RU2015158C1 - Method for purification of contaminated gas fuel - Google Patents

Abstract

FIELD: purification from resin. SUBSTANCE: contaminated gas fuel is introduced to a separate shaft-type reactor having a circulating fluidized bed of finely divided calcium and magnesium carbonate preferably in the form of dolomite or its sintering products. The gas to be purified goes to work as fluidizing agent. Purification is performed at a temperature of 600 - 1000 C. The fluidized bed density averages 80-250 kg/m³. After reactivating due to carbon precipitation the material is withdrawn and activated. Activation is conducted by a an oxygen-containing gas and/or steam at a temperature of 600 - 1000 C. The velocity of the gas flow in reactor is preferably below 10 m/s residence time of gas in reactor ranging from 0.2 to 20 s. When purified the gas fuel is cooled to 150 - 300 C and dedusted. The residual contents of resin and ammonia gas varies from 500 to 300 mg/m³ respectively. After purification HCL concentration is lowered to thermodynamic balance level. EFFECT: increased efficiency of process. 6 cl, 1 dwg

Description

 The invention relates to a method for purifying a crude gas obtained from a carbon material by a gasification process, in which the purification takes place in a secondary zone separated from the gasifier of the gasification process.

 Crude gas produced from various types of biofuels and used as fuel is a valuable substitute for oil in cases where its application makes the direct burning of solid fuel impossible, for example, when calcining lime or converting existing oil-fired boilers.

At temperatures below 1200 ^{° C} in the raw gas produced by gasification of a carbonaceous material such as coal, peat, bark, wood or fuel from waste, always present resin which limits the use of the hot combustion gas in direct or close contact with the gasifier. Operational problems caused by the deposition of resin on devices and fittings are a big problem, limiting the possibilities of use. In addition, during the burning of hot gas, nitrogen and, in some cases, also sulfur (for example, from peat), which are present in the bound state in resins, as well as ammonia, Н ₂ S (from peat) or НСl (from fuel from waste) contribute to emission into the environment NO _x , SO _x , Hcl and chloride hydrocarbons, i.e. dioxins.

A known method of purification of untreated combustible gas obtained by gasification from a carbon material, comprising contacting the gas to be purified with dolomite particles in a fluidized bed in a circulation mode. The gas to be cleaned is a fluidizing agent, its feed rate is 1-10 m / s, the temperature of the cleaning process is 700-1100 ^о С, the particle size of dolomite is less than 1 mm. The known method does not provide low residual concentrations of resin, ammonia and hydrogen chloride.

 The purpose of the invention is to reduce the residual concentration in the combustible gas of the resin in the form of organic compounds, ammonia and hydrogen chloride in the presence of the latter.

 This goal is achieved using the process according to the invention having the features indicated in the claims.

 The invention relates to a method for purification of a crude gas containing tar and ammonia, in special cases also containing significant amounts of hydrogen chloride, the gas being produced using an arbitrary gasification process from carbonaceous material, such as bark, wood, peat or fuel, from waste in the primary zone. In the secondary zone, in contact with the corresponding active (catalytic and possibly sorbing) material, for example calcium carbonate - magnesium, preferably dolomite, the resin and ammonia present in the crude gas are converted. In special cases, sorption of hydrogen chloride occurs simultaneously. The secondary zone consists of a quick circulation fluidized bed shaft containing shaft material, at least mainly in the form of an active material, for example dolomite.

 A sufficient degree of conversion of resins and ammonia and, in special cases, simultaneous sorption of hydrogen chloride can be achieved first by separating the resin-containing gas from the pyrolyzed larger fuel particles in the gasification zone and then in the secondary zone in the form of a rapid circulation mixture with a fluidized bed where contact is made gas with the corresponding active material, such as dolomite, with the corresponding process parameters.

 If the carbonaceous material also contains sulfur in significant quantities, which is typical, for example, for peat, then sorption of hydrogen sulfide will certainly occur on the catalytic and sorbing material.

The amount of active material that is required relative to the amount of crude gas is determined by the required spatial velocity for the catalytic conversion of resins and ammonia and depends on several parameters, such as temperature, gas residence time in the process, particle size of the active material, partial pressure of substances involved in reactions and the degree of deactivation of the active material. Too low a temperature and / or partial pressure of CO ₂ can lead to the conversion of the resin, causing the deposition of coal on the active material, which leads to deactivation. If this happens, the material can be activated by treatment with an oxidizing gas, such as air and / or steam. Sorption of HCl (and / or H ₂ S) occurs so quickly at the temperature of the process that these reactions begin to be almost completely determined by the level of equilibrium and lead to the consumption of the active material corresponding to the formed solid chloride (and sulfide, respectively).

 Thus, the sorption of chloride (and in some cases also hydrogen sulfide) on an active material, such as dolomite, is a quick reaction and requires the presence of a significantly lower amount of active material with respect to gas flow than the catalytic conversion of resins and ammonia.

 The use of a secondary zone in the form of a quick circulation fluidized bed creates significant advantages.

 Such a shaft is capable of removing dust brought from the gasifier, provides very even temperatures in the reaction zone, as well as homogeneous contact between the gas and the shaft material, that is, it creates a slight risk of fluctuations in the degree of sorption conversion. In addition, the particle size can be significantly reduced for those cases in which it is necessary to ensure an increase in conversion at a given temperature and spatial speed. Significant erosion of the shaft material also leads to an increase in the permissible active surface. Further, the secondary zone, designed as a quick circulation mixture with a fluidized bed, it is advisable to combine with an arbitrary gasifier in combination with such a shaft, which is equipped simply with a primary particle separator, or another type of gasifier. With increasing scale, relatively small diameters are also achieved, since gas velocities can be maintained at a relatively high level, up to about 10 m / s, preferably up to 6 m / s.

 In the event that the gasifier consists of a gasifier in combination with a quick circulation shaft with a fluidized bed, a direct connection can be made after the primary separation of dust. If the active material is used as a shaft material in a gasifier in combination with a quick circulation shaft with a fluidized bed, the secondary zone can be advantageously combined with a gasifier, for example, so that after the secondary zone the dust from the secondary particle separator comes as a result of full or partial recycling in the gasifier.

The necessary amount of active material in the reactor core of the secondary zone to ensure a sufficient degree of metal conversion of the resin and ammonia is controlled by adding to the total amount and by controlling the recirculation of the shaft material. The desired degree of conversion determines the appropriate combination of temperature, particle size and amount of active material. Due to abrasion, deactivation and / or sorption of HCl (and possibly H ₂ S), the consumed active material is replaced by adding appropriate amounts of fresh active material and / or activation of such material. The gas residence time in the process can be controlled by a combination of diameter and height above the gas inlet.

 In those special cases where HCl is present in significant quantities in the crude gas, the presence of the active material in the gas after it is discharged from the secondary zone means that the sorption of HCl has improved, since it becomes thermodynamically more complete at lower temperatures, provided that the purified the gas is cooled to a substantially lower temperature before the final dust removal.

 The drawing schematically shows a gasification and gas purification system, which is an embodiment of the invention.

 PRI me R. In the system depicted in the drawing, the carbonaceous material 1 enters a gasifier 3, which consists of a quick circulation shaft with a fluidized bed. It includes a reactor 44, a primary separator 45, and a recirculation device 46 for mine material that has undergone separation in the primary separator. Mine material consists of active catalytic and absorbent material, in the preferred embodiment, in the form of dolomite mixed with non-carbonated carbon material. Primary separator 45 is a non-centrifugal mechanical separator, a separator with V-shaped elements in relation to the boiler in combination with a quick circulation fluidized bed.

 The hot crude gas 2 produced in the gasifier 3 exits directly from the primary separator 45 and is supplied directly to the second gas cleaning zone 25 without additional dust removal. The secondary zone 25 is designed as a quick circulation fluidized bed shaft 26 and contains active shaft material of the same type as in the gasifier 3.

 The crude gas 2 is supplied to the secondary zone, forming a fluidizing gas.

 The secondary zone 25 is designed with a long and narrow rod of a reactor of arbitrary cross-section (for example, round or square). The mine material, which follows the gas stream from the upper part of the reactor core, is mainly separated in a transverse particle separator 27, preferably a separator with V-shaped elements of the same type as the V-shaped gasifier separator, followed by a secondary separator 28, in a preferred embodiment, a cyclone. The material 30, which has undergone separation in the primary particle separator, is recycled to the lower part of the quick circulation shaft 26 through a recirculation device. The material 29, which has been separated in the secondary particle separator 28, is added mainly to the lower part of the gasifier 3 in the form of a stream 31. If necessary, part of the material stream 29 can also be directed to the lower part of the quick circulation shaft 26 in the form of a stream 34 and / or discharged from systems in the form of a stream 43.

 To feed the catalytic and absorbent material 14 into the secondary zone 35, a lateral feed device 15 is used at an appropriate height. The consumed and / or deactivated mine material is discharged using an exhaust device 36 connected to the bottom of the secondary zone 35.

 The active material used in the secondary zone in this example consists of a material containing a double carbonate salt of calcium and magnesium, preferably dolomite, with a particle size of less than 2 mm, preferably less than 1 mm, which in combination with the passing gas forms a shaft 26 fast circulation with fluidizing gas.

 The gas velocity in the upper section of the reactor, calculated from the free cross section, is controlled so that it is below 10 m / s, preferably not above 5 m / s.

 The fluidizing gas of the quick circulation shaft 26 consists of crude gas 2 and added oxidizing gas 13, such as air. If necessary, additional oxidizing gas 33 can be added to the secondary zone 25 at one or more other corresponding higher levels.

Conversion of tar and ammonia contained in the raw gas 2 and sorption chloride contained in the raw gas takes place by contact with the catalytic and absorbing material in the shaft 26 fast circulation within the temperature interval 600-1000 ^{° C,} preferably ^about 700-900 C or most preferably 850-950 ^C. the required temperature level is maintained by burning combustible gas components inside the secondary stage 25, which is regulated by adjusting the amount of added oxidizing gas, streams 13 and 33. The average density of the material in suspension in the reactor core of the secondary zone 25 is maintained within the range of 20-300 kg / m ³ , preferably within the range of 80-250 kg / m ³ so that the necessary contact between the passing gas is achieved and active material. This is achieved by controlling the total amount of circulating material in combination with controlling the flow rate of the recycled material 30 and 34.

 The residence time of the gas in the reactor rod, calculated in the empty reactor rod, is maintained within the range of 0.2-20 s, preferably in the range of 0.5-7 s.

If necessary, activation of the deactivated catalytic and sorbent material can be carried out by adding oxidizing gas 32, for example air, to the material that is recycled to the lower part of the rapid circulation mixture in the form of flows 30 and 34. The amount of added oxidizing gas 32 is regulated so that the activation occurred within the temperature range of 600-1000 ^about With, in the preferred embodiment, within the range of 750-900 ^about C.

 Before the process starts, the secondary zone 25, including the mine material contained therein, is heated by burning liquefied petroleum gas in it.

 The stream 4 of purified gas leaving the secondary separator 28 of the secondary zone 25 is freed from small particles of mine material and steam that have entered it in subsequent gas treatment zones.

Gas passes through two heat exchangers. In the first heat exchanger 37 heat exchange takes place with oxidizing gas, stream 10, intended for both the gasifier 3 and the secondary stage 25, so preheated oxidizing gas 11 at the outlet of the heat exchanger 37 has a suitable temperature, preferably about 400 ° ^C. The preheated oxidizing gas 11 is used both in the gasifier 3 (in particular, as a fluidized gas) in the form of a stream 12, and in the secondary zone 25 in the form of streams 13, 32 and 33.

In the subsequent second heat exchanger 38, the temperature of the gas 5 is reduced to a level that allows the released gas 6 to undergo further purification using, for example, conventional textile filters or a cyclone to further remove dust in the separator 39, that is, in the preferred embodiment, to 150-300 ^about C. The removed dust leaves the dust removal zone.

 As mentioned earlier, gas stream 4 contains small particles of active material that have fallen into it, which follow with a gas stream from secondary separator 28. In special cases, for example, due to gasification of fuel from waste, crude gas 2 from the gasifier contains significant amounts of HCl. Since sorption of Hcl on a lime-containing material such as dolomite helps to lower the temperature, cooling the gas in heat exchangers 37 and 38 helps to increase the degree of sorption of residual Hcl on the material that has entered the gas stream.

Almost dust-free gas 7, which leaves the dust removal zone 39, is supplied to a scrubber 40, in which it is freed from moisture and other water-soluble components. In the scrubber 40, both humidification of the gas stream 7 and vapor condensation occur. Under these conditions, precipitation of almost all residual fines and absorption of water-soluble gas components, such as NH ₃ , HCl and / or NH ₄ Cl, also occur.

Water stream 20 exiting the scrubber is recycled to pump 41, while it is cooled in heat exchanger 42 so that the temperature of the water 19 recycled to the scrubber 40 is kept within the interval 15-20 ° ^C. Excess water 21 descends from the water circuit.

The gas 8 leaving the scrubber can be considered pure for industrial use purposes, i.e. it is almost free from the resin, ammonia, dust, HCl and H ₂ S. However, at a given temperature release) of about 30 ^{° C} it is saturated with steam. Depending on the application, in order to reduce the relative humidity, the gas stream 8 can be preheated or passed through an additional drying step to reduce the moisture content in it. Pure gas meets the requirements for use for engine operation, for example using diesel engines with a turbocharger, and can be burned without subsequent purification of the exhaust gas.

 For applications in simpler cases, for example to generate heat in boilers, the scrubber 40 can be eliminated so that the purified gas is used either directly after the heat exchanger 37 in the form of a stream 22 or after the dust separator 39 in the form of a stream 23.

 In the described example, the secondary zone 25 is combined with a gasifier 3, based on the technology of the quick circulation shaft with a fluidized bed. Gasifier 2 can produce raw gas 2 from several fuels, such as bark, peat or waste fuel. As the shaft material in the quick circulation shaft of the gasifier 3, it is possible to use, as mentioned, the catalytic and absorbent material of the same type as in the second secondary zone 25.

 The total pressure drop of the supplied oxidizing gas, such as air, when passing through the production system is slightly higher than 1 bar. Therefore, it is required to use a compressor 16, which increases the pressure of the oxidizing gas in the stream 9 to the level of pressure in the stream 10, necessary to achieve the goal.

The residual content of tar and ammonia in the purified gas is 500 and 300 mg / m ^3, respectively. If there is hydrogen chloride in the gas being cleaned, its residual concentration after the cleaning process decreases almost to the level of thermodynamic equilibrium.

Claims (6)

1. METHOD FOR CLEANING A CONTAMINATED FUELING GAS obtained from a carbonaceous material during gasification, including treating the gas to be purified in a separate reactor with finely ground calcium carbonate-magnesium, mainly in the form of dolomite, and / or its calcining product in the form of a circulating fluidized bed in the temperature range up to 1000 ^o C when using the cleaned gas as a fluidizing agent, characterized in that, in order to reduce the residual concentration in the combustible gas of the resin in the form of organic compounds d, ammonia and hydrogen chloride in the presence of the latter, cleaning is carried out in a shaft type reactor with an average fluidized bed density of 80 - 250 kg / m ³ at a temperature of at least 600 ^o C.  2. The method according to claim 1, characterized in that the fluidized bed material that has lost activity due to carbon deposition is removed from the reactor and replaced with an equivalent amount of fresh material or activated material by treatment with oxygen-containing gas and / or steam in a separate activation zone or a system for circulating fluidized bed material after separation. 3. The method according to p. 2, characterized in that the said activation is carried out in the temperature range of 600 - 1000 ^o C.  4. The method according to claims 1 to 3, characterized in that the gas velocity in the reactor is maintained at a level below 10 m / s.  5. The method according to claims 1 to 4, characterized in that the residence time of the gas to be purified in the reactor is maintained in the range of 0.2 - 20 s. 6. The method according to PP.1 to 5, characterized in that the gas after the reactor is cooled to 150 - 300 ^o C and dedusted.

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