Investigation of alternative fuels for industrial gas turbines Tamal Bhattacharjee, Paul Nihill, Cormac Bulfin, Ishank Arora Contents 1. Abstract4 2. Introduction4 3. Hydrogen5 3. 1Production5 3. 1. 1Steam Reforming of Hydrocarbons5 3. 1. 2Water Splitting5 3. 1. 3Gasification of Waste & Biomass to produce syngas6 3. 1. 4The process7 3. 1. 5Application to industrial gas turbines8 4. Methanol9 4. 1Abstract9 4. 2Introduction9 4. 3History10 4. 4Manufacturing Process10 4. 4. 1 Production of methanol from synthesis gas10 4. Industrial Process11 4. 5. 1STEP-1: Feed Production11 4. 5. 2STEP-2: Reforming11 4. 5. 3STEP-3: Methanol Synthesis12 4. 5. 4STEP-4: Methanol Purification12 4. 6How it works on a gas turbine12 4. 7Feasibility15 4. 8Advantages & Disadvantages16 4. 9Conclusion17 5. Power Alcohol17 5. 1Introduction17 5. 2Chemistry18 5. 3Production18 5. 3. 1Ethanol from sugar cane18 5. 3. 2Fermentation18 5. 3. 3Distillation19 5. 3. 4Fractional Distillation19 5. 4Air pollution21 5. 5Advantages23 5. 6Disadvantages23 6. References24 1. Abstract
The industrial gas turbine is a key part of modern electricity generation. In 1998 15% of electric power was produced by gas turbines. Due to their efficiency, compactness, reliability and relatively low capital cost 81% of new electric power demand will be met by industrial gas turbines. Gas turbines must meet very strict NOx CO and CO2 regulations. (GL Juste 2006). As the popularity of gas turbines and combined heat and power generation plants increases research has turned to cheaper and more environmentally friendly fuels for gas turbines.
Methane C2H4 is the main fossil fuel used in gas turbines today but with increased regulations on carbon emissions combined with the increasing cost of fossil fuels, research is turning to alternative fuels which may power gas turbines into the future. This literature review explores potential liquid and gas alternative fuels for industrial gas turbines along with some of the latest research in the area and some examples of the successful industrial applications. 2. Introduction
The increasing cost of fossil fuels, the fact that they are a finite resource and the environmental effects of their combustion means that research into alternative fuels is one of the largest and most varied areas of scientific investigation in progress today. As with all scientific research, some will be successful and form the basis of future energy production and some will be either too inefficient or impractical to be implemented in industry. It is interesting to note that some of the methods which seemed impractical even 10 years ago are now being introduced owing to the increasing cost of fossil fuels.
Fuels derived from biomass and gasification of sewage sludge and municipal waste and some methods of hydrogen fuel production appear to hold the most promise. “Different global energy scenario studies indicate that in India biomass may contribute much more: up to 30% of the energy supply by 2100” (K. K. Gupta et al 2010) Gas turbines and combined heat and power (CHP) systems are at the forefront of future European strategies on energy production with current efficiencies for combined cycle facilities above 60%. “The main CHP targets are the reduction of the overall costs and the development of above 40 kW biomass-fired systems…..
Gas turbines enjoy certain merits relative to steam turbines and diesel engines. They have high grade waste heat, lower weight per unit power, dual fuel capability, low maintenance cost, low vibration levels, low capital cost, compact size, short delivery time, high flexibility and reliability, fast starting time, lower manpower, and have better environmental performance. ” (P. A. Pilavachi et al 2000) This project focuses on alternative fuels as applied to industrial gas turbines owing to their projected increase in popularity in the short to medium term at least. 3. Hydrogen 3. 1Production 3. 1. Steam Reforming of Hydrocarbons The bulk of hydrogen fuel production is currently via steam reforming of natural gas this process involves the reaction of natural gas or liquid hydrocarbons with high temperature steam to produce varying amounts of CO and H2. Steam reforming of hydrocarbons does not eliminate CO2 but it greatly reduces the amount which is discharged into the atmosphere. Steam reforming of hydrocarbons is an efficient way of reducing CO2 emissions. In addition to the H2 produced during gasification a low temperature gas shift reaction with the remaining carbon monoxide can produce further H2.
The process of steam reforming natural gas along with the gas shift reaction are governed by the chemical equations below. (K. K. Gupta et al 2010) Steam Reforming: CH4 + H2O – CO + 3H2 ? H = +251 kJ/mol Gas Shift: CO + H2O – CO2 +H2 ? H= -42 kJ/mol (K. K. Gupta et al 2010) The release of CO2 can be completely eliminated in a large plant where the CO2 is captured and injected into an oil or gas reservoir. It is currently disputed between scientists whether or not the production of H2 in this way releases more CO2 than directly burning fossil fuels. 3. 1. 2Water Splitting
There is currently a lot of research concerning the splitting of water to produce H2. This method is yet to find industrial application as it takes a lot of energy to split water and the only sustainable method is the use of renewable technologies to provide the energy. The hydrogen is more likely to be used as a storage medium when the power generated by renewable technologies is not required. An example of this would be the storage of power from a wind turbine during the day. There is a lot of very interesting research into water-splitting with many methods being explored simultaneously.
Thermo chemical water splitting using solar power is an interesting option. Direct thermal water splitting is impractical due to the energy requirements to heat the water to 25000K. But if the water is reacted with metal oxides and redox materials it can be achieved at a much lower temperature. The oxygen and hydrogen are released at different stages eliminating the need for separation. This process can be conducted in a cycle that produces H2 more efficiently from solar radiation. 3. 1. 3Gasification of Waste & Biomass to produce syngas
A Practical Example of waste to energy conversion is the Pyromex waste to energy facility in Germany. The Pyromex system is currently being used successfully to gasify industrial waste in a purpose built plant in Munich Germany. Due to the fact there are no gaseous emissions from the system there is no need for the construction of smoke stacks and the system is considered separate to incineration by EU authorities. Emissions from the plant are in the form of solid sand like dry waste. The waste composition is tabulated below and shows how far below allowable limits the process is.
The raw material in the process is otherwise unrecyclable waste products and the system can treat sewage sludge, plastics, fly ash from power plants and various other waste products. The system has the potential to be a major contributor to the Hydrogen Economy. The prototype plant working on a throughput of 25 ton/day had the potential to produce approximately 2150 kWh by a combined heat to electricity and syngas engine generator system. If used in combination with an industrial gas turbine there is no doubt that owing to the greater efficiency this power output could be improved.
Fig. 1 – Exhaust gas emissions (Pyromex®) 3. 1. 4The process The material to be gasified is introduced into the slowly turning reactor through a two stage tank system. With this setup an oxygen free environment can be ensured inside the reactor pipe, where the conversion of the organics to syngas takes place at over 1000°C. The produced gas is then cleaned with a simple acid and an alkaline scrubber. Even though the temperatures within the reactor are far above 1000°C, the surface remains cool enough to be touched by hand.
The PYROMEX gasification is a closed circuit process and therefore no emissions are released into the environment. The process flow chart below gives a better understanding of the workings of the plant. This process can be easily scaled. And there are numerous plants completed and in the process of construction in Germany and the U. S. Fig. 2 – Gasification process of producing syngas from waste & biomass (Pyromex®) 3. 1. 5Application to industrial gas turbines Once the hydrogen has been produced it can be mixed with carbon monoxide which can also be produced efficiently using solar power.
This syngas can be used in an Industrial gas turbine with some modifications to the fuel nozzle system and careful control of the fuel air ratio to produce electricity. In the case of liquid fuel turbines the hydrogen can be converted to various hydrocarbons using the Fischer-Tropsch process. The use of hydrogen in a gas turbine is a relatively new concept with the use of high hydrogen content syngas becoming an attractive area for research. Unfortunately the use of hydrogen rich gas in a conventional gas turbine involves some tweaks to the ystem. The natural gas lean-premixed combustors have to undergo some modifications if fed with hydrogen rich fuels due to the combined effect of hydrogen shorter auto-ignition delay and faster flame speed. (Paulo Gobbato et al 2010) One of the routes with the highest potential is the pre combustion route utilizing coal in an integrated gasification and combine cycle (IGCC). The challenge in utilizing hydrogen rich fuel is principally associated with its reduced auto-ignition delay time, which can be addressed in one of three approaches: 1.
De-rating the engine – allowing the same mixing time by increasing the auto-ignition delay time through altering the characteristics of the vitiated air (i. e. the inlet temperature of the flow to the SEV). 2. Decreasing the reactivity of the fuel – i. e. by dilution with an inert gas. 3. Modifying the hardware – either to reduce the mixer residence time in line with the reduced auto ignition delay time or develop a concept which is less influenced by the reactivity of the fuel. (Nils Erland et al 2012) 4. Methanol 4. 1Abstract 5.
When methanol is intended to be used as fuel for gas turbine, it is very important to enhance overall thermal efficiency of the gas turbine system, and to make it competitive with conventional oil or gas fuels. There are many ways to accomplish this. Combined cycle is not, however, a proper way, as this could also be applied to conventional fuel. Noting the unique characteristic of methanol, the steam reforming regenerative cycle was investigated by many institutions. In this scheme, wasted heat of the gas turbine exhaust gas is transferred to reformed gas.
And it is recycled back to the gas turbine as a part of fuel, thus resulting in increased overall efficiency of the gas turbine. Thermal decomposition of methanol is also an endothermic reaction and may be applied to the regenerative cycle. In either case, however, only a part of the waste heat is recovered. Hence the hybrid system with combined cycle was proposed to achieve additional heat recovery. But this is a complex system. 4. 2Introduction 6. Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH. . 8. Fig. 3 – Chemical formulation of Methanol 9. Methanol can be used as alternative fuel in gas turbine. Methanol is made from natural gas, coal, and biomass. This was one of the older alternative fuels. Like Ethanol, Methanol is very good for blending with gasoline to replace the harmful octane enhancers. The benefits of using Methanol are that it reduces emissions, which has a significant effect on bettering the environment. Methanol can easily be blended with gasoline. It also has a lower risk of flammability than normal gasoline.
Another benefit of Methanol is that it is made from domestically renewable sources. Methanol can also be used to make the octane enhancer MTBE. Another huge possible benefit of Methanol is that it can be made into hydrogen. 10. 4. 3History 11. Methanol has been tested as a gas turbine fuel in the U. S. In 1974, a 12-hour test was conducted by Turbo Power and Marine in a 20 MW gas turbine at the Bayboro Station of Florida Power Corporation. The methanol was fired as a liquid. NOx emissions were 74% less than those from No. 2 Distillate, and CO emissions were comparable (Power 1979).
In 1978 and 1979, EPRI and Southern California Edison Company sponsored a 523-hour test at SCE’s Ellwood Energy Support Facility, using one half of 52 4. 4Manufacturing Process 4. 4. 1 Production of methanol from synthesis gas 12. Carbon monoxide and hydrogen react over a catalyst to produce methanol. Today, the most widely used catalyst is a mixture of Cu (Copper), zinc oxide, and alumina first used by ICI in 1966. At 5–10 M Pa (50–100 atm) and 250 °C, it can catalyze the production of methanol from carbon monoxide and hydrogen with high selectivity (>99. 8%): 13. CO + 2 H2 > CH3OH…..
It is worth noting that the production of synthesis gas from methane produces three moles of hydrogen gas for every mole of carbon monoxide, while the methanol synthesis consumes only two moles of hydrogen gas per mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where it, too, reacts to form methanol according to the equation: 14. CO2 + 3 H2 > CH3OH + H2O. 15. Some chemists believe that the certain catalysts synthesize methanol using CO2 as an intermediary, and consuming CO only indirectly. 6. CO2 + 3 H2 > CH3OH + H2O; where the H2O byproduct is recycled via the gas shift reaction: 17. CO + H2O > CO2 + H2, 18. This gives an overall reaction, which is the same as listed above. 19. CO + 2 H2 > CH3OH 4. 5Industrial Process Fig. 4 – Industrial process for creating Methanol 4. 5. 1STEP-1: Feed Production 20. The two main two feed stocks, natural gas and water, both require purification before use. Natural Gas contains low levels of sulphur compounds and undergo a desulphurization process to reduce, the sulphur levels of less than one part per million.
Impurities in the water are reduced to undetectable or parts per billion levels before being converted to steam and added to the process. If not removed, these impurities can result in reduced heat efficiency and significant damages to major pieces of equipment. 4. 5. 2STEP-2: Reforming 21. It is the process which transforms the methane and the steam to intermediate reactants of hydrogen, carbon-dioxide and carbon monoxide. Carbon dioxide is also added to the feed gas stream at this stage to produce a mixture of components in the ideal ratio to efficiently produce methanol.
This process is carried out in a Reformer furnace which is heated by burning natural gas as fuel. 22. Reaction: Reaction: 4. 5. 3STEP-3: Methanol Synthesis 23. After removing excess heat from the reformed gas it is compressed before being sent to the methanol production stage in the synthesis reactor. Here the reactants are converted to methanol and separated out as a crude product with a composition of methanol (68%) and water (31%). Traces of byproducts are also formed. Methanol conversion is at a rate of 5% per pass hence there is a continual recycling of the un- reacted gases in to the synthesis loop. 24.
Reaction: 25. 4. 5. 4STEP-4: Methanol Purification 26. The 68% methanol solution is purified in two distinct steps in tall distillation columns called the topping column and refining column to yield a refined product with a purity of 99% methanol classified as Grade AA refined methanol. 27. The methanol process is tested at various stages and the finished product is stored in a large secured tank age area off the plant until such time that it is ready to be delivered to customers. 4. 6How it works on a gas turbine 28. Chemical reaction involved is: It reacts with water to form carbon di oxide (CO2) and hydrogen (H). 9. CH3OH + H2O = CO2 + 3H2 30. The reaction is endothermic and absorbs waste heat at about 300oC. The system performance was predicted using in house process simulator called CAPES and found thermal efficiency of approx. 50% (LHV) when turbine inlet temperature is 1,100oC and compression ratio is 14. The schematic diagram given below illustrates its function. 31. 32. Fig. 5 – Methanol fueled gas turbine process 33. 34. The performance of the gas turbine with steam reforming was recalculated using PRO/II. The same adiabatic efficiency of 87% for compressor and 90% for turbine were used.
Similar value of overall thermal efficiency of approx. 50% was obtained as shown in Table-1. For reference, the performance of air heating system was also investigated. In this case, thermal efficiency was in the same level as reforming but total heat transfer area is 1. 7 times of steam reforming case. Let’s explain model making of steam reformer by PRO/II. After defining stoichiometric data for steam reforming reaction, Gibbs reactor was used for equilibrium calculation at specified temperature. For combustor design, two combustion reactions were defined.
Then two conversion reactors were connected in series and set the conversion parameter to 1. Both reactors are defined as adiabatic. 35. Heat exchangers having phase change were split into 10 to 20 zones and flow configurations were set to true counter flow. Minimum pinch points were set to 10 to 20 oC. Pressure drop of each exchangers were set to 0. 02-0. 01 atm and overall heat transfer coefficient were set to100kcal/h C. Flow Scheme| unit| Fig-1| Fig. -2| Waste Heat Recovery| | Air Heating & Methanol Evap. | Steam Reforming, Water Injection & Methanol Evap. Turbine Inlet Temperature| oC| 1,100| 1,100| Compression Ratio| -| 14| 14| Methanol Rate| kgmol/h| 0. 133| 0. 133| Stoichiometric Air Rate| kgmol/h| 1| 1| Air Rate| kgmol/h| 4. 150| 2. 600| Reforming Water Rate| kgmol/h| -| 0. 133| Total Water Rate| kgmol/h| -| 0. 720| Excess Air Mol Ratio| -| 4. 150| 2. 600| Water/Air Mol Ratio| -| 0. 000| 0. 277| Water/Methanol Mol Ratio| -| 0. 000| 5. 414| 1st Compressor Power| kW| -12. 472| -7. 814| 1st Turbine Power| kW| 24. 128| 19. 750| Water Injection Pump| kW| -| -0. 006| Net Shaft Power| kW| 11. 656| 11. 930| Power Output| kW| 11. 423| 11. 691|
Methanol Heat of Combustion (HHV)| kW| 47. 149| 23. 574| Methanol HHV| kJ/mol| 638. 10| 638. 10| Overall Thermal Efficiency (HHV)| %| 48. 45| 49. 59| Compressor Adiabatic Efficiency| %| 87| 87| Turbine Adiabatic Efficiency| %| 90| 90| Generator Efficiency| %| 98| 98| Methanol Evaporator Area/Pinch Point| m2/oC| 0. 140/10| 0. 138/5| Methanol Reformer Area/Reaction Temp. | m2/oC| -| 0. 201/300| Air Heater Area/Pinch Point/Max. Temp. | m2/oC| 2. 972/10/525| 0| Water Evaporator Area/Pinch Point| m2| -| 1. 452/10| Total Surface Area| m2| 3. 112| 1. 791| Exhaust Temperature| oC| 335. 3| 102. 5| Table 1 – Methanol Fuel Gas Turbine with Steam Reforming & Water Injection or Air Heating 4. 7Feasibility 36. MW, twin engine, gas turbine generator unit supplied by Turbo Power and Marine Systems, Inc. (Edison Co. 1981). The methanol was fired as a liquid. Some fuel system modifications were performed to permit the higher mass and volumetric flow of methanol to achieve base load output. Some elastomers in the fuel system were replaced with materials impervious to methanol attack. The tests showed: “Operations on methanol are as flexible as on natural gas or distillate fuel.
The ability to start, stop, accelerate, decelerate, perform automatic synchronization, and respond to control signals is equal to operations on either natural gas or distillate fuel. Turbine performance on methanol is improved over other fuels due to higher mass flow and the lower combustion temperatures resulting from methanol operations. Oxides of nitrogen emissions on them ethanol-fueled turbine, without water injection, were approximately 80% of the emissions of the distillate-fueled turbine with water injection. There was a significant reduction in particulate emissions during methanol operation.
An additional reduction in oxides of nitrogen emission was obtained during operations of the methanol-fueled turbine with water injection. No significant problems occurred during the test that could be attributed to methanol. The hot end inspection indicated cleaner components within the methanol-fueled turbine. ” During 1984-1985, GE conducted methanol combustion tests of heavy-duty gas turbine combustors in a private study for Celanese Chemical Company, Inc. This work is unpublished. The tests were conducted at GE’s Gas Turbine. Development Laboratory in Schenectady, N . Y.
Tests were performed with an MS6001B full-scale combustor representative of GE heavy-duty gas turbine combustors, and an MS7001 developmental dry low NOx combustor. Then ethanol was fired as a liquid, “dry” and also with water addition. A high-pressure centrifugal pump was used to supply the methanol to the combustor. The tests demonstrated that methanol fuel can be successfully burned in GE heavy-duty combustors without requiring major modifications to the combustor. NOx emissions were approximately 20% of those for the same combustor firing NO. 2 distillate at the same firing temperature.
With water addition, NOx levels of 9 ppmv could be achieved. Liner metal temperatures, exit pattern factors, and dynamic pressures were not significantly affected by methanol combustion and met GE criteria for acceptable performance. The results are valid for 2000 F firing temperature machines (E-class). Additional work would be required to confirm performance with methanol fuel, elevated firing temperatures of the F series of machines. Vaporized methanol will reduce NOx 5% to 10% (relative to CH4 emissions) whereas liquid methanol will reduce NOx 30% relative to CH4 emissions.
Water content in the methanol provides further NOx reduction. In 1984, a field test demonstration was performed at the University of California at Davis (California Energy Commission 1986). Methanol was fired in a 3. 25 MW Allison 501-KB gas turbine for 1,036 hours. Low NOx emissions were observed and were further reduced by mixing water with the methanol. Problems encountered with the traditional gas turbine fuel pump were bypassed by using an off-board centrifugal pump. 4. 8Advantages & Disadvantages 37. Methanol is a liquefied form of methane, a naturally-occurring gaseous hydrocarbon produced by decomposition.
Currently, methane is burned as a ‘waste” gas at oil drilling platforms, coal mining sites, landfills, and sewage treatment plants. The advantage is methane, and its derivative methanol is that it is extremely plentiful; drilling for oil, mining coal, and the decomposition of organic matter all produce methane already. As a hydrocarbon similar to propane and petroleum, methane is a very powerful, explosive gas that can easily take the place of petroleum without marked decline in power or major retooling of existing technologies.
The disadvantages of methanol is the process by which methane is converted into a liquid at normal temperatures; by mixing methane with natural gas and gasoline, methane is converted into methanol. But the need for gasoline does not entirely wean the United States off of oil, so its “alternative” status is questionable. Additionally, the process to capture, store, and convert methane is prohibitively expensive compared to gasoline. 38. 4. 9Conclusion 39. Methanol is considered a superior turbine fuel, with the promise of low emissions, excellent heat rate, and high power output.
The gas turbine fuel system must be modified to accommodate the higher mass and volumetric flow of methanol (relative to natural gas or distillate). The low flash point of methanol necessitates explosion proofing. The low flash point also dictates that startup be performed with a secondary fuel such as distillate or natural gas. Testing to date has been with methanol as a liquid. GE is comfortable with methanol as a liquid or vapor. GE is prepared to make commercial offers for new or modified gas turbines utilizing methanol fuel in liquid or vapor form based on the earlier experience.
Some combustion testing may be required for modern machines applying for very low NOx permits. 5. Power Alcohol 5. 1Introduction Power Alcohol is a mixture of petroleum and ethanol in different proportions and due to these proportions different names are given to each blend like:- 1. As a blend of 10 percent ethanol with 90 percent unleaded gasoline called “E-10 Unleaded”. 2. As a component of reformulated gasoline, both directly and/or as ethyl tertiary butyl ether (ETBE). 3. As a primary fuel with 85 parts of ethanol blended with 15 parts of unleaded gasoline called “E-85. (Rex Weber 2003) When mixed with unleaded gasoline, ethanol increases octane levels, decreases exhaust emissions, and extends the supply of gasoline. Ethanol in its liquid form, called ethyl alcohol, can be used as a fuel when blended with gasoline or in its original state. Well the production of ethanol fuel began way back in1907 but Ethanol use and production has increased considerably during the 1980s and 1990s not just due to the lack of fossil fuels but was also due to several other factors 1.
Ethanol reduces the country’s dependence on imported oil, lowering the trade deficit and ensuring a dependable source of fuel should foreign supplies be interrupted. 2. Farmers see an increased demand for grain which helps to stabilize prices. 3. The quality of the environment improves. Carbon monoxide emissions are reduced, and lead and other carcinogens (cancer causing agents) are removed from gasoline. 5. 2Chemistry Glucose (a simple sugar) is created in the plant by photosynthesis. 6 CO2 + 6 H2O + light > C6H12O6 + 6 O2 During ethanol fermentation, glucose is decomposed into ethanol and carbon dioxide.
C6H12O6 > 2 C2H5OH+ 2 CO2 + heat During combustion ethanol reacts with oxygen to produce carbon dioxide, water, and heat: C2H5OH + 3 O2 > 2 CO2 + 3 H2O + heat After doubling the combustion reaction because two molecules of ethanol are produced for each glucose molecule, and adding all three reactions together, there are equal numbers of each type of atom on each side of the equation, and the net reaction for the overall production and consumption of ethanol is just: Glucose itself is not the only substance in the plant that is fermented. The simple sugar fructose also undergoes fermentation.
Three other compounds in the plant can be fermented after breaking them up by hydrolysis into the glucose or fructose molecules that compose them. Starch and cellulose are molecules that are strings of glucose molecules, and sucrose (ordinary table sugar) is a molecule of glucose bonded to a molecule of fructose. The energy to create fructose in the plant ultimately comes from the metabolism of glucose created by photosynthesis, and so sunlight also provides the energy generated by the fermentation of these other molecules. Ethanol may also be produced industrially from ethene (ethylene).
Addition of water to the double bond converts ethene to ethanol: C2H4 + H2O > CH3CH2OH This is done in the presence of an acid which catalyzes the reaction, but is not consumed. The ethene is produced from petroleum by steam cracking. 5. 3Production Ethanol can be produced by various methods but the most commonly used in today’s world is by the method of fermentation and distillation of sugarcane, grains, corn etc. 5. 3. 1Ethanol from sugar cane The first stage in ethanol production is to grow a crop such as sugar cane. The sugar cane of cut down and undergoes fermentation and distillation. 5. 3. 2Fermentation
Crushed sugar cane in placed in fermentation tanks. Bacteria in the tanks acts on the sugar cane and in time produce a ‘crude’ form of ethanol. This is then passed on to the ‘distillation stills’ where it is refined to a pure form. 5. 3. 3Distillation The impure/crude ethanol is heated in a ‘still’ until it vaporizes and rises into the neck where it cools and condenses back to pure liquid ethanol. The impurities are left behind in the still. The ethanol trickles down the condensing tube into a barrel, ready for distribution. When burned it produces fewer pollutants than traditional fuels such as petrol and diesel.
Fig. 6 – Distillation process of impure/crude ethanol The production of petroleum is done by the fractional distillation of crude oil. 5. 3. 4Fractional Distillation The various components of crude oil have different sizes, weights and boiling temperatures; so, the first step is to separate these components. Because they have different boiling temperatures, they can be separated easily by a process called fractional distillation. The steps of fractional distillation are as follows: 1. You heat the mixture of two or more substances (liquids) with different boiling points to a high temperature.
Heating is usually done with high pressure steam to temperatures of about 1112 degrees Fahrenheit / 600 degrees Celsius. 2. The mixture boils, forming vapor (gases); most substances go into the vapor phase. 3. The vapor enters the bottom of a long column (fractional distillation column) that is filled with trays or plates. The trays have many holes or bubble caps (like a loosened cap on a soda bottle) in them to allow the vapor to pass through. They increase the contact time between the vapor and the liquids in the column and help to collect liquids that form at various heights in the column.
There is a temperature difference across the column (hot at the bottom, cool at the top). 4. The vapor rises in the column. 5. As the vapor rises through the trays in the column, it cools. 6. When a substance in the vapor reaches a height where the temperature of the column is equal to that substance’s boiling point, it will condense to form a liquid. (The substance with the lowest boiling point will condense at the highest point in the column; substances with higher boiling points will condense lower in the column. ). 7.
The trays collect the various liquid fractions. 8. The collected liquid fractions may pass to condensers, which cool them further, and then go to storage tanks, or they may go to other areas for further chemical processing Fractional distillation is useful for separating a mixture of substances with narrow differences in boiling points, and is the most important step in the refining process. The oil refining process starts with a fractional distillation column. On the right, you can see several chemical processors that are described in the next section.
Very few of the components come out of the fractional distillation column ready for market. Many of them must be chemically processed to make other fractions. For example, only 40% of distilled crude oil is gasoline; however, gasoline is one of the major products made by oil companies. Rather than continually distilling large quantities of crude oil, oil companies chemically process some other fractions from the distillation column to make gasoline; this processing increases the yield of gasoline from each barrel of crude oil.
Fig. 7 – Fractional distillation of crude oil 5. 4Air pollution Compared with conventional unleaded gasoline, ethanol is a particulate-free burning fuel source that combusts with oxygen to form carbon dioxide, water and aldehydes. Gasoline produces 2. 44 CO2 equivalent kg/l and ethanol 1. 94. Since ethanol contains 2/3 of the energy per volume as gasoline, ethanol produces 19% more CO2 than gasoline for the same energy. The Clean Air Act requires the addition of oxygenates to reduce carbon monoxide emissions in the United States.
The additive MTBE is currently being phased out due to ground water contamination; hence ethanol becomes an attractive alternative additive. Annual Fuel Ethanol Production by Country (2007–2011)[2][64][65][66] Top 10 countries/regional blocks (Millions of U. S. liquid gallons per year)| World rank| Country/Region| 2011| 2010| 2009| 2008| 2007| 1| United States| 13,900| 13,231| 10,938| 9,235| 6,485| 2| Brazil| 5,573. 24| 6,921. 54| 6,577. 89| 6,472. 2| 5,019. 2| 3| European Union| 1,199. 31| 1,176. 88| 1,039. 52| 733. 0| 570. 30| 4| China| 554. 76| 541. 55| 541. 55| 501. 90| 486. 00| 5| Thailand| | | 435. 20| 89. 80| 79. 20| 6| Canada| 462. 3| 356. 63| 290. 59| 237. 70| 211. 30| 7| India| | | 91. 67| 66. 00| 52. 80| 8| Colombia| | | 83. 21| 79. 30| 74. 90| 9| Australia| 87. 2| 66. 04| 56. 80| 26. 40| 26. 40| 10| Other| | | 247. 27| | | Table 2 – Annual fuel ethanol production by country Table 2 – Annual fuel ethanol production by country | World Total| 22,356. 09| 22,946. 87| 19,534. 993| 17,335. 20| 13,101. 7| 5. 5Advantages
Ethanol has a higher octane number (113) than regular unleaded gasoline (87) and premium unleaded gasoline (93). Complete combustion: Ethanol molecules contain 35 percent oxygen, and serve as an “oxygenate” to raise the oxygen content of gasoline fuel. Thus, it helps gasoline burn completely and reduces the buildup of gummy deposits. Prevent overheating: Ethanol burns cooler than gasoline. Fuel Type| Ethanol| Regular Gasoline| Premier Gasoline| E10 Gasohol| E85 Gasohol| Energy Content (/Gallons)| 84,600| 125,000| 131,200| 120,900| 90,660| Table 3 – Energy content of fuels
Energy content: As shown in Table 2, fuel ethanol contains around 33 percent less energy content than regular gasoline. The energy content of gasohol blends (E10 or E85) is determined by the energy content of ethanol and gasoline, and their ratio. Emissions from ethanol are about 48% of diesel; it is lowest of any of the fuels. “The clean burning characteristics extend turbine life, possibly by as much as 100%. ” (K. K. Gupta 2010) 5. 6Disadvantages Loss of power and performance – Pure ethanol is over 100+ octane, and provides the fuel with much of its octane rating.
Because Ethanol burns at a lower temperature than the older (MTBE) gas, boaters can expect to see a 2 to 3 % drop in RPM. “Use of ethanol in the pure state or as a blend would probably require replacement of any white metal or aluminum in the system as well as some elastomers. ” (K. K. Gupta 2010) 6. References Hydrogen Journal Papers G. L. Juste (2006) Hydrogen injection as additional fuel in gas turbine combustor. Assessment of effects. International Journal of Hydrogen Energy 31 (2006) 2112 – 2121 K. K. Gupta a,*, A. Rehman b, R. M.
Sarviya b, (2010) Bio-fuels for the gas turbine: A review. Renewable and Sustainable Energy Reviews 14 (2010) 2946–2955 P. A. Pilavachi (2000), Power generation with gas turbine systems and combined heat and power, Applied Thermal Engineering 20 (2000) 1421±1429 Paolo Gobbato*, Massimo Masi, Andrea Toffolo, Andrea Lazzaretto (2010) Numerical simulation of a hydrogen fuelled gas turbine combustor. International Journal of Hydrogen Energy 36 (2011) 7993- 8002 Nils Erland L. Haugena, Christian Brunhuberb and Marie Bysveena (2012) Hydrogen fuel supply system and re-heat gas turbine.
Combustion Energy Procedia 23 ( 2012 ) 151 – 160 Website Pyromex® Technology Description http://www. pyromex. com/index. php/en/pyromex-technology/technology-description Methanol & Power alcohol “A Special Report: Burning Tomorrow’s Fuels,” Power, S14-S15, February 1979. “Test and Assessment of Methanol in a Gas Turbine System,” Southern California Edison Company, EPRI Report AP-1712, February 1981. “Methanol. Clean Coal Stationary Engine Demonstration Project. Executive Summary,” California Energy Commission, Report P500-86-004, February 1986. Methanol Power Generation – Demonstration Test Starts for a Power Source at Peak Demand” Japanese High-Technology Monitor, 5 April 1993. “Ethanol blended fuels” – Rex Weber 2003 of Northwest Iowa Community College in cooperation with the Iowa Corn Promotion Board. “Fuel Ethanol” – Zhiyou Wen, Extension Engineer, Biological System Engineering, Virginia Tech John Ignosh, Area Specialist, Northwest District, Virginia Cooperative Extension, Jactone Arogo, Extension Engineer, Biological System Engineering, Virginia Tech
