Model Question Paper - 2006 NATIONAL CERTIFICATION EXAMINATION FOR ENERGY AUDITORS AND ENERGY MANAGERS PAPER-2: ENERGY EFFICIENCY IN THERMAL UTILITIES General Instructions: Please check that this question paper contains 65 questions The question papers is divided into three sections All questions in all three sections are compulsory All parts of a question should be answered at one place -------------------------------------------------------------------------------------------- Section-I : Objective Type Questions (i) Answer all question of this section. (ii) Each question carries one mark. (iii) Put a () tick mark on the appropriate box in the answer book. 01 The A grade coals have calorific value (a) Greater then 6200 kcal/kg (b) Less then 6200 kcal/kg (c) Less then 1300 kcal/kg (d) Greater then 1300 kcal/kg 02 The smallest size of the coal (≈75 micron) is required in (a) Fluidized bed firing (b) Pulverized coal firing (c) Stoker firing (d) Hand firing 03 Calorific value of liquid and gaseous fuels is generally measured in terms of (a) kcal/m3 and kcal/N m3 respectively (b) kcal/N m3 and kcal/ m3 respectively (c) kcal/kg and kcal/ m3 respectively (d) kcal/ m3 and kcal/kg respectively 04 Which of the following agro-residues has the lowest gross calorific value (a) Deoiled Bran (b) Paddy Husk (c) Saw dust (d) Coconut shell 05 Under optimum combustion condition of fuel oil, the percentage of oxygen in flue gas will range between. (a) 0 to 0.1% (b) 2 to 3% (c) 12 to 13% (d) 22 to 23% 06 Heat generated in combustion on per kg basis, is the highest for (a) carbon (b) hydrogen (c) sulpher (d) oxygen 07 Ash fusion temperature of typical Indian coal is (a) 500ºC (b) 700ºC (c) 900ºC (d) 1100ºC 08 Stoichiometric Volumetric air to fuel ratio for complete combustion of natural gas ranges between (a) 9.5 to 10 (b) 14.5 to 15 (c) 18.5 to 19 (d) 22.5 to 23 09 With increase in percentage of excess air for combustion of a given fuel percentage of oxygen in flue gas. (a) increases (b) decreases (c) remains same (d) none of the above 10 Permissible limit of TDS in boiler a) increases for higher pressure boilers b) decreases for higher pressing boilers c) is independent of boiler pressure d) none of the above 11 Radiation losses from a boiler a) increase with increase in % its loading b) decrease with increase in % its loading c) are independent of % its loading d) none of the above. 12 An evaporation ratio (steam to fuel ratio) of an efficient oil fired boiler is in the range of___. a) 5 – 6 b) 13 – 16 c) 1-3 d) 7 – 9 13 Name the predominant loss component for furnace oil fed boiler. a) losses due to radiation and convention b) loss due to hydrogen in fuel c) loss due to dry flue gas d) loss due to moisture in fuel 14 A rise in conductivity of boiler feed water indicates ____ . a) drop in the contamination of feed water b) greater purity of feed water c) rise in the contamination of feed water d) it has got no relation with the contamination of feed water 15 De-aeration of boiler feed water is referred to as: a) removal of dissolved gases b) removal of silica c) removal of scales by blow down d) phosphate treatment of feed water 16 F & A (From and At) rating of the boiler is the amount of steam generated from (a) Water at 0ºC to steam at 100ºC (b) Water at 27ºC to steam at 100ºC (c) Water at 77ºC to steam at 100ºC (d) Water at 100ºC to steam at 100ºC 17 Demineralization in water treatment means (a) removal of total salts (b) removal of only hardness salts (c) removal of alkali salts (d) removal of non-hardness salts 18 Chemical de-aretion of feed water with sodium sulphate as oxygen scavenger removes oxygen but (a) decreases pH of the water (b) decreases TDS level of the water (c) increases TDS level of the water (d) None of the above 19 For industrial process heating, the best quality of steam is: a) dry saturated steam b) superheated steam c) wet steam d) high pressure steam 20 For flash steam calculation, flash steam quantity available depends upon ___ a) condensate pressure and flash steam pressure b) pressure of steam generated in boiler c) Steam enthalpy at atmospheric pressure d) Total heat of flash steam 21 Latent heat steam at critical point is a) Infinite b) 540 kcal c) zero d) none of the three 22 head loss due to flow of steam in a pipe line is proportional to a) velocity 4 b) velocity –4 c) velocity –2 d) velocity 2 23 Failure mode of bucket steam trap is a) open b) closed c) none of the two 24 Chances of water hammering will be largest in a) down inclined steam line b) up inclined steam line c) horizontal steam line d) none of the above 25 The temperature maintained in forging furnaces ranges between a) 700-850ºC b) 850-1000ºC c) 1000-1150ºC d) 1150-1250ºC 26 Radiation Recuperators are used for flue gas temperature of more than a) 800ºC b) 600ºC c) 400ºC d) 200ºC 27 The pressure drop as the exhaust gases pass through recuperator is of the order of a) 0.5 to 1.0 mm of H2O column b) 1.0 to 5.0 mm of H2O column c) 5.0 to 10 mm of H2O column d) 10 to 50 mm of H2O column 28 To retain the heat stored in furnace walls it is advisable to run a batch furnace in batch for a given load. a) 48 hrs every six days b) 8 hrs per day c) 24 hrs every third day d) none of the above 29 In large glass industries, the equipment connected with glass melting furnace for preheating the air is___. a) recuperators b) regenerators c) shell & tube heat exchanger d) heat wheels 30 The temperature which separates ‘ovens’ from ‘furnaces’ is a) 170ºC b) 270ºC c) 370ºC d) 470ºC 31 The axis of the oil fired burner in a furnace should be kept: a) slightly inclined towards the roof b) more inclined towards roof c) slightly inclined towards the stock d) parallel to stock 32 Higher excess air in an oil fired furnace would result in: a) increased furnace temperature b) increased heating rate c) reduced flame temperature d) none of the above 33 Which of the following is organic insulating material a) Expanded Polystyrene b) Calcium silicate c) Mineral wool c) None of the above 34 The melting temperature of the pure refractory compounds in highest for a) Alumina b) Lime c) Chromite d) Meginisia 35 The insulation material suitable for low temperature application is a) Mineral fibre b) Fibre glass c) Silica d) Polyurethane 36 The unit for thermal conductivity of insulation and refractories is ____. a) K.cal/m-hr-°C b) K.cal/ m²-hr-°C c) K.cal/m²-°C d) K.cal/ m-°C 37 The insulation which can be used for lining furnaces operating up to 1850ºC is: a) Alumina b) Zirconia c) Dolomite d) Calcium silicate 38 The material used to control SOx in the FBC boiler is a) Limestone b) Alumina c) Silica d) All of the above 39 The velocity of fluidizing air in atmospheric fluidized bed boiler is in the range of: a) Higher than 4.5 m/sec b) 1.2 – 3.7 m/sec c) Less than 1.2 m/sec d) 4-6 m/sec 40 In FBC boiler the combustion is carried out at a temperature a) closer to steam temperature b) at adiabatic combustion temperature c) at and above ash fusion temperature d) below ash fusion temperature of fuel used 41 Residence time in fluidized bed boiler a) is equal to conventional grate firing boiler b) is less then that in conventional grate firing boiler c) is little more then that in conventional grate firing boiler d) many times more then that in conventional grate firing boiler 42 The coal size used in AFBC boiler ranges. a) 1 μm-10 μm b) 1mm- 10mm c) 10mm-20mm d) 10 μm- 100mm 43 The overall conversion efficiency of a PFBC boiler in cogeneration mode is higher by a) 20-25% b) 10-12% c) 5-8% d) 1-3% 44 An economizer is used to recover waste heat from flue gas to heat a) stock b) combustion air c) feed water d) room air 45 In a shell and tube heat exchanger, the vapour stream is a) flown in the tubes b) contained on the shell side c) generally not used for heat exchange d) none of the above. 46 Major advantage of waste heat recovery in industry is: a) reduction in pollution b) increase in efficiency c) both a & b d) none of the above 47 Ceramic recuperators can withstand temperatures up to: a) 600 ºC b) 1300 ºC c) 1700ºC d) 950ºC 48 In a combined cycle power plant consisting of gas turbine and waste heat boiler, the exhaust gas temperature is ____. a) around 150 °C b) around 500 °C c) around 300 °C d) around 400 °C 49 The overall efficiency of combined cycle cogeneration is of the order of: a) 69 – 83 b) 90 – 95 c) 70 – 90 d) 55 – 60 50 Heat to power ratio of combined cycle cogeneration is in the range of------------- a) 4.0 – 5.0 b) 1.0 – 1.7 c) 2.0 – 10 d) 1.0 – 5.0 Section II: Short Descriptive Questions (i) Answer all TEN of the following questions. (ii) Each question carries FIVE marks S-1 Explain the significance of the ultimate analysis of the fuels from the combustion point of view. S-2 Explain why stack temperature in boilers can not be reduced below 160-170ºC S-3 List out the data required for calculation of boiler efficiency using ‘indirect method’. S-4 List the characteristic of steam which make it most popular for carrying energy S-5 Explain why furnaces should operate at slightly positive pressure? S-6 List advantages of ceramic fibre insulation? S-7 Calculate rate of heat loss from a furnace whose external surface (area 20 m2) is at temperature 70ºC placed in a room at 35ºC S-8 What is the principle of CFBC (circulating fluidized bed combustion) boiler? S-9 Discuss the advantage and disadvantage of Reciprocating engine (Internal combustion energy) in the cogeneration mode. S-10 Briefly explain the principle of ‘thermo compression’. Section III: Long Descriptive Questions (i) Answer all FIVE of the following questions. (ii) Each question carries TEN marks L-1 List various energy conservation opportunities in a boiler. L-2 Calculate the theoretical air requirements for CH4 on mass basis and percentage volume of CO2 (on dry basis) in flue gas. If the actual measured value of percentage of CO2 in flue gas is 10%, estimate excess air ratio L-3 Describe various consideration involved in retrofitting of FBC systems to conventional system. L-4 From the given diagram, evaluate (i) heat load on cooling tower (ii) power generation in MW. P=0.6MPa T=250ºC Q=5 MT/h P=0.2 Mpa kJ/cm2 h=2957.2 kJ/kg T=150ºC Q=50MT/h h=2768.8 kJ/kg P=4.5MPa T=500ºC Q=72MT/h h=3439.6 kJ/kg P=10 kPa T=45.8ºC Q=17MT/hr hf=191.8 kJ/kg CONDENSOR L-5 What are waste heat recovery boilers? Explain their need and benefits?