RU2169166C1 - Method of preparing semicoke - Google Patents

Abstract

FIELD: metallurgical industry. SUBSTANCE: method comprises heating, drying and carbonizing solid hydrocarbon feedstock using air blasting to which combustible gas is added. Combustible gas has temperature from apparatus outlet at concentration that does not exceed lower limit of gas inflammation. Amount of gas added is preferably 8-10% from volume of the resulting combustible gas. Carbonization temperature varies from 920 to 950 C. EFFECT: improved quality of semicoke by about 5 or 6 % and shorter feedstock treatment time. 4 cl, 2 ex

Description

 The invention relates to methods for producing semicoke with the simultaneous production of associated combustible gas for the metallurgical industry.

 A known method of processing solid carbon-containing raw materials (brown coal) using a gaseous coolant with a supply of water vapor, including heating, coking and cooling. The gases circulating at each of the respective stages are flue gases generated during coking (US Pat. No. 4,231,844, November 4, 1980).

 Closest to the claimed method according to the technical essence and the technical result achieved is a method for producing semi-coke from carbon-containing lumpy or briquetted raw materials, which is a variation of the method of gasification of solid fuel. The method involves the formation of backfill of the original lump of raw materials in a vertical autothermal apparatus of a mine type. As you move from top to bottom, the raw materials are sequentially heated, dried and carbonized, and then partially activated. Unloading of the finished semicoke is made at the lower level of the vertical chamber. Raw materials are added to the chamber from above to maintain a constant level of backfill.

 Air blast moves from top to bottom through the backfill and, sequentially reacting with the oxidation of gaseous products of pyrolysis, and then reducing during activation, turns into low-calorific combustible gas, which is taken at a distance equal to about 1.5 times the diameter of the backfill from its upper level. The gas is subjected to multi-stage purification, cooling and compression before being supplied to the consumer (US patent N 4883499, 11/28/89).

A disadvantage of the known method for producing semicoke is the increased content of residual volatile substances in the final product, due to the relatively low temperature in the carbonization front (not more than 850-870 ^o C), which reduces the quality of semicoke as a product intended for introduction into metallurgical melts.

 In the known method, the regulation of the maximum temperature in the carbonization front is provided only by changing the flow rate of blast air. At the same time, with an increase in air flow rate and a corresponding increase in temperature in the front, the burning of semicoke increases (ash content increases) and the specific yield of products decreases.

 The objective of the present invention is to improve the quality of semicoke (reducing the residual yield of volatiles while maintaining a minimum ash content of the product) and the performance of the process for its preparation.

 The problem is solved by the method of producing semi-coke by processing solid carbon-containing raw materials in a vertical shaft-type autothermal apparatus using air blasting, which includes the stages of heating, drying and carbonization of the raw materials, unloading the resulting semi-coke from below and the selection of combustible gas, in which according to the invention food fuel is added to the air blast gas having an outlet temperature from the apparatus in a concentration not exceeding the lower ignition limit of the gas.

Preferably, about 8-10% of the volume of the resulting combustible gas is added to the air blast, the carbonization temperature is 920-950 ^° C, the air blast is fed from the opposite side of the coal ignition with a specific flow rate of 100-400 m ³ / m ² • h.

 The method is as follows.

Coal is loaded into a vertical apparatus. After filling, an air blast is fed to the full height, and the coal layer is ignited from the opposite side air supply. With a specific air supply of 100-400 m ³ / m ² • h, the combustion front is shifted towards the air flow, and behind the combustion front there is a solid residue - semi-coke. When the combustion front moves through the layer, coal sequentially passes through the stages of heating, drying, and carbonization. Carbonization products containing, inter alia, combustible components such as carbon monoxide, hydrogen, liquid and gaseous hydrocarbons, together with solid carbon react with atmospheric oxygen to form a combustion front, the temperature of which reaches 750-900 ^o C and in which all oxygen reacts air. Behind the combustion front there is a reduction zone in which combustion products (carbon dioxide and water vapor) are converted into combustible components of associated gas by reduction on a carbon surface. To ensure an elevated temperature in the front of carbonization of coal and to prevent burnout of part of the resulting semicoke, part of the product combustible gas is mixed with air blast (about 8-10% of the volume of gas produced). In this case, the concentration of combustible gas in the blast does not reach the lower limit of ignition. The supply to the combustion front of an additional amount of combustible gas raises the temperature to 920-950 ^o C, providing a deeper carbonization of coal without burning part of the finished semi-coke.

In examples illustrating the method, a vertical shaft apparatus with a diameter of 0.5 m and a height of 1.5 m was used. Coal of fraction 5-20 mm of grade B2 (Berezovsky open pit of the Kansk-Achinsk coal basin) was used as raw material, having the following technical and elemental composition:
W _t ^r = 33.3%
A ^d = 5.0%
V ^daf = 48%
Q _i ^r = 3800 kcal / kg
C ^daf = 71.7%
H ^daf = 4.9%
N ^daf = 0.8%
O ^daf = 22.3%
S ^daf = 0.3%
Example 1
In the above apparatus, 206 kg of coal are charged. Bottom air blowing at a flow rate of 25 m ³ / h (128 m ³ / m ² • h) is supplied, and coal is ignited from above. After 10 hours, the front of carbonization of coal reaches the level of air supply and the apparatus is unloaded. The yield of semicoke was 63.8 kg or 31% of the initial coal. Its parameters are as follows:
W ^a = 2.0%
A ^d = 11.3%
V ^daf = 8.5%
C ^daf = 92.2%
H ^daf = 1.7%
S ^d = 0.13%
N ^daf = 0.3%
O ^daf = 5.65%
The gas output was 42.5 m ³ / h, and caloric content 795 kcal / m ³ , no resin, ablation less than 1 g / m ³ . The maximum temperature in the moving front of carbonization is 780 ^o C.

Example 2
The method is carried out in similar conditions to example 1.

206 kg of coal are also loaded into a vertical reactor. Bottom air blowing at a flow rate of 25 m ³ / h (128 m ³ / m ² • h) is supplied, and coal is ignited from above. In order to increase the temperature in the carbonization zone, in addition to the blast, 4.5 m ³ / h of gas with a calorific value of 770 kcal / m ³ , taken at the outlet of the reactor at a temperature not lower than 300 ^o C., is supplied. After 8.9 hours, the carbon carbonization front reaches the level supply of blast and the device is unloaded. The yield of semicoke was 67.7 kg or 32.8% of the initial coal. Its parameters are as follows:
W ^a = 1.7%
A ^d = 11.6%
V ^daf = 4.4%
C ^daf = 96.1%
H ^daf = 1.1%
S ^d = 0.12%
N ^daf = 0.2%
O ^daf = 2.5%
The gas outlet after sampling was 46 m ³ / h, and the calorific value was 770 kcal / m ³ , there was no resin, the entrainment was less than 1 g / m ³ . The maximum temperature in the moving front of carbonization 920 ^o C.

As can be seen from the examples presented, due to the selection of part of the gas and mixing it with the blast, it is achieved
1) improving the quality of semi-coke by reducing the yield of volatiles in the product;
2) the yield of the product increases (by about 5-6%);
3) reduced time for processing coal in the apparatus by increasing the speed of movement of the carbonization front.

Claims (4)

 1. A method of producing semi-coke by processing solid carbon-containing raw materials in a vertical shaft-type autothermal apparatus using air blasting, which includes the stages of heating, drying and carbonization of the raw materials, unloading the resulting semi-coke from below and selection of combustible gas, characterized in that product combustible gas is added to the air blast having a temperature of exit from the apparatus, in a concentration not exceeding the lower limit of ignition of the gas.  2. The method according to p. 1, characterized in that about 8-10% of the volume of the resulting combustible gas is added to the air blast. 3. The method according to PP.1 and 2, characterized in that the carbonization temperature is 920-950 ^o C. 4. The method according to claims 1 to 3, characterized in that the air blast is fed from the opposite side of the coal ignition with a specific flow rate of 100-400 m ³ / m ² • h.