RU2543194C1 - Brown coal gasification method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: brown coal with the moisture content of 20-53% up to the fraction size of 2-3 mm and then delivered to two-stage vortex drying by the intake of a part of a generator gas from a gas-generator plant with a temperature of 960°C with O₂ unavailable in it. Dried coal is mixed with water to receive a coal-water slurry, which is subject to fine grinding, thereafter it is diluted by water up to the ratio of L:S=2:3, and gasification is made by the delivery of air at a pressure of 0.1-0.11 MPa at a temperature of 850-1100°C. The quantity of blown air (α) is equal to 0.25-0.35 of stoichiometric quantity (α=1), required for the complete oxidation of carbon, hydrogen and sulphur contained in dry ash-free basis of the gasified brown coal.

EFFECT: invention allows improving the efficiency factor and the production output of the gasification process and exclusion of the explosive risk.

1 dwg

Description

Technical field

The invention relates to methods for producing combustible gases from solid carbon-containing fuels, and in particular to methods for gasifying lump and granular fuels, and can find application in the fuel and chemical industries, as well as in the power system.

State of the art

The prior art various methods for the gasification of carbon-containing fuel. In particular, there is a known method for producing gas from peat, disclosed in patent RU 2185418, published on July 20, 2002, which involves heating peat and then supplying steam-air or steam-oxygen blast to the heating zone until the temperature reaches 180-220 ° C, and heating is carried out in the presence of palladium catalyst.

The disadvantage of this method is the use of an expensive catalyst, the use of steam-air blast, which reduces the heat of combustion of the gas, or the use of special oxygen blast.

Also known is a method of burning crushed coal according to patent RU 2078283, published on 04/27/1997, in which the combustion is carried out by preliminary stepwise gasification in the fluidized bed and afterburning of the obtained gas in the boiler furnace as a result of separate and sequential gas generation, afterburning and cooling operations in the fluidized bed and introducing gasification and afterburning products into the boiler furnace.

Among the disadvantages of this method, it is possible to distinguish such as the limited possibility of gasification due to significant entrainment with increasing speed on the surface of the fluidized bed, which limits the performance of the gas generator, because exceeding the gas velocity of more than 3-4 m / s leads to an exponential increase in the consumption of entrained particles and the average size of entrained particles. As a result, the largest of them do not have time to burn out in the boiler furnace and form a mechanical underburn, reducing the boiler efficiency.

Closest to the claimed invention is a method of heat treatment of organic carbon materials disclosed in patent RU 1085509, published 04/07/1984, which includes mixing the source material with a liquid, transporting the mixture from bottom to top through a layer of liquid with an adjustable level, supplying wet material to the reaction zone , its processing at elevated pressure and temperature to produce gases and a solid product, the removal of the resulting gases and solid product, while the wet material before feeding the reaction zone is preheated by passing through it a countercurrent of gases obtained in the reaction zone.

The disadvantage of this method is the use of elevated pressure, elevated temperature and the need to heat the material before being fed into the reaction zone, which makes gasification more expensive and does not exclude its fire hazard.

Disclosure of invention

The technical result to which the claimed invention is directed is to increase the efficiency and productivity of the gasification process while eliminating its explosion hazard, increasing the calorific value of gas, as well as providing the possibility of efficient use of industrial waste as additives in other industries, for example, in the construction industry, the manufacture of building materials.

The specified technical result is achieved due to the fact that in the gasification method brown coal with a moisture content of 20-53% is pre-crushed to a particle size of 2-3 mm, then at least two-stage vortex drying is carried out by taking part of the generator gas from a gas generator with a temperature of 960 ° C in the absence of O ₂ in it, after which the dried coal is mixed with water to obtain a water-coal suspension with a ratio of W: T = 0.5: 1, which first undergoes an operation of fine grinding of the coal contained in it to a particle size of it is less than 10 microns, after which the water-carbon suspension is diluted with water to W: T = 2: 3 and then the gas-carbon suspension is gasified by supplying air at a pressure of 0.1-0.11 MPa at a gasification temperature of 850-1100 ° C, while the amount of blast air (α) is 0.25-0.35 of the stoichiometric amount (α = 1) required for the complete oxidation of carbon, hydrogen and sulfur contained in the dry ashless mass of gasified brown coal.

Studies conducted by various authors on the selection of the optimal ratio of water and coal for coal-water fuel (HLF) showed that when burning HLW and its gasification it is necessary to strive to optimize the ratio of solid to liquid to ratios of at least 60:40.

The use of a water-coal suspension (WCS) with coal contained in it, crushed to a particle size of less than 10 microns, can increase the efficiency of gasification of the fuel-containing components of the mixture and significantly increase the productivity of the gas generation process. In addition, similar WCS are stratified at a significantly lower rate.

Brown coal is the most widespread type of low-grade coal in Russia (as well as abroad), well developed in the Kansk-Achinsk and other brown coal basins and deposits located from the European part to Sakhalin. Among them, the Kansk-Achinsk basin is the largest, providing production of more than 50 million tons of coal per year. Brown coals have a relatively low ash content - most often up to 20%, but they are usually very humid - with humidity up to 40-50%. At present, Kansk-Achinsk coals have been industrially developed to produce semi-coke using appropriate gas generators, but, unfortunately, this semi-coke is not in commercial demand. At the same time, brown coals of any grades can be easily gasified with the release of combustible generator gases. Therefore, in this study, the use of flooded brown coal is provided as one of the main types of widely available low-grade coal fuel.

In this case, in order to obtain an aqueous suspension of brown coal with a ratio of W: T≥6: 4, it is necessary to provide for the preliminary drainage of brown coal and their two-stage grinding - first up to 2 mm, and then to micron sizes.

The claimed method of gasification necessarily provides for the selection of brown coals for a detailed analysis of the chemical and mineralogical composition of their mineral part, which will provide a real forecast of the possibilities of using the ash and slag output of the gasification process for suitability for one or another technical use. So, if the mineral part contains CaO less than 10%, then fly ash and ground slag can be added to cement in an amount up to 20-25% without reducing the grade of cement, i.e. every 1.20-1.25 kg of the resulting mixture can be sold at the price of pure cement. But if you exceed this limit of additives, then we get a decrease in the grade of cement and, consequently, a decrease in its price, which can also be beneficial especially in cases where we do not need a high grade of concrete.

When gasification of coal-rich coal slurry, it is necessary to provide increased safety at the stage of vortex drying of coal at a temperature of 150-720 ° C, which is achieved by supplying a gas coolant with an oxygen content of less than 1%. The existing gasification technologies for WCS use a gas coolant obtained by burning coal in a special furnace device with an air excess ratio of 1.1-1.5.

In the claimed gasification method, it is proposed to provide vortex drying of brown coal by taking part of the generator gas from a gas generator with a temperature of 960 ° C at O ₂ = 0. As a result of this, the temperature of the generator gas heating the vortex drying decreases to 550-600 ° C, and then this part of the generator gas is mixed with its main stream used to implement the operation of mini-TPPs or mini-TPPs, which increases the efficiency of the method due to the following advantages:

a) there is no need for a separate furnace for vortex drying;

b) in the drying unit, a zero oxygen content is provided, which completely eliminates the explosion hazard.

Thus, the method of gasification of brown coal of all grades (from B1 to B3) is based on the use of a water-coal suspension, which simplifies heating of coal during vortex drying of brown coal to obtain drying products with a moisture content of 2-3%, necessary to obtain a WCS with an optimum solid content ( not less than 60%) - due to the receipt of the heat carrier available on the general technological scheme instead of a separate furnace heating device for products by burning used brown coal. In practice, a part of the obtained gas-generating gas with a temperature of 960 ° C is used here, with its subsequent return after exiting the vortex drying, into a mixture with the main quantity of the product of generation - gaseous fuel to generate electricity and heat.

Brief Description of the Drawings

The invention is illustrated in the drawing, where figure 1 shows the General technological scheme for the gasification of water-carbon suspension obtained from flooded brown coal with two-stage grinding.

The implementation of the invention

The method of gasification of brown coal is as follows.

Brown coal with moisture content W ^r = 20-53% is pre-crushed to a particle size of 2-3 mm in commercially available drum crushers. The crushed coal is then fed to vortex drying, which is carried out by taking part of the generator gas from a gas generator with a temperature of 960 ° C in the absence of O ₂ . Vortex drying is carried out in two or three stages in the vortex chambers, for example, the design of IGI - CJSC Kompomash - TEK to ensure coal moisture W ^r = 2-3%. In the process of drying coal to W ^r = 2-3%. its bertination occurs, accompanied by a certain decrease in the oxygen content and an increase of 15-17% in the calorific value (calculated on its dry ashless mass).

After that, the dried coal is mixed with water to obtain a water-coal suspension (WC) with a ratio of W: T = 0.5: 1. The obtained WCS is sent for fine grinding of the coal contained in it in a cavitation-vibration apparatus, for example, of the design of ZAO Kompomash-TEK, to a particle size of less than 10 microns. From the fine grinding apparatus, the obtained WCS is sent to a container with a stirrer, where it is diluted with water to W: T = 2: 3 and transferred to a gas generator

Gasification of a coal-water suspension is carried out by supplying air at a pressure of 0.1-0.11 MPa. The gasification temperature is 960 ° C. The water contained in the WCS evaporates and, therefore, vapor-air gasification is carried out. The amount of blast air (α) is 0.25-0.35 (depending on the type of gasified fuel) of the stoichiometric amount (α = 1) required for the complete oxidation of carbon, hydrogen and sulfur minus oxygen contained in the dry ashless mass of gasified fuel.

Gaseous products (generator gas), together with solid particles, which are a mixture of mineral substances formed from the mineral components of the initial fuel, and the "underburning" of coke-like particles, consisting mainly of carbon, are sent to commercially available boilers to produce heat (steam and hot water ) and electricity.

Gaseous products cooled in the boiler to 150-200 ° C are cleaned of solid particles in multicyclones or an electrostatic precipitator and are released into the atmosphere. The trapped particles, together with the solid particles collected during the periodic cleaning of the gas generator and heat transfer surfaces of the boiler, are called ash and slag waste (ASW)

Disposal of ash and slag wastes is carried out in various directions, depending on their composition and local conditions. One of the most ambitious areas of their use, associated with the lowest capital costs, is as a partial replacement for earthen soil and sand - the use in the construction of artificial earthen structures (dams, embankments, foundations of buildings, etc.) and roads. It is also possible to mix (10-20 wt.%) With cement without changing its brand, as well as as a raw material for the production of various building materials (mortars, bricks, porous aggregates for concrete, etc.)

Claims (1)

The method of gasification of brown coal, characterized in that brown coal with a moisture content of 20-53% is pre-crushed to a particle size of 2-3 mm, then at least two-stage vortex drying is carried out by taking part of the generator gas from a gas generator with a temperature of 960 ° C in the absence of in it ₂ O, then dried coal is mixed with water to produce a coal-water slurry with a ratio of W: T = 0.5: 1, which first passes the operation fine grinding coal contained in it to a particle size less than 10 micrometers, whereupon a single-angle suspension is diluted with water to W: T = 2: 3 and then the water-coal suspension is gasified by supplying air at a pressure of 0.1-0.11 MPa at a gasification temperature of 850-1100 ° C, while the amount of blown air (α) is 0.25-0.35 of the stoichiometric amount (α = 1) required for the complete oxidation of carbon, hydrogen and sulfur contained in the dry ashless mass of gasified brown coal.

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