Coke quality

Press, 16 July 1976, Page 3

Coke quality

Sir, — I read that the Christchurch Gas Company may be forced to cease production of coke within the next five vears. Last year I would have greeted that prospect with dismay; this year, although concerned about a substitute clean fuel, I must confess to being pleased. Might I ask the company why such an obvious decline in quality has taken place when already this season we have experienced substantial price increases? Recently 1 changed from size 2 to size 1 because the former had a tendency to form clinker. Last year No. 1. would burn for a fortnight non-stop in an efficient space heater before clinker became a problem. This year after 36 hours the same space heater is entirely clogged with a solid combination of clinker and stones. The last load removed after such a period weighed 960 grammes (21b 3oz). — Yours, etc., T. L. R. WILSON. July 7, 1976.

IA spokesman for the Christchurch Gas Company replies: "The main feature of the correspondent’s complaint lies in the clinkering propensity of the fuel. Clinker is formed through fuel bed temperature being in excess of the fusion point of the ash, thus causing the ash residual of the burned coke to melt and form glass-like products, generally called clinker. The fused mass incorporates much of the non-combustible foreign body that: might be present, in the fuel bed. The ash content of the coke iin current production is normal and consistent with former years, but the fusion temperature could have declined. This will call for special laboratory determination. Ex-

traneous foreign matters such as dirt or stones can enter the fuel consignment from bad storage conditions or mishandling. The size of the coke used will only affect draught, conditions through the fuel bed. and thus could effect fuel bed temperature. The quality factors of No. 1 and No. 2 are similar. Recommended action, apart from change of fuel type, is to reduce draught and to clean the base of the furnace more regularly.”]