EA007799B1 - Process for producing metallurgical medium-temperature coke - Google Patents

Abstract

The invention relates to a coal processing technology, in particular to producing metallurgical medium-temperature coke and accompanying combustible gas by thermo-acid coal coking in a dense layer and can be used in metallurgy.The obtained inventive result is that the produced medium-temperature coke has higher strength and density, low ash content and larger average piece size. Besides, the specific coke yield and power effectiveness are increased.The inventive process for producing metallurgical medium-temperature coke comprises a thermal-acid coal coking at 750-900°C in shaft-type installations using the effect of the return heat wave, the coal size 0-70 mm, and the specific air supply is 60-150 m/(mhr) depending on the coal type. The coke is cooled by a forced ventilation by the scheme “installation – heat exchanger” with useful thermal take-off which result in increase of the process power effectiveness.

Description

The invention relates to the field of coal processing, in particular to the production of metallurgical medium-temperature coke and associated combustible gas for use in metallurgy.

A known method of producing medium temperature coke 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 are supplied to the drying and coking zone from an external combustion device, and gas pre-cooled in an external heat exchanger from the coking zone is fed 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, until recently, they operated in Germany and at the Angarsk coke and gas plant (Shkoller MB Semi-coking of hard and brown coals. - Novokuznetsk: Engineering Academy of Russia. Kuzbass. Branch, 2001, 232 s).

The disadvantages of this method are: the ability to process only large-sized (2080 mm) thermally strong raw materials, since it requires the supply of a large amount of external coolant (hot flue gases) and therefore requires good gas permeability of the coal layer; low specific productivity of the furnace associated with the need for prolonged convective heating of large particles of coal with hot gases; environmental hazard of production due to the entry into the atmosphere of a large volume of waste coolant containing carbon monoxide and toxic products of thermal decomposition of coal and due to the presence of a wide range 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.

Closest to the claimed method according to the achieved result and technical essence is a method for 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 (RF patent No. 201483, 06/30/1994, ) The method involves igniting a layer of coal 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, the coal is subsequently subjected to heating, drying, and pyrolysis, thus turning into coke. The vapor-gas 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 750 to 900 ° C. Further along the course of the 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 oxidative 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.

The product obtained according to the known method, despite its close chemical composition to metallurgical coke, high reactivity and high electrical resistivity, has limited use in metallurgy, primarily because of its low structural strength, low density, and relatively small piece size ( maximum - 20 mm, average - 2-5 mm) and increased ash content. The strength of the carbon residue, as well as its density is significantly reduced due to the high porosity. The disadvantage of this method is the reduced specific yield of the solid product due to the high degree of burning of the carbon-containing feedstock.

The objective of the present invention is to obtain a solid product that fully meets the requirements for metallurgical coke, and especially in terms of structural strength, while maintaining high reactivity and electrical resistivity.

The technical result of the invention is to increase the energy efficiency of the process, increase the specific yield of solid product, strength, density and average size of a piece of medium-temperature coke, as well as reduce its ash content by reducing the degree of coke burning.

The technical result is achieved by enlarging the fractional composition of the source coal to 70 mm, reducing the specific air consumption to 60-150 m / (m ² ^ h) depending on the brand of coal, as well as cooling the coke by forced circulation of gas along the circuit of the apparatus - heat exchanger with useful selection of thermal energy.

To achieve a technical result, the method is as follows. Crushed coal of a fraction of 0-70 mm is loaded into the mine apparatus through the loading hatch, air blasting with a specific flow rate of 60 to 150 m ³ / (m ² ^ h) depending on the type of coal 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 supply of blast, in order to form a reverse heat wave, which at a constant speed shifts 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 burn completely in oxygen

- 1 007799 air with the formation of 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) by gas by means of its forced circulation along the apparatus - heat exchanger circuit with a useful selection of thermal energy. Cooled coke is discharged through the hatch located at the bottom of the apparatus.

In examples illustrating the method, a shaft-type apparatus with an inner diameter of 0.5 m and a height of 1.5 m was used.

Example 1

As a raw material used coal fraction 0-70 mm (Shubarkol coal grade D, Kazakhstan), having the following technical and elemental composition:

A '. = 12.2%; C “= 77.9%;

A ⁷ = 2.4%; H “= 5.3%;

Y “= 44%; A ⁷ ''1.2%;

ABOUT'. 25.7 MJ / kg; O “= 15.16%; § “= 0.44%.

170 kg of crushed coal is loaded into the apparatus. The ignition of the layer is carried out from above. Air blast is supplied from below. After the combustion front reaches the lower side of the coal layer, the process ends.

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

The velocity of the combustion front was 13.5 cm / h.

The specific yield of coke is 56 kg / (m ² -h).

The coke yield is 52.2% of the weight of the source coal.

The output of combustible gas is 194 m ³ / (m ² -h).

The specific heat of combustion of the raw gas is 2.8 MJ / m ³ .

Ash content of coke A ⁷ = 5.2%.

The apparent density of coke is 0.695 g / m ³ .

The structural strength of coke is 79%.

The reactivity for CO ₂ at 1000 ° C is 2.76 cm ³ / g-s.

Electrical resistivity - 2.2 Ohm-cm.

Granulometric composition of coke:

more than 40 mm - 21%; 20-40 mm - 28%; 5-20 mm - 44%; less than 5 mm - 7%.

Example 2

As a raw material used coal fraction 0-70 mm (Berezovsky brand B2, Kansk-Achinsk basin), having the following technical and elemental composition:

W = 30%; C “= 71%;

A ⁷ = 5%; H “= 5.0%;

Y “= 48%; N “= 0.7%;

O ', 22.08 MJ / kg; O “= 23%; § “= 0.3%.

120 kg of crushed coal is loaded into the apparatus. The ignition of the layer is carried out from above. Air blast is supplied from below. After the combustion front reaches the lower side of the coal layer, the process ends.

The specific air flow rate is 67.5 m ³ / (m ² -h).

The velocity of the combustion front was 10.5 cm / h.

The specific yield of coke is 36.1 kg / (m ² -h).

The coke yield is 35%.

The output of combustible gas is 114 m ³ / (m ² -h).

The specific heat of combustion of the raw gas is 2.5 MJ / m ³ .

Ash content of coke A ⁷ = 14.2%.

The density of coke is 0.53 t / m ³ .

The structural strength of coke is 64%.

The reactivity for CO ₂ at 1000 ° C is 7.95 cm ³ / g-s.

Electrical resistivity - 1.9-10 ³ Ohm-cm.

Granulometric composition of coke:

more than 40 mm - 6%; 20-40 mm -17%;

5-20 mm - 40%; less than 5 mm - 37%.

Example 3 (comparative).

As raw materials used coal fraction 5-20 mm (Berezovsky brand B2, Kansk-Achinsk basin), having the following technical and elemental composition:

W = 30%; C “= 71%;

A ⁷ = 5%; H “= 5.0%;

Y “= 48%; N “= 0.7%;

0 ^g ₁ = 22.08 MJ / kg; O “= 23%; § “= 0.3%.

- 2 007799

120 kg of crushed coal is loaded into the apparatus. The ignition of the layer is carried out from above. Air blast is supplied from below. After the combustion front reaches the lower side of the coal layer, the process ends.

The specific air flow rate is 115 m ³ / (m ² -h).

The velocity of the combustion front was 9.2 cm / h.

The specific yield of coke is 27.7 kg / (m ² -h).

The coke yield is 27.4%.

The output of combustible gas is 164 m ³ / (m ² -h).

The specific heat of combustion of the raw gas is 2.6 MJ / m ³ .

Ash content of coke A ^a = 21%.

The density of coke is 0.45 t / m ³ .

The structural strength of coke is 46%.

Granulometric composition of coke:

5-20 mm - 19%; less than 5 mm - 81%.

Thus, the proposed method allows to obtain coke having a higher strength and density, lower ash content, a larger average size of the piece and a higher specific yield of solid product (see table).

Claims (1)

CLAIM A method for producing metallurgical medium temperature coke in a shaft-type apparatus, including thermal-oxidative treatment of coal in a reverse heat wave with a temperature of 750900 ° С, characterized in that coal of a fraction of 0-70 mm is used with a specific air flow rate of 60-150 m ³ / (m ² -h ) depending on the type of coal, the coke is cooled (dry quenched) by gas by means of its forced circulation around the circuit, the apparatus — a heat exchanger with a useful selection of thermal energy.