JPH0218359B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing metallurgical coke. Attempts are currently being made in various countries around the world to improve the productivity of coke ovens and the quality of produced coke by increasing the bulk density of charged coal, or to utilize low-rank coal. In Japan, the briquette coal partial charging method is implemented on a commercial scale. This method attempts to increase the bulk density of the charged coal by molding 30% of the charged coal into briquettes, but the increase rate is only about 10%. On the other hand, in the stamping method used in Europe, the entire amount of charged coal is compressed and molded, so the bulk density of the charged coal increases significantly, reaching an increase rate of 40 to 50%. As the bulk density of the charged coal increases, the coal particles are consolidated,
The resulting coke has a dense structure, and the coke strength, particularly the abrasion strength, is significantly improved. However, if the bulk density is increased and the weight of coal per unit volume in the coking chamber is increased, the coke becomes finer. One of the reasons for this is the temperature difference between the heating wall side and the center side of the coking chamber, which leads to an increase in the so-called temperature gradient in the coal, which causes coke cracking to occur due to the increase in thermal stress due to the difference in shrinkage of semi-coke during the semi-coking process. It is possible that it will become larger. For this reason, in the case of the stamping method, which has a remarkable increase rate in bulk density, if the coke is mixed in the same way as the gravity charging, which is usually practiced, the coke becomes fine particles, making it difficult to use as coke for blast furnaces. Powdered coke is added to the coal blend to improve particle size. However, with the method of improving coke particle size by adding coke powder, the degree of improvement in coke abrasion strength decreases, and in order to prevent the reduction in coke abrasion strength due to the addition of coke powder, coke powder is finely pulverized to 0.2 mm or less. However, this method has disadvantages such as increased pulverization costs including measures to prevent dust generation. As a measure to prevent coke granulation, charging raw materials
Japanese Patent Laid-Open No. 14579/1983 describes a method in which the mixture is preheated to 300° C. or lower to reduce moisture to zero, coal-based or petroleum-based heavy oil is added, the mixture is molded, and the mixture is charged into a carbonization chamber. This method reduces the temperature difference between the wall side and the inside of the coal during carbonization by preheating the sample coal, reduces the thermal stress that causes cracks in the coke, and prevents a decrease in coke particle size. It is something. However, this method has not yet been implemented in commercial-scale equipment for mass processing, and there are problems such as increased raw material costs due to the addition of heavy oil and smoke and ignition when charging into the carbonization chamber. There are drawbacks such as: The object of the present invention is to provide a method for producing metallurgical coke that does not have these drawbacks. Compared to gravity charging, which is normally charged from the top of the furnace, block-shaped briquette coal has a bulk density that is 40 to 50% higher, and the cracks generated during the semi-coking process become larger, resulting in finer coke particles. As a result of intensive research to achieve the purpose of the present invention, the inventors of the present application have determined that the sum of inert components and mineral substances in the total coal (hereinafter referred to as total It was discovered that a method for adjusting the inert (abbreviated as "inert") is effective, and based on this knowledge, the present invention was achieved. However, vitrinite, which is anthracite coal, does not expand or contract when heated, so it was included as an inert component in the coal. According to the present invention, by adjusting the sum of inert components and mineral substances (term used in the JIS M8816-1979 standard) in the blended coal, the coke particle size can be improved without sacrificing the improvement in coke wear strength. Therefore, it is possible to use a large amount of coal types containing many inert components, such as Canadian coal, Australian coal, and South African coal. The above-mentioned inert components in coal mean those components that do not expand or contract when the coal is heated.In addition to the vitrinite of the anthracite mentioned above, this includes inertinites of the maceral group of coal. Inertinites include miclinites, sclerotinites, fujinites, and semifujinites. Since the inert components and minerals in coal have smaller expansion and contraction during heating, the coal blend with more total inert has a higher thermal stress generation factor, as shown in Figure 1.
It is possible to reduce the linear linear contraction coefficient β ₁ of semi-coke, which is considered to be one of the most important factors. However, inert components and mineral substances in the coal are factors that reduce the fluidity of the coal blend, so if the total inert content is too large, the fusion bond between the coal particles becomes poor and the coke strength decreases. The bulk density of charged coal in gravity charging is 0.70 to 0.80 wet tons/ ^m3 , which is approximately 1/2 lower than the coal true specific gravity of 1.3 to 1.4 dry g/ ^cm3 , so the distance between coal particles is In order to promote melt adhesion between particles in order to obtain hard lump coke, the fluidity of the blended coal is generally controlled to be 200 ddpm or more as measured by the Giesler plastometer. Inert is 20-25Vol%. On the other hand, for block-shaped briquette coal with a bulk density of 1.0 wet ton/m ³ or more, preferably 1.15 wet ton/m ³ or more, the bulk density increases by 40 to 50% compared to gravity charging. The distance between particles is shortened, and the amount of adhesive component can be reduced. As a result, even if the total inert in the total coal to be blended is increased to 27 to 35 Vol%, it is possible to obtain higher coke strength compared to gravity charging, and the coke particle size can be reduced without sacrificing the improvement in coke strength. Improvements can be made. The reason for setting the total inert to 27 to 35 Vol% is that as shown in Figure 2, when the total inert is 27 Vol% or less, the increase in coke particle size is small, and when the total inert is 35 Vol% or more, the melting and adhesion of coal particles is insufficient. This is because the strength of coke is significantly reduced. There are no particular restrictions on the particle size of pulverized coal, and from the economic point of view, gravity charging is usually sufficient, but coal with a particularly large amount of total inert should be pulverized to 2 mm or less. Also, coke powder, petroleum coke and volatile content 10
Even when adding an inert material (component) such as char, which shows an amount of less than 20% by volume, it can be blended so that the sum of these inert materials and the total inert of the coal maceral is 27 to 35 Vol%. Example Using raw coal having the properties shown in Table 1, a blended coal with a pulverized particle size of -3 mm85 and a total moisture content of 10% was used, and the molding pressure was
The coal was compression molded at 100 kg/cm ² to form a cylindrical block shaped coal with a total weight of 10 kg, which was placed in an iron retort and carbonized at a maximum temperature of 1000°C in an externally heated electric furnace to measure the coke particle size and strength. The maceral group was measured in accordance with the JIS method, and the total inert was calculated as shown in formula (A). Total inert = (Fujinite) + 2/3 (Semi-Fujinite) + (Mikulinite) + (Sclerotinite) + (Mineral matter)……(A
) The primary linear shrinkage coefficient of semi-coke is measured using a Shimadzu thermomechanical analyzer (1) Adjust the sample particle size to 100mesh or less and total moisture to 10%. (2) Pressurize the sample from (1) above to a diameter of 7ψmm and a length of 5mm.
A test piece is obtained by molding it to a thickness of ~6 mm. (3) The test piece obtained in (2) above is set in a measuring device and heated to 800°C in a nitrogen gas stream while applying a load. (4) The semi-coke linear shrinkage coefficient β ₁ is calculated as shown in equation (B). β ₁ = 1/l ₀ (dl/dt)/(dθ/dt) −(B) l ₀ ... Sample length dl at solidification point ... Length change dt ... Time change dθ ... Temperature amount of change

【table】

[Table] The results are shown in Table 2. In the case where the total inert in block shaped coal shows 20 to 25 Vol%, which is similar to gravity charging, although the coke strength D ¹⁵⁰ ₁₅ is improved compared to gravity charging, the coke grains become significantly finer. It's getting better. Furthermore, in the case of case, the reason why the coke strength DI is lower than that of gravity charging ( ) is because the upper limit of total inert according to the present invention is exceeded. The total inert of the present invention is 27~35Vol%
In case 2, the coke particle size has greatly increased, and the coke strength D ¹⁵⁰ ₁₅ is also excellent compared to the gravity charging bulk density of case 0.75 wet Kg/.

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a graph showing the relationship between total inert and semi-coke linear shrinkage coefficient.The horizontal axis shows the volume % of total inert, and the vertical axis shows semi-coke linear shrinkage coefficient _β1.Figure 2 shows the relationship between total inert and semi-coke linear shrinkage coefficient. This is a graph showing the relationship between coke particle size and coke strength, where the horizontal axis shows the volume % of total inert, the vertical axis (left) shows the average particle size of coke, and the vertical axis (right) shows coke strength.

Claims (1)

[Claims] 1 In the method of forming coal blend into a block with a size slightly smaller than that of an indoor furnace to give a bulk density of 1.0 wet tons/m ² or more and then charging it into an indoor furnace and carbonizing it, the inert components of the total coal to be blended are and the sum of minerals is 27~
A method for producing metallurgical coke, characterized by blending coal so that it becomes 35 Vol%.