Development of New Cokemaking Process, SCOPE21

Preheating the coal charge, employing the high heat conductivity brick, and loweringthe coke discharge temperature have the effect of reducing coking time. Coking time ofpilot plant operation was 8 hours in the case of the coal charge preheated to 280°C, andthe flue temperature of 1250°C. According to the test results of the pilot plant, theproductivity of a commercial plant of the SCOPE21 process was estimated to beenhanced 2.4 times as high as that of the conventional one (Figure 4).Only a minor amount of carbon deposits was found in the area of the feed connectionand standpipe base, which was the same as in conventional process. This is consideredbecause of the effect of briquetting of fine coal according to the basic research (Figure 5).4.3 Environmental protectionEnvironmental conditions will be improved by conveying the hot coal in the sealedstructure, by preventing gas leakage the from the coke oven and by reducing NO x in thecombustion gas due to the new coke oven heating system.1) Smokeless conveying of hot coalWe developed a plug flow transport method for conveying the preheated coal in the pilot plant test. Thetransport rate of 350t/h was a sufficiently high rate even in commercial plants. This charging system makes itpossible to charge high temperature preheated coal into coke a oven safely and cleanly without scatteringdusts.2) Low NO x combustion from coke ovenThe pilot plant is equipped with a new combustion system that will attain the high productivity, uniformheating and low NO x emissions which are the basic requirements the next-generation coke oven has to meet.The new heating chamber is as large as that of the typical commercial plant. Its chamber wall is made ofsuper dense silica brick high heat conductivity for higher productivity. As shown in Figure 6, NO x concentrationin the combustion gas was less than 100ppm when the flue wall temperature was 1250°C, which was thesame temperature measured in the actual scale combustion test.3) Gas leakageIt is usually very difficult to prevent gas leakage from the coke oven because the seal is not perfect and theoven is operated with a gas pressure that is higher than the ambient pressure. SCOPE21 process has anairtight structure in which the oven was completely covered with hoods and a gas pressure control system forthe coke oven was developed for a sub-atmospheric pressure operation. The collected engineering data wasused for the feasibility study of a commercial plant.4) Energy savingThe SCOPE21 process can reduce net energy consumption by 21% as shown in Figure 7. The netenergy consumption for carbonization can also be decreased by preheating the coal charge and by loweringthe coke discharging temperature although an extra power needs in the coal pretreatment system.