RU2258100C1 - Electrolyzer for production of sodium hypochlorite - Google Patents

Abstract

FIELD: chemical technology; technology of electrochemical synthesis of sodium hypochlorite.

SUBSTANCE: proposed electrolyzer includes rectangular bath and lower and upper hermetic covers provided with inlet and outlet pipe unions, respectively. Electrode unit is mounted in bath between covers, thus forming inlet and outlet chambers; electrodes connected in bipolar manner are separated from each other by means of porous membranes of similar height in such way that ratio of "cathode-membrane" and "membrane-cathode" distances is selected from row of 0.1-1.0. Electrode unit is mounted in bath for vertical motion between covers for setting the required volume of chambers in accordance with starting characteristics of sodium chloride solution and electrolyzer mode.

EFFECT: enhanced efficiency.

2 cl, 1 dwg

Description

The invention relates to chemical technology, in particular to a technology for the electrochemical synthesis of sodium hypochlorite.

A filter-press type electrolyzer for producing sodium hydroxide is known, comprising alternating anode, cathode and non-conductive cushioning plates and ion-exchange membranes placed between the anode and cathode plates to form anode and cathode chambers, and holes are made in all of these plates, forming longitudinal electrically during assembly isolated channels in communication with the anode and cathode chambers for supplying electrolyte to them and removal of electrolysis products. An increase in the current output of the product was achieved in it by the fact that in all of these plates additional holes were made, forming longitudinal electrically isolated channels during assembly, each communicating only with the anode or only with the cathode chambers below the electrolyte level in them [1].

The electrolyzer has a rather complicated design, is characterized by increased costs during maintenance and repair, and cannot be used to produce sodium hypochlorite.

Known electrolyzer to obtain sodium hypochlorite, containing a rectangular bath with vertical flat-parallel electrodes located in it, turned on bipolar [2].

The electrolyzer is characterized by a reduced current output due to a significant degree of electrolytic dissociation of this salt, leading to the appearance of a free hypochlorite ion in solution, which is capable of further anodic oxidation, as well as reduction at the cathode.

Known electrolyzer for separation of ions, containing a rectangular bath and located at opposite ends of the bath electrodes in ionite covers. Ensuring the continuity of the process and accelerating the separation in the electrolytic cell is achieved by the fact that it is equipped with two chambers made to rotate around a vertical axis and located between the electrodes, while the chamber walls facing the electrodes are made of ion-exchange membranes permeable to shared ions, and each chamber equipped with two electrodes located at these membranes [3]. The cell is closest to the invention in terms of essential features and adopted as a prototype.

The electrolyzer in the design is a complex stationary laboratory-industrial equipment and, like the electrolyzer according to [1], is characterized by increased costs during maintenance and repair, while placing the chambers in the interelectrode space of the bath excludes the possibility of using it to produce sodium hypochlorite.

The objective of the invention is to create an electrolytic cell with a two-chamber rectangular bath to obtain sodium hypochlorite, in which an increased current output of the product would be combined with high mobility of the electrolyzer, its small size and weight, as well as the ease of maintenance and repair during operation, for example, in field conditions on silage blanks.

The problem is solved in that in the electrolytic cell for producing sodium hypochlorite, containing a rectangular bath with two chambers, vertical plane-parallel electrodes located in the bath, included bipolar and separated by membranes, according to the invention, the lower and upper parts of the bath are equipped with hermetic covers with nozzles designed respectively for the input of the initial solution of sodium chloride and the output of the sodium hypochlorite solution, the electrodes are separated by porous membranes having the same height, so that the cathode – membrane and membrane – anode distances are selected from the range 0.1–1.0, and the inlet and outlet chambers of the electrolyzer are respectively formed between the bath lids and the lower and upper edges of the electrodes and membranes. It is advisable to install the electrode block with the possibility of movement in a vertical plane between the lids of the bath.

When using the invention, a technical result can be obtained, which is expressed in obtaining a sodium hypochlorite solution with a high current efficiency during flow operation of the electrolyzer, while the design of the electrolyzer is simple and high maintainability, which allows the use of the electrolyzer in the field, for example, to obtain large quantities hypochlorite solution as a preservative in the process of harvesting silage.

The electrolyzer for producing sodium hypochlorite in the drawing contains a rectangular bath 1 with sealed covers 2 and 3, equipped respectively with an inlet fitting 4 and an outlet fitting 5, an electrode unit 6 with vertical plane-parallel electrodes 7 _1-n , which are bipolar and separated from each other having porous membranes 8 having the same height, so that the ratio of the cathode – membrane 9 and membrane – anode 10 distances is selected from a range of 0.1-1.0. The block of electrodes 6 in the cavity of the bath 1 is installed between the covers 2 and 3 with the formation of the inlet chamber 11 under the lower edges of the electrodes and membranes, as well as the output chamber 12 - above the upper edges of the electrodes and membranes. In this case, the electrode block 6 has the ability to move in a vertical plane between the covers 2 and 3 to set the volumes of the chambers 11 and 12 in accordance with the characteristics of the initial solution of sodium chloride and electrolysis mode.

The cell operates as follows. The initial solution is fed into the bath 1 through the nozzle 4 in the lower cover 2, while in the lower chamber 11 under the electrode block 6 the pressure of the solution jet weakens, as a result, the flow rate of the solution through all the electrode spaces 9 and 10 is the same, which makes it possible to maintain the optimal electrolysis mode in them. In this case, on the anode surface of the electrode 7 ₁ , the chlorine ion is oxidized to elemental chlorine. Interacting with water, elemental chlorine forms hypochlorous acid in the anolyte space in the anode space 10. On the cathode surface of the electrode 7 ₂ in the near-cathode space 9, hydrogen is reduced and in the catholyte in the near-cathode space 9, sodium hydroxide is accumulated. The flow mode of electrolysis in the electrolyzer reduces the possibility of strong heating of the solution due to the heating action of the electric current and provides the possibility of conducting an intensive electrolysis mode at high current densities without reducing the current efficiency. Moreover, the volume of the anode space 10 is larger than the cathode space 9 due to the asymmetric arrangement of the diaphragm 8, which provides an additional opportunity to exclude heating of the anolyte, in which acceleration of the decomposition of the hypochlorite ion is possible [4]. In addition, the presence of the diaphragm 8 leads to the fact that the hypochlorite ion in the anode space 10 is connected in the form of poorly dissociated hypochlorous acid and is not subjected to further oxidation at the anode 7 ₁ . The electrolysis products after leaving the electrode spaces are mixed in the upper chamber 12, where the chemical process of the formation of sodium hypochlorite occurs during the interaction of hypochlorous acid contained in the anolyte with sodium hydroxide from catholyte. The obtained target product — sodium hypochlorite — leaves the cell through the nozzle 5 in the top cover 3. The possibility of moving the electrode block 6 between the chambers allows in each case to set the volume of the chamber 12 in accordance with the composition of the solution and the electrolysis mode.

The proposed electrolyzer has an advantage in comparison with other designs, because it is characterized by the maximum simplicity of the design, containing only two electrical contacts with current leads 13 and 14, has maximum maintainability and allows to obtain large volumes of sodium hypochlorite solution in a short time. The electrolyzer can be used for the needs of agricultural production, for example, in feed preparation during the laying of silage, in the processing of livestock products, and in the disinfection of large facilities and large rooms. It can be used in oil production for disinfection of produced water, for disinfection of terrain, and in other sectors of the national economy.

Sources of information

1. USSR author's certificate No. 1662353, cl. With 25 V 9/00, publ. 07/07/91, Bull. Number 25.

2. N.P. Fedotiev et al. Applied Electrochemistry, L., Chemistry, 1967, p. 422-423.

3. Copyright certificate of the USSR No. 1333716, cl. With 25 V 9/00, publ. 08.30.87, Bull. No. 32 is a prototype.

4. N.P. Fedotiev et al. Applied Electrochemistry, L., Chemistry, 1967, p. 423.

Claims (2)

1. An electrolyzer for producing sodium hypochlorite, comprising a rectangular bath with two chambers, vertical plane-parallel electrodes located in the bath, switched on bipolar and separated by membranes, characterized in that the lower and upper parts of the bath are equipped with sealed covers with nozzles designed respectively for the inlet of the initial chloride solution sodium and sodium hypochlorite solution, and the electrodes are separated by porous membranes having the same height so that the ratio of the cathode-meme distances the brane and the anode membrane are selected from the range 0.1-1.0, and the inlet and outlet chambers of the electrolyzer are respectively formed between the bath covers and the lower and upper edges of the electrodes and membranes. 2. The electrolyzer according to claim 1, characterized in that the electrode unit is mounted to move in a vertical plane between the lids of the bath.