One is to mix it with hydrogen sulfide gas to produce elemental sulfur by a redox reaction, and the other is to use lime (calcium oxide) to neutralize it in an acid/base reaction.
a. Write the chemical equation for each process.
b. Assuming both processes are equally efficient, which would you recommend for use in a home furnace? Explain.
SO2 + H2S –> S + H2O
In this reaction the sulfur in SO2 has a +4 oxidation state. Hydrogen sulfide has S in the -2 state. Both end up as element as sulfur. S4+ gains 4 electrons and is reduced, while S2- is oxidized as it loses 2 electrons to form sulfur.
4H+ + SO2 + 4e- –> S + 2H2O
2(H2S –> S + 2H+ + 2e-)
——————————————-
4H+ + SO2 + 2H2S –> 3S + 2H2O + 4H+
simplfy:
SO2(g) + 2H2S(g) –> 3S(s) + 2H2O(l)
In the second case we are reacting sulfur dioxide which is the acid anhydride of H2SO3, and CaO which is the basic anhydride of Ca(OH)2. So this is sort of an acid/base reaction. We get the salt, without the water.
SO2(g) + CaO(s) –> CaSO3(s)
For home use I would suggest that the second reaction would be much easier to deal with. There would be no smelly, dangerous hydrogen sulfide gas to store and possibly release to the environment. The flue gases would run through a set of baffles and grills coated in CaO so that there would be a large surface are with which the flue gases containing SO2 would come into contact. This would have the added benefit of trapping CO2 as calcium carbonate.
You DON’T want any hydrogen sulfide gas around your house. 1 ppm will give you a headache and 10 will kill you if you give it a chance. Modern oil for home heating will not have the sulfur it once had. It is used for diesel engines which now have cat converters tht will be sulfated if the fuel is too high in sulfur.