CN101774569B - Preparation method of calcium carbide formed coke - Google Patents

Abstract

The invention discloses a method for preparing calcium carbide coke, which uses plasma coal cracking solid products as raw materials, and comprises the following steps: 1) pretreatment: the plasma coal cracking solid products are deashed first, and then devolatilized Carbonization to obtain coke powder with ash content ≤ 9% and volatile content ≤ 2%; 2) Ingredients: use powdered calcium hydroxide as a binder, mix coke powder and powdered calcium hydroxide evenly to obtain a mixture; then mix 3) Molding: pressurize the material at room temperature to obtain green balls; 4) Curing of green balls: stack the green balls into a curing tank, pass in _CO2 for curing; leave the tank for drying Or dry to get the coke. The form coke prepared by this method can be used as a special carbon material for calcium carbide production.

Description

Preparation method of calcium carbide coke

technical field

The invention relates to a method for preparing calcium carbide coke by plasma cracking solid products of coal powder.

Background technique

In the process of plasma cracking coal to acetylene, coal and plasma react in the cracking reactor, and the cracked gas is quenched, dedusted and multi-phase separated to obtain three parts: gas phase, liquid phase and solid phase. The solid phase is called solid product (that is, the solid product of plasma coal cracking), and the yield accounts for more than 50% of the input coal powder.

The solid phase product has small particle size (average particle size is less than 50 μm, 90% is less than 125 μm), large specific surface area, and contains inorganic substances such as quartz stone, dolomite, and calcite. The composition characteristics and elements of a certain batch of Xinjiang coal plasma cracking solid products The composition is shown in Tables 1 and 2.

Table 1. Characteristics of solid products of plasma coal cracking

M _ad % A _d % V _daf % FC _d % CRC Q _{net, ar} (MJ/kg) ST(°C) Solid product 4.77 18.22 26.25 60.55 3 21.97 1190

Note: M, A, V, FC, CRC, Q, and ST in the table respectively represent moisture, ash, volatile matter, fixed carbon content, coke residue characteristics, calorific value, and softening temperature; subscripts ad, d, daf, net , ar represent the air-dried basis, dry basis, dry ash-free basis, received base low-temperature calorific value, respectively.

Table 2. Elemental composition of solid products of plasma coal cracking (dry ash-free basis)

C% H% N% O% S% Solid product 90.73 3.78 1.97 2.82 0.70

The solid product of plasma coal cracking has the advantages of low sulfur and nitrogen content and a large number of microporous structures on the surface, which has great advantages in the preparation of molded coke.

Coke is an important resource, widely used in metallurgy, foundry and chemical industry, one of its important uses is to produce calcium carbide. Calcium carbide is an important raw material for the production of acetylene. Synthetic calcium carbide is based on the action of carbon materials and lime at high temperature:

CaO+3C→CaC ₂ +CO 465kJ/mol

The reaction is an endothermic reaction, and it is beneficial to carry out the positive reaction at high temperature, so it is usually carried out at 1800-2100°C. At 1750°C, CaO-CaC ₂ forms the lowest eutectic product, and the lime and coke enter the calcium carbide furnace in granular form, and gradually react to form a molten liquid during the falling process.

The general requirements for synthetic calcium carbide coke are: fixed carbon>84%, ash<15%, volatile matter<1.5%, moisture<3%. Particles with a shape of 3 to 20 mm. The coke used in my country's calcium carbide industry has low fixed carbon and high ash content. Usually mixed coke blocks have 82-84% fixed carbon and 14-16% ash; crushed coke has 78-82% fixed carbon and 17-19% ash.

To smelt coal into coke, coking coal (medium metamorphic bituminous coal) is required as the main raw material coal. Coking coal is a type of coal that has stricter requirements on coal quality. According to statistics in 1987, my country's coking coal reserves accounted for 28% of the country's coal quality, but volatile gas coal accounted for more than 50%, and most of the coking coal had a high ash content and was difficult to wash, which affected the quality of coke produced. With the increasing shortage of high-quality coking coal resources, the coke technology of non-coking coal has been paid more and more attention. How to use the plasma coal cracking solid products with large output and low cohesiveness to produce coke is very meaningful.

Coke is generally made of coal powder (or coke powder) as the main raw material, mixed with or without a binder to pressurize the formed coal, and then processed into a product with a certain shape and a certain strength after carbonization, which can replace conventional coke.

At present, the binder used in the coke process is basically coal tar pitch, such as the DKS method in Japan and the FMC method in the United States. Chinese patent CN1105381A has invented a method for preparing calcium carbide coke by using calcium carbide slag and coke foam as raw materials, but the process only involves waste utilization in the production process of calcium carbide, and the raw material used is coke foam, which itself meets the index. Adhesive molding is enough.

However, if the solid product of plasma coal cracking is used to prepare coke, the problem of excessive ash and volatile content must be solved; the strength and reactivity after forming must be improved. Therefore, there is currently no method for preparing coke by using plasma coal cracking solid products.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing molded coke, and the molded coke prepared by this method can be used as a special carbon material for calcium carbide production.

In order to solve the above-mentioned technical problem, the present invention provides a kind of preparation method of calcium carbide type coke, use plasma coal cracking solid product as raw material, comprise the following steps:

1), pretreatment:

The solid product of plasma coal cracking is first deashed, and then devolatilized and carbonized to obtain coke powder with ash content ≤ 9% and volatile content ≤ 2%;

2), ingredients:

Using powdered calcium hydroxide as a binder, uniformly mix coke powder and powdered calcium hydroxide to obtain a mixture; the calcium hydroxide accounts for 13% to 20% of the weight of the mixture; then mix the mixture with water, Obtain material, described water accounts for 15%～25% of material weight;

3), molding:

The material is pressure-molded at room temperature to obtain green balls;

4), raw ball solidification:

Pile the green balls into the curing tank and pass CO ₂ to cure; the green balls are cured at a pressure of 0.1-1MPa and a temperature of 50-90°C for 8-12 hours; out of the tank and dried or air-dried to obtain coke.

As the improvement of the preparation method of calcium carbide type coke of the present invention: the deliming in step 1) is to comprise the following steps:

A. Add 4-6 mass times of 8-10 wt% NaOH solution or KOH solution to the plasma coal cracking solid product, stir and mix evenly, heat up to 180-210°C for 1-2 hours;

B. Filter the reaction product obtained in step A, and wash the filter cake with water until the pH is 7 to 7.5; then add 5 to 10 wt% of hydrochloric acid solution or nitric acid solution as dilute acid in the filter cake after washing with water, and stir evenly after mixing , heating up to 80-95° C. for 1-1.5 hours; the mass ratio of the dilute acid to the plasma coal cracking solid product is 4-6:1;

C. Wash the reaction product obtained in step B with water until the pH is 6.5-7, filter, and dry the obtained filter cake; obtain a deashed plasma coal cracking solid product.

As a further improvement of the preparation method of calcium carbide type coke of the present invention: the devolatilization carbonization in step 1) comprises the following steps:

A. Put the deashed plasma coal cracking solid product into the carbonization chamber, first dehydrate at 110°C for 30 minutes, and then dry distillation at 500-550°C for 30-45 minutes;

B. Carbonizing the solid product obtained in step A at a high temperature of 800-900° C. for 4-5 hours;

C. Sieve the product obtained in step B, and pulverize the product larger than 125 μm.

As a further improvement of the preparation method of the calcium carbide coke of the present invention: in step 3), the molding pressure is 0.6-3t (ton), and the green balls are cylindrical green balls of 0.8-1.2cm×Φ1.8cm.

As a further improvement of the preparation method of the calcium carbide coke of the present invention: in step 4), the flow rate of CO ₂ required per ton of green pellets is 40-150 m ³ /h.

As a further improvement of the preparation method of the calcium carbide coke of the present invention: in step 2), the particle size of calcium hydroxide is 50 μm.

The preparation method of the calcium carbide type coke of the present invention uses the solid product of plasma coal cracking as the main raw material (the solid product of plasma coal cracking obtained under different working conditions can be used as the raw material of the present invention), which has weak cohesiveness, It is characterized by ultrafine particles (average particle size less than 50 μm), large specific surface area (more microporous surface), low sulfur and nitrogen content, and its composition is shown in Table 1 and Table 2. The product after the devolatilization and carbonization treatment in step 1) is cooled and passed through a 120-mesh sieve, and a small amount of the oversize is crushed to less than 125 μm, and mixed with the undersize to obtain coke powder. Because the solid product of plasma coal cracking is weakly cohesive, even if a small amount of particles coalesce, the coke powder obtained is still millimeter-sized particles with low strength, so it is very easy to break. The composition characteristics of the obtained coke powder are shown in Table 3.

Table 3 Composition characteristics of coke powder after pretreatment of solid products of plasma coal cracking

M _ad % A _d % V _daf % FC _d % Burnt powder 0.62 7.07 2.12 90.96

Because the solid product of plasma coal cracking itself is ultrafine particles, the average particle size is less than 50 μm, and the specific surface area is large, so the strength of the prepared coke is higher than that of ordinary coal powder. The present invention uses powdery calcium hydroxide as binding agent, and advantage is: because CaO is another raw material that calcium carbide is synthesized, therefore can not introduce extra impurity with calcium hydroxide as binding agent, and can provide in solidification (carbonation) process required strength; moreover, the type coke doped with lime of the present invention has a higher specific resistance than ordinary coke, which is more conducive to the production of calcium carbide.

The preparation method of the form coke of the present invention adopts the route of firstly deashing and devolatilizing, then forming, and then carbonating (curing). The process is simple and easy to operate. However, the current existing mold coke process requires two carbonizations before and after, which consumes a lot of energy. The present invention only needs to be carbonized once, so it also has the advantage of reducing production costs. The main mass of the coke prepared by the method of the present invention is shown in Table 4.

Table 4 Main quality indicators of calcium carbide coke

indicators This method prepares calcium carbide coke General coke shape  Cylinder 0.8～1.2cm×Φ1.8cm Irregular 0.3～2cm FC _d % 76～82 82～84 A _d % 17～22 14～16 V _daf % 1.5～2.5 2% M _ad % ＜2% ＜3% Cold compressive strength (kg/piece) 120～220kg - Total porosity (%) 42～51 40～50

As can be seen from Table 4, the form coke prepared by the method of the present invention has a slightly higher ash content, but since the calcium introduced by the binder is mainly calcium, which is not an impurity for calcium carbide production, the true form coke The ash content should be comparable to the raw coke powder. After subtracting the added calcium from the ash, the fixed carbon content should be around 90%.

In summary, the preparation method of calcium carbide coke of the present invention has the following advantages:

1. The raw material used is the solid product of plasma coal cracking, which has large output, low value, and poor cohesiveness. Making shaped coke greatly improves its utilization value; avoiding the use of high-quality coking coal whose resources are decreasing year by year, thus greatly reducing production costs .

2. The solid product of plasma coal cracking itself is ultra-fine particles, the average particle size is less than 50 μm, and there are a large number of microporous structures on the surface, so the strength and reactivity of the prepared coke are higher than ordinary coal powder;

3. The binder used is lime. The advantage is that CaO is another raw material for calcium carbide synthesis. As a binder, it will not introduce additional impurities, and it can provide the required strength after carbonation. The lime-doped coke is comparable to ordinary coke. Compared with its higher specific resistance, it is more conducive to the production of calcium carbide;

4. Adopt the route of deashing, devolatilization first, then molding, and then carbonation to simplify the process. Moreover, the use of a large amount of tar pitch in the conventional coke process is avoided, energy consumption is saved and costs are reduced.

Detailed ways

Embodiment 1, a kind of preparation method of calcium carbide type coke, take plasma coal cracking solid product as raw material, carry out following steps successively:

1), pretreatment:

The solid product of plasma coal cracking is first deashed and refined, and then devolatilized and carbonized; the details are as follows:

①, deashing:

A. Add 5 times the mass of caustic soda solution (NaOH solution) with a concentration of 10wt% to the solid product of plasma coal cracking, stir it mechanically to make it evenly mixed, then heat up to 200-210° C. for 2 hours; end the reaction.

B, the reaction product obtained in step A is filtered, and the filter cake is washed with water until the pH is 7 to 7.5; then adding a concentration of 10wt% hydrochloric acid solution to the filter cake washed with water, the quality of the hydrochloric acid solution is the plasma coal cracking solid 5 times of the product, after uniform stirring and mixing by machinery, the temperature was raised to 90-95°C and reacted for 1 hour.

C. Wash the reaction product obtained in step B with water until the pH is 6.5-7, filter, and dry the obtained filter cake at 50° C. to obtain a deashed plasma coal cracking solid product.

②, devolatilization carbonization:

A. Put the above-mentioned deashed plasma coal cracking solid product (dried deashed sample) into the carbonization chamber, first dehydrate at 110°C for 30min, and then dry distillation at 500°C for 45min; get solid product and tar, tar can be Recycle.

B. Carbonizing the solid product obtained in step A at a high temperature of 800° C. for 5 hours;

C. The product obtained in step B is cooled slightly, and then coke is taken out, passed through a 120-mesh sieve after cooling, and a small amount of the oversize material is crushed to less than 125 μm, and then mixed with the undersize material to obtain coke powder.

The coke powder has a very low ash content (ash content ≤ 9%) and volatile content ≤ 2%, which is used as a molding raw material and meets the index of coke.

Moreover, in the following steps, lime (calcium hydroxide) is used as a binding agent, no volatile matter will be introduced, and the introduced ash (calcium) is not an impurity for calcium carbide production, so the composition characteristics of the coke powder are equivalent to the produced Compositional characteristics of coke.

2), ingredients:

Using powdery (50 μm in particle size) calcium hydroxide as a binder, mix the coke powder and powdery calcium hydroxide evenly to obtain a mixture. Calcium hydroxide accounts for 15% of the total weight of the mixture, that is, the ash ratio is 15%; Then the mixture is mixed with water to obtain the material, and the water accounts for 21% of the total weight of the material, that is, the molding moisture is 21wt%;

3), forming:

The material was press-molded at room temperature, the molding pressure was 1.8t, and a cylindrical green ball of 1.2cm×Φ1.8cm was obtained, with a mass of about 3.8g.

The formed cylindrical green balls have high water content and certain strength.

4), green ball solidification (carbonation):

The green pellets are piled into the carbonation tank (curing tank), the tank temperature is 80°C; the preheated CO ₂ is introduced from the bottom, and the required flow rate per ton of green pellets is 45m ³ /h, and the top is provided with an outlet to discharge the CO ₂ moisture , the tank pressure is 0.1MPa, and the treatment time is 8.5h. The carbonated coke is taken out and dried or air-dried.

The obtained form coke had a compressive strength of 187kg and a total porosity of 47%.

Embodiment 2, a kind of preparation method of calcium carbide type coke, take plasma coal cracking solid product as raw material, carry out following steps successively:

1), pretreatment:

In step 1) of embodiment 1, alkali is changed into potassium hydroxide, acid is changed into nitric acid, and all the other steps are the same.

2), ingredients:

Using powdered calcium hydroxide as a binder, mix coke powder and powdered calcium hydroxide evenly to obtain a mixture. Calcium hydroxide accounts for 20% of the total weight of the mixture, that is, the ash ratio is 20%; then mix the mixture with water Mix to obtain the material, 23% of the total weight of water and material, that is, the molding water is 23wt%.

3), forming:

The material was press-molded at room temperature, the molding pressure was 3t, and a cylindrical green ball of 1.1cm×Φ1.8cm was obtained, with a mass of about 3.7g.

4), green ball solidification (carbonation):

The green pellets are piled into the carbonation tank (curing tank), the tank temperature is 65°C; the preheated CO ₂ is introduced from the bottom, and the required flow rate per ton of green pellets is 100m ³ /h, and the top is provided with an outlet to discharge the CO ₂ moisture , the tank pressure is 0.1MPa, and the treatment time is 8h. The carbonated coke is taken out and dried or air-dried.

The coke has a compressive strength of 223kg and a total porosity of 43%.

Embodiment 3, a kind of preparation method of calcium carbide type coke, use plasma coal cracking solid product as raw material, carry out following steps successively:

1), pretreatment:

With the step 1) of embodiment 1.

2), ingredients:

Using powdered calcium hydroxide as a binder, mix coke powder and powdered calcium hydroxide evenly to obtain a mixture. Calcium hydroxide accounts for 18% of the total weight of the mixture, that is, the ash ratio is 18%. Then mix the mixture with water Mix to obtain the material, 20% of the total weight of water and material, that is, the molding water is 20wt%.

3), molding:

The material was press-molded at room temperature, the molding pressure was 0.6t, and a cylindrical green ball of 1.1cm×Φ1.8cm was obtained, with a mass of about 3.7g.

4), green ball solidification (carbonation):

The green pellets are piled into the carbonation tank (curing tank), the tank temperature is 90°C; the preheated CO ₂ is introduced from the bottom, and the required flow rate per ton of green pellets is 40m ³ /h, and the top is provided with an outlet to discharge the CO ₂ moisture , the tank pressure is 0.5MPa, and the treatment time is 6h. The carbonated coke is taken out and dried or air-dried.

The form coke has a compressive strength of 122kg and a total porosity of 50.3%.

Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the present invention.

Claims (6)

1. A preparation method of calcium carbide type coke is characterized in that: taking plasma coal cracking solid product as raw material, comprising the following steps: 1), pretreatment: The solid product of plasma coal cracking is first deashed, and then devolatilized and carbonized to obtain coke powder with ash content ≤ 9% and volatile content ≤ 2%; 2), ingredients: Using powdered calcium hydroxide as a binder, uniformly mix coke powder and powdered calcium hydroxide to obtain a mixture; the calcium hydroxide accounts for 13% to 20% of the weight of the mixture; then mix the mixture with water, Obtain material, described water accounts for 15%～25% of material weight; 3), molding: The material is pressure-molded at room temperature to obtain green balls; 4), raw ball solidification: Pile the green balls into the curing tank and pass CO ₂ to cure; the green balls are cured at a pressure of 0.1-1MPa and a temperature of 50-90°C for 8-12 hours; out of the tank and dried or air-dried to obtain coke. 2. the preparation method of calcium carbide type coke according to claim 1 is characterized in that: the deashing in described step 1) comprises the following steps: A. Add 4-6 mass times of 8-10 wt% NaOH solution or KOH solution to the plasma coal cracking solid product, stir and mix evenly, heat up to 180-210°C for 1-2 hours; B. Filter the reaction product obtained in step A, and wash the filter cake with water until the pH is 7 to 7.5; then add 5 to 10 wt% of hydrochloric acid solution or nitric acid solution as dilute acid in the filter cake after washing with water, and stir evenly after mixing , heating up to 80-95° C. for 1-1.5 hours; the mass ratio of the dilute acid to the plasma coal cracking solid product is 4-6:1; C. Wash the reaction product obtained in step B with water until the pH is 6.5-7, filter, and dry the obtained filter cake; obtain a deashed plasma coal cracking solid product. 3. the preparation method of calcium carbide type coke according to claim 2 is characterized in that: the devolatilization carbonization in described step 1) comprises the following steps: A. Put the deashed plasma coal cracking solid product into the carbonization chamber, first dehydrate at 110°C for 30 minutes, and then dry distillation at 500-550°C for 30-45 minutes; B. Carbonizing the solid product obtained in step A at a high temperature of 800-900° C. for 4-5 hours; C. Sieve the product obtained in step B, and pulverize the product larger than 125 μm. 4. The method for preparing calcium carbide coke according to claim 3, characterized in that: in the step 3), the molding pressure is 0.6-3t, and the green ball is a cylindrical shape of 0.8-1.2cm×Φ1.8cm raw balls. The method for preparing calcium carbide coke according to claim 4, characterized in that: in step 4), the flow rate of CO ₂ required per ton of green pellets is 40-150 m ³ /h. 6. The method for preparing calcium carbide coke according to claim 5, characterized in that: in the step 2), the particle size of calcium hydroxide is 50 μm.