Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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° 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° F., preferably about 300°) 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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. <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).

Abstract: Black liquor from a cellulose pulp processing plant is treated, including by using a direct contact (cascade) evaporator, without need for oxidizing the black liquor, without substantial sulphur emissions at the cascade evaporator, and by maximizing the solids content of the black liquor so that the loss of heating value of the black liquor is minimized. The black liquor is heated under temperature and time conditions sufficient to drive off most of the organic sulphur compounds as off gases, which gases are converted primarily to methane and hydrogen sulfide, with the methane separated by selective absorption in white liquor. The black liquor is then stripped of most remaining sulfur by bringing it into stripping contact with flue gases from the recovery boiler, the flue gases taken from downstream of the direct contact evaporator.