(1) "Btu" means British thermal unit which is the heat required to raise the temperature of one pound of water through one Fahrenheit degree.
(2) Commencing July 1, 1970, no person shall burn liquid or solid fuels containing sulfur in excess of 2 pounds of sulfur per million Btu fired.
(3) Commencing July 1, 1971, no person shall burn liquid or solid fuels containing sulfur in excess of 1.5 pounds of sulfur per million Btu fired.
(4) Commencing July 1, 1972, no person shall burn liquid or solid fuels containing sulfur in excess of 1 pound of sulfur per million Btu fired.
(5) Commencing July 1, 1971, no person shall burn any gaseous fuel containing sulfur compounds in excess of 50 grains per 100 cubic feet of gaseous fuel, calculated as hydrogen sulfide at standard conditions. The provisions of (5) shall not apply to:
(a) The burning of sulfur, hydrogen sulfide, acid sludge or other sulfur compounds in the manufacturing of sulfur or sulfur compounds.
(b) The incinerating of waste gases provided that the gross heating value of such gases is less than 300 Btus per cubic foot at standard conditions and the fuel used to incinerate such waste gases does not contain sulfur or sulfur compounds in excess of the amount specified in this rule.
(c) The use of fuels where the gaseous products of combustion are used as raw materials for other processes.
(d) Small refineries (under 10,000 barrels per day crude oil charge) provided that they meet other provisions of this rule.
(6) The following are exceptions to this rule:
(a) A permit may be granted by the director to burn fuels containing sulfur in excess of the sulfur contents indicated in (2) through (5) provided it can be shown that the facility burning the fuel is fired at a rate of 1 million Btu per hour or less.
(b) For purpose of this rule, a higher sulfur-containing fuel may, upon application to the director, be utilized in (2) , (3) or (4) if such fuel is mixed with one or more lower sulfur-containing fuels which results in a mixture, the equivalent sulfur content of which is not in excess of the stated values when fired.
(c) The requirements of (2) , (3) , or (4) shall also be deemed to have been satisfied if, upon application to the director, a sulfur dioxide control process is applied to remove the sulfur dioxide from the gases emitted by burning of fuel of any sulfur content which results in an emission of sulfur in pounds per hour not in excess of the pounds per hour of sulfur that would have been emitted by burning fuel of the sulfur content indicated without such a cleaning device.