Energy Conservation in Industry Questions and Answers

Answer: C

Correct answer: exceeds its target

Certificates are issued for the saving achieved beyond the target, one for each tonne of oil equivalent. A plant that merely meets its target has complied and earns nothing; one that falls short must buy certificates from those that have earned them, which is what creates the market.

Answer: D

Expressing every fuel and electricity in a common unit of oil equivalent lets a coal saving in one sector trade against an electricity saving in another. One such tonne is ten million kilocalories, about 11 630 kilowatt hours.

Answer: A

Correct answer: where they cost least

Every plant faces a different marginal cost of saving energy, and trading lets the sector’s total obligation be met by whoever can meet it most cheaply, the others paying them to do so. The physical reduction is the same as under a rigid per-plant rule, and the cost of achieving it is lower - which is the whole argument for a trading scheme.

Answer: B

Correct answer: a financial penalty

Failure to meet the target and failure to buy certificates covering the shortfall together attract a penalty proportional to the shortfall, so the scheme has a definite price of non-compliance. That price is what makes the certificate market work: a plant will buy certificates whenever they cost less than the penalty.

Answer: C

Correct answer: evaporating water from the kiln feed

The wet process feeds the kiln a slurry of thirty per cent or more water, and every tonne of that water must be evaporated using fuel before any calcination begins. The dry process grinds and blends the raw materials dry, so the heat goes into the chemistry rather than into boiling water, and the fuel per tonne of clinker falls by roughly a third.

Answer: D

The meal is calcined progressively in cyclones on its way down while the gas rises, so the kiln receives feed already hot and partly decarbonated. Adding stages recovers more but raises the pressure drop and the fan power.

Answer: A

Firing fuel in the calciner vessel drives off the carbon dioxide before the meal enters the kiln, so the kiln itself can be shorter and its output far greater for its size. It is the standard arrangement in any modern works.

Answer: B

Correct answer: cement produced

The clinker factor is the tonnes of clinker per tonne of finished cement, so a factor of 1 means the cement is all clinker and a factor of 0.7 means thirty per cent is something else. Since clinker is the part that took the kiln fuel, lowering the factor lowers the energy per tonne of cement directly.

Answer: C

Correct answer: needs no calcination

Most of the energy in cement making goes into calcining limestone, driving carbon dioxide out of calcium carbonate. Fly ash and slag are already the products of other high temperature processes and need no calcination at all, so every tonne of them substituted for clinker saves both the fuel and the process emissions of that tonne.

Answer: D

Grinding by compression between rollers and a table is inherently more efficient than tumbling steel balls, and the mill dries the feed with kiln gas at the same time. Grinding is the largest electrical load in a cement works.