Method and device for treating oil sludge and oil-containing waste water

  • US 5,059,332 A
  • Filed: 10/03/1990
  • Issued: 10/22/1991
  • Est. Priority Date: 04/09/1990
  • Status: Expired due to Fees
First Claim
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1. A method of treating an oil sludge and an oil-containing waste water, comprising the steps of heating a mixture of said oil sludge and said oil-containing waste water to give a fluidity thereto;

  • feeding said mixture to a flashing vessel having an inner pressure maintained less than atmospheric pressure to vaporize off a part of the water and a light oil and to obtain a sludge containing an oil-containing dust, a heavy oil component and residual water;

    cooling a vapor of said part of water and said light oil to condense said vapor and separate said part of water from said light oil and recovering said part of water and said light oil;

    separating said sludge into said oil-containing dust and a primary oil-containing water comprised of said heavy oil component and said residual water by means of a first centrifugal separator;

    separating said primary oil-containing water into said heavy oil component and said residual water as a secondary oil-containing water by means of a second centrifugal separator and recovering said heavy oil component;

    washing said oil-containing dust separated by said first centrifugal separator with a washing liquid to elute oil attached to said oil-containing dust into said washing water and thereby obtain an oil-free dust and an emulsion;

    separating said oil-free dust from said emulsion by means of a third centrifugal separator;

    washing said oil-free dust with an acidic water, then washing said oil-free dust with an alkaline water, and finally washing said oil-free dust with a neutral water to obtain a waste washing water containing said oil-free dust;

    separating said dust from said waste washing water by means of a fourth centrifugal separator to recover said dust;

    adding a pH adjusting liquid to a mixture of said secondary oil-containing water, said emulsion and said waste washing water to adjust a pH value of said mixture;

    electrolyzing said mixture after adjustment of the pH value in an electrolytic cell to separate the same into a scum containing said emulsion generated at an upper portion of said electrolytic cell, a sedimented substance containing a metal hydroxide collected at a lower portion of said electrolytic cell, and a residual liquid generated at an intermediate portion of said electrolytic cell;

    returning said scum to said second centrifugal separator to treat the same;

    recovering said metal hydroxide; and

    discharging said residual liquid.

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