Study On Magnetically Stabilized Fluidized Bed Used In Biodesulphurization System

Microorganism desulphurization technology is important for the society, enviroment and economy due to its such advantages as easy process, low cost, less consumption, needless of high temperature, pressure and catalyzer, and no repollution in the treatment of sulphur-containing pollution. The sulphate waste water biodesulphurization technique and sulphide waste water biodesulphurization technique were designed out based on the metabolic mechamism of sulphate reducing bacteria (SRB) and colorless sulpher bacteria (CSB). The sulphate waste water biodesulphurization system was mainly consisted of anaerobic magnetically stabilized fluidized bed (anMSFB) filled with immobilized SRB biofilm and sulphide waste water biodesulphurization system was mainly consisted of aerobic magnetically stabilized fluidized bed (aMSFB) filled with immobilized CSB biofilm. In order to fullfill the system desulphurization operation with high efficiency, the intensive study was made on the following parts.(1) The key of the successful MSFB operation was to synthesize a type of porous carrier suitable for the microorganism immobilization with high magnetic susceptibility, so the composition of the magnetic porous beads was the basis of the system operation. Magnetic porous polystyrene beads (MPB) were obtained by suspension of copolymerization of styrene (STY) and divinylbenzene (DVB) in the presence of fine iron particles with Cellulose CM-Sodium (CMC) combined with gelatin as suspension stabilizers. The scanning electron microscopy was employed to investigate MPB morphology. MPB with narrow pore size distribution was characterized with high spherity and porsity(67.6%), strong adsorption, low density(1050 kg/m3), high specific surface area (11400m2/m3)and porous degree, dense pores on rough surface and even particle diameter(460μm). The average pore size was within the range of bacteria diameter. Acid anhydride groups were found on the surface and in the pores of MPB and the content of it could reach 18mmol/g, so it had better hydrophility and biocompatibility to make the large collection of biomass. According to the previous statement, it was known that MPB was good carriers for the immobilization of enzyme and microorganism. MPB was also suitable as particles filled in MSFB for its strong magnetic responding capacity, where the MPB sedimentation rate was high to 2.9 cm/min when magnetite existed.(2) MSFB was selected as bioreactor for the treatment of sulphate waste water and sulphide waste water because it could not noly solve the low reaction efficiency difficulty of anaerobic bioreactor but also solve the washout of particles under high flow rate through the magnetic stabilization. The fluidization behaviour of MSFB was observed under various magnetic intensity to find out the effect of influent flow rate on the bed voidage and pressure drop. The optimal operation parameters were determined that the applied electric current should be 5A and the minimum fluidization velocity be 55 ml/min.(3) It was significant to study the operation performance of the biodesulphurization system. The acclimated SRB group and CSB group were put in anMSFB and aMSFB filled with MPB. The start-up of the system was operated using immersing–carriers- to- form-biofilm method. Then, the simulated waste water was flowed in to enter the stabilized loading operation. The optical microscopy and the scanning electron microscopy were used to investigate the biomass and biofilm formation in anMSFB and aMSFB. The effect of temperature and pH on the removal efficiency of SO42- and S2- were studied, and the SO42- degradation kinetics equation of anMSFB and S2- degradation kinetics equation were determined. The bed height of MPB in anMSFB and aMSFB was deduced out theoretically according to the certain influent waste water concentration and desulphurization efficiency. The study has laid a foundation for MSFB with immobilized microorganism applied in the treatment of sulphur-containing waste water.