CN204522740U - Fluidized bed system for directly capturing carbon dioxide in mineralized flue gas - Google Patents

Abstract

A fluidized bed system for direct capture of carbon dioxide in mineralization flue gas, comprising: a pretreatment unit including a dry powder grinder for grinding and/or a heating incinerator for heat treatment and/or for an alkaline process Stirred reaction kettle, filter press and drum dryer for desiliconization; flue gas temperature and humidity adjustment unit, set on the bypass of the flue, including a bubble tower filled with liquid, and the flue gas from the bypass enters the bubble tower Realize temperature and humidity regulation; the fluidized bed reactor connects the solid material from the pretreatment unit and the flue gas from the flue gas temperature and humidity adjustment unit; the cyclone separator connects the dusty gas from the fluidized bed reactor to realize gas-solid separation , wherein the gas obtained is sent to the flue and discharged from the chimney. The system of the utility model has a large processing capacity, a small size, and a small footprint, which is convenient for continuous operation and easy to combine with the existing system of the power plant. At the same time, the fly ash after decarbonization is not It affects the original use of fly ash in power plants and has lower decarbonization costs.

Description

A fluidized bed system for directly capturing carbon dioxide in mineralized flue gas

technical field

The utility model relates to the technical field of flue gas carbon dioxide capture and utilization, in particular to a fluidized bed system for directly capturing carbon dioxide in mineralized flue gas.

Background technique

The global greenhouse effect caused by the increase in the concentration of greenhouse gases in the atmosphere has caused icebergs to melt, sea levels to rise, species to decrease, and various climate disasters to occur frequently around the world, causing serious economic losses and threatening human survival. As the most important greenhouse gas, carbon dioxide (CO ₂ ) has become the focus of international climate negotiations for its future total control and emission rights allocation. Governments and energy companies in various countries have paid more and more attention to research on CO ₂ emission control technologies, and some countries have taken the lead in starting substantive decarbonization work. With my country's carbon emissions surpassing that of the United States and international calls for emission reductions, the Chinese government made a commitment to the world in 2009 to reduce carbon emissions per unit of GDP by 40-45% by 2020. China's resource pattern of "rich coal, less oil, and gas" determines that coal is the main body of China's energy supply. The proportion of coal-fired power generation in China's primary energy is close to 65%. Therefore, _CO2 emissions mainly come from coal-fired power plants, accounting for about 65%. 40-50% of total emissions. Carbon dioxide capture and storage technology in power plants will inevitably become the medium and long-term technical demand of my country's low-carbon development strategy.

CO ₂ mineralization and sequestration is a technology that reacts CO ₂ with alkaline earth metals in ores or solid wastes under certain conditions to produce carbonates to achieve carbon sequestration. This technology can achieve permanent storage of CO ₂ , has low environmental risk, wide range of available mineral resources, and strong storage capacity. It is a very potential greenhouse gas emission reduction technology. However, due to the shortcomings of the currently developed _CO2 mineralization process, such as long process flow, low reaction rate, large equipment size, harsh reaction conditions, high energy consumption, difficult recovery of chemical reagents, and secondary pollution, and the main foreign researches are suitable for Serpentine, olivine and other ores used as mineralized raw materials are often used as raw materials for handicraft processing in China, resulting in high raw material prices. All of these hinder the commercialization of CO ₂ mineralization and storage technology in China.

On the other hand, the annual discharge of fly ash from coal-fired power plants in China has reached 100 million tons, and some fly ash has a high content of calcium oxide (CaO) (mass fraction can reach more than 20%), which is very suitable for mineralization and storage CO ₂ in coal flue gas. In addition, there are a large number of solid wastes produced by calcium carbide, cement and iron and steel enterprises, which are also rich in CaO and can also be used as raw materials for mineralization. Therefore, in China, solid waste can be selected as the raw material for CO ₂ mineralization and storage according to local conditions.

Contents of the invention

In order to overcome the above-mentioned shortcoming of the prior art, the purpose of this utility model is to provide a kind of fluidized bed system that directly captures the carbon dioxide in the mineralized flue gas, utilizes high-calcium waste (fly ash, carbide slag, steel slag, waste old cement ) as raw material, using gas-solid phase direct reaction fluidized bed process to capture and mineralize CO ₂ in the flue gas, which can effectively improve the utilization of fly ash and reduce CO ₂ emissions. It is a new type of greenhouse that is very suitable for China's national conditions Gas emission reduction technology.

In order to achieve the above object, the technical solution adopted by the utility model is:

A fluidized bed system for directly capturing carbon dioxide in mineralized flue gas, comprising:

Pretreatment unit 7, comprising a dry powder grinder for grinding and/or a heating incinerator for heat treatment and/or a stirred reactor for alkaline desiliconization, a filter press and a drum dryer;

The flue gas temperature and humidity adjustment unit 9 is arranged on the bypass of the flue, including a bubble tower 15 filled with liquid, and the flue gas from the bypass enters the bubble tower 15 to realize temperature and humidity adjustment;

The fluidized bed reactor 10 is connected to the solid material from the pretreatment unit 7 and the flue gas from the flue gas temperature and humidity adjustment unit 9;

The cyclone separator 11 is connected to the dusty gas from the fluidized bed reactor 10 to realize gas-solid separation, and the gas obtained is sent to the flue and discharged from the chimney 13 .

The outlet pipeline of the bubble column 15 is provided with a thermal insulation device.

SCR reactor 5, electrostatic precipitator 6 and FGD absorption tower 8 are sequentially arranged on the flue along the flow direction of flue gas. The flue gas enters the FGD absorption tower 8 for desulfurization. The bypass is arranged on the flue after desulfurization, and a compressor 14 is arranged in the bypass, and the compressor 14 is arranged before the bubble tower 15 .

Part of the solid product from the cyclone separator 11 is returned to the fluidized bed reactor 10 for recycling.

The device of the present utility model supports the following processes:

The first step is to collect high-calcium waste and grind it for use;

The second step is to open a bypass on the flue gas discharge flue to lead a stream of flue gas through the temperature and humidity regulator to adjust the temperature and humidity. The temperature adjustment range is 40-90 ° C, and the humidity adjustment range is 5-60% (relative humidity) ;

In the third step, the temperature-humidity-adjusted flue gas and the high-calcium waste are contacted and reacted in a fluidized bed reactor;

In the fourth step, the dusty gas exiting the fluidized bed reactor after the reaction is sent to the cyclone separator for gas-solid separation, and the resulting gas is sent back to the original flue gas discharge flue and discharged into the chimney.

Wherein, the high-calcium waste can be fly ash, calcium carbide slag, steel slag or waste cement, etc. It is generally required that the CaO mass fraction is more than 20%, the particle size is 20-80 microns, and has good chemical reactivity. Therefore, depending on the specific situation, it depends on whether the fly ash needs to be pretreated. There are three main pretreatment methods: fine grinding, heat treatment and alkaline desiliconization treatment. Pretreatment methods can be selected according to the specific conditions of the raw materials or used at the same time to meet the requirements of the direct mineralization fluidized bed process. The criteria for judging whether raw materials need to be pretreated include particle size, crystal phase structure and CaO content. After the gray sample is taken for analysis, different pretreatment methods are used in a targeted manner according to the specific situation.

When the flue gas is the flue gas of the power plant, and the high-calcium waste is the fly ash obtained after electrostatic precipitating of the flue gas of the power plant, the capture of carbon dioxide in the flue gas by the fly ash of the power plant is realized.

For example, when fly ash is selected, the following analysis is performed:

(1) Whether it has a particle size of 30-80 microns. In general, the particle size of fly ash is about 40 microns, which is just suitable for the minimum fluidization velocity required by the fluidized bed, and it is not necessary to crush and grind, but sometimes for To further improve the reactivity, fine grinding can be used to destroy the glass phase crystal structure of fly ash to create more lattice defects, and the particle size can be reduced to about 20 microns after further fine grinding.

(2) The crystalline phase in fly ash is mainly corundum mullite and glass phase, the structure is relatively dense, and the surface activity is not high. This is mainly because the fly ash is rapidly cooled in the flue to form small ball-shaped crystals. High-temperature heat treatment at 600 degrees for 2 hours can be used to destroy the crystal structure on the surface of the small balls to improve their chemical reactivity.

(3) Whether the CaO content must be above 20%. For example, Class C fly ash does not need to be pretreated, and Class F fly ash needs to be desiliconized by alkali method. Generally, 0.5-2mol/l NaOH or NaCO ₃ solution is used to press The solid-liquid ratio is 100-250g/l, and the fly ash is hydrothermally reacted at 100 degrees for 3 hours, and the reacted mortar is filtered and dried to obtain the desiliconized fly ash, and the filtrate contains sodium metaaluminate and sodium metasilicate. For aluminum extraction.

The bypass is opened on the flue after desulfurization, of course, it can also be opened before desulfurization, depending on the structural space. The humidity regulator can be in the form of a double-pressure bubble tower, which first saturates the flue gas with water, then controls the outlet pressure, and adjusts the humidity carried by the flue gas from the tower by changing the pressure. The flue gas in the flue is generally under negative pressure (-40kPa). It needs to go through a compressor to increase the pressure to a slight positive pressure (200kPa), and then control the outlet pressure of the bubble tower to adjust the moisture carrying capacity. Note that the flue gas pipeline from the bubble column should be insulated to keep the humidity stable.

The minimum fluidization velocity at the inlet of the fluidized bed reactor is calculated based on the fly ash particles, and generally needs to be above 0.004m/s. The initial bubbling velocity is calculated based on the fly ash particles, and generally needs to be above 0.012m/s. Consider factors such as resistance drop in the case, select the gas flow velocity as 0.1-0.5m/s, the residence time of fly ash in the reactor is 3-20min, and the feed ratio of solid and gas (ash gas ratio) is kept at 5- 15kg fly ash/m ³ flue gas, depending on CaO content and CO ₂ concentration in flue gas. Because the flue gas has a certain humidity, a liquid film will be formed on the solid surface of the fly ash, and the CaO on the solid surface and in the pores will be electrolyzed by the water in the liquid film to produce Ca ⁺ , and the liquid film can also absorb CO in the flue gas. _2. HCO ₃ ^- and CO ₃ ^2- are ionized, and at a certain temperature (60-90 degrees Celsius) Ca ⁺ reacts with HCO ₃ ^- or CO ₃ ^2- to quickly generate calcium carbonate. The ash-containing gas coming out of the fluidized bed reactor passes through the cyclone separator, and the gas is discharged from the upper part, and the lower part is the fly ash containing calcium carbonate whose particle size becomes larger (up to 100 microns) after the reaction. Take a gas sample at the place where the flue gas enters and exits the fluidized bed system, and measure the CO ₂ and SO ₂ content through the flue gas analyzer. It was found that the CO ₂ concentration decreased from about 13% of the inlet to 9%, while the SO ₂ concentration decreased from 100 mg/Nm ³ to 35 mg/Nm ³ .

The decarbonized gas from the top of the cyclone returns to the original main flue and is discharged into the chimney. Part of the fly ash can re-enter the fluidized bed to continue the reaction, while the separated solid product collected in the lower part is returned to the fluidized bed reactor for recycling. . , the reflux ratio is controlled between 1:1-5:1. The solid product can be used to make fly ash cement, or used as foundation filler.

Compared with the prior art, the beneficial effects of the utility model are:

1. The system structure is simple, only including pretreatment (can be canceled if it is C grade high calcium fly ash), temperature and humidity adjustment, fluidized bed and separation system.

2. Avoid using a large number of high-pressure slurry bed reactors in traditional mineralization, and use fluidized bed reactors to facilitate continuous operation, and the device has large processing capacity, small size and less land occupation.

3. The selected solid waste has a very small particle size, which avoids the energy consumption caused by crushing and grinding.

4. It is convenient to combine with the existing system of the power plant, the engineering amount of the transformation is small, and the additional equipment is also small.

5. The carbonation reaction is carried out at a medium temperature of 70-90°C and a low pressure (not exceeding 2 bar), which can reduce energy consumption and achieve rapid carbonation reaction. The CO ₂ removal rate in the flue gas can reach 30% within 5 minutes.

6. Compared with other CO ₂ capture technologies, such as the organic amine chemical absorption method, the cost is 250-350 yuan/ton CO ₂ . The decarbonization cost of this technology is 40-120 yuan/ton CO ₂ . For example, 30% of the _CO2 in the flue gas of coal-fired power plants can be removed at a relatively low cost, which is also very attractive. At the same time, the fly ash after decarbonization does not affect the original use of fly ash in power plants, which means that the raw materials are not consumed, and can still be used as cement additives and building materials, so the raw material cost of this decarbonization process can be approximately ignored .

Description of drawings

Fig. 1 is the structural representation of the utility model.

Detailed ways

The implementation of the utility model will be described in detail below in conjunction with the accompanying drawings and examples.

As shown in Figure 1, the utility model is a fluidized bed system that directly captures carbon dioxide in mineralized flue gas. The high-calcium waste uses power plant fly ash, including: a pretreatment unit 7, a flue gas temperature and humidity adjustment unit 9 , a fluidized bed reactor 10 and a cyclone separator 11. After the raw coal passes through the coal mill 1, it is burned in the boiler system 2 to generate energy and send it to the turbine 3 and the generator 4. The flue gas produced by combustion contains a large amount of fly ash. After the flue gas is denitrated by the SCR reactor 5, it is then dedusted by the electrostatic precipitator 6, and the obtained fly ash is sent to the pretreatment unit 7 for pretreatment. The gas is then desulfurized by the FGD absorption tower 8, and the fly ash after the pretreatment reaches the standard is sent to the fluidized bed reactor 10 through the conveying system 12. A bypass is set on the flue gas pipeline behind the FGD absorption tower 8, and a stream of flue gas is drawn to the flue gas temperature and humidity adjustment unit 9, where the temperature and humidity are adjusted and then sent to the fluidized bed reactor 10. Fly ash and flue gas contact and react in the fluidized bed reactor 10 to achieve the purpose. After the reaction, the ash-containing gas exiting the fluidized bed reactor 10 enters the cyclone separator 11, where the gas-solid separation is completed, and the separated gas is sent to the flue gas main pipe and discharged from the chimney 13 and can be analyzed by a gas component analyzer 16 its ingredients. Wherein, the temperature and humidity adjustment unit 9 includes a compressor 14 and a bubble column 15 filled with liquid.

In the utility model, the pretreatment unit 7 takes fly ash from the fine ash bin of the electrostatic precipitator 6 of the power plant, or transports high-calcium solid waste such as steel slag and cement from the outside. According to actual conditions, the pretreatment unit 7 may include a dry powder grinder, a heating incinerator, a stirred reactor, a filter press, a drum dryer, and the like. Under normal circumstances, firstly, alkaline desiliconization is performed, using a stirred reactor, a filter press, and a drum dryer; then fine grinding, using a dry powder grinder, and finally heating pretreatment, using a heating incinerator. The pretreated fly ash or solid waste is transported to the raw material hopper of the fluidized bed reactor 10 through a pneumatic soot blowing system.

The flue gas temperature and humidity adjustment unit 9 bypasses the flue gas after the desulfurization system of the power plant, and the flue gas is boosted to 0.2 MPa by the compressor 14 . The flue gas then enters the bubble tower 15 filled with liquid. The bubble tower 15 has the function of heating and temperature control, and the moisture carrying capacity of the gas can be adjusted by adjusting the outlet pressure of the flue gas. The rear part of the flue gas temperature and humidity adjustment unit 9 is provided with a humidity sensor to detect the humidity value. The pipeline after the bubble tower 15 is to be insulated and heat-traced to keep the humidity of the flue gas.

The fluidized bed reactor 10 blows the flue gas from the flue gas temperature and humidity adjustment unit 9 into the reactor from the bottom through the air distribution plate and the wind cap, and sets an online continuous sampling port at the air inlet to take the flue gas and analyze its CO ₂ , _The concentration of SO2. The raw material hopper of the fluidized bed adopts pneumatic ash feeding, and N ₂ or compressed air can be used here. The feed enters from the lower part of the reactor at regular intervals according to the set program, and is fluidized by the flue gas at the bottom, and the fluidization velocity changes according to the diameter and density of the particles. The height and diameter of the reaction section and the buffer section of the fluidized bed reactor 10 are designed according to the composition and activity of different samples. The dust-laden gas after the reaction is carried out from the top of the reactor.

The cyclone separator 11 separates the dust-containing gas from the fluidized bed reactor 10 from gas to solid. The cyclone separator 11 is designed and selected according to the particle size of the product after the reaction. Generally, the solid with a particle size of 20 microns can be separated from the gas. After the dust is removed, a gas sampling port is installed on the pipeline to continuously analyze the concentration of CO ₂ and SO ₂ on-line. The ash separated at the bottom of the cyclone separator 11 is the product, and a part of the product can be added back into the raw material hopper to increase the degree of carbonation of CaO in the raw material.

The preprocessing unit parameters described above are as follows:

The parameters of the temperature and humidity adjustment unit are as follows:

Described fluidized bed reactor unit parameter is as follows:

Described cyclone separation unit parameter is as follows:

The online analysis unit parameters are as follows:

A fluidized bed process for directly capturing carbon dioxide in mineralized flue gas can be realized by using the above system. A feasible process example is as follows:

Fluidized bed process for directly capturing carbon dioxide in mineralized flue gas, using high-calcium fly ash from pulverized coal furnace as raw material, CaO content is about 30%, and the main crystal phase is mullite, quartz and a large amount of glassy amorphous state SiO ₂ , D50 is 80 microns, the specific steps are as follows:

In the first step, after analyzing the ash sample, it is found that CaO exists in the form of CaSiO ₃ , and the reactivity meets the requirements. In order to further improve the reactivity, the fly ash is finely ground to reduce the particle size to D50 of 20 microns. Generally, dry powder is used for grinding Machine, grind for 20min. Fly ash can be sampled from the ash bin of the power plant with a pneumatic soot blowing system.

The second step is to open a bypass on the flue after the desulfurization of the power plant to lead a stream of flue gas. First, the pressure is increased to 2bar through the booster, and then adjusted by the temperature and humidity regulator. The temperature is adjusted to 90 degrees Celsius, and the humidity adjustment range 20%.

In the third step, the flue gas with adjusted temperature and humidity is introduced from the bottom of the fluidized bed reactor and blown into the reactor through the air distribution plate and the wind cap. The ratio is maintained at 5kg fly ash/m ³ flue gas. The fly ash is fluidized upward together with the flue gas, the fluidization velocity is 0.1m/s, and the residence time of the fly ash in the reactor is kept at 5min. The dusty gas on the upper part of the fluidized bed is separated from the solid by the cyclone dust collector, and the return flow of fly ash is controlled at a ratio of 1:1. Take a gas sample at the place where the flue gas enters and exits the fluidized bed system, and measure the content of CO ₂ and SO ₂ by the flue gas analyzer. The concentration of CO ₂ is reduced from about 12.3% at the inlet to 7.5%, while the concentration of SO ₂ is reduced from 89mg/Nm ³ Reduced to 21mg/Nm ³ .

In the fourth step, the decarbonized gas from the cyclone separator is returned to the original main flue and discharged into the chimney, and the separated solid product can be used to make fly ash cement, or used as foundation filler.

The utility model can use power plant fly ash (or other high-calcium solid wastes can also be used or added) to directly capture carbon dioxide in mineralized flue gas, and the fly ash with a certain particle size can be directly combined with CO ₂ quick reaction to generate calcium carbonate. First of all, this process directly utilizes the alkalinity of fly ash and the acidic reaction of _CO2 , and it is not necessary to acid-leach metal cations such as calcium and magnesium in the raw material, and then adjust the pH value to react with _CO2 under alkaline conditions, and the process flow is shortened. In addition, the use of a fluidized bed can maximize the amount of flue gas treatment per unit time, and reduce the size and footprint of equipment. Finally, the process can be carried out only by maintaining a certain temperature and humidity, without using high temperature and high pressure process conditions, which reduces the energy consumption of the process. Therefore, the disadvantages of long traditional _CO2 mineralization process, large equipment size, high energy consumption and high cost are overcome.

Claims (4)

1. directly trap a fluidized system for mineralising carbon dioxide in flue gas, it is characterized in that, comprising:

Pretreatment unit (7), comprise dry powder mill for grinding and/or for heat add thermal incinerator and/or for the stirred autoclave of alkaline process desiliconization, filter press and rotary drum drier;

Flue-gas temperature humidity adjustment unit (9), is arranged in the bypass of flue, comprises the bubble tower (15) that liquid is housed, and the flue gas going out bypass enters bubble tower (15) and realizes temperature and humidity regulation;

Fluidized-bed reactor (10), picks out the solid material of pretreatment unit (7) and goes out the flue gas of flue-gas temperature humidity adjustment unit (9);

Cyclone separator (11), the dusty gas picking out fluidized-bed reactor (10) realizes gas solid separation, and wherein gained gas is delivered to flue and discharged from chimney (13).

2. directly trap the fluidized system of mineralising carbon dioxide in flue gas according to claim 1, it is characterized in that, described flue is disposed with SCR reactor (5) along flow of flue gas direction, electrostatic precipitator (6) and FGD absorption tower (8), described electrostatic precipitator (6) gained dust delivers to pretreatment unit (7) as solid material, electrostatic precipitator (6) gained flue gas enters FGD absorption tower (8) and carries out desulfurization, described bypass is arranged on the flue after desulfurization, compressor (14) is provided with in bypass, before compressor (14) is arranged at bubble tower (15).

3. directly trap the fluidized system of mineralising carbon dioxide in flue gas according to claim 1, it is characterized in that, a part for the solid product of described cyclone separator (11) is recycled to fluidized-bed reactor (10) and recycles.

4. directly trap the fluidized system of mineralising carbon dioxide in flue gas according to claim 1, it is characterized in that, the outlet conduit of described bubble tower (15) arranges attemperator.