SU816958A1 - Method of thermal treatment of coal for producing activated coal - Google Patents

Description

The invention relates to chemical technologies, in particular, to methods for the thermal treatment of coal and can be used for the carbonization of raw coal in the manufacture of industrial activated carbons. The known method of heat treatment (activation) of the coal in the moving bed is 800-1000 ° C in contact with the vapor-gas coolant supplied by the coil 1 when air is supplied to the furnace 11. The disadvantage of this method is the low process efficiency limited by the maximum permissible flow rate of the vapor-gas mixture limited by the vapor-gas velocity the flow above which coal is carried away from the working zone of the furnace to the gas channels. In addition, the productivity of the process is limited by the maximum permissible amount of air supplied to the furnace, since, when the content of free oxygen in the working zone exceeds a certain limit, coal is burned. It is closest to the proposed heat treatment of coal by moving the moving layer through the wall to 500 ° C and contact with para-gas coolant supplied by the countercurrent f2. The disadvantage of this method is the low intensity of the process, which is limited by external temperature heating of gases, heating the walls of the retort and relatively low thermal conductivity of both the wall and the material being processed, and during internal heating the maximum permissible gas flow rate, which should not exceed the critical fluidization rate. due to possible coal ablation from the working area of the furnace; in addition, in the upper part of the retort, water and resin products of heat treatment are condensed the cold carbon, which leads to its agglomeration, worsening its expiration and heat, resulting in furnace productivity is drastically reduced, decreases product yield and coal is obtained insufficiently high strength. The purpose of the invention is to increase the strength, yield of carbonized coal and the productivity of the process. The goal is achieved by the fact that in the method involving the heating of a moving bed of coal through the wall before and contact with the steam-gas coolant, in the interval of 20-300s, the vapor-gas coolant is fed by the flow, in the interval of 500-1200 ° C, the electric current is passed through the heat layer and use a coolant with a content of 0.2-10% by volume of free oxygen. Additionally, in the interval 300l200 c, the vapor-gas coolant is supplied countercurrently. The heat treatment process of coal is divided mainly into three stages for each of which, to obtain a product of a given quality and increase the heat exchange intensity, it is necessary to heat the material in a different environment with a different method of heat supply depending on the material properties at this stage of processing. So, the first stage precedes the onset of destructive processes, the final temperature of this stage usually does not exceed. This stage is endothermic, since here it is mainly the removal of moisture, the transition of the material into a plastic state (for thermoplastic materials) and, therefore, an intensive supply of heat is necessary. At the same time, water vapor resinous substances are released in this range of heat treatment, capable of condensing during cooling, which contributes to agglomeration, freezing and coking of the product and furnace flue gas ducts. At this stage, the heat treatment of the material is carried out simultaneously by external heating through the wall and internal heating by direct contact of the coal with a stream of gas coolant supplied by the stream. This eliminates vapor condensation and increases the intensity of the process. At the 2nd stage (300-50 s), the processes of destruction and synthesis proceed in parallel, connected with the breaking of weak oxygen-hydrogen, oxygen-carbon, carbon-hydrogen bonds and the formation of stronger aromatic carbon-carbon bonds. Depending on the ratio, processes of destruction and synthesis, both the release and the absorption of energy occur, the amount of which substantially depends on the material being processed and the specific temperature in a given interval. In this case, at this stage of heat treatment, to obtain a product of a given quality, both the treatment medium and the rate of heat supply must be strictly controlled. At this stage, resinous substances are also released that can condense when cooled. This stage of heat treatment according to the proposed method is conducted by external heating through the wall and countercurrent flow of heat transfer fluid. This prevents condensation of precipitated gummy products in view of the fact that gaseous products move from the cooler layer to the hotter one adjacent to the wall, and then are removed through the hole in the wall. Thus, the process is carried out in a reducing environment of gaseous pyrolysis products with a given heating rate, which is regulated by the wall temperature and the material moving speed. At the 3rd stage (500-1200 ° C) the carbon-containing material (coal) becomes Electrically conductive and its structure is mainly formed, and the properties of the final product depend little on the rate of temperature rise. According to the proposed method, the heating of the material at this stage is carried out by passing through the layer of electrolyte material and at the same time an upward flow of the vapor-gas coolant containing, at the inlet, 2-10% by volume of free oxygen. At the same time, the penetration of a layer of material by a gas-vapor mixture containing oxygen, combined with the transmission of electric current, ensures the maximum intensity of the process leading to a HIGH furnace performance, heating and producing water gas uniformly over the entire layer of material due to interaction at a temperature above 700 ° C. and carbon dioxide with carbon. From the high-temperature zone, a vapor-gas mixture containing products of the interaction of oxygen with gaseous heat-treating products, as well as combustible components such as hydrogen, methane, carbon monoxide and others, are used partly to heat the material in the low-temperature and partly medium-temperature zone. Intensification of the first and third stages of heat treatment significantly increases the productivity of the process as a whole. The choice of the combined-cycle heat carrier with the content of free oxygen O, 2-10 vol.% Is due to the fact that free oxygen reacts noticeably with combustible components only when its content in the steam-gas mixture is more than 0.2%. Therefore, the introduction of less than 0.2% free oxygen into the coolant is ineffective. When the content of free oxygen in the supplied gas-vapor mixture is more than 10%, the gaseous heat treatment products with oxygen are completely reacted in the coolant supply zone, after which excess oxygen reacts with coal. As a result, the surface overhang of the material occurs, the macroporosity of the coal grows, and atoms in turn reduce the strength and yield of the product. FIG. 1 shows schematically the construction of a vertical shaft furnace with two product channels implementing this method in FIG. 2 shows section A-A in FIG. 1. The furnace includes a low-temperature heating zone 1, a medium-temperature heating zone 2, a high-temperature heating zone 3 and a cooling zone 4, hoppers 5 for loading material i / food channels, slit holes b for feeding a vapor-gas heat carrier to penetrate the layer of material from above through gas channels 7, slit-like holes 8 for removing gaseous heat treatment products through gas channels 9, electrodes 10 for supplying electric current to a layer of material, pipe 11 with holes for supplying vapor-gas heat an oxygen-containing sieve sieve, unloading device 12 of the scraper type, discharge hopper 13, gas ducts 14 for removing from the furnace a mixture of low-temperature and medium temperature zones, channels 15 for supplying air for combustion. In the gas channels of the middle temperature zone of gaseous products, channels 16 for mixing a part of gases of high-temperature zones and steam from pipes 17, shut-off valves 18 for adjusting the degree of dilution of gases from a high temperature zone supplied to permeation of a layer of material in low temperature zones , Manifolds 19, gas ducts 20 for supplying part of the gas to the high-temperature zone collective frame 19, dampers 21 for adjusting the distribution of the gas stream from the high temperature zone to the headers 19 of the pipe 22 for supplying steam for cooling the heat-treated product. To remove gaseous products from the furnace, the ducts 14 are connected to the exhaust fan 23 through the heat recovery tank 24. The product channels of the low-temperature and medium temperature zones expand downwards. They are separated by gas channels and have in cross section, for example, the form of an elongated rectangle, ellis, circle. In the high-temperature zone, the productive channels are separated by an intermediate electrode, and in the cooling zone they are combined into one common channel. Example 1. Raw coal AF-3 in the amount of 1 and O kg / h is loaded into a laboratory furnace (Fig. 1 and 2) with volumes of zones 1, 2, 3 and 4, respectively, equal to 70, 90, 45 and 65 dm. Charcoal characteristics the following,%: content in Lagi5 Ash content5 Volatile yield .30 Fractional composition: 1 mm 1% 1-2.75 mmilu% 2.75-5.5 mm $ 88% 5 mm61% From pipes 17 to channels 16 are fed 20 kg / h water vapor 140 ° C. In channels 14, a discharge pressure of 80 Pa is set. A voltage of 60 V is applied to the electrodes. A current of 200 A is passed through a layer of coal. Through pipes 11. 25 nm of a gas-vapor mixture of 800 ° C is fed and the content, vol. %: free oxygen 5; € 0.10 NdO 17 N 68. 50 kg / h of water vapor 120s is fed through pipe 22. In zone 1, coal is heated to through the wall and in contact with the vapor-gas coolant (mixture of gases from zone 3 and water vapor from pipes 17) supplied by the flow. In zone 2, heating is conducted to 500 :: :: through the wall and contact with the vapor-gas coolant supplied by the countercurrent from zone 3. At the same time, the coolant is enriched with volatile substances separated from coal in zone 2. In zone 3, heating is carried out to 1200 ° C by passing electric current and contact with the upward flow of the vapor – gas coolant containing 5 vol.% free oxygen at the entrance to the zone. In zone 4, the coal is cooled to 150 ° C with steam, 61 kg / h of carbonized coal is discharged into the hopper 13. Heating of coal is carried out in the range of 20-300С with a speed of 10 K / min., In the range of 300-500 ° С - 6 K / min, in the range of 500-1200 ° С - 25 K / min. The carbonized carbon is cooled at a rate of 20 deg / min. In zone 4, water vapor, cooling coal, as it rises, heats up and at a temperature of 700 ° C, it partially interacts with coal to form water gas. In zone 3, the vapor-gas coolant containing products of the interaction of oxygen with gaseous heat treatment products as well as combustible components moves countercurrently upwards and, giving off heat to the coal, is cooled to 500 seconds. At the outlet from zone 3, the coolant contains, vol.% Sah6,5; SB 28 Na41; N, 16, CH 1,5) N / p 7. In the upper part of zone 3, the vapor-gas coolant is divided into two streams, one of which in an amount of 50 is sent to zone 1 through ducts 20, and the rest to zone 2. Distribution of expenses heat carrier is regulated by gates 21. In gas ducts 20, temperature is heat. The carrier is adjusted to 800 ° C due to partial combustion of combustible components. Then the coolant is injected with water vapor supplied from the pipes 17 to the channels 7, from where the vapor-gas mixture through the holes 6 is fed by the flow into the moving slab coal. Here the vapor-gas stream is enriched with Sarami nBmi water and resinous impurities, extracted from coal. The vapor-gas mixture from zone 1 is removed through channels 14.

In zone 2, the coolant from zone 3 enriched in volatile substances extracted from coal is removed through openings 8 to gas channels 9, where part of the bitter components are burned. The average temperature in the channels 9 is set equal to 750s.

In the channels 14, the vapor-gas flows from zones 1 and 2 are mixed and removed by means of a diesel generator 23 through the waste heat boiler 24 to the atmosphere. 450 nm gases and with a calorific value of 2800 kcal / nm are removed from the furnace. In the waste heat boiler, physical and chemical heat is removed from the furnace gases to produce steam and hot water. . .

  Pr and me r p 2. In contrast to example 1, the content of free

oxygen in the vapor-gas mixture supplied; in the area 3 through the pipe 11, set 0.2% vol. At the same time, 92 kg / h of raw coal is loaded into the furnace, and 59 kg / h are discharged from the caobonized coal.

Froze In contrast to examples 1 and 2, the free oxygen content in the gas-vapor mixture given in zone 3 through pipes 11 is set to 10 vol.% At the same time, 107 kg / h of raw coal is loaded into the furnace, and 63 kg / h of carbonized coal are unloaded.

Table 1 shows the indicators of carbonized AP-3 carbon obtained by the proposed method, and data on the process productivity and product yield for examples in comparison with the known method.

The quality of the carbonized coal produced by the proposed method is significantly higher, since its strength and bulk density have higher values, and the total porosity is lower. In addition, the carbonized carbon yield and process productivity are significantly increased.

Table 1

Offered:

197

2.98

393

For comparison, the carbonized carbon AP-3 obtained by the proposed method in example 1 and the carbon obtained by a known method activated up to 30% of the degree of activation (adopted in industry680 0.26 100 61 61 690 0.25 92 59 64 660 0.29 107 63 58

AP-3 type active carbons in a laborg. torus rotary kiln with water vapor.

Table 2 shows the performance of the resulting active carbons. .

Offered91 0.70 0,, 37 0.19 54 ems 80 0.75 0.502 0.28 0.14 41

Claims (2)

The known adsorbent based on carbonized carbon according to the proposed method has much greater strength and adsorption capacity, which significantly improves the technical and economic indicators of the processes where these active carbons are used. Thus, the proposed method provides an increase in the productivity of the process by an average of 30% yield of carbonized coal by 10% of the strength of coal (according to GOST 16188-70) by 10%. However, this method significantly reduces emissions of harmful substances into the atmosphere and improves working conditions. 1. The method of heat treatment of carbon to obtain activated carbon, including the heating of the moving layer. That coal and 2 coal through the wall before and contact with the steam-gas coolant, characterized in that, in order to increase the strength, yield of carbon coal and process performance, in the range of 20-300 ° C, the steam-gas heat carrier serves 1. in the interval 5001200 G, heating is conducted by passing an electric current through the layer and using a vapor-gas heat carrier with a content of 0.2-10% by volume of free oxygen. 2. The method according to .P.1, O.t l and h a y i and and the fact that in the range of 300-1200 With the vapor-gas coolant serves countercurrent. Sources of information taken into account in the examination 1. The author's certificate of the USSR 389013, cl. From 01 to 31/08, 1971. 2. The UK patent number 745150, kl.v 55 (1) A, 1956 (prototype). sj K.i V a / a. If ..., -. .Vrr .v-i .-: -: -.; -; -; . -one - .- :-. . ; 7 --- - - -..--. -Y-- Yas-y-r -.- DG -; - 7 -.-- “- -: -.- a- - ; :: SrxW: N. ; -№K - .. “., - ,. xtt .. - .-: /.- .. / and .. / J S2 br 7J - Aa 17 19