Modelling and simulation of an existing MSWI flue gas two-stage dry treatment

Power generation from municipal solid waste incineration (MSWI) is in widespread use as a technology for solid waste treatment and energy recovery. One of the main environmental issues posed by MSWI plants is the continuous emission of pollutants into the atmosphere. Among flue gas components, acid gases are of particular concern due to their high potential impact on the environment. The two-stage dry treatment is among the Best Available Technologies for an enhanced removal efficiency of acid gases. In the first stage the removal process is based on the reaction of acid gases with solid calcium hydroxide (slaked lime), while in the second stage removal is obtained by reaction with sodium bicarbonate. In the present study, design and process data from an existing Municipal Solid Waste Incinerator, where a flue gas two-stage treatment is adopted, were used to test a previously developed operational model. The model was implemented in a simulation software to describe both design and process conditions, taking also into account the recycle rate of solid products and unreacted calcium hydroxide in the first stage. Simulations were carried out with the aim of optimizing both reactant feed rates and amounts of solid wastes formed in the acid gas removal process.