摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
Using a high pressure rotary adsorbent wheel, a high value compressed gas feed can be purified by concentrating the impurity such as water, condensing it out, before final purification. Instead of exhausting gas from the system, the effluent can be put back into the feed at a point prior to condensation of the high value gas feed, and therefore the entire feed is purified without any high value gas feed going into a waste stream.
摘要:
A method for optimising a mineral recovery process. A slurry 10 is fed to a conditioning step 20. The condition slurry 30 is then provided to a flotation circuit 40 to recover a concentrate 50. The remainder of the slurry is then rejected as tail 60 or passed for further processing. The present invention provides apparatus for analysing a sample stream 100 of the slurry. A sample stream 100 is provided to an analysis device 200 which treats the sample with an oxidising gas similar to the oxidative treatment 20. Several parameters are measured before and/or after the oxidative treatment of the slurry. The flotability characteristic of the slurry is then determined as a function of the measured parameter(s). The result is used to optimise mineral recovery. This apparatus can be used intermittently or continuously to provide on-going optimisation of the mineral recovery circuit.
摘要:
Methane collected from a landfill is used as a feedstock for the production of hydrogen in a steam methane reformer. This invention provides a green energy feed stock for the hydrogen production that benefits the environment.
摘要:
The present invention relates to a pressure swing adsorption process for direct reduction of iron wherein a portion of spent reducing gas withdrawn from the direct reduction reactor is subjected to a PSA process for the removal of carbon dioxide from the spent reducing gas. An improved CO2-rejection method using an external natural gas purge stream after depressurization and before the product purge step is described. The PSA process comprises an external purge step with a non-absorbable gas, which surprisingly reduces the adsorbent regeneration requirements to maintain the selective adsorption of carbon dioxide from the spent reducing gas. The external natural gas purge results in a cleaner bed before the start of each adsorption cycle. Consequently, significantly more CO2 can be rejected and/or higher hydrogen and CO recoveries can be attained. The external purge stream is fully integrated into the DDRI production scheme.
摘要:
A method for integrating a liquefied natural gas liquefier system with production of liquefied natural gas from a methane-containing gas stream. The liquefied natural gas is produced by feeding a methane-containing gas stream through a heat exchanger to a distillation column and liquefying the natural gas while capturing the gaseous nitrogen. The liquefied natural gas is captured and the nitrogen gas is recovered, fed through the heat exchanger to recover cold and purified.