Abstract: A feeding system for feeding comminuted cellulose containing material and liquid to a continuously operating treatment vessel. The feeding system comprises a chute, operating at a first pressure, a high pressure feeder sluices the material to a second pressure, that is higher than the first pressure, for further conveyance to the treatment vessel. The high pressure feeder also receives a return liquid flow from the treatment vessel at the second pressure and recirculates a recirculation flow to the chute. The high pressure feeder is in fluid communications, regarding both the liquid and the material, with the recirculation flow when any of the pockets of the high pressure feeder is in a location which corresponds to an outlet for the recirculation flow.

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 controlling the pH of the liquid circulation in a continuous prehydrolysis apparatus where a mineral acid or some other acid stronger than sulfurous acid is used as a hydrolysis agent and the material to be hydrolyzed is transferred, entrained in the liquids of a first and a second liquid circulation separated by a liquid exchanger, from a steaming vessel to a hydrolysis vessel by means of a transfer valve. Such an amount of alkaline sulfite or ammonium sulfite is added into the liquid of the first liquid circulation as is necessary to make the liquid alkaline or at least neutral.

Abstract: A process and apparatus for producing pulp from impregnated cellulose-containing starting materials such as wood, straw, grass, waste materials etc. in a compacting apparatus comprising a shell (1) and two mutually opposite pistons (4, 4') contained in the shell. The material to be compacted is disposed between the pistons and constitutes a resistive electrical load. The pistons are movable relative to each other and the shell is movable relative to the pistons. The impregnated starting materials are digested at a relatively low hydromodulus of 0.5 to 2 with a direct action of heat on the impregnated starting materials in the compacting apparatus at a digesting temperature of 160.degree. to 300.degree. C. The digesting times are short and depend on the digesting temperature.

Abstract: A process for making a refiner mechanical pulp from wood chips which comprises:(a) Comminuting the wood chips largely by splitting along the wood grain;(b) Wetting said particles with a solution of a sulphite salt of an alkali metal to add an amount of said alkali metal salt within the range of 1% to 10% of the oven dry weight of said particles, said solution having a pH within the range of 7 to 12.5;(c) Steam heating the sulphite salt solution bearing particles to a temperature within the range between 80.degree. C. and 165.degree. C. and holding them within that temperature range for a period of 0.5 to 80 minutes;(d) Passing the particles, after said period of heating, through a disc refiner to produce refiner mechanical pulp.

Abstract: A process for improving the strengths and resistance to water absorption of wood fiber hardboard, along with a lessening in the number of conventional steps, is disclosed. Hardboad is thereby produced by a process wherein drying oil is added to the wood chips prior to the pulp preparation stage; and optionally an oxidation accelerator is added during the pulp preparation stage. The hardboard is then formed in the usual manner without requiring the conventional addition of binder ingredients in the stock chest, without requiring conventional baking following pressing and, in the case of "tempered" hardboard without requiring the subsequent addition of tempering materials and baking following the conventional press operation.

Abstract: The continuous treatment of a cellulosic material in the form of chips to produce at least partial delignification of the material without true mechanical grinding is effected in apparatus comprising two parallel meshing screws which are rotated in the same direction in a sheath and have identical threads providing a plurality of zones of different pitch. The material is passed in succession through a first zone for feeding the material downstream, a first braking zone for causing a first compression of the material, a second zone for feeding the material downstream and in which the material is brought into contact with a reagent, e.g. steam or a chemical reagent, and a second braking zone for causing a second compression of the material.

Abstract: Chemical cellulose is produced by treatment in a digester. In the first step, wood in the form of chips is treated for a period of about from 15 to 90 minutes with a cooking acid of a calculated amount of below 5% by weight and at least 2.5% by weight of SO.sub.2 and a mole ratio of SO.sub.2 to MgO or CaO of from about 2 : 1 to 3.5 : 1 at a temperature of from about 45 to 90.degree. C. The liquid SO.sub.2 is fed into the digester until the total SO.sub.2 content of the cooking acid is from about 6 to 10 percent by weight, and completing the digestion in a second step to obtain a pulp by cooking at a temperature of above 110.degree. C., and working up the pulp in a manner known per se to obtain chemical cellulose.

Abstract: Significant yield increases are obtained in pulping of wood or other lignocellulosic materials with polysulfide liquors through particular control of the times and temperatures of treatment. The lignocellulosic material is treated with a polysulfide liquor at less than 100.degree. C for about 45 minutes, the liquor is removed for reuse, the impregnated lignocellulosic material is quickly steamed to pulping temperature and is pulped at a low temperature of about 160.degree. C for a short period of time.

Abstract: Impregnation of fiber material before digestion is accomplished utilizing a minimum amount of equipment. Liquid with entrained fiber material -- both fiber material sufficiently impregnated with liquid to be denser than the liquid and material insufficiently impregnated to be denser than the liquid -- is fed from a high-pressure transfer valve to an inlet at the top of a continuous digester. The digester has an outlet disposed vertically above the inlet, and liquid along with fiber material of lesser density than the liquid is withdrawn from the outlet. The withdrawn liquid and fiber material is recirculated back to the transfer valve through a conduit adapted to allow the passage of fiber material entrained in liquid therethrough. Each individual portion of fiber material is continuously circulated until it becomes sufficiently impregnated with liquid to descend into the digester and form a fiber column therein.

Abstract: An apparatus and method for impregnating fiber material with treatment liquid before treatment thereof in a high pressure vertical fiber material treatment vessel. Fiber material and treatment liquid under relatively low pressure flow in a first flow system, continuous withdrawal of liquid from the first system taking place. A second flow system of fiber material and treatment liquid, under relatively high pressure (the second flow system including an impregnation portion of the treatment vessel), is provided. Fiber material entrained in liquid in the first system is transferred to the second system, and the pressure thereof boosted, by a pocketed-rotor transfer device.