Ahlstromforetagen Svenska Ab

Andritz-ahlstrom Inc.

Kamyr, Inc.

Ahlstrom Machinery, Inc.

A. Ahlstrom Corporation

Other

Ahlstrom Recovery Inc.

Ahsltromforetagen Svenska Ab

Ahlstromforetagen Swenska

Andritz Inc.

Rolf C Ryham

Jan T Richardsen

Joseph R Phillips

Bruno S Marcoccia

R Fred Chasse

J Robert Prough

Richard O Laakso

Tuomo S Nykanen

Brian F Greenwood

Johan E Gullichsen

Erkki J Kiiskila

Esko I Mattelmaki

Jarmo Soderman

Karl G Wiklund

C Bertil Stromberg

Erwin D Funk

J Wayne Chamblee

Kaj Henricson

James W Smith

Jian E Jiang

Ella Sun Yu

Karl Wiklund

Jen T Richardsen

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

Steam (preferably clean steam) having less noncondensible gases than steam produced by conventional black liquor flashing is produced from hot black liquor from a digester of a pulp mill. A heat exchanger is utilized and the hot black liquor is passed through the heat exchanger in heat exchange contact with an evaporable liquid, preferably clean water. After the water is heated in the heat exchanger it is flashed in at least one flash tank where the heat exchanger is a liquid-to-liquid heat exchanger. The heat exchanger may alternatively include an evaporator (such as a falling film evaporator) in which case the black liquor is passed through an inductor before it enters the evaporator. Alternatively, the heat exchanger may be one or more boilers, such as kettle boilers, in which case the black liquor preferably passes through a cooler after the boilers. Heat energy and turpentine recovery are also maximized.

Heat recovery from spent digester cooking liquor

Dissolved organic material control in a cellulose pulp continuous digester

The EPA Cluster Rules for cellulose pulp mills are complied with by first collecting foul condensate including hazardous air pollutants (HAPs), such as methanol, at a temperature of between about 140-180&deg; F., and passing the foul condensate into direct contact with heated vapor at a plurality of series connected stations to gradually heat the foul condensate to a temperature desirable for steam stripping. Then the heated foul condensate is steam stripped to produce a high temperature (e.g. about 250-350&deg; F., preferably about 300&deg;) clean condensate. Then the high temperature clean condensate is flashed in a plurality of flash stations to produce a heated vapor in a lower temperature clean condensate, and the heated vapor is used to heat the foul condensate in each of the direct contact heat exchangers. Typically the highest temperature is used to heat the highest temperature foul condensate, with progressively lower temperature vapors used to heat progressively lower temperature condensate stations. A vapor is produced during steam stripping, and using low pressure steam the vapor is reboiled to produce a discharge containing the majority of HAPs, and the HAPs in the discharge are destroyed in a conventional thermal destruct unit or in another conventional manner.

Regenerative heat recovery for high temperature condensate stripping plants

Useable steam, e.g. substantially clean useable steam, is produced from a chemical cellulose pulping system hot spent treatment liquor (e.g. black liquor) with optimum energy efficiency by passing the spent liquor to a reboiler, and then pressurizing (e.g. with an eductor, fan, or compressor) the clean steam discharged from the reboiler. The clean steam can be used to steam incoming chips (e.g. in a chip bin) without significantly increasing the TRS load on the pulp mill NCG system.

Heat economy enhancements for the recovery and use of energy obtained from spent cooking liquors

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

A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps the pressure in the return line may be reduced utilizing a pressure reduction valve and/or a flash tank. During pressurized transferring of the slurry from the pumps to a treatment vessel (which may be as little about 10 feet or as much as about a half a mile away) treatment liquid is provided which contains at least some active pumping chemical including sodium hydroxide, sodium sulfide; polysulfide, anthraquinone or their equivalents or derivatives; surfactants, enzymes, or chelants; or combinations thereof. Pseudo-countercurrent circulation of treatment liquids may be provided between stations.

Method for feeding comminuted fibrous material

DOM control in cellulose pulp production

Low dissolved solids control in pulp production

A system and method for feeding comminuted cellulosic fibrous material such as wood chips to the top of a treatment vessel such as a continuous digester provide enhanced simplicity, operability, and maintainability by eliminating the high pressure transfer device conventionally used in the prior art. Instead of a high pressure transfer device the steamed and slurried chips are pressurized using one or more slurry pumps located at least thirty feet below the top of the treatment vessel and for pressurizing the slurry to a pressure of at least about 10 bar gauge. A return line from the top of the digester may, but need not necessarily, be operatively connected to the one or more pumps and if connected to the pumps the pressure in the return line may be reduced utilizing a pressure reduction valve and/or a flash tank. Steam from the flash tank may be used in steaming the chips. Pressure relief prevention may be provided by isolation valves in the lines leading to and from the top of the treatment vessel controlled by a controller which is responsive to the pressure sensed in the slurry line leading to the top of the treatment vessel.

Method and system for feeding comminuted fibrous material

A method and system for treating waste liquors from pulping processes for recovering energy and chemicals from the waste liquors (such as kraft black liquor). A recovery boiler having a furnace for combusting waste liquor includes a plurality of injection nozzles in the furnace walls, for injecting waste liquor into the furnace. At least one conduit is disposed in at least one wall of the furnace below the nozzles for withdrawing a portion of the combustible gas from the furnace. Typically between about 10-50% of the combustible gas produced in the furnace is withdrawn through the conduit or conduits below the nozzles, and the withdrawn gas is cooled and purified. The system may utilize a superheater which is separate and distinct from the recovery boiler, the cleaned and cooled withdrawn gas led to the separate superheater.

Method and apparatus for increasing recovery boiler capacity by

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

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Suwanee, GA, United States of America

Rolf C Ryham