Method for preparing anhydrous sodium chromate

An anhydrous sodium chromate and sodium chromate technology, applied in the production of chromate/dichromate, bulk chemicals, etc., can solve the problems of waste of resources and high production cost, improve manpower, solve the problem of easy moisture absorption , the effect of good liquidity

Active Publication Date: 2017-05-10
SICHUAN YINHE CHEM
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  • Abstract
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  • Claims
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Problems solved by technology

This production process not only prepares sodium chromate containing tetrahydrate, but also goes back to the way of the process, resulting in waste of resources and high production costs

Method used

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  • Method for preparing anhydrous sodium chromate

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Effect test

Embodiment 1

[0028] A method for preparing anhydrous sodium chromate, including the following steps:

[0029] Step 1: Put 8m of sodium chromate alkaline solution 3 And carbonization method to prepare carbonization solution of sodium alum 1m 3 Put it into the pretreatment storage tank, sample and analyze the pH to be 8.2. After stirring at room temperature for 15 minutes, the pH is retested to be 8.3 to obtain the sodium chromate pretreatment solution; the concentration of the carbonization solution is 925g·L -1 (In Na 2 Cr 2 O 7 ·2H 2 O meter), pH is 5.8;

[0030] Step 2. Pump the sodium chromate pretreatment liquid to the continuous evaporation crystallizer, use steam as the heat source, heat up to 81°C, start the vacuum pump, and control the pressure in the evaporator at -0.09MPa; control well during the evaporation process Feed rate of sodium chromate pretreatment liquid, observe the precipitation of sodium chromate crystals, when the solid-liquid ratio is 50%, discharge to the concentrated l...

Embodiment 2

[0033] A method for preparing anhydrous sodium chromate, including the following steps:

[0034] Step 1: Add 7m of sodium chromate alkaline solution 3 And carbonization method to prepare the carbonization solution of sodium alum 2m 3 Add to the pretreatment storage tank, sample and analyze the pH to be 7.6, and after stirring for 15 minutes at room temperature, the pH is re-measured to be 7.6 to obtain the sodium chromate pretreatment solution; the concentration of the carbonization solution is 925g·L -1 (In Na 2 Cr 2 O 7 ·2H 2 O meter), pH is 5.8;

[0035] Step 2: The sodium chromate pretreatment liquid is pumped to the evaporation crystallizer, using steam as the heat source, the temperature is raised to 90°C, the vacuum pump is started, and the pressure in the evaporator is controlled at -0.07MPa. During the evaporation process, control the feed rate of the sodium chromate pretreatment liquid and observe the precipitation of sodium chromate crystals. When the solid-to-liquid rati...

Embodiment 3

[0038] A method for preparing anhydrous sodium chromate, including the following steps:

[0039] Step 1: Add 6m of sodium chromate alkaline solution 3 And carbonization method to prepare the carbonization solution of sodium alum 3m 3 Add to the pretreatment storage tank, sample and analyze the pH 7.1, stir at room temperature for 15 minutes and then re-test the pH 7.15 to obtain the sodium chromate pretreatment solution; the concentration of the carbonization solution is 925 g·L -1 (In Na 2 Cr 2 O 7 ·2H 2 O meter), pH is 5.8;

[0040] Step 2: The sodium chromate pretreatment liquid is pumped to the evaporation crystallizer, using steam as the heat source, the temperature is raised to 102°C, the vacuum pump is started, and the pressure in the evaporator is controlled at -0.04MPa. During the evaporation process, control the feed rate of the sodium chromate pretreatment liquid and observe the precipitation of sodium chromate crystals. When the solid-liquid ratio is 36%, the material is...

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Abstract

The present invention discloses a method for preparing anhydrous sodium chromate. The method comprises the steps of mixing a sodium chromate alkali solution with a carbonating solution in proportion of (1:1) to (8:1), and then, adjusting the pH to 6.5-8.5 to obtain a pretreatment solution of sodium chromate; placing the pretreatment solution of sodium chromate in an evaporation crystallizer for vacuum evaporation at the temperature of 80 DEG C to 120 DEG C under the pressure of 0.01 MPa to 0.09 MPa; and when the solid-to-liquid ratio reaches 10%-50% through vacuum evaporation, performing solid-liquid separation at the temperature of 70 DEG C or above to obtain anhydrous sodium chromate and a filtrate. Based on the technology characteristics of sodium dichromate preparation by a carbonation method, high-quality anhydrous sodium chromate is successfully prepared by the method disclosed by the invention, with the main content being equal to or greater than 99.5% and the content of all impurities such as sulfate being less than 0.001%; moreover, the product does not absorb moisture or cake even if stored for a long term, and has good fluidity. The problems of sodium chromate tetrahydrate on easy moisture absorption, caking and poor fluidity are successfully solved. The method also brings into play the superiority of a production process of preparing sodium dichromate from a chromium salt by the carbonation method, so that two high-quality chemical products can be produced on one production line.

Description

Technical field [0001] The invention relates to the field of preparation of chemical raw materials, in particular to a method for preparing anhydrous sodium chromate. Background technique [0002] Sodium chromate is the basic raw material of the chromium salt industry and is widely used in many important economic fields, such as inks, paints, pigments, metal corrosion inhibitors, organic synthetic oxidants, and various fields such as tanning, printing and dyeing. At present, the market demand for pigments and other industries is more than 20,000 tons. However, these industries do not directly use sodium chromate as a raw material. Instead, they all use sodium alumite as a raw material, and use NaOH to pull back to sodium chromate, and then carry out downstream product production and application. Sodium chromate to prepare sodium sulphate requires more than four steps such as sulfuric acid acidification (or carbonization, electrolysis), evaporation, crystallization, and centrifuga...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01G37/14
CPCC01G37/14C01P2006/80C01P2006/82Y02P20/54
Inventor 周中田陈宁董明甫王方兵谢友才黄先东张良魏俊刘玉洪
Owner SICHUAN YINHE CHEM
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