Process And Equipment For Flue Gas Desulfurization On The Basis Of Pulse Bubbling And Aerodynamic Stirring

Sulfur dioxide is a major air pollutant and has significant impacts upon human health. In addition, the concentration of sulfur dioxide in the atmosphere can influence the habitat suitability for plant communities, as well as animal life. Sulfur dioxide emissions are a precursor to acid rain and atmospheric particulates.Due largely to China Environmental Bulletin,the amount anthropogenic emissions of sulfur dioxide released in the P.R.C. per year was about 20m tons, mainly from the burning of fossil fuels. Since Coal-based Energy consumption structure of should not change foreseeable short-term s, research on new innovative and high efficiency equipments and technologies of flue-gas desulfurization, a technology that enables sulfur dioxide to be chemically bound in power plants or other factory burning sulfur-containing coal or oil, seems particularly important to decrease in sulfur dioxide emissions.Approximately 85% of the FGD units worldwide are wet desulfurization technology, mostly were using lime or limestone wet scrubbing, which in the United States, Japan, and Germany wet FGD market shares is more than 90%.The core technology of Wet FGD is absorber, which had gone through three stages. The first Wet FGD technology generation of absorber were mainly refers to packed tower absorber and turbulent ball tower. Almost all of the first wet FGD generation technology were called lime-discarding desulfurization because of the desulfurizer being abandoned since it had desulfurization capacity reached saturation. The second generation Wet FGD technology generation of absorber replaced packing tower, turbulent ball tower and sieve tower with empty tower, which brought many good results such as simple internal structure, lower cost, reducing the fouling that are typical representatives of the spray tower and spray bubble column etc. The typical second Wet FGD generation absorbers were spray tower and jet bubbling column. Wherein the spray tower started earlier, the jet bubbling column is developing rapidly. The Jet bubbling column system, in which the dispersed phase is gas phase and the liquid phase is a continuous phase, synthesized sulfur dioxide absorption, calcium sulfate oxidized and crystallization, dust removal and other processes to the same reactor and had high desulfurization efficiency and dust efficiency. The typical process control operational pH range is usually 3 to 5,which lower pH environment in the absorber means a better rate of oxidation. Although there are many advantages, the jet bubbling column system were more complicated with higher the absorber pressure losses.Direction of the third Wet FGD generation of the absorber column is a large-scale and modular, while increasing the flow rate through the flue gas to increase the reaction field disturbances and turbulence, prolonged absorption of the flue gas in the liquid residence time to improving the absorption rate of sulfur dioxide and better desulfurization effect.Ring-gate type absorber belongs to is an improved jet bubbling absorber, with two typical characteristics which refer to a ring-gate-type gas distribution systems and tangential intake mode. The air flow runs tangentially into the annular gas passage, driving the liquid absorbent radially rotation. Pulsed gas flow passes through into the ring-gate hole and is cut by the radially rotating liquid absorbent into smaller bubbles at the gate hole. Bubbles rise up, forward and in the radial direction of the three-dimensional, while absorbing liquid stirred to generate pulsed bubbling. Sharp disturbed bubbling layer state extended contact time of gas and liquid the tower. Ring-gate type structure gas distribution combined single tangential inlet way to generate a pulsed bubble effect and increase the disturbance of the absorber, which are typical characteristics of the third FGD generation of towers and consistent with a high gas velocity to increase turbulence and desulfurization efficiency principles.Experiment results compared with the ring-gate type absorber and Japanese jet-tubing absorber show that pressure loss of ring-gate-type absorber is less than Japanese jet-tubing absorber with an equal amount intake flue gas volume and absorbing liquid height at the same level; and the bubbling layer height of ring-gate-type absorber is greater than the height of than Japanese jet-tubing absorber. In intake flow flue of 2800m3/h, the height of the ring bubbling layer grid type absorber repeatedly reach 1000mm or more, and the peak value of up to 1500mm with very intense disturbance inside liquid, While Jet bubbling tube absorber layer height is only about 700mm. When the mass concentration of the same amount was 1.37% CaCO3 solution as absorption liquid, flow flue of 2300 m3/h, sulfur dioxide concentration 3000mg/m3,absorbent pH values greater than 5.2, the desulfurization efficiency of the ring-gate-type absorber is higher than jet-tubing absorber, but when the pH is less than 5.2 because of no fresh slurry is added, the desulfurization efficiency of the ring-gate type absorption tower is lower than jet-tubing absorber.Theoretical analysis shows that while he diameter of the absorber to a certain extent, ring-gate type absorber tower center portion of the cloth presence of defects in the gas shortage, ring center portion of the gate-type absorption column there may be defects in the cloth gas shortage. In order to improve this defect, pneumatic devised stirred absorber was invented. Major improvements were the addition of the injection tube inside the ring-gate and installation float buoys in the annular gas passage stirrer, for reinforcing the absorber gas-phase solid-liquid mixing. No fixed pontoon agitator shaft, the buoy stirrer floats in the annular channel absorbing fluid level. There is no other source of energy, the kinetic energy of the rotation entirely by airflow within the annular channel, while the faster speed the flow rotation, the shorter the time spent stir.Experiment results compared with the pneumatic devised stirred absorber and Japanese jet-tubing absorber show that pressure loss of pneumatic devised stirred absorber is less than Japanese jet-tubing absorber with an equal amount intake flue gas volume. When intake flow flue of 2800m3/h, sulfur dioxide concentration 3400mg/m3, the mass concentration of the same amount was 1.64% CaCO3 solution as absorption liquid and absorbent pH value at 5.2, the average desulfurization efficiency of the pneumatic devised stirred absorber is up to 96%, while the average desulfurization efficiency of lower than jet-tubing absorber is only about 80%. Under the same experimental conditions, when absorbent pH value decreased to 4.0, the average desulfurization efficiency of the pneumatic devised stirred absorber still can reach 77%, while the average desulfurization efficiency of lower than jet-tubing absorber is only about 53%.Considering features that low pH environment conducive to the enrichment of heavy metals, double loop VST absorber for treatment of high concentration of sulfur-containing flue gas desulfurization and recovering economic value slag was developed. The new double loop absorber includes two independent desulfurization cycle. The first cycle is the ring-gate-type gas distribution and desulfurization system, using weak alkaline mineral absorption liquid slurry such as phosphate slurry. The second cycle is the VST structure absorber using strong alkaline liquid absorbing means to maintain a high desulfurization efficiency such as Na2CO3 solution. After desulfurization in the first cycle, impurities in the phosphate slurry are removed to make phosphate enrichment and the desulfurization slag can be directly added to the concentrated sulfuric acid is made after SSP (phosphate) for local sales. The second cycle of VST structure would to ensure a high desulfurization efficiency. For example, when the intake flow flue is 2300 m3/h, sulfur concentration 3400mg/m3, VST buried 220mm, the total absorption tower desulfurization efficiency may be up to 95%. Research shows that the buried depth of VST have a greater impact on desulfurization absorber efficiency. In order to gain a the total desulfurization efficiency of 78%, VST must buried at a depth of 80mm maximum or least when other things being equal to the above.In this paper, new equipments and technologies of flue gas desulfurization based on the pulse bubbling and aerodynamic stirring was systematically researched, including gas desulfurization absorber device, stirring apparatus and absorber applications performance optimization studies. The results shows that while simplifying the structure of the absorber, new equipment and technologies reduce the pressure loss, improve aspects of the absorber bubbling effect and ensure a higher desulfurization efficient. The research also has done a lot of minerals experiments to determine the optimum operating range in the application of the double loop absorption desulfurization while recovering economic value minerals. These studies provide the possibility of practical and theoretical basis for the large-scale industrialization with independent intellectual property rights of the absorber.