Wednesday, March 7, 2012
All roads lead to Hydrogen
We have discussed about the formation of fossil fuel as part of carbon cycle. It takes several million years before the carbon from the plants and animals turn into fossil fuels due to chemical reactions under higher pressure and temperature. The fossil fuels include solid coal, liquid oil and gaseous Hydrocarbons such as crude oil and natural gas. The natural gas forms the top layer due to its lightness. Natural gas is also the result of anaerobic reaction by microorganism in the absence of air converting organic matter under the earth into a gas. The gas during exploration comes with great pressure to be transported across several kilometers. We are actually duplicating this process to generate Biogas from our food and agriculture wastes and other organic matters. The end product is a mixture of methane and carbon dioxide. During oil and gas exploration we get methane and carbon dioxide and other gases such as Hydrogen sulfide depending upon the location of the oil field. That is why Sulfur and other products such as Mercaptnans are present in crude oil and natural gas. When these fossil fuels are burnt the gaseous combustion products contain sulfur dioxide and oxide of nitrogen along with oxides of carbon. Air is normally used for combustion which is a mixture of Nitrogen and oxygen in the ration of 71:21,therefore, the combustion products invariably consist of oxides of nitrogen. We are so addicted to oil and we are even trying to convert natural gas into oil, similar to gasoline using GTL (gas to oil) process. However all these combustion processes can be reacted with steam to form synthesis gas, a precursor for liquid Hydrocarbon. It is quite obvious that water in the form of steam is a key component in future energy mixes because that is how one can introduce a Hydrogen molecule in the reaction process. Hydrogen in the form of water is the key. Even if we can successfully steam reform natural gas to get Hydrogen we still have problems deal thing with traces of sulfur and mercaptans, potential poison for catalyst in PEM (Proton exchange membrane) Fuelcells.The idea is to generate Hydrogen using a carbonaceous source such as fossil fuel for simple reasons. It is abundantly available but it emits greenhouse gases; but when you introduce Hydrogen into the mix then there is a good possibility of reducing greenhouse emission, even though we still use fossil fuels. Secondly, we are cautious to handle pure Hydrogen due to its explosive nature and the best available option is to mix Hydrogen with combustion products of fossil fuels. The result is the formation of Syngas. Syngas is an important intermediary that will lead us to the Hydrogen economy of the futue.The syngas can be generated by various methods as long as we have an organic source and water (steam) source. In fact all food and agriculture waste can be converted into syngas either using a biological process or by gasification process. Both will lead to formation of Methane or syngas. Syngas is a mixture of hydrogen with carbon dioxide formed in the following sequences, starting with carbon ,air and steam. 2C + O2-------- 2 CO, 2CO + 2H2O---------2H2 +2 CO2 The carbon source can be any organic source such as coal, coke, wood etc.As you can see in the reaction, the quantity of carbon source is equally important to generate Hydrogen. One can say that Syngas is a match maker between fossil economy of the past and Hydrogen economy of the future. It is a very important chemical reaction that will change the future energy scene in the world. That is why many counties like US and Australia and in Europe who have considerable coal deposits are now trying to generate Hydrogen from coal. Once coal is converted into a gas such as syngas then they are one step closer to separate Hydrogen from syngas.Number of companies and Research organizations around the world are trying to develop an efficient and economical method of generating Hydrogen from coal. They have to find suitable conditions to generate higher yield of Hydrogen from syngas and then find an efficient system to separate Hydrogen from carbon dioxide. As I have mentioned earlier, the purity of Hydrogen is important especially when we use coal as the basic material because it contains number of impurities to be removed before converting into a syngas. As we can see, all energy roads are now leading to Hydrogen as the ultimate clean fuel of the future. When the demand for Hydrogen increase, the demand for water too will increase because it is the direct source of Hydrogen. Energy and water are two side of the same coin as I have mentioned earlier in the past.