Research On Thermal Desorption Technology Of HPP-SO₂Absorption Solution

Based on thermal desorption process of HPP-SO2absorption solutions, thereinforcements of adding acids into the solutions on thermal desorption process arestudied. Thermal desorption parameters are investigated and reaction dynamics ofdesorption reaction is calculated. The effects of the synergism of thermal desorptionwith vacuum desorption is experimented, as well as thermal desorption with nitrogenstripping desorption in this thesis.By adding sulfuric acid, phosphoric acid, boxic acid, oxalic acid, acetic acid, citricaicd and adipic acid into1,4-bis-(2-hydroxypropyl)-piperazine-SO2absorption solutionsrespectively, the influences of the species of adding acids and their combination onthemal desorption are investigated. Results show that the promoting effect is improvedby adding more acids. Adding sulfuric acid, phosphoric acid and oxalic acid have betterdesorption effect than adding acetic acid, citric acid and adipic acid, except boric acidwhich plays nothing on promoting the desorption process of the solution.The combination of sulfuric acid/phosphoric acid can improve the effect of thermaldesorption furthermore. Compared with1,4-bis-(2-hydroxypyl)-piperazine/sulfuric acidsolution with pH6.20, the saturation absorption concentrations of SO2of thecombination solution of acids of1,4-bis-(2-hydroxypyl)-piperazine with pH4.80declines16%～17%in per absorption/absorption cycle. However, the combinationsolution has higher desorption percentage, resulting in similar effective absorptionconcentrations of SO2. The combination solution performs stabily on dealing with SO2after five times recycle.Single factor experiment method is employed in testing the effects of thermaldesorption parameters such as thermal desorption temperature, HPP concentration, SO2concentration on thermal desorption process. Results indicate that SO2desorptionpercentage raise with the increase of desorption temperature and SO2concentration, andwith the reducment of HPP concentration. SO2desorption rate is improved byamplifying desortion temperature. Suitable desorption temperature range is100～102℃and suitable SO2concentration at the beginning of desorption is50%～100%of thesaturation concentration, while pH of the lean solution is5.60～5.80.Reaction dynamics of thermal desorption reaction of1,4–bis-(2-hydroxypyl)–piperazine-sulfuric acid-SO2absorption solution is calculated roughly to investigate the relationships of dynamics parameters with desorption temperature and sulfuric acidconcentration. Results show that apparent activation energy of Ea of desorption reactionis69.92kJ/mol. And apparent reaction order of n of thermal desorption declines whileapparent reaction rate constant raises with the increase of desorption temperature. Withamplifing sulfuric acid concentration in the solution, thermal desorption reactionapproaches to first order reaction.The influences of the synergism of thermal desorption with vacuum desorption, andthermal desorption with nitrogen stripping on thermal desorption effects are investigated,separately. Results display that vacuum desorption conduces to thermal desorptionremarkably with vacuum degree of0.004MPa～0.04MPa with desorption percentageof SO2about95%. Boiling point of the solution declines with aggrandizement ofvacuum degree. Among the range of50～100mL/min of nitrogen flux, desorptionpercentage of SO2raises with increase of nitrogen flux, and is about95%.