A major environmental concern associated with integrated steel mills is the pollution produced in the manufacture of coke, an essential intermediate product in the reduction of iron ore in a blast furnace. Coke is produced by driving off the volatile constituents of the coal—including water, coke oven gas, and coal-tar—by baking the coal in an airless furnace at temperatures as high as 2,000 degrees Celsius. This fuses together the fixed carbon and residual ash. The coke oven gas (COG) byproduct, a combustible hydrogen and hydrocarbon gas mix, may be flared, recycled to heat the coal, or cleaned to be used as a fuel source to generate energy or used to produce methanol.
There are several inherent problems with COG as a fuel for power generation, notably contaminants that would not be found in pipeline natural gas or distillate fuels. Tar, a by-product of burning coal, is plentiful in COG and can be detrimental to gas turbine hot gas path components. Particulates, in the form of dust particles, are another nuisance contaminant that can shorten the life of the gas turbine’s hot section via erosion and plugging of internal cooling holes.
China, the world’s largest steel producing country, has approximately 1,000 coke plants producing 200MT/year of COG. GE Energy has entered into the low British thermal unit (BTU) gases segment in China with an order from Henan Liyuan Coking Co., Ltd. The gas turbines will burn 100% coke oven gas, which will help the Liyuan Coking Plant reduce emissions and convert low BTU gas to power efficiently. This paper will detail the technical challenges and solutions for utilization of COG in an aeroderivative gas turbine, including operational experience. Additionally, it will evaluate the economic returns of gas turbine compared to steam turbine power generation or methanol production.
Techno-Economic and Carbon Footprint Analyses of a Coke Oven Gas Reuse Process for Methanol Production