EA007798B1 - Method of laminar coal gasification - Google Patents

Abstract

The invention relates to producing power-generating or process gas from coal destined for use in power generating and chemical industries.The method of laminar coal gasifying is carried out in a vertical shaft-type apparatus with air blasting from bottom and firing of coal layer from atop and has two stages, at the first stage 150-600 m(m2 x hr) of air blasting is fed, followed by the second stage where up to 100 kg/(mx hr) of water vapour is added, wherein the method provides simultaneous use of at least four apparatuses operating with equal process phase displacement.

Description

The invention relates to the field of production of energy or process gas from coal and can be used in the energy and chemical industries.

There are a number of methods for the layered gasification of coal using air and vapor-air blast. For example, in the process of ^ e11tap-O1i8Ja (Schilling, G.-D. Coal Gasification / G.-D. Schilling, B. Born, W. Kraus. - M .: Nedra, 1986. - 175 p.) Previously set on fire from below coal filling in the mine-type apparatus is blown by the vapor-air mixture from bottom to top.

The main disadvantage of this method is that the resulting gas is saturated with the products of coal pyrolysis and contains up to 0.1 kg of resin per 1 nm ^{3 of} gas. This gas has limited use. Approximately every 3-4 months, cleaning of pipelines from condensate and tar deposits is required, which prevents long-term continuous operation of equipment. Cooling the gas and washing it from resinous substances significantly increases capital and operating costs and reduces the efficiency of the gasification process.

The closest to the claimed method on the achieved result is a method for producing semi-coke and associated gas (RF patent No. 2169166, 10.06.2001), which is a type of layer gasification of coal. The method involves purging the bed of coal with a mixture of air and combustible gas (approximately 8-10% of the volume obtained in a vertical shaft-type apparatus). The blast is fed from the opposite side of the coal ignition with a specific flow rate of 100-400 m ³ / (m ² хч) so that the temperature of the coal in the carbonation front is 920-950 ° C. The products of coal pyrolysis, which are formed in the carbonation front, burn in the air flow, forming mainly carbon dioxide and water vapor.

Further, these gases are reduced to carbon monoxide and hydrogen on the heated surface of the semi-coke. Thus, the resulting gas does not contain condensable products of pyrolysis of coal and can be used in further processing without intermediate stages of cooling and washing from the resin.

The disadvantage of this method, from the point of view of the production of gas that does not contain condensable products of pyrolysis of coal, is incomplete gasification of the carbon-containing part of coal. Approximately 5060% of the organic part of the coal is converted to gas, and the remainder is output as semi-coke. The relatively low temperature in the carbonation front (up to 920-950 ° C) limits the rate of endothermic reactions of carbon with carbon dioxide and water vapor, therefore the volume content of carbon monoxide and hydrogen in the gas does not exceed 33%, and its specific heat of combustion is 600-900 kcal / nm ³ , which limits the scope of application of such gas as an energy carrier.

The closest to the claimed method according to the technical nature is two-stage gasification of a moving layer of solid fuel in a mine-type gas generator (Fedoseev, SD Semi-coking and gasification of solid fuel / SD Fedoseev. - M .: Gostoptekhizdat, 1960. -326 с) . In the gas generator, horizontal blowing of the upper part of the fuel layer by the gas coolant obtained by burning a part of the product gas is carried out. The semi-coke formed as a result of pyrolysis is moved to the lower part of the shaft, where it is subjected to full gasification by the vapor-air mixture. The gas flows after the first and second stages are mixed and fed to the stage of cooling and purification from tar.

The disadvantage of this method is that the resulting gas contains pyrolysis products.

The objective of the present invention is to obtain a gas that does not contain condensable pyrolysis products, expanding the scope of use of gas, improving efficiency and efficiency.

The technical result of the invention is to increase the specific heat of combustion of a gas that does not contain condensable pyrolysis products, under the condition of complete gasification of the organic mass of the original coal.

The technical result is achieved due to the two-stage layered gasification of coal in a vertical shaft-type apparatus, including the first stage — heating, drying, carbonization of the original coal and partial gasification of carbon and the second stage — complete gasification of carbon contained in the coke residue. In the first stage, the supply of air blast in the amount of 150-600 m ³ / (m ² hh) is carried out from the side opposite to the ignition of the layer, in the second stage (after the reaction front reaches the side of the layer of coal opposite to the ignition), water is added to the blow to 100 kg / (m ² хч), necessary to maintain the temperature in the gasification front not higher than 1100-1200 ° С (the limiting is ash softening temperature).

To achieve a technical result, the method is as follows. Crushed coal of class 5-50 mm is loaded into a vertical shaft-type apparatus at full height, air blast is fed with a specific flow rate from 150 to 600 m ³ / (m ² hh) and the coal layer is ignited from the side opposite to the blast feed. The resulting reaction front at a constant speed shifts towards the air flow, and a layer of hot coke residue remains behind the front. Coal when passing through the front of the reaction is sequentially subjected to heating, drying and pyrolysis. The combustible components of the pyrolysis products are completely oxidized by atmospheric oxygen to form carbon dioxide and water vapor, and then, by reducing the coke residue on the hot surface, they are converted into combustible gas components (carbon monoxide and hydrogen) that does not contain condensable

- 1 007798 pyrolysis products. In this case, the temperature at the front of the reaction reaches 1000-1200 ° C, and the specific heat of combustion of the gas is 1000-1200 kcal / nm ³ .

After the front of the layer reaches the opposite side of the ignition, water vapor is added to the blast in an amount of up to 100 kg / (m ² hch) and full vapor-oxygen gasification of the carbon contained in the coke residue is carried out, and the gasification front moves in the direction of the primary ignition layer. The resulting combustible gas does not contain condensable products of pyrolysis of coal, and the specific heat of combustion of the gas is 1000-1200 kcal / nm ³ . The amount of water vapor in the blast is chosen so that the temperature in the gasification front does not exceed the softening temperature of the ash for a given coal (1100-1200 ° С).

After the end of the process, slag is unloaded from the lower side of the vertical apparatus.

To equalize the composition of the product of combustible gas and the specific productivity of gas, it is preferable to simultaneously use at least four devices operating with equal shifts in the phase of the process.

In the examples illustrating the method, a vertical shaft-type apparatus with an internal diameter of 0.5 m and a height of 1.5 m was used. The raw material used was coal of a fraction of 5-20 mm of grade B2 (Berezovsky cut, Kansk-Achinsk coal basin) The following technical and elemental composition:

A '. = 33.5%; And ³ = 5.0%; A ^{3: 3} = 48%; ABOUT'. 3800 kcal / kg;

C ^3aH = 71.7%; Η == 4.9%; \ ³ ' ^{: 3} 0.8%; O ^3aH = 22.3%;

8 ^3aH = 0.3%.

Example 1

Air supply - 46 nm ³ / h.

The steam supply in the second stage is 12 kg / h.

The temperature in the response zone is 1100-1150 ° C.

Gas composition (vol.%): CO = 13.8; H ₂ = 15.6; CO ₂ = 16,0;

CH ₄ = 2.4; Ν ₂ = 46.5; H ₂ O = 5.92.

Specific heat of gas combustion 0 / = 1026 kcal / nm ³ .

The carbon content in the solid residue is 1.9%.

Example 2 (comparative).

Air supply - 21 nm ³ / h.

The temperature in the response zone is 900–930 ° C.

The composition of the gas (vol.%): CO = 8.5; H = 12.5; CO2 = 17.5;

CH ₄ = 2.9; Ν ₂ = 51.6; H ₂ O = 7.0.

Specific heat of gas combustion 0 / = 795 kcal / nm ³ .

The carbon content in the solid residue is 81.5%.

Thus, the proposed method allows for complete gasification of the organic mass of the original coal and to obtain a gas that has an increased specific heat of combustion and does not contain condensable pyrolysis products.

Claims (2)

1. The method of layer-by-layer gasification of coal in a mine-type apparatus by supplying air blast from below and igniting a layer of coal from above, characterized in that the process is carried out in two stages, the first of which is supplied with air blast in an amount of 150-600 m ³ / (m ² hh ), and on the second - up to 100 kg / (m ² hh) water vapor is added to the blast. 2. The method according to claim 1, characterized in that it provides for the simultaneous use of at least four devices with equal shifts in the phase of the process.