Abstract: A calender hood for a paper machine having a dryer section and a calender section the hood extending along a portion of the paper path from the dryer section through the calender section to restrict movement of the ambient air into the region between the surface of the paper sheet and the calender hood and thereby reduce heat losses to the ambient air by the paper sheet.

Abstract: A supercritical water oxidation reactor is described having first and second reaction zones connected in series and through which an aqueous feed stream to be oxidized can be passed in either direction. A self-contained heat exchange fluid system allows supercritical and subcritical temperatures to be maintained in either reaction zone. When supercritical water oxidation is occuring in one reaction zone the effluent is being cooled to a subcritical temperature and used to flush the second reaction zone to remove inorganic scale.

Abstract: A supercritical water oxidation reactor is described having first and second reaction zones connnected in series and through which an aqueous feed stream to be oxidized can be passed in either direction. A self-contained heat exchange fluid system allows supercritical and subcritical temperatures to be maintained in either reaction zone. When supercritical water oxidation is occuring in one reaction zone the effluent is being cooled to a subcritical temperature and used to flush the second reaction zone to remove inorganic scale.

Abstract: A method for oxidizing organic material in an aqueous stream containing one or more inorganic salts, inorganic salt precursors or mixtures thereof, comprising oxidizing said organic material under supercritical conditions in the presence of an oxidant and a mobile surface of particles to which inorganic salts insoluble under the reaction conditions can adhere.

Abstract: A supercritical water oxidation reactor is alternately supplied with a feed stream and a flushing stream. The feed stream contains organic and inorganic materials. The organic materials are oxidized under supercritical conditions in the reactor and the inorganic materials precipitate out of solution under the same conditions. The flushing stream is a solution in which the inorganic material is soluble. More than one supercritical water oxidation reactor may be connected so that the feed stream is alternately supplied to each reactor. During the period when the feed stream is being supplied to a reactor the effluent from the reactor is cooled to a temperature at which inorganic precipitates are soluble and is then supplied as a flushing stream to one or more of the remaining connected supercritical water oxidation reactors.

Abstract: A process is provided for the bleaching of wood pulp with hydrogen or sodium peroxide. The process includes the steps of adding to a wood pulp a bleach liquor having an effective amount of hydrogen or sodium peroxide bleaching agent and, by weight of the diluted wood pulp, 0.5 to 6% sodium hydroxide, 0 to 5% sodium silicate, 0 to 1%, preferably 0.02 to 0.05%, magnesium sulphate, and a chelating agent in an amount sufficient to sequester heavy metal ions in the pulp, to produce a pulp consistency of 1 to 16% at a temperature in the range of the bleach liquor freezing point to 25.degree. C., uniformly mixing the bleach liquor with the wood pulp, and immediately thickening the diluted wood pulp to a consistency in the range of 20 to 70% for bleaching of the thickened wood pulp.

Abstract: Wood pulps, particularly sulphonate pulps, such as jack pine ultra-high-yield pulps produced by sulphonation, are readily discolored by metal ions commonly found in paper mills. Additions of 0.001 to 2% on pulp dry basis of tin ions, especially derived from stannous compounds, to wood pulps effectively brighten the pulps at ambient temperature.Metal ions such as ferrous, ferric, cupric, aluminum, nickel and manganese are common discoloring ions and pulps containing these ions can be brightened by the addition of tin ions particularly derived from stannous chloride, stannous sulphate, stannous tartrate, stannous oxolate, stannic chloride and stannic sulphate, the tin ions as Sn.sup.+2 being added in an amount to provide a ratio of stannous ions to discoloring metal ions up to about 2:1, preferably about 1.5:1.