稠油污水混凝除硅效果及作用机理探讨

发布时间：2018-08-03 13:19

【摘要】：稠油污水成分复杂且又有回用热采锅炉的高水质需求,因此处理难度很高,其中硅含量的去除更是一个难点。稠油热力开采过程中,高温蒸汽及冷凝液会与地层岩石反应,脱除其中的硅并带入到采出液中,最终进入稠油污水。国标中要求处理后稠油污水回用锅炉前其中硅含量应低于50mg/L,这样才能保证锅炉长期运行下不产生硅垢。化学混凝除硅是稠油污水除硅的主要方法,很多金属氧化物或氢氧化物都有良好的除硅效果,但它们的具体除硅机制却并不明朗,一方面是因为水中的硅酸有多种形态,另一方面则是因为这些除硅药剂在水中的水解成分也较为复杂。本文介绍了稠油含硅污水中硅的来源、混凝处理技术及相关理论的研究进展。以辽河稠油污水和实验室模拟污水为主要研究对象,结合前人的研究成果建立起污水中各形态硅酸的分析方法,包括单硅酸(Sia)、低聚硅酸(Sib)、高聚硅酸(Sic)和不溶硅酸等,考察了水中的硅酸在温度、pH和盐等影响下的形态变化与转化规律。应用多种钙类、镁类及铝类等混凝剂,研究其加量和成分等对不同硅酸形态去除效果的影响,分析各类除硅剂的有效作用成分,总结了混凝除硅过程中的主要作用机理。实验结果表明:温度较高时有利于污水中的Sic向Sia变化,且温度越高平衡后Sia含量越高;酸性条件会抑制Sia的形成,而碱性条件下则会促进其它形态的可溶硅酸向单硅酸转化;Mg2+、Al3+、Fe3+等阳离子能显著影响溶液中可溶硅酸的含量,主要是以沉降去除为主,其中Al3+表现最好,Ca2+则有一定的抑制Sia聚合的作用,而Cl-、HCO3-、NO3-、SO42-等离子则无明显作用。由于污水中高含HCO3-,钙类除硅剂的效果不如镁类,而同等条件下强碱复合MgCl2效果最好,在pH=12时,800mg/L加量下,除硅率达到91.89%,反应后总硅含量降低到38.4mg/L;其次是MgO颗粒,最差是Mg(OH)2颗粒,对MgO的粒径考察发现粒径越小除硅效果越好,但分析除硅过程中的硅酸形态表明,钙类和镁类除硅剂主要直接去除的是水中的Sia,它们很可能是通过在水中形成的表面水化层对单硅酸的吸附来达到除硅作用;Al2(SO4)3在加量为6mmol/L时能将稠油污水中的总硅降低到50mg/L以下,聚合氯化铝(市售)在加量为4mmol/L时即可达到同等效果;pH值会影响硫酸铝的水解形态,pH=5时Al2(SO4)3表现出最优的除硅效果,其中对Sic的去除效果要优于Sia;新制备的Al(OH)3对污水中Sia的去除效果优于对Sic;对比实验室制备的不同铝形态分布的PAC10、PAC22及PAC25的除硅效果可见,单核铝(Ala)含量高的PAC10对含硅污水处理后,污水中残余的Sic更少,胶溶铝(Alc)含量高的PAC25处理后污水中残余的Sia更少,即Ala对Sic、Alc对Sia分别有针对性的去除效果;吸附-改性理论可以解释硅铝之间的相互作用,在硅铝高聚物的氧化物或氢氧化物表面形成的硅铝酸盐位或固溶体覆盖层降低了原物质的溶解度,从而导致其更容易在污水混凝过程中沉降去除。
[Abstract]:Heavy oil sewage is complex and has high water quality demand for reusing heat recovery boiler. Therefore, it is difficult to treat the silicon content. In the process of heavy oil thermal recovery, the high temperature steam and condensate will react with the formation rock, remove the silicon and lead into the extraction liquid, and eventually enter the heavy oil sewage. The national standard is required. The silicon content of the treated heavy oil sewage boiler should be lower than 50mg/L, so as to ensure that the boiler does not produce silicon scale in the long run. Chemical coagulation removal of silicon is the main method of heavy oil sewage removal of silicon. Many metal oxides and hydroxides have good silicon removal effect, but their specific silicon removal mechanism is not clear, on the one hand Because of the various forms of silicic acid in water, on the other hand, the hydrolysis components of these chemicals in water are also more complex. This paper introduces the source of silicon in heavy oil and silicon polluted water, the technology of coagulation treatment and the research progress of related theories. The analytical methods of silicic acid in various forms of sewage were established, including monosilic acid (Sia), oligosilicate acid (Sib), high Polysilic acid (Sic) and insoluble silicic acid. The morphological changes and transformation laws of silicic acid in water were investigated under the influence of temperature, pH and salt. The additives, such as calcium, magnesium and aluminum, were used to study the amount and composition of the acid. The effect of different silicic acid on the removal efficiency of silicon removal agent is analyzed. The main mechanism of action in the process of coagulation removal is summarized. The experimental results show that when the temperature is high, the Sic changes to the Sia in the sewage, and the higher the temperature is, the higher the Sia content is, the acidic condition will inhibit the formation of Sia and the alkaline condition. Mg2+, Al3+, Fe3+ and other cations can significantly affect the content of soluble silicic acid in the solution, mainly by settlement removal, of which Al3+ is the best, Ca2+ has a certain effect on the inhibition of Sia polymerization, while Cl-, HCO3-, NO3-, SO42- plasma has no obvious effect. The effect of HCO3-, calcium desilication agent is not as good as that of magnesium, and the effect of strong alkali compound MgCl2 is the best under the same condition. Under 800mg/L addition, the removal of silicon content is 91.89%, the total silicon content is reduced to 38.4mg/L after the reaction; the second is MgO particles, the worst is Mg (OH) 2 particles, and the smaller the particle diameter of MgO is, the better the silicon removal efficiency is, but the analysis of silicon removal is analyzed. The form of silicic acid in the process indicates that calcium and magnesium desilication agents mainly remove Sia in water. They are likely to be desilicate by adsorption of monosilicate by the surface hydration layer formed in water. Al2 (SO4) 3 can reduce the total silicon in thick oil to below 50mg/L when adding amount of 6mmol/L and polymerized aluminum chloride (market). The same effect can be achieved when adding the amount of 4mmol/L; the pH value will affect the hydrolysis of aluminum sulfate, and Al2 (SO4) 3 shows the best effect on the removal of silicon at pH=5, and the removal effect of Sic is better than that of Sia; the new Al (OH) 3 is superior to Sic in the removal of Sia in the sewage. The desilication effect of C25 shows that the PAC10 with high Ala content has less residual Sic in the wastewater after the treatment of silicon containing sewage, and the residual Sia in sewage is less in the wastewater after PAC25 treatment with high Alc content, that is, Ala pairs Sic, Alc to Sia respectively, and adsorption modification theory can explain the interaction between silicon and aluminum, in silicon The aluminate or solid solution covering layer formed on the oxide or hydroxide surface of the aluminum polymer reduces the solubility of the raw material, which makes it easier to settle down in the process of sewage coagulation.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X741

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