GATE 2020 CE (CE2) – Question 63

Air Pollution and Municipal Solid Wastes · Municipal solid wastes: generation, collection, transportation and management · 2 marks · Numerical answer

A waste-to-energy plant burns 1000 tonnes/day dry waste: C 35%, O 26%, H 10%, S 6%, N 3%, inert 20%. Air is 23% oxygen by mass. Assume complete conversion C→CO₂, H→H₂O, S→SO₂ and N→NO₂. Atomic weights H 1, C 12, N 14, O 16, S 32. Find theoretical air requirement (tonnes/day), nearest integer.

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Correct answer: 6963 to 6967

Explanation

Daily oxygen demand is $350(32/12)+100(8)+60(32/32)+30(32/14)-260=1601.9048$ tonnes. Divide by oxygen mass fraction 0.23: air requirement is 6964.8033 tonnes/day, rounded **6965**. Nitrogen oxidation is included as explicitly required.