JPS6241284A - Production of chrome-containing coke - Google Patents

Abstract

PURPOSE:To obtain chrome-contg. coke which exhibits an excellent reducing reaction promoting action etc., and is suitable for production of ferrochromium, by intimately mixing a chrome are powder with a raw material for production of coke and feeding the intimate mixture into a coke oven, followed by carbonization. CONSTITUTION:45wt% or less chrome are powder is intimately mixed with a raw material for production of coke. The intimate mixture is fed into a coke oven, followed by carbonization, thereby obtaining an intended chrome- contg. coke. Alternatively, a chrome-contg. coke may also be prepared by mixing a raw material for production of coke with 45wt% or less chrome ore powder and a binder (e.g., polyvinyl alcohol), molding the mixture and carbonizing the molding in a coke over. In the chrome-contg. coke thus obtd., the chrome component is tightly and integrally united with the coke. Therefore, when it is used as a raw material of reduction treatment, the reducing reaction is advantageously promoted as compared with the case where the reducing reaction is conducted by the conventional method in which coke and chrome ore are each used in the form of a single material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel method for producing chromium-containing coke that can be suitably used for producing ferrochrome, producing chromium-containing hot metal, and the like.

[Conventional technology]

Unless special manufacturing methods are used, a ferrochrome master alloy is often used as the chromium source when producing chromium-containing hot metal. To produce this ferrochrome, an electric furnace (submerged arc furnace) is used, and chromium-containing raw materials (consisting essentially of chromium oxide and iron oxide), coke, and flux are charged into the electric furnace and melted. Usually, a molten ferrochrome metal is obtained by reduction treatment. In this case, as the raw material to be charged into the electric furnace, sintered ore, calcined pellets, or semi-reduced pellets are manufactured by the manufacturing method described in the first step, and these are charged into the electric furnace singly or in combination. is usually done.

(a) Manufacturing method of sintered ore: Blend chromite ore powder with coke powder as a fuel, limestone as a flux, silica sand, etc., and charge it into a sintering machine.
Ignite coke powder to obtain sintered ore.

Yama), Manufacturing method for fired pellets Mix limestone as a flux with chromite powder as necessary, grind the ore using a ball mill etc. to obtain green balls with sufficient strength, and then process as needed. After adding a binder and the like as appropriate, green balls are formed using a granulating device such as a polling disk, and the green balls are fired using pellet firing equipment to obtain fired pellets.

(C), Manufacturing method for semi-reduced pellets Mix chromite powder with coke powder as a reducing agent and limestone as a flux if necessary, and use a ball mill etc. to obtain green balls with sufficient strength. After polishing the ore, binder is added as necessary, and green balls are formed using a granulating device such as a polling disk.

The coke powder is heated at a temperature below the ignition temperature of coke powder, dried and dehydrated to obtain dry pellets, and the dried pellets and granular coke as an externally charged reducing agent are charged into, for example, a heavy oil-burning rotary kiln.

While the dried pellets are being transferred in this kiln, the chromite in the dried pellets is partially reduced to obtain semi-reduced pellets.

Thus, in the production of conventional ferrochrome.

In addition to the coke charged into the electric furnace, a large amount of coke is consumed as a fuel or as a reducing agent during the production of sintered ore and semi-reduced pellets as charging raw materials.

Furthermore, when producing chromium-containing hot metal using a special method, the use of coke as a heat source and reducing agent is generally indispensable.

[Problem that the invention seeks to solve]

In the conventional production of ferrochrome, the coke used to produce chromium-containing hot metal was treated as a separate substance group from chromium ore, and was not integrated. This required much greater coke consumption than the net amount of coke required for true chromium reduction.

Particularly in recent years, the use of semi-reduced pellets has increased in order to reduce energy costs and lighten the load on electric furnace ironmaking. Since it is essential to use a large amount of coke, and a large amount of granular coke is charged even in electric furnaces, reducing the consumption of this coke has become a major issue.

In -a, the coke is used to reduce the chromium ore, but this is all about causing the reduction reaction of chromium oxide and iron oxide in the chromium ore with solid carbon, which is the main component of the coke. Therefore, in order for this reduction reaction to proceed advantageously, it is necessary that the chromium ore particles and the solid carbon particles in the coke be in a close state.

However, in the conventional manufacturing process, coke is simply mixed mechanically as a separate substance from chromium ore, which requires an excessive amount of coke to carry out a sufficient reduction reaction, reducing coke consumption. There were limits to what could be done.

The present invention aims to solve such problems.

[Means to solve problems]

As a solution to effectively achieve this object, the present invention provides a method for producing coke for steelmaking in which raw materials for coke production are charged into an ordinary coke oven and subjected to dry distillation, in which up to 45% by weight of the raw materials for coke production are added. Mix chromium ore powder up to
A method for producing chromium-containing coke characterized by dry distilling this mixture in a coke oven, and a method for producing coke for steelmaking in which raw materials for coke production are charged into a coke oven and subjected to dry distillation. The present invention provides a method for producing chromium-containing coke, which comprises mixing up to 45% by weight of chromium ore powder with a raw material together with a binder, molding the mixture, and subjecting the molded product to dry distillation in a coke oven.

The content of the present invention will be specifically explained below.

The present invention is characterized in that chromium ore is allowed to coexist in a dispersed state in the charging coal for scraping during the dry distillation process of coke in a coke oven. By performing this dry distillation process, chromium oxide and iron oxide are partially reduced and chromium-containing coke in which these are tightly integrated is obtained.

Substantially any coke oven can be used to carry out the method of the present invention. Various types of coke ovens are known, but in the production of coke for blast furnaces, basically, coal for carcass is charged into a coking chamber that has two combustion chambers on both sides. Heat from room temperature to a maximum of 1000-1350℃, 1
The dry distillation treatment takes 0 to 30 hours. Charging coal, which is a raw material for coke, is usually a combination of several brands or dozens of brands with low-volatile coal added, heavy oil, etc. added as necessary, and most of it is crushed to a size of 31 or less. is used. In this case, the red-hot coke that has undergone dry distillation is taken out of the carbonization chamber (there are methods such as extruding it with an extruder or dropping it by gravity from a sloped floor) and leading it to a fire extinguishing tower where it is extinguished and cooled with water spray, or it is inert. Usually, it is cooled by gas cooling, etc., and the particle size is adjusted using a coke cutter. In the present invention, while utilizing such conventional coke manufacturing method as it is,
Chromium-containing coke can be produced.

In carrying out the present invention, chromite powder ore is blended with the conventional raw material for coke production up to a maximum of 45% by weight. In this case, coarse particles mixed in the chromite powder ore are removed by sieving or crushed before use.

The presence of coarse particles reduces the strength of the produced chromium-containing coke. There is a limit to the blending ratio of chromium powder ore due to the strength of the chromium-containing coke that is produced, and in order to obtain a product with strength equal to or higher than that of commercially available compacted coal, a maximum of 45% by weight is required. It is necessary to do up to The chromium-containing coke obtained by the method of the present invention requires high strength when it is planned to be charged into a blast furnace, but it can be advantageously applied as a charging material for electric furnaces and other electric furnaces other than blast furnace charging. In many cases, it is sufficient that the strength is stronger than that of small charcoal.As shown in the results in FIG. Mixed with up to 45% by weight of chromium powder ore.

It can also be obtained by charging this mixture into a coke oven and subjecting it to dry distillation treatment. Furthermore, as shown in the results in FIG. 1, in order to obtain chromium-containing coke with better strength, it is desirable to charge the coke into a coke oven in the form of briquettes. In this case.

By blending up to 45% by weight of chromium powder ore with ordinary raw materials for coke production, and adding an appropriate amount of binder,
It is preferable to mix the mixture with or without heating to a temperature sufficient to disperse the binder, form the mixture (briquette), and charge it into a coke oven. Various binders can be used, but polyvinyl alcohol-based binders are preferred.

The dry distillation temperature and dry distillation time also affect the strength of the obtained chromium-containing coke, and also have a large effect on the reduction rate of chromium ore. In the present invention, the chromium ore is reduced and the presence of reduced chromium and iron in the coke is advantageous in achieving the above-mentioned objectives. As shown in Example 2 below, the maximum temperature during dry distillation was set to about 12
When the temperature is 00°C or higher, it is possible to reduce more than half of the chromium oxide to metallic chromium, although this is related to the blending ratio of the chromium powder ore. In addition, if the maximum dry distillation temperature is the same, the reduction rate will also change depending on the time maintained at this maximum temperature.
The longer the retention time, the higher the reduction rate. When the maximum dry distillation temperature is the same, the reduction rate is determined mostly by the holding time at this maximum temperature and the chromium powder ore blending ratio, but the strength of the chromium-containing coke produced is mainly determined by the chromium powder ore blending. Since the dry distillation temperature is determined by the type and size of the coke oven, it is actually best to adjust the reduction rate by adjusting the length of the dry distillation time. According to the method, it is possible to freely adjust the strength and reduction rate according to the intended use of the produced chromium-containing coke to the extent that it suits the intended use.

Example 1 Coking coal for coke production having the composition shown in Table 1 and the industrial analysis values shown in Table 2 was mixed with the composition shown in Table 3 and the coking coal shown in Table 4.
The blending ratio of chromium powder ore with the particle size distribution shown in the table is 1.
In weight%, 0%, 15%, 30%, 45% and 60
%. Each mixture was separated for 1 minute, and one of the mixtures was mixed after adjusting the water content to 12%. Coke was produced according to the calcination method in the test method. In addition, for the other half of the formulation, 8% by weight of polyvinyl alcohol 12.5% aqueous solution was added and mixed, and then 200 kg/cm
50mm x 50mm x 20+
1111 into a charcoal shape, and the molded product was JIS I'l 8 under the heat pattern shown in Fig. 3 in the same way as the former.
B Coke was produced according to the calcination method of the old coking property test method.

The particle size of each coke obtained was adjusted, and the strength was measured according to the British Standard Microstrength Method. The results are summarized in Figure 1. Figure 1 also shows the strength of commercially available charcoal and the strength of blast furnace coke as reference values.

Table 1 (Coking coal blending table, weight %) Table 2 (Industrial analysis values of blended coking coal, anhydrous basis) Table 3 (Chromium ore composition, weight %) Table 4 (Chromium ore particle size distribution) Figure 1 As is clear from the results of 9, according to the method of the present invention,
Chromium-containing coke containing up to 45% by weight of chromium powder ore has higher strength than commercially available charcoal, and when molded products using a binder are used as raw material,
A product with higher strength can be obtained.

Example 2 A molded article similar to the molded article molded using a binder in Example 1 was made with a chromium ore content of 15% and 30%.
% and 45%, and were made from the same raw materials and in the same procedure as in Example 1, and for each of these molded products, the 3
Coke was produced in the same manner as in Example 1 using the seed heat pattern.

The obtained coke was chemically analyzed to quantify the contents of metallic chromium and total chromium, and the metallization rate of chromium content = (metallic chromium/total chromium) x 100% was calculated. The results are shown in Figure 2.

As is clear from the results in Figure 2, the metallization rate of chromium is greatly affected by the maximum dry distillation temperature, and when the maximum dry distillation temperature is 1150°C, reduction does not substantially proceed regardless of the blending ratio of chromium ore. When the temperature exceeds 1200°C, reduction progresses, and at 1250°C, the maximum
From the results of six or more examples, it can be seen that even with a blending ratio of 60 to 70%, chromium ore powder can be agglomerated in the coke manufacturing process. , and it can be seen that half-reduction of chromite is also achieved at this time. 1. Since the chromium-containing coke obtained by the present invention has a chromium content and coke that are tightly integrated, when this is used as a raw material for reduction treatment, coke as a single item and chromium ore as a single item are used for reduction. It is clear that the reduction reaction proceeds more favorably than conventional methods of treatment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the blending ratio of chromium powder ore in raw materials for coke production and the strength of the produced chromium-containing coke. FIG. 2 is a diagram showing the relationship between the blending ratio of chromium powder ore in the raw material for coke production and the metallization ratio of chromium in the produced chromium-containing coke when the dry distillation conditions are changed. FIG. 3 is a heat pattern diagram during dry distillation treatment when the relationship shown in FIG. 1 is derived. FIG. 4 is a heat pattern diagram during dry distillation treatment when the relationship shown in FIG. 2 is derived.

Claims (3)

[Claims] (1) In a method for producing coke for steelmaking in which a raw material for coke production is charged into a coke oven and subjected to dry distillation treatment, up to 45% by weight of chromium ore powder is mixed with the raw material for coke production, and this mixture is poured into a coke oven. A method for producing chromium-containing coke characterized by dry distillation treatment. (2) In a method for producing coke for steelmaking in which raw materials for coke production are charged into a coke oven and subjected to dry distillation treatment, up to 45% by weight of chromium ore powder is mixed with the raw material for coke production together with a binder and molded. , a method for producing chromium-containing coke, characterized by dry distilling the molded product in a coke oven. (3) The method for producing chromium-containing coke according to claim 2, wherein the binder is a polyvinyl alcohol-based binder.