The present study concerns the phosphoric slurry cooling using a vacuum system “flash cooler”. This system has a dual purpose, the first is to ensure the desired cooling of the phosphoric slurry and the second and the mainly purpose is to reduce the fluorine content in the exhaust gas outlet of the phosphate attack units. A simulation was made through the Aspen Plus software features of this vacuum system which is composed of a flash cooler to cool the slurry, a spray tower to clean the fluorinated gas and recovered it to a fluosilicic acid solution and a barometric condenser to create the vacuum all over the system. The determination of the different operating parameters of each device in order to minimize the amount of fluorine released into the atmosphere and maximizes his recovery as a solution of fluosilicic acid, were investigated. The obtained results confirmed the good performance of this system and showed that it is possible to cool the slurry to the desired phosphoric slurry temperature and get a good discount rate of fluorine released into the atmosphere. This pollutant is recovered as fluosilicic acid solution to 20% by mass.