Degradation Of Coke Research Articles

A quantitative measure of coke abrasion.

The size degradation of coke and model coke materials in tumble drums has been studied. For the model materials it was shown that current tumble strength indices are affected by size degradation due to both volume breakage and abrasion. The poor correlation between these strength indices can in part be explained by differences in the relative importance of these two mechanisms in different drums. A new procedure using presta-bilized material was developed in which size degradation was controlled by the abrasion mechanism alone. It was found that, by performing measurements in this manner, abrasion of the model coke materials could be represented as a first order rate process. The abrasion rate constant showed a strong relationship with material strength as measured by compressive strength.Seven cokes with a relative abrasion resistance varying from very low to high were examined using this procedure. In all cases, the abrasion process was well represented by the first order rate equation and the measured values of abrasion rate constant were reproducible to±3%. The abrasion rate constant was found to increase with increasing coke size. Abrasion rate constants measured in ASTM and MICUM drums correlated well and there is potential to relate the rate constant to fundamental coke properties.

Thermal degradation of metallurgical coke

To understand the drastic deterioration of coke at the 3–5 m level above the tuyeres in the blast furnace, studies were made of the tensile strength in relation to the JIS drum strength, and measurements were made of the tensile strength of coke at high temperatures (maximum 2300 °C). Plastic deformation was observed above 2000 °C and this could be estimated from the microstrength and the porosity of coke. It was concluded that the factors affecting the resistivity to plastic deformation were the coke bonding between inerts and reactives and the existence of amorphous texture, and that the thermal degradation of the matrix strength must contribute, to some extent, to the drastic reduction in drum strength in the lower part of blast furnace.

Some aspects of deterioration of coke in blast furnace.

on the basis of the results of dissection of Nagoya No. 1 blast furnace, studies have been made on the degradation of coke in a large blast furnace. The results o f these studies show as follows.(1) The degradation of coke in a blast furnace is greatly influenced by the temperature wherein coke is subjected to the CO2 reaction.(2) Lump coke, which begins to degrade due to the selective solution loss and the decrease in strength at 1 000°C, does not change the grain size up to 1 400°C but begins to reduce the size markedly above 1 400°C.(3) Coke fines deposited between the lower part of shaft and the tuyeres are concentrated in the vicinity of raceway and moved by the kinetic energy of gas.(4) The increase in the alkali content of coke (by 5% maximum in the present study) does not decrease the strength of coke. Further, the relationships between the inner volumes of dissected blast furnaces and the change in the properties of coke charged in furnaces were studies. The results of this study suggest that the size reduction ratio of coke particle is higher and the degradation conditions of coke become more strict in the case of large blast furnace than that of small one.

Physical degradation of coke in blast furnace.

Fbeen concluded that the thermal degradation and the attack by inorganic compounds contribute considerably to the drastic degradation at the position of 3-5m above the tuyere level, and that the contribution to the deteriorations by CO2 reaction is smaller than the former.On the base of these findings, the coke degradation through blast furnace has been tried to determine by measuring the difference of coke size between before charging and at the tuyere during the operation with very low fuel rate (396kg/pig-t). The result obtained implies that the less thermal level of the lower part of blast furnace brings the less degradations of coke through blast furnace.Another blast furnace trial has been conducted with the low CSR (coke strength after CO2 reaction) cokes with enough JIS drum strength (more than 92.0 in DI3015) which are produced mainly by lowering the flue temperature of coke ovens. Any serious problems have not been encountered such as frequent slips and scaffold formations during the operation. A clear relation is recognized between the slag discharging speed and the hot drum index (1500°C) of charged coke.To confirm what kind of coke shows the less thermal degradation, the apparatus for measuring the indirect tensile strength at high temperatures (2300°C) has been developed. It is found that the optimum inerts and the high micro strength are indispensable to get the coke with less thermal degradation.

高炉内におけるコークスの劣化機構に関する 2～3 の検討

Based on the results of dissection of Nagoya BF No.1, studies were conducted on the degradation of coke in a large blast furnace. The results of these studies show the following facts. 1) The degradation of coke in blast furnaces is greatly influenced by the temperature at which coke is subjected to CO2 reaction. 2) The lump coke, which begins to degrade due to selective solution loss and to decrease its strength at 1 000°C, does not change its grain size up to 1 400°C but begins to reduce it sharply above 1 400°C. 3) The coke fines depositing between the lower part of the shaft and the tuyeres are generated in the vicinity of the raceway and move there by the kinetic energy of the blast. 4) The increase in the alkali content of coke (by 5% maximum in the present study) does not decrease the strength of coke.Further, the relationship between the inner volumes of Nippon Steel's dissected blast furnaces and the changes in coke size in these furnaces was studied. It is suggested that the coke particle size reduction ratio is higher and the coke degradation conditions are severer in large blast furnaces than in small ones.

Degradation of Coke and Char during Solution Loss Reaction

In order to find its feasibility as blast furnace coke feedstock, non-metallurgical coal was compared with metallurgical coal in terms of reactivity and degradation during CO2 gasification reaction, with emphasis on the difference between the pore structure of coke and that of char. The following results were obtained:(1) The higher reactivity of non-metallurgical coal char is due to the fact that their coal rank is lower.(2) Though the pore structure of metallurgical coke is composed mainly of macropores, pore walls of char are either abundant in micropores when the rank is low, or practically nil in any size when the rank is relatively high.(3) Open macropores characterize the pore structure of coke, while char has a considerable number of closed pores.(4) The deterioration of the structural strength of coke becomes greater than that of char as gasification reaction proceeds.

Mathematical Model for Blast Furnace Operation Considering the Degradation of Coke by Gasification

Mathematical Model for Blast Furnace Operation Considering the Degradation of Coke by Gasification

コークスの性状変化を考慮した高炉モデル

コークスの性状変化を考慮した高炉モデル

アルカリ吸着によるコークスの劣化について

アルカリ吸着によるコークスの劣化について

コークスのガス化反応による劣化について

コークスのガス化反応による劣化について

コークスの高温劣化による異常炉況

コークスの高温劣化による異常炉況