RU2553116C1 - Method of metallurgical coke production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes heating, baking and calcination of the carbon containing charge in the movable flow. Charge in the movable flow is heated upon oxygen presence in the heating zone of the rotating tube-time furnace with temperature in range 200-500°C, and baking and calcination of the carbon containing charge are performed in the baking and calcinations zone of the rotating tube-type furnace with temperature in range 600-1500°C. The carbon containing charge containing 50-100 wt % of petroleum semi-coke with output of volatile substance from 14 to 25 wt % is used, it is produced by decelerated semicoking of heavy petroleum residues.

EFFECT: enhanced coke quality.

4 cl, 1 dwg, 6 tbl, 3 ex

Description

The invention relates to oil refining technology and can be used to produce metallurgical coke.

A known method of producing petroleum coke in delayed coking plants by heating the feedstock in a tubular furnace followed by coking in a reactor (USSR Author's Certificate No. 199312), according to which coking is carried out in the presence of a vaporous coolant with a coke number of not more than 3%, heated to a temperature of at least 500 ° C.

The disadvantage of the known solution for the USSR AS No. 1993312 is the need to use an additional heat source - a vaporous coolant and a reactor in which coking is carried out, which complicates the method and increases the cost of its implementation.

There is a method of continuous calcination of petroleum coke with a high content of volatile and coke breeze in rotary tube furnaces (USSR Author's Certificate No. 239206), according to which coke is heated in direct-flow furnaces, first to the temperature of volatile emissions by burning fuel, and then lead calcination by burning volatiles released from coke.

The disadvantage of the known decision on the USSR AS No. 239206 is its limited functionality, since it is intended only for calcination of petroleum coke

A known method of producing petroleum coke (USSR author's certificate No. 507614), comprising preheating the feedstock to 380-400 ° C, fractioning it into light fractions and bottoms, heating the bottoms in a tube furnace in the presence of water vapor to 475-510 ° C and coking. In this case, after heating the bottom residue, vapor-gas products are separated from it, and the remaining liquid part is sent to coking.

A disadvantage of the known solution for the USSR AS No. 507614 is its complexity, due to the peculiarity of the feedstock for coking, namely: they use directly the oil residue. In this case, it is first necessary to carry out fractionation of the heated feedstock into light fractions and bottoms. Then, the separated bottoms are heated in a tubular furnace in the presence of water vapor, and steam and gas products must be separated from the heated bottoms before coking.

The methods for producing petroleum coke according to the USSR copyright certificate No. 1169977 and USSR copyright certificate No. 1279997 have similar disadvantages.

The known method for the continuous production of coke and a coking device according to the patent of the Russian Federation No. 2144555 (selected as the closest analogue to the prototype). Known for the patent of the Russian Federation No. 2144555, a method for continuously producing coke from coal includes the following stages: preparing at least one elongated coking chamber with a channel formed by the outer wall of the small pipe and the inner wall of the large pipe; forced supply of coal to the loading end of the coking chamber and its compaction by pressing against the outer wall of the small pipe and the inner wall of the large pipe and continuous coking of coal and turning it into coke in the absence of oxygen by heating a mass of coal forcibly moved in the coking chamber channel, which is heated by heat conduction on both sides during movement through a elongated coking chamber, in which coking of coal begins at the walls of both pipes and is accompanied by separation of the moving ma sy coal substantially in the middle of the channel.

The disadvantage of the method according to the patent of the Russian Federation No. 2144555, selected as the closest analogue, is its complexity, due to the need to use equipment made specifically for the implementation of the proposed method, namely: the need to use a special complex furnace design.

The technical result achieved by the claimed invention is to simplify the method of producing metallurgical coke from petroleum feedstock and improve its quality.

The claimed technical result is achieved due to the fact that in the method for producing metallurgical coke, which includes heating, sintering and calcining a carbon-containing mixture in a moving stream, according to the invention, the carbon-containing mixture is heated in a moving stream in the presence of oxygen in a heating zone of a rotary tube furnace with a temperature in the range of 200 -500 ° C, and sintering and calcination of a carbon-containing mixture is carried out in the sintering and calcining zone of a rotary tube furnace with a temperature in the range of 600-1500 ° C, and using comfort carbon-containing mixture with a content of 50-100 wt.% petroleum coke with a yield of volatiles from 14 to 25 wt.%, obtained by delayed semi-coking of heavy oil residues.

The mixture is heated at the associated, countercurrent or mixed movement of the mixture and gas.

Exhaust gases are used to heat the air entering the tube furnace.

The resulting coke is cooled with water and / or steam.

The inventive method can be carried out on a rotary tube furnace of any design.

Rotary kiln (tube furnace, drum furnace) is an industrial cylindrical furnace with rotational movement around the longitudinal axis, designed to heat bulk materials with the aim of their physicochemical processing. Rotary kilns distinguish: by the principle of heat exchange - with countercurrent flow and with a parallel flow of gases and material; by the method of energy transfer - with direct, indirect (through the wall of the muffle) and combined heating of the processed material. According to their purpose, there are distinguished rotary kilns for sintering charges in the production of alumina, obtaining cement clinker, oxidizing, reducing, chlorinating roasting, calcining aluminum hydroxide, coke, carbonates, sulfates, etc., dehydrating materials, extracting zinc and lead (Waelz kiln), obtaining iron or non-ferrous metal alloys by their direct reduction from ores in the solid phase (flash furnaces), firing of refractory raw materials, etc. The main ones are rotary kilns in which pulverized, solid, liquid or gas is burned heat of fuel directly into the working space of the furnace and the heating gases are moved towards the material being worked. A metal drum lined with refractory bricks is installed at a slight angle to the horizon on the support rollers. In some cases, the diameter of the drum is made variable in length. The drum is driven into rotation (1-2 rpm) by an electric motor through a gearbox and an open gear transmission. The mixture is loaded from the side of the head. The dry charge is fed by mechanical feeders, and the charge in the form of pulp is fed in bulk or through nozzles. Fuel (10-30% by weight of the charge) is introduced through burners (nozzles) placed in a hot head. Here, the finished product is sent to the refrigerator. Gases from a rotary kiln are cleaned from dust (sublimates) in the system. To improve the conditions of heat transfer in a rotary kiln, various heat-exchange devices are built in - scraper blades, shelves, chain curtains, nozzles, etc. For the same purpose, in some cases, the lining of furnaces is carried out with a complex shape, for example, cell. The main dimensions of the rotary kiln vary significantly: length from 50 to 230 m, and diameter from 3 to 7.5 m. The productivity of the rotary kiln reaches 150 t / h (finished product). There is a tendency to connect a rotary kiln with various heat exchangers, which makes it possible to reduce their size with an increase in the technical and economic indicators of the operation of furnaces (Great Soviet Encyclopedia).

Thus, it is customary to call tubular rotary kilns continuous technological units with a working space in the form of a hollow cylinder, in which, due to the slight inclination (~ 3 °) of the kiln and rotation, the processed bulk materials move along the kiln, being heated due to the heat released during fuel combustion. In a structural respect, they differ from each other only in the size of the housing and the device systems for loading and unloading material. The name of the furnace usually reflects its purpose. Tube furnaces are widespread in the oil refining and petrochemical industries, they are an integral part of many plants and are used in various technological processes, such as distillation of oil, fuel oil, catalytic cracking and reforming, hydrotreating, oil refining, etc.

According to the claimed method, metallurgical coke can be produced on any tube furnaces, it is only necessary to adjust the temperature regime (the authors carried out industrial tests on three types of furnaces).

Heating the carbon-containing mixture, sintering and calcination of the obtained coke is carried out in the presence of oxygen. As a rule, this is oxygen. The thermo-oxidative treatment of the carbon-containing charge provides the combustion of the released volatile substances (coke oven gas) and eliminates the danger of its explosion, because Tubular (calcining) furnaces, as a rule, do not have a system for trapping or afterburning of emitted volatile substances. In addition, the presence of oxygen (air) in the heating, sintering, and calcining zone saves fuel supplied to the tube furnace, since during the combustion of volatile substances released from a carbon-containing mixture, a large amount of heat is released.

The movement of the charge and gas (air) can be either in one direction or in the opposite. Or the direction of movement of the gas (air) can be set separately for heating (for example, countercurrent) and sintering with calcination (for example, forward flow).

The authors have repeatedly conducted industrial tests of the proposed method on three different designs of tubular rotary kilns with different directions of gas (air). The test results in all cases were approximately the same, in any case, the authors cannot say with certainty that the direction of the gas (air) is of fundamental importance for the proposed method.

Petroleum semi-coke with a yield of volatiles from 14 to 25% in the amount of (50 - 100) wt.% Obtained by delayed semi-coking of heavy oil residues is used as a starting material (initial carbon-containing charge).

Used in the inventive method, the petroleum coke has ductility, which manifests itself in the process of heating it at temperatures of 200-500 ° C (i.e., at the initial stage of the implementation of the proposed method). The manifestation of the plastic properties used in the inventive method of the petroleum coke at the stage of heating allows for further movement of the charge during rotation of the tube furnace to pellet the charge, i.e. to obtain bulk material, which, when it is subsequently sintered and calcined, turns into coke.

At the calcination stage, the obtained bulk material is desulfurized by breaking the theophene bonds at temperatures of 1320–1360 ° C. The sulfur content in the charge is reduced from 4.2% (in the original charge) to 0.7% (after calcination).

Volatiles released from the processed charge are burned in the working space of the tube furnace.

To obtain high-quality coke by the claimed method, the residence time of the mixture in the furnace should be sufficient to remove moisture, volatiles and end the physicochemical transformations in the calcined coke. The residence time of the charge in the furnace depends on such factors as the diameter and length of the furnace, the number of revolutions of the drum, the angle of inclination of the drum.

A factor affecting the residence time of the charge in the furnace and its productivity is the fill factor of the furnace. For each furnace, the optimal drum filling value is selected so that the coke, when moving in the calcination zone, is exposed to the maximum exposure to the burning torch and comes into contact with hot gases. When the drum is filled above the optimum, the heat exchange conditions of coke with flue gases deteriorate, and part of the material in the middle of the stream does not come into contact with the lining of the furnace or with incandescent gases, i.e. It is not heated by radiation or convection. In this case, the physicochemical processes in coke do not have time to end. With a reduced fill factor of the furnace, the thermal energy of the flue gases will not be fully utilized.

The rotational speed of the drum is set different for different designs of tube furnaces depending on the fill factor of the furnace, the characteristics of the carbon-containing charge, the state of the charge, the method of heating the charge in the furnace, etc. and is determined experimentally.

The authors do not know the formula for the dependence of the rotational speed of the drum of a tubular furnace depending on the fill factor of the furnace, the characteristics of the carbon-containing charge, the method of heating the charge, etc. Therefore, in the inventive method, it is impossible to give a rule according to which the choice of the rotation speed of the furnace drum is determined. This speed is determined empirically.

Sintering and calcination of the material obtained after heating is carried out at a temperature of 600-1500 ° C. To do this, adjust the temperature regime of the tube furnace by zones - in the heating zone provide a temperature in the range of 200-500 ° C, in the subsequent sintering and calcination zone provide a temperature in the range of 600-1500 ° C.

To organize such zones, it is required to introduce small design changes in the tubular furnace. The heating, sintering and calcining zones are distinguished by additional blower and draft means, which ensures the necessary temperature regime in each zone.

After calcination, the resulting coke is cooled, for example, in a cooling drum and then dispersed into fractions. A large fraction of coke is used as metallurgical coke, a small fraction as a carburizer.

Obtained by the inventive method, coke from the initial carbon-containing mixture, which is an oil semi-coke with a yield of volatile substances from 14 to 25% in the amount of (50 - 100) wt.%, Obtained by delayed semi-coking of heavy oil residues, fully meets the requirements for metallurgical cokes.

The nature of the initial mixture, which is an oil semi-coke with a yield of volatile substances from 14 to 25% in an amount of (50 - 100) wt.%, Obtained by delayed semi-coking of heavy oil residues, eliminates the need for additional sources of heating of the mixture when implementing the inventive method, and It also provides high-quality coke, which in its characteristics is not inferior to metallurgical coke.

In FIG. 1 shows a diagram of a furnace on which the inventive method was carried out.

The method was carried out on two furnaces.

Example 1

The implementation of the proposed method on a tubular furnace for calcining anthracite Novosibirsk electrode plant

The tube furnace contains: a metal drum 1, lined with refractory brick, which is mounted at a slight angle to the horizon on the support rollers 2. In some cases, the diameter of the drum is made variable in length. The drum is rotated by an electric motor through a gearbox and an open gear 3. The charge is loaded from the side of the head 4. The dry charge is fed by mechanical feeders, and the charge in the form of pulp is fed in bulk or through nozzles 5. Fuel is introduced through burners (nozzles) 6, placed in a hot head 7. Here, the finished product is sent to the refrigerator. Gases from a rotary kiln are cleaned of dust in system 8. To improve the heat transfer conditions, various heat-exchange devices 9 are built into the kiln — scraper blades, shelves, chain curtains, nozzles, etc. For the same purpose, in some cases, the lining of furnaces is carried out with a complex shape, for example, cell.

As the fuel can be used pulverized, solid, liquid or gaseous fuel, which is burned directly in the working space of the furnace.

In the refrigerator, the material is cooled to 80-100 ° C. The refrigerator drum is constantly cooled by water. Water consumption is ~ 15 m ³ per tonne of calcined material.

Due to the tilt and rotation of the drums, the calcined material is mixed along the length of the furnace and intensively mixed. The length of the furnace is 60 m, the diameter is 4.5 m. The drum filling factor is 6-8%, the inclination angle is 3.5 degrees. The maximum drum speed is 1.4 rpm.

According to the length of the drum can be divided into three zones:

Zone 1: The zone of drying and heating of the material, the longest zone. The temperature of the coolant at the beginning of the zone is ~ 1200 ° C, at the end of 500-600 ° C.

Zone 2: Annealing zone. This is the zone of maximum temperatures in the furnace (up to 1400 ° C), its length is determined by the length of the flame and is 3-10 m. When calcining a carbon-containing mixture with a relatively high yield of volatile substances as a result of their combustion, the calcination zone can increase to 12-15 m.

Zone 3: The shortest cooling zone (1.5 - 2.0 m). It is located near the front head of the drum.

The size of the zones (especially the calcination zone) depends on the productivity of the furnace and the burning of material. With the extension of the calcination zone, the residence time of the material at high temperatures increases. With a large distance of the torch from the front head, combustion (fumes) of the calcined material increases.

The temperature in the furnace is maintained by supplying fuel and creating optimal vacuum. A prerequisite is the tightness of the furnace. Only in this case can the air supply to the furnace be clearly regulated.

Technological parameters of the furnace

Before carrying out the work according to the claimed method, the furnace worked in anthracite calcination mode.

Calcination furnace operating mode

1. The temperature of the coolant at the inlet to the drum 1250 ° C

2. The temperature of the coolant at the outlet of the drum 1050 ° C

3. The consumption of natural gas 450 m ³ / h

4. Air consumption 5432 m ³ / h

5. Productivity for petroleum coke 12 t / h

For the basic mode, a heat balance was drawn up.

In the technological process, air suction and coke “waste” are not controlled. When compiling the balance, the “waste” of coke was taken equal to 5% of the productivity, heat loss of 5% of the heat input, and the heat that is lacking in the flow part of the balance is spent on heating the sucked-in air.

The coefficient of excess air during the combustion of natural gas was 1.15. The calorific value of natural gas is 33142 MJ / m ³ .

Heat balance MJ / h (kW)%

Coming

1. The heat of combustion of gas 14914 (4143) 21.4

2. The heat of combustion of volatile substances 34008 (9447) 48.9

3. Combustion of material 20640 (5733) 29.7

Total 69562 (19333) 100

Consumption

1. With calcined coke 21600 31.1

2. With combustion products 8621 12.4

3. Heat loss 3,500 5.0

4. With suction air 35844 51.5

Total 69562 (19333) 100

After determining the operating mode of the furnace, its characteristics according to the data obtained during anthracite calcination, the anthracite supply was stopped, the anthracite was discharged, and a carbon-containing mixture was fed into an empty heated furnace, which was used as an oil semicoke with a yield of volatiles from 14 to 25% in quantity (50 -100) wt.% Obtained by delayed semi-coking of heavy oil residues (hereinafter referred to as oil semi-coke).

Technical analysis of petroleum coke is given in table 1 and table 1.1.

where W ^r - humidity;

A ^d is the ash content;

W ^daf — volatile matter content;

S ^d is the sulfur content.

Used in the inventive method, petroleum semi-coke is characterized by an increased yield of volatile substances (17.3%) compared with petroleum coke (8.57%).

To calculate the amount of heat released during the combustion of volatiles, the yield of coking chemical products was determined.

A comparative analysis of the incoming heat balance items is presented in Table 3.

The consumption of natural gas when calcining anthracite is assumed to be 450 m ³ / h, petroleum coke and petroleum coke - 50 m ³ / h. It is assumed that 5% of the processed material burns. The output of volatile substances from anthracite 3.5%.

The heat from the combustion of volatile substances contained in petroleum coke increases 1.6 times compared to petroleum coke. By reducing the consumption of natural gas from 450 to 50 m ³ / h, the heat input from its combustion is reduced by 9 times. The heat input from the combustion of the material is considered the same in both cases. The total heat input during the processing of petroleum coke increases by ~ 10% compared with the heat generated during calcination of petroleum coke.

It should be noted that even without the supply of natural gas, the heat input during sintering of petroleum coke exceeds the heat input during heat treatment.

The movement of the charge and air were opposite to each other (countercurrent).

Table 3.1 shows the data on the quality obtained in Example 1 coke compared with the established requirements.

Example 2

In the same furnace under the same technological conditions as in Example 1, coke was obtained on a tube furnace for calcining the anthracite of the Novosibirsk Electrode Plant from a mixture of petroleum coke (table 1) and coal concentrate GZh grade (gas-fatty coals) of the Raspadskaya concentrator ". For coking, we used blends consisting of petroleum coke and coal concentrate in a ratio of components of 50:50 and 70:30, respectively.

Quality indicators of coal concentrate at the Raspadskaya concentrator: moisture (W ^a ) - 2.83%; ash (A ^d ) - 7.64%; volatile (W ^daf ) - 35.0%; sulfur (S ^d ) - 0.93%.

Table 4 shows information about the quality of coke obtained in example 2.

As can be seen from the example (Table 4), the parameters of the obtained coke also meet the requirements of GOST, but when the content of petroleum coke is 50%, the index of hot strength CRI is already slightly higher than that specified in GOST. But this drawback is not significant, since it is not standardized.

Example 3

The second furnace, on which work was carried out

Limestone kiln in Nizhny Tagil, Sverdlovsk Region. Rotary kiln with a diameter of 3.6 m, length 60 m. The frequency of rotation of 1.6 rpm

The consumption of oil semicoke is 10 t / h. Natural gas was used in the burner only when the furnace was heated to operating temperature, flow rate 300 m ³ / h.

Obtained in the second example, coke had practically the same indicators as in the first example (Table 3.1).

As can be seen from table 3.1, obtained by the claimed method, coke has indicators of ash, mechanical (CSR) and hot (CRI) strength above the indicators established by GOST.

The indicator associated with the sulfur content is worse than established by GOST, which limits the use of coke obtained by the claimed method in blast furnace production, however, such coke can be widely used in mineral wool cupolas, as well as in non-ferrous metallurgy (copper and zinc production), where sulfur is specially added to the process (sulphiding reduction smelting).

The improvement of coke quality occurred in relation to the following indicators: ash content, mechanical and hot strength.

The inventive method does not require the use of special equipment or significant structural changes in a tubular furnace.

The production of coke from petroleum coke with a yield of volatiles from 14 to 25% in the amount of (50 - 100) wt.%, Obtained by delayed coking of heavy oil residues on a tube furnace according to the claimed method, can significantly reduce the cost of coke production.

Claims (4)

1. A method of producing metallurgical coke, including heating, sintering and calcining a carbon-containing mixture in a moving stream, characterized in that the heating of the carbon-containing mixture in a moving stream is carried out in the presence of oxygen in the heating zone of a rotary tube furnace with a temperature in the range of 200-500 ° C, and sintering and calcining a carbon-containing mixture is carried out in the sintering and calcining zone of a rotary tube furnace with a temperature in the range of 600-1500 ° C, and a carbon-containing mixture with a content of 50-100 wt.% oil is used ukoksa a yield of volatiles of 14 to 25 wt.%, prepared by slow carbonization of heavy oil residues. 2. The method according to p. 1, characterized in that the heating of the mixture is carried out with the associated or countercurrent movement of the mixture and gas. 3. The method according to p. 1, characterized in that the exhaust gases are used to heat the air entering the tube furnace. 4. The method according to p. 1, characterized in that the obtained coke after calcination is cooled with water and / or steam.