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High temperature processs for causticisation of a Bayer liquor

A Bayer, high-temperature technology, applied in the preparation of alkali metal aluminates/alumina/aluminum hydroxide, etc., which can solve the problems of downgrading, not providing C/S ratio, etc.

Active Publication Date: 2014-12-10
WORSLEY ALUMINA PTY LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, although Roche et al. advocate a residence time of less than 15 minutes at 140 °C, Roche et al. provide no information on how to avoid degradation of the C / S ratio during the cooling process prior to separation

Method used

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  • High temperature processs for causticisation of a Bayer liquor
  • High temperature processs for causticisation of a Bayer liquor
  • High temperature processs for causticisation of a Bayer liquor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0096] Example 1: Lime as causticizing agent in the presence of TCA inhibitors

[0097] In this example, the causticizing agent was slaked lime slurried in deionized water, and the Bayer process liquor was the first flusher overflow. The TCA inhibitor used was sodium gluconate, which was added to the first washer fluid prior to lime addition so that the final concentration after lime slurry addition was 0.075 g / L. The initial A, C and S of the first flusher overflow are shown at 0 minutes in Table 1 below.

[0098] The first flusher overflow is collected from the refinery and filtered to remove suspended solids. The filtered liquor (1.999 L) was then added to a 3.75 L stirred plate reactor along with the TCA inhibitor. The reactor was sealed and the liquid was heated to 140°C.

[0099] A slurry of technical grade slaked lime (available with Ca(OH) 2 84.7%). This slaked lime charge was calculated to increase the C / S of the first washer overflow to 0.945, assuming 90% lim...

Embodiment 2

[0107] Example 2: Lime as causticizing agent - no reaction solids fast from reaction slurry quick separation

[0108] This example demonstrates the effect on the C / S ratio when lime is used as causticizing agent (without addition of TCA inhibitor) and no rapid separation of reaction solids is performed. In this example, the first washer overflow is collected from the refinery and filtered to remove suspended solids. The filtered liquor (2.630 liters) was then added to a 3.75 liter stirred plate reactor, which was sealed and the liquor was then heated to 144°C. The initial A, C and S for the first flusher overflow are shown at 0 minutes in Table 2 below.

[0109] A sample of the slaked lime slurry was taken from the refinery and analyzed for % solids (23.0%), and the filtered and rinsed solids were dried and analyzed by XRF to give dry Ca(OH) 2 content (62.64% as CaO). This lime slurry charge was calculated to increase the C / S of the first washer overflow to 0.945, assum...

Embodiment 3

[0116] Example 3: Lime as causticizing agent - after separation of reaction solids from reaction slurry previous cooling effect

[0117] In this example, the causticizing agent was slaked lime slurried in deionized water, and the Bayer process liquor was the first flusher overflow. The TCA inhibitor used was sodium gluconate, which was added to the first washer fluid prior to lime addition so that the final concentration after lime slurry addition was 0.075 g / L. The initial A, C and S for the first flusher overflow are shown at 0 minutes in Table 3 below.

[0118] The first flusher overflow is collected from the refinery and filtered to remove suspended solids. The filtered liquor (2.000 liters) was then added to a 3.75 liter stirred plate reactor along with the inhibitor, the reactor was sealed and the liquor was then heated to 140°C.

[0119] A slurry of technical grade slaked lime (available with Ca(OH) 2 84.8%). This slaked lime charge was calculated to increase th...

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Abstract

A high temperature causticisation process for the causticisation of a Bayer process liquor is disclosed. The process comprises the steps of: a) adding a quantity of a causticising agent to the Bayer process liquor in a reactor vessel operating at a target reaction pressure for a given target reaction temperature, b) allowing the causticising agent to react with the Bayer process liquor for a sufficient residence time to produce a reaction slurry comprising a quantity of reaction solids in a causticised Bayer liquor; and, c) subjecting the reaction slurry to solid / liquid separation at a target separation temperature to produce a separated stream of reaction solids and a product stream of clarified cauticised Bayer liquor. The process is characterised in that the target reaction temperature is not less than 115°C and the target separation temperature is not less than 115°C.

Description

technical field [0001] The present invention relates to methods and systems for causticizing (causticizing) Bayer liquors. Background technique [0002] In the Bayer process for alumina production, a concentrated sodium aluminate solution is produced by grinding and cooking bauxite in a caustic solution, usually under conditions of high temperature and pressure. After purification of the slurry, the concentrated sodium aluminate solution is cooled and seeded with gibbsite crystals, causing the gibbsite to crystallize from solution. The gibbsite is calcined to produce alumina while the spent (or "spent") liquor is recycled to cook more bauxite. [0003] During cooking, some caustic is consumed in undesired reactions with impurities within the bauxite, reducing the productivity of the liquor. One of the most important of these reactions leads to the formation of sodium carbonate, either from the dissolution of inorganic carbonates within the existing mineral phase, or from t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F7/06
CPCC01F7/06
Inventor 史蒂文·菲利普·罗森贝格达雷尔·詹姆斯·威尔逊丹尼尔·马克·罗沃斯
Owner WORSLEY ALUMINA PTY LTD