Double-membrane-method technology for refining brine and equipment for the same

The invention relates to double-membrane-method technology for refining brine and equipment for the same. After pretreatment, brine to be treated enters a filtration procedure to form high-concentration nitrate-containing water and refined brine; pretreatment refers to carrying out a removal procedure of calcium and magnesium ions, a removal procedure of ammonium, a reduction procedure and a pH adjusting procedure to the brine to be treated; the filtration procedure refers to the steps that: the pretreated brine is pumped to gas-stripping tubular type membrane module for ultrafiltration, thereby organic impurities, suspended matters and partial precipitates of the brine are intercepted; pressure raising is carried out to the brine which permeates a tubular type membrane, then the brine directly enters nanofiltration membrane module for nanofiltration; the brine which can not permeate the tubular type membrane returns the removal procedure of calcium and magnesium ions; and in a high pressure state, sulfate ions are intercepted by a nanofiltration membrane to form high-concentration nitrate-containing water, and chloride ions and sodium ions permeate smoothly the nanofiltration membrane to form refined brine. The technology in the invention is simple, low energy consumption, small land-occupation area, low investment and low production cost, a stable operation system, strong impact-resistance load capability and no secondary pollution.