The Boc Group, Inc.

Rustam H Sethna

Mark J Kirschner

Atul M Athalye

Ramakrishnan Ramachandran

Satish S Tamhankar

Ron C Lee

Michael K Sahm

Richard W Potthoff

William M Kulik

A method for producing bleached wood pulp in which wood chips are digested in polysulfide liquor to produce brown stock pulp. The brown stock pulp is washed to produce washed brown stock wood pulp and weak black liquor and the washed wood pulp is then delignified in an oxygen delignification stage to produce oxygen delignified wood pulp. The delignified wood pulp is then ozone bleached in an ozone bleaching stage in which a waste stream principally containing ozone, carbon dioxide and oxygen is produced. The ozone-bleached pulp is introduced into an extractive oxidation stage which can include peroxide to further bleach the pulp and the product of the extractive oxidation stage is then either introduced into either a peroxide or chlorine dioxide bleaching stage. The waste stream is recovered and scrubbed with either white liquor, oxidized white liquor, or fully oxidized white liquor either in a separate scrubber or during oxidation reactions occurring in either polysulfide, white liquor or complete white liquor production stages. The scrubbing with white liquor or oxidized white liquor removes ozone and carbon dioxide so that the scrubbed stream can be utilized in the oxygen delignification stage. This eliminates the need for ozone destruct units. Moreover, the polysulfide liquor is utilized in the digestion of the wood pulp and the thiosulfate liquor is used in the oxygen delignification of the washed wood pulp. The fully oxidized white liquor can be utilized within the extractive oxidation stage and optionally can be used in a peroxide bleaching stage if present. The oxygen removed from the scrubbed stream can be balanced with oxygen demand of the foregoing stages.

Pulp bleaching method wherein an ozone bleaching waste stream is scrubbed to form an oxygen containing stream

White liquor produced from black liquor is partially or completed oxidized. The white liquor contains dregs that are utilized as a carbon based catalyst. Dregs are produced by separating the dregs from green liquor an intermediate product between the black liquor and the oxidized white liquor. After formation of the oxidized white liquor, the dregs are separated therefrom to form a waste dreg stream which can be recycled so that part of the dregs present within the dregs containing white liquor stream to be oxidized is contributed by the waste dreg stream.

Method of producing oxidized white liquor using dregs containing carbon

Terephthalic acid is produced by reacting paraxylene with oxygen in a reactor having several vertical stages, the reaction taking place in the liquid phase using acetic acid as solvent and a cobalt-manganese-bromine complex catalyst. During the reaction, a carbon dioxide-containing gas phase is withdrawn from the vapor space of the reactor. The gas phase is cooled to condense vaporized acetic acid therefrom and carbon dioxide is separated from the gas phase and recycled to the vapor space or to the liquid phase or to both of these. In an alternate embodiment, the gas remaining after condensing acetic acid is subjected to catalytic oxidation to oxidize carbon monoxide and methane, if present, to carbon dioxide, and some or all of the carbon dioxide is recycled to the reactor.

Production of terephthalic acid

A gas injection apparatus for injecting a gas into a liquid comprising a baffle plate, a re-circulation chamber, and a discharge nozzle. The discharge nozzle is oriented normally to the baffle plate so that a liquid stream composed of the liquid is directed against the baffle plate and produces an oppositely directed flow towards the outer peripheral edge of the baffle plate. The oppositely directed flow has a sheet-like turbulent flow regime located adjacent to the plate and a circulating flow regime located above the turbulent flow regime and bounded by a re-circulation chamber. The gas is mixed into the liquid so that smaller bubbles are entrained in the turbulent flow regime and are discharged with the liquid flowing in the turbulent flow regime from the outer peripheral edge of the baffle plate. Larger bubbles flow into the circulating flow regime to break up into smaller bubbles which are entrained in the turbulent flow regime swept out of the apparatus. The apparatus is particularly useful in a gold leaching process in which the gold slurry is thickened to produce clarified water. Oxygen is injected into the clarified water and thereafter, the clarified water is injected into a leaching tank.

Gas injection apparatus and method having application to gold leaching

An oxygen delignification method and apparatus in which a charge of heated wood pulp is reacted with oxygen in the presence of a charge of caustic soda in a plurality of reaction stages located between mixing stages in which caustic is mixed with the wood pulp. The use of the plurality of mixing stages reduces peak pH exposure of the wood pulp that would otherwise occur if the charges of caustic and wood pulp were mixed all at once. Moreover, the caustic mixed in such manner replenishes neutralized caustic and ensures that the average pH level is increased above that in conventional oxygen delignification. The increase in average pH level favors an increase in the delignification. Filtrate from a washing stage is introduced into the mixing stages to prevent wood pulp degradation. Oxygen is mixed within the wood pulp by a wood pulp mixer that employs coaxial perforate passageways between which the wood pulp is retained and driven but which allow the oxygen to pass in an inward radial direction of the passageways to mix with the wood pulp.

Wood pulp reactor

An apparatus and method for dispersing a gas in a liquid and for increasing gas pressure of a gas from a supply pressure to a delivery pressure. A first pump pumps the liquid to produce a pressurized liquid stream. The gas is injected into the pressurized liquid stream through for instance, a piping tee. The gas injection produces a pressure drop within the gas and as a result, the first pump pumps the liquid stream so that it has a static pressure no greater than the injection pressure. A second pump pumps the resultant pressurized gas-liquid stream so that an outlet liquid stream is produced with the liquid having a greater head than that of the pressurized liquid stream and the gas having the increased delivery pressure.

Gas injection apparatus and method

Oxygen delignification method incorporating wood pulp mixing apparatus

A method of producing oxidized white liquor from white liquor in which sodium sulfide is oxidized to sodium sulfate. In accordance with the method, an oxygen containing gas is contacted with the white liquor at a temperature of at least 110.degree. C. and such that the total pressure of oxygen and water vapor is no less than 9.2 atmospheres during the contacting.

Oxidation of white liquor using a packing column

The present invention provides a food processing system and method for refrigerating articles of food. The food processing system includes at least two cooling stages formed by a cryogenic freezer and a hydrocooler. The cryogenic freezer receives the articles of food and transfers heat from the articles of food to the cryogen so that the articles of food are refrigerated. After the transfer of heat from the articles of food to the cryogen, the cryogen boils off to form cryogenic vapor. The hydrocooler receives the articles of food prior to the cryogenic freezer and transfers heat from the articles of food to supplied cooling water. Such heat transfer reduces the quantity of cryogen required to refrigerate the articles of food. Additionally, an eductor is connected to a pump and to vent line from the cryogenic freezer. The cooling water is pumped through the eductor to suction cryogenic vapor from the cryogenic freezer and to mix the cryogenic vapor and the cooling water prior to reception of the cooling water in the hydrocooler. Such mixing transfers heat from the cooling water to the cryogenic vapor to increase the heat transfer between the articles and the cooling water in the hydrocooler. As a result of such increased heat transfer, the amount of cryogen required in refrigerating the articles is further reduced The eductor and pump combination has general application to the cooling of articles.

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New Brunswick, NJ, United States of America

Rustam H Sethna