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Showing posts with label Ammonia. Show all posts
Showing posts with label Ammonia. Show all posts

Monday, May 28, 2012

Fuelcell can become a commercial reality

We currently generate electric city from heat, obtained by combustion of fossil fuel such as coal, oil and gas. But such combustion generates not only heat but also greenhouse gases such as Carbon dioxide and oxides of Nirogen.The only alternative to generate power without any greenhouse gas emission is to use a fuel with zero carbon. However, oxides of Nitrogen will still be an issue as long as we use air for combustion because atmospheric air contains almost 79% Nitrogen and 21% oxygen. Therefore it becomes necessary to use an alternative fuel as well as an alternative power generation technology in the future to mitigate greenhouse problems. Hydrogen is an ideal fuel to mitigate greenhouse gases because combustion of Hydrogen with oxygen from air generates only water that is recyclable. Combining Hydrogen with Oxygen using Fuel cell, an electrochemical device is certainly an elegant solution to address greenhouse problems. But why Hydrogen and Fuel cell are not commonly available? Hydrogen is not available freely even though it is abundantly available in nature. It is available as a compound such as water (H2O) or Methane (CH4) and Ammonia (NH3). First we have to isolate Hydrogen from this compound as free Hydrogen and then store it under pressure. Hydrogen can easily form an explosive mixture with Oxygen and it requires careful handling. Moreover it is a very light gas and can easily escape. It has to be compressed and stored under high pressure. Generation of pure Hydrogen from water using Electrolysis requires more electricity that it can generate. However, Hydrogen cost can be reduced using renewable energy source such as solar thermal. The solar thermal can also supply thermal energy for decomposing Ammonia into Hydrogen and Nitrogen as well as to supply endothermic heat necessary for steam reformation of natural gas into Hydrogen. Onsite Hydrogen generation using solar thermal using either electricity or heat can currently become a commercial reality. Hydrogen generation at higher temperatures such as Ammonia decomposition or steam reformation can be directly used in Fuel cell such as Phosphoric acid Fuel cell. Phosphoric acid fuel cell is a proven and tested commercial Fuel cell that is currently used for base load power generation. It is also used for CHP applications. Hydrogen generation using solar thermal and power generation using Fuel cell is already a commercial reality and also an elegant solution to mitigate greenhouse gases. Large scale deployment of Fuel cell and solar thermal will also reduce the cost of installations and running cost competing with fossil fuel.Fuecell technology has a potential to become a common solution for both power generation and transportation. While Government can encourage renewable energy by subsidizing PV solar panels and discourage fossil fuel by imposing carbon tax, they should give preference and higher tariff for power purchase from Solar thermal and Fuel cell power generators. This will encourage large scale deployment of Fuel cell as a potential base load power source.

Thursday, May 17, 2012

Ammonia can substitute Gasoline

Ammonia is a well known industrial chemical that is manufactured worldwide as a precursor for the production of Urea. The chemistry and technology of Ammonia synthesis is well known and well established. It was a land mark achievement to fix atmospheric Nitrogen into the soil in the form of Urea as a fertilizer. It has 17.6% Hydrogen and 82.4% Nitrogen making it an ideal fuel for combustion when compared to Gasoline in terms of greenhouse gas emission because Ammonia no carbon. Handling free Hydrogen has always been a concern due to its explosive nature and lightness. Transportation of Hydrogen in the form of Ammonia is relatively cheaper and safer. A non-regulated Ammonia nursing tank at 265 psi pressure holds 3025kg Ammonia, containing 534kg Hydrogen, whereas a 5900 gallon Hydrogen tube trailer at 3200 psi pressure, contain only 350kgs of Hydrogen. Low pressure Ammonia tank with less than 25% volume contain more than 53% Hydrogen than a high pressure tube trailer. Ammonia has a lower volumetric energy density compared to other fuels.However, after subtracting energy required to elicit hydrogen from each fuel, hydrogen emerges with highest energy density compared to other fuels, and it is the only fuel which is carbon free. These qualities make Ammonia, a potential substitute for Gasoline. Ammonia need not be used as direct combustible fuel in internal combustion engines but it can be used as Hydrogen carrier safely and economically. The Hydrogen resulting from the decomposition of Ammonia can be used as fuel in a Fuel cell car as well as in a combustion engine. It can also be used to generate small onsite power using a Fuel cell or IC engine. For example, 534kg Hydrogen can generate Electricity up to 10 MW and up to 6Mw thermal energy using a Fuel cell. Currently ammonia is manufactured using fossil fuel source such as natural gas or naphtha to generate Hydrogen in the form of Syngas.But this can be effectively substituted with renewable source of Hydrogen such as Electrolysis of water using renewable solar thermal power or wind energy. Alternatively a biogas can be steam reformed to generate Hydrogen similar to natural gas. The generated Hydrogen can be compressed and stored. Nitrogen constitutes 79% of atmospheric air and it can be obtained by air liquefaction and separation by distillation or by simple membrane separation method to separate air into Nitrogen and Oxygen. The resulting Nitrogen can be compressed and stored for Ammonia sysnthsis.Production of Ammonia using Bosch Haber process is well known. Ammonia can be transported in pipelines, in tankers by road, rail or ship to various destinations. Ammonia can be readily be used as fuel using a spark ignited combustion engine with little modifications because Ammonia is classified as non-combustible fuel. Alternatively, it can be decomposed in a catalytic bed reactor and separated into Hydrogen and Nitrogen using PSA (pressure swing adsorption) system. The resulting Hydrogen can be stored to run a Fuel cell car similar to Honda FCX. Ammonia, as a Hydrogen carrier can substitute gasoline as an alternative fuel for transportation and power generation. All necessary technologies and systems are commercially available to make it a commercial reality.

Tuesday, May 8, 2012

Power generation with Ammonia

Majority of current power generation technologies are based on thermodynamic principles of heat and work. Heat is generated by chemical reactions such as combustion of coal, oil or gas with air or pure oxygen. This heat of combustion is then converted into work by a reciprocating engine or steam turbine or gas turbine. The mechanical energy is converted into electrical energy in power generation and as a motive force in transportation. The fundamental principles remain the same irrespective of the efficiencies and sophistications we incorporated as we progressed. The efficiency of these systems hardly exceeds 30-40 of the heat input, while the remaining 60-70 heat is wasted. We were also able to utilize this waste heat and improved the efficiency of the system by way of CHP (combined heat and power) up to 80-85%.But this is possible only in situations where one can utilize both power and heat simultaneously. In a centralized power plant such large heat simply dissipated as a waste heat through cooling towers and in the flue gas. This is a huge loss of heat because a substantial portion of heat of combustion is simply vented into the atmosphere in the form of greenhouse gases. If ‘greenhouse gas’ and ‘Global warming’ were not issues of concern to the world, probably we would have continued our business as usual. Generation of heat by combustion of hydrocarbon is one example of a chemical reaction. In many chemical reactions, heat is either released or absorbed depending upon the type of reaction, whether it is exothermic or endothermic. Sometimes these chemical reactions are reversible. It may release heat while the reaction moves forward and it may absorb heat while it moves backward in the reverse direction. By selecting such reaction one can make use of such energy transformations to our advantages. One need not release the heat and then release the product of reaction into the air like burning fossil fuels. Ammonia is one such reaction. When Hydrogen and Nitrogen is reacted in presence of a catalyst under high temperature and pressure the reaction goes forward releasing a large amount of energy as practiced in industries using Heber’s process. The heat released by this reaction can be converted into steam and we can generate power using steam cycle. The resulting Ammonia can further be heated in presence of a catalyst by external heat due to endothermic nature of the reaction and split into Hydrogen and Nitrogen. However, such heat can be supplied only from external sources. One University in Australia is trying use the above principle by using solar thermal energy as a source of external heat. The advantage of this system is power can be generated without burning any fossil fuel or emitting any greenhouse gas. One can use renewable energy sources such as solar thermal and also use Ammonia as a storage medium. Ammonia is a potential source of energy to substitute fossil fuels. However, such Ammonia is currently synthesized using Hydrocarbon such as oil and gas. The source of Hydrogen is from synthesis gas resulting from steam reformation of a Hydrocarbon. Hydrogen can also be derived from water using electrolysis using renewable energy source. In both the above cases, renewable energy is the key, without which no Hydrogen can be produced without a Hydrocarbon or an external heat is supplied for splitting Ammonia. Ammonia can also be split into Hydrogen and Nitrogen using external heat. The resulting Hydrogen can be used to generate power using a Fuel cell or run a Fuel cell car. Nitrogen also has many industrial applications.Thereoefore Ammonia is a potential chemical that can substitute fossil fuels in the new emerging renewable economy.

Thursday, April 5, 2012

Ammonia as a source of Hydrogen for future cars

Synthesis of Ammonia is one of the remarkable achievements of Chemical engineering in forties. It is a precursor for Urea, the fertilizer that brought about ‘Green revolution’ in agriculture industry and helped to achieve record food production all over the world. It was a milestone in modern chemistry to synthesis a molecule containing 1 atom of Nitrogen and 3 atoms of Hydrogen, reperesented by NH3 called Ammonia. The Heber-Bosch process for the production of Ammonia is a well established, mature, commercial technology. The process uses a Hydrocarbon source such as Naphtha or Natural gas as the feed stock to generate a synthesis gas composed of Hydrogen and Carbondioxide.The gas mixture is separated into carbon dioxide and Hydrogen using PSA (pressure swing adsorption ) technology. The resulting Hydrogen is used to combine with Nitrogen to synthesize Ammonia. The chemical reaction can be represented by the following equation. N2 + 3H2 ---------- 2 NH3 The above reaction takes place at a pressure of 100-200 bars and temperature of 300-500C in presence of a catalysts. It is an exothermic (heat releasing) reaction and the catalyst bed is cooled and maintained at 400C to be efficient.Buth this process of Hydrogen generation using Hydrocarbon emits greenhouse gases. Alternatively, Hydrogen can be generated using different methods using renewable energy sources using water electrolysis. Such process may be used in the future for this application. Nitrogen is derived from atmospheric air. The air we breathe contains about 79% of Nitrogen and 21% Oxygen. But these two gases can be separated by liquefying the air by cryogenic process and distilling them into two fractions. Alternatively, they can be separated using pressure swing adsorption or membrane separation process, utilizing their density differences. In either way, Nitrogen can be separated from atmospheric air. By combining the above Hydrogen and Nitrogen, it is possible to synthesis Ammonia on a commercial scale. The ammonia can be easily split into Hydrogen and Nitrogen by passing Ammonia through a bed of Nickel catalyst at 200-400C as and when required, to generate onsite Hydrogen. This Hydrogen can be used for power generation or to run our cars using PEM Fuelcell.As we have seen previosulsy, we are now looking for various sources of Hydrogen, and Ammonia is one of the promising sources for couple of reasons. The process and technology of Ammonia production, transportation and usage is well documented and has been practiced for few decades. It does not emit any greenhouse gases.Liquified Ammonia has been widely used in air-conditioning and refrigeration systems. Ammonia can be easily metered into any system directly from the cylinder. It is easier to use Ammonia directly into a convention internal combustion engines in place of Gasoline and this technology has already been practiced in 1880. Ammonia is pungent and any leakage can be easily identified. The advantage of using Ammonia as a fuel in cars, it does not emit any smoke but only water vapour.It can be admixed with Gasoline or used as 100% anhydrous Ammonia. It also helps in reduction of NO2 emission, especially is diesel engines. Ammonia has a great potential as a source of future fuels provided the sources of Hydrogen comes from water using renewable technologies or by photo-electrolysis using sunlight.