PRECIPITATION OF COLLOID SILICA FROM HYDROTHERMAL SEPARATE BY COAGULANTS ADDITION ( KAMCHATKA , RUSSIA )
We have carried out the experiments on coagulation and precipitation of silica from the separate of Verkhne-Mutnovsky geothermal electric power plant (Mutnovskoe hydrothermal field). Silica precipitation from the water solution was conducted in two ways: by adding slaked lime CaO and by electrocoagulation treatment on aluminium electrodes. Silica precipitation with addition of slaked lime was carried out under laboratory conditions at the temperature of 20 and 96 °C. Сolloid and monomeric silica concentrations, solution pH, flakes sizes and physical-chemical properties of material precipitated with different quantities of added lime were determined. We also carried out series of experiments on solution treatment of mixed type: addition lime with freshly precipitated flakes, and addition lime with sea water. In the experiments on electric coagulation, current intensity and distance between electrodes were changed. Dependence of silica concentration on treatment duration was studied. Quantities of electric energy and anode aluminium consumed for reducing of silica concentration to a certain level were obtained. The results of our experiments can be used for developing of technological scheme of silica precipitation and utilization optimal for Verkhne-Mutnovsky geothermal electric power plant.
RESULTS OF THE ELECTROCHEMICAL TREATMENT OF HYDROTHERMAL SEPARATE AT THE MUTNOVSKOE HYDROTHERMAL FIELD ( KAMCHATKA , RUSSIA )
We have studied silica precipitation from the hydrothermal solution by electrochemical coagulation method in the laboratory and Mutnovskoe field conditions. Coagulant was added to the solution from the dissoluble metal electrodes (steel, copper, aluminium) under passing direct electric current. We found treatment with aluminium electrodes to be the most effective. In these experiments silica and aluminium concentration in solution, solution pH were determined and electrodes voltage was recorded. Settling rates of the coagulated silica flakes and the time of solution clarification were also measured. Current strength, solution temperature and distance between the electrodes plates were changed in experiments. The theoretical functions expressing the dependence of silica concentration in solution on treatment duration and the quantity of electric energy consumed during the treatment were found. The rate of aluminium electrodes dissolving and amount of coagulant used for treatment were calculated. With the help of X-Ray analysis it was obtained the amorphous structure of material precipitated by the electric treatment. On the base of the experimental data we evaluated the parameters of pilot electrocoagulator necessary for treatment of 1 kg/s of hydrothermal separate flow.
Modeling studies: The Dachny geothermal reservoir, Kamchatka, Russia
The spatial distribution of pre-exploitation conditions (i.e. temperature and pressure distribution, liquid and vapor saturations, circulation characteristics of high-temperature fluids) in the Dachny field of the Mutnovsky hydrothermal system, obtained using a three-dimensional (3-D) mapping method, are revised on the basis of natural-state simulations performed using the computer code TOUGH2. A 3-D model of the natural-state conditions at the Dachny site was developed. The fine-tuning of the model was achieved by comparing computer results to the observations made in geothermal wells tested during 1983–1988. Also studied was the behavior of the field in response to different exploitation scenarios, assuming production from existing and additional wells needed to supply sufficient steam to a proposed 80 MWe power plant.