Research On Simultaneous Decarbonization And Desulfurization By Aqueous Ammonia From Coal-fired Flue Gas

As a chemical absorbent to purify the coal-fired flue gas, ammonia solution embodies the superiority for its high absorption capacity, low energy consumption and the possibility of multi-pollutant removal. Research on the use of ammonia solution of lower concentration to remove CO₂ and SO₂ simutaneously from coal-fired flue gas is shown in this thesis. Influencing factors, modelling and the comparison of the experimental results between MEA and ammonia solution on simultaneous decarbonization and desulfurization are investigated.Research of spraying the ammonia solution into the packed column to remove the CO₂ and SO₂ simutaneously is conducted in this thesis. The results show that the CO₂ removal efficiency would increase by the rise of mass fraction of ammonia solution, liquid gas ratio or the decrease of initial CO₂ concentration. The diminution of pH value is not good for CO₂ removal, however, there exists a fluctuation around 10.2; In the range of 15℃⁶0℃, the highest removal efficiency occurres at 35℃; The factors mentioned above have very little effect on the SO₂ removal, which basicly maintains over 99%. While the increase of SO₂ concentration leads to the decrease of CO₂ removal efficiency. The continuous cycle operation shows that ammonia supplement experiment would extend the time of high removal efficiency. The aerosol concentration at the outlet of the packed column would rise along with the increase of mass fraction of ammonia solution, reaction temperature, pH and liquid gas ratio.The model of experiment process is established, and then the comparison between the experimental and the simulation results, which are proved to be very consistent at last, is performed. Then the model is used to predict the constituents of rich liquid after desulfurization and decarbonization, NH4HCO3 and（NH4）2SO3 are considerd to be the main products.In the comparative study of MEA and ammonia solution, the absorption experiments on the homemade bubbling bed shows that the absorption ability of ammonia solution is higher than MEA. Study on the influence of various factors in the packing column, which is closer to the actual situation, reveales that ammonia solution in the lower concentration could achieve high removal efficiency of different SO₂ concentrations and CO₂ concentrations, and the increase of liquid gas ratio could increase the removal efficiency of the both two. The optimum reaction temperatures of them are 35 ℃and 45℃, respectively. The CO₂ and SO₂ removal efficiency decreases significantly as the pH value goes down. Through the preliminary experiment of improved ammonium method, we find that even a little MEA added into the ammonia solution could increase the removal capacity of absorbent and accelerate the reaction rate obviously.