The invention relates to a method for producing 
sulfuric acid and co-producing 
calcium carbide by 
phosphogypsum, and belongs to the technical field of 
environmental protection. According to the method, 
phosphogypsum is subjected to a 
water washing and purification pretreatment by a multi-stage 
cyclone; then the pretreated 
phosphogypsum is dried and dewatered; the dewatered phosphogypsum enters a multi-stage suspension 
heat exchanger to carry out preheating; the hot state 
gypsum enters a circulating 
fluidized bed decomposing furnace, then primary air and secondary air are respectively introduced to carry out decompositions; high temperature 
sulfur dioxide-containing 
flue gas discharged from the top of the circulating 
fluidized bed decomposing furnace enters the multi-stage suspension 
heat exchanger to carry out heat exchanging and cooling with the cold state 
gypsum; dust in the cooled hot 
flue gas is removed by a multi-stage dust removing device; the dust-removed 
flue gas enters an 
acid washing and purification 
system to further remove the dust and the gaseous impurities in the 
flue gas; the purified and cleaned 
flue gas is conveyed into an acid preparation 
system to produce the 
sulfuric acid product; the hot state 
calcium oxide discharged from the bottom of the circulating 
fluidized bed decomposing furnace is cooled, and conveyed into a sealed 
calcium carbide furnace to carry out an electrical arc reaction with a carbon material to generate the 
calcium carbide product; the high temperature furnace gas discharged from the top of the sealed 
calcium carbide furnace is directly conveyed into the decomposing furnace, wherein the high temperature furnace gas is adopted as a fuel and a 
reducing agent. The method of the present invention has good 
environmental protection benefits and strong economic advantages.