Steam Boilers, Engines, Nozzles and Turbines Objective Questions - Part 7

151. 02 content in atmospheric air on weight basis is

(a) 21%
(b) 23%
(c) 30%
(d) 40%
(e ) 70%

Ans: b

152. Primary air is the air used to

(a) provide air around burners for obtaining optimum combustion
(b) transport and dry the coal
(c) convert CO (formed in lower zone of furnace) into C02 at higher zone
(d) air delivered by forced draft fan
(e) none of the above.

Ans: b

153. Sulfur content of fuels is very important to the plant operators because it

(a) has high heating value
(b) retards electric precipitation
(c) promotes complete combustion
(d) highly corrosive effect
(e) facilitates ash removal.

Ans: d

154. Presence of moisture in fuel oil would

(a) keep the burner tips cool
(b) aid in proper combustion
(c) cause sputtering, possibly extinguish¬ing flame
(d) clean the nozzles
(e) reduce flame length.

Ans: c

155. Gusset stays in a boiler are provided to

(a) prevent the bulging of flat surfaces
(b) avoid explosion in furnace
(c) prevent leakage of hot flue gases
(d) support furnace freely from top
(e) prevent atmospheric air leaking into furnace.

Ans: a

156. Water and sediment in fuel oil can be removed by

(a) heating the oil in the settling tanks
(b) cooling the oil in the settling tanks
(c) burning the oil
(d) suspension
(e) filtering.

Ans: a

157. Pour point of fuel oil is the

(a) lowest temperature at which oil will flow under set condition
(b) storage temperature
(c) temperature at which fuel is pumped through burners
(d) temperature at which oil is transported
(e) none of the above.

Ans: a

158. Secondary air is the used to

Ans: a

159. The behavior of coal in a furnace is determined by

(a) the content of sulfur
(b) the content of ash and heating value
(c) the proximate analysis
(d) the exact analysis
(e) its type.

Ans: c

160. Pick up wrong statement about desired properties of a good fuel

(a) high calorific value
(b) produce minimum smoke and gases
(c) ease in storing
(d) high ignition point
(e) economical

Ans: d

161. Sulphur in coal results in

(a) causing clinkering and slagging
(b) corroding air heaters
(c) spontaneous combustion during coal storage
(d) facilitating ash precipitation
(e) all of the above.

Ans: e

162. Caking coals are those which

(a) form lumps or masses of coke
(b) burn freely
(c) show little or no fusing action
(d) burn completely
(e) do not form ash.

Ans: a

163. Green coal, in order to be burnt, must be

(a) heated sufficiently
(b) burnt in excess air
(c) heated to its ignition point
(d) burnt as powder
(e) burnt as lumps.

Ans: c

164. The ultimate analysis of fuel lists

(a) various chemical constituents, carbon, hydrogen, oxygen etc, plus ash as per-cents by volume
(b) various chemical constituents, carbon, hydrogen, oxygen, etc, plus ash as per-cents by weight
(c) fuel constituents as percents by volume of moisture, volatile, fixed carbon and ash
(d) fuel constituents as percents by weight of moisture, volatile, fixed carbon and ash
(e) moisture and ash free heating value.

Ans: b

165. The proximate analysis of fuel lists

Ans: d

166. Tertiary air is the air used to

(a) provide air around burners for obtaining optimum combustion
(b) transport and dry the coal
(c) cool the scanners
(d) supply air for seigniors
(e) convert CO (formed in lower zone of furnace) into C02 at higher zone.

Ans: e

167. The safety valve on boiler drum compared to safety valve on superheated is set ai

(a) same value
(b) higher value
(c) lower value
(d) lower/higher depending on steam flow
(e) unpredictable.

Ans: b

168. Which is not correct statement about pulverized fuel firing

(a) high burning rate is possible
(b) heat release can be easily controlled
(c) fuel burns economically
(d) it is the best technique for burning high ash content fuel having low fusion ash
(e) separate mills are required to powder the coal.

Ans: d

169. The three “Ts” for good combustion are

(a) temperature, time, and turbulence
(b) total air, true fuel, and turbulence
(c) thorough mixing, total air, and temperature
(d) total air, time, and temperature
(e) none of the above.

Ans: a

170. Which is not correct statement about the function of furnace

(a) to provide proper conditions for continuous complete combustion
(b) mix fuel with air and ignite
(c) separate ash from coal
(d) maintain heat supply to prepare and ignite the incoming fuel
(e) to minimize radiation losses.

Ans: c

171. Which is not correct statement about effect of sulfur in fuel

(a) it has heating value
(b) it helps in electrostatic precipitation of ash in flue-gases
(c) it leads to corrosion of air heaters, ducting, etc. if flue gas exit temperature is low
(d) it erodes furnace walls
(e) none of the above.

Ans: d

172. Heating value of fuel used is as on fired basis. If it is reported for dry or moisture free fuel, then latter should be multiplied by the following factor to correct for as fired value

(a) (1- moisture content)
(b) (1 + moisture content)
(c) 1 + moisture content
(d) 1 – moisture content

Ans: a

173. Gradually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of

(a) higher effectiveness of boiler
(b) high calorific value coal being burnt
(c) fouling of heat transfer surfaces
(d) raising of steam temperature
(e) leakage of air.

Ans: c

174. Incomplete combustion can be best judged by

(a) smoky chimney exit
(b) excess air in flue gases
(c) measuring carbon mono-oxide in flue gases
(d) measuring temperature of flue gases at exit of furnace
(e) measuring oxygen in flue gases.

Ans: c

175. The capacity of induced draft fan compared to forced draft fan in a boiler is

(a) same
(b) more
(c) less
(d) less or more depending on size of boiler
(e) unpredictable.

Ans: b

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