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Techniques for production of chlorated products and prefabricated cathode structures

A technology of chlorination products and cathodes, applied in the direction of electrodes, electrolytic coatings, coatings, etc.

Inactive Publication Date: 2015-11-18
HYDRO QUEBEC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When iron impurities are also present in the electrolyte, a large number of anions such as PO 4 -3 The addition of

Method used

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  • Techniques for production of chlorated products and prefabricated cathode structures
  • Techniques for production of chlorated products and prefabricated cathode structures
  • Techniques for production of chlorated products and prefabricated cathode structures

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0156] The beneficial effect of the addition of very small amounts of phosphate additives on the cathode was observed in the following experiments.

[0157] will contain 550g / l NaClO 3 A bath of 350 liters of sodium chlorate electrolyte, 110 g / l of NaCl and 3 g / l of dichromate was used for electrolysis. The pH and temperature were maintained at 6.5 and 70°C, respectively. Steel cathodes and DSA anodes were used in the experiments. at 2.5kA / m 2 After 74 hours of continuous electrolysis, the cell voltage was 3.056 volts. Then with CaCl 2 Form added 4ppm calcium impurity to the electrolyte and in only 1 hour, the voltage rose to 3.074, which means a rise of 18mV. A 15 minute shutdown event without cathodic protection (ie, open circuit - OC) was performed to cause some corrosion of the cathode and generation of iron impurities in the electrolyte and after 22 hours of continuous electrolysis, the voltage reached 3.060 volts. This voltage is close to the original value, which ...

Embodiment 2

[0168] Figure 6 Shown in addition to using stainless steel cathodes with figure 2 Electrochemical experiments similar to those shown in . specifically, Figure 6 Shown at 70°C and 2.5kA / m with 400 series stainless steel cathode and DSA anode 2 A series of shutdowns in the chlorate electrolyzer under operation. Observations were made for current interruptions in the form of open circuit (OC) for 2, 5, 10 and 15 minutes followed by interruptions in the form of short circuit (CC) for 15 minutes. if possible by passing Figure 6 and figure 2 As can be seen by comparison, the cell with the stainless steel cathode has a potential 190 mV higher than that of the iron cell (4.42 - 4.23 volts). As mentioned before, this is due to the presence of chromium in the stainless steel alloy. Background O 2 Release was also slightly higher by 0.4% (3.1% vs. 2.7%). Surprisingly, however, the cathodic current efficiency of the stainless steel cathode was much higher and remained high e...

Embodiment 3

[0176] Figure 8 Shown are two scanning electron micrographs taken from a cross section of a cathode structure comprising a 400 series stainless steel substrate, a catalytic intermediate layer and a thin hydroxyapatite top layer. Note that a tungsten coating was provided on top of the sample prior to electron microscopy to protect the sample during processing.

[0177] Figure 9 A chemical map showing a layer of hydroxyapatite, which indicates the presence of calcium and phosphorus elements.

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Abstract

Techniques for producing chlorinated products include an electrochemical process that includes the steps of providing an anode and a cathode in an electrolyte comprising impurities such as calcium ions, applying a voltage between the anode and the cathode under conditions to form an electrolysis product such as sodium chlorate in the electrolyte, and providing sufficient phosphate ions to form with at least a portion of the calcium ions a protective external layer including a calcium phosphate compound such as hydroxyapatite on the cathode, while preferably avoiding other phosphate precipitations. A pre-determined amount of phosphate ions may be added, for example, based on the surface area of the cathode in order to form the protective layer. Related uses and systems are also described. Prefabricated cathodes may include a substrate, a catalytic intermediate layer and a calcium phosphate protective layer.

Description

technical field [0001] The present invention relates generally to the field of manufacture of chlorination products, and more particularly to cathodic protection techniques and prefabricated cathodic structures in the manufacture of sodium chlorate. Background technique [0002] Sodium chlorate (NaClO 3 ) can be manufactured commercially by an electrochemical process according to the following overall reaction: [0003] NaCl+3H 2 O=>NaClO 3 +3H 2 (1) [0004] Hydrogen evolution occurs on the cathode side as follows (H 2 ): [0005] 2H 2 O+2e - =>2OH - +H 2 (2) [0006] And on the anode side through a series of reactions to form chlorate (ClO 3 - ): [0007] 2Cl - =>Cl 2 +2e - [0008] Cl 2 +H 2 O=>HClO+Cl - +H + [0009] HClO=>ClO - +H + [0010] 2HClO+ClO - =>ClO 3 - +2Cl - +2H + (3) [0011] On the cathode side, the hydrogen current efficiency (CE) is defined as the hydrogen flow rate (J H2 ) and the ratio between the tota...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25B11/04C25B1/26C25B15/08C25B9/17
CPCC25B1/26C25B11/04C25B15/08C25D9/10C25B1/265C25B15/02C25B11/075C25B9/17C25B11/051C25B11/061
Inventor R.舒尔茨
Owner HYDRO QUEBEC CORP