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The LLL field brine-scaling test system and a variety of measurement techniques have been used to test a group of eight proprietary additives from eight different companies, a hydroxyethylcellulose previously found to retard silica precipitation, and geothermal sludge as a seeding agent to reduce scaling. For each additive, scaling rates at both 210 and 125/sup 0/C and on three different materials--mild steel, Teflon, and Hastelloy C-276--were measured using test coupons. Sections of steel pipe and perforated screens also were exposed to the treated brine, silica precipitation rates in the effluent brine were measured by means of the electrochemical linear polarization resistance technique. Examination of the pipe sections and chemical analyses of the scales are not complete, thus only preliminary conclusions are reported here. It appears that, although none of the additives effected a dramatic reduction in scaling rates, several decreased the rate of scaling of mild steel at 125/sup 0/C by a factor of 2 to 3. Only hydroxyethylcellulose retards the rate of precipitation of silica in the effluent brine. Scaling rates could not be measured accurately in the seeding experiment because of its short duration, but this brine treatment had the desired effect, at 125/sup 0/C, of reducing themore » level of dissolved silica and hence the scaling tendency of the brine. Further experiments of this type will be conducted.« less |
