ENGINEERS ACADEMY Power Plant Steam Generators/ 1

QUESTION BANK

1. Match List-I (Type of ) and List-II 3. Radiation . (Classification of boiler) and select the correct 4. Convection superheater. answer using the codes given below the lists: List-I List-II In the case of Benson boiler, the correct sequence of the entry of water through these components is: A. Babcock and Wilcox 1. Forced circulation (a) 1, 2, 3, 4 (b) 1, 2, 4, 3 B. Lancashire 2. Fire tube (c) 2, 1, 3, 4 (d) 2, 1, 4, 3 C. La-mont 3. Water tube 5. Coal fired power plant boilers manufactured in D. Cochran 4. Vertical India generally use: Codes: (a) pulverized fuel combustion A B C D (b) fluidized bed combustion (a) 1 2 3 4 (c) circulating fluidized bed combustion (b) 2 3 4 1 (d) moving stoker firing system (c) 3 2 1 4 6. Once-through boilers will not have (d) 2 4 1 3 (a) Drums, headers and pumps 2. In forced circulation boilers, about 90% of water (b) Drums, steam separators and pumps is recirculated without evaporation. The (c) Drums, headers and steam separators circulation ratio is (d) Drums, headers and pumps (a) 0.1 (b) 0.9 7. Match List-I (Name of boiler) with List-II (c) 9 (d) 10 (Special features) and select the correct answer 3. Consider the following using the codes given below the lists: 1. Increasing evaporation rate using convection List-I List-II heat transfer from hot gases. A. Lancashire 1. High pressure water tube 2. Increasing evaporation rate using radiation. B. Cornish 2. Horizontal double fire tube 3. Protecting the refractory walls of the furnace. C. La-Mont 3. Vertical multiple fire tube 4. Increasing water circulation rate. D. Cochran 4. Low pressure inclined water The main reasons for providing water wall tube enclosure in high pressure boiler furances would 5. Horizontal single fire tube include Codes: (a) 2 and 3 (b) 1 and 3 A B C D (c) 1, 2 and 4 (d) 2 and 3 (a) 2 5 1 3 4. Consider the following components: (b) 2 4 3 1 1. Radiation evaporator. (c) 1 5 2 3 2. Economizers. (d) 5 4 1 3

# 100-102 Ram Nagar, Bambala Puliya, Email: [email protected] Pratap Nagar, Tonk Road Jaipur-33 Website: www.engineersacademy.org Ph.: 0141-6540911, +91-8094441777 ENGINEERS ACADEMY 2  Steam Generators/Boilers Mechanical Engg. 8. Benson boiler is one of the high pressure boilers 14. In a boiler 25kg of fuel is burnt per hour 150kJ having of enthalpy rise is required for conversion of 1kg (a) One drum steam from water. The feed water supplied per hour’s 220kg. Calculate the boiler efficiency if (b) One water drum and one calorific values of fuel is 5150 kJ /kg. (c) Three drums (a) 61% (b) 62% (d) No drum 9. Consider the following statements: (c) 63% (d) 65% 1. Forced circulation is always used in high 15. Match List I with List II and select the correct pressure power boilers. answer 2. Soot blowers are used for cleaning tube List I surfaces at regular intervals. A. Lancashier Boiler 3. Electrostatic precipitator is used to remove fly and form flue gases. B. La-mont Boiler Which of these statements are correct? C. Babcock & Wilcox Boiler (a) 1, 2 and 3 (b) 2 and 3 D. Cochran Boiler (c) 1 and 3 (d) 1 and 2 List II 10. Boilers operate at 1. Forced circulation (a) subcritical pressure 2. Fire tube (b) supercritical pressure 3. Water tube (c) subcritical as well supercritical pressures (d) critical pressure only 4. Vertical 11. In a boiler, feed water supplied per hour is 205 kg Codes: while coal fired per hour is 23 kg. Net enthalpy A B C D rise per kg of water is 145 kJ for conversion to steam. If the calorific value of coal is 2050 kJ/kg (a) 2 3 1 4 then the boiler efficiency will be (b) 1 2 3 4 (a) 78% (b) 74% (c) 2 1 3 4 (c) 62% (d) 59% (d) 4 1 3 2 12. In steam generators, a stoker acts as one of the 16. Which of the following is a water tube boiler? following devices. What is this device? (a) Locomoative boiler (a) Air preheating device (b) Steam superheating device (b) Cocharan boiler (c) Air superheating device (c) Babcock & Wilcox (d) Fuel feeding device (d) Lancasher boiler 13. Scale deposits in Benson Boiler are prevented 17. The water tubes in Babcox & Wilcox boiler are because inclined to (a) boiler is flushed out after every 4000 working (a) improve convective heat transfer hour (b) improve radiative heat transfer (b) forced circulation is used (c) shorter the size of the boiler (c) bore of tubing is small. (d) steam and water have same density (d) promote natural circulation of water

# 100-102 Ram Nagar, Bambala Puliya, Email: [email protected] Pratap Nagar, Tonk Road Jaipur-33 Website: www.engineersacademy.org Ph.: 0141-6540911, +91-8094441777 ENGINEERS ACADEMY Power Plant Steam Generators/Boilers 3 18. Which of the following is a forced circulation 21. In water tube boilers parallel sets of tubing are boiler ? used (a) Babcock and Wilcox (a) to reduce the friction loss in flow (b) Locomotive Boiler (b) to reduce the length of tubing (c) to increase the exposed surface area (c) Simon Carres Boiler (d) to improve heat transfer (d) Benson Boiler 22. With the use of condensate instead of using the 19. Feed water is heated by superheated steam in feed water, the deposition of salt in the boiler is (a) Benson Boiler (a) increased (b) Velox Boiler (b) prevented (c) Leoffler Boiler (c) dependent of other factors (d) Babcock and Wilox Boiler (d) None of the above 20. Steam from a high pressure boiler 23. A good condensing plant should have (a) is first superheated and then throttled (a) maximum cooling surface per kW capacity (b) is first throttled and then superheated (b) minimum cooling surface area per kW (c) is first superheated and cooled capacity (d) is fed into turbine without throttling (c) average cooling surface area per kW capacity (d) None of the above

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# 100-102 Ram Nagar, Bambala Puliya, Email: [email protected] Pratap Nagar, Tonk Road Jaipur-33 Website: www.engineersacademy.org Ph.: 0141-6540911, +91-8094441777 ENGINEERS ACADEMY 4  Steam Generators/Boilers Mechanical Engg. ANSWERS AND EXPLANATIONS 1. Ans. (c) 11. Ans. (c) Fire tube boilers: Mass of feed water = 205 kg/hr (i) Locomotive boiler (Horizontal boiler) Mass of coal = 23 kg/hr (ii) lancashire boiler Calorific value of coal = 2050 kJ/kg (iii) Net enthalpy rise = 145 kJ/kg of water (iv) Cochran boiler (verticale boiler) Water tube boilers: Total enthalpy rise = 145 × 205 (i) Babcox-wilcox boiler Net heat supplied by the coal = 23 × 2050 (ii) Lamont boiler (high pressure boiler) 145 205 Boiler efficiency  60% (iii) Benson boiler (High pressure boiler) 23 2050 2. Ans. (d) 12. Ans. (d) 3. Ans. (a) 13. Ans. (a) Heat transfer to water wall is predominately by 14. Ans. (a) radiation. Heat utilized = 220 × 150 = 33000kJ/hr. E  AT4 Heat supplied by fuel 4. Ans. (d) = 25 × 2150 = 53750 kJ /hr. 5. Ans. (a) Boiler efficiency Coal fired power plant boilers manufactured in heat utilized 33000 india generally use pulverized fuel combustion. =   0.61 6. Ans. (c) heat supplied by fuel 53750 7. Ans. (a) = 61% 8. Ans. (d) 15. Ans. (c) Benson Boiler is a typical high pressure, water 16. Ans. (c) tube, forced circulated once through boiler. This 17. Ans. (d) boiler does not have any drum. 18. Ans. (d) 9. Ans. (a) 19. Ans. (c) Forced circulation is required because at high pressure the density difference between steam 20. Ans. (c) and water is very less. 21. Ans. (a) 10. Ans. (c) 22. Ans. (b) NTPC-Talcher (Orissa) plant has sub-critical 23. Ans. (b) once-through boiler.

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# 100-102 Ram Nagar, Bambala Puliya, Email: [email protected] Pratap Nagar, Tonk Road Jaipur-33 Website: www.engineersacademy.org Ph.: 0141-6540911, +91-8094441777