Silica Scale Prevention for Advanced Energy Utilization of Geothermal Brine

我们提出了一种利用硅胶来去除地热卤水中二氧化硅的方法，并将其应用于防止换热表面的二氧化硅结垢。(1)利用模型地热卤水，实验考察了种子颗粒直径、初始比表面积和初始孔径对去除二氧化硅的影响。颗粒直径对最终沉淀二氧化硅的数量和最终比表面积几乎没有影响。单位表面积上的二氧化硅沉淀量随着初始孔径的增大而增加，二氧化硅的沉淀率系数随着颗粒直径的减小和初始孔径的增大而增大。(2)考察了pH值和一些操作条件对二氧化硅去除效果的影响。当初始SiO_2浓度为0.5 kg·SiO_2·m~(-3)时，在初始pH为5~9的范围内，随着初始pH的增加，SiO_2的去除速率增大。在初始pH相同的情况下，随着温度的升高和初始二氧化硅浓度的降低，二氧化硅的去除率增加。在初始二氧化硅浓度较低的情况下，二氧化硅的去除效率不受预播时间的影响，而在初始二氧化硅浓度较高的情况下，随着预播时间的减少，二氧化硅的去除效率会增加。(3)采用基于实际地热卤水中溶解盐组分的模型地热卤水，考察了溶解盐类对硅胶播种方法去除二氧化硅性能的影响。钾、钠离子通过盐析作用提高了二氧化硅的过饱和度，从而促进了二氧化硅的去除。除盐析作用外，钙离子和铁离子还通过生成硅酸盐来促进二氧化硅的去除。硼酸对二氧化硅去除效果影响不大。

We have proposed a seeding method using silica gel to remove silica from geothermal brines and applied to prevent silica scale on the heat exchanging surfaces.(1)The effects of the seed particle diameter, initial specific surface area and initial pore diameter on silica removal are experimentally examined using a model geothermal brine. The effects of the particle diameter on the quantity of the final precipitated silica and on the final specific surface area are hardly seen. The quantity of precipitated silica per unit surface area increases with increasing initial pore diameter, and the silica precipitation rate coefficient increases with decreasing particle diameter and with increasing initial pore diameter.(2)The effects of pH and some operational conditions on the silica removal performance are investigated. When the initial silica concentration is 0.5 kg-SiO2-m^<-3>, the silica removal ratio increases with increasing initial pH in the range of 5-9. When the initial pH is the same, the silica removal ratio increases with increasing temperature and with decreasing initial silica concentration. While the silica removal ratio is not affected by the pre-seeding time in the case of lower initial silica concentrations, it increases with decreasing pre-seeding time in the case of higher initial silica concentrations.(3)Model geothermal brines based on a component of dissolved salts in the actual geothermal brines were used, and the effect of dissolved salts on the silica removal performance by a seeding method using silica gel is examined. Potassium and sodium ions increase the silica supersaturation degree by their salt-out effects, and as a result promote silica removal. Calcium and ferric ions promote silica removal by production of their silicates in addition to the salt-out effect. Boric acid has little effect on silica removal.