SAI VIDYA INSTITUTEOF TECHNOLOGY US N 1 V A Rajanakunte, Bangalore-560064 DEPARTMENT OF MECHANICAL ENGINEERING INTERNAL ASSESSMENT: III VIII SEM, ME MAX MARKS : 50 SUBJECT: BIOMASS ENERGY SYSTEMS DATE: /05/2016 SUB CODE: 10ME843 TIME: 1.30PM – 3.00PM Note: Answer any FIVE full questions, choosing at least two questions from each part. PART-A 1 What is Ethanol? With the help of flow chart explain the production of ethanol form sugar cane. With the help of neat sketches, state the modifications necessary for SI and CI Engines for use of Bio-gas. 1 0 1 0 CO 1 CO 1 3 With a neat flow chart, explain the production of ethanol from wood by acid hydrolysis. 4 state the various effect of using bio-diesel in I.C.engines 1 0 1 0 CO 1 CO 1 2 SAI VIDYA INSTITUTE OF TECHNOLOGY US N 1 V A Rajanakunte, Bangalore-560064 DEPARTMENT OF MECHANICAL ENGINEERING INTERNAL ASSESSMENT: III VIII SEM, ME MAX MARKS : 50 SUBJECT: BIOMASS ENERGY SYSTEMS SUB CODE: 10ME843 DATE: /05/2016 TIME: 1.30PM – 3.00PM Note: Answer any FIVE full questions, choosing at least two questions from each part. PART-A 1 What is Ethanol? With the help of flow chart explain the production of ethanol form sugar 1 cane. 0 CO 1 4 state the various effect of using bio-diesel in I. 8 With a neat sketch.engines 1 0 1 0 CO 1 CO 1 1 0 1 0 1 0 1 0 CO 2 CO 2 CO 2 CO 2 1 0 1 0 1 0 1 0 CO 2 CO 2 CO 2 CO 2 PART-B 5 Explain Digester Design Considerations 6 How biodiesel is produced from edible and non-edible oils. 8 With a neat sketch. Sterling cycle. CO2. 1 0 CO 1 3 With a neat flow chart. describe a bio-mass based steam power plant . describe a bio-mass based steam power plant CO1. Rankine cyle.C. state the modifications necessary for SI and CI Engines for use of Bio-gas. 7 Describe briefly Brayton cycle. Rankine cyle. explain the production of ethanol from wood by acid hydrolysis.2 With the help of neat sketches. 7 Describe briefly Brayton cycle. The fundamentals of residual biomass and energy crops. Sterling cycle. The fundamentals of biomass conversion processes and devices PART-B 5 Explain Digester Design Considerations 6 How biodiesel is produced from edible and non-edible oils. modifications in design are needed. For sub-soil condition and high water table areas. 4. Period of digestion. 8. The production slows down considerably below 20°C In the mesophilic range the usual of gas production in the Indian biogas plants. the contents if any. 3. Type of the cover. Information about sub-soil condition and water table. methanogenic bacteria grow best at temperatures of 330 . The climate condition of the region.40°C The rate of gas production approximately doubles up for every 10°C rise in temperature between 15°C and 35°C and doubles between 35°C and 55°C (thermophilic range). This depends on mainly upon the temperature of digestion It is well known fact the production of biogas through anaerobic digestion of the biomass is dependent on the temperature. The cover may be a fixed one or floating.CO1. Methods of stirring. A number of factors are to be taken into account to arrive an optimum size of a biogas plant. Hence a digester operating at 15°C has to have a volume four times greater than the one at 35°C and eight times the one at 55°C to yield the same daily production of the digester. 6. The period of digestion‘t’ is fixed by the time necessary to produce a satisfactory digested sludge. The fundamentals of residual biomass and energy crops. Efficiency of collection of the raw waste. These are 1. The capacity of the digestion tank may be formulated is as The required capacities of digestion tanks may be calculated on the basis of destruction 2/3 of the organic matter in slurry and the conversion of 1/4 of what is destroyed into mineral matter and the remaining to gases. Explain Digester Design Considerations Digester Design Considerations Digestion tanks may be of any convenient shape and provided with a cover to retain the gas. . Method of adding the raw waste and removing digested slurry. 5. If the clay type soils maximum shrinkage of soil is possible and hence at an interval of 61 cm height one concrete ring structure around the digester might help in strengthening the digester. The volume of waste to be digested daily. The availability of other cellulosic fermentable waste in that area. The type and amount of waste available for digestion consistently. 2. and 10. 9. The fundamentals of biomass conversion processes and devices 5. CO2. 7. Hence if the gas requirement and duration of cycle are known. According to these factors the requirement of gas will have to be worked out and this has to be tallied with the availability of feed materials to decide the size of capsule module.1 times the volume of the slurry. the temperatures are required to he maintained at nearly constant value because the thermophilic bacteria are highly sensitive to fluctuation in the temperature. Suitability of Raw Material. Normally 1 kg of wet dung is mixed with 1 kg of water to get the slurry. and carbon content is 25 times that of nitrogen. For operation of the digester in the thermophilic range. Sterling cycle. construction of plants above ground with usual backing and soil grouting might also be considered in such areas. Retention time depends on the climatic conditions. In temperature climate with a definite drop in temperature during the winter. Normally the weight of dung in a dung vegetable mixture should be maintained above 50%. 1 kg of dry dung gives 0. The ratio of dry dung to water in wet dung is 1: 4. the retention time may have to be 40 to 60 days. 7. In high water table areas. Hence the total volume of the digester can be taken as 1. Besides this. and so size of the digester. A gas space of 10% of this volume could be provided in the digester.186 m3 of gas.The ultimate concentration of solids in the slurry should be between 7 and 9%. tropical prone climate. . The amount of dry solids in cowdung is 18%. the Deenbandhu model whose entire structure goes upto 1. 30 to 40 days retention time would be sufficient. The duration of each cycle depends on the temperature. If the availability of clung is less and will meet the user's fertilizers requirements but leave Min short of gas) then he can substitute a portion of vegetable waste for an equal amount of dung (dry) This will enable him to get more gas for the same amount of fertilizer. In such cases it is necessary to maintain C/N ratio. The nitrogen content in dry dung is 1. the retention time may be 60 to 90 days. For hot. At 15°C. The Ganesh model of biogas plant in which 4 to 5 well rings of sufficient diameter are placed one over the other and cemented together at the joints seems to work well in areas comprising of sandy soil.5 m below ground level is quite suitable. Rankine cyle. A leak-proof two-wall system with aqua-proof cementing might also help in enhancing the gas output .2 to 1. In hot regions with a period of winter. Volume of Digester for Biogas Production using Cow dung only. then the amount of water and dung needed can be estimated. This ratio should be maintained between 30 and 35 by properly varying the quantities of other biodegrable materials.Describe briefly Brayton cycle.7%. The volume of the digester is equivalent to the volume of slurry. This thermodynamic cycle is represented on p-V and T-s coordinates. is similar to diesel cycle in compression and heat addition. Heat rejection and heat addition takes place at constant temperature.Stirling Cycle stirling cycle is a thermodynamic cycle consists of two isothermal and two isochoric processes. This cycle consists of two reversible adiabatic or isentropic processes and two constant pressure processes. Pressure-volume and Temperature-entropy diagram Where. The isentropic expansion of diesel cycle is further extended followed by constant pressure heat rejection. . 1-2: Isothermal compression 2-3: Constant volume cooling 3-4: Isothermal exoansion 4-1: Contant volume heating From the p-V and T-s diagram of stirling cycle it is clear that the amount of heat addition and heat rejection during constant volume is same. Heat supplied = Work done during isothermal expansion Heat rejected by the air during isothermal compression Work done = heat supplied – heat rejected Thermal efficiency can be given by the equation Brayton Cycle The air-standard Brayton cycle is a theoretical cycle for gas turbines. p-V and T-s diagram for the air-standard Brayton cycle Where. Consider the idealized four-steady-state-process cycle in which state 1 is saturated liquid and state 3 is either saturated vapor or superheated vapor. The various processes in simple Rankine cycle are: 1–2: Reversible adiabatic pumping process in the pump. This system is termed the Rankine cycle and is the model for the simple steam power plant. 1-2: Isentropic process 2-3: Isobaric process 3-4: Isentropic Process 4-1: Isobaric process Thermal Efficiency can be calculated by the formula Where ‘k’ is the specific heat ratio Cp/Cv. 3–4: Reversible adiabatic expansion in the turbine (or other prime mover such as a steam engine). Simple Rankine Cycle The simple Rankine cycle is also a reversible cycle. 4–1: Constant-pressure transfer of heat in the condenser. 2–3: Constant-pressure transfer of heat in the boiler. . It is convenient to show the states and processes on a T–s diagram. They burn biomass directly to produce highpressure steam that drives a turbine generator to make electricity. Seasonal heating requirements will impact the CHP system efficiency. from the standard biomass electricity-only systems with efficiencies of approximately 20%. These combined heat and power (CHP) systems greatly increase overall energy efficiency to approximately 80%. The thermal efficiency is defined by the relation 8. For a steam cycle. the extracted or spent steam from the power plant is also used for manufacturing processes or to heat buildings. heat transfer and work may be represented by various areas on the T–s diagram.Figure 2: Temperature vs entropy diagram of Rankine cycle The Rankine cycle also includes the possibility of superheating the vapor. In some biomass industries. A simple biomass electric generation system is made up of several key components. The heat transferred to the working fluid is represented by area a–2–2’–3–b–a and the heat transferred from the working fluid by area a–1–4–b–a. With a neat sketch. From the first law we can conclude that the area representing the work is the difference between these two areas—area 1–2–2’–3–4–1. as cycle 1–2–3’–4’–1. describe a bio-mass based steam power plant BIOMASS BASED STEAM POWER PLANT DESCRIPTION Most biopower plants use direct-fired combustion systems. this includes some combination of the following items: Fuel storage and handling equipment Combustor / furnace Boiler Pumps . If kinetic and potential energy changes are neglected. . and reduce the efficiency of the boiler. wet basis. which is fed into a boiler to generate steam. but this method will incur significant cost in labor and equipment operations and maintenance . depending on fuel properties and local. or an electrostatic precipitator. Direct combustion systems feed a biomass feedstock into a combustor or furnace. sawdust. Most wood chips produced from green lumber will have a moisture content of 40% to 55%.100 pounds of water. This is the case with both small grate-fired plants and large suspension-fired plants. In addition. state. which spins to run a generator and produce electricity. emission controls for unburned hydrocarbons. biomass is burned in a combustor or furnace to generate hot gas. stackers. Fans Steam turbine Generator Condenser Cooling tower Exhaust / emissions controls System controls (automated). or bio-oil. The biggest problems with biomass-fired plants are in handling and pre-processing the fuel. Wood chip-fired electric power systems typically use one dry ton per megawatt-hour of electricity production. belts. oxides of nitrogen. Drying the biomass before combusting or gasifying it improves the overall process efficiency. and is listed in order of increasing capital cost and effectiveness. Boiler fuel can include wood chips. and Federal regulations. Steam from the boiler is then expanded through a steam turbine. which means that a ton of green fuel will contain 800 to 1. but may not be economically viable in many cases. This water will reduce the recoverable energy content of the material. where the biomass is burned with excess air to heat water in a boiler to create steam. How Does it Work? In a direct combustion system. can be used to transfer biomass from the piles to the bunkers. This approximation is typical of wet wood systems and is useful for a first approximation of fuel use and storage requirements but the actual value will vary with system efficiency. and pneumatic transport. A system using wood chips. In general. Emission controls might include a cyclone or multi-cyclone. sawdust. An automated control system conveys the fuel from the outside storage area using some combination of cranes. pellets. The primary function of all of the equipment listed is particulate matter control. like front loaders. and sulfur might be required. a baghouse. Cyclones and multi-cyclones can be used as pre-collectors to remove larger particles upstream of a baghouse (fabric filter) or electrostatic precipitator. Manual equipment. augers. front-end loaders. all biomass systems require fuel storage space and some type of fuel handling equipment and controls. which is expanded through a steam turbine or steam engine to produce mechanical or electrical energy. Exhaust systems are used to vent combustion by-products to the environment. reclaimers. or pellets typically use a bunker or silo for short-term storage and an outside fuel yard for larger storage. as the water must be evaporated in the first stages of combustion. processed biomass is the boiler fuel that produces steam to operate a steam turbine and generator to make electricity.In a direct combustion system. .