US 5,380,402 A · Reducing pulp mill liquid discharge

Abstract

A pulp mill has zero or minimum liquid discharges. The large amounts of liquid that must be processed to achieve this result are handled utilizing a multiple effect evaporator provided with heat from a steam exhaust of a condensing type steam turbine. Super heated steam from the recovery and bark boilers is fed to the turbine to generate electricity for the production of bleaching chemical and other uses in the mill. Three or four steam exhausts having different composite temperature and pressure values are taken from the turbine and used where most suitable in the pulp mill. For evaporation of bleach plant effluent the steam taken from the turbine preferably has a pressure of about 1-3 psia and a temperature of about 120.degree.-140 .degree. F, and has no significant adverse affect on power generation.

Claims22

Dependent claims

A method of facilitating operation a cellulose pulp mill, having a bleach plant, and a black liquor system so as to allow minimum discharge of pollutants therefrom, utilizing a condensing type steam turbine with at least one exhaust, comprising the steps of:

(a) producing super heated steam by burning organic containing waste products from the pulp mill;
(b) feeding the super heated steam to the condensing type steam turbine to generate a maximum amount of electricity from a given amount, temperature, and pressure of steam;
(c) exhausting steam from the at least one exhaust of the steam turbine;
(d) collecting liquid wastes from the cellulose pulp mill, including substantially all liquid effluents from the bleach plant;
(e) evaporating substantially all the collected liquid wastes independent of the black liquor system using the exhausted steam from the at least one steam turbine as heating fluid for effecting evaporation to produce clean condensate and a concentrated liquid waste;
and wherein the liquid polluting effluents is minimized.

3 more elements

A method of minimizing effluents from a cellulose pulp mill having a digester, bleach plant, condensing type steam turbine, a black liquor system containing a recovery boiler and chemical recovery loop, comprising the steps of:

(a) producing super heated steam by burning organics containing waste products from the pulp mill;
(b) feeding the super heated steam to the condensing type steam turbine to generate electricity;
(c) exhausting steam from the at least one exhaust of the steam turbine;
(d) evaporating substantially all liquid effluents from the bleach plant independent of the black liquor system to a concentration level high enough for incineration, by using the exhausted steam from the at least one turbine as heating fluid to produce a concentrated effluent;
(e) incinerating the concentrated effluent independent of the black liquor system to produce a residue containing sodium, sulfate and carbonate;
(f) leaching the residue to produce a leachate;
and
(g) feeding at least a substantial portion of the leachate to the chemical recovery loop associated with the recovery boiler.

5 more elements

Dependencies are inferred from the claim text.

Reducing pulp mill liquid discharge

Life of this patent

Reducing pulp mill liquid discharge

Life of this patent

Abstract

Claims22