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Method for recovering chemicals and by-products from high-sulphidity pulping liquors

一种硫化度、化学品的技术，应用在从高硫化度制浆液回收化学品和副产物领域，能够解决成本高等问题

Inactive Publication Date: 2015-09-23
ANDRITZ AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This approach has proven to be cost-prohibitive

Method used

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  • Method for recovering chemicals and by-products from high-sulphidity pulping liquors
  • Method for recovering chemicals and by-products from high-sulphidity pulping liquors
  • Method for recovering chemicals and by-products from high-sulphidity pulping liquors

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Embodiment

[0109]EXAMPLE AND WITH NEW PROCESS The mass flow rates of the major components in the various liquid streams of the recovery procedure are provided in Tables 1-5 below. The example recovery procedure does not incorporate removal of by-products or non-process elements and acidification of spent pulping liquor. The acidification procedure is applied to the entire effluent stream. Where applicable, compare flow rates to those referenced to conventional kraft recovery procedures. In the case of the new method, the pulping of softwood was carried out at 80% degree of sulfidation and 17.5% EA (effective alkali as NaOH on wood), while in the reference procedure it was carried out at 35% degree of sulfide and 19.5% EA pulping. Other key assumptions are: (1) Na 2 S is fully hydrolyzed in the pulping liquor, ie sulfides are completely converted to hydrosulfides according to reaction 2, (2) reduction efficiency in the recovery furnace is 95%, and (3) causticity is 85%. Mass flow unit...

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Abstract

The subject of the invention is a new method to be used in connection with the recovery of pulping chemicals from the spent pulping liquor produced by kraft- type pulping at very high sulphidity. The sulphidity is most preferably in the range 70–100 %. In the new method, spent pulping liquor (5) is acidified to a relatively low pH, preferably below 7, most preferably below 6, in order to convert a large part, or all, of the sulphide and hydrosulphide in the liquor into H2S. Sulphur containing gases (19), mainly H2S, released from the spent pulping liquor, together with other sulphur gases collected at the pulp mill, are converted into an acid compound, preferably H2SO4 (9), which is then employed as an acidification agent in the previously mentioned acidification step. The amount of acid thus generated is sufficient to provide most, if not all, of that required for the acidification step. The acidification of the spent pulping liquor may be further exploited as a means to increase recovery of by-products and / or to purge non-process elements from the chemical-recovery cycle.

Description

technical field [0001] The method of the present invention involves the recovery of pulping chemicals, recovery of by-products and removal of non-process elements from pulping effluents produced in kraft pulping at very high degrees of sulfidation in pulp mills. Background technique [0002] In conventional kraft pulping procedures, the active pulping chemicals are sodium hydroxide (NaOH) and sodium sulfide (Na 2 S). Na 2 The amount of S relative to the amount of NaOH is characterized by a parameter called degree of sulfidation, which is defined as follows: [0003] Sulfur degree (%) = m Na2S x 100 / (m NaOH / 2+m Na2S ), where m Na2S is Na 2 moles of S and m NaOH is the number of moles of NaOH. [0004] In conventional kraft pulping procedures, the degree of sulfidity of the pulping liquor is usually in the range of 25-40%. In kraft pulping, it is often advantageous to increase the degree of sulfidation of the pulping liquor from the standpoint of the pulping stage. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): D21C11/00D21C11/06
CPCD21C11/06D21C11/0035D21C11/0007D21C11/04D21C3/022D21C11/0085D21C11/12
Inventor 佩特森·麦基奥
Owner ANDRITZ AG
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