Geothermal power plant scale separation method and apparatus

In a geothermal electrical power generating plant of the type employing flash crystallizer means and reactor clarifier means for processing a large quantity of particulate silica that precipitates out of a geothermal brine stream as thermal energy is extracted from it during power production, apparatus for separating scale particles which have broken loose into the brine stream from the silica particles, which comprises:

• elongated tubular decanter means having its tubular axis generally vertically oriented, and having upper and lower end portions;
• substantially closed scale collector vessel means located generally below said decanter means and operatively connected to said lower end portion of said decanter means for fluid communication with said decanter means, said collector vessel means having a scale collection location in the bottom thereof;
• first fluid conduit means from underflow means of said clarifier means to said decanter means for generally continuously diverting a portion of the underflow from said underflow means, said underflow portion having particulate solids suspended therein consisting primarily of silica seed particles and also including scale particles;
• a source of dilution liquid in said plant, and second fluid conduit means from such source to said decanter means for generally continuously diluting said underflow portion to provide a liquid slurry medium in said decanter means which has a sufficiently low viscosity to enable generally free settling movement of said silica and scale particles;
• and
• slurry removal port means in said upper end portion of said decanter means for generally continuous removal of said liquid slurry medium from said decanter means, which establishes a continuous upward flow of said liquid slurry medium in said decanter means that has an upward velocity that is substantially greater than the terminal settling velocity of said silica particles but substantially less than the terminal settling velocity of said scale particles, whereby most of said silica particles will rise upwardly in said decanter means and out through said slurry removal port means, and most of said scale particles will settle downwardly in said decanter means into said scale collector vessel means and downwardly therein to said scale collection location.