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Process for controlling sodium and sulfur balance in pulp mill

A pulp mill, level technology, applied in the regeneration of pulping chemicals, chemical instruments and methods, water treatment parameter control, etc., can solve the problems of increasing NaOH, sulfur and increasing operating costs, so as to reduce the amount of alkali and improve sodium / Sulfur balance, high cost effect

Active Publication Date: 2021-03-19
STORA ENSO OYJ +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The fact that dust removal results in fresh NaOH loading means that increased mill sulfur incorporation will result in increased operating costs due to the need for increased NaOH loading

Method used

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  • Process for controlling sodium and sulfur balance in pulp mill
  • Process for controlling sodium and sulfur balance in pulp mill
  • Process for controlling sodium and sulfur balance in pulp mill

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0079] A continuous feed system consisting of a series of bioreactors is used. Using autotrophic sulfide-oxidizing bacteria from Soda lake, under sulfide-oxidizing conditions (pH 9.5; Na + >4M) to operate the system. The maximum wet volume of the reactor is 5L The temperature was maintained at 30°C by using a water jacket and a constant temperature bath (Shinko, Japan). The influent was fed to the bioreactor using a peristaltic pump (Watson-Marlow) and the effluent from the reactor was controlled by overflow. The sulfide-rich stream (influent) was mixed with a portion of the bioreactor contents prior to addition to the bioreactor. pH was monitored using a pH sensor (Endress+Hauser, The Netherlands). Oxygen supply was performed with an air feed controlled with an ORP-sensor (Endress+Hauser, The Netherlands).

[0080] The sulfide oxidizing bacteria present in the bioreactor are species adapted to elevated salt concentrations but not to the high salt concentrations of green...

Embodiment 2

[0087] Table 2

[0088] Savings in caustic consumption 3

2-A: No premix 2

Negligible <0.6kg NaOH / kg S removed

2-1 with premix 2

2.6kg NaOH / kg removed S

[0089] 2 Influent pulp mill stream – green liquor

[0090] 3 Separated from effluent

[0091] Example 2-1 shows that premixing the pulp mill stream with bioreactor contents increases sulfur production and caustic (NaOH) regeneration compared to Example 2-A where no premixing occurs (comparative).

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Abstract

The present invention relates to a process for the controlling the sodium and sulfur levels in a pulp mill, comprising the steps of: a) providing a pulp mill stream comprising sulfide and having a total alkali concentration of at least 2 Molar; b) supplying a portion of the pulp mill stream to a reactor comprising sulfide oxidizing bacteria and removing sulfide from the pulp mill stream by subjecting said stream to sulfide oxidizing bacteria in the presence of oxygen, and at a pH in the range 8 to 11, to oxidize the sulfide to elemental sulfur, c) withdrawing from the reactor a treated pulp mill stream comprising sulfur, wherein the portion of the pulp mill stream is mixed with a portion of the sulfide oxidizing bacteria present in the reactor prior to supplying the pulp mill stream to thereactor in step b).

Description

technical field [0001] The present invention relates to a method for controlling the sodium and sulfur balance in a pulp mill. Background technique [0002] The most common chemical wood pulping technology today is Kraft pulping (Kraft process) in which wood chips are cooked in so-called "white liquor". White liquor is a mixture of different chemicals (typically sodium hydroxide (NaOH) and sodium sulfide (NaOH) 2 S)) mixtures. This process releases cellulose fibers from wood chips, which produces a brown slurry. The pulp is then washed and used as unbleached kraft pulp or bleached to produce a white pulp. This slurry is then used for different paper products ranging from fine paper to board. [0003] The sodium and sulfur balance is a very important part of pulp mill economics, since sodium and sulfur recycling is a key factor in maintaining the process economics of a pulp mill, especially a kraft pulp mill. The loading of sodium hydroxide in the digester was related to...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): D21C5/00D21C11/00D21C11/02
CPCD21C5/005D21C11/0064D21C11/02C02F3/345C02F2101/101C02F2103/28C02F2209/06C02F2301/046D21C11/0078D21C11/0007D21C11/0057
Inventor 埃里克·梵·泽森米歇尔·保卢斯·玛丽亚·诺丁克里卡尔·沃兹伯恩奥利·蒂莫宁玛丽亚·比约克阿里·科蒂莱宁
Owner STORA ENSO OYJ
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