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Tag Archives: Integrated gasification combined cycle

Coal is the single largest fuel used for power generation all over the world, due to its abundant availability and established infrastructure and technology. However, greenhouse gas emission poses a significant challenge in continuing the usage of coal as prime fuel. Currently, Natural gas is favored as fuel for power generation and number of LNG (liquefied natural gas) plants have been set up in many parts of the world. Coal seam methane gas is another potential source that competes with natural gas. Basically, Methane is the major constituent of such gases in the form of Hydrogen  and they are suitable for both combustion as well as for gasification for power generation. Countries who are endowed with large deposits of coal such as Australia, South Africa, Indonesia have advantages in clean coal technologies and in reducing their greenhouse gas emissions. There is an opportunity for coal-fired power plants to continue their operations, if they can solve the greenhouse gas emission and other pollution problems associated with coal. Number of companies are now re-evaluating clean coal technologies such as IGCC and carbon capture and reuse.

As we have seen in previous articles, Hydrogen is the key in developing clean coal technology of the future. That is why, gasification technology such as IGCC (Integrated Gasification and Combined Cycle) is gaining importance over combustion technologies because that is the only way we can introduce a Hydrogen molecule in the combustion by way of ‘Syngas’. By introducing Hydrogen, we not only can improve the thermal efficiency but also use the heat of combustion to the most by combined cycle with reduced GHG emission. It also facilitates the usage of existing and known power generation technologies such as, steam turbine and gas turbine, as well as, new technologies such as Fuel cell and Hydrogen turbines.

Coal in the form of pumpable liquid (CWS –coal water slurry) is another key milestone in developing a clean coal technology. Countries like China and Indonesia have been using coal water slurry for power generation successfully. Finely powdered coal is mixed with water in the ratio of 60:40 along with dispersant such as Lignosulfonate as additives to make a finely dispersed, viscous liquid that resembles heavy petroleum oil, ready for combustion. It is easier to handle pumpable oil than a solid coal.

A novel products called ‘colloidal coal water’ (CCW) is a finely dispersed colloidal coal in water with additives such as surfactants and dispersants with specific formulating agents leading to certain rheological properties is a key development in clean coal technology. The coal water slurry now used does not have long-term stability and storage properties like colloidal coal water fuel. The work is under development and it is expected that such finely dispersed colloidal coal water mix resembling a liquid hydrocarbon may be named as ‘liquid coal’ for all practical purposes will become a low-cost fuel in the future power generation.

This ‘colloidal coal liquid’ can be easily gasified or used as liquid fuel for combustion equipment such as boilers and also serve as precursor for a number of chemical product synthesis as downstream products. The emitted Carbon dioxide can be captured cryogenically and separated in a pure form for potential application such as ‘Natural Refrigerant’ and to synthesize number of chemical products. Clean coal can become a commercial reality provided we re-evaluate the coal preparation, gasification methods and to contain emitted carbon into a useful product of commerce.

There is a general opinion that Hydrogen is now very expensive compared to Gasoline and Diesel. It depends on how you generate Hydrogen. We have used Gasoline and Diesel for several decades and real cost of crude oil is much lower than what we are paying for Gasoline and diesel at the service stations. Crude oil is formed naturally and all the cost involved is for pumping, transportation and refining. The cost of energy spent on transportation and refining is also comparatively low. It is the geopolitical situation in the world, supply demand gap, Government taxes and levies, inventory levels, financial market and distributors play a key role in fixing the price of these fuels.

Hydrogen can be generated from tap water without involving fossil fuels at all. But Governments are spending on research and development of Hydrogen generation using fossil fuels such as natural gas and coal. It is understandable that these sources are suitable for bulk production of Hydrogen on an industrial scale. We will also be able to use existing fossil fuel infrastructure to the most extent. But the flip side of this approach is Hydrogen generated by this route is still not pure enough to meet Fuel cell requirements. This Hydrogen may be suitable for Hydrogen combustion engines. Why they are not suitable? For example, Hydrogen is generated from natural gas by steam reforming,Syngas is generated as an intermediary product which is a mixture of Hydrogen and Carbon monoxide; but also other impurities present in natural gas such Sulfur,Phosphorus and Mercaptans etc.Natural gas has to be purified to remove all these impurities before it can be subject to steam reformation. In spite of an elaborate purification methods adopted, Fuel cell suppliers are reluctant to guarantee the life of their Fuelcell.The Fuel cell uses expensive Platinum as a catalyst which can be readily poisoned by the presence of impurities in Hydrogen, produced from natural gas. This is one of the main reasons why Hydrogen becomes expensive by this route. Industries can pay high cost for this Hydrogen, but ordinary citizens cannot afford to pay.

Hydrogen can be generated directly from tap water by simply electrolyzing it using a Direct current such as solar and wind. If we use grid power, it requires about 68kwhrs of electricity, costing about $3.40 per Kg of Hydrogen. Assuming Hydrogen will cost about $5 per kg after compression and storage, it is still worth the cost. This Hydrogen will give a mileage of 73.4 miles/kg using Fuel cell car. This is equal to 3.67 Gallons of gasoline costing about $13.76, at the rate of $3.75 per gallon. It is very clear that hydrogen is cheaper than gasoline or diesel. At the current price,Gasoline  costs 275% more than Hydrogen gas.

By converting existing coal and oil based power plants into IGCC, Integrated Gasification and Combined Cycle plants, Government can cut the current emission levels of greenhouse gases, and at the same time supply electricity at the prevailing rates. We do not have to import oil or gas. Government should fund conversion of coal and oil-fired power plants into IGCC plants and create Hydrogen infrastructure, by producing more Hydrogen Fuel cell cars and Hydrogen service stations. By adopting this policy, US Government can bring down the prices of crude oil in the international market which will help cut the prices of all other petrochemical products like fertilizers, plastics, drugs and cosmetics. The crux of the issue is to divert petroleum products from fuel use to other uses. At the same time Governments can reduce their greenhouse emissions to the level demanded by scientists. By reducing the cost of solar panels to less than $.100 per watt, Renewable Hydrogen will become a commercial reality and that will be the end of fossil fuels.

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