RU2725319C2 - Method of producing carbon dioxide for production of calcined soda by ammonia method - Google Patents

Abstract

FIELD: inorganic chemistry; environmental protection.SUBSTANCE: invention can be used in large-tonnage production of soda ash by ammonia method. Flue gases of enterprises, including thermal power stations, containing 7–14 vol. % of carbon dioxide can be mixed with carbon dioxide obtained by treatment of calcium-containing raw material with hydrochloric acid with content of not less than 95 vol. %. Content of COafter mixing is not less than 45 vol. %. Concentration is then carried out in an apparatus with regenerative blocks at temperature of 45 °C by absorbing 34–42 % aqueous solutions of absorbents, in form of mixtures of diethanolbenzylamine and monoethanol amine or ethylene diamine and monoethanol ethylene diamine. Carbon dioxide obtained in regenerative blocks containing not less than 50 vol. % COis subjected to drying at 145 °C or mixed with carbon dioxide containing 35–38 vol. % CO, obtained during limestone burning. Obtaining carbon dioxide with content of COof not less than 40–44 vol. % corresponding to norms for soda production.EFFECT: invention enables to recycle flue gas from enterprises, including thermal power stations.1 cl, 5 dwg

Description

The invention relates to the field of production of carbon dioxide (CO ₂ ) used in soda production.

Currently, the traditional method for producing carbon dioxide in Russia is the method of E. Solve (patent 1861) from ammonia, sodium chloride, carbon dioxide. According to this method, carbon dioxide and lime are obtained by calcining carbonate raw materials (limestone), extracted from stones (Shikhanov) quarry Shakhtau. By the way, the reserves of limestone in the Shakhtau quarry will be enough until 2020. In the future, the problem of providing soda production with raw materials - carbon dioxide remains unresolved. The ammonia method by which soda ash is obtained in Sterlitamak (Republic of Bashkortostan) by the method of Ernest Solve (Belgian chemist and entrepreneur) has already existed for the 72nd year. Also, the Solve method is distinguished by a large proportion of waste - 10-12 m ³ (more than 10-12 tons) of the so-called distillate liquid (J) are formed per 1 soda ash waste is 10 times more than soda ash produced. In the USA, soda (Na ₂ CO ₃ ) is produced from natural soda (Na ₂ CO ₃ -NaHCO ₃ -2H ₂ O) and nachcolite (NaHCO ₃ ) and dausonite MaAl (OH) ₂ CO ₃ . Soda sources are also available in other countries - in Belgium, Turkey, Brazil, China, Canada and South Africa.

A known method of separating liquid carbon dioxide from technological and energy gases by absorption of CO _{2 with an} aqueous solution of monoethanolamine (MEA), followed by compression of carbon dioxide [T.F. Pimenova. Production and use of dry ice, liquid and gaseous carbon dioxide. M .: light and food industry, 1982].

The known process for the emission of carbon dioxide from flue gases includes the following stages:

1) cooling of flue gases in a water scrubber;

2) the extraction of carbon dioxide from flue gases by its absorption with an aqueous MEA solution at a temperature of 40-50 ° C;

3) regeneration of the circulating MEA solution at 110-130 ° C and a pressure of 0.17-0.2 MPa with desorption of CO ₂ from the absorbent solution;

4) liquefaction of CO ₂ by compression in a mechanical compressor with further cooling. In industrial installations, the liquefaction of CO ₂ obtained from flue gases usually uses compression of gaseous carbon dioxide to a pressure of 7.1 MPa (71 kg / cm ³ ) in a 4-stage piston compressor with further cooling of the product to 15-20 ° C or compression in a 2-stage compressor to a pressure of 1.5 MPa with cooling to a temperature of minus 30 ° C.

The disadvantage of these processes is the high cost of electricity for the compression of CO ₂ before liquefaction and significant losses of MEA due to entrainment from the regenerator.

The closest in combination of features is a method of purification of gases from carbon dioxide by absorption with an aqueous solution of amines followed by regeneration of the absorbent at a pressure of 0.5-9.5 MPa. This method uses a single-stage absorption-desorption scheme of CO _{2 with an} aqueous solution of one absorbent - MEA, which at high temperatures (129-160 ° C) of pressure regeneration undergoes increased degradation [A.S. 512785 USSR / Leites I.L., Murzin V.I. and other publ. 05/05/76. Bull. No. 17].

It is known that with an increase in temperature for every 10 ° С, the rate of MEA degradation increases 1.6-1.8 times, which leads to an increase in absorbent losses. Moreover, the vapor pressure of the MEA at these temperatures is high, which significantly increases the physical loss of the MEA due to entrainment from the regenerator. Of course, the consumption coefficient of the absorbent increases sharply in the process of carbon dioxide emission.

The problem to which the invention is directed is to develop a method for producing carbon dioxide used in the production of soda ash from flue gases of thermal power plants (CHP), bringing the CO ₂ content to the required standards for soda production. The technical result when using the invention is expressed in the development of a combined method for producing carbon dioxide from flue gases of a thermal power plant, followed by concentration by absorption with amino alcohols, amines and mixing with highly concentrated CO ₂ (more than 90-95%) obtained at the plant [see Pat. 2547105 RF / Zagidullin R.N. and other publ. 04/10/2015 Bull. No. 10].

The above technical result is achieved by the method of producing carbon dioxide with a content of at least 38-42% vol. (such a CO ₂ content is required for soda production) by concentrating the flue gases of a thermal power plant at a temperature of 45 ° C, where the CO ₂ content is 7-14% vol. first in regenerative blocks using a mixture of diethanolbenzylamine (DEBA) and monoethanolamine (MEA) or monoethanol ethylene diamine (MEEDA) and ethylene diamine (EDA) as CO ₂ absorbents.

Natural gas (methane) is fed into the nozzle of the gas turbine unit 1 for combustion with the estimated amount of air, taking into account its complete combustion. In this case, the formation of thermal energy (about 8,200 kcal / mol hail) is supplied to boiler 2, where the pipes are heated. Through these pipes, due to the heat exchanger 3, heat is removed to consumers. Waste gases (CO ₂ , СО, nitrogen oxides) - the products of fuel combustion are carried away into the pipe of the thermal power station and are currently discharged into the atmosphere. The supply of flue gases containing 7-14% vol. carbon dioxide to the installation (Fig. 2) to extract and concentrate it using absorbents in the absorption and desorption system (CO ₂ regeneration). Mixing of 7-14% vol. flue gas carbon dioxide obtained by the reaction of calcium-containing raw materials with hydrochloric acid (see US Pat. No. 2547105. Publ. 10.04.2015 Bull. No. 10; Pat. No. 2291109 Publ. 10.01.2007. Bull. No. 1).

Description of a plant with regenerative units for the extraction and conversion of carbon dioxide from flue gases using absorbents.

Flue gases containing 7-14% vol. carbon dioxide enter the cooling and washing unit of gas 5 (Fig. 2) and the apparatus (Fig. 3) and pass each stage 16 through the working hydrodynamic zones 20 in the pipe 21.

The flue gases in the pipe 21 are saturated with a circulating agent entering through the inlet pipes 22 into the working hydrodynamic zone, where a gas-liquid mixture is formed, which is intensively mixed in a turbulent mode.

Gases are cooled and washed with the release of dust particles and harmful gas impurities from the nozzle 21. The cooled and washed gas passes through a separator 23 with the separation of gases from the dusty liquid agent.

Next, the gases through terminal 16 are sent to the absorption unit 6 (Fig. 2), and the spent agent is returned to the collector 25 (Fig. 4, Fig. 4 shows a two-stage apparatus) and again with a fresh agent continues to circulate in a closed cycle using a circulation pump 26 from the collection 25 through the apparatus (Fig. 4).

In block 6, like block 5, the gases in the apparatus (Fig. 4) are treated with an agent, for example, monoethanolamine (MEA), monoethanol ethylene diamine (MEDA), which absorb carbon dioxide.

The apparatuses of FIG. 3 and FIG. 4 are presented for a better understanding of the process.

Exempted from carbon dioxide, the exhaust gases by the blower 11 (Fig. 2) are either emitted in the case of large volumes (these are gases and dust-free particles free from harmful impurities) or are used, for example, for heating coolants.

Saturated carbon dioxide absorbent from block 6 is sent to the closed cycle 7 of the circulation of the absorbent solution through the evaporator 8, the heat exchanger - 9 (Fig. 2), the collector - 25 with a circulation pump 26. (Fig. 4).

In the evaporator 8, carbon dioxide is desorbed from the absorbent due to steam heating at a temperature of 145 ° C, which is sent to block 10 (Fig. 2).

In a closed cycle 7, in the heat exchanger 9, part of the heat from the evaporator 8 is regenerated to preheat the circulating absorbent saturated with carbon dioxide.

In block 10, carbon dioxide is dried and cleaned with KMnO ₄ circulating from the collector 12 by a centrifugal pump 13 in a closed cycle. Carbon dioxide in the block 10 circulates in a closed cycle in the gas pipeline through the apparatus (Fig. 4) by a gas blower 11 with simultaneous regulation of the output of a part of the volume of the finished product, for example, for compression.

In the reactor 27 (Fig. 5), limestone or calcium-containing secondary raw materials 37 (calcium-containing waste, sludge, etc.) containing 94% CaCO ₃ are fed from above.

In the lower part of the reactor, hydrochloric acid (inhibited hydrochloric acid 38 and hydrochloric acid 39) is dosed (dosed supply of hydrochloric acid or hydrogen chloride). To obtain more concentrated CaCl ₂ solutions, a supply of gaseous hydrogen chloride 40 is provided. A CaCl ₂ solution containing H ₂ O, a small amount of HCl and a small amount of CO ₂ 42 is fed into reactor 28 (reactor-neutralizer) filled with CaCO ₃ or limestone flour 43. the reactor 28 is the neutralization of residual HCl by reaction

CaCO ₃ + 2 HCl = CaCl ₂ + CO ₂ + H ₂ O.

The result of this reaction is the formation of an additional amount of calcium chloride and, accordingly, CO ₂ . Insoluble precipitate 41 is discharged from the bottom of the reactor to a collection vessel 29.

To obtain CaCl ₂ , hydrochloric acid is used according to STP 6-01-08-105-96 “hydrochloric acid from the exhaust gases of organochlorine production” 31.5% (premium), 30.0% (first grade), 27.5% (second grade), concentrated hydrochloric acid with a concentration of 36-37%, as well as gas and technical acid with a concentration below 27.5%.

After the reactor 28, a solution of calcium chloride 46 is fed into the collector 30, after the collector, a solution of calcium chloride 45 is fed to the evaporation and drying.

To obtain granules of solid calcium chloride - after evaporation and drying - served in the granulator.

Carbon dioxide released in the process from reactors 27 and 28 is sent via line 44 to a sanitary column 31 filled with limestone or limestone flour 43 and a solution of CaCl ₂ (26-28% concentration) in a weight ratio of CaCO ₃ : CaCl ₂ equal to 2-4: 1.

The resulting CaCl ₂ solution with traces of hydrochloric acid and carbon dioxide 42 from the bottom of the column 31 is fed into the tank 32. A portion of the CaCl ₂ solution from the tank 32 is pumped to the sanitary column 31 or to the reactor 28 by the pump 33.

The container 32 is provided with CaCl ₂ solution 46. The purified carbon dioxide 47 is passed through a droplet eliminator 34. Carbon dioxide can be used in the production of sodium carbonate 49 or chalk 50. There is a discharge of excess CO ₂ into the atmosphere 48.

Claims (2)

1. The method of producing carbon dioxide for soda production by the ammonia method by burning calcium-containing raw materials, including calcium carbonate, characterized in that the flue gases of enterprises, including TPPs containing 7-14 vol.% Carbon dioxide, are concentrated on a plant with regenerative blocks at a temperature of 45 ° C by absorption with 34-42% aqueous solutions of absorbents, which are used as a mixture of diethanolbenzylamine and monoethanolamine or ethylene diamine and monoethanol ethylene diamine, followed by drying of the obtained carbon dioxide at 145 ° C or carbon dioxide with a content of at least 50 vol.%, Obtained in regenerative blocks, mixed with carbon dioxide with a content of 35-38 vol.% obtained by calcining limestone, to obtain carbon dioxide with a content of at least 40-44 vol.%. 2. The method according to p. 1, characterized in that the flue gases after the CHP, containing 7-14 vol.% Carbon dioxide, are mixed with carbon dioxide obtained by processing calcium-containing raw materials with hydrochloric acid with a content of at least 95 vol.% To obtain dioxide carbon after mixing with a content of at least 45 vol. %

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