Method of producing chlorine, caustic soda and hydrogen. RU patent 2509829.

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing chlorine, an alkali metal hydroxide and hydrogen, and a computer-controlled device for carrying out the disclosed method, wherein the method includes the following steps: (a) preparing brine by dissolving an alkali metal chloride source in water; (b) removing the alkaline precipitate from the brine obtained at step (a) in the presence of hydrogen peroxide or in the presence of at most 5 mg/l active chlorine using an activated carbon filter and obtaining ready brine; (c) treating at least a portion of the ready brine obtained at step (b) at an ion-exchange step; (d) treating at least a portion of brine obtained at step (c) at an electrolysis step; (e) separating at least a portion of chlorine, alkali metal hydroxide, hydrogen and brine obtained at step (d); (f) treating at least a portion of brine obtained at step (e) at a dechlorination step, carried out in the presence of hydrogen peroxide; and (g) recycling at least a portion of the dechlorinated brine obtained at step (f) to step (a).

EFFECT: cost-effective method of producing chlorine which is automated to such an extent that it is suitable for remote control and requires minimal immediate attention and maintenance.

11 cl, 1 dwg

The present invention relates to a method for producing chlorine, alkali metal hydroxide and hydrogen and device for implementing this method.

The production of chlorine itself is well studied. Chlorine can be produced by electrolysis of sodium chloride solution (brine), as byproducts sodium hydroxide and hydrogen. In another known way chlorine produced by electrolysis of a solution of potassium chloride, as byproducts caustic potash (potassium hydroxide) and hydrogen. Such ways of chlorine production is usually carried out at facilities of large-scale production of chlorine; they are characterized by the shortcomings, which include a large number of process stages, the use of a large number of pieces of equipment, the need for more attention to management personnel and frequent maintenance. In this regard it is noted that a typical installation of large-scale production of chlorine consists of separate blocks for the storage and manipulation of salt; for production and processing in brine; many stages of removal from the brine alkaline precipitation; many concurrent electrolytic cells; stages cooling and drying chlorine; stages of compression and liquefaction of chlorine; storage, shipment and distribution liquid chlorine; overload, evaporation, storage, shipment and distribution of alkali metal hydroxide; and handling, overload, compression, storage, shipment and distribution of hydrogen.

For example, the patent US 4190505 relates to a method of electrolysis of sodium chloride, containing a complex of iron cyanide, electrolytic cell, separated on the anode and cathode cation-exchange membrane, and the use of sodium chloride, containing a complex of iron cyanide, as source material. The complex iron cyanide removed through the stage of oxidative decomposition, which can be used by any oxidising agent, well-known in this field, including, for example, chlorine, sodium hypochlorite, hydrogen peroxide, sodium chlorate, potassium chromate and potassium permanganate. Chlorine and/or sodium hypochlorite is the most preferred. This patent describes typical technological scheme of the device, including electrolytic cell cathodic chamber and a tank of Catolica, where a water solution of caustic soda circulates between a specified cathodic chamber and a tank of Catolica. In the specified tank Catolica catholyte are divided into water solution of caustic soda and hydrogen. The anolyte circulates between the anode chamber and a tank of anolyte. Chlorine gas, separated from anolyte, assign, aqueous solution of sodium chloride reduced concentration sent to the tower of obesjajusee. To dilute aqueous solution of sodium chloride, taken from the tower of obesjajusee, introduce additional water. Specified diluted solution is then applied to the dissolving tank of sodium chloride. Saturated aqueous solution of sodium chloride warm up, flowing through the heat exchanger, and additionally heated by steam in the tank oxidative decomposition up to 60 degrees or higher. After cooling the solution is sent to the reaction tank, where they perform the processing additives such as sodium carbonate, caustic soda, etc. The treated solution then passes through a filter and a tower with chelating resin, where the removal of ions of calcium, magnesium ions, iron ions or other remaining dissolved in an aqueous solution of sodium chloride compounds and reduce their content to 0.1 ppm. Thus purified, essentially, saturated aqueous solution of sodium chloride served in the tank for anolyte.

Method and device corresponding to US 4190505, are an example of the method and devices, characterized by complexity and demands of a large number of pieces of equipment. Therefore, you need great attention to the management staff and frequent maintenance. In addition to the complexity of such methods of large-scale production noted that a significant part of the produced chlorine must be transported by pipeline, by rail or by truck. Currently such transportation by rail or road is discussed from the point of view of the relevant safety and security. That is clearly a demand for small installations for the production of chlorine, suitable for the production of chlorine for use on site. In this regard, noted that existing installations for small-scale production of chlorine are small installations for the production of chlorine-based mercury, which are subject to conversion or closure in the foreseeable future due to related threats to health and the environment.

Ordinary methods of production of chlorine by membrane electrolysis, usually undertaken at facilities for large-scale production of chlorine (the production of about 100,000 to 200,000 tons chlorine per year), can theoretically be applied on a small scale only, to satisfy local demand. However, as just indicated, such methods involve using a large number of pieces of equipment, necessity of close attention of the management personnel and frequent maintenance. Therefore, if, for example, in the year to produce only about 5000-20000 tons of chlorine, it is difficult to implement such a cost-effective way.

Therefore, the present invention is to provide a method of production of chlorine, which is economically feasible in the exercise for light-duty, preferably located at the place of consumption, installation for the production of chlorine. Another object of the present invention is to provide a device for implementing the method corresponding to the present invention, the automated to the extent that it is suitable for remote control and requires minimal immediate attention and support. Suddenly it was discovered that the first task can be solved by using a particular sequence of technological stages which constitute a simple process that is suitable for implementation by remote control. Therefore, the present invention relates to a method of production chlorine, alkali metal hydroxide and hydrogen, which is the method includes the following stages:

(a) preparation of brine by dissolving source chloride alkali metal in water;

(b) removing from the brine obtained at the stage of (a), alkaline residue in the presence of hydrogen peroxide in the presence of at most 5 mg/l active chlorine through a filter made of activated carbon and getting ready brine;

(C) processing is at least part of ready brine obtained at the stage of (b), at the stage of ion exchange;

(d) treatment for at least part of the solution obtained at the stage of (C) stage of electrolysis;

(e) allocation of at least part of chlorine, alkali metal hydroxide, hydrogen and brine obtained at the stage of (d);

(f) processing at least part of the solution obtained at the stage of (d), at the stage of obesjajusee carried out in the presence of hydrogen peroxide; and

(g) recycling at least part obezhirennogo brine obtained at the stage (f), to the stage of (a).

Advantages of the method of the present invention is that it provides an adequate solution to the problem of transportation and does not require the use of mercury, at the same time provides fewer process steps, fewer pieces of equipment, lower pressure, less attention from managers and less maintenance compared to conventional methods of production of chlorine. Thus, thanks to the present invention, the resulting method is effective chlorine production, cost-effective even when on a small scale. Therefore, the present invention represents a significant improvement relative to the known methods of production of chlorine. Preferably, chloride alkaline metal is sodium chloride or potassium chloride. Preferably, chloride alkaline metal is sodium chloride.

Brine obtained at the stage of (a), preferably, contains at least 200 g/l of chloride alkali metal. More preferably, brine contains 300 to 310 g/l chloride alkaline metal, it is most preferable, brine is a saturated solution of chloride of alkaline metal. Stage (a) properly can be carried out at a temperature of at most 80 degrees C. On the other hand, the temperature at the stage of (a) properly can be at least room temperature. Preferably, the stage of (a) carried out at a temperature in the range from 20 to 80 degrees C. In General, the stage of (a) performed at atmospheric pressure, although there may be applied a higher pressure, as clearly specialists in this field. It is noted that the source of chloride of alkaline metal, preferably pick up so that it was not necessary in the treatment of brine, prepared at the stage of (a) on the normal brine purification stages, as described in US 4242185, before being sent to the step (b). In other words, in this the invention, preferably, there is no stage of purification of the brine, which brine mixed with commonly used substances to clean brine, such as, for example, phosphoric acid, carbonates of alkaline metals, bicarbonate of alkali metals, alkaline phosphates metals, acid alkaline phosphates metals or their compounds.

The temperature at the stage of (b) properly can be at most 80 degrees C. on the other hand, the temperature may reach at least 20 degrees C. Preferably, the stage of (b) is carried out at a temperature in the range from 20 to 80 degrees C. The pressure at the stage of (b) properly is at least 2 bar abs., preferably at least 4 bar abs. On the other hand, the pressure on the stage of (b) properly is at most 10 bar abs., preferably, at most 6 bar abs. The pressure at the stage of (b), preferably, with a range from 2 to 10 bar abs., preferably, the range of 4 to 8 bar abs. At the stage of (b) alkaline residue is removed from the brine obtained at the stage of (a), in the presence of hydrogen peroxide in the presence of at most 5 mg/l active chlorine using the filter activated carbon, resulting solution emit. In accordance with the present invention, the number of ions of alkaline metals can be significantly reduced relative to their number in brine obtained at the stage of (a). In such an alkaline residue includes, for example, the iron hydroxide, aluminum hydroxide, magnesium hydroxide and other metal hydroxides. The number of Fe 3+ , present in brine, at the stage of (b) may be reduced to the number in the range from 10 to 200 mcg/l, while the number of Mg 2+ , present in brine, at the stage of (b) may be reduced to the number in the range from 300 to 1000 mg/L. At the stage of (b) the filter is activated charcoal may also be used for chemical decomposition and/or removal of traces of hydrogen peroxide and/or to remove traces of chlorine, still present in brine after stage (f). Thus, ion exchange resin, used at the stage of (C), may be appropriately secured. In this respect, it is observed that in the known methods such trace amounts can be removed by using a sequence of two conventional filters, for example, related to the filters upstream type or membrane type. Carbon filters are sometimes used in the methods of production of chlorine. For example, in the US 4242185 described that activated charcoal or activated charcoal can be used for decomposition of residual chlorine in the recirculated flow depleted brine. But suddenly it was found that when used in accordance with the present invention carbon filter also reduces the number of ions of alkaline metals on the number in brine obtained at the stage of (a).

Accordingly, any filter activated carbon can be used in accordance with the present invention. Preferably used activated carbon can be a granular activated carbon-based washed acid fossil coal or activated coal with high catalytic activity, to ensure that hydrogen peroxide and any optional active chlorine will be completely destroyed and will not be able to influence the ion-exchange resin used on stage (s). Accordingly, the number of brine, which can be passed through the filter for an hour, lies in the range from 1 to 30 volumes filter/hour, preferably in the range from 8 to 15 volumes filter/hour.

It is noted that the stage of physical obesjajusee (for example, using towers obesjajusee) may not be used in the method of the present invention.

At the stage of (C) carry out ion exchange treatment to reduce the amount of alkaline earth metals present in brine, to the range of parts per billion. The number of ions M 2+ (M=metal), such as ions of Ca 2+ and Mg 2+ , can be reduced to values in the range from 0 to 20 parts per billion, while the number of strontium ions can be reduced to less than 50 ppb. Accordingly, at the stage of ion exchange use two or more of ion-exchange columns, which ion-exchange columns can be used alternately. In these columns can be used known ion-exchange resins, preferably, ion exchange chelating resins such as, for example, lewatitž TP208 or Abmerlite® IRC748. Accordingly, the number of brine, which can be passed through each of the ion exchange columns, lies in the range from 10 to 40 volumes column/h, preferably 15 to 30 volumes of the column/h. The temperature on stage (s) properly can be at most 80 degrees C. On the other hand, stage (s) properly can be carried out at a temperature of at least 20 degrees C. Preferably stage (s) carried out at a temperature in the range from 20 to 80 degrees C. Stage (s) properly can be conducted at a pressure of at most 8 bar abs., preferably, at most 5 bar abs., preferably, at most, 3,5 bar abs. On the other hand, stage (s) properly can be conducted at a pressure of at least 1 bar abs., preferably at least 2.5 bar abs. Preferably, the stage (C) is carried out at a pressure in the range from 1 to 5 bar abs., more preferably, in the range from 2.5 to 3.5 bar abs.

On stage (d)at least part of the solution obtained at the stage of (C), processed at the stage of electrolysis, at what stage are formed chlorine, alkali metal hydroxide and hydrogen. Transport the brine from the stage (a) to the point (d) can be successfully implemented only one pump. Between the stage and the stage (d) in brine obtained at the stage (s), preferably add hydrochloric acid. Stage membrane electrolysis in accordance with the present invention properly carried out using only one cell instead of two or more cells, as in the case of conventional methods of production of chlorine. The cell stage (d) can be any type of electrolyzer, which are usually used at the stage of membrane electrolysis. For example, suitable electrolyzer described in ER(A1). Stage (d) duly carried out at a temperature, at most 95 C, preferably, at most 90°C. on the other hand, the stage (d) duly carried out at a temperature at least 50 C, preferably at least 85 degrees C. Preferably, the stage (d) carried out at a temperature in the range from 50 to 95 C, preferably at a temperature in the range of 80 to 90 degrees C. Stage (d) duly executed under the pressure of at most 2 bar abs., preferably, at most 1.5 bar abs. On the other hand, the stage (d) duly executed under the pressure of at least 1 bar abs. Preferably, the stage (d) duly carried out at a pressure in the range from 1 to 2 bar abs., preferably, at a pressure in the range of 1.0 to 1.5 bar abs.

On stage (e) method of the present invention, at least, part of chlorine, alkali metal hydroxide, hydrogen and brine after stage (d) allocate. Preferably, most of the chlorine, alkali metal hydroxide, hydrogen and brine after stage (d) allocate on stage (e). To this end, the setting for electrolysis is used at the stage of (d)must have an outlet for chlorine, outlet for alkali metal hydroxide, outlet for hydrogen and outlet brine.

Stage (f) duly carried out at a temperature, at most, 95 C, preferably, at most 90°C. on the other hand, the stage (f) duly carried out at a temperature at least 50 C, preferably at least 85 degrees C. Preferably, the stage (f) carried out at a temperature in the range from 50 to 95 C, preferably at a temperature in the range from 85 to 90 degrees C. Stage (f) duly executed under the pressure, at most, 3-6 bar abs., preferably, at most 2.5 bar abs. On the other hand, the stage (f) duly executed under the pressure of at least 1 bar abs., preferably at least 1.2 bar abs. Preferably, the stage (f) carry out at a pressure in the range from 1 to 3 bar abs., preferably, at a pressure in the range of 1.2 to 2.5 bar abs.

The method of the present invention, at least, part obezhirennogo brine obtained at the stage (f), at the stage of (g) recycle at the stage of (a). Preferably, more than 50% obezhirennogo brine obtained at the stage (f), at the stage of (g) recycle at the stage of (a). Preferably, all obeschannyj brine obtained at the stage (f), at the stage of (g) recycle at the stage of (a).

In a preferred embodiment of the present invention of the hydrogen peroxide is used at the stage of obesjajusee in such quantity that the brine, recycled on stage (g)contains at most 5 mg of hydrogen peroxide per litre specified brine, preferably, at most, 3 mg of hydrogen peroxide per litre specified brine, it is most preferable, at most, 1 mg of hydrogen peroxide per litre specified brine. In another preferred embodiment, the implementation of the present invention of the hydrogen peroxide is used at the stage of obesjajusee in such quantity that the brine, recycled on stage (g)contains at most 5 mg of chlorine per litre specified brine, preferably, at most, 3 mg of chlorine per litre the specified brine, it is most preferable, at most, 1 mg of chlorine per litre specified brine (the content of active chlorine reflects the total concentration of chlorine containing oxidizers present in the solution).

The main advantage of the method of the present invention is that it can be carried out using a remote control that allows to considerably reduce the time and attention of the governing personnel. Consequently, this way, preferably, carry out using the remote control. In addition, this method is suitable for implementation on a small scale. Therefore, this method is usually carried out on the installation of small-scale production of chlorine maximum performance 3000-20000 metric tons chlorine per year, preferably, 10000-17000 metric tons chlorine per year.

Suddenly it was discovered that the second objective of the invention is solved by using a special device with a remote control.

Therefore, the present invention also refers to a managed using the computer device for implementing the method corresponding to the present invention, which includes the reservoir (2) for the source of chloride alkali metal; filter element (7), adjoining with the tank; ion exchange the item (9), reported with filter element; an electrolytic cell (11)which is connected with ion-exchange element, in which the electrolytic element has the outlet to chlorine (12), the outlet for alkali metal hydroxide (14), the outlet for hydrogen (13) and outlet brine (15); the first pump (5) to transport the brine from the tank in an electrolytic cell; optional second pump (18) for transportation obezhirennogo brine from electrolytic cell in the tank; one or more of these items have one or more sensor to monitor one or more parameters of the process, such as temperature, pressure, voltage or current, which sensors connected to one or more first computer, which is the first computer connected to one or more second the PC in the control center via a data network like the control center removed from the electrolytic cell. The first computer(s) is(are) a computer(s) (e) perform(comply) with the management and security devices. Preferably, the first computer(s) is(s) in the immediate vicinity of the cell, that is where the device. Specified the second machine(s), producing(e) the observation and analysis of the process parameters, and manage the implementation of the method of the present invention, preferably, with the participation of one or more qualified operator of devices for production of chlorine, is located(s) in the control center, the remote device. The control center can be removed from the device (that is, the installation of the electrolysis), but still is on the same production site, as the device itself. However, in a preferred embodiment of the invention control center is on another site, which may be located in the same country, but also may be in another country or even another continent. Preferably, the control center is located on an industrial platform of a large traditional installation of electrolysis. Thus, the installation is under the supervision and control of qualified operators chlorine, thereby ensuring uninterrupted and reliable supply of chlorine where he was needed. The data network through which it is connected first and second computers, for example, can be the Internet. Alternatively, the data network can be an extranet or intranet.

These sensors specified elements (i.e. the filter element, ion element and/or specified electrolytic cell) are part of the surveillance system, commonly used in the field of control work of the electrolytic installations. Suitable observation system, for example, is described in US 6591199.

The reservoir (2) and/or the cell (11), preferably equipped with at least one auto focus camera and equipment for measurement of density for monitoring the implementation stage. Specified(s) auto focus camera(s) and apparatus for measuring density, preferably, also connected with a first computer(s) goes through the data network, connected with the specified second computer(s) of the control center. The device with the computer controlling the implementation the method corresponding to the present invention, preferably, is an installation of small-scale production of chlorine with maximum performance 3000-20000 metric tons chlorine per year, more preferably, 10000-17000 metric tons chlorine per year. The specified device, preferably, is so compact as possible. It is noted that in device corresponding to the present invention, it is most preferable, missing element for physical obesjajusee (for example, the tower of obesjajusee).

Figure 1 illustrates the implementation of the method of the present invention.

1. Method of production of chlorine, alkali metal hydroxide and hydrogen, which is the method includes the following stages: (a) preparation of brine by dissolving source chloride alkali metal in water; (b) removing from the brine obtained at the stage of (a), alkaline residues in the presence of hydrogen peroxide in the presence of at most 5 mg/l active chlorine through a filter made of activated carbon and getting ready brine; (C) handling, at least part of ready brine obtained at the stage of (b), at the stage of ion exchange; (d) processing at least part of the solution obtained at the stage, at the stage of electrolysis; (e) the allocation of at least part of chlorine, alkali metal hydroxide, hydrogen and brine obtained at the stage of (d); (f) processing at least part of the solution obtained at the stage of (e)under obesjajusee implemented in the presence of hydrogen peroxide; and (g) recycling, at least part obezhirennogo brine obtained at the stage (f), to the stage of (a).

2. The method according to claim 1, wherein the stage of (a) carried out in a tank in which there is a source of chloride of alkaline metal, in which the tank water is added and the resulting brine is then removed from the tank.

3. The method according to claim 1 or 2, where brine, prepared at the stage of (a), is a saturated solution of sodium chloride.

4. The method according to claim 1 or 2, in which stage (s) carried out at a temperature in the range from 20 to 80 degrees C.

5. The method according to claim 1 or 2, in which the stage of (b) is carried out at a temperature in the range from 20 to 80 C and a pressure in the range from 1 to 10 bar abs.

6. The method according to claim 1 or 2, in which stage (s) carried out at a temperature in the range from 20 to 80 C and a pressure in the range from 1 to 10 bar abs.

7. The method according to claim 1 or 2, in which stage (d) carried out at a temperature in the range from 80 to 90 C and the pressure in the range of 1.0 to 2 bar absolute.

8. The method according to claim 1 or 2, in which stage (f) carried out at a temperature in the range from 80 to 90 C and the pressure in the range from 1 to 3 bar abs.

9. The method according to claim 1 or 2, in which the brine on stage (f) contains 170-240 g/l chloride alkali metal.

10. The method according to claim 1 or 2, in which chloride alkaline metal is sodium chloride, and an alkali metal hydroxide is a sodium hydroxide, or chloride alkaline metal is potassium chloride, and the alkali metal hydroxide is a potassium hydroxide.

11. Device with computer control for realization of the method according to any one of claims 1 to 10, which includes a reservoir for source chloride alkali metal; filter element which is connected with the tank; ion exchange the item which is connected with filter element; an electrolytic cell, is connected with ion exchange element, in which the electrolytic element has the outlet to chlorine, outlet for alkali metal hydroxide, outlet for hydrogen and outlet brine; the first pump to transport the brine from the tank in an electrolytic cell; optional second pump for transporting obezhirennogo brine from electrolytic cell in the reservoir, and one or more of these elements provided with one or more sensor to monitor one or more parameters of the process, such as temperature, pressure, voltage or amperage as the sensors connected to one or more first computer, which is the first computer connected to one or more second computer in the control center via a data network like the control center removed from the electrolytic cell.