This set of Energy Engineering MCQs focuses on “Ash and its Effects on Boiler Operation and Performance”.
1. Ash is widely used in the production of _______
b) Thermal wear
c) Food oxidants
Explanation: Ash is widely used in the production of cement. Fly ash is pozzolanic and develops self hardening characteristics. Concrete made of ash can yield improved workability and strength greater than all cement based concrete. The pozzolanic quality of ash lime mixture creates a healing of cracks in the pavement themselves.
2. Why is used for treating acidic soils?
a) To improve fertility of soil
b) For their better alkali values
c) To keep away insects
d) To loosen up the soil
Explanation: Due to their better alkali values, they are used for treating acidic soils. Its use for agricultural purposes is recently experimented in Japan and it is found that it supplies essential nutrients as sulfur, boron, calcium and zinc. It also adjusts pH to optimum levels for plant growth.
3. What is the India’s current total capacity of power plants installed?
Explanation: India’s current total installed capacity of power plants is 84000MW, out of which coal-fired thermal plants contribute 54000MW (65% of total). The World Bank estimated coal based power generation to increase by another 81000MW by 2010 which would have further increased fly ash load of 56 million tons per year.
4. How much percent of fly ash is, mixed with Portland cement?
a) 10 to 25%
b) 5 to 10%
c) 30 to 50%
Explanation: 10 to 25% dry fly ash can be used as during manufacture of cement or blended with finished Portland cement to produce Portland pozzolana cement whose strength is higher. The major drawback of this cement is its high cost and it requires more setting time.
5. Sintered light weight aggregates are produced by which method?
Explanation: Sintered light weight aggregates are produced by nodulisation of fly ash and sintering them at 1000oc to 1300oC. Unburnt fuel in the fly ash modules supports ignition. Sintered weight aggregate substitute’s chips in concrete reducing dead weight.
6. How much time period is fly ash stone powder cement bricks water cured?
a) A week
b) 2 weeks
c) 3 weeks
d) 1 month
Explanation: Fly ash stone powder cement bricks are manufactured by mixing weighted fly ash, cement and stone powder in a mixture and molded and pressed in brick making machine. The compacted bricks are water cure for a month. The compressive strength of these bricks varies from 70 to 110bar depending upon cement content.
7. How much amount of fly ash is made utilized by India?
a) 3 – 4%
b) 10 – 20%
c) 50 – 60%
d) 35 – 55%
Explanation: About 20% of coal ash in the coal is converted into bottom ash and 80% fly ash. India utilizes only 3 – 4% of fly ash generated as compared to 40% utilization in France and U.K. The government5t of India is imposing to achieve about 50% of fly ash in the upcoming years .
8. Which among the following when utilized gives good finishing on the both sides of the walls?
a) Cast-in-situ fly ash walls
b) Cellular light weight concrete
c) Sintered light weight aggregates
d) Fly ash cement putty
Explanation: Using high fly ash comprising of cement, lime fly ash and sand in appropriate proportions depending upon the quality of fly ash with pre-measured water cement ratio, cast-in-situ can be built. These can be cast to any thickness using steel shuttering. By using this system we can achieve 20% of economy, quicker construction, good finish on both sides of wall and more carpet area.
9. Which type of concrete is useful in high rise construction?
a) Cellular light weight concrete
b) Cast-in-situ fly ash
c) Fly ash stone powder bricks
d) Sintered light weight aggregates
Explanation: Cellular light weight cement can be manufactured by a process involving the mixing of fly ash, cement, coarse sand fine and a foaming agent. The slurry formed is poured in moulds and allowed to set. The blocks are then removed and cured by spraying water on the stack. The blocks are especially useful in high rise construction reducing the dead weight of the structure.
Sanfoundry Global Education & Learning Series – Energy Engineering.
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