Thermal Power Plant Sub-critical Pressure Boiler Water In Addition To Silicon

The silica in water presents harmful effects on many industry process. The feed-water of critical and hypercritical presser boiler in fuel electric plant have a strict demand for the Si content. The content asked approached or reached the super-clean water data. So it is one of the very important tasks for the water treatment in fuel electric plants to remove the silica.Coagulation is one of the usual and basic methods. This method is the most suitable one for silica deprivation pre-treatment of boiler water in fuel electric plant. Reservoir water and ground water the research concerned are the raw waters of low turbidity degree which are very difficult to be treated due to its lower silica contents in seston ,organic matter and colloid. Reinforced coagulation must be adopted for a better silica deprivation effect.According to the high hardness and basicity characteristics of ground water, silica deprivation research of ground water has been carried out focus on the softening coagulation method. The effect of Ca(OH)₂,Na₂CO₃ and PFS addition amounts on the silica deprivation rate has been studied. Good results have been obtained, the deprivation rate of total silica content in ground water exceeds 90% , the deprivation rate of colloid silica approximately reaches 90%. The study results show that with the increase of addition amount of Ca(OH)₂ ,the deprivation rates of total silica and colloid silica decrease, and the influence degree of the Ca(OH)₂ addition amount on silica deprivation rate is quite low when the amount reaches one certain value; as the PFS addition amount increases, the total silica content and colloid silica content gradually decrease, and decrease rate gradually falls down; the best deprivation result can be achieved by the two steps method: first, softening and deposition of the ground water be carried out by Ca(OH)₂ addition, then coagulation proceeds.The silica deprivation investigation of ground water and reservoir water by using PFS and PAC, PFS and organic macromolecular flocculating agent—PAM respectively have been conducted. The results show that the silica deprivation efficiency is lower when PFS or PAC alone be added, the deprivation rates of colloid silica in reservoir water and ground water by PFA coagulation treatment are below 80% and 70%respectively. The rate can reach a rather high value (87.5%and83.1% respectively) by the addition of PAM at the same time. The deprivation rate of colloid silica reaches 86.5%and 80.7% respectively under the same conditions.The interactivity of PAC and silica has been investigated after the production in laboratory of PAC and three kinds of silica (mainly consisted of Sia, Sib and Sic respectively). The influence of the three kinds of silica on the morphosis and coagulation property has been studied further. The results show that the interactivity of PAC and silica in the water solution kaolin clay is quite complicated, when the PAC interacts with silica, at the same time, the PAC itself undergos the processes of further hydrolyzation and morphosis change, the monomer silicic acid of silica is going to reach ionizing equilibrium and reach polymeric and solent equilibrium with polimerid. With the increases of Si and Sic contents in water solution, the range of PH value for suspended particle Off-stabilization becomes larger, the Eeta electric potential interval becomes smaller and the distance between the Off-stabilization intervals of high and low basification degree becomes longer, the active silicic acid moves the Off-stabilization interval of suspendedparticle toward the direction of lower pH value.Additionally, the experimental research has been carried out in laboratory focus on the coagulation desilication effect by adding addition agent into water before and. The results show that when the addition amount of electric power ash or kaolin clay is 20mg/L, the colloid silica deprivation rate of reservoir water is 90.4% or 86.6% respectively; when the addition amount of electric power ash or kaolin clay is 30mg/l_, the colloid silica deprivation...