Question 10 on the afternoon of the first day of the 2014 Chemistry exam
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10. To produce 15 tons of paper, 90 tons of water, 12,750 kWh of electricity, and 37.5 tons of low-pressure steam are required. If the energy conversion factors for water, electricity, and low-pressure steam are 0.0857 kgce/t, 0.1229 kgce/(kW·h), and 0.1286 kgce/kg respectively, what is the value of the unit comprehensive energy consumption (in kgce) for producing this amount of paper? Hint: What is kgce in terms of kilogram of standard coal? (A) 426 (B) 1032 (C) 2146 (D) 6397?
This topic features two super-large tables, and there are also little traps inside!
Very large tables are for professional cases; this is for basic knowledge. But the traps are all the same; they’re all unit traps. Another trap is the comprehensive energy consumption per unit; initially, the total energy consumption is calculated to be 6397, but that’s not the correct answer. What is required is the energy consumption per unit of product. Here comes the question: is the unit of product measured in tons or in kilograms? The question does not state it explicitly, but apart from the 15 tons of product, one answer of 426.49 is found, which is close to answer A. There are too many pitfalls in this question.
This post was last edited by ydm4585 on 2015-6-19 at 11:02. Regarding the comprehensive energy consumption per unit, it might indeed be necessary to divide by 15. Generally, the unit used to measure energy consumption is kg of standard coal per ton; experts with experience are requested to provide their judgment on this matter.
It’s very simple – I don’t have the energy consumption standards here; you can look them up by yourself. It should take less than 5 minutes to find them!
There’s no need for any standards for this; calculating energy consumption is quite simple anyway. It is to multiply each by the amount of energy used according to these standards and then add them together. The concept of energy consumption per unit actually lacks two words: product. It only makes sense to compare the energy consumption per unit of product. Therefore, the denominator must be divided by the total amount of products produced over the same energy consumption period.