RU2722557C2 - Coal processing method - Google Patents

Abstract

FIELD: coal processing.

SUBSTANCE: invention relates to production of coke and combustible gas. Method consists in thermo-oxidative treatment of coal of 0–70 mm in reverse thermal wave, wherein temperature in oxidation zone is maintained from 905 °C to 1100 °C and air flow through the layer of coal is carried out with a specific consumption of 155 to 300 m³/(m²·h) depending on coal grade and required characteristics of coke, then obtained coke is cooled.

EFFECT: technical result is reduction of residual output of volatile substances in coke residue, increased specific heat of combustible gas combustion, increased specific capacity of device by gas and coke.

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Description

The invention relates to the field of coal processing, in particular, to the production of coke products and combustible gas for use in metallurgy and other industries.

A known method of producing semicoke in a vertical shaft furnace, in which coal is fed from above, and coke is discharged from below. The furnace is divided by transfer sleeves into three zones: the upper drying zone, the middle coking (pyrolysis) zone and the lower cooling zone. Hot flue gases from an external combustion device are supplied to the drying and coking zone, and gas pre-cooled in an external heat exchanger from the coking zone is supplied to the cooling zone. Coal, moving by gravity from top to bottom, is subsequently subjected to heating, thermal decomposition (coking), cooling and is quenched with water when unloading from the furnace.

Such furnaces are operated in Poland, Australia, China, and Russia at the Leninsk-Kuznetsk semi-coking plant (Shkoller MB Semi-coking of hard and brown coals. - Novokuznetsk: Engineering Academy of Russia. Kuzbass. Branch, 2001. - 232 p.).

The disadvantages of this method include the ability to process only large-sized (20-80 mm) thermally strong raw materials, requiring the supply of a large amount of external coolant (hot flue gases) and good gas permeability of the coal layer; low specific furnace productivity, associated with the need for prolonged convective heating of large particles of coal with hot gases; the environmental hazard of production due to the release into the atmosphere of the spent coolant containing carbon monoxide and toxic products of thermal decomposition of coal, and due to the presence of toxic substances in liquid and gaseous coking products and wastewater; the need for water for quenching coke, high humidity and reduced structural strength of the resulting product due to its wet quenching.

A known method of producing a carbon adsorbent in a vertical shaft-type apparatus with internal heating by burning volatiles and part of the carbon residue in a coal layer blown by an air stream. The ignition of the coal layer in the method is carried out from the side opposite to the air supply, as a result of which, with certain parameters of the blast, a reverse heat wave is generated, which is shifted towards the air flow. When a heat wave passes through a layer, coal is subsequently subjected to heating, drying, and pyrolysis, thus turning into coke. The gas-vapor mixture of drying and pyrolysis products, as well as part of the coke, react with the oxygen of the air until it is completely exhausted, forming a narrow combustion zone, within which the temperature is reached from 600 to 900 ° C. Further along the movement, hot combustion products (CO ₂ and H ₂ O) are reduced on coke to carbon monoxide and hydrogen. Combustible gas is removed from the apparatus for subsequent processing and use. The carbon residue formed after thermal oxidation treatment is classified as medium temperature coke. When processing coal according to the known method, the resulting product has a large porosity (over 60%) and a developed inner surface, which ensures its high sorption activity and subsequent use mainly as a carbon adsorbent. (RF patent No. 201483, publ. 1994).

A known method of producing metallurgical medium-temperature coke in a mine-type apparatus, which consists in heat treatment of a coal layer of a fraction of 20-70 mm when fired from the side opposite to the air supply, with a specific air flow rate of 70-99.5 m ³ / (m ² ⋅ hour), depending on the brand of coal, followed by cooling. (RF patent No. 2275407, publ. 2006)

The disadvantage of this method is the low productivity of coke due to the low speed of the front of the return heat wave.

Closest to the claimed method according to the achieved result and technical essence is a method of producing metallurgical medium-temperature coke in a vertical shaft-type apparatus with internal heating by burning volatiles and part of the carbon residue in a coal layer blown by an air stream (Patent RU 2288937, publ. 2006, )

The method includes ignition of a coal layer of a fraction of 0-70 mm from the side opposite to the air supply, as a result of which, at certain blast parameters - from 60 to 150 m ³ / (m ² ⋅ h) - a reverse heat wave is generated, which is shifted towards the air flow. When a heat wave passes through a layer, coal is subsequently subjected to heating, drying, and pyrolysis, thus turning into coke. The gas-vapor mixture of drying and pyrolysis products, as well as part of the coke, react with the oxygen of the air until it is completely exhausted, forming a narrow oxidation zone within the heat wave, in which the temperature is reached from 750 ° C to 900 ° C. Further, in the direction of travel, hot combustion products (CO ₂ and H ₂ O) are reduced on coke to carbon monoxide and hydrogen (CO and H ₂ ), which are combustible. The resulting combustible gas is removed from the apparatus for subsequent use as an energy carrier without preliminary purification, since it does not contain tarry substances, and the content of solid particles in flue gases when it is burned is lower than current environmental standards. When processing coal according to the known method, the resulting coke product has a developed inner surface and high adsorption activity, as well as high reactivity and high electrical resistivity, which allows it to be used as a carbon reducing agent in various metallurgical processes and as a sorbent for environmental and technological purposes.

The disadvantages of this method are the relatively high residual yield of volatiles in the coke residue, which narrows the scope of its application in metallurgy and other industries, low specific heat of combustion of combustible gas, low specific productivity of the apparatus for gas and coke.

The problem to which the present invention is directed, is to obtain a coke product with improved quality while maintaining high adsorption activity, reactivity and electrical resistivity, improving the thermal characteristics of combustible gas, as well as increasing the productivity of the apparatus.

The technical result of the invention is to reduce the residual yield of volatiles in the coke residue, increase the specific heat of combustion of combustible gas, increase the specific productivity of the apparatus for gas and coke.

The technical result is achieved due to the fact that the thermal oxidative treatment of coal of class 0-70 mm is carried out in a reverse heat wave while maintaining the temperature in the oxidation zone from 905 ° C to 1100 ° C and air supply with a specific flow rate of 155 to 300 m ³ / (m ² ⋅h) depending on the brand of coal and the required characteristics of coke.

The invention consists in the following.

Crushed coal of 0-70 mm fraction is loaded into the mine apparatus through the loading hatch, air blasting with a specific flow rate of 150 to 300 m ³ / (m ² ⋅h) is fed under the gas distribution grill at the bottom of the mine and the coal layer is ignited from the side opposite to the blast supply, in order to form a reverse thermal wave, which moves at a constant speed towards the air flow, leaving behind a layer of hot coke. Coal during the passage of a heat wave is sequentially subjected to heating, drying and pyrolysis. Combustible pyrolysis products are completely burnt in atmospheric oxygen to form carbon dioxide and water vapor, which are then reduced on the hot surface of the coke to carbon monoxide and hydrogen, thus forming a combustible gas that does not contain hydrocarbons of a series above methane, including condensable resinous substances . After the heat wave reaches the gas distribution grid level, the process ends. Upon completion of the coking process, coke is cooled (dry quenched), after which the cooled coke is discharged through a hatch located at the bottom of the apparatus.

The invention is illustrated by the following examples.

In examples illustrating the method, a lined shaft apparatus with an inner diameter of 0.3 m and a height of 1.5 m is used.

Example 1

As the feedstock, grade D coal is used, class 0-70 mm, Taldinskaya-Zapadnaya mine (Kemerovo region), having the following technical and elemental composition: W ^r _t = 12.7%; A ^d = 8.8%; V ^daf = 39.8%; C ^daf = 78.7%; O ^daf = 13.5%; H ^daf = 5.25%; N ^daf = 1.98%; S ^d _t = 0.52%; Q ^r _i = 24.1 MJ / kg.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 155 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 905 ° C.

The coke yield is 47.3% of the weight of the source coal.

The specific calorific value of coke is 28.6 MJ / kg.

The specific productivity of the apparatus for coke is 38.8 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is 215.4 m ³ / (m ² ⋅ h).

The specific heat of combustion of the combustible gas is 2.86 MJ / m ³ .

The residual yield of volatiles in coke is 4.1%.

The electrical resistivity of coke in the class 3-6 mm is 16.8 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 2.24 cm ³ / (g⋅s).

Example 2

As the starting raw material, grade D coal of 0-70 mm grade is used in Taldinskaya-Zapadnaya mine (Kemerovo region), having the technical and elemental composition as in Example 1.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 195 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 1010 ° C.

The coke yield is 40% by weight of the source coal.

The specific calorific value of coke is 29.1 MJ / kg.

The specific productivity of the apparatus for coke is 39.1 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is 247 m ³ / (m ² ⋅ h).

The specific heat of combustion of the combustible gas is 4.12 MJ / m ³ .

The residual yield of volatiles in coke is 2.5%.

The electrical resistivity of coke in the class of 3-6 mm is 13.1 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 1.88 cm ³ / (g⋅s).

Example 3 (comparative)

As the starting raw material, grade D coal of 0-70 mm grade is used in Taldinskaya-Zapadnaya mine (Kemerovo region), having the technical and elemental composition as in Example 1.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 120 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 810 ° C.

The coke yield is 49% by weight of the source coal.

The specific heat of combustion of coke is 27.6 MJ / kg.

The specific productivity of the apparatus for coke is 33.6 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is 184 m ³ / (m ² ⋅ h).

The specific heat of combustion of the combustible gas is 2.59 MJ / m ³ .

The residual yield of volatiles in coke is 5.4%.

The electrical resistivity of coke in the 3-6 mm class is 19.7 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 2.39 cm ³ / (g⋅s).

Example 4

As the feedstock used coal grade 3B class 0-30 mm section "Bolshesyrsky" (Krasnoyarsk Territory), having the following technical and elemental composition: W ^r _t = 23.5%; A ^d = 4.4%; V ^daf = 45.2%; C ^daf = 75.3%; O ^daf = 18.7%; H ^daf = 5.0%; N ^daf = 0.87%; S ^d _t = 0.17%; Q ^r _i = 20.5 MJ / kg.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 210 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 910 ° C.

The coke yield is 29.7% by weight of the source coal.

The specific heat of combustion of coke is 28.9 MJ / kg.

The specific productivity of the apparatus for coke is 34.2 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is 293 m ³ / (m ² ⋅ h).

The specific heat of combustion of combustible gas is 3.7 MJ / m ³ .

The residual yield of volatiles in coke is 5.8%.

Iodine adsorption activity - 60.3%.

The electrical resistivity of coke in the class of 3-6 mm is 280 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 2.24 cm ³ / (g⋅s).

Example 5

As the feedstock used coal grade 3B class 0-30 mm section "Bolshesyrsky" (Krasnoyarsk Territory), having the technical and elemental composition is the same as in example 4.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 300 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 1100 ° C.

The coke yield is 27.3% by weight of the source coal.

The specific calorific value of coke is 28.8 MJ / kg.

The specific productivity of the apparatus for coke is 36.1 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is 326 m ³ / (m ² ⋅ h).

The specific heat of combustion of the combustible gas is 3.6 MJ / m ³ .

The residual yield of volatiles in coke is 2.8%.

Iodine adsorption activity - 55.9%.

The electrical resistivity of coke in the 3-6 mm class is 116.0 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 5.75 cm ³ / (g⋅s).

Example 6 (comparative)

As the feedstock used coal grade 3B class 0-30 mm section "Bolshesyrsky" (Krasnoyarsk Territory), having the technical and elemental composition is the same as in example 4.

60 kg of coal are loaded into the apparatus. The ignition of the coal layer is carried out from above. Air blast is served from below. After the combustion front reaches the lower side of the coal layer, the supply of blast air is stopped and the process ends. The resulting coke is cooled and discharged from the apparatus.

The specific air flow rate is 143 m ³ / (m ² ⋅ h).

The temperature in the oxidation zone is 850 ° C.

The coke yield is 33.4% of the weight of the source coal.

The specific calorific value of coke is 27.7 MJ / kg.

The specific productivity of the apparatus for coke is 32.2 kg / (m ² ⋅ h).

The specific gas productivity of the apparatus is -186 m ³ / (m ² ⋅ h).

The specific heat of combustion of the combustible gas is 3.18 MJ / m ³ .

The residual yield of volatiles in coke is 7.2%.

Iodine adsorption activity - 41.2%.

The electrical resistivity of coke in the 3-6 mm class is 335 Ohm⋅cm.

The reactivity for CO ₂ at 1000 ° C is 6.41 cm ³ / (g⋅s).

The data obtained are presented in the table.

As follows from the data presented, the method according to the invention allows to obtain a coke product with high quality by reducing the residual yield of volatiles in it, to increase the specific heat of combustion of combustible gas, as well as the specific productivity of the apparatus for gas and coke.

Claims (1)

A method of processing coal to produce coke and combustible gas in a mine-type apparatus, comprising thermo-oxidizing treatment of coal of 0-70 mm class in a reverse heat wave with subsequent cooling of coke, characterized in that the temperature in the oxidation zone is maintained from 905 ° C to 1100 ° C and air supply through the coal layer is carried out with a specific flow rate from 155 m ³ / (m ² ⋅ h) to 300 m ³ / (m ² ⋅ h) depending on the type of coal and the required characteristics of coke.