Waste Heat Recovery in a Sulfuric Acid Production Unit
This paper is a contribution to the waste heat recovery in a diammonium phosphate production plant. Such plant is made of sulfuric acid, phosphoric acid, and diammonium phosphate production units.
The production of sulfuric acid by the contact process results in a significant waste of thermal energy associated with acid cooling by seawater. Such waste can exceed 30 MW for a production of 1500 tons/day. Furthermore, this process rejects about 150 t/h of gas at a temperature of 70 °C.
In this paper three systems are presented for waste heat recovery in the studied plant. First, a hot water loop is designed for the production of low-pressure steam. The thermal energy to be used in this loop comes from the sulfuric acid streams that need to be cooled in the process. Then, low-pressure steam is substituted by sulfuric acid for the concentration of the phosphoric acid produced in the same plant. Finally, a pre-concentration of the phosphoric acid is considered by direct contact with the rejected hot gases in a spray column.
A techno-economic study was conducted to evaluate the profitability of the proposed systems.
KeywordsWaste heat recovery Steam production Sulfuric acid Phosphoric acid
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