Coke Oven Gas is Considered a Clean Manufacturing Gas that has Many Potential Uses

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

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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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Natural Gas Fuel Cells, Reciprocating Engines and Microturbines are Sensible Choices for Combined Heat and Power Industrial Systems

Distributed Energy Systems have the capability to provide both combined heat and electrical power at one time. Overall Energy Efficiency usage is much higher with systems that implement CHP (combined heat & power). For example, an electrical coal power plant may be able to convert 30 - 50 % of the heat provided by coal into electrical energy, whereas a CHP power plant converts the majority or around 80 % into combined heating and electrical power [ 1. Lyons ]. Heating capabilities of value include space heating (or cooling), hot water production and industrial process heat from pressurized steam. However, much of the electrical power systems available to provide these additional heating capabilities are smaller in overall power capacity than regular sized electrical power plants ie coal, nuclear, etc. In general, three types of power technologies exist that provide the above mentioned heating and electrical power, those being Combustion Turbines, Reciprocating Engines & Fuel Cells. These 'mini power stations' are applicable in four different market areas - 1) Residential power & heating, 2) Small Commercial & Institutional Power, 3) Small - Large sized Industrial Systems and 4) Smaller Distributed electrical power for Electrical Utility Company. These systems operate at power capacities from several kW to 25 MW [ 2. The California Energy Commission ]. Fuel cell power systems include molten carbonate (MCFC) or solid soxide (SOFC) fuel cells that are made to mostly run off of natural gas (or related gases) whereas Microturbines & Reciprocating Engines can operate on a variety of fuels including natural gas, diesel or gasoline. Reciprocating Engines are similar in technology and comparable to vehicle engines that are spark or compression ignited. Both Microturbines and Reciprocating Engines provide additional heat provided as combustion waste gas streams that can be controlled with an additional Waste Heat Boiler or Duct Burner. Much of the energy in the combustion flue gases can also be reapplied toward energy (recombustion heating) using a system called a Recuperator. MCFC or SOFC Fuel Cell systems generate additional heat as well because they require that the natural gas be heated to temperatures from 650 - 1000 celcius. A Heat Recovery Steam Generator (HRSG) system is used to recover the heat used to convert the natural gas into hydrogen. The waste heat steam from these systems can also be used for room cooling using an Absorption Chilling System.

Commercial or institutional businesses usually prefer the ability to have heated water for various purposes such as what would fill the needs for a prison or hospital. Waste heat in this case must be cooled down to around 250 degrees Fahrenheit and then used to heat water, instead of directly being utilized by a Boiler or Heat Recovery system. One popular domestic fuel cell company called FuelCell Energy constructs larger sized fuel cells that are specially used to operate a hospital or prison. FuelCell Energy also assists in marketing fuel cells for the food and beverage industry such as breweries or bakeries, where not only hot water but process steam could be used for manufacturing purposes. In fact, there are a number of different manufacturing industries that already implement one of CHP power systems to use both for electricity and process steam. Some of these industries include Food Processing, Chemical/Pharmaceutical, Ceramic, Pulp & Paper, Mining and Textiles, just to name a few [ 3. Lyons ]. These types of industries already require heat for purposes such as distillation or drying, and since CHP systems are very energy efficient they are already used in hundreds if not thousands ofmanufacturing plants. More prevalent and widespread use of these power systems may help to create more jobs as well as save companies money on overall operating costs. These type of power systems, in addition, can provide additional savings in operation by using waste sources of gases such as from landfills, municipal sewage or biogas created from sources such as Anaerobic Digestors. Some companies even provide consulting services or related software to evaluate the use of equipment such as reciprocating engines using a defined amount and source of biogas or landfill gas. It is estimated that landfill gas would most likely provide 10 times or more the amount of power than from other biogas sources. Efforts by the government are being made to also help produce cleaner based CHP power from systems such as Reciprocating Engines by using cleaner burning fuels such as hydrogen, ethanol or by implementing cleaner technologies such as laser spark ignition or partial oxidation engines. In summary, drastic improvements in manufacturing efficiency as well as redudant - backup utility power can be realized with combined heat and power systems such as microturbines, reciprocating engines and fuel cells.

REFERENCES

1. "Combined Heat and Power Using Combustion Turbines" - Solar Turbines Inc. by Chris Lyons - 2006 or later

2. California Distributed Energy Resource Guide - DER Equipment - Combined Heat and Power

3. Same as Reference 1

Photos provided by the Picassa Web Album

KEYWORDS: Distributed Energy, Combined Heat and Power, Microturbines, Reciprocating Engines, Molten Carbonate Fuel Cells, Solid Oxide Fuel Cells, Industrial Process Steam Heat, Heat Recovery Steam Generator, Absorption Chillers, Distillation, Drying, Biogas, Landfill Gas, Wastewater Treatment Gas, Waste Heat Steam, National Fuel Cell Research Center

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