A. Ahlstrom Corporation

Kamyr, Inc.

Ahlstrom Machinery, Inc.

Jarmo Soderman

Joseph R Phillips

Rolf C Ryham

Brian F Greenwood

Johan E Gullichsen

Jan T Richardsen

Erkki J Kiiskila

Esko I Mattelmaki

Tuomo S Nykanen

Karl G Wiklund

Karl Wiklund

Effluents are minimized from a cellulose pulp mill having a recovery boiler by concentrating liquid effluents from the bleach plant and/or liquid spills from process streams, incinerating the concentrated effluents in the recovery boiler, removing particles present in the flue gases from the recovery boiler to produce an ash including salts containing potassium and chloride, and sulfur compounds, and removing the potassium and chloride from the ash while returning the sulfur containing compounds to the recovery loop, so as to balance the sulfur, chloride and potassium levels in the mill. The sulfur is typically returned directly to a stream of black liquor just before entry into the recovery boiler. Green liquor is produced from the melt, which preferably is treated to remove metals from it prior to caustization (e.g. by sedimentation and/or filtration), and prior to green liquor crystallization to produce sodium hydroxide.

Minimal effluents discharge pulp mill with chemical recovery

Apparatus for a pulp and paper mill, and methods of acting on liquid effluents produced in the mill, which minimizes the discharge of polluting gaseous and liquid effluents to the environment. Liquid effluents from the bleach plant are concentrated (e.g. evaporated), incinerated (e.g. gasified), leached, crystallized (e.g. freeze crystallized) then washed, and then fed to the plant chemical recovery loop. White liquor produced from the recovery boiler melt is fully oxidized and used in place of caustic in the bleach plant. Essentially all sulfuric acid, sulfur dioxide, caustic, and chlorine dioxide necessary for the pulp mill is produced from mill liquid effluents and gas waste streams, on site at the pulp mill. Typical bleaching sequences that can be used are DE.sub.op D.sub.n D, or AZE.sub.o PZP.

Apparatus for minimizing effluent discharges and recovering chemicals in

In minimizing effluents from a cellulose pulp mill, liquid effluents from a bleach plant are concentrated, and then incinerated to produce a residue including sodium, sulfate, and sodium chloride. This residue is distilled with sulfuric acid to produce gaseous hydrogen chloride and remaining residue, the HCl being used in chloride dioxide production for the bleach plant, while the remaining residue is passed to the recovery loop (e.g. recovery boiler). Sulfur containing gases from the non-condensible gas system may be combusted to produce gaseous sulfur dioxide, which is then converted to sulfuric acid, to distill the residue. Where a non-chlorine bleach plant is provided, the liquid effluents may be concentrated in evaporators and then passed directly to the recovery boiler. The liquid streams in the mill are managed by a cascade principle to reserve the cleanest water for only those processes where it is needed while minimizing its use where it is not necessary.

Zero discharge mill distillation, salt recovery, and water management

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.

Reducing pulp mill liquid discharge

Method for minimizing pulp mill effluents

Growing community of inventors

Helsinki, Finland

Jarmo Soderman