The invention relates to a 
flue gas separation and purification 
system for producing electronic-grade 
sulfuric acid. The 
system comprises a dust remover, a washing 
tower, a 
demister, a nicotinic acid absorption 
tower, a nicotinic acid 
evaporation tank and a condensation tank which are sequentially connected, wherein the washing 
tower and the nicotinic acid absorption tower are further sequentially connected with a circulating tank and a nicotinic acid cooler, and 98% 
sulfuric acid solution is arranged in the bottom of the dust remover, the bottom of the 
demister and the circulating tank; a water inlet structure is arranged on the upper portion of the condensation tank body and comprises a first 
pipe plate arranged on the upper portion of the condensation tank body and a cooling water distribution 
pipe arranged on the inner side of the tank body, the upper portion of the cooling water distribution 
pipe is connected with a cooling water inlet pipe, a water distribution ring plate is arranged on the inner side of the cooling water distribution pipe, a notch is formed in the upper portion of the water distribution ring plate, and the lower portion of the water distribution ring plate is arranged on the first pipe plate. A heat exchange pipe is vertically arranged in the first pipe plate, and the top of the heat exchange pipe extends out of the first pipe plate and is evenly provided with a plurality of notches. By utilizing the 
system, high-purity 
sulfur trioxide can be obtained, and when the 
sulfur trioxide is condensed, no pressure exists in the heat exchange pipe, so that the safety is improved.