CN111154278B

CN111154278B - Method for preparing high-strength formed coke by cold press molding

Info

Publication number: CN111154278B
Application number: CN202010011496.8A
Authority: CN
Inventors: 张斌
Original assignee: Hunan University
Current assignee: Xiaoyi Chengyuan Environmental Protection Technology Co.,Ltd.
Priority date: 2020-01-06
Filing date: 2020-01-06
Publication date: 2022-01-25
Anticipated expiration: 2040-01-06
Also published as: CN111154278A

Abstract

The invention relates to a formed coke molding process and discloses a method for preparing high-strength formed coke through cold press molding. The mass ratio of the used binder is as follows: 0-20 parts of corn starch, 60-80 parts of asphalt, 0-5 parts of artificial graphite or boron compound, 0-10 parts of cement or magnesium oxide, 0-20 parts of ethyl acetate and 0-2 parts of sodium hydroxide. The total proportion of the binder is 8.6-10.7% of the mass of the coke powder. Mixing the mixed binder and coke powder (metallurgical coke or petroleum coke) uniformly in advance, adding a certain amount of water, and performing cold press molding at normal temperature to obtain formed coke. The formed coke prepared by the invention has the excellent characteristics of high cold and hot strength, good thermal stability, high forming rate, low cost and the like.

Description

Method for preparing high-strength formed coke by cold press molding

Technical Field

The invention belongs to a formed coke forming process, and relates to a method for preparing formed coke with high cold and hot strength by mixing a binder and coke powder at normal temperature and then pressing and forming.

Background

The formed coke is prepared by mixing waste coke powder serving as a raw material with a binder and then pressing and forming the mixture to obtain a product which has certain mechanical strength and meets smelting requirements. Asphalt is an organic binder commonly used in the production of formed coke, wherein beta resin can provide the cold strength of the formed coke, and the formed coke is carbonized at high temperature to form a carbon skeleton to provide the hot strength of the formed coke. However, since asphalt is solid at normal temperature and has no adhesive property, it needs to be heated to a temperature higher than the melting point to act as an adhesive. Chinese patent application No. CN201210139885.4 discloses that the conventional asphalt adding method is to melt asphalt at a temperature far higher than the softening point (for example, the softening point of medium temperature asphalt is 75-95 deg.C) (140-. Meanwhile, in order to prevent the asphalt from being solidified due to cooling, heat preservation treatment is required in the stirring process, so that sufficient infiltration and uniform mixing between the asphalt and the solid materials can be ensured, and then heat preservation is required to be carried out continuously so as to facilitate hot press forming, so that the process operation is difficult and the equipment is complicated. In order to reduce the disadvantages, the technological method needs to be improved, solvent is added to activate the binding property of the asphalt at normal temperature, or starch is added to prepare formed coke at normal temperature, and then the formed coke is heated to the melting point of the asphalt to activate the binding property. Chinese patent application No. CN201110131643.6 teaches that the addition of xylene as a solvent eliminates the need to heat and knead the mixture of asphalt and powder before molding, and realizes the use of asphalt as a binder at normal temperature. But xylene is a highly carcinogenic organic substance, and has great harm to the health of workers when being produced and operated in the environment for a long time. Corn starch is a normal-temperature organic binder, can be converted into gelatinized starch at 70-90 ℃, further improves the formed coke cold strength due to higher viscosity of the gelatinized starch, but generates carbonization phenomenon at more than 200 ℃, loses cohesiveness and cannot provide high-temperature strength. The addition of the asphalt modifier, namely the artificial graphite or boron compound can improve the viscosity of the asphalt before carbonization in the early stage and the coking value of the asphalt after carbonization in the later stage, inhibit the generation of an asphalt intermediate phase, remarkably increase the oxidation resistance of the asphalt, improve the microstructure of the asphalt after carbonization and further improve the high-temperature strength of the formed coke. The cement or magnesium oxide has the functions of compensating the formed coke strength of corn starch losing cohesiveness after carbonization at the temperature of more than 200 ℃, compensating the formed coke strength reduced by the rapid reduction of viscosity after the temperature of asphalt softening point, and improving the defects of unstable high-temperature performance of the organic binder because of the formed coke strength reduced by cohesiveness caused by polycondensation reaction before carbonization. The sodium hydroxide can promote the gelatinization process, reduce the gelatinization temperature and directly influence the cohesiveness of the starch and the normal temperature strength of the formed coke.

Disclosure of Invention

The invention provides a method for preparing formed coke by cold press molding of a formed coke binder, which has the advantages of simple process flow, low production cost, high molding rate and high cold and hot strength and can meet the requirements of a metallurgical submerged arc furnace.

The method for preparing the high-strength formed coke by cold press molding is adopted to solve the problems, the binder is added into coke powder and uniformly mixed, water or a non-aqueous solvent is added, and the formed coke is obtained by normal-temperature briquetting molding and drying, and comprises the following specific steps:

(1) putting raw coke powder into a raw material bin, conveying the coke powder in the raw material bin into a hammer crusher through a belt, and crushing the coke powder by using the crusher until the particle size is less than 3 mm;

(2) mixing binder components, adding the binder components into a stirrer, and uniformly stirring, wherein the binder components comprise the following mass ratio: 0-20 parts of normal temperature binder, 60-80 parts of asphalt, 0-5 parts of asphalt modifier, 0-10 parts of formed coke strength stabilizer and 0-2 parts of starch pasting modifier;

(3) meanwhile, the mixed binder is conveyed into a crusher through a screw feeder, the coke powder and the binder components are mixed in the crusher, the ratio of the coke powder to the binder components is controlled and adjusted through the rotating speed of the screw feeder so as to realize non-intermittent continuous ball pressing, and the total ratio of the binder is 8.6-10.7% of the mass of the coke powder;

(4) conveying the mixture of the two materials into a horizontal mixer through a belt, adding water or a non-aqueous solvent into the mixer, and uniformly mixing the coke powder and the binder to obtain a final material, wherein the material temperature at the outlet of the mixer is 70-90 ℃, the moisture content of the final material is 8-15%, the non-aqueous solvent is 0-20 parts, and the adding amount of the moisture is not more than 15%;

(5) pressing the final material into blocks to obtain wet blocks;

(6) and transferring the formed final material, namely the wet block, to a drying bin for drying.

Furthermore, in the coke powder, the ratio of the particle size of 0.9-3mm is 40%, the ratio of 0.2-0.9mm is 30%, and the ratio of below 0.2mm is 30%.

Further, the normal-temperature binder is corn starch, the asphalt modifier is artificial graphite or boron compounds, the formed coke strength stabilizer is cement or magnesium oxide, the starch gelatinization modifier is sodium hydroxide, and the non-aqueous solvent is ethyl acetate. In general, when corn starch is added without ethyl acetate, the higher the moisture and temperature, the more uniform the mixing, the higher the degree of gelatinization of the corn starch, the higher the pelletization rate, the higher the cold and hot strength, the insufficient moisture addition, the large internal friction, the uneven mixing, the lower the yield and the cold and hot strength, but the too much moisture addition, exceeding 15%, both the pelletization rate and the final cold and hot strength decrease. If the corn starch is not added, ethyl acetate is added, water is directly added instead of introducing water vapor, and the water vapor has the function of gelatinizing the corn starch.

Further, the coke powder is metallurgical coke powder or petroleum coke powder, the granularity of corn starch, asphalt, artificial graphite, magnesium oxide and sodium hydroxide is below 0.15mm, the asphalt is high-temperature asphalt or medium-temperature coal asphalt, preferably non-national standard high-temperature coal asphalt, the total amount of water added is 8-15% of the mass of the metallurgical coke or petroleum coke, an atomizing nozzle is opened, water vapor heated by heat-conducting oil enters a horizontal mixer through the nozzle to heat the mixture, if the water vapor is not added enough, a water pipe can be opened to supplement water, the temperature in the mixer is 70-90 ℃, and the briquetting pressure is 30-35 MPa.

Furthermore, the coke powder is metallurgical coke powder or petroleum coke powder, the corn starch is 0-20 parts, the high-temperature asphalt is 60-80 parts, the artificial graphite or boron compound is 4-5 parts, the cement or magnesium oxide is 0-10 parts, the sodium hydroxide is 0-2 parts, and the total amount of the binder is 8.6-10.7% of the mass of the metallurgical coke or petroleum coke.

Furthermore, the coke powder is metallurgical coke powder or petroleum coke powder, the ethyl acetate is 0-20 parts, the high-temperature asphalt is 60-80 parts, the artificial graphite or boron compound is 0-5 parts, the total amount of the binder is 10% -10.5% of the mass of the metallurgical coke or petroleum coke, and the total amount of the water is 8-9% of the mass of the metallurgical coke.

Further, if the volatile content of the petroleum coke is too high, the petroleum coke can be dried for 2 hours at the temperature of 250 ℃ and 300 ℃ and then added with a binder and a water pressure block for molding.

Further, in the step (5), the briquetting method is to convey the uniformly mixed material to a pair-roller extrusion granulator through a belt for pelletizing, wherein the wet block is a wet ball, and the shape of the wet ball is an ellipse.

The wet bulb had a size of 40mmx60mm and a thickness of 20 mm.

In the step (6), the wet balls are conveyed into a drying bin through a belt to be dried, wherein the temperature is 130 ℃, and the time is 6 hours.

Further, the boron compound is one or a combination of any two of boron oxide, pyridine borane, boron carbide, borax and boric acid.

The cement is magnesia cement or aluminate refractory cement, and the magnesia is light magnesia.

The invention has the advantages that:

1. the corn starch and the sodium hydroxide are added and heated to 70-90 ℃ for gelatinization, so that cold press molding can be realized, and the cold strength is high.

2. The non-national standard high-temperature asphalt is added instead of the medium-temperature asphalt, so that the price is very low on one hand, and the high-temperature carbonization coking value of more than 50 percent can be obtained on the other hand, the high-temperature strength is improved, and the volatile component content is greatly reduced.

3. Adding the modifier of artificial graphite or boron compounds, increasing the softening temperature of the asphalt, improving the cohesiveness of the asphalt, reducing the generation of an asphalt intermediate phase, enhancing the oxidation resistance of the asphalt, adjusting the microstructure of the carbonized asphalt, increasing the coking value of the carbonized asphalt and finally increasing the high-temperature strength of the formed coke.

4. The addition of the stabilizer cement or magnesium oxide can compensate the formed coke strength of the corn starch losing cohesiveness after carbonization at the temperature of more than 200 ℃, compensate the strength reduction caused by the viscosity rapidly reduced after the asphalt softening point temperature, improve the formed coke strength reduced by cohesiveness due to the occurrence of polycondensation reaction before carbonization, improve the defect of unstable high-temperature performance of the organic binder, and adjust the fluctuation of the heat strength of the formed coke in the temperature rise process of the submerged arc furnace.

5. The solvent ethyl acetate is added to dissolve the beta resin of the asphalt, the adhesive property of the asphalt is activated at normal temperature, the formed coke is prepared by cold press molding, various defects of hot press molding are avoided, and the ethyl acetate is non-toxic and volatile, and has the characteristics of safety, non-toxicity and easy processing.

6. The raw material petroleum coke powder is dried for 2 hours at the temperature of 250-300 ℃ in advance and then pressed into balls, so that all water and most volatile components in the raw material can be removed, and the formed coke is prevented from being cracked due to too high internal vapor pressure of the volatile components when being roasted at the temperature of more than 500 ℃.

Drawings

FIG. 1 is a process flow diagram for preparing high-strength formed coke by cold press molding.

Detailed Description

Example 1:

the method for preparing the high-strength formed coke by cold press molding is characterized by comprising the following specific steps of:

(1) crushing the coke powder to a particle size of less than 3mm by using a crusher;

(2) mixing binder components, stirring and uniformly mixing, wherein the binder components comprise the following mass ratio: 0-20 parts of normal temperature binder, 60-80 parts of asphalt, 0-5 parts of asphalt modifier, 0-10 parts of formed coke strength stabilizer and 0-2 parts of starch pasting modifier;

(3) in a crusher, mixing the coke powder with the binder component, and adjusting the ratio of the coke powder to the binder component, wherein the total ratio of the binder is 8.6-10.7% of the mass of the coke powder;

(4) mixing coke powder and binder components uniformly in a mixer, adding water and steam to obtain a final material, wherein the material temperature requirement of an outlet of the mixer is 70-90 ℃, the moisture content of the final material is 8% -15%, and the moisture addition amount is not more than 15%;

(5) pressing the final material into blocks;

(6) and (5) transferring the molded final material to a drying bin for drying.

In the coke powder, the ratio of the particle size of 0.9-3mm is 40%, the ratio of 0.2-0.9mm is 30%, and the ratio of below 0.2mm is 30%.

The normal temperature binder is corn starch, the asphalt modifier is artificial graphite or boron compound, the formed coke strength stabilizer is cement or magnesium oxide, and the starch gelatinization modifier is sodium hydroxide.

The method specifically comprises the following steps: the raw materials comprise metallurgical coke powder, 20 parts of corn starch, 60 parts of high-temperature asphalt, 4 parts of artificial graphite, 10 parts of cement and 2 parts of sodium hydroxide, wherein the particle sizes of the corn starch, the asphalt, the artificial graphite and the sodium hydroxide are less than 0.15mm, the total amount of a binder is 9.6 percent of the mass of the metallurgical coke, the total amount of water is 13 percent of the mass of the metallurgical coke, the temperature in a horizontal mixer is 70 ℃, the particle size of the metallurgical coke is less than 3mm, and the molding pressure is 30-35 MPa. The drying temperature was 130 ℃. The falling strength of the formed coke is 10 times (1 m)^-1The cold strength is 1350N, and the compression strength at high temperature of 900 ℃ is 1340N. Formed coke ash14.85 percent of components, 4.96 percent of volatile components, 79.12 percent of fixed carbon and the balance of water.

Example 2: the raw materials are metallurgical coke powder, 20 parts of corn starch, 60 parts of high-temperature asphalt, 4 parts of artificial graphite and 2 parts of sodium hydroxide, the total amount of the binder accounts for 8.6 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 1. The falling strength of the formed coke is 7 times (1 m)^-1The cold strength is 1230N, and the high-temperature compressive strength at 900 ℃ is 1280N. Formed coke ash content 14.13%, volatile component 5.15%, fixed carbon 78.53%, and the balance water.

Example 3: the raw materials are metallurgical coke powder, 20 parts of corn starch, 60 parts of high-temperature asphalt, 10 parts of magnesium oxide and 2 parts of sodium hydroxide, the total amount of the binder accounts for 9.2 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 1. The falling strength of the formed coke is 8 times (1 m)^-1The cold strength is 1280N, and the high-temperature compressive strength at 900 ℃ is 1210N. 14.54 percent of formed coke ash, 5.93 percent of volatile matter, 78.26 percent of fixed carbon and the balance of water.

Example 4: the raw materials are metallurgical coke powder, 20 parts of corn starch, 60 parts of high-temperature asphalt, 4 parts of boron oxide, 10 parts of cement and 2 parts of sodium hydroxide, the total amount of the binder accounts for 9.6 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 1. The falling strength of the formed coke is 7 times (1 m)^-1The cold strength is 1320N, and the compression strength at high temperature of 900 ℃ is 1310N. Formed coke ash content 14.93%, volatile component 5.21%, fixed carbon 78.98%, and the balance water.

Example 5: the raw materials are metallurgical coke powder, 20 parts of corn starch, 80 parts of high-temperature asphalt, 5 parts of artificial graphite and 2 parts of sodium hydroxide, the total amount of the binder accounts for 10.7 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 1. The falling strength of the formed coke is 12 times (1 m)^-1The cold strength is 1460N, and the high-temperature compression strength at 900 ℃ is 1450N. 14.03 percent of formed coke ash, 5.28 percent of volatile component, 80.03 percent of fixed carbon and the balance of water.

Example 6: the raw materials are metallurgical coke powder, 20 parts of ethyl acetate and 80 parts of high-temperature asphalt, the total amount of the binder accounts for 10 percent of the mass of the metallurgical coke, the total amount of the water added accounts for 9 percent of the mass of the metallurgical coke, water vapor is not introduced into a horizontal mixer, the drying temperature is divided into 2 sections, the ethyl acetate is removed by drying at 50 ℃ for 3 hours, and then the ethyl acetate is dried at 130 ℃ for 6 hours, and the method is otherwise the same as the example 1. The falling strength of the formed coke is 14 times (1 m)^-1Cold strength of1870N, and 1860N compressive strength at 900 deg.C. 13.46% of formed coke ash, 5.04% of volatile matter, 80.72% of fixed carbon and the balance of water.

Example 7: the raw materials are metallurgical coke powder, 20 parts of ethyl acetate, 80 parts of high-temperature asphalt and 5 parts of artificial graphite, the total amount of the binder accounts for 10.5 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 6. The falling strength of the formed coke is 15 times (1 m)^-1The cold strength was 1990N and the compression strength at 900 ℃ was 1980N. 13.74 percent of formed coke ash, 4.87 percent of volatile component, 80.96 percent of fixed carbon and the balance of water.

Example 8: the raw materials are metallurgical coke powder, 20 parts of ethyl acetate, 80 parts of high-temperature asphalt and 5 parts of boron oxide, the total amount of the binder accounts for 10.5 percent of the mass of the metallurgical coke, and the rest is the same as that of the example 6. The falling strength of the formed coke is 13 times (1 m)^-1The cold strength is 1950N, and the high-temperature compression strength at 900 ℃ is 1960N. 13.76% of formed coke ash, 4.96% of volatile components, 80.83% of fixed carbon and the balance of water.

Example 9: the raw materials are petroleum coke powder, 20 parts of corn starch, 60 parts of high-temperature asphalt, 4 parts of artificial graphite, 10 parts of cement and 2 parts of sodium hydroxide, the total amount of the binder is 9.6 percent of the mass of the petroleum coke, the total amount of the water is 8 percent of the mass of the petroleum coke, and the rest is the same as example 6. If the formed coke is cracked due to too high internal vapor pressure of volatile components when being roasted at the temperature of more than 500 ℃, the raw material petroleum coke powder can be dried for 2 hours at the temperature of 250 ℃ and 300 ℃ and then pressed into balls, because all water and most of volatile components in the raw material can be removed. The falling strength of the formed coke is 7 times (1 m)^-1The cold strength is 1180N, and the compression strength at the high temperature of 900 ℃ is 1430N. Formed coke ash 2.46%, volatile matter 12.34%, fixed carbon 84.18%, and water in balance.

Example 10: the raw materials are petroleum coke powder, 20 parts of ethyl acetate, 80 parts of high-temperature asphalt and 5 parts of artificial graphite, the total amount of the binder is 10.5 percent of the mass of the petroleum coke, the total amount of the water is 8 percent of the mass of the petroleum coke, and the rest is the same as that of the example 6. The falling strength of the formed coke is 13 times (1 m)^-1The cold strength is 1830N, and the high-temperature compressive strength at 900 ℃ is 2050N. Formed coke ash content 1.43%, volatile matter 13.05%, fixed carbon 84.32%, and the balance water.

In this example, the strength index of the sample obtained is shown in Table 1.

TABLE 1 Strength index of formed coke

Name (R)	Drop Strength/time (1 m)^-1	Cold strength/N	Thermal strength/N	Ash content%	Volatile fraction/%)	Fixed carbon/%)
							Metallurgical coke powder				12.87	2.4	82.27
Example 1	10	1350	1340	14.85	4.96%	79.12
							Example 2	7	1230	1280	14.13	5.15	78.53
Example 3	8	1280	1210	14.54	5.93	78.26
							Example 4	7	1320	1310	14.93	5.21	78.98
Example 5	12	1460	1450	14.03	5.28	80.03
							Example 6	14	1870	1860	13.46	5.04	80.72
Example 7	15	1990	1980	13.74	4.87	80.96
							Example 8	13	1950	1960	13.76	4.96	80.83
Petroleum coke powder				0.3	9.69	88.52
							Example 9	7	1180	1430	2.46	12.34	84.18
Example 10	13	1830	2050	1.43	13.05	84.32%

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.

Claims

1. The method for preparing the high-strength formed coke by cold press molding is characterized by comprising the following specific steps of:

(2) mixing binder components, and uniformly stirring, wherein the binder components comprise the following mass ratio: 80 parts of high-temperature asphalt and 5 parts of asphalt modifier;

(3) preliminarily mixing the coke powder and the binder component in a crusher, and adjusting the ratio of the coke powder to the binder component, wherein the total ratio of the binder is 10.5% of the mass of the coke powder;

(4) adding a non-aqueous solvent into a mixer, and uniformly mixing the coke powder and the binder to obtain a final material, wherein the material temperature at the outlet of the mixer is 70-90 ℃, the water content of the final material is 8-15%, and the non-aqueous solvent accounts for 20 parts;

(5) pressing the final material into a block;

(6) transferring the molded final material to a drying bin for drying;

in the coke powder, the granularity of 0.9-3mm accounts for 40%, the granularity of 0.2-0.9mm accounts for 30%, and the granularity of less than 0.2mm accounts for 30%;

the asphalt modifier is artificial graphite or a boron compound, and the non-aqueous solvent is ethyl acetate;

the coke powder is metallurgical coke powder or petroleum coke powder, the granularity of the asphalt, the artificial graphite or the boron compound is below 0.15mm, the total amount of water added is 8-9% of the mass of the metallurgical coke or the petroleum coke, water is introduced into the mixer instead of water vapor, the drying temperature is divided into 2 sections, the materials are dried at 50 ℃ for 3 hours to remove ethyl acetate, and then dried at 130 ℃ for 6 hours;

the petroleum coke powder is dried for 2 hours at the temperature of 250 ℃ and 300 ℃ in advance, and then the binder and the water pressure block are added for molding;

the boron compound is one or a composition of any more of boron oxide, pyridine borane, boron carbide, borax and boric acid;

in the step (5), the final material is pressed into a block to obtain the oval wet ball.