The analysis of coal indicates 75 wt% C, 17% H, 2% S, and the balance noncombustible ash. The coal is burned at a rate of 5000 kg/h, and the feed rate of air to the furnace is 50 kmol/min. All of the ash and 6% of the carbon in the fuel leave the furnace as a molten slag; the remainder of the carbon leaves in the stack gas as CO and CO2; the hydrogen in the coal is oxidized to water, and the sulphur emerges as SO2. The selectivity of CO2 to CO production is 10:1. (a) Calculate the percent excess air fed to the reactor. (b) Calculate the mole fractions of the gaseous pollutants – CO and SO2 – in the stack gas. (c) Emitted suplhur dioxide by itself is a health hazard, but it is a more serious threat to the environment, as a precursor to acid rain. Under the catalytic action of sunlight, the sulphur dioxide is oxidised to sulphur trioxide, which in turn combines with water vapor to vorm sulphuric acid, which eventually returns to earth as rainfall. Acid rain formed in this manner has caused extensive damage to forests, fields and lakes in many parts of the world. For the furnace described above, calculate the rate of formation of sulphuric acid (kg/h) if all the emitted SO2 is converted in the indicated matter.
The analysis of coal indicates 75 wt% C, 17% H, 2% S, and the balance noncombustible ash. The coal is
burned at a rate of 5000 kg/h, and the feed rate of air to the furnace is 50 kmol/min. All of the ash and 6% of
the carbon in the fuel leave the furnace as a molten slag; the remainder of the carbon leaves in the stack gas
as CO and CO2; the hydrogen in the coal is oxidized to water, and the sulphur emerges as SO2. The selectivity
of CO2 to CO production is 10:1.
(a) Calculate the percent excess air fed to the reactor.
(b) Calculate the mole fractions of the gaseous pollutants – CO and SO2 – in the stack gas.
(c) Emitted suplhur dioxide by itself is a health hazard, but it is a more serious threat to the environment,
as a precursor to acid rain. Under the catalytic action of sunlight, the sulphur dioxide is oxidised to
sulphur trioxide, which in turn combines with water vapor to vorm sulphuric acid, which eventually
returns to earth as rainfall. Acid rain formed in this manner has caused extensive damage to forests,
fields and lakes in many parts of the world. For the furnace described above, calculate the rate of
formation of sulphuric acid (kg/h) if all the emitted SO2 is converted in the indicated matter.
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