Coke oven gas (COG) is used as fuel for the calcination of limestone in the vertical kilns at this steel mill in India. The COG is boosted to a pressure of 2 kg/cm2 in a set of rotary vane boosters. The gas then goes through an orifice to the kiln for combustion. The gas pressure must be maintained to insure uniform calcination. Blockages in the gas main, boosters and kilns lead to downtime, production losses and increased maintenance costs.
The mill needed to optimize the availability of its lime kilns or else install additional capacity. Because the ring main and the orifice at the kiln level are extremely sensitive to deposits that restrict the gas flow and extend the time required for calcination, the boosters and the orifice had to be cleaned almost daily. The flame arrestor also was a major safety concern.
The mill tried to solve the problem with a chemical treatment program. While it minimized the down- time caused by jamming of the compressor blades and plugging of the burner nozzles from once a day to once a week, it was not sufficient to eliminate need for additional capacity.
SUEZ recommended conducting trials with Ferrameen COG9019. The new product dramatically increased the availability of the boosters and kilns. Dosage based on response analysis, and modifications to the chemical feed system and booster and kiln operation logic, helped to ensure safety at the flame arrestor and while handling chemicals. It also reduced the total cost of treatment.
As a result of these changes, the mill no longer needed additional capacity. The availability of the boosters and kilns was so improved that the mill could handle the increased demand for calcined lime with its existing boosters while keeping a kiln in reserve as a spare.
The shutdown frequency of the rotary vane booster was reduced from 7 to 35 days. Chokage in the ring main and orifice was greatly reduced, improving the availability of the kilns and reducing the percentage of downtime from29% to9%.
For increased safety, the chemical dosing pattern was modified so that no chemical was injected during lance reversal. Centralized dosing helped reduce chemical waste from 5% to <1%. Chemical consumption was reduced by 20% compared to the previous program