KR20070053767A - Removal of carbon dioxide from air - Google Patents

Abstract

The present invention relates to a method for removing carbon dioxide from air, the method according to the invention comprising exposing a solvent-covered surface with a thin layer or an air stream in which the air stream is maintained near the thin layer. The present invention also provides a device which is a thin layer scrubber comprising a surface covered with a solvent installed to be exposed to an air stream. According to another feature of the invention, there is provided a method and apparatus for separating carbon dioxide (CO ₂ ) bound to the solvent. The invention is particularly useful for the treatment of hydroxides comprising carbon dioxide obtained from air.

CO2, hydroxide, sodium bicarbonate, scrubber

Description

REMOVAL OF CARBON DIOXIDE FROM AIR

One feature according to the invention relates to the removal of selected gases from air. In particular, the present invention has utility in the extraction of carbon dioxide (CO ₂ ) from air, and will be described primarily in connection with such utility, although other utilities may be considered.

Removing carbon dioxide (CO ₂ ) from the ambient air makes it possible to use carbon-based fuels and subsequently treat associated greenhouse gas emissions. While carbon dioxide is neither toxic nor harmful in parts per million (ppm) quantities, carbon dioxide causes environmental problems just because it accumulates in the air, so that air can be replenished at different places and at different times to compensate for air emissions. It is possible to remove carbon dioxide from it. The overall manner of capturing air is known.

The production of carbon dioxide arises from various industrial applications, such as the development of power plants from coal, and the use of hydrocarbons, which are typical principal components of fuels burned in combustion devices such as engines. Exhaust gases from the combustion unit are simply released into the atmosphere Contains gas. However, as it relates to rising greenhouse gases, emissions of carbon dioxide from all sources will have to be reduced. The best choice for a mobile source would be the direct collection of carbon dioxide from air rather than the collection of carbon dioxide from mobile combustion devices in automobiles or airplanes. The advantage of removing carbon dioxide from air is that it eliminates the need to store carbon dioxide in mobile devices.

Various methods and apparatus have been developed for removing carbon dioxide from air. In one of these cases, the air is washed with an alkaline solvent in a tank filled with what is called Raschig rings. For the removal of small amounts of carbon dioxide, gel absorbers have also been used. Although these methods are effective for the removal of carbon dioxide, there is a serious disadvantage in that a relatively high pressure loss occurs during the washing process, in which air must be propelled by the absorbent at a considerably high pressure in order to remove the carbon dioxide efficiently. Moreover, in order to obtain increased pressure, several means of compression means are required, which consume a certain amount of energy. Since the energy required to increase the air pressure will produce its own carbon dioxide to be obtained or treated, the additional energy used to compress the air can have a particularly detrimental effect with respect to the overall carbon dioxide balance of the process.

Therefore, because these processes heat or cool the air, or change the pressure of the air by a significant amount, that is, the clean process introduces carbon dioxide into the atmosphere as a byproduct of the generation of electricity used to power the process. As the net loss in carbon dioxide is insignificant, the prior art method results in an inefficient acquisition of carbon dioxide from air.

Moreover, while there is already a scrubber design for separating carbon dioxide from the air, this design is typically a bed type of package type with the goal of removing all small amounts of impurities from other gases. Limited to implementation. One such device described in US Pat. No. 4,047,894 is a carbon foam assembled spaced apart from each other in a porous sintered plate or housing made of polyvinyl chloride (PVC). It includes an absorbent element comprising a. Before the plate is assembled in the housing, potassium hydroxide is injected into the porous plate. Such devices have the disadvantage that the absorbent material used to separate carbon dioxide from the air cannot be filled without disassembly of the device housing.

In another aspect, the present invention generally relates to a method and apparatus for separating carbon dioxide (CO ₂ ) bound to a solvent. The present invention is particularly useful in the context of treating hydroxide solvents (or other alkali absorbers used to collect carbon dioxide), including carbon dioxide obtained from air, and although other utilities are contemplated, Will be.

The process of collecting carbon dioxide from air typically depends on a solvent that binds carbon dioxide physically or chemically from the air. Real carbon dioxide Classes of solvents include strong alkali hydroxide solutions such as, for example, sodium hydroxide and potassium hydroxide. For example, hydroxide solutions that exceed 0.1 molarity, such as carbonates, can readily remove carbon dioxide from the air to which carbon dioxide is bound. Higher hydroxide concentrations are preferred, and an effective air contractor will use more than 1 mole of hydroxide solution. Sodium hydroxide is a particularly convenient choice, but other solvents can be used, such as organic amines. Nonetheless, other choices of absorbents include weaker alkaline saline such as sodium carbonate or potassium carbonate brines. The disclosure below applies to all solvents storing carbon dioxide at least partially in the form of ionic carbonates or bicarbonates.

The design of air constrictors aimed at constricting air for carbon dioxide is dealt with in other patents and in literature [1, 2, 3]. This feature of the invention relates to the recovery of the absorbent, wherein carbon dioxide The laden sorbent is recovered and carbon dioxide is separated from the solution. The present invention discloses a series of electrochemical processes that can be combined with an air capture unit to replenish and separate a hydroxide solution and in some cases collect carbon dioxide in a pressurized stream.

All processes have commonalities in that sodium hydroxide is separated from carbonates or other salts by electrochemical means. There are several electrolytic processes involving only a pair of electrodes, but most processes use bipolar membranes and / or at least one type of cationic or anionic membrane. Include a separation plan. In addition, some processes involve known calcination and / or acid base reactions leading to the release of carbon dioxide in the gaseous state. Several such processes are grouped into classes with seven features as claimed in the present invention and described below.

Accordingly, it is an object of the present invention to improve and streamline the process design for the acquisition of carbon dioxide from air, which is an important tool that allows the use of hydrocarbons in a carbon-limited world. Many such processes may also be found useful in other applications where carbon dioxide bound in the hydroxide solvent must be completely or partially removed from the solvent.

Disadvantages in this field have been described and overcome by the carbon dioxide separation membrane and method of use thereof encompassed by the present invention.

The purpose of separating carbon dioxide from air is to balance the carbon dioxide emissions from, for example, the operation of a vehicle or a power plant. While the most obvious source of release of carbon dioxide that can be cured by the present invention may be difficult or impossible to obtain carbon dioxide at the time of release, the present invention is not limited to such a source but complements any other source as well. Can be. If at some point in the future it is considered that the amount of anthropogenic carbon dioxide in the air is too high, this approach of carbon dioxide mitigation can actually be used to lower the concentration of carbon dioxide in the atmosphere.

It is an object of the present invention to obtain carbon dioxide from the air for the purpose of controlling the overall carbon dioxide supply of the atmosphere, but this concept is equally applicable even if the reason for obtaining carbon dioxide from a gas having a low concentration of carbon dioxide is different. . Exemplary embodiments may occur for the purpose of the sale of carbon dioxide in the food industry or the oil industry, may occur in indoor air, tunnels or other enclosed environments, and include the acquisition of carbon dioxide or other acid gases from a dilute stream. do.

In one aspect, the present invention relates to an air scrubber apparatus, a method for recovering carbon dioxide from a solvent used in the scrubber, a commercial method utilizing the apparatus, and a method for removing carbon dioxide. The air scrubber according to the present invention is effective at removing a large portion of carbon dioxide from the air flowing through the air scrubber and operating at the minimum air pressure drop. In the case of the present invention, a scrubber design of a lamella design is described for reasons that will become clear below. An air scrubber unit based on a lamella design can be a module within a large superstructure for funneling air into the air, which can be modified to suit a particular design. The air can be propelled by natural wind, thermal convection or a fan.

In another aspect of the present invention, a method and apparatus for recovering carbon dioxide obtained in a scrubber are proposed. In almost all air acquisition designs, the overall process of obtaining carbon dioxide from air requires an air shrinker that removes carbon dioxide from the air by incorporating carbon dioxide into the solvent or absorbent. The absorbent consumed is then preferably treated to recover all or part of the carbon dioxide in the concentrated, pressurized stream. The recovered solvent is recycled to the carbon dioxide collector.

The present invention designs several processes for recovering hydroxide based absorbents by electrochemical process means capable of separating acids from bases. Such processes exist and are exemplified for various acids. These processes are taken herein and combine such processes in such a way to make a functional and effective carbon dioxide recovery unit.

The invention also relates to the design of several new unit fixings that are specifically applied to the applications contemplated herein.

There are several advantages of this invention: Firstly, the process avoids the intermediate step of converting carbonate ions into calcium carbonate that is then calcined to free carbon dioxide, thereby avoiding the overall flow sheet of carbon dioxide acquisition from air. make the sheet reasonably reasonable. Mass handling of such conversion processes is complex. Second, more direct electrochemical processes also provide a way to reduce the overall energy consumption. Third, it significantly reduces the need for a complex, mobile device for handling solid material streams such as may be required in conventional calcium carbonate propulsion recovery units.

Finally, it is noted that implementations of this type in the present invention can also be used in systems that need to separate carbonate and hydroxide solutions resulting from processes other than air extraction.

Additional features and advantages of the invention will be apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings, in which like reference characters designate the same devices.

1 shows a perspective view of an air cleaner unit made in accordance with a preferred embodiment of the present invention.

FIG. 2 shows a plan view of the air cleaner unit of FIG. 1.

3 shows a front view of the air inlet of the air cleaner unit of FIG.

4 shows a side elevation view of the air cleaner unit of FIG. 1.

5 shows a schematic diagram of an apparatus for separating carbonate and hydroxide solutions according to another feature of the invention.

6-13 illustrate various processing flow diagrams and processing systems for separating carbonate and hydroxide solutions in accordance with the present invention.

1 to 4, an air scrubber unit in accordance with one aspect of the present invention removes carbon dioxide from an air stream maintained by a low pressure-tilt. The air scrubber unit consists of a wind collector 10 and a liquid sump 12 having two sheets covered with a downward flowing sorbent that combines a thin air space, as well as a lamella in the plate 5. . Although the lamellas can be supported spaced by other means, the two sheets forming the lamellas are preferably strapped between the sheets in the thru-rods supported by the rigid frame 1. Separated by a spacer 4 which is bonded.

In general, the absorbent material flows down the lamellae sheet, while the air flow passes between the thin air spaces between the sheets. The contact of air with absorbent materials generates a chemical reaction that removes carbon dioxide. However, the air scrubber unit can also obtain other gases present in the air.

The absorbent is applied to the lamella sheet, for example from a corrugated tubing 3 supplied from the header 6, according to established conditions in this field approach, for example spray nozzles or liquid jets. The design can also wet the vertical surface near the top and allow fluid to flow over the surface until gravity covers the entire area. Alternatively, the surface may be shaped like a flat disk that gets wet during the rotation through the catchment. Movement can disrupt the liquid flowing along this surface.

Typical pressure gradients for moving the air flow across the lamellas are those that can be formed by natural air flow such as, for example, wind or heat gradients. The pressure drop across the unit ranges from almost zero to hundreds of Pascals, with a preferred range of 1 to 30 Pascals and an optimal range of 3 to 20 Pascals. However, a piped or pipeless fan can also be used to move the air flow to induce air and convection.

Lamellae Lamella )

The purpose of the wind collector is to ensure that the air flow is in intimate contact with the scrubber or surface covered with the absorber of the wind collector. The basic unit of the wind collector is a single lamella that becomes a thin air space joined by two sheets covered with absorbent. In the simplest design, the sheet is flat, but it is possible that the sheets are curved long enough that the air passing over the sheet can move in a straight line, ie the sheet is curved in a direction perpendicular to the wind flow. . Each air cleaner includes means for disturbing the absorbent on the sheet of lamellae and re-acquiring the absorbent material consumed.

Presented below is a list of exemplary embodiments for the wind chamber lamellae:

1) Flat rectangular sheets or plates aligned parallel to each other.

2) corrugated sheets having planes that are straight in the direction of air flow and aligned parallel to each other.

3) A flat disc that rotates around its central axis with air flowing at right angles to the axis of rotation. The absorbent may be applied by a wheel dipping into the fluid near the bottom of the rotary motion. A standing absorbent can only cover the outer rim of the disk or can reach all directions about the axis. Alternatively, the absorbent may be injected into the rim by the liquid flowing around the disc due to gravity and rotational movements that wet the axis.

4) Concentric tubes or similar shapes in which air can be injected along the tube axis. Such tubes are vertical for contrast-flow designs with wetting initiated at the upper rim or with nearly horizontal absorbents entering at one end and at one point and disturbing through the slow rotational movement of the tube. Can be arranged.

The air flow across the lamellae may be a natural wind flow or may be obtained, for example, by other means passing through the treated heat rise airflow. High wind speeds, however, can lead to back-productivity as larger speeds reach greater proportions of energy dissipation. Slow airflow rates maximize the contact time with the absorbent on the lamella, while minimizing the loss of kinetic energy in the system. Due to this, the air flow rate through the scrubber unit can range from a substantially stationary state to several tens of meters per second. The preferred range is 0.5 to 15 m / s and the optimum range for wind propulsion systems is 1 to 6 m / s.

In practice, the flow rate of air flow through the wind collector needs to be a substantial part of the typical wind speed. The choice of better geometry will somewhat reduce the flow rate, but this improvement will be a factor rather than two orders of magnitude.

In an exemplary embodiment of the present invention, an air flow speed of 2 m / s is assumed, but the air flow speed may range from 0.5 m / s to about 4 m / s. At a normal flow rate of 2 m / s, the flux of carbon dioxide per unit air region is 30 mmol / m 3 / s. The flow in sodium hydroxide is limited to about 0.06 mmol / m 2 / s of the hydroxide surface and is superior for boundary layer thicknesses where the air side transport coefficient exceeds about 2 to 4 mm.

In this embodiment, the acquisition system is as compact as possible, and the size limiting element determines the geometry of the device. Positioning the flat absorbent sheet about 0.5 cm apart provides a sheet surface area of about 500 m 2 within cubic meters. The substantial length is about 1.2 m in addition to the allowance for the limited thickness of the sheet. If the sheet is folded or made in the form of a tube it is possible to obtain a slightly larger sheet surface. However, because the liquid absorbent flows from the top of the wind collector to the bottom, the sheet with breaks or folds adds disturbances to the system, deforming the air flow and reducing the boundary layer thickness, thus providing a flat vertical sheet. Is a natural choice. Since flat plates already operate at the optimal boundary layer thickness, such disturbances do not improve carbon dioxide absorption performance, but disturbances will increase the energy dissipated within the device.

However, for structural reasons very large systems with wind collector designs with depths greater than 1 meter are likewise considered. Such a device is still optimal for a sheet surface of 500 m 2 per square meter of the front entrance. In this embodiment, the natural spacing between the plates does not exceed the optimal boundary layer thickness, which may require the introduction of a shape that causes disturbance. Disturbance causes the boundary layer thickness to return to the desired value of 2-4 mm. For example, a 20 m depth filter system would require about 25 m 2 of packaging per cubic meter. The typical separation distance for the sheets would be about 8 cm and would be too large for the optimal boundary layer. Generating centimeter-scale eddies will effectively reduce the boundary layer thickness and thereby provide the necessary air side carbon dioxide flux.

Flow through the 1 m depth unit 0.6 cm away from the sheet or plate will raise the laminar to a relatively high flow rate. If the Reynolds number is

Re = (ρdv) / η (1)

If defined as thin layer area is in the range of about 1400. In other words, for plates located 0.6 cm apart, the flow is maintained in a thin layer (lamina) of up to about 4 m / s. In the following, the resistance to air flow in the stack of plates is thus calculated.

The pressure drop per unit length is given by:

∂P / ∂x (2)

If the pressure across the plane perpendicular to the two sidewalls is constant, the force acting on the air parcel of width Δy, height h, and depth Δx is given by the following equation:

Δyh (∂P / ∂x) △ x = -η {(∂ ² v / ∂y ² ) △ y} h △ x (3)

or

(∂ ² v / ∂y ² ) = -1 / η (∂P / ∂x) (4)

or

v (y) = (1 / 2η) (∂P / ∂x) y ² + C ₁ y + C _{2 .} (5)

The two integration constants follow two boundary conditions.

That is, v (0) = v (d) = 0. (6)

From the above,

v (y) = (1 / 2η) (∂P / ∂x) y (d-y). (7)

Therefore, the peak velocity between the plates is:

v _max = (d ² / 8η) (ΔP / L). (8)

Where L is the length of the plate and P is the pressure drop between the plate lengths. The average flow rate is given by:

이다.Or less, v (average)

to be.

v (average) = (1 / d) (∫v (y) dy) = (d ² / 12η) (△ P / L) (∫ is the static fraction from 0 to d) (9)

or

ΔP = (12ηL) / (d ² ) v (average) (10)

or

L = (ΔPd ² ) / (12ηv (average)). (11)

If L needs to be determined,

(ρv (average) ² ) / 2 = ΔP (12)

Since L = (ρv (average) d ² ) / (24η) = (Re / 24) d (13), v = 2 m / s and L = 0.2 m.

More generally, the design rule is

d / L ~ (24 / Re) (14)

Where Re is the Reynolds number of the flow.

The flow between the plates is affected by the distance variation between the plates. The mass flow per unit length of the system is given by:

Q = ρv (average) d = ρ (d ³ / 12η) (∂P / ∂x) (15)

If Q is a constant and d is a function of x, it is given by:

ΔP = (12ηQ / ρ) {∫dx / d (x) ³ (∫ is static from 0 to L) (16)

In the simple case, the width is d ₁ in one half of the lamellae and d ₂ in the other half. If we assume

d ₁ + d ₂ = 2d and (d ₂ / d ₁ ) = α or d ₁ = (2d) / (1 + α) and d ₂ = (2d) / (1 + 1 / α) (17)

According to Equation 17, the following values are obtained:

^{△ P = (12ηL / ρd 3} ) (d 3/2) (1 / d 1 3 + 1 / d ₂ ³ ) = (12ηL / ρd ³ ) {(1 + α) ³ + (1 + 1 / α) ³ } / 16 (18).

The correction factor for α = 1 becomes 1, but the correction factor for α = 2 increases to 1.89. For a sufficient three-dimensional system where air can flow around a narrow point, the overall limit is substantially smaller.

It should be noted that the equations derived above apply only to the flow of thin layers developed entirely between the plates. However, there is a starting point of the plate where the flow is not sufficiently developed. In such areas the pressure drop is best characterized by dragging onto a separate plate. As the boundary layer thickness increases and boundary layers begin to overlap from adjacent plates, the flow develops into the normal flow pattern observed between the two plates.

The drag per unit width on one side of an infinitely thin plate is given by:

F _drag = C _d (ρ / 2) xv ² (19)

Where x is the distance from the start of the plate.

The drag coefficient C _d is given according to the literature as follows:

C _d = 1.308Re _x ^-1/2 = 1.308η ^1/2 ρ ^-1/2 v ^-1/2 x ^-1/2 (20)

The pressure drop between a series of parallel plates short enough to not interfere with each other is given by:

P (0)-P (x) = C _d (ρ / 2) xv ² (1 / d) (21)

Where d is the infinitely thin gap between the plates, or the pressure is given by:

P (0) - P (x ) = 1.308η 1/2 ρ 1/2 v 3/2 x 1/2 d -1 (22)

At the starting point, the airflow looks different as the boundary layers affected by the starting point get smaller.

In addition, in one particular design, it may have an ambient wind speed v ₀ . In front of the lamellae, the air stagnates and slows down at the speed v. The pressure to propel the air through the lamellae is given by:

(ρ / 2) (v ₀ ² -v ² ) = (12ηLv) / d ² (23)

or

(ρ / 2) v ² + {(12ηL) / d ² } v-(ρ / 2) v ₀ ² = 0 (24)

v = (v ₀ ² + (12nL / ρd ² ) ² } ¹ / ^2- (12ηL / ρd ² ) (25)

Of the two solutions to the root equation, choose only the physical solution, that is, the value is positive.

Absorbent

The absorption rate of carbon dioxide into the strong hydroxide solution has been actively studied. Exemplary air scrubbers are devices that pull carbon dioxide or other gas directly from natural wind flows or from flows that follow similar propulsion such as, for example, thermally induced convection.

Absorption of carbon dioxide into a strong hydroxide solution involves a chemical reaction that greatly accelerates the dissolution process. The pure reaction is as follows:

CO _{2 ^{(dissolved) + 2OH - -> CO 3}} - + H 2 O (26)

There are several clear ways in which this reaction occurs. The two steps associated with high pH are:

CO _{2 ^{(dissolved) + OH - -> HCO 3}} - (27)

The following reaction is followed by this reaction:

_{^{HCO 3 - + OH - ->}} CO 3 - + H 2 O (28)

The latter reaction is known to proceed very quickly; On the other hand, the initial reaction is relatively slow. The reaction kinetics for the reaction (2) is expressed as:

_{(d / dt) [CO 2} ] = κ [OH -] [CO 2] (29)

Therefore, the time constant describing the reaction kinetics is expressed as:

τ = 1 / (κ [OH -]) (30)

The rate constant κ is measured at 20 ° C. and infinitely dilute, with the following values:

κ = 5000 liter mol ^-1 s ^-1 = 5 m ³ mol ^-1 s ^-1 (31)

Ionic strength correction is given by:

κ = κ _∞ 10 ^{0.13 A} (32)

At high concentrations of carbon dioxide in the gas, the rate of reaction (2) limits the rate of absorption, although the time constant for the 1 molar solution at 0.14 ms is quite small.

Standard model that combines gas-side flow coefficients and liquid-side conversion coefficients to describe pure flow through cross-interfaces according to standard chemical engineering models such as Danwert or Astarita, for example. The conversion process in which the gas component is dissolved or chemically absorbed in the absorbent may be described. The total flow is given by:

F = κ _G (ρ (x = -∞)-ρ (x = 0)) = κ _L (ρ '(x = 0)-ρ' (x = ∞)) (33)

Ρ and ρ 'are the molar concentrations of carbon dioxide in the gas and in the solution, respectively. The parameter x represents the distance from the mutual boundary. The distance inside the gas is calculated as a negative value. By applying Henry's law at the boundary,

ρ '(0) = K _H ρ (0) (34)

Becomes

Expressed as a dimensionless factor, K _H = 0.7 [Hensity constants are generally dimensioned because the concentration is measured at partial pressure on the gas side. That is, it is expressed in pascal units or atmospheric pressure units (atm). The liquid side concentration, on the other hand, is usually measured in moles per liter. Because of this, typical units are liter / mol / atm.

For the gas side, the conversion constant can be calculated by the following equation:

κ _G = (D _G / Λ) (35)

Where Λ is the thickness of the sublayer of the thin layer forming the surface of the mutual interface. The thickness of this layer will depend on the geometry of the flow and the disturbance of the gas flow. Given that the geometry of the flow and the disturbances are given within the gas flow, the optimal choice for Λ should be determined.

For fluid packages, the standard approach to calculating the conversion factor is to assume the residence time τ _D for parcel at the surface of the fluid. This time arises from the flow characteristics of the absorbent, which includes surface generation and disappearance as well as disturbing liquid mixing in the vicinity of the surface.

λ = (Dτ _D ) ^1/2 (36)

At time τ _D , diffusion can mix dissolved carbon dioxide into the thickness of the layer, so the flow from the surface is given by:

F = D _L (∂ρ '/ ∂x) (37)

D _L is the diffusion constant of carbon dioxide and ρ 'is the concentration of carbon dioxide on the liquid side. The slope is calculated at the surface. The conversion coefficient of the liquid is defined from the equation:

F = κ _L (ρ '(x = 0)-ρ' (x = ∞)) (38)

If we approximate the slope with the equation

∂ρ / ∂x = (ρ '(0)-ρ' (∞)) / λ (39)

For the diffusion propulsion absorption process the following equations are derived:

κ _L = (D _L / λ) = (D _L / τ _D ) ^1/2 (40)

Where D _L is the diffusion rate of carbon dioxide in the absorbent.

In the presence of a fast chemical reaction with a reaction time τ _R << τ _D , the layer that absorbs carbon dioxide is characterized by this faster time, so that the conversion factor is given by the following equation:

κ _L = (D _L / τ _R ) ^1/2 (41)

If a chemical reaction is present, this causes the conversion factor to increase by the following factors:

(τ _D / τ _R ) ^1/2 (42)

However, this improvement can only be maintained if the supply of reactants in the absorbent is not limited. In the case of carbon dioxide, which neutralizes the hydroxide solution, it is possible to deplete the hydroxide in the boundary layer. The layer thickness is λ ρ _OH ^- including the area density of the hydroxide ions in the λ and exhaust velocity (rate of depletion) is a 2κ _L ρ'CO _2. For this reason, the following equation applies for the fast response limit (Equation 41):

(ρ _OH- / 2ρ ' _CO2 ) (τ _R / τ _D ) << 1 (43)

In the case of the present invention,

ρ _OH -τ _R = 1 / κ (44)

to be.

Because of this, the condition can again be expressed as:

2ρ ' _CO2 κτ _D >> 1 (45)

The critical time for transition from fast reaction kinematics to instantaneous reaction kinetics is about 10 seconds for atmospheric air. The transition is not dependent on the hydroxide concentration in the solution. However, once the transition has taken place, the rate of absorption is limited by the rate at which hydroxide ions move to the surface. Therefore, lower than the fast limit, the carbon dioxide flux is given by:

F = (1/2) (D _OH- / τ _D ) ^1/2 ρ _OH- (46)

The flow in the instantaneous region is independent of the carbon dioxide concentration in the boundary layer.

The flow is characterized by an effect transformation factor that can be expressed as:

F = κ _eff (ρ _{CO2 - ρ 'CO2 / K H)} (47)

Under these conditions, the molar concentration is asymmetric in distant gases and distant liquids. In the case of a hydroxide solution, the concentration of the distant liquid is zero. therefore,

F = κ _eff ρ _CO2 (48)

ego,

κ _eff = {1 / κ _G + 1 / (κ _L K _H )} ^-1 (49)

to be.

The optimum design is close to the boundary between the gas side restriction and the liquid side restriction. Therefore, for the present invention the design value for the air side boundary thickness is established in the following equation:

Λ ≒ D _G / (D _L / τ _R ) ^1/2 (50)

This condition is about 4 mm for air based extraction of carbon dioxide.

All of these conditions greatly limit the practical design. For a 1 molar solution, the total solution flow is measured to be 6 × 10 ⁻⁵ mol m ⁻² s ⁻¹ , which results in an effective value of 0.4 cm / s close to the theoretical value.

In the form of absorbers that absorb carbon dioxide, there are a wide variety of choices available. In one embodiment, an aqueous hydroxide solution is used as the absorbent material. This tends to be a strong hydroxide solution that rises to the maximum possible level (about 20 moles) above 0.1 mole.

The hydroxide used as the absorbent may be various cations. Sodium hydroxide and potassium hydroxide are most obvious, but other absorbents, including organic absorbents such as MEA, DEA, have practical potential. In addition, the hydroxide does not need to be purified and may comprise a mixture of other materials added to change or modify the various properties of the absorbent. For example, additives can enhance the reaction kinetics of hydroxides with carbon dioxide from air. Such catalysts can be surfactants or molecules dissolved in a liquid. The addition of organic compounds such as MEA is just one embodiment. Another additive serves to reduce the loss of water by making the solution more hygroscopic. Still other additives may be used to improve the flow or hygroscopic properties of the fluid or to help protect the surface from the corrosive effects of the hydroxide solution. In addition, any absorbent used in the present invention should make the surface of the lamellar sheet moist. Various means are known in the art for this purpose. Such means include surface treatment, surfactants in the absorbent, and other means that increase hydrophilicity in the absorbent or other means.

The present invention includes the following important design features:

1) The lamellar sheets become substantially smooth in the direction of the air flow on a size scale consistent with the size sheet separation (but a much finer sized incidental structure can be used to improve the carbon dioxide transport coefficient). Such variations are relatively insignificant unless variations that are orthogonal to the air flow prevent effective wetting of the plate, sheet or surface.

2) The sheets are secured sufficiently firmly or firmly so that their bending or flapping does not significantly reduce the pressure variation between the lamellas.

3) The air flow through the inlet at the surface is restricted so as not to significantly affect the pressure variation between the lamellas.

4) The spacing between lamellae is chosen such that the system does not transform out of the lamellae flow or at least deviate from the region.

5) The depth of the membrane unit is kept short enough to prevent almost complete exhaustion of air in the front part of the unit.

6) It is appropriate that the lamellas are vertically aligned for the use of both sides of the seat. However, deviations from such a design can be considered for other flow optimizations.

7) The height of the lamellae is chosen to maximize the wetting properties of the surface and minimize the need to regenerate fluid multiple times.

Dry block of carbon dioxide recovery system building blocks )

In another aspect of the invention, the following electrochemical process may be used in the carbon dioxide acquisition system disclosed in the present invention, or in any other apparatus for collecting carbon dioxide. These electrochemical processes are all based on separating the salts into their acids and bases, where the acids and bases are held in solution by electrodialysis using bipolar membranes. Examples include the formation of hydrochloric acid from sodium hydroxide and sodium chloride and the formation of acetic acid from sodium hydroxide and sodium acetate. Other combinations of acids and bases are also presented in the literature, patent literature and industrial sites. In the context of the present invention, units of this type as well as units for separating salts of weak acids into the corresponding acids and bases can be used to separate the hydroxide and sodium carbonate solutions.

In the following, a number of treatment steps are described which become the basic drying blocks of the treatment process considered in the present invention.

1.Isolate a mixture of hydroxide and sodium carbonate electrochemically into sodium hydroxide and sodium carbonate. For this processing step the invention can use specially designed units which rely on existing dry blocks or which use electro-dialysis for separation. This technique can also be extended to include cations of sodium and other cations such as potassium, ammonia, and organic amines such as monoethanolamine (MEA), diethanolamine (DEA) as non-limiting examples. In all cases the basic reaction is to separate the mixture of R-OH and R ₂ CO ₃ into a separate solution of R-OH and RHCO ₃ via a membrane process.

2. Electrochemical separation of metal bicarbonate into metal carbonate and carbon dioxide. This process preferably uses electrodialysis comprising a bipolar membrane, but other electrolytic processes are disclosed and can be used in the literature.

3. Separating the metal bicarbonate into metal hydroxides and carbon dioxide. Again this process is preferably dependent on electrodialysis with a bipolar membrane, but can also be achieved by electrolysis of the metal bicarbonate producing hydrogen reused within the hydrogen electrode producing carbon dioxide.

4. A unit that combines two or more of the drying blocks (2 and 3 or 4) into a single unit. For example, the process of making a mixture of carbonates and hydroxides into hydroxide and carbon dioxide gas in any way.

The following are additional drying blocks that do not contain electrochemistry:

1. A membrane process using a concentration gradient to separate cations such as sodium from a solvent or to remove hydroxides from an incoming solvent. In some cases these units can partially transform the solvent from carbonate to bicarbonate.

2. A temperature swing process for the separation of sodium carbonate from a mixture of sodium carbonate and sodium hydroxide using precipitation.

3. Process of making bicarbonate solution to carbonate solution by heat or pressure fluctuations. This process is developed in accordance with methods known in any carbon dioxide-cleaning system operating at a sufficiently high carbon dioxide pressure for the reaction between sodium carbonate or potassium carbonate and carbon dioxide to form bicarbonate.

4. A process that takes a bicarbonate solution and uses evaporation or thermal fluctuations to precipitate the bicarbonate from the solution.

5. Process for calcining bicarbonate with carbonate. Of particular interest in this process are sodium bicarbonate and potassium bicarbonate.

6. A process for mixing an acid with a hydroxide-carbonate mixture to neutralize the mixture and to form a solid precipitate of these salts. The process can be stopped either in pure carbonate or in moving to form a carbonate / bicarbonate mixture or in moving all pathways leading to bicarbonate.

7. A process using an acid to extract all carbon dioxide from a bicarbonate, or carbonate or hydroxide mixture. This process can be performed at elevated pressure to deliver carbon dioxide at pipeline pressure.

Overview of the overall process plan

All processes begin the extraction of carbon dioxide from air in units that are no longer specifically described herein. Specific implementations are addressed in other aspects of the invention, and the details of these units are not of interest at this point. Rather, it should be noted that these units consume hydroxide based solvents which are not completely or partially converted to carbonates. It will be possible to partially convert the solvent to bicarbonate. In the latter case, the use of carbonate as the starting solvent may also be considered. The feed solvent may contain only hydroxides and other compounds. For example, the solvent may include any additives that improve process performance, but may in particular include residual carbonates generated from the preceding process cycle.

The object of this area of the present invention is to outline the processes and methods for recycling partial or complete recovery of solvent and carbon dioxide into a stream, preferably concentrated at a pressure suitable for subsequent processing steps. For clarity, specific hydroxides and specific acids will be described in the description below. However, it is emphasized that the process is not limited to this particular compound and can be generalized to include other ionic materials.

In the examples below the air constrictor unit uses a sodium hydroxide solution having a concentration in excess of 1 mole per liter of sodium hydroxide. Some residual carbonate may still be present in the solvent from the previous process cycle, but since the solvent is exposed to air, the hydroxide is converted to carbonate and the concentration of the carbonate in the solvent begins to increase until no conversion is required. There are several reasons for the absorption process to stop. In particular, the process may be stopped due to exhaustion of hydroxide or carbonate concentration reaching saturation. For most acquisition designs, precipitation of carbonates in the absorbent will be undesirable. The resulting carbonate solution is then returned back to the acquisition unit for further processing. Conceptually, three steps can be considered in the recovery process:

1. Separation of unconverted hydroxide from carbonates;

2. decomposition of sodium carbonate into sodium hydroxide and sodium bicarbonate (acid base decomposition); And

3. Decompose sodium bicarbonate into sodium hydroxide or sodium carbonate and carbonic acid.

In some implementations, these steps can be combined into two process steps or even a single process step. Alternatively, each of these steps can be carried out by neutralizing the base (in this case sodium) with a weak acid. If the sodium salt of the acid precipitates, in this case it is simple to separate the acid anions in the precipitated form from the liquid, so the process can be stopped at any point; Otherwise, the neutralization process must be complete, resulting in a salt of gaseous carbon dioxide and base. If the air acquisition uses sodium hydroxide and the acid is acetic acid, the result will be sodium acetate. The resulting sodium acetate will be separated from sodium hydroxide and acetic acid. Sodium hydroxide and acetic acid are recycled. Decomposition of sodium acetate is optimally performed using an electrodialysis unit comprising a bipolar membrane. If high pressure carbon dioxide is required, an acid stronger than acetic acid is needed.

Process 1:

5 to 7, Process 1 divides the improvement of the solvent into three distinct steps. The process first separates most of the carbonate from the brine. The process then uses an electrochemical step that effectively removes sodium ions from the brine to reach sodium hydroxide and sodium bicarbonate. Finally, the resulting sodium bicarbonate releases carbon dioxide by the addition of an acid that is recycled back to the electrochemical step. The advantage of this process run is that this process combines high energy efficiency with the ability to produce pressurized carbon dioxide. The delivery of carbon dioxide at elevated pressures is an advantage of electrochemical separation.

Step 1.1

Sodium carbonate is extracted from the solvent consumed by the temperature fluctuations. The solubility of sodium carbonate is much lower than the solubility of sodium hydroxide (similar logic applies to other hydroxides, but this practice is limited to compounds with matching solubility ranges). As a result, the maximum amount of sodium carbonate that can be converted to sodium carbonate by carbon dioxide absorption for the concentrated hydroxide solution is limited. One advantage of operating at high sodium hydroxide concentrations is that the solvent consumed is controlled by sodium hydroxide which still must not be treated by a number of expensive steps. The temperature swing method solves this problem because it allows the separation of carbonates without having all sodium hydroxide pass through the membrane system. If the spent solution is nearly saturated with sodium carbonate, a portion of the sodium carbonate can be extracted through precipitation. Solubility of sodium carbonate varies more than three times between 0 and 25 ° C. This makes it possible to regenerate the sodium carbonate solution through temperature fluctuations using heat exchange between the incoming and outgoing fluids. This approach can utilize ambient heat in warm, dry climates with large maximum temperature fluctuations. The regenerated hydroxide solution is returned to the air constrictor unit. This approach is also more advantageously employed in dry climates, which will help to reduce the water loss accompanied by high sodium hydroxide concentrations.

Step 1.2

Sodium carbonate precipitate is dissolved in water at maximum concentration. Sodium carbonate is further processed in an electrochemical unit for acid / base separation where sodium carbonate can be separated into sodium hydroxide (base) and sodium bicarbonate (acid). There are a number of different designs for this electrochemical separation. Some are known and are common separators for acids and bases using bipolar membranes. Other designs include hydrogen electrodes. The following describes a specific device specifically designed for the decomposition of sodium carbonate.

Step 1.3

The bicarbonate solution resulting from step 1.2 is injected into a pressure vessel which is mixed with the weak acid. Suitable acids include citric acid, formic acid and acetic acid. However, the present invention is not limited to any particular acid. The acid-base reaction removes carbonic acid from the salt. Carbonic acid is then broken down into carbon dioxide and water. First, the carbon dioxide breaks down into the brine but soon reaches a pressure above the vessel pressure, resulting in the release of a pressurized carbon dioxide stream. The design limitations for these units lead to some limitations on the choice of acid. Most importantly, the acid needs to be strong enough to remove carbon dioxide from the solution even at design pressure. Further description of these units is given below. The advantage of such a system is that it allows the release of concentrated carbon dioxide at pipeline pressure without having to place a large electrochemical unit into the pressure vessel. The brine of the salt of the weak acid is left. It may be a salt of sodium acetate, sodium citrate and any other weak acid.

Step 1.4

Salts of weak acids and bases used in the acquisition are decomposed in an electrodialysis unit using cation, anion and bipolar membranes to recover sodium hydroxide and weak acids. There are several variations of these units that can be used. As a result of step 1.4, carbon dioxide is recovered and the remaining sodium hydroxide is returned to the full cycle. It is generally advantageous to use a unit that removes sodium ions from the solution rather than removing the anions from the solution because it is generally undesirable to send residual anions to the air constrictor when taking various design options. This also makes it possible to control the concentration of sodium hydroxide saline. Depending on the detailed conditions of the implementation, this last unit can be used to adjust the water content of sodium hydroxide to meet what is required in the air constrictor. While the present disclosure describes weak acids as a whole, the electrodialysis process uses less energy than when recovering weak acids, so the process according to the basic principle works on strong acids as well. In some special cases, strong acids may have other advantages overcoming the inherent higher electrochemical potential. For example, some membranes can maintain more current on simple ions of strong acids and more organic acids at the same time.

Process 2:

Referring to FIG. 8, process 2 is similar to process 1 but replaces the first step with a membrane separation system. This process will produce a solution of sodium hydroxide that is relatively dilute and needs to be concentrated. It can then be used as starting brine on the hydroxide side of the membrane. If the air extraction step leads to evaporative water loss from the solvent and in any case additional water needs to be added to the solvent, process 2 works particularly satisfactorily.

Step 2.1

A periodic system of cells is used with dilute NaOH solution in place of the concentrated NaOH / Na ₂ CO ₃ brine. On one side the cells are separated by a cationic membrane and on the other side by a bipolar membrane. The last cell is connected to the first cell, making the system periodic. The design can be reduced to a simple pair of cells, but geometrical constraints are beneficial for multiple cell systems as a whole. As sodium diffuses through the cationic membrane, the charge neutrality of the cell requires the bipolar membrane to provide H ⁺ -OH ^- pairs. H ⁺ neutralizes the OH ⁻ left behind; OH ⁻ forms the base with sodium removed in another chamber. In the first approach, the concentration of sodium in the two chambers is out of balance, suggesting that this separation can be performed without power if at least half of the NaOH in the spent solvent is converted to sodium carbonate. If this is not the case, it is still possible to use such a system to partially reduce the NaOH concentration, or if it is desired to increase the water content of the solution, a significant portion of the sodium ions may be added to the remaining sodium ion concentration on the carbonate side of the system. It can be transferred to a new hydroxide chamber that needs to maintain lower sodium ion concentrations. It will be practically appropriate to dilute the brine concentration at this point, as many air systolic designs have some loss of water originally present in the solution. However, process step 2.2, which is a direct analog of process step 1.2, can likewise proceed if the extraction of sodium hydroxide is not entirely complete. By taking a number of these cell alignments (without ending at the end) and integrating them into the stack used in step 2.2 to produce sodium bicarbonate, the driving expression is partially part of the second step of conversion. The power of the concentration driving cell to provide can be used (FIG. 8).

Step 2.2

This process is very similar to step 1.2 above. The difference is that sodium carbonate is delivered in dissolved form, which is likely to be the residual sodium hydroxide left in the feed brine.

Step 2.3 and Step 2.4

Same as step 1.3 and step 1.4.

Process 3

Referring to FIG. 9, the step of electrochemically decomposing sodium carbonate into sodium hydroxide and sodium bicarbonate is removed for process simplicity. Instead, weak acids are used to produce carbon dioxide directly. Since this implementation is included for simplicity and allows this to take advantage of future art techniques, it will reach the most efficient implementation for acid / base separation in some specific acid / base pairs. It is of course also possible to create a hybrid process in which steps 1.1 and 2.1 can only be pushed farther than the carbonate boundary and expanded. As an alternative, the electrochemical separations in steps 1.2 and 2.2 can be used but stop without complete formation of sodium bicarbonate.

Step 3.1

This step separates sodium carbonate from sodium hydroxide in the feed brine. This step can be done as either step 1.1 or step 2.1. It can also be completely removed by introducing the hydroxide carbonate mixture in step 3.2.

Step 3.2

This step is similar to steps 1.3 and 2.3, but this requires twice as much acid. The advantage of such an implementation is the substantial streamlining of the flow sheet.

Step 3.3

This step is similar to 1.4 and 2.4, but it requires twice as much acid.

Process 4:

Referring to FIG. 10, process 4 starts the same as process 1 and process 2, but the acid decomposition is then replaced by a bipolar membrane process that removes carbon dioxide from the solution.

Step 4.1

This step is the same as step 1.1 or step 2.1.

Step 4.2

This step is the same as step 1.2 or step 2.2.

Step 4.3

NaHCO ₃ electrochemically separated with carbon dioxide and sodium hydroxide. This is based on electrodialysis using bipolar membranes. In order to obtain high pressure carbon dioxide, the electrodialysis unit must be introduced into a pressure vessel and maintain the required carbon dioxide pressure throughout the cell. For this reason, it is preferable not to combine step 4.2 and step 4.3 because of increasing the size of the unit that needs to be kept under pressure. However, it is possible to combine two units into one. The advantage of such a design would be a reduction in process steps. It is even possible to combine all three units into one. Another practice is to use other electrochemical means, such as, for example, an electrolysis system using hydrogen electrodes that generate hydrogen on the cathode and consume hydrogen generated at the cathode for the anode.

Process 5:

Processes 5 and 6 extract carbon dioxide from sodium bicarbonate brine while at least partially producing sodium carbonate, thereby introducing a new recycle loop between the final stage and the upstream stage. Process 5 precipitates sodium bicarbonate, while process 6 implements the water soluble form of the process. As a result, this process is well suited to the practice of producing carbonates and using these carbonates as new absorbents for carbon dioxide acquisition. See FIG. 11:

Step 5.1

This step is the same as step 1.1 or step 2.1.

Step 5.2

This step is the same as step 1.2 or step 2.2. However, the feed to the unit consists of recycled sodium carbonate, partially derived from step 5.1 and partially derived from step 5.5.

Step 5.3

Increasing the concentration of sodium bicarbonate by removing water. This is best done by allowing water to pass through concentrated brine through the permeable membrane. There are two possible sources for this brine. (1) concentrated brine leaving the air constrictor; This is particularly useful if step 5.1 follows 2.1; (2) Concentrated brine derived from step 5.1 if step 5.1 is similar to step 1.1 and results in a solid sodium carbonate precipitation. The result is concentrated brine of sodium bicarbonate. It is necessary to be included in an airtight container to contain a pressure higher than the ambient carbon dioxide partial pressure for the solution.

Another option for dewatering the brine is to reverse the conventional electrodialysis unit (without a bipolar membrane). Rather than using pure water to be reused elsewhere in the cycle (the whole system loses water), brine concentrated on other sides of the membrane will be collected for further use. The advantage of this approach is that it requires a smaller volume to pass through the membrane, but requires a continuous electromotive force.

Step 5.4

Temperature fluctuations to precipitate sodium bicarbonate from brine. Temperature fluctuations are not as efficient as temperature fluctuations for the precipitation of Na ₂ CO ₃ . However, operating between 25 and 0 ° C. allows removal of approximately one third of sodium bicarbonate. Heat exchange between supply and discharge minimizes heat loss in the system. The remaining brine is returned to step 5.3 for further dehumidification.

Step 5.5

Calcination of solid sodium bicarbonate to form sodium carbonate and pressurized carbon dioxide. In order to pressurize carbon dioxide, a calciner is received in a pressure vessel. Such systems may utilize various sources of waste heat, for example, from refineries or power plants. Another alternative could be solar energy with the benefit of carbon neutral. If fossil carbon is used, the heat source will use oxygen rather than air and will collect carbon dioxide from its combustion. The hydrogen and oxygen generated in the upstream electrodialysis unit will provide another carbon dioxide that is liberated from the supply of energy. Alternatively, a small portion of the sodium carbonate produced can be used to partially absorb the carbon dioxide produced from the combustion process. This sodium bicarbonate brine is returned to step 5.3 for dehumidification. The remaining sodium carbonate is returned to step 5.2. The carbon dioxide stream leaves the unit.

The advantage of this practice is that it reduces electricity demand and replaces it with partially lower grade heat. Therefore, this method is particularly useful in areas with high power or very high concentrations of carbon dioxide. Methods 1-4 are advantageous in areas with low cost, low carbon power supply. For example, excess wind power from hydro or large wind mill farms.

Process 6

Process 6 is similar to process 5 but replaces precipitation / calcination with pyrolysis of sodium bicarbonate directly in solution. The advantage of process 5 is that it is easy to create a high pressure in the carbon dioxide stream, while the advantage of process 6 is that it is easy to implement and follows the conventional process stream. See Figure 12:

Step 6.1

This step is the same as in step 5.1.

Step 6 .2

This step is the same as step 5.2.

Step 6 .3

This step is the same as step 5.3, but the concentration is kept lower than for 5.3 and this step may be omitted in some implementations.

Step 6.4

Temperature fluctuations that heat the solution to remove carbon dioxide from the brine and return the brine enriched in sodium carbonate to step 6.2. Heat exchangers are used to minimize energy demand. Water condensation can be handled inside the unit. Reference is made to the description below. Potential heat sources are similar to those listed in step 5.5. Some of the brine produced in step 6.2 can be used to absorb the carbon dioxide produced during the heat generation process. The resulting sodium carbonate rich brine is returned to step 6.2.

Process 7:

Process 7 is similar to processes 5 and 6 in that it does not make an attempt to precisely operate the carbon dioxide generating unit between sodium bicarbonate and carbonate and drive electrodialysis of the carbon dioxide generator past this point. In fact, it will stop slightly before that point in order to prevent producing a high pH solution. See FIG. 13.

Step 7.1

This step is similar to step 6.1.

Step 7.2

This step is similar to step 6.2.

Step 7.3

This step is similar to step 6.3.

Step 7.4

Cells replacing anionic and bipolar membranes with basic saline starting with bicarbonate solution and acidic saline starting with pure water, the voltage applied above removes bicarbonate ions and carbonate ions through the anion membrane to produce carbonic acid on the acidic side This will release carbon dioxide. With the removal of the carbonate anion, the brine on the base side gradually rises in pH. The process should be stopped when the OH ⁻ concentration begins to complete the dissolved inorganic carbon. This allows the conversion of bicarbonate brine to carbonate brine.

The remaining carbonate brine is returned to the previous unit, whereby it is converted back to bicarbonate brine after some dehumidification.

Description of the process

The processes outlined above represent different optimizations for different situations and different goals. The best proved will depend on the typical temperature at which the unit operates, the cost depending on the region and the carbon concentration of the power supply, the process of the various electrochemical designs to generate the acid and base. As this field is still new and fluid, it is possible to move more and more with sufficient electrochemical design over time.

Processes 1 to 4, which depend entirely on the second acid to complete the conversion of the spent solvent to carbon dioxide and fresh solvent, make it possible to independently optimize the acid / base separation and pressurization of the carbon dioxide. The advantage of these methods is that they completely eliminate the need for a compressor to remove carbon dioxide to reach pipeline pressure. The same applies to Process 5, but the optimum pressure that can be reached for Process 6 is limited by the temperature to remove carbonate / bicarbonate brine. One advantage of process 6 is that step 6.4 has been implemented in the past on a large scale, thereby reducing the cost uncertainty associated with scaling up the new process.

Other processing units can be integrated into the entire stream to handle embodiments with impurities. For example, carbonate brine arriving from an air constrictor must be filtered to remove dust buildup.

Although more specific implementation of the unit process that is optimized for the design of the present invention is described in more detail below, standard implementation may be used for all process units.

Implementation of Separation of Carbonate into Bicarbonate and Hydroxide

In principle any implementation of established electrochemical processes for separating acids and bases can be employed for the process units of the invention. Not all of them rely on bipolar membranes, but many of them rely on bipolar membranes. One developed for this purpose combines a series of cationic and bipolar membranes. The system is terminated at two standard electrodes producing oxygen and hydrogen. This will be responsible for some percentage amount of total energy consumption. Two standard electrodes are coupled to the process through the fuel cell or in processes 5 and 6, which require heat, they can burn to generate heat without the release of carbon dioxide.

Sodium ions follow either a concentration gradient or an electric gradient from the mixture that accumulates sodium hydroxide and then enters the cell. Different regions of the cell can act at different concentrations to minimize potential differences in the system. In particular it is possible to include an upstream separation of the hydroxide from the carbonate which can be blown with only a concentration gradient as mentioned above. Since none of the units reach acidic pH, the proton concentration is small enough everywhere to avoid the need for components separated by the anionic membrane. The system is therefore simpler than known bipolar membrane systems which require proton current control. For these cells negative ions do not leave the cell from which they originate. The advantage of extracting sodium carbonate from solvent brine prior to this step is to reduce the amount of sodium passing through this membrane. However, a simple form of the process can eliminate the first step.

Execution of Mountain Propelled Carbon Dioxide Generator

Mixing the acid with sodium carbonate or sodium bicarbonate results in the generation of intense carbon dioxide. If the acid is strong enough, the whole process can generate a high carbon dioxide pressure if the reaction occurs in a vessel maintained at the required pressure. One possible use of such a system is to generate carbon dioxide at pressures above the pipeline pressure, eliminating the need for subsequent compression.

One possible implementation of such a system is to plan three small reservoirs, one with acid, the other with bicarbonate, and the third with acid salts (eg sodium chloride). Bicarbonate and acid are injected from each reservoir into the flow channel formed to enhance the mixing of the two fluids. If the acid is weak and hence the reaction is slow, it is also possible to introduce vigorously stirred container vessels. In a fast reactor, the mixing channel rises to a high point where the gas separates from the liquid stream that is later channeled down the groove to enter the salt solution reservoir again. Inside the acid and base reservoir the injector may be mechanically coupled to the salt discharge reservoir. The mechanical energy used at the outlet is sufficient to drive the infusion pump. Direct mechanical coupling may be based on a mechanically connected piston displacement pump. Small turbines can likewise be combined together. There are many technical approaches in this field that allow for mechanical coupling.

The small system can instead operate in a batch operation where the input tank and output tank are separated by, for example, diaphragms. Filling an empty input tank when pressure is released causes the full output tank to empty gradually. The system is then pressured to separate from the environment and two fluids are pumped from the input tank to the output tank to generate carbon dioxide. Once the output tank is filled, the carbon dioxide line is closed by the valve and the cycle repeats itself. Other implementations may use a piston that effectively replaces the moving diaphragm.

It is of course also possible to provide an electrical coupling by converting the output energy of the salt stream and the carbon dioxide stream into electrical energy. Small disharmony in volume can be compensated by extracting some energy from the carbon dioxide output line. In principle, this can be a substantial source of mechanical energy that meets a large number of pumping requirements within the overall system. This ability can be used to control the mismatch in concentration between carbonic acid and acid used to drive the system.

In this way acid production is a convenient way of providing mechanical energy that is removed from the emitted carbon dioxide.

Before injecting carbon dioxide into the output stream, the carbon dioxide needs to be cleaned and dried to meet all the requirements given in the particular application or special arrangement.

Water Handling in Thermal Fluctuations CO2 Generator

When heating the bicarbonate solution, the carbon dioxide will carry water vapor that needs to be condensed with it. The carbon dioxide flowing out of the solution at a certain pressure and exiting the reservoir mixes with water vapor. In the next step, carbon dioxide is used to preheat the incoming solution and in the process carbon dioxide condenses water vapor. As increasing the brine concentration increases the partial pressure of carbon dioxide throughout the solution, the collected water is sufficiently preserved from bicarbonate.

Water can be used to provide an input feed to produce fresh sodium bicarbonate through the electrochemical acid / base separation process in step 6.2.

As the opportunity for carbon dioxide is depleted in the petroleum industry, work will be undertaken to establish regulatory permits for carbon credit "credits" obtained through compulsory management. This “credit” will then have market value used in a number of ways. One possibility is for local agents to provide “credit guarantees” to automakers or buyers as a means of sponsoring mileage, while continuing to design public vehicle designs that do not perform to the required level. To allow.

While the motor vehicle or truck is driven by known internal combustion engine technology (or an improved propulsion system that depends on hydrocarbon fuel), at the same time a zero emission motor vehicle since sufficient carbon dioxide has already been removed from the atmosphere via the method according to the invention. It is not at all illogical to see when a request is made. This could be prepared by a supplementary guarantee attached to the purchase of a car or truck, or by regulatory requirements placed in the transportation industry, or some other agreement that would one day have to be defined. Or a person with a social conscience could “buy-out” carbon in advance when buying a car.

Although the present invention is particularly useful for extracting carbon dioxide from air, the air scrubber of the present invention can be used to remove other gases by using different absorbent materials.

Claims (38)

Exposing the surface covered with the absorbent to an air stream maintained in a laminar or having a flow close to the thin layer area. The method of claim 1, comprising one or more of the following features: (a) the surface comprises smooth parallel plates; (b) the surface is not entirely flat and follows a straight parallel in the direction of the air flow; (c) the surface comprises an angled shape or any combination thereof similar to corrugations, pipes, tubes, harmonica covers, but the air flow follows a straight line; (d) the surface is roughened with grooves, dimples, bumps or other small structures smaller than the surface spacing, where the surface structure is sufficiently maintained within the thin layer boundary of the air flow; (e) The surface is roughened with grooves, dimples, bumps or other small structures and is roughened around small grooves, dimples, bumps or other small structures. The Reynolds number of the flow is small and optimally between 0 and 100; (f) the surface is roughened by sand blasting or other similar means; (g) the surface is roughened via etching or other similar means; (h) the surface is on a plate made of steel or other hydroxide resistant metal; (i) the surface is on a plate made of glass; (j) the surface is on a surface made of plastic, preferably polypropylene; And (k) The surface is coated or treated to increase the hydrophilicity of the plate. The carbon dioxide from the air of claim 1, wherein the surface is held tight by a wire and becomes a foil or other thin film supported by a rigid wire or wire netting. How to obtain. The method of claim 3, comprising one or more of the following features: (a) all wires except some supporting wires in front and rear extend parallel to the wind flow direction; (b) the thin film or film is supported on a rigid structure that can be a rigid plate, honeycomb, or lattice work that can impart structural robustness to the film; (c) the film is made of a thin plastic film; And (d) The film is made of a thin plastic film that is a surface treated to increase the hydrophilicity of the surface. The method of claim 1, comprising one or more of the following features: (a) the direction of air flow is horizontal; (b) the surface-or line of symmetry-is perpendicular; (c) the liquid solvent stream is nearly perpendicular to the air flow direction; (d) the surface spacing is about 0.3 cm to about 3 cm; (e) the surface length is approximately perpendicular to the air flow direction and is about 0.30 m to about 10 m; (f) the air flow speed is from about 0.1 m / s to about 10 m / s; (g) the distance of air flow between the surfaces is about 0.10 m to about 2 m; (h) liquid solvent is applied by spraying the flow on the upper edge of the surface; (i) solvent is applied to both sides of the plate; (j) solvents are applied in a pulsed manner; (k) liquid solvent is collected at the surface or the bottom of the plate; (l) the liquid solvent is collected at the surface or the bottom of the plate, and the collected fluid is passed immediately to the recovery unit; (m) liquid solvent is collected at the surface or bottom of the plate and the collected fluid is recycled to the top of the scrubbing unit for further carbon dioxide collection; (n) the device is further installed to minimize loss from misalignment between the surface and the instantaneous wind zone, including an airflow straightener; And (o) Includes a structure that passively or actively adjusts the surface to face the wind. In a thin layer air scrubber that utilizes the pressure drop generated by natural air flow, (a) stagnation of air in front of the scrubber; (b) a pressure drop created by a flow substantially perpendicular to the inlet and / or outlet of the scrubber; or and (c) a pressure drop produced by thermal convection. The thin layer air cleaner of claim 6, comprising one or more of the following features: (a) the pressure drop is created by cooling convection or by heat convection along the hill side; (b) a plurality of lamellas wetted at least in part by a liquid absorbent; And (c) The spacing between lamellae is chosen so that the system does not change the lamellae flow area, and is preferably about 2 to 4 mm. The method of claim 1, wherein the surface is assisted by the wetting of the disk and the air moves perpendicular to the axis. The method of obtaining carbon dioxide from air according to claim 8, comprising one or more of the following features: (a) the axis is approximately horizontal, the disc is immersed in solvent at the rim, and the circulating motion promotes separation of fluid from the disc; (b) liquid is sprayed onto the disk as the disk moves by radially aligned injectors; And (c) The liquid is ejected to the disk near the shaft. The method of claim 1, wherein the surface is a circular concentric tube or other cross-sectional shape with air flowing in the direction of the tube axis. The method for obtaining carbon dioxide from air according to claim 10, comprising one or more of the following features: (a) the tube rotates about a central axis; (b) the tube has an approximately vertically oriented axis and the solvent is applied in such a way that the solvent flows downwardly from the surface of the tube; And (c) The tube has an axis pointing at an angle to be perpendicular, and the solvent is inserted at a single point at the top inlet and flows downward in a spiral motion covering the entire surface. The method of claim 1, wherein the solvent is a hydroxide solution. The method of claim 12, comprising one or more of the following features: (a) the hydroxide concentration is from 0.1 to 20 moles; (b) the hydroxide concentration is 1-3 moles; (c) the concentration of the solution is greater than 3 moles; (d) the concentration of the solution is adjusted to minimize water loss and water gain; (e) the concentration of the solution is allowed to adjust by itself until the vapor pressure of the solution matches the vapor pressure of the ambient air; (f) the hydroxide is sodium hydroxide; (g) hydroxide is potassium hydroxide; (h) a solvent is a hydroxide solution to which an additive or surfactant is added; (i) the solvent is a hydroxide solution comprising an additive or surfactant which increases the reaction kinetics of carbon dioxide with the solution; (j) the solvent is a hydroxide solution comprising an additive which reduces the vapor pressure of water to the solution; (k) solvents include additives or surfactants that change the viscosity or other rheological properties of the solvent; And (l) A solvent is a hydroxide solvent which contains the additive or surfactant which improves the water absorption of a solvent in order to wash | clean gas other than carbon dioxide from air. Extracting carbon dioxide from ambient air in an area remote from the area where the carbon dioxide was generated, using an absorbent, and selling, selling, or delivering the resulting carbon credit to a third party, How to generate tradable carbon credits. The method of claim 14, wherein carbon dioxide is obtained from ambient air by the process of claim 1. The method of claim 14, wherein carbon dioxide is obtained from ambient air using the apparatus of claim 6. 15. The method of claim 14, wherein the carbon credit is sold, sold or delivered with the sale or lease of the car or truck or fuel for the car or truck. The method of claim 14, wherein the carbon credit is sold by the producer of the hydrocarbon fuel. In the method for separating hydroxide / carbonate brine into hydroxide and carbon dioxide, Brine is first concentrated to approach the carbonate saturation point; Concentrated hydroxide carbonate brine then separates the carbonate from the brine via thermal shaking precipitation; The carbonate is electrochemically separated into a sodium hydroxide and sodium bicarbonate solution in a first electrochemical process step; Bicarbonate is mixed with an acid to release carbon dioxide and the acid is recovered as a salt in a second electrochemical process step. The method of claim 19, comprising one or more of the following features: (a) the sodium hydroxide solution and the sodium bicarbonate solution are separated from the brine by electrodialysis using a bipolar membrane; (b) the second electrochemical process comprises electrodialysis using a bipolar membrane; (c) brine is treated without initial concentration; (d) at least some of the carbonate is separated from the hydroxide in a second electrochemical process step; (e) acid is used to neutralize the brine before the brine releases carbon dioxide; (f) Acid injection is used to neutralize the brine before releasing carbon dioxide, wherein the acid injection is used in a first low pressure unit to adjust the mixture to a pH level supporting the formation of bicarbonate and in a second high pressure system generating carbon dioxide. Done; (g) carbon dioxide is released in an electrochemical process involving electrodialysis using a bipolar membrane; (i) carbon dioxide is released in an electrochemical process that produces hydrogen at the anode and uses hydrogen again at the hydrogen cathode; (j) the carbonate is separated from the hydroxide in the last step; And (k) All or some hydroxides and carbonates are separated in the carbon dioxide release step. The volume is separated into cells by a membrane crossing between the bipolar membrane and the cationic membrane, and the fluid flowing in all other chambers is concentrated with hydroxide / carbonate brine, while providing the hydroxide ions and protons needed to maintain charge neutrality in the cross chamber. And partially separating the hydroxide / carbonate brine into a hydroxide solution and a carbonate solution in a device through which a dilute sodium hydroxide solution with sodium ions passing across an anionic membrane and a bipolar membrane. The method of claim 21, comprising one or two of the following features: (a) the cells are arranged in a stack having a liquid connection between the first and last cells containing the same type of saline; (b) the cells are arranged in a toroidal shape; And (c) Cells are aligned in a stack comprising two separate cells. A method for separating hydroxide and carbon dioxide from hydroxide / carbonate brine, Using an electrochemical process to separate the hydroxide solution from the carbonate solution; The carbonate is separated into sodium hydroxide by the electrochemical method and the sodium bicarbonate solution is separated in the first electrochemical process step; Bicarbonate is mixed with acid to release carbon dioxide; The acid is recovered from the salt of the acid via a second electrochemical process step. The method of claim 21, comprising one or more of the following features: (a) the sodium hydroxide solution and the sodium bicarbonate solution are separated from the brine by electrodialysis using a bipolar membrane; (b) electrochemical processes for recovering acid from salts of acids include electrodialysis using bipolar membranes; (c) brine is treated without initial concentration; (d) at least some of the carbonate is separated from the hydroxide in a second electrochemical process step; (e) acid is used to neutralize the brine before the brine releases carbon dioxide; (f) acid injection is used before the brine releases carbon dioxide, the acid injection being performed in a first low pressure and a second high pressure system generating carbon dioxide to adjust the mixture to a pH that supports the formation of bicarbonate; (g) carbon dioxide emissions are carried out in an electrochemical process; (h) carbon dioxide is released by electrochemical methods in a pressure vessel to provide high pressure carbon dioxide; (i) carbon dioxide is released in an electrochemical process involving electrodialysis using a bipolar membrane; (j) carbon dioxide is released in an electrochemical process that generates hydrogen at the anode and again uses hydrogen at the hydrogen cathode; (k) carbonate is separated from the hydroxide in the last step; And (l) All or some hydroxides and carbonates are separated in the carbon dioxide release step. 20. The process of claim 19, wherein sodium bicarbonate requires pyrolysis to sodium carbonate and carbon dioxide accompanied by recycling sodium carbonate to the initial stages of the process. The method of claim 25, comprising one or more of the following features: (a) The bicarbonate solution is reduced in water content through membrane separation by concentration gradient or electrochemical gradient (reverse electrodialysis), and the bicarbonate is from brine concentrated by thermal fluctuation precipitation accompanied by carbon dioxide and carbonate thermoplastics of bicarbonate. The resulting dilute bicarbonate outlet stream is recycled to another dehumidification process of the bicarbonate solution; (b) the bicarbonate solution is heated until carbon dioxide is released with carbonate / bicarbonate brine electrochemically retreated with bicarbonate; (c) the bicarbonate solution comprises carbon dioxide in a pressure vessel; (d) a heat exchanger between the supply and the output of the thermal stage to minimize energy consumption; (e) the resulting dilute water stream is kept free from brine and treated off-water; (f) a dilute water stream is used to replenish water in the feed in the air constrictor unit; (g) the base ion is sodium; (h) the base ion is potassium; (i) the base ions are a mixture comprising sodium and potassium; And (j) Bases include organic bases. 22. The process of claim 21, wherein sodium bicarbonate requires pyrolysis to sodium carbonate and carbon dioxide accompanied by recycling sodium carbonate to reach the initial stage of the process. The method of claim 27, comprising one or more of the following features: (a) Sodium bicarbonate solution reduces water content through membrane separation by concentration gradient or electrochemical gradient (reverse electrodialysis), and bicarbonate is concentrated by thermal fluctuation precipitation accompanied by carbon dioxide and carbonate thermoplastics of bicarbonate. Extracted from brine and the resulting dilute bicarbonate outlet stream is recycled to another dehumidification process of the bicarbonate solution; (b) the bicarbonate solution is heated until carbon dioxide is released with carbonate / bicarbonate brine electrochemically retreated with bicarbonate; (c) the bicarbonate solution comprises carbon dioxide in a pressure vessel; (d) a heat exchanger between the supply and the output of the thermal stage to minimize energy consumption; (e) the resulting dilute water stream is kept free from brine and treated off-water; (f) a dilute water stream is used to replenish water in the feed in the air constrictor unit; (g) the base ion is sodium; (h) the base ion is potassium; (i) the base ions are a mixture comprising sodium and potassium; And (j) The base is an organic base. A reservoir for holding an acid, a reservoir for holding a base and a reservoir for holding a production salt; A line in fluid communication with the acid and base reservoirs and having a structure that enhances mixing; A gas separation unit for supplying carbon dioxide under pressure to the outlet pressure valve and connected to the salt reservoir; Apparatus for producing carbon dioxide by mixing acid and bicarbonate, comprising a combination of outlet lines from a salt brine reservoir mechanically connected to a pump for supplying acid and base to a reservoir holding an acid and a base, respectively. . 30. The apparatus of claim 29, comprising one or more of the following features: (a) carbon dioxide provides most of the pumping power requirements for the device; (b) further comprising a device for converting the excess pressure above the carbon dioxide outlet valve into usable power; And (c) The excess pressure is converted into usable power which can be grooved by two feed pumps or used elsewhere. It contains three reservoirs for holding acid, containing base, and containing production salt, the reservoirs being separated from each other by a membrane, the apparatus adding fresh fluid to ambient pressure, and fluid producing carbon dioxide Apparatus for generating carbon dioxide by mixing acid and bicarbonate, characterized in that operated in a batch mode that is pressurized in the process. In the apparatus for separating alkaline brine into cations and bicarbonates, The device comprises a cathode and an anode through which power is delivered, the cations migrate across the cationic membrane, thereby converting the initial brine to bicarbonate, while the brine gradually builds up into a pure hydroxide solution. The device of claim 32, wherein the cation is sodium or potassium, or ions that will not precipitate from solution. A device for separating carbon dioxide from bicarbonate brine comprising carbon dioxide, the device comprising a reservoir having acid and base cells separated by an anionic membrane that crosses with bipolar cells to produce bicarbonate in the stream; Wherein the bicarbonate ions are mixed with the acid in the acid cells producing carbon dioxide, leaving a residual saline rich in carbonate ions in the base cell.  A method of separating carbon dioxide from hydroxide brine according to claim 25, wherein the pyrolysis step is replaced by an electrochemical process according to claim 34. 36. The method of claim 35, wherein the carbon dioxide generating unit is pressurized to deliver a carbon dioxide concentrated stream. A process for separating carbon dioxide from hydroxide brine according to claim 27, wherein the pyrolysis step is replaced by an electrochemical process according to claim 36. 38. The method of claim 37, wherein the carbon dioxide producing unit is pressurized to deliver a concentrated stream of carbon dioxide.

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