New moisture control system of coal for coking.

Abstract

Coke oven operations are greatly affected by the properties of charging coal. Especially, fluctuations of moisture content of charging coal have a great adverse effect on the stable operation of coke ovens. We have always aimed at an ideal operational condition that the moisture content of charging coal is reduced and controlled economically to a constant level regardless of weather. For this purpose, the new control technique of coal moisture using waste heat from coke ovens effectively was developed successfully. The first equipment of this process came on stream at Nos. 1 and 2 coke oven batteries of Oita Works in September, 1983. The operation results have been better than expected.Features of this equipment are as follows:(1) This equipment is able to apply to coke oven in operation.(2) The moisture content of charging coal is controlled to 5%.(3) The whole of charging coal is dried.(4) In this process, the sensible heat of combustion waste gas from coke oven and of generated gas in coke oven recovered by heat exchangers using a heat carrying medium. This recovered heat is utilized at a dryer and the heat carrier is recirculated.(5) The capacity of dryer is 260 t-dry coal/h and the moisture content of charging coal can be reduced from 11 to 5%. Moisture content can be reduced from 9 to 5% using only the recovered heat. For reducing from 11 to 9%, a heating furnace is installed to heat circulating medium up.The effects of this process are a decrease in heat consumption (actual: 90-93Mcal/t-dry coal, expected: 78Mcal/t-dry coal) and an improvement of coke quality (JIS DI15015-actual: ⊕1.5, expected : ⊕0.8), an increase of productivity (actual: 11%, expected: 10%). On the other hand, the carry-over to the larry car system and the ascension pipe increased. This affected adversely the gas cleaning process and the tar quality. However, these problems were not substantial and overcame by our operational improvements.This process has been operating satisfactorily.