CN115820953B - Blast furnace coal injection and blending method containing coke powder and waste plastics - Google Patents

Abstract

The invention discloses a method for blowing coal and blending coal from a blast furnace containing coke powder and waste plastics, belonging to the technical field of fuel blowing from the blast furnace; the blast furnace injection coal comprises, by weight, 30-50% of anthracite, 0-50% of bituminous coal, 10-30% of coke powder and 10-20% of waste plastics; firstly, mixing and crushing anthracite, bituminous coal and coke powder to prepare total coal powder, granulating waste plastics to form particles with the granularity of less than 10 mm, and uniformly mixing the treated waste plastics with the total coal powder to obtain blast furnace injection coal; the invention uses the coke powder and the waste plastics to be added into the mixed coal, can ensure low cost and low volatile matters, and simultaneously improves the heating value, and has higher cost performance.

Description

Blast furnace coal injection and blending method containing coke powder and waste plastics

Technical Field

The invention belongs to the technical field of blast furnace injection fuel, and particularly relates to a blast furnace injection coal containing coke powder and waste plastics and a coal blending method.

Background

The steel production is an industry with high energy consumption and high pollution, and is also an industry with maximum energy conservation and emission reduction potential. Along with the continuous strict requirements of the nation on energy conservation and emission reduction in the steel industry and the continuous increase of the pressure of iron making cost of enterprises, optimizing the efficiency of a blast furnace becomes an important way for improving the competitiveness of the steel enterprises, and mainly comprises methods of reducing fuel consumption, reasonable fuel structure and the like. The main means for increasing the coal injection amount of the blast furnace and reducing the coke ratio are all countries in the world, which are used for reducing the pig iron cost and the environmental pollution. In China, the blast furnace coal injection ratio still has a certain lifting space. Increasing the coal injection amount of the blast furnace, saving coke and reducing the iron-making cost become urgent tasks and important research subjects at present. Therefore, it is necessary to use the pulverized coal injected from the blast furnace to partially replace the coke. The coal injection of the blast furnace is an important technical measure for reducing the production cost and improving the economic benefit of the modern blast furnace. Can relieve the shortage of coking coal in China, optimize the energy structure of an iron-making system, and reduce the pollution of coking to the environment.

The coal injection of the blast furnace is an effective measure for increasing iron and saving coke, and the performance of the coal for injection has close relation with the effective degree of the measure, so the research on the performance of the coal dust is very important. The main purpose of blast furnace coal dust injection is to replace metallurgical coke, so that the type and physical and chemical properties of the injected coal dust are required. Coal for blast furnace injection can be theoretically injected by using all coal types, but at present, strongly caking coal can be used for coking, is quite rare, and the use of the coal injection can cause the coking of tuyeres and the damage of equipment, so non-caking coal or weakly caking coal, such as: anthracite, bituminous coal, lean coal and the like, three coal blending modes are generally used in the existing coal injection technology, and the coal blending modes are as follows: anthracite coal injection, bituminous coal injection and coal blending injection.

The anthracite has high heat value and theoretical replacement ratio, good safety, is the preferred coal for injection of blast furnaces in China, but has lower volatile content, higher ignition point, low combustion speed and poorer combustibility. Especially, in the high coal ratio injection, the ratio of unburned coal powder is greatly increased, so that the smooth running of a blast furnace is affected, and the replacement ratio is reduced, so that the maximum injection amount of anthracite is low, and the high coal ratio injection is difficult to realize by single injection of anthracite. Compared with anthracite, the anthracite has higher volatile component content, low ignition point, good combustibility and higher grindability index, and is favorable for expanding the blowing quantity in theory. However, in the blast furnace smelting environment, the heat value and the theoretical replacement ratio of the bituminous coal are lower than those of the anthracite coal, and the injection is single. High volatile bituminous coals also suffer from certain drawbacks such as: the bituminous coal has high explosiveness and potential safety hazard; the injection of a large amount of bituminous coal reduces the theoretical combustion temperature, resulting in uneven temperature distribution in the furnace. At present, the blast furnace injection coal mainly adopts a mixed coal blending scheme of bituminous coal and smokeless coal, and the method has the advantages that: firstly, due to the mutual catalysis among different pulverized coal, the combustion rate of mixed coal has an increasing trend compared with that of single pulverized coal; secondly, the increase of the proportion of the bituminous coal can reduce the hydrogen content in the blast furnace, reduce the cohesiveness of the coal gas, improve the diffusion speed and the reaction speed, strengthen the indirect reduction reaction in the blast furnace, thereby effectively improving the utilization coefficient of the blast furnace and reducing the fuel ratio; thirdly, after a certain amount of anthracite is added into the bituminous coal, the defect that a spray gun and a tuyere are easy to coke and block or burn when the bituminous coal is singly blown can be overcome, and the problem of explosiveness when the bituminous coal is blown can be effectively solved; fourth, compared with anthracite, the bituminous coal has wider distribution range, larger reserves and lower price, and the mixed coal is beneficial to reducing the cost. However, with the increasing demand of steel, high-quality anthracite is in demand, and many ironmaking enterprises are seeking a coal blending scheme with lower price, more environmental protection and heating value reaching the ironmaking demand.

The coke powder is a by-product which is produced in the production and subsequent use processes of the coke, and in China, more than 1600 ten thousand tons of coke powder can be produced in the production process of the coke every year. The volatile components are lower, the safety in the use process is high, the fixed carbon content is higher and can basically reach more than 70%, and only the ash content and the sulfur content are higher, so that the carbon source is a high-quality carbon source. The coke powder has a lower recovery price due to its less functionality than coke, anthracite, etc. Therefore, the coke powder can be used in the blast furnace blowing direction to replace a part of anthracite, and the combustion characteristic of the coal powder is improved. The coke powder has the following advantages of replacing anthracite: firstly, the digestion capability of the coke powder can be increased, and the application field of the coke powder is expanded; secondly, the dosage of anthracite is reduced, and precious coking coal resources are saved; thirdly, the method accords with the current energy saving and emission reduction strategy of China; fourth, the low price of the coke powder can promote the economic benefit of downstream enterprises. Therefore, the addition of the coke powder can bring good economic and environmental benefits to enterprises and society.

In order to reduce the dependence on metallurgical coke and thus carbon dioxide emissions, researchers have proposed the following methods: (1) replacing the coke with a hydrogen-rich carbon-containing material; (2) producing agglomerates using a secondary resource; (3) the reduction process of the ferric oxide is changed to low-carbon utilization.

The increase in the yield of plastics in modern society directly leads to the formation of large amounts of waste, which is not only difficult to dispose of but also presents a certain hazard to the environment. The main chemical components of the waste plastics are high molecular hydrocarbon compounds, which can generate higher heat energy and chemical energy after combustion, so the waste plastics are added into the coal for blast furnace injection to recycle and reduce the wasteAn efficient way of carbon dioxide emission. The hydrogen-rich carbon-containing waste material is used for partially replacing a small part of coal dust, so that the dependence on coal resources can be reduced and CO can be effectively reduced ₂ And (5) discharging. According to statistics, the comprehensive utilization rate of the waste plastics after incineration treatment is 30%, and the material loss is up to 70%; the comprehensive utilization rate of waste plastics in the power generation process is only 40%, and the material loss degree is as high as 60%; however, if the waste plastics are used in the aspect of blast furnace injection, the comprehensive utilization rate of the waste plastics is as high as 79.6%, and the material loss is reduced to 20.4%. However, there are few reports of adding waste plastics to blast furnace injection coal, and they have not been used in industry.

Plastics can be classified into thermoset plastics and thermoplastic plastics. Among them, thermosetting plastics mainly composed of polyurethane and epoxy resin cannot be reprocessed due to crosslinking and curing, and cannot be recycled by recycling, so that the thermosetting plastics have become the most harmful plastic type to the environment at present.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a method for blowing coal and blending coal by a blast furnace containing coke powder and waste plastics. So as to provide higher theoretical heat value for blast furnace injection coal blending and alleviate the disposal problem of waste plastics.

In order to achieve the above purpose, the present invention is realized by the following technical scheme.

The blast furnace coal injection comprises 30-50% of anthracite, 0-50% of bituminous coal, 10-30% of coke powder and 10-20% of waste plastics by weight percentage.

Preferably, the waste plastic is waste epoxy resin or waste polyurethane plastic.

More preferably, the waste epoxy resin has a moisture content of 5% -20%, a volatile content of 70% -90%, an ash content of 3% -10%, a sulfur content of <0.1% and a fixed carbon content of 5% -15%; the waste polyurethane plastics have the moisture content of 5% -20%, the volatile content of 70% -90%, the ash content of 5% -15%, the sulfur content of <0.2% and the fixed carbon content of 5% -15%.

Preferably, the particles with the particle size smaller than 2.0 and mm in the total pulverized coal obtained by mixing anthracite, bituminous coal and coke powder account for more than 90% of the total pulverized coal.

Preferably, the particle size of the waste plastic is < 10 mm.

Preferably, the material consists of 40% of anthracite, 30% of bituminous coal, 20% of coke powder and 10% of waste plastics by weight percentage.

Preferably, the bituminous coal has a moisture content of 10% -20%, a volatile content of 10% -40%, an ash content of 5% -15%, a sulfur content of <1.0% and a fixed carbon content of 50% -80%.

Preferably, the moisture content of the coke powder is 0.1% -5%, the volatile content is 1% -5%, the ash content is 11% -15%, the sulfur content is 0.5% -1.5%, and the fixed carbon content is 80% -90%.

Preferably, the anthracite coal has a moisture content of 10% -20%, a volatile content of 5% -15%, an ash content of 5% -15%, a sulfur content of <0.8% and a fixed carbon content of 75% -85%.

The moisture content of coal refers primarily to the free water content. The volatile matter is a mixed gas composed of various hydrocarbon compounds, hydrogen, carbon monoxide and the like, the volatile matter content decreases with increasing degrees of coalification, and the higher the volatile matter is, the more explosive the coal is. Ash is the residue left after the coal is completely combusted, and mainly comes from non-combustible minerals of coal types, and the minerals need to consume heat during combustion, so that the higher the ash content is, the more unfavorable the combustion efficiency of coal injection is, ash slag generated by coal combustion is increased, and the discharged fly ash is also increased. The fixed carbon is a main source of the calorific value of the coal, the fixed carbon content in the coal can be increased along with the increase of the deterioration degree of the coal, and the coal with high fixed carbon content has stronger combustion performance and more calorific value. The higher sulfur content coal is more lost to equipment after combustion and pollutes the environment, so the sulfur content in the mixed coal needs to be reduced as much as possible in the process of blending the coal in the blast furnace.

The anthracite coal uses the anthracite coal type selected by most ironworks, for example: jincheng anthracite.

The bituminous coal uses the bituminous coal type selected by most ironworks, for example: shanxi dazhang coal.

The coke powder is selected from most ironworks, for example: coke powder of Shanxi Luan auspicious coking Co.

A coal blending method for blast furnace injection coal containing coke powder and waste plastics comprises the following steps:

1) Firstly, mixing anthracite, bituminous coal and coke powder, adding the mixture into a mill, and crushing the mixture into mixed coal powder;

2) Granulating the waste plastics by using a cold state method to form particles with the granularity of less than 10 mm;

3) And uniformly mixing the treated waste plastics with mixed coal dust to obtain blast furnace injection coal.

Preferably, the cold state granulation is performed by mechanically processing, extruding and cutting waste plastics.

Compared with the prior art, the invention has the following beneficial effects:

(1) The invention plays the synergistic combustion effect of the coke powder, the anthracite and the bituminous coal; the method for blowing coal and blending coal in the blast furnace has the advantages of high heat, low sulfur, high fixed carbon content and low price of the coke powder.

(2) Since combustion occurs at the surface with a cracked structure, whereas existing aggregates of waste have a dense core structure, their conversion is lower despite the higher total porosity; the invention selects the porous small-particle waste epoxy resin, which has larger specific surface area and better combustibility. The combustion rate of the injection waste plastics selected by the invention is higher than that of the injection coal. The burning rate of the pulverized coal is about 55%, and the burning rate of the waste plastic can reach about 80%. The coke powder and the waste plastics are added into the mixed coal, so that the heat productivity can be improved while the cost and the volatile component are low, and the cost performance is higher.

(3) The invention adopts the waste plastic with less mixing amount, reduces volatile components and is safer to operate.

Drawings

FIG. 1 is an SEM image of anthracite coal used in all embodiments of the invention; wherein (1 a) has a magnification of 5000 times and (1 b) has a magnification of 10000 times.

Fig. 2 is an SEM image of bituminous coal used in all examples of the present invention, wherein (2 a) is at 5000 times magnification and (2 b) is at 10000 times magnification.

Fig. 3 is an SEM image of the coke breeze used in all the examples of the present invention, wherein (3 a) and (3 b) are magnified 10000 times.

Fig. 4 is an SEM image of the coal blend of the coal blending scheme of example 1 of the present invention, wherein (4 a) is at 5000 times magnification and (4 b) is at 15000 times magnification.

Fig. 5 is an SEM image of the waste epoxy resin used in example 4 of the present invention, wherein (5 a) is at 5000 times magnification and (5 b) is at 10000 times magnification.

Fig. 6 is an SEM image of the waste polyurethane used in example 5 of the present invention, wherein (6 a) is at 5000 times magnification and (6 b) is at 10000 times magnification.

Fig. 7 is an SEM image of the coal blend of the coal blending scheme of example 4 of the present invention, wherein (7 a) is at 5000 times magnification and (7 b) is at 10000 times magnification.

Fig. 8 is an SEM image of the coal blend of the coal blending scheme of example 5 of the present invention, wherein (8 a) is at 5000 times magnification and (8 b) is at 10000 times magnification.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail by combining the embodiments and the drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. The following describes the technical scheme of the present invention in detail with reference to examples and drawings, but the scope of protection is not limited thereto.

Various physicochemical properties and prices of anthracite, bituminous coal, coke powder, waste epoxy resin and waste polyurethane are shown in table 1. Wherein M is _ad Represents the total moisture content, A _ad Representing ash content, V _ad Representing volatile content, FC _ad Represents the fixed carbon content, S represents the sulfur content, wherein the calorific value is calculated by theoryThe calculated data will deviate from the measured calorific value to some extent. The ratio of the coke powder of example 1, example 2 and example 3 to the anthracite coal is different and is 40% of the mass of the anthracite coal, because the safety is ensured. The scheme of blending coal by using the waste epoxy resin has higher cost performance and reaches higher heating value with lower price; and the volatile components of the waste polyurethane can be reduced by using the waste polyurethane, so that the safety of the coal injection process is improved. The price of each material is based on the current average market price.

Table 1:

example 1

Coke powder, anthracite and bituminous coal are mixed according to the mass ratio of 20:50:30, as a first coal blending scheme, adding the mixed coal into a mill for crushing, wherein the grain size of coal powder is less than 2.0 and mm and accounts for more than 90%, and using a blast furnace injection system for injection, compared with anthracite injection, the purchasing cost can be reduced by 614 yuan/ton, and the calorific value is improved by 71 kcal/kg, and the specific numerical values are shown in table 2.

The morphology test is carried out on the raw coal and the coal blending scheme of the embodiment, and the result is as follows:

as shown in fig. 1, the anthracite powder has a blocky shape with uneven size, and the surface of the anthracite powder is rough; in fig. 2, the bituminous coal exhibits smaller block and plate shapes; in fig. 3, the coke powder exhibits a smooth-surfaced lump and flake morphology due to its passing through the pyrolysis process; in fig. 4, it can be seen that anthracite, bituminous coal and coke powder are uniformly dispersed, which meets the coal blending requirement of blast furnace injection.

Example 2

Coke powder, anthracite and bituminous coal are mixed according to the mass ratio of 15:55:30, as a second coal blending scheme, adding the mixed coal into a mill for crushing, wherein the particle size of pulverized coal is more than 90 percent of that of 2.0 and mm, and using a blast furnace injection system for injection. Compared with anthracite injection, the anthracite injection can reduce the purchase cost by 533 yuan/ton, and improve the calorific value by 31 kcal/kg, and the specific values are shown in Table 2.

Example 3

The coke powder, anthracite and bituminous coal are mixed according to the mass ratio of 10:60:30, as a third coal blending scheme, adding the mixed coal into a mill for crushing, wherein the particle size of pulverized coal is more than 90 percent of that of 2.0 and mm, and using a blast furnace injection system for injection. Compared with anthracite coal injection, the purchasing cost 453 yuan per ton can be reduced, but the heat value is reduced, and the specific values are shown in Table 2.

Table 2:

example 4

Anthracite and bituminous coal are first mixed according to the proportion of 50:30, and pulverizing in a mill, wherein the particle size of pulverized coal is less than 2.0 and mm and more than 90%. The waste epoxy resin is mechanically processed, extruded and cut into particles with the granularity of less than 10 mm, and then the particles are mixed with anthracite and bituminous coal, and the mixture is blown by a blast furnace blowing system. Wherein, the proportion of waste plastics, anthracite and bituminous coal is 20:50:30. compared with anthracite coal injection, the anthracite coal injection can reduce the purchase cost by 434 yuan/ton, and improve the calorific value by 704 kcal/kg, wherein the specific values are shown in Table 3.

Morphology tests are carried out on the waste epoxy resin and the coal blending scheme of the embodiment, and the results are as follows:

as shown in fig. 5, the waste epoxy resin is formed by stacking small blocks, and the surface is smoother; as shown in fig. 7, after the waste epoxy resin was added to the coal blending scheme of this example, the coal particles and the waste epoxy resin powder were uniformly distributed, indicating that the two were successfully mixed and the particles were smaller, and blast furnace injection was possible.

Example 5

Anthracite and bituminous coal are first mixed according to the proportion of 50:30, and pulverizing in a mill, wherein the particle size of pulverized coal is less than 2.0 and mm and more than 90%. The waste polyurethane plastics are mechanically processed, extruded and cut into particles with the granularity of less than 10 mm, and then are mixed with anthracite and bituminous coal, and are blown by a blast furnace blowing system. Wherein, the proportion of the waste polyurethane plastics, anthracite and bituminous coal is 20:50:30. compared with the anthracite injection, the purchasing cost can be reduced by 214 yuan/ton, the calorific value is improved by 521 kcal/kg, the cost is increased compared with that of the embodiment 4, but the volatile component is reduced, and the safety of a coal blending scheme based on the addition of waste polyurethane plastics is improved, wherein the specific numerical values are shown in the table 3.

Morphology tests are carried out on the waste polyurethane plastics and the coal blending scheme of the embodiment, and the results are as follows:

as shown in fig. 6, the waste polyurethane plastics have different block shapes, wherein the small particles are most so as to be in full contact with oxygen; as shown in fig. 8, after the waste polyurethane plastics are added into the coal blending scheme of the embodiment, the waste polyurethane plastics and coal particles are uniformly distributed, and small particles of the waste polyurethane plastics provide a specific surface area fully contacted with oxygen during combustion, so that the combustion performance of the mixed coal is enhanced, and the requirements of blast furnace injection are met.

Table 3:

example 6

Anthracite, bituminous coal and coke powder are mixed according to a proportion of 40:30:20, and pulverizing in a mill, wherein the particle size of pulverized coal is less than 2.0 and mm and more than 90%. The waste epoxy resin is mechanically processed, extruded and cut into particles with the granularity of less than 10 mm, and then the particles are mixed with anthracite, bituminous coal and coke powder, and the mixture is blown by a blast furnace blowing system. Wherein, the proportion of waste plastics, anthracite, bituminous coal and coke powder is 10:40:30:20. compared with anthracite coal injection, the anthracite coal injection can reduce the purchase cost by 686 yuan/ton, and the lifting heat value is 466 kcal/kg, and the specific values are shown in Table 4.

Example 7

Anthracite, bituminous coal and coke powder are mixed according to a proportion of 40:30:20, and pulverizing in a mill, wherein the particle size of pulverized coal is less than 2.0 and mm and more than 90%. The waste polyurethane plastics are mechanically processed, extruded and cut into particles with the granularity of less than 10 mm, and then are mixed with anthracite, bituminous coal and coke powder, and are blown by a blast furnace blowing system. Wherein, the proportion of waste polyurethane plastics, anthracite, bituminous coal and coke powder is 10:40:30:20. compared with anthracite injection, the anthracite injection can reduce the purchase cost by 576 units/ton, and improve the heat value by 374 kcal/kg, and the specific values are shown in Table 4.

Table 4:

in Table 4, the blending schemes of examples 6 and 7 have less than 21% of volatile components, and have certain safety, and the cost is reduced compared with anthracite coal injection, the calorific value is increased, the sulfur content is obviously reduced, and the blending scheme can utilize waste plastics and is environment-friendly and greatly enhanced.

While the invention has been described in detail in connection with specific preferred embodiments thereof, it is not to be construed as limited thereto, but rather as a result of a simple deduction or substitution by a person having ordinary skill in the art to which the invention pertains without departing from the scope of the invention defined by the appended claims.

Claims (7)

1. The blast furnace injection coal containing the coke powder and the waste plastics is characterized by comprising, by weight, 30-50% of anthracite, 0-50% of bituminous coal, 10-30% of coke powder and 10-20% of waste plastics; the waste plastic is waste epoxy resin or waste polyurethane plastic; particles with the particle size smaller than 2.0 and mm in the total pulverized coal obtained by mixing anthracite, bituminous coal and coke powder account for more than 90% of the total pulverized coal; the particle size of the waste plastic is less than 10 mm.

2. The blast furnace injection coal containing coke powder and waste plastics according to claim 1, wherein the waste epoxy resin has a moisture content of 5% -20%, a volatile content of 70% -90%, an ash content of 3% -10%, a sulfur content of <0.1% and a fixed carbon content of 5% -15%; the waste polyurethane plastics have the moisture content of 5% -20%, the volatile content of 70% -90%, the ash content of 5% -15%, the sulfur content of <0.2% and the fixed carbon content of 5% -15%.

3. The blast furnace injection coal containing coke powder and waste plastics according to claim 1, wherein the blast furnace injection coal is composed of 40% of anthracite, 30% of bituminous coal, 20% of coke powder and 10% of waste plastics by weight percentage.

4. The blast furnace injection coal containing coke breeze and waste plastics according to claim 1, wherein the bituminous coal has a moisture content of 10% -20%, a volatile content of 10% -40%, an ash content of 5% -15%, a sulfur content of <1.0% and a fixed carbon content of 50% -80%.

5. The blast furnace injection coal containing coke powder and waste plastics according to claim 1, wherein the moisture content of the coke powder is 0.1% -5%, the volatile content is 1% -5%, the ash content is 11% -15%, the sulfur content is 0.5% -1.5%, and the fixed carbon content is 80% -90%.

6. The blast furnace injection coal containing coke powder and waste plastics according to claim 1, wherein the anthracite coal has a moisture content of 10% -20%, a volatile content of 5% -15%, an ash content of 5% -15%, a sulfur content of <0.8% and a fixed carbon content of 75% -85%.

7. A method for blending coal by blast furnace injection comprising coke breeze and waste plastic according to any one of claims 1 to 6, comprising the steps of:

1) Firstly, mixing anthracite, bituminous coal and coke powder, adding the mixture into a mill, and crushing the mixture into mixed coal powder;

2) Granulating the waste plastics by using a cold state method to form particles with the granularity of less than 10 mm;

3) And uniformly mixing the treated waste plastics with mixed coal dust to obtain blast furnace injection coal.

Images