Kamyr, Inc.

Ahlstrom Machinery, Inc.

Andritz-ahlstrom Inc.

A. Ahlstrom Corporation

Jan T Richardsen

Rolf C Ryham

Joseph R Phillips

J Robert Prough

Bruno S Marcoccia

Richard O Laakso

R Fred Chasse

Tuomo S Nykanen

Brian F Greenwood

Johan E Gullichsen

Erkki J Kiiskila

Esko I Mattelmaki

Jarmo Soderman

Karl G Wiklund

Mark D Barrett

Victor L Bilodeau

Carl L Luhrmann

Karl Wiklund

Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Dissolved solids control in pulp production

Dissolved organic material control in a cellulose pulp continuous digester

Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it wit much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Dissolved organic materials control in cellulose pulp production

DOM control in cellulose pulp production

Low dissolved solids control in pulp production

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

Kraft pulp of increased strength (e.g. at least about 15% greater tear strength at a specified tensile for fully refined pulp, and as much as about 27%) is produced by keeping the dissolved organic material (DOM) concentration below about 100 g/l (e.g. &lt;50 g/l) throughout substantially the entire kraft cook. This may be done by extracting liquor containing a level of DOM substantial enough to adversely affect pulp strength, and replacing some or all of the extracted liquor with liquor containing a substantially lower effective DOM level than the extracted liquor, so as to positively affect pulp strength. The replacement liquor may be water, white liquor, pressure heat treated black liquor, washer filtrate, cold blow filtrate, or combinations, or the extracted liquor can be treated to remove or passivate the DOM (e.g. by precipitation, ultrafiltration, or absorption). The extraction and dilution provided is practiced at a number of different stages during kraft cooking, such as at three or more different levels in a continuous digester, or by continuously flowing low DOM concentration liquor through a batch digester.

Pulping with low dissolved solids for improved pulp strength

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

Method of managing liquid steams in a pulp mill

In the production of cellulose pulp (e.g. kraft pulp) utilizing a continuous digester having a number of different feed points for cooking (e.g. white) liquor and utilizing a high pressure feeder, the volume of cool white liquor that is applied to the feed system is reduced compared to conventional processing. This can cause excessive hammering, and damage the high pressure feeder and adjacent piping and equipment. In order to avoid this, liquid being recirculated from the top of the digester back to the high pressure feeder is cooled by passing it into a heat exchanger into heat exchange relationship with a cooler liquid, with the flow of coolant automatically controlled by sensing the temperature of the recirculated liquid. The temperature in the feed system can further be lowered by cooling the cooking liquor before it is added to the pulp slurry, as by passing it to a flash tank so that its temperature is reduced at least 10.degree. C., and the flashed steam can be used in an evaporator.

Top circulation line cooling for a modified cook digester

Growing community of inventors

Glens Falls, NY, United States of America

Jan T Richardsen