The influence of the bulk density of the coal blend on the gross calorific value of blast furnace coke

As is known, the specificity of the layered coking process causes the development of fracturing, which determines the formation of the granulometric composition of the coke. The article presents and analyzes data on the physicochemical properties of coke of various size classes. The expediency of studying the values of the calorific value for different classes of the size of blast furnace coke has been substantiated. For this purpose, ramp coke was taken from batteries that were significantly different in size. In particular, coke oven battery I has almost twice the useful volume of coking chambers and, accordingly, the design capacity than coke oven battery II. In addition, the height of the chambers of coke oven battery I is 7000 mm, and that of coke oven battery II is 4300 mm. The above circumstances must be taken into account when evaluating the heat of combustion of various size classes of blast furnace coke. The composition of the investigated charge consisted of classic grades of coals, which are characterized by their inherent set of quality indicators. The charge for battery I was characterized by a lower burst pressure. It is shown that the value of the highest calorific value of wet quenching blast furnace coke undergoes significant changes depending on the size. Size classes less than 25 mm are characterized by maximum values of the gross calorific value, which reach 33.0 MJ/kg and more. The level of "readiness" of coke, expressed by the value of the yield of volatile substances and the actual density of the coke, significantly affects the value of the highest calorific value. Less "finished" blast furnace coke is characterized by higher values of the gross calorific value for all particle sizes. It is concluded that the value of the highest calorific value of blast furnace coke can serve as a criterion (in addition to those already available) for assessing the degree of "readiness" of blast furnace coke. Keywords: coal, coke, coke size classes, degree of readiness, heat of combustion. Corresponding author Miroshnichenko I.V., e-mail: [email protected]

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EFFECT OF BULK DENSITY OF COAL BLEND ON THE CALORIFIC VALUE OF COKE

Journal of Coal Chemistry ◽

10.31081/1681-309x-2020-0-6-4-12 ◽

2020 ◽

Vol 6 ◽

pp. 4-12

Author(s):

I.V. Miroshnichenko ◽

D.V. Miroshnichenko ◽

I.V. Shulga ◽

Yu.V. Nikolaychuk

Keyword(s):

Bulk Density ◽

Quality Indicators ◽

Calorific Value ◽

Dry Weight ◽

Raw Material ◽

State Enterprise ◽

Water Molecules ◽

Material Base ◽

Gross Calorific Value ◽

Coal Blend

The article is devoted to laboratory studies to determine the influence of the bulk density of a coal blend (in particular, tamped) on the value of the gross calorific value of the coke obtained from it. To making up a model coal blends, coal concentrates has been selected and analyzed from the raw material base of Ukrainian coke enterprises. From the studied coals four variants of coal blends has been formed, characterized by different grades. Experimental coking of coal charges has been carried out in a 5-kg laboratory oven designed by the State Enterprise "UKHIN". The bulk coking blend has been moistened to 8 %. The blend for tamping has been moistened to 12 %, tamped into a special matrix to a density of 1.15 t/m3 , and then the tamped coal cake has been placed in a retort for coking. It has been established that the maximum value of the gross calorific value of blast-furnace coke is achieved during coking of coal blends, which are characterized by the following set of quality indicators: R0=0,91–0,94 %; Vdaf = 30,9-31,0 %; C daf = 83,80-83,83 %; Hdaf = 5,01-5,02 %; Od daf = 8,42-8,45 %. It has been shown that an increase in the bulk density of coal blends, characterized by the same set of quality indicators, from 800 to 1150 kg/m3 leads to an increase in the gross calorific value of blastfurnace coke by 0,05-0,12 MJ/kg. Hydrogen bonds are a factor that contributes to the denser packaging of coal grains in the load. For this, the number of water molecules must correspond to the number of polar bonds in carbon macromolecules. With a lack of water, not all polar functional groups present in macromolecules will participate in the formation of new bonds, which will not allow to the coal grains to be packed more tightly. On the contrary, at higher humidity, excess water molecules will take up space in the feed, not participating in the formation of bonds with carbon macromolecules, which will lead to a decrease in the bulk density in terms of dry weight.

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