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Study on the Synthesis and Performance of Special Inhibitor in LT-MED Seawater Desalination

Author: ZhangHaiChun
Tutor: WangHaiZeng；RuanGuoLing
School: Ocean University of China
Course: Marine Chemistry
Keywords: Low-temperature multi-effect distillation Scale Desalination Calcium carbonate Complex
CLC: TQ085.4
Type: Master's thesis
Year: 2008
Downloads: 103
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Abstract

Scaling are the troubled the thermal desalination device running one of the main problems. Multi-effect distillation desalination device in large cryogenic running at home and abroad, adding scale inhibitor commonly used method to prevent the fouling of heat exchanger surfaces. The scale inhibitor be applied in thermal desalination are phosphate and polymers two categories. The main application of the phosphates in the cryogenic distillation apparatus below 90 ℃ and the application is not widespread, organic polymers, especially the polycarboxylic acids because of its good inhibition effects and thermal stability, in a thermal desalination widely Application Potassium persulfate as the initiator, in an aqueous system, synthesis of acrylic acid, maleic anhydride, and 2 - acrylamido-2 - methylpropane sulfonic acid (AMPS) monomer terpolymer antiscalant PAMA orthogonal experimental results show that the optimum synthesis conditions (AA): n (AMPS) = 2: 1, potassium persulfate monomer weight ratio is 15%, isopropanol and the total monomer mass ratio of 3% The reaction time is 4H, N (MA): n (AMPS) = 6: 1, the reaction temperature was 90 ° C. The IR spectrum showed characteristic absorption peak of carboxylic acid salts, sulfonic acid group-containing synthetic polymers, the CN absorption peaks. Viscosity Determination of the molecular weight of the synthetic polymer in the best conditions for the 4511. Thermogravimetric analysis results show that the polymer begins to decompose at 372.5 ℃. ? Using the national standard GB/T16632-1996 preliminary study PAMA polymer scale inhibitor for calcium carbonate scale inhibition effect the PAMA amount of calcium ion concentration, alkalinity and temperature scale inhibition rate greater. As PAMA dosage increase, inhibition rate showed a tendency to increase. Alkalinity increases with the concentration of calcium ions, and the temperature increases, inhibition rate showed a downward trend. Constant time scale inhibition rate. Experimental results show that the seawater concentration method, the as PAMA dosage increase, inhibition rate also showed a tendency to increase. Temperature, holding time scale inhibition rate of concentration is smaller. As the temperature increases, the time, the concentration factor increased, inhibition rate showed a decreasing trend. Dispersing iron oxide experiment, the as the PAMA amount increases, a transmittance decreased, the dispersing ability becomes strong. As the the Fe2 concentration increases, through the first decreases increases. As the temperature increases, the transmittance was a tendency to increase. For polymer antiscalant PAMA, using the inhibition effects of the two methods is satisfactory, it is a good antiscalant. GB method deficiencies as an evaluation method, evaluation methods need to be further improved. As a single component scale inhibitor, PAMA has better scale effect, but compared to commercialization the antiscalant there is a certain distance, the need for complex research, to increase its scale inhibition performance, so as to realize the commercialization production. The scale inhibitor PAMA prepared with foreign antiscalant BelgardEV2035, BelgardEV2050 complex investigated the complex effects and economic. The PAMA with BelgardEV2035 BelgardEV2050 mixed synergies. Comparative analysis of the angle from the molecular weight of the complex results shows that the molecular weight is one of the important factors affecting the inhibition effects, there is a synergistic effect of two different molecular size scale inhibitor compound; comparative analysis of the results of the complex from the point of view of the functional groups seen, phosphono the introduction of the ability to improve the resistance of calcium carbonate, a carboxyl group, a phosphono group, and a sulfonic acid group, compounding definite synergistic effect exists. However, the introduction of the phosphonomethyl will bring about environmental problems, is an important direction in the the antiscalant synthesis in the future to reduce antiscalant molecule proportion or find alternative similar functions, non-phosphorus group substituted phosphono. Compound antiscalant economy showed that and compounded synthetic scale inhibitor effect while also significantly reducing the single use antiscalant BelgardEV2035, BelgardEV2050 the cost. Preparation of the blank and added antiscalant scale sample by means of scanning electron microscopy, and conducted a preliminary exploration of inhibition mechanism. The scanning electron microscopy analysis showed that, PAMA and its mixture with calcium carbonate scale inhibition mechanism is lattice distortion. The mechanism may be through the geometric matching theory, the surface can be explained by the theory and the molecular weight, the functional groups. PAMA and BelgardEV2050 complex scale inhibitor not only the crystal distortion, but also the crystal type change its scale inhibition mechanism remains to be further explored. Radical polymerization using the method of synthesis of terpolymer antiscalant PAMA, preferably hindered calcium carbonate ability and better dispersion of iron oxide and also showed a good synergistic effect and economic, Global antiscalant complex with , is a new and efficient non-phosphorus scale inhibitor. In this study, for PAMA in the low-temperature multi-effect distillation desalination provides an experimental basis, to further improve the synthesis conditions on the basis of the evaluation method and complex technology, is expected in the low-temperature multi-effect distillation desalination applications.

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