Kinetic studies on the medium temperature calcium hydroxide sorbent injection FGD process.

摘要

Recent progress in dry sorbent injection flue gas desulfurization has resulted in a new process--medium-temperature sorbent injection process. Compared to conventional furnace injection, this new process exhibites equivalent SO{dollar}sb2{dollar} removal performance at a much lower operation temperature, allowing the injection point to move to a lower temperature region downstream of a furnace.; In this dissertation, kinetic studies of the medium-temperature Ca(OH){dollar}sb2{dollar} sorbent injection were conducted in entrained-flow reactors. Considering dehydration and carbonation reactions would take place simultaneously with sulfation reaction when a Ca(OH){dollar}sb2{dollar} particle is injected into a flue gas stream at medium temperatures, the experimental and kinetic analysis of each of the possible reactions were conducted independently over a broad spectrum of reaction conditions. Reaction conversions for the solitary carbonation and the solitary sulfation reactions in a temperature range of 600 to 1100{dollar}spcirc{dollar}F and with residence times within 1000 ms were determined. Mathematical models simulating the solitary carbonation and the solitary sulfation processes were developed based on the experimental data obtained. The activation energies and frequency factors for these reactions have been calculated.; Following the solitary reaction studies, experimental tests on the simultaneous dehydration, sulfation, and carbonation reactions of Ca(OH){dollar}sb2{dollar} were also conducted. The carbonation and sulfation conversions with a simulated flue gas in the reaction temperature range of 600-1100{dollar}spcirc{dollar}F and residence time within 100 ms were determined.; Based on the solitary reaction models, a comprehensive mathematical model was developed to describe the medium-temperature Ca(OH){dollar}sb2{dollar} sorbent injection process. This model incorporates the simultaneous dehydration, sulfation, and carbonation of Ca(OH){dollar}sb2{dollar}, as well as the further sulfation of the newly-formed CaCO{dollar}sb3{dollar}. The deactivation of sorbent caused by the loss of porosity for reactant gas diffusion was considered by introducing time-dependent activities which are commonly used to describe a catalyst deactivation process. The model was validated for both the sulfation and carbonation conversion data at the studied reaction temperatures. The model-predicted conversions were shown to be in good agreement with the experimental data.