| Reusing urban reclaimed water as circulating cooling water is one of the effective ways to solve the water resource shortage. However, the reclaimed water can not be used directly, it needs lime softening treatment.In this process,it will produce large amounts of calcium mud,which causes new environmental pollution. This study stands on the composition and pHase characteristics of calcium mud,using calcium mud to disposal SO2 is make two kinds of harmful substances to the environment interaction,realize "using waste treat waste"and the comprehensive utilization of resources. But,there is a new question which is difficult to dehydrate about desulfurization gypsum.In this paper,is to find out the reasons for this problem, and to provide a reference for the desulfurization of calcium. In this paper.the purpose is to find the reason of this qusiton and provide reference for calcium mud used for desulfurization.In this paper,makes experiments to study the effect of different impurities on the key processes of desulfurization:limestone dissolution, calcium sulfite oxidation and crystallization.Firstly,with the X-ray Diffraction (XRD), X-Ray Fluorescence(XRF),Grading Analyzer, Scanning Electron Microscopy (SEM),chemical and mineral compositioru particle size and other properties of reclaimed water softening calcium mud were analyzed. The results showed that the content of calcium oxide was 46.84%, lower than the general standard, and it has the small particle size and large surfase area, it contained a variety of impurities.The impact of impurities,such as MgO, Fe2O3, Polymeric ferric sulfate (PFS), polyacrylamide (PAM) on the dissolution of calcium mud was investigated by PH-stat method. At the temperatuie of 50℃, stirring speed 500r/min, the final pH of 5.5, the dissolution rate of calcium mud in the same time was slightly lower than that of the power plant, when dissolved in 60min, dissolution rate difference of about 6%. After adding impurities, it is found that the addition of iron and magnesium is beneficial to dissolution. The addition of PFS can have different effects, and the PAM can greatly reduce the dissolution rate, when it adds 0.5mg can reduce the dissolution rate by more than 10%.When the experiment conditions as followsrthe initial PH is 5.5,the temperature is 50℃, flow rate of oxidation air is 0.15 m3/h, stirring speed is 300 r/min,using the iodine volume method to experiment. The results show that MgO has a slight effect on the oxidation. Fe2O3 can cause the inhibition of the oxidation. The effect of PFS is different according to different addition. Smallest amount of PAM is significantly inhibited the oxidate process.At the same time, this paper was also studyed the impact of the particle size distribution when added the concentration of impurities contained in the calcium mud. The results showed that in the oxidation process, the slurry particle size distribution will be broadened with the addition of impurities, particle size becomes smaller.The influence of the presence of PFS, PAM and mixing impurities at different ratios on the gypsum crystallization process was explored which is similar to the conditions of WFGD. The results show that PAM and PFS on crystallization process has certain inhibition.When adding different impurities such as PAM、PFS or mixing impurities,the crystal trapezoid body gradually turns to needle shaped gypsum, the volume average particle size decreases and the specific surface area increases,which reduces the dehydration of gypsum. |
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