Study on the Regeneration of Basic Aluminum Sulfate SO₂-Rich Solution by Vacuum Desorption

Abstract

Basic aluminum sulfate (BAS) wet flue gas desulfurization (FGD) is a promising renewable process used to remove sulfur dioxide (SO2) from flue gas, in which the regeneration of BAS SO2-loaded solution is of great importance for the reuse of BAS solution. In this paper, a novel regeneration method by vacuum desorption was developed to achieve superior regeneration performance for a BAS-rich solution. The operating parameter effect on SO2 desorption performance was thoroughly investigated in a lab-scale reactor. The experimental results demonstrated that the great decrease of pressure could significantly improve the regeneration performance, and high desorption temperature was favorable for SO2 desorption. Furthermore, it is worth determining the optimum components of a BAS-rich solution and initial sulfite concentration, considering the contradiction between the SO2 absorption performance and the regeneration performance. The increase of stirring speed in the liquid had a considerable positive effect on SO2 desorption efficiency. In addition, through a simple comparison with direct heating regeneration, it indicates that the utilization of vacuum regeneration could have the potential to improve the regeneration rate and lower the total energy consumption. Finally, the recycling experiments of the absorption–desorption process show that the BAS solution could be reused successfully to capture SO2 from flue gas by vacuum regeneration, while SO2 absorption efficiency would decrease to below 90% after 11 cycles, attributed to the inevitable oxidation of byproduct in the desulfurization process.

SO2 enhanced desorption from basic aluminum sulfate desulphurization–regeneration solution by falling-film evaporation

“…For instance, basic aluminum sulfate has been used to absorb SO 2 from ue gas, [9][10][11][12] which proves the high absorptive ability, and our team has carried out the mechanism research. 13 However, research has been rarely conducted on desorption of the basic aluminum sulfate desulphurization-regeneration solution, which is a key step in the renewable wet desulfuration process.…”

“…13 However, research has been rarely conducted on desorption of the basic aluminum sulfate desulphurization-regeneration solution, which is a key step in the renewable wet desulfuration process. Thus far, water bath heating 14 assisted by mechanical agitation, 15 microwaves, 16 ultrasonic waves [17][18][19] or vacuum-pumping 20 has been applied for enhanced desorption, exhibiting some improvements. However, these methods are limited by nonuniform heating and long desorption time; moreover, the relevant research is still at the laboratory stage, which is hard to industrialize.…”

Study on the kinetics of S(iv) oxidation in the basic aluminum sulfate wet flue gas desulfurization process

“…Compared with the limestone-gypsum method, basic aluminum sulfate (BAS) wet FGD technology has many advantages to remove SO 2 from ue gas, such as high desulfurization efficiency, circular utilization of the absorbent, rare fouling, low investment and energy consumption, etc. [4][5][6] During the desulfurization process, BAS as the effective absorbent reacts with SO 2 from ue gas to form the complex Al 2 (SO 4 ) 3 $Al 2 (SO 3 ) 3 , which could reversibly occur decomposition under the condition of heating due to its thermodynamic instability, and that would be further oxidized by oxygen in ue gas as the following reactions: 5,6…”

“…Through practice, it environmentally indicated that the latter might be the most promising regenerative desulfurization process, whereby Al 2 (SO 4 ) 3 $Al 2 (SO 3 ) 3 is decomposed by heating or reducing pressure, regenerating BAS with the recovery of pure SO 2 used to produce sulfur or sulfuric acid. 7 In particular, faced with a serious shortage of sulfur sources in China, there are better application prospects for BAS-desorption regeneration process.…”

“…In addition, our previous works have researched the performance of desulfurization and regeneration regarding to BAS-desorption regeneration method, further proving that it has an excellent feasibility for desulfurization with efficient recycling. 6,7 However, it should be noted that the oxidation of S(IV) in BAS solution is a key step of desulfurization process. For instance, for BAS-gypsum process, forced oxidation of the S(IV) in BAS rich solution is desirably needed, while retarding the S(IV) oxidation is of great importance with respect to BAS-desorption process.…”