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Method of improving causticizing efficiency of recovered white liquor

A technology of causticizing rate and white liquor, which is applied in the field of alkali recovery causticization, can solve the problems of high residual alkali and low conversion rate of white mud, and achieve the effects of strengthening digestion, strengthening causticizing reaction rate, and enhancing uniformity

Active Publication Date: 2019-04-09
ZHEJIANG UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Such as the applied Chinese invention patents CN98109098, CN201610837446, CN201210044136, etc., these measures can effectively improve the causticization rate and yield in the alkali recovery process, but there are still problems such as low conversion rate and high residual alkali in white mud

Method used

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  • Method of improving causticizing efficiency of recovered white liquor
  • Method of improving causticizing efficiency of recovered white liquor
  • Method of improving causticizing efficiency of recovered white liquor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] (1) Pass the quicklime through a 300-mesh sieve after crushing to obtain quicklime with a particle size of 300 mesh.

[0028] (2) Mix 1.0 kg of quicklime (calcium oxide content: 80%) sieved in step (1) with dilute white liquor (NaOH concentration: 8 g / L) according to 1 kg: 3 L, digest and react at 60 ° C for 20 min, and use The grinder was wet-grinded until fully emulsified, and then passed through a 100-mesh sieve through a screw extruder to obtain 1.0 kg of fine lime milk with an average particle size of 25 μm, and the residual CaO mass content in the dry sample was 0.8%.

[0029] (3) After the green liquor is left to be clarified, the supernatant is taken as the clarified green liquor (Na 2 CO 3 Content 125g / L), separated by microfiltration membrane (cut-off pore size 1.0μm) to obtain fine green liquid, in which Na 2 CO 3 Content 120g / L.

[0030] (4) First mix 5.5L of fine green liquid and sodium acetate according to the ratio of adding 5g of sodium acetate per 1...

Embodiment 2

[0033] (1) Crushing quicklime and passing through a 400-mesh sieve to obtain quicklime with a particle size of 400 mesh.

[0034] (2) Mix 1 kg of quicklime (calcium oxide content: 80%) sieved in step (1) with dilute white liquor (NaOH concentration: 5 g / L) according to 1 kg: 1 L, digest and react at 80 ° C for 20 min, and use grinding Machine wet grinding until fully emulsified, and then passed through a 400-mesh sieve through a screw extruder to obtain 1.1 kg of fine lime milk with an average particle size of 17 μm, and the residual CaO content in the dry sample is 0.6%.

[0035] (3) After the green liquor is left to be clarified, the supernatant is taken as the clarified green liquor (Na 2 CO 3 Content 125g / L), separated by microfiltration membrane (cut-off pore size 0.5μm) to obtain fine green liquid, Na 2 CO 3 Content 115g / L.

[0036] (4) According to the ratio of adding 10g sodium phosphate to every 1L fine green liquid, 5.5L fine green liquid and sodium phosphate are...

Embodiment 3

[0039] (1) Crushing quicklime and passing through a 500-mesh sieve to obtain quicklime with a particle size of 500 mesh.

[0040] (2) Mix 1 kg of quicklime (calcium oxide content: 80%) sieved in step (1) with dilute white liquor (NaOH concentration: 2 g / L) according to 3 kg: 1 L, digest and react at 100 ° C for 20 min, and then use grinding Machine wet grinding until fully emulsified, and then passed through a 500-mesh sieve through a screw extruder to obtain 1.2 kg of fine lime milk with an average particle size of 10 μm, and the residual CaO content in the dry sample is 0.4%.

[0041] (3) After the green liquor is allowed to stand for clarification, the clarified supernatant is obtained as the clarified green liquor (Na 2 CO 3 Content 125g / L), separated by microfiltration membrane (cut-off pore size 0.1μm) to obtain fine green liquid, Na 2 CO 3 Content 110g / L.

[0042] (4) According to the ratio of adding 15g of sodium citrate per 1L of fine green liquid, mix 5.5L of fin...

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Abstract

The invention discloses a method of improving the causticizing efficiency of recovered white liquor. The method comprises the following steps: dissolving a melt combusting in an alkali recovery furnace in water to form green liquor, leaving the green liquor to stand and clarify, taking a supernatant liquid to obtain clarified green liquor, and separating the green liquor through a micro filtrationmembrane to obtain concentrated green liquor; adding an additive into the concentrated green liquor, then adding fine lime milk for a digestion reaction and filtering the mixture, and washing the obtained precipitate with diluted white liquor till the pH is 7.5-9.0 to obtain a fine calcium carbonate solution; adding the fine calcium carbonate solution and the additive into the clarified green liquor, separately and then adding fine lime milk for a causticizing reaction, and carrying out solid-liquid separation through a vacuum pre-hanger to obtain white liquor; and generating fined calcium hydroxide particles in a manner of digestive causticizing separation, then by adopting a spiral extruding and filtering form, culturing calcium carbonate crystal seeds by combining with a crystal importing method and a crystal form control technology and finally, injecting crystal nucleuses into the green liquor to carry out the causticizing reaction. The measures improve the causticizing effect greatly, and the causticizing rate can reach over 90%.

Description

technical field [0001] The invention relates to an alkali recovery causticizing method, in particular to a method for increasing the alkali recovery white liquor causticization rate. Background technique [0002] Recently, with the strengthening of the central government's environmental protection supervision, the pollution problem of papermaking wastewater is gradually entering people's field of vision, and the alkali recovery section is a more important part. Since the causticization rate is an important index to measure the conversion efficiency of alkali recovery, a low causticization rate not only means that the efficiency of alkali recovery is low, but also directly increases the residual alkali rate in white mud. At present, in the process of alkali recovery, factories usually use the causticization method to recover caustic soda. Due to factors such as the complex composition of quicklime and the many impurities in the green liquor, the causticization rate is not hig...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F11/18C01D1/22
CPCC01D1/22C01F11/18
Inventor 邱金锋陈东之陈建孟叶杰旭成卓韦张士汉
Owner ZHEJIANG UNIV OF TECH
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