Milling process

Abstract

Process for milling a substance selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, and trona, in which the substance is milled with a cleaning agent in a mill for the purpose of obtaining a powder with a mean diameter of less than 100 μm and of inhibiting the formation of incrustations in the mill. In a process for scrubbing a flue gas contaminated by a volatile acid compound, the powder is injected in the flue gas.

1 . A process for scrubbing a flue gas contaminated by a volatile acid compound, in which a reactant is subjected to a milling operation in order to reduce it to the state of a powder with a mean diameter of less than 50 μm, and said reactant is injected into the flue gas,
 wherein the milling operation comprises: mixing a substance selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, and trona with a cleaning agent and milling the mixture into a mill, for the purpose of obtaining the reactant powder with a mean diameter of less than 50 μm and of inhibiting the formation of incrustations in the mill; and 
 wherein the cleaning agent comprises at least one composition selected from the group consisting of zeolites, dolomite, magnesium hydroxycarbonate, lime, sodium chloride, zinc chloride, sodium sulfate, calcium fluoride, hydrocarbons, talc, fly ash, fatty acids, and fatty acid salts. 
 
     
     
         2 . The process according to  claim 1 , wherein the cleaning agent comprises a fatty acid or a fatty acid salt. 
     
     
         3 . The process according to  claim 2 , wherein the fatty acid or fatty acid salt is selected from the group consisting of calcium stearate, magnesium stearate, and soaps. 
     
     
         4 . The process according to  claim 1 , wherein the cleaning agent is employed in an amount from 0.2 to 7 parts by weight per 100 parts by weight of the substance. 
     
     
         5 . The process according to  claim 1 , wherein the substance is employed in the state of granules with a mean diameter of greater than twice that of the powder obtained. 
     
     
         6 . The process according to  claim 1 , wherein the mill is an impact mill. 
     
     
         7 . The process according to  claim 6 , wherein the impact mill comprises a hammer mill. 
     
     
         8 . The process according to  claim 1 , wherein the powder collected from the milling operation undergoes a particle size classification before its injection into the flue gas. 
     
     
         9 . The process according to  claim 1 , wherein the reactant injection is carried out by means of a mechanical blower. 
     
     
         10 . The process according to  claim 9 , wherein the blower is designed to convey the powder in a stream of air. 
     
     
         11 . The process according to  claim 1 , wherein the substance is employed in the state of granules with a mean diameter D m  of particle sizes from 150 to 250 μm. 
     
     
         12 . The process according to  claim 1 , wherein the substance is employed in the state of particles with a mean diameter of between 5 and 10 times greater than the mean diameter of the powder obtained. 
     
     
         13 . The process according to  claim 1 , wherein the amount of cleaning agent used does not exceed 20 parts by weight per 100 parts by weight of the substance being milled. 
     
     
         14 . The process according to  claim 2 , wherein the amount of cleaning agent used ranges from 0.15 to 1.0 parts by weight per 100 parts by weight of the substance undergoing milling. 
     
     
         15 . The process according to  claim 1 , wherein the powder has a particle size slope of less than 5. 
     
     
         16 . The process according to  claim 1 , wherein the powder has a mean particle diameter between 10 and 30 μm and a particle size slope from 1 to 3. 
     
     
         17 . The process according to  claim 2 , wherein the fatty acid or fatty acid salt is stearic acid or a stearate.