Research On Preparation Of Magnesium Hydrate Through Lime Method Wtth Concentrated Saltwater From Seawater Desalination

The concentrated saltwater is a byproduct of desalination, its composition is similar to seawater but at a higher concentration than seawater about a time, and in the preprocesses for sea water desalination must to filter and to add additives such as inhibitors, so that concentrated saltwater also contains some additives composition, this characteristic decided that if let it out, it will not only be a destructive on the Marine ecological environment, but also is a waste of sea water.The existing production process is making this concentrated brine into the saline salt, its advantages can be substantially reduced salt required saline area, shorten the time needed to produce the salt, the cost of making salt. But, on the other hand, because of the large amount of brine disposal, it is out of the saline salt processing capability, and due to the ban on the direct discharge of concentrated brine, brine handling problems with the scale of the rapid increase of desalination of sea water is increasingly outstanding, this problem already became restrict the obstacle of the development of seawater desalination industry.Exploration of the new comprehensive utilization of brine is undoubtedly the most sensible choice, this task is make exploration to achieve this goal, taking into account if the magnesium extracted out of the concentrated brine system first,the remaining will become simple, and make a basis for subsequent utilization, this thesis mainly studies on how to extract magnesium salt and how to improve the purity of magnesium salt.Experimental raw materials from Beijiang Power Station, taking into account the industrialized production to processing large quantities of concentrated salt solution, from the economic point of view, select the lime as precipitating agent to experimental study.The experiment study on the process conditions of preparation of magnesium hydrate through lime method, using the concentrated saltwater obtained from Seawater Desalination as raw material. According to the single factor and orthogonal tests, the effects of reaction aging time, molar ratio of calcium hydroxide and magnesium ions, the flow rate of calcium hydroxide and agitation rate on the purity of magnesium hydrate and calcium content in the production are investigated to optimize the reaction conditions. The results show that the order of the factors is molar ratio of calcium hydroxide and magnesium ions, the flow rate of calcium hydroxide and the reaction aging time follow. The optimal react conditions are: molar ratio of calcium hydroxide and magnesium ions is0.9, the flow rate of calcium hydroxide is10×10-3mol·min-1, and the reaction aging time is120minutes.On the basis of the purity of magnesium hydroxide experiments, to improve the particle size of magnesium hydroxide were studied, through the single factor experiment and the orthogonal experiment, the effects of reaction aging time, feeding rate of the calcium hydroxide, concentration of calcium hydroxide, concentration of magnesium ions in concentrated saltwater. The results show that the order of the factors is feeding rate of the calcium hydroxide, and concentration of calcium hydroxide, time of reaction and aging flowed. The optimal react conditions are:the flow rate of calcium hydroxide is5×10-3mol·min-1, concentration of calcium hydroxide is2.4mol·Kg-1and the reaction aging time is60minutes.