Coke oven gas is a type of manufacturing gas that can be potentially used to produce other chemicals, fuels or recycled into hydrogen. Coke Oven Gas (COG) is made from the dry distillation of coal from the metallurgical Coke making process. During this process, Hot Coke Oven Gas (HCOG) is quenched to a cooler gas and then it is water saturated as well. However, after this process, COG may still not be ready for resuse since it also contains many other contaminants such as aromatics, tar vapors, napthalene, and polyaromatics which at times can consist up to 30 % by weight of the gas [ 1. K. Norinaga 2010 ]. It must sometimes then go through a refining process where the 'tar vapors and contaminants' are removed. Just as important, hydrogen sulfide gas must also be removed since it is known to be corrosive with metal catalysts that are used to reform the COG. Desulfurization can be accomplished using activated carbon or other types of metal type catalysts. When COG is reused it can be applied towards process heaters and boilers and also gas turbines for power generation. The main components of dry Coke Oven Gas are Hydrogen & Methane which are around 50-60 % and 25-30% respectively. It is an attractive manufacturing gas due to the fact that it has a higher than usual hydrogen content while having a very low carbon dioxide content (~3 %). Such low carbon dioxide content correlates to cleaner manufacturing processes which would typically produce less amounts of greenhouse gases. Other than its use as a direct combustion fuel for heat or energy generation, COG can be used to manufacture chemicals or fuel cell energy and currently there are at least two types of processes that convert COG into other types of manufacturing gases. It can be sequestered into hydrogen or reformed into Synthesis Gas.
Natural Gas Reformation produces Hydrogen while hydrogen sequestration is a manufacturing process developed to isolate and purify the hydrogen from sources like Synthesis Gas. Due to its chemical nature several forms of natural gas reformation can be used on COG which include steam reformation, dry reformation or partial oxidation. For example, the partial oxidation reformation method may be effective in producing the right type of Synthesis Gas. Even though there is a smaller methane percentage in COG as oppossed to natural gas, that amount of natural gas is further converted into hydrogen and carbon monoxide. When reformation technologies are applied towards methanol or other chemical production, a hydrogen to carbon monoxide ratio of 2 to 1 is favorable for further chemical synthesis using catalysis (ie like Fischer Tropsch). Its sequestration into direct hydrogen is another interesting method since it already contains a high level of hydrogen and may not need further reformation as it would produce just slightly higher levels of hydrogen. For hydrogen isolation it appears that adsorption and membrane separation are two technologies that are effective in sequestering hydrogen from other gases. The methods of Pressure Swing Adsorption as well as Membrane based hollow fiber or Assymetric type materials could be favorable technologies for hydrogen sequestration [ 2. J. Ritter et al 2007 ]. Overall, Coke Oven Gas has many potential applications in energy generation as well as chemical manufacturing, driven and supported by the Steel Industry. Since COG has a high hydrogen content as well as a low carbon dioxide it may be used as an environmentally clean manufacturing gas that have may have several future opportunities not limited to the types described above. In the future, there may be a need to use manufacturing gases that produce low carbon dioxide content mostly unrelated to how it is used. Coke Oven Gas (COG) may be an example of such a manufacturing gas.
REFERENCES
1. "Application of an Existing Chemical Kinetic Model to a Practical System of a Hot Coke Oven Gas Reforming by Non Catalytic Oxidation", Industrial and Engineering Chemistry Research Vol 49 No 21 pgs 10565-10571 [2010] by K. Norinaga, H. Yatabe, M. Matsuoka, J. Hayashi
2. "State of the Art Adsorption and Membrane Separation Processes for Hydrogen Production in the Chemical and Petrochemical Industries", Separation Science and Technology Vol 42 No 6 pgs 1123-1193 [2007] by JA Ritter, AD Ebner
Photos taken from the Picassa Web Album
KEYWORDS: Coke Oven Gas, Synthesis Gas, Hydrogen Sequestration, Low Carbon Dioxide content Manufacturing Gas, Partial Oxidation, Dry & Steam Reformation, Aromatics & Tars in Coke Oven Gas, Coke Gas Desulfurization, Clean Manufacturing Gases, Combustion of Coke Oven Gas in Heaters & Boilers, Chemical Synthesis from Coke Oven Gas, Methanol Synthesis
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