Abstract: A method for recycling waste material including waste paper comprises the steps of introducing the waste material into a pressure vessel, re-pulping the waste paper in the pressure vessel at an elevated processing temperature and pressure to form a treated waste material including substantially re-pulped waste paper, thereafter introducing cooling water into the pressure vessel so as to cool the treated waste material in the pressure vessel to a discharge temperature below the elevated processing temperature and reduce odor emitted by the treated waste material, and thereafter discharging the treated waste material from the pressure vessel. The recovered paper pulp fraction is suitable as a feedstock in the manufacture of a variety of paper products including paper tissue and paper towel products.

Abstract: In a method for processing flue gases, flue gases from an incineration plant for non-condensable gases of a kraft pulp mill are scrubbed by means of a calcium compound. The calcium compound is lime mud taken from the chemical recirculation of the kraft pulp mill after causticization and before a lime reburning kiln, and it is used in the scrubbing of gas as a substance reacting with sulphur dioxide.

Abstract: A method for feeding a cellulosic fibrous material to a high pressure processing vessel including: pressurizing a low pressure flow of the fibrous material in a high pressure transfer device; discharging a high pressure flow of the fibrous material from the transfer device to a conduit in fluid communication with the processing vessel; discharging a low pressure flow of fluid and fibrous material from the transfer device; downstream of the transfer device, pressurizing the discharged low pressure flow; merging the pressurized low pressure discharge flow with the discharged high pressure flow, and transferring the merged flow to the processing vessel.

Abstract: A process for manufacturing a cellulosic paper product is provided. The process comprises forming an aqueous suspension of papermaking fibers; introducing a borate compound, preferably boric acid, into the aqueous suspension; depositing the aqueous suspension onto a sheet-forming fabric to form a wet web; and dewatering and drying the wet web. The process of the present invention provides cellulosic paper products exhibiting a reduced malodor upon re-wetting.

Abstract: An aqueous stream such as pulp mill condensate containing one or more sulfur compounds is treated by (a) reacting an aqueous feed stream containing TRS contaminant selected from the group consisting of hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide, and mixtures thereof, with ozone to produce a first liquid product stream and a first gaseous product stream, wherein the total amount of said one or more contaminants in said first liquid product stream is less than 1% of the amount thereof in said feed stream, and wherein said first gaseous product stream contains ozone and one or more of said contaminants; and (b) treating said first gaseous product stream with an alkaline aqueous stream to remove essentially all of said one or more contaminants from said first gaseous product stream. Preferably, a second gaseous stream produced in step (b) and containing ozone is reacted with an aqueous stream containing one or more of said contaminants, to consume all the ozone in said stream.

Abstract: A process and an apparatus in black-liquor evaporation for the selective removal, by liquid absorption, of hydrogen sulphide from the generated gas (3) containing hydrogen sulphide as well as carbon dioxide, an disclosed. In the process, the gas is counter-currently brought into multistage contact, preferably comprising three stages (6, 7, 8), with circulating carbonate-containing alkaline solutions, preferably sodium carbonate solutions (25), the pH of which is adjusted during the absorption to about 9-12 by the addition of a hydroxide, preferably a sodium hydroxide solution (26, 27, 28). It is preferred that the gas flow is turbulent and the liquid flow is laminar when contacted with one another. The apparatus comprises a container (1) having a gas inlet (2), a gas outlet (4), and a packing (9) arranged in several successive stages (6, 7, 8).

Abstract: The release of malodorous TRS-containing gases from a comminuted cellulosic fibrous material feed system for a digester is minimized utilizing a particular arrangement associated with a pressure isolation device. Material is fed through the pressure isolation device and the pressure of the material increases from the inlet to the outlet, and the material is discharged from the pressure isolation device into a treatment vessel, such as a horizontal steaming vessel. Malodorous gases from the pressure isolation device are discharged substantially independently of the material discharged from the isolation device, and at least some of the malodorous gases discharged from the pressure isolation device are pressurized (e.g. in an eductor or thermocompressor) and reintroduced into the flow of cellulosic material downstream of the pressure isolation device (for example into the horizontal steaming vessel or a vessel downstream of it).

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: A method is provided for reducing emissions of harmful nitrogen compounds from a pulp mill (e.g. kraft mill) having malodorous gases which include ammonia and reduced sulphur compounds therein. The method is practiced by (a) treating the pulp mill malodorous gases to lower the ammonia content thereof (e.g. by washing them with a bisulfite solution, such as one produced from washing flue gases with sodium sulphite), and then (b) burning the malodorous gases (e.g. in a dedicated incinerator, recovery boiler, power boiler, or lime kiln) under conditions which effect oxidation of reduced sulfur compounds therein (e.g. with an air excess of at least about 3% and a temperature of over 800 degrees C) so as to reduce odor emissions and emissions of harmful nitrogen compounds from the pulp mill.

Abstract: An integrated flue gas treatment and condensing heat exchanger is used to scrub sulfur dioxide from the flue gas produced by a power boiler used in a paper mill operating a kraft process. Sensible and latent heat from the flue gas is recovered and the condensate effluent from the condensing heat exchanger contains valuable chemicals that are returned to and used in the kraft process.

Abstract: A method for reprocessing an ozone-containing gas present in a pulp bleaching plant comprising the steps of supplying the ozone-containing gas to a scrubber and reducing the ozone concentration of the gas as the gas flows through the scrubber. The step of reducing comprises the steps of supplying an alkaline medium to the scrubber and flowing the ozone-containing gas in countercurrent relationship with the alkaline medium within the scrubber so as to provide intimate contact between the ozone-containing gas and the alkaline medium, thereby converting the ozone-containing gas into a substantially ozone-free gas. The alkaline medium may comprise one of the following: a sodium hydroxide solution; white liquor; post oxygen stage filtrate; weak black liquor; or filtrate from an Eo stage of the pulp bleaching plant. The method further comprises the step of separately discharging the ozone-containing gas and the alkaline medium from the scrubber.

Abstract: A method of preparing a digesting liquor having high sulphidity from a spent liquor obtained from digesting cellulosic fiber material, optionally without a conventional causticizing step is provided. Thermal decomposition of the spent liquor is conducted under reducing conditions in a reactor at a pressure of from atmospheric pressure up to about 150 bar and at a temperature of about 500.degree. to 1600.degree. C. so that a combustible gas phase containing hydrogen sulphide is formed in the reactor and extracted therefrom, and a phase of solid or molten material of substantially sodium sulphide or potassium sulphide, or mixtures thereof. The solid or molten material is dissolved in an aqueous liquid to produce said digesting liquor. The invention hydrogen sulphide is recovered from the gas phase and returned to the reactor to be present during the thermal decomposition of the spent liquor.

Abstract: A method for adjusting the sulphur/sodium ratio in a soda recovery boiler when strong sulphurous odour gases are burned therein. According to the method, sodium is introduced into the soda recovery boiler in an amount proportional to the amount of sulphur either as sodium hydroxide, sodium carbonate compounds or soap, whereby the sodium and sulphur react, forming sodium sulphate, which can be removed from the flue gases together with fly ash.

Abstract: A process for deodorizing tall oil rosin and tall oil fatty acids and their derivatives by treating same with an ammonium hydroxide solution under conditions of a steam sparge.

Abstract: This invention relates to an alkaline scrubber for condensate stripper off-gases. In particular, this invention relates a process for selectively removing hydrogen sulfide and methyl mercaptan from a gas stream containing these compounds and methanol. Such gas streams are commonly generated during pulp and paper production.

Abstract: Sulphur dioxide is separated from the flue gases of a cellulose pulp mill by absorbing it into a sodium sulphite solution. Sulphur dioxide is regenerated from the sodium bisulphite solution produced by an evaporation-crystallization method utilizing thermo-compressor evaporation technique. A lamella evaporator is utilized as the evaporator-crystallizer, the evaporator being divided into separate compartments for ease of cleaning the lamella surfaces. The recovered concentrated sulphur dioxide can be used wherever desired, for example for the production of chlorine dioxide.

Abstract: A method for washing pulp in a batch digester modified pulping process wherein black cooking liquor used for cooking the chips is partially displaced by pumping a first stage wash effluent into the bottom of the digester, additional amounts of the cooking liquor are displaced by pumping a second stage wash effluent, and so on, until sufficient increments of wash effluent have been pumped to displace the cooking liquor. A wash filtrate water is then pumped into the digester from a final pulp washing operation to displace the hot black liquor until all of the hot black liquor is sent to an accumulator, and the various wash effluents have been replenished in their respective stages.

Abstract: A process for cooking and bleaching pulp in a closed system, wherein spent liquors from the cooking and the bleaching are recovered and their chemicals are regenerated and recycled as cooking and bleaching chemicals.

Abstract: Process for the treatment of waste water and gases containing dialkyl disulphides by catalytic oxidation of these compounds by means of a peroxide compound in an aqueous medium. Divalent copper ions are used for the catalyst and the medium is kept at a pH below 6.5.

Abstract: A composition is provided which comprises an aqueous alkaline solution of a metal salt and black liquor, the metal salt being selected from the group consisting of iron, chromium, cobalt and nickel salts. This composition is useful in a process described for absorption of hydrogen sulfide from flue gas, followed by subsequent oxidation of dissolved sulfide to thiosulfate, if desired. The presence of the metal ions and black liquor synergistically catalyzes the overall reaction of absorption of hydrogen sulfide, followed by oxidation of the sulfide. Preferably, prior to scrubbing to remove hydrogen sulfide with the solution, the flue gas is first cooled to near its dew point, and then scrubbed with water to remove particulates. Additionally, the effluent flue gas from the absorption step is usefully scrubbed with water to recover heat, following which it is used to scrub condensates from a kraft pulp mill. The metal salt in the solution is preferably an iron salt at a concentration of about 0.002 M.

Abstract: Process for the treatment of waste water and gases containing dialkyl disulphides by catalytic oxidation of these compounds by means of a peroxide compound in an aqueous medium. Divalent copper ions are used for the catalyst and the medium is kept at a pH below 6.5.

Abstract: An improved method for removing malodorous sulfur compounds from flue gases generated in kraft or sodium sulfite pulping operations and the like by the absorption process using green liquor, an aqueous solution containing sodium sulfide and sodium carbonate. The malodorous gas compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide are preferentially absorbed by the sodium sulfide forming sodium hydrosulfide and methanol. Any sulfur dioxide in the gas is absorbed and neutralized by sodium carbonate. In this method carbon dioxide absorption is minimized and the formation of sodium bicarbonate is limited. Sodium bicarbonate formation is minimized in order to avoid its reaction with sodium hydrosulfide which would then release undesirable hydrogen sulfide during absorption, as well as to forestall the need to increase chemical and lime kiln capacity requirements when the green liquor returned to the kraft recovery process contains excess amounts of sodium bicarbonate.

Abstract: The digestion of the cellulose-containing material is performed with a digestion liquor containing sulphur and sodium followed by recovery and regeneration of said digestion liquor and bleaching of the cellulose-containing material with chlorine dioxide. The SO.sub.2 -containing and possibly chloride-containing gas from the recovery boiler (11) of the process and from combustion of evil-smelling gases (20) is absorbed in an absorption liquor containing and alkali metal salt solution free of sulphur or sulphur compounds such as sulphide or thiosulphate, in a scrubber (27). The resulting scrubber liquor is mixed with acid residual solution (26) from the manufacture of chlorine dioxide, whereby sulphur dioxide (32) in gaseous state is returned to the process, whereafter the residual solution (34) free from SO.sub.

Abstract: High heat recovery and minimized oxygen requirement for oxidation of sulfur compounds in black liquor is obtained by integrating the oxidation into the multiple effect evaporation system of the pulp mill recovery sequence. The oxidation step is carried out at an intermediate stage in the multiple effect concentration of weak black liquor in counterflow to the external heat input, and the thus oxidized liquor is then further concentrated by flow through the remaining effects of the system co-currently with the direction of heat flow.

Abstract: A process is disclosed in which a waste gas containing sulfur compounds and carbon dioxide from pulp mill is contacted with an aqueous alkali solution derived from green liquor, white liquor or weak white liquor having low pH value and low sodium ion concentration and having been oxidized, whereby the sulfur compounds are absorbed as completely as possible with minimal absorption of carbon dioxide in the waste gas.

Abstract: A method for oxidizing and removing remaining sodium sulfide as well as generated sulfur compounds by introducing oxygen into cooking liquor at high temperature and high pressure in the end stage of kraft cooking.

Abstract: High recovery of useful energy from the heat of reaction in the oxidation of black liquor is obtained by integrating the oxidation into the multiple effect evaporation system of the pulp mill recovery sequence. The heat of reaction is thereby recovered as flash steam, which when combined with the vapors from an appropriate evaporator body enables recovery of its energy through further evaporation. The oxidation reaction may be carried out on the liquor leaving the second effect of the evaporation sequence for maximum energy recovery, or in accordance with an alternative embodiment, the reaction is carried out between the first effect and the flash tank with preferable addition of a second flash tank in series with the first.

Abstract: A method for removing malodorous sulfur compounds from a fluid containing such compounds. In this method, fungi belonging to genera Cephalosporium, Paecilomyces, Penicillium, Aspergillus, Trichoderma and Mucor can be used for effectively removing malodorous sulfur compounds from a fluid.

Abstract: The process for producing pulp according to the present invention consists in the subsequent steps of an aqueous treatment of a vegetable stock at a temperature within the range of from 110.degree. to 170.degree. C. under a pressure of from 2 to 7 atm.g. for a period of from 0.3 to 4 hours at a weight ratio of the vegetable stock to water of 1:2-4 respectively; a simultaneous impregnation and cooking of said vegetable stock in a solution of nitric acid at a temperature of from 70.degree. to 90.degree. C. for 0.5-3 hours; cooking at a temperature of from 100.degree. to 130.degree. C. under a pressure of from 1 to 4 atm.g. for 0.3-0.5 hour; an alkali extraction of the vegetable stock; decontamination of the gaseous cooking products by mixing thereof with the air in a volumetric ratio of 1:0.5-1 respectively, and treatment with the spent liquor resulting from the stage of alkali extraction.

Abstract: Cooked pulp at an elevated temperature and pressure is discharged from a plurality of batch digesters sequentially into a first blow tank. The first blow tank is maintained at a substantially constant pressure which is less than the pressure in the digester and greater than atmospheric. Pressurized steam is released from the first blow tank into a dirty steam system as pulp is discharged into a second blow tank at a substantially constant rate in a non-interrupted flow stream. The pressure in the second blow tank is maintained at about atmospheric pressure. A blow line refiner is interposed between the first and second blow tanks.

Abstract: A process is provided for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulosic material with alkaline sodium- and sulfur-containing-sulfate pulping liquor, which comprises evaporating and burning spent sulfate pulping liquor to obtain a smelt; dissolving the resulting smelt in water to form a sodium-sulfide-sodium carbonate-containing solution green liquor; regenerating pulping white liquor containing sodium sulfide and sodium hydroxide from said green liquor; and recirculating said regenerated white liquor to the pulping stage; oxidizing at least one of the resulting green and white liquors to form sodium thiosulfate therein; reacting the oxidized liquor with residual acid liquor, from the manufacture of chlorine dioxide by reduction of an alkali metal chlorate solution, to convert thiosulfate to sulfur dioxide and sulfur; removing and recovering formed sulfur dioxide; and returning the residual liquor, freed from sulfur dioxide, to the pulping.

Abstract: Oxidation and fixing of sulfur and sulfur compounds in weak black liquor is accomplished by methods which insure minimal odorous sulfur emissions and which facilitate the collection of sulfate soaps. By critical adjustment of certain parameters substantially complete oxidation of sulfur and sulfur compounds is achieved, with maximum utilization of oxygen, while enhancing the collection of sulfate soaps and minimizing the production of foam. Various methods are disclosed for the oxygenation of weak black liquor, including the utilization of reaction columns, conical reactors, and venturis.

Abstract: The invention relates to a continuous method of making cellulosic pulp from wood chips within a range of yield from 65 to 90 per cent by digestion with a digestion liquor containing Na.sub.2 S and Na.sub.2 CO.sub.3. The digestion is effected at temperatures between 150.degree. and 190.degree.C and malodorous sulfur compounds are removed from the pulp, the liquor and the vapors prior to their withdrawal from the digesting process. In order to eliminate their capacity of emitting obnoxious odors, the sulfur compounds are oxidized by addition of molecular oxygen to the digester prior to discharge of pulp and spent liquor from the digester after which the spent liquor is removed from the digested pulp, concentrated and burned for renewed use in preparation of fresh digesting liquor.

Abstract: A new chemical recovery process and apparatus for a polysulfide pulping system is described wherein sulfur is recovered from the weak black liquor and is returned to the process, along with makeup sulfur, to reconstitute the polysulfide solution.After the polysulfide digestion, the spent liquor is contacted with ferric oxide Fe.sub.2 O.sub.3 whereby ferrous sulfide, FeS, is formed. After separation of the ferrous sulfide from the remaining liquid, the ferrous sulfide is oxidized to form elemental sulfur, and ferric oxide. After the melting of the sulfur and the separating of the products, the sulfur can be returned to the Sulfur Dissolving Tank wherein, along with makeup sulfur as required, the white liquor from the causticizing plant can be treated to form the polysulfide liquor for digestion. The ferric oxide can be reused for contacting the black liquor to form ferrous sulfide. The resulting smelt of reduced sulfidity from the recovery furnace can be reprocessed to form the white liquor.

Abstract: In a process for the production of fiber substances from waste which contains aerobically unstable components, the waste is subjected to aerobic decomposition at a temperature of at least 50.degree.C in the presence of oxygen to form a fibrous mass and then the mass is treated with solvents which dissolve these components. This eliminates the odor characteristic of fiber substances produced from waste. An arrangement for carrying out the process is also disclosed.