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Reducing agent for the soluble chromate content of cement and methods for the production thereof

A manufacturing method and reducing agent technology, applied in chemical instruments and methods, iron sulfate, sulfur trioxide/sulfuric acid, etc., can solve the problems of unlikely use and residue, and achieve the effect of saving energy

Inactive Publication Date: 2006-08-23
克尔－麦吉染料股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, there are also cited disadvantages: when isolating ferrous sulfate heptahydrate, other metal sulfates will remain in the dilute acid and it is unlikely to use green salt
[0009] EP 160747A1 describes that the chromate reducing effect of ferrous sulphate mixed in cement decreases over time during storage

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0086] Manufacture and characteristics of the reducing agent containing ferrous sulfate

[0087] The dilute acid (23.5% sulfuric acid, 3.8% iron) obtained during the kraft manufacture of titanium dioxide is concentrated by evaporation in a three-stage forced circulation evaporation system with increasing vacuum until The sulfuric acid content reaches 48% (this content corresponds to a sulfuric acid concentration of 70% in the liquid phase). During concentration by evaporation, most of the ferrous sulfate crystallizes out as the monohydrate. After concentration by evaporation, the resulting slurry was aged, whereby its temperature was lowered from about 90°C to 60°C in a stirring cascade. The slurry was then filtered under pressure in a ceramic cartridge filtration system, and compressed air was used to partially remove the attached sulfuric acid from the filter cake. A brittle, dry, easily handled filter cake (filter salt) is obtained which can be used as a reducing agent co...

Embodiment 2a

[0091] In each case, 200 g of filter salt having a free sulfuric acid content of 25.3% were slurried by mixing hot dilute acid at 60° C. on a preheated suction filter, and the hot suspension was quickly sucked dry. In contrast to the washing with cold dilute sulfuric acid, non-thixotropic, free-flowing filter salts were obtained in all cases.

[0092] Test No.

Embodiment 2b

[0094] Washing was performed in the same manner as in Example 2a) and Test 3. Then by mixing in 10 wt% CaCO 3 to neutralize residual acid in the filtered salt.

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PUM

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Abstract

The invention relates to a reducing agent for the soluble chromate content of cement and to methods for the production thereof, which comprise concentrating an used sulfuric acid, containing iron(II) sulfate, and separating the sulfuric acid from the obtained precipitate which contains iron(II) sulfate.

Description

technical field [0001] The present invention relates to a reducing agent for reducing the content of soluble chromate in cement and its production method. Background technique [0002] The chromate content in cement usually ranges from 20 ppm to 100 ppm, depending on the main components of the raw materials used. The chromium contained in cement can dissolve in the form of tetravalent chromium (IV) when mixed with water, and if it is frequently exposed, it can sensitize the skin and cause a chromium allergic reaction, which is the so-called contact dermatitis that masons suffer from. To prevent chromium allergic reactions, chemical reduction of tetravalent chromium to trivalent chromium is considered, thereby greatly reducing solubility. Ferrous(II) sulfate (in the form of heptahydrate or monohydrate) is mainly used in the cement industry as a reducing agent so that the tetravalent chromium content is below 2ppm (ref: Locher, Friedrich Wilhelm: Zement: Grundlagen der Herste...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B22/14C04B28/02C01G49/14C01B17/90C01G23/053C22B7/04
CPCC04B28/02C04B2111/1081C01B17/901C01G49/14C04B22/149C01P2004/62C01G23/0532C22B7/04C01P2004/61Y02P10/20C04B22/142C01B17/90C04B22/14C01B17/88
Inventor 迈克尔·福斯辛格哈德·奥尔本诺·劳巴克德特勒夫·克莱因沃纳·舒伊克劳斯·克利施欧文·韦斯沃纳·巴尔菲利普·里斯
Owner 克尔－麦吉染料股份有限公司
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