Process for producing sodium chromate by calcium-free calcination

A technology of calcium-free roasting and sodium chromate, applied in the direction of chromate/dichromate, etc., which can solve problems such as research, long process route, and problem of wall formation that cannot be fundamentally solved

Inactive Publication Date: 2005-02-16
TIANJIN CHEM RES & DESIGN INST +1
View PDF1 Cites 21 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the patent adopts the powder roasting process, which fails to fundamentally solve the problems of material segregation in the rotary kiln and the wall of the furnace material in industrial production, and cannot realize industrial production.
In addition, the patented chromium slag is processed by wet separation method and the coarse slag is returned to be used as filler, which has a long process route and high production cost
[0005] Domestic patented calcium-free granulation and roasting chromium salt production process: ZL93112820.X, adding accelerant to the rotary kiln material and adding accelerators to granulate and dry, and roasting with heavy oil. Although it can improve the chromium oxidation rate, the process route is long and the chromium residue is not separated. Choose to directly return 70% of the filler as a filler, and the amorphous glass body with a low melting point in the returned slag will be firmly bonded to the kiln wall after being melted during the roasting process, so that the problem of wall formation in industrial production cannot be fundamentally solved. , high production cost, unable to realize industrialized production
In addition, this patent does not conduct research on the relevant components of chromite suitable for calcium-free roasting, and fails to solve the special requirements of calcium-free roasting process for chromite in industrial production
The problem of how the fuel used in calcium-free roasting can not only meet the process requirements, but also minimize the production cost has not been resolved.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Process for producing sodium chromate by calcium-free calcination

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0011] Example 1: Chromite (Cr 2 o 3 = 45 ± 1%) grinding to 200 mesh and passing 98%, soda ash crushing to 80 mesh passing 90%, calcium-free slag sorting and grinding to 100 mesh passing 98%. The three materials are mixed evenly, and the material ratio is chromite: soda ash: chromium slag=26:21:53 (weight ratio). The powder is roasted in the rotary kiln, the reaction temperature is 1130 degrees, and the temperature of the flue gas at the kiln tail is 610 degrees. The material stays in the rotary kiln for 4 hours and 10 minutes, and the high temperature zone stays for 60 minutes. The material does not segregate and does not form a wall. The clinker chromium oxidation rate is 93%. After leaching and filtering, the chromium slag does not contain calcium chromate, and the leaching rate of hexavalent chromium is greater than 99.1%. After the chromium slag is sorted, 74% of the coarse slag is returned as filler, and the remaining chromium slag is detoxified and discharged for sto...

example 2

[0012] Example two: raw material is the same as example 1, chromite: soda ash: chromium slag=25: 20: 55, the powder is roasted in the rotary kiln, the reaction temperature is 1080 degrees, the flue gas temperature at the kiln tail is 590 degrees, and the residence time of the material is in the rotary kiln 4 hours, in which the residence time in the high temperature zone is 65 minutes, the material does not form a wall, the clinker chromium oxidation rate is 94%, and the hexavalent chromium leaching rate is greater than 99.4%.

example 3

[0013] Example three: the raw material is the same as example 1, the batching is the same as example 2, the reaction temperature is 1070 degrees, the kiln tail flue gas temperature is 630 degrees, the material residence time is 4 hours, and the high temperature zone residence time is 60 minutes. The material does not segregate, does not form a wall, the clinker chromium oxidation rate is 93%, and the hexavalent chromium leaching rate is greater than 99.2%.

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

No PUM Login to view more

Abstract

The invention relates to a method to manufacture sodium chromate. It adopts non- calcium roasting technics to realize industrialized production. With chromite, soda and chrome dregs without calcium as charging after mixing evenly, coal dust as fuel, the steps are as follows: coal injection baking in burner, leaching clinker, gravity sorting chrome dregs without calcium and recycling useful dregs as filling. It is the first time that fillings are composed with iron ore, chromite and soda after baking. With shortening technics route and reducing equipment investment, the invention can reduce production cost. Without segregation and adhibiting wall, roasting heat is easy to control.

Description

technical field [0001] The invention relates to a method for producing sodium chromate, in particular to a process for industrialized production of sodium chromate by adopting a calcium-free roasting process. Background technique [0002] Today's production of sodium chromate clinker is roasted with calcium filler (limestone and dolomite) mixed with chromite, soda ash and a small amount of calcium-chromium slag (calcium process for short). This process produces a large amount of sodium chromate slag (2.5-3 tons of slag / ton of product), and the chromium slag contains water-insoluble calcium chromate (a carcinogen recognized by the international health community), and the chromium slag discharged contains hexavalent chromium Up to 2-3% (calculated as chromium trioxide). The hexavalent chromium in a large amount of chromium slag is difficult to detoxify, and the chemical components of calcium chromium slag are not suitable for comprehensive utilization, c...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Application Information

Patent Timeline
no application Login to view more
Patent Type & Authority Applications(China)
IPC IPC(8): C01G37/14
Inventor 韩登仑张忠元李元魁杨海何喜善邓珍兰张红军杨昆山
Owner TIANJIN CHEM RES & DESIGN INST
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products

Browse by: Latest US Patents, China's latest patents, Technical Efficacy Thesaurus, Application Domain, Technology Topic.

© 2024 PatSnap. All rights reserved.Legal|Privacy policy|Modern Slavery Act Transparency Statement|Sitemap