Plant for chlor-alkali electrolysis and a process for using it

This application claims priority to European application No. 13162062.7 filed on April 3, 2013, the whole content of this application being incorporated herein by reference for all purposes.

The present invention relates to a plant for chlor-alkali electrolysis.

Plants for chlor-alkali electrolysis are well known. They are constructed from equipment parts that are assembled on the production site. Those plants are dedicated to the manufacture of high volumes of specific products. Such plants exhibit low if not nil flexibility in process conditions and/or part arrangements.

The object of the present invention is to provide a chlor-alkali electrolysis plant which does not present these drawbacks.

The invention therefore relates in a first embodiment to a mobile/movable chlor-alkali electrolysis plant comprising at least one chlor-alkali electrolysis module mounted on a first support which can be moved as a whole, and optionally at least one module for a treatment of the electrolyte of the chlor- alkali electrolysis module mounted on a second support which can be moved as a whole.

One important feature of the plant is that it is mobile or expressed in a better way movable. By mobile/movable, one intends to denote that the plant can be transported from one site to another one with minimal handling, i.e. minimal amount of dismantling/assembling operations. This movable feature is made possible by the use of a support mounted chlor-alkali electrolysis module and an optional support mounted module for a treatment of the electrolyte, which modules constitute parts of the plant which can independently be moved as a whole.

Preferably, the movable chlor-alkali electrolysis plant according to the invention comprises at least one chlor-alkali electrolysis module mounted on a first support which can be moved as a whole, and at least one module for a treatment of the electrolyte of the chlor-alkali electrolysis module mounted on a second support which can be moved as a whole.

The movable chlor-alkali electrolysis plant according to the invention is named indifferently movable chlor-alkali electrolysis plant or movable electrolysis plant in the text of the present application. Similarly, the chlor-alkali electrolysis module is named indifferently chlor-alkali electrolysis module or electrolysis module.

Such a movable electrolysis plant exhibits at least one of the following additional advantages of allowing evaluation of:

■ various process conditions like electrolysis parameters such as temperature, pressure, voltage, current densities, electrolyte qualities :

■ various electrolyte treatments prior to and/or after electrolysis;

■ various equipments making the parts of the plant;

■ various arrangements of the parts of the plants.

In the next part of the description:

■ the electrolysis module mounted on a support can indifferently be designated as support mounted electrolysis module or electrolysis skid;

■ the module for a treatment of the electrolyte of the electrolysis module can be indifferently designated as support mounted electrolyte treatment module or electrolyte treatment skid, or treatment skid, and

■ the electrolyte of the electrolysis module can be designated as electrolyte.

In a preferred aspect of the first embodiment, the movable electrolysis plant is a plant for the production of chlorine. In a more preferred aspect of the first embodiment, the movable electrolysis plant is a plant for the production of chlorine by electrolysis of brine. In a still more preferred aspect of the first embodiment, the movable electrolysis plant is a chlor-alkali membrane electrolysis plant for the production of chlorine.

In the movable electrolysis plant according to the invention, the first support and the second support can be distinct or can be the same. It is preferred that the first support and the second support are distinct.

In the movable electrolysis plant according to the invention, the support can be of any type. This support must be resistant enough to accommodate the weight of the module. It must be rigid enough to be moved when moved with the module. The support is preferably a metallic support. The support is more preferably a container or a platform. First and second supports are therefore more preferably a container or a platform. Examples of platforms are platforms constituted by a basis only or those comprising further a vertical axis on each of the four corner.

In case the first support and the second support are distinct, one of them can be a container and the other a platform, both of them can be a container or both of them can be a platform. The support mounted module is more preferably assembled in a container, preferably a standardized-size container, or on a platform, preferably a standard- size platform. The support mounted module is most preferably assembled in a container, preferably a standardized-size container.

The module is therefore advantageously easily transported by transporting the container with its content or the platform with its content.

Transportation can be by road, by rail, by air, by sea, or by any

combination thereof. Transportation is preferably by road since industrial sites are more easily accessible by road than by any other transportation means. The other means like by air, by sea or by rail, can however be envisioned at least for part of the transportation itinerary which is intermediate between the sites.

The movable electrolysis plant according to the invention can therefore be transported with a truck and discharged from the truck with usual mechanical means. An example of usual mechanical means is a fork-lift truck. Another example is a crane.

In the movable electrolysis plant according to the invention, the support has advantageously dimensions adapted to transportation.

Standard-size containers can be of any type. Standard-size platforms can be of any type. Such types are for example as disclosed in International Standard ISO 6346 managed by the International Container Bureau.

Standard-size containers are preferably selected from Standard 20', upgraded 20', Standard 40', High Cube 40', Open Top 20', Open Top 40', Reefer 20', Reefer 40', Reefer High Cube 40', Flat Rack 20', Flat Rack 40', Flat Rack Collapsible 20' or Flat rack Collapsible 40', which characteristics are disclosed in http://www.foreign-trade.com/reference/ocean.cfm.

Standard-size platforms are preferably selected from Platform 20', Platform 40', Chassis 23'6", Chassis 33' Tri-axle or Chassis 40' Gooseneck, which characteristics are disclosed at http ://www. foreign- trade . com/reference/ocean . cfm.

The support mounted electrolysis module and the support mounted module for the electrolyte treatment can be moved as whole. By as a whole, it is intended to mean that a minimal dismantling of the electrolysis skid or the treatment skid is needed, before moving of the skid. By minimal dismantling, it is intended to mean that at most 10 % by weight, preferably at most 5 % by weight, more preferably at most 1 % by weight of the electrolysis module mounted on the support or of the module for the treatment of the cell electrolyte mounted on the support, is dismantled before moving the skids.

The movable electrolysis plant according to the invention is therefore advantageously not a plant deposited in a metallic frame or in a container or on a platform for transportation and separated from it for being used.

In the movable electrolysis plant according to the invention, the support mounted electrolysis module usually exhibits an external envelope having a length lower than or equal to 12.50 m, a width lower than or equal to 2.50 m and a height lower than or equal to 3.50 m. The electrolysis skid has usually a weight lower than or equal to 40000 kg.

In the movable electrolysis plant according to the invention, the support mounted module for a treatment of the electrolyte, usually exhibits an external envelope having a length lower than or equal to 12.50 m, a width lower than or equal to 2.50 m and a height lower than or equal to 3.50 m. The treatment skid has usually a weight lower than or equal to 40000 kg.

By external envelope, one intends to mean the minimal parallelepiped volume which can contain the electrolysis or the treatment skid.

In the movable electrolysis plant according to the invention, both the electrolysis skid and the electrolyte treatment skid when present, exhibit an external envelope as mentioned here above.

In the movable electrolysis plant according to the invention the support mounted electrolysis module and/or the support mounted module for a treatment of the electrolyte when present exhibit at least one of the following features:

■ an external envelope having a length lower than or equal to 5.89 m, a width lower than or equal to 2.33 m, a height lower than or equal to 2.38 m, preferably lower than or equal to 2.28 m and a weight lower than or equal to 21727 kg;

■ an external envelope having a length lower than or equal to 5.89 m, a width lower than or equal to 2.31 m, preferably lower than or equal to 2.28 m, a height lower than or equal to 2.38 m, preferably lower than or equal to 2.28 m and a weight lower than or equal to 28120 kg;

■ an external envelope having a length lower than or equal to 12.01 m, a width lower than or equal to 2.33 m, a height lower than or equal to 2.38 m, preferably lower than or equal to 2.28 m and a weight lower than or equal to 26780 kg; ■ an external envelope having a length lower than or equal to 12.01 m, a width lower than or equal to 2.33 m, a height lower than or equal to 2.69 m, preferably lower than or equal to 2.56 m and a weight lower than or equal to 26512 kg;

■ an external envelope having a length lower than or equal to 5.89 m, a width lower than or equal to 2.31 m, preferably lower than or equal to 2.28 m, a height lower than or equal to 2.33 m, preferably lower than or equal to 2.18 m and a weight lower than or equal to 21600 kg;

■ an external envelope having a length lower than or equal to 12.01 m, a width lower than or equal to 2.33 m, a height lower than or equal to 2.33 m, preferably lower than or equal to 2.26 m and a weight lower than or equal to 26630 kg;

■ an external envelope having a length lower than or equal to 5.38 m, a width lower than or equal to 2.26 m, a height lower than or equal to 2.26 m, preferably lower than or equal to 2.20 m and a weight lower than or equal to 20756 kg;

■ an external envelope having a length lower than or equal to 11.48 m, a width lower than or equal to 2.26 m, a height lower than or equal to 2.18 m, preferably lower than or equal to 2.13 m and a weight lower than or equal to 25526 kg;

■ an external envelope having a length lower than or equal to 11.35 m, a width lower than or equal to 2.28 m, a height lower than or equal to 2.48 m, preferably lower than or equal to 2.43 m and a weight lower than or equal to 26109 kg;

■ an external envelope having a length lower than or equal to 5.61 m, a width lower than or equal to 2.20 m, a height lower than or equal to 2.23 m and a weight lower than or equal to 27722 kg;

■ an external envelope having a length lower than or equal to 12.06 m, a width lower than or equal to 2.08 m, a height lower than or equal to 1.95 m and a weight lower than or equal to 38918 kg;

■ an external envelope having a length lower than or equal to 5.63 m, a width lower than or equal to 2.20 m, a height lower than or equal to 2.23 m and a weight lower than or equal to 27722 kg;

■ an external envelope having a length lower than or equal to 12.06 m, a width lower than or equal to 2.08 m, a height lower than or equal to 1.95 m and a weight lower than or equal to 38918 kg; ■ an external envelope having a length lower than or equal to 6.07 m, a width lower than or equal to 2.43 m, a height lower than or equal to 2.23 m and a weight lower than or equal to 23993 kg;

■ an external envelope having a length lower than or equal to 12.19 m, a width lower than or equal to 2.43 m, a height lower than or equal to 1.95 m and a weight lower than or equal to 30117 kg;

■ an external envelope having a length lower than or equal to 8.25 m and a weight lower than or equal to 17955 kg;

■ an external envelope having a length lower than or equal to 12.37 m and a weight lower than or equal to 20227 kg;

■ an external envelope having a length lower than or equal to 9.97 m and a weight lower than or equal to 17955 kg;

■ an external envelope having a length lower than or equal to 12 m and a weight lower than or equal to 20227 kg.

In the movable electrolysis plant according to the invention, the support mounted electrolysis module and/or the support mounted module for a treatment of the electrolyte each of about 11.55 m long, about 2.5 m wide, about 3 m tall and weighing about 15000 kg are particularly convenient.

In the movable electrolysis plant according to the invention, the support mounted electrolysis module and/or the support mounted module for a treatment of the electrolyte each of about 12.20 m long, about 2.5 m wide, about 3.1 m tall and weighing about 15000 kg are more particularly convenient.

Both skids are designed for easy installation on a concrete floor.

In the movable electrolysis plant according to the invention, the electrolysis module contains usually at least one electrolyzer. The electrolyzer can be of any type. The electrolyser can be mono-polar or bi-polar. It is preferably bi-polar. The electrolyzer preferably contains at least one anode and at least one cathode. The electrolyser contains more preferably at least one anode compartment and at least one cathode compartment. The cathode and anode compartments are preferably separated, more preferably by a separator. The separator can be of any type. The separator is preferably a diaphragm or a membrane and more preferably a membrane. The diaphragm can be of any type. The diaphragm is preferably selected from a polymer- inorganic compounds based diaphragm, or an asbestos based diaphragm. The diaphragms are preferably as described in T.F O'Brien, T. Bommaraju and F. Hine, Handbook of Chlor-Alkali Technology, Springer, 2005, pages 272-273 and 292-294. Examples of polymer-based diaphragm are Polyramix (PMX) diaphragms. Examples of asbestos-based diaphragms are Chrysotile diaphragms. The membrane can be of any type. The membrane is preferably an ion-exchange membrane, preferably a cation- exchange membrane. The cation exchange membrane is preferably based on a perfluoropolymer containing sulfonic and/or carboxylic groups, more preferably sulfonic and carboxylic groups. The membranes are preferably as described in Handbook of Chlor-Alkali Technology, Springer 2005, pages 306-307.

Examples of membranes are N2030 and N2040 from DuPont, F6805 from Asahi Kasei Chemicals, F8020, F 8020SP and F 8080, F8081, F8080HD and F8081HD from Asahi Glass. In the electro lyser, more preferably in the anodic

compartment of the electrolyzer, the anode can be of any type. Examples of anodes are described in Handbook of Chlor-Alkali Technology, Springer 2005, pages 211-237. The anode is preferably a coated anode, more preferably containing ruthenium oxide as basic component along with an oxide of a non- platinum metal (e.g. Ti, Sn or Zr), and optionally a second precious metal oxide selected from the group Pt, Ir. In the electrolyser, more preferably in the cathodic compartment of the electrolyzer, the cathode can be of any type.

Examples of cathodes are described Handbook of Chlor-Alkali Technology, Springer 2005, pages 241-265. The cathode is preferably a coated cathode, more preferably containing ruthenium oxide and optionally a second precious metal selected from the group of Pt and Pd.

In the movable electrolysis plant according to the invention, the electrolyser contains preferably at least two different separator-electrode assemblies. The two separators of the two different separator-electrode assemblies are usually both a diaphragm or a membrane or are one diaphragm and one membrane, and preferably both a membrane. The two separator- electrode assemblies preferably differ from each other by at least one of the following features:

■ They contain a different separator

■ They contain a different membrane,

■ They contain a different diaphragm,

■ They contain a different anode,

■ They contain a different cathode.

In the movable electrolysis plant according to the invention, the electrolyser has usually a width higher than or equal to 0.1 m, preferably higher than or equal to 0.2 m and most preferably higher than or equal to 0.3 m. This width is usually lower than or equal to 1.0 m, preferably lower than or equal to 0.8 m and most preferably lower than or equal to 0.5 m. The electro lyser has usually a height higher than or equal to 0.80 m, preferably higher than or equal to 1.00 m and most preferably higher than or equal to 1.25 m. This height is usually lower than or equal to 2.0 m, preferably lower than or equal to 1.8 m and most preferably lower than or equal to 1.7 m. The electrolyser has usually a thickness higher than or equal to 0.10 m, preferably higher than or equal to 0.25 m and most preferably higher than or equal to 0.30 m. This thickness is usually lower than or equal to 0.80 m, preferably lower than or equal to 0.70 m and most preferably lower than or equal to 0.60 m.

In the movable electrolysis plant according to the invention, when the separator in the electrolyser is a membrane, the membrane has usually a geometric area higher than or equal to 0.01 m ² , preferably higher than or equal to 0.05 m ² and most preferably higher than or equal to 0.1 m ² . This area is usually lower than or equal to 1 m ² , preferably lower than or equal to 0.50 m ² and most preferably lower than or equal to 0.20 m ² . A membrane with a geometric area of about 0.15 m ² is particularly convenient. The membrane can be of any geometric form. A rectangular membrane is preferred.

In the movable electrolysis plant according to the invention, the

electrolyser is preferably a bipolar chlor-alkali electrolyser containing three membranes with an individual active surface of about 0.15 m ² , composed by two bipolar elements and two half-cell extremity elements. By active surface, one intends to mean the surface of the membrane which is contact with the electrolyte. The anodic compartment of the electrolyser is preferably fed with a brine. This configuration permits to test three different membranes with the same feeding brine. In this case, the movable electrolysis plant is well suited for chlorine production.

In the movable electrolysis plant according to the invention, the electrolysis module contains usually at least one electrical current rectifier. The current rectifier can be of any type. The minimal operational current is usually higher than or equal to 0.5 kA and lower than or equal to 2.5 kA. When the electrolyser is a membrane electrolyser, the minimal operational current density is usually higher than or equal to 1 kA/m ² , preferably higher than or equal to 2 kA/m ² , more preferably higher than or equal to 5 kA/m ² , and most preferably higher than or equal to 6 kA/m ² . This maximal operational current density is usually lower than or equal to 50 kA/m ² , preferably lower than or equal to 20 kA/m ² , more preferably lower than or equal to 15 kA/m ² , and most preferably lower than or equal to 10 kA/m ² . An electrical current rectifier from ELCA with a maximum operational current density of about 10 kA/m ² is convenient. Such a rectifier can deliver a direct current under a direct voltage of 0 to 15V. Such a rectifier usually accepts an input sinusoidal voltage from 0 to 1550 V.

The electrical current rectifier can be connected to any source of compatible alternating current.

In the movable electrolysis plant according to the invention, the

electrolysis module contains usually at least one tank for storing the cell electrolyte.

In the movable electrolysis plant according to the invention, the electrolysis module preferably contains at least one electrolyzer with at least one anode compartment separated from at least one cathode compartment by a separator, and/or at least one electrical current rectifier, and/or at least one tank for storing an anolyte, and/or at least one tank for storing a catholyte.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, the electrolysis cell contains usually at least one tank for storing for storing an anolyte, and/or at least one tank for storing a catholyte, preferably at least one tank for storing the catholyte, and more preferably only one tank for storing the catholyte.

The tank for storing the anolyte or the catholyte can be of any form, but preferably cylindrical. They can be made of any material, in particular materials resisting to corrosion by the anolyte or the catholyte.

The tank for storing the anolyte or the catholyte has a diameter usually higher than or equal to 0.10 m, preferably higher than or equal to 0.25 m and most preferably higher than or equal to 0.50 m. This diameter is usually lower than or equal to 2.0 m, preferably lower than or equal to 1.0 m and most preferably lower than or equal to 0.8 m. This tank has a height usually higher than or equal to 0.2 m, preferably higher than or equal to 0.5 m and most preferably higher than or equal to 0.7 m. This height is usually lower than or equal to 2.0 m, preferably lower than or equal to 1.5 m and most preferably lower than or equal to 1.0 m. This tank has a volume usually higher than or equal to 20 1, preferably higher than or equal to 50 1, and more preferably higher than or equal to 90 1. This tank has a volume usually lower than or equal to 300 1, preferably lower than or equal to 250 1, and more preferably lower than or equal to 220 1. A volume of about 200 1 is particularly convenient. In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, the anolyte is preferably a brine and the catholyte is preferably a sodium hydroxide solution. The tank for storing the brine is preferably made of PVC/GFRP (polyvinylchloride/glass fiber reinforced polymer). The tank for storing the catholyte is preferably made of PP/GFRP (polypropylene/glass fiber reinforced polymer).

In the movable electrolysis plant according to the invention, the tank for storing the brine is preferably part of the at least one module for a treatment of the electrolyte mounted on a support. The tank for storing the sodium hydroxide preferably serves as a tank for supplying the catholyte to the cathodic

compartment of the electrolyser and for collecting the catholyte from the cathodic compartment of the electrolyser. In the catholyte tank, the sodium hydroxide solution concentration can be and is preferably adjusted by means of a dilution with water.

In the movable electrolysis plant according to the invention, the electrolysis module may comprise at least one degasser for degassing the electrolyte, preferably the electrolyte exiting the electrolyser.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, the electrolysis module may comprise at least one degasser for degassing the anolyte and at least one degasser for degassing the catholyte, preferably the anolyte and the catholyte exiting the electrolyser. The degassers can be of any form, but preferably cylindrical. They can be made of any material, preferably materials resisting to corrosion by the anolyte or the catholyte, and the gas present in the anolyte or in the catholyte, preferably in the anolyte or in the catholyte exiting the electrolyser. When the anolyte is a brine, the gas leaving the anodic compartment comprises chlorine. When the catholyte is sodium hydroxide, the gas leaving the cathodic

compartment comprises hydrogen. The degasser for the anolyte is preferably made of PVC/GFRP. The degasser for the catholyte is preferably made of PP/GFRP. The degasser for the anolyte and the degasser for the catholyte have a diameter usually higher than or equal to 0.05 m, preferably higher than or equal to 0.10 m and most preferably higher than or equal to 0.15 m. This diameter is usually lower than or equal to 1.0 m, preferably lower than or equal to 0.5 m and most preferably lower than or equal to 0.3 m. These degassers have a height usually higher than or equal to 0.10 m, preferably higher than or equal to 0.25 m and most preferably higher than or equal to 0.50 m. This height is usually lower than or equal to 1.00 m, preferably lower than or equal to 0.80 m and most preferably lower than or equal to 0.70 m.

In the movable electrolysis plant according to the invention, when the electro lyser is a membrane type electro lyser, the anolyte is preferably a brine and the catholyte is preferably a sodium hydroxide solution, the degasser for the anolyte is for removing chlorine from the brine exiting the electro lyser and the degasser for the catholyte is for removing hydrogen from the caustic soda exiting the electrolyser. In this case, the movable electrolysis plant is convenient for chlorine and caustic soda productions.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, the electrolysis module may comprise at least one pump for providing the anolyte from an anolyte storing tank to the electrolyser and at least one pump for providing the catholyte from a catholyte storing tank to the electrolyser.

The pump can be of any type, e.g. centrifugal or metering. The operational minimal delivery flow rate is usually higher than or equal to 1 1/h, preferably higher than or equal to 2 1/h, more preferably higher than or equal to 5 1/h and most preferably higher than or equal to 10 1/h. The operational maximal delivery flow rate is usually lower than or equal to 200 1/h, preferably lower than or equal to 150 1/h, more preferably lower than or equal to 120 1/h and most preferably lower than or equal to 100 1/h. For the anolyte, preferably a brine, a centrifugal pump is preferred. A pump able to deliver a flow rate of 60 1/h under 2 bar like a HTM model from Giemmecotti, is convenient. A pump which part is in contact with brine being preferably made of polyvinylidene fluoride (PVDF) is convenient. For the catholyte, preferably a caustic soda solution, a centrifugal pump is preferred. A pump able to deliver a flow rate of 60 1/h under 1 bar like a MD model from Iwaki is convenient. A pump which part is in contact with caustic soda being preferably made of polytetrafluoroethylene (PTFE), copolymer of ethylene and trifluoroethylene (ETFE), 904 austenitic steel, Hastelloy C or Ni 200/201 is convenient.

In the movable electrolysis plant according to the invention, the skid cell may comprise at least one heat-exchanger, preferably for heating the electrolyte entering the electrolyser.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, the electrolysis module may comprise at least one heat-exchanger for heating the anolyte, preferably a brine, more preferably entering the electrolyser and at least one heat-exchanger for heating the catholyte, preferably a solution of caustic soda, more preferably entering the electrolyser.

The heat exchanger can be of any type. The operational minimal power duty is usually higher than or equal to 1.0 (kW), preferably higher than or equal to 2.0 kW, more preferably higher than or equal to 2.5 kW and most preferably higher than or equal to 3.0 kW. The operational maximal power duty is usually lower than or equal to 15 kW, preferably lower than or equal to 10 kW, more preferably lower than or equal to 7 kW and most preferably lower than or equal to 5 kW. The heat-exchanger for the anolyte and the catholyte are preferably plate heat-exchangers, like M3 model from Alfa Laval. The parts of the heat- exchanger in contact with the anolyte or the catholyte are preferably made of Hastelloy Grade "C".

In the movable electrolysis plant according to the invention, the electrolysis module usually contains at least one hydraulic seal. The seals are usually used for protecting the electrolyser from undesired under- or overpressures.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, and when the catholyte is a caustic soda solution, the cathodic compartment of the electrolyser is operated under light pressure, and the electrolysis module preferably comprises at least one hydraulic seals to maintain a correct pressure on the cathodic side. This hydraulic seal is preferably made of PP/GFRP.

The hydraulic seals can be of any type, as for example a seal which uses a bubble distributor placed under a liquid level. The hydraulic seals can be of any form, but preferably cylindrical. The hydraulic seals have a diameter usually higher than or equal to 0.1 m, preferably higher than or equal to 0.2 m and most preferably higher than or equal to 0.3 m. This diameter is usually lower than or equal to 1.0 m, preferably lower than or equal to 0.7 m and most preferably lower than or equal to 0.5 m. These hydraulic seals have a height usually higher than or equal to 0.4 m, preferably higher than or equal to 0.5 m and most preferably higher than or equal to 0.6 m. This height is usually lower than or equal to 1.0 m, preferably lower than or equal to 0.9 m and most preferably lower than or equal to 0.8 m. The hydraulic seals are preferably made of PP/GFRP.

In the movable electrolysis plant according to the invention, the electrolysis module usually contains at least one regulating valve. The regulating valve is usually used to guarantee a pressure difference between different parts of the electrolysis module.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, and when the anolyte is a brine, at least one regulating valve is used. Said valve operated jointly with another regulating valve placed on an air inlet allows maintaining a desired pressure difference between the anodic and the cathodic compartment of the electrolyser.

The various components of the skid cell are usually connected one to each other via pipes. The pipes are designed to accommodate liquid and/or gas streams.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, when the anolyte is a brine and the catholyte is a caustic soda solution, the pipes are preferably designed to accommodate flow rates of brine or chlorine containing brine or caustic soda solutions or gaseous chlorine or gaseous hydrogen, or any mixture thereof.

The various components of the electrolysis skid are realized in materials which are resistant to corrosion by the electrolyte, the anolyte or the catholyte, or by the products of the electrolysis, more specifically under the operating conditions of the electrolysis cell.

In the movable electrolysis plant according to the invention, when the electrolyser is a membrane type electrolyser, when the anolyte is a brine and the catholyte is a caustic soda solution, the various components of the electrolysis skid are realized in materials which are resistant to corrosion by brine and/or gaseous chlorine and/or brine containing chlorine. When the catholyte is a caustic soda solution, the various components of the electrolysis skid are realized in materials which are resistant to corrosion by caustic soda solutions and/or gaseous hydrogen, and/or caustic soda solutions containing hydrogen. A preferred material resistant to brine, chlorine and brine containing chlorine is PVC/GFRP. A preferred material resistant to hydrogen, caustic soda solutions and caustic soda solutions containing hydrogen is PP/GFRP.

The movable electrolysis plant according to the invention may contain at least one module for a treatment of the electrolyte mounted on a support which can be moved as a whole. The movable electrolysis plant according to the invention preferably contains at least one module for a treatment of the electrolyte mounted on a support which can be moved as a whole, often two modules for a treatment of the electrolyte and sometimes three modules for a treatment of the cell electrolyte, each mounted on a support which can be moved as a whole.

When the movable electrolysis plant according to the invention contains at least one electrolyser with at least one anode compartment separated from at least one cathode compartment by a separator, preferably a membrane, and when the anolyte is a brine, the at least one module for a treatment of the electrolyte is a module for treating the brine. This module preferably comprises at least one unit selected from:

■ A unit (A) for adjusting the salt concentration of the brine;

- A unit (B) for removing fine solid particles from the brine;

■ A unit (C) for removing carbonate ions from the brine;

■ A unit (D) for removing iron and aluminum from the brine;

■ A unit (E) for removing calcium and magnesium, from the brine;

■ A unit (F) for removing iodide from the brine;

- A unit (G) for removing bromide from the brine;

■ A unit (H) for removing silicon from the brine;

■ A unit (I) for removing chlorine from the brine;

■ A unit (J) for removing chlorate from the brine;

■ A unit (K) for removing sulphates from the brine;

■ A unit (L) for removing organic compounds from the brine;

■ A unit (M) for removing mercury from the brine;

■ A unit (N) for removing ammonia from the brine.

By brine one intends to denote any aqueous composition containing a metal chloride salt, preferably an alkaline metal chloride, an alkaline-earth metal chloride or any mixture thereof, more preferably an alkaline metal chloride, still more preferably sodium chloride, potassium chloride or any mixture thereof and most preferably sodium chloride.

A module for the treatment of the brine comprising at least one unit selected from a unit (A), a unit (B), a unit (C), a unit (D) and a unit (E), as described above, is convenient. Such a module will be designated as first brine treatment module or skid 2. When present in the module the units are preferably connected according to the sequence (A) < (B) < (C) < (D) < (E). A module for the treatment of the brine comprising one unit (A), one unit (B), one unit (C), one unit (D) and one unit (E), as described above, is particularly convenient.

The brine treatment skid 2 may also contain in addition, at least one unit selected from a unit (F), a unit (G) and a unit (H) as described above. When present in the module, the units are preferably connected according to the sequence (A) < (B) < (C) < (H) > (D) < (F) < (G) < (E).

The first brine treatment module is preferably connected upstream of the electrolysis cell module. Upstream means that the brine exiting the brine treatment module 2 feeds the electrolysis module.

Units (A) to (E) can be as described in Handbook of Chlor-alkali

Technology, Springer 2005, pages 495-509; 529, preferably with size and weight adapted for mounting on a support that can be moved as a whole.

Units (F) to (H) can be as described respectively in patent applications EP 94203514.8, WO 2005/068686 and WO 2009/133074 of Solvay (Societe

Anonyme), the contents of which are incorporated by reference. The person of ordinary skill in the art will easily know how to select the equipment for carrying out the treatments in the various units, in particular equipment dimensions compatible with the dimensions of the support.

A module for the treatment of the brine comprising at least one unit selected from a unit (I) and a unit (J) and (K) as described above, is also convenient. Such a module will be designated as second brine treatment module or skid 3. When present in the skid, those units are preferably connected according to the sequence (I) < (J) < (K). The module for treating the brine comprising at least one of the above units is preferably connected downstream of the electrolysis module. Downstream means that the brine exiting the electrolysis module feeds the treatment module. Units (I), (J) and (K) can be as described in Handbook of Chlor-alkali Technology, Springer 2005, pages 636- 649 and 665-696, preferably with size and weight adapted for mounting on a support that can be moved as a whole.

A module for the treatment of the brine comprising at least one unit (L) is also convenient. Such a module will be designated as third brine treatment module or skid 4.

The adjustment of the salt concentration of the brine in unit (A) can be carried out by any means, preferably at least by salt addition, more preferably at least by salt addition to a least one brine less concentrated in salt. Such a brine exhibits a concentration in salt preferably sodium chloride, usually higher than or equal to 200 g/kg, often higher than or equal to 210 g/kg, frequently higher than or equal to 230 g/kg, and in particular higher than or equal to 250 g/kg. Such a brine exhibits a concentration in salt, preferably sodium chloride, usually lower than or equal to 320 g/kg, often lower than or equal to 300 g/kg, frequently lower than or equal to 280 g/kg, and in particular lower than or equal to 260 g/kg. A brine less concentrated in salt to be submitted to saturation will be called brine 1. Unit (A) for adjusting the salt concentration of the brine is preferably a saturation unit. A saturation unit is understood to mean a unit able to deliver a brine saturated in salt at a temperature between 10 °C and 30 °C. The saturation unit can be as described in Handbook of Chlor-alkali Technology, Springer 2005, pages 509-525. The saturation unit comprises preferably at least one vessel for carrying the saturation (saturator). Saturation is carried out by any means, preferably with vacuum salt, for example vacuum salt by ESCO. The supply of salt to the saturator is made by any means, preferably by means of a belt conveyor or by a screw system, and more preferably by a screw-system. The supply system can be fed by any means, preferably by a hopper connected to a big bag containing the vacuum salt.

Unit (A) may also comprises at least one additional vessel for storing the brine less concentrated in salt (brine 1) and which is to be saturated.

Unit (A) preferably comprises at least one other additional vessel for adjusting the pH of the brine less concentrated in salt (brine 1) and which is to be saturated. A brine less concentrated in salt to be submitted to saturation and which is pH adjusted before saturation will be called a brine 2.

Unit (A) preferably contains at least one additional vessel for storing the saturated brine produced in the saturator.

A saturated brine will be called brine 3.

The saturator can be equipped with a stirring device and/or a heating system. This is usually for speeding up the saturation of the brine.

The form, dimensions and/or materials of the saturator, of the vessel for storing the saturated brine and of the vessel for storing the less concentrated brine can be as disclosed above for the vessel containing the anolyte, preferably the brine.

The removal of fine solid particles from the brine, preferably from brine 3, can be carried out by any means, preferably at least by filtration. The filtration unit can be as described in of Chlor-alkali Technology, Springer 2005, pages 592-606. Unit (B) contains preferably at least one filter, more preferably one cartridge filter. The cartridge filter can be of any type. Pall cartridge filters are preferred (for example double-ended oper cartridge filters of the PUY series).

A brine epurated in fine solid particles will be named brine 4. The removal of carbonate ions from the brine, preferably from a brine 4, can be carried out by any means, preferably at least by acid treatment and venting. Unit (C) can be as described in Handbook of Chlor-alkali Technology, Springer 2005, pages 626-631. Unit (C) contains preferably at least one vessel (decarbonator) for carrying the acid treatment. The acid treatment is carried out by any means, preferably by addition of hydrochloric acid. The removal of the carbonate is preferably carried out by venting carbon dioxide. The treatment is preferably carried out at a pH higher than or equal to 1.0 and lower than or equal to 2.5 . Venting is preferably carried out with an inert gas, more preferably with nitrogen. Unit (C) therefore preferably contains at least one pump for adding acid to the decarbonator, at least one mean for controlling the pH of the brine in the carbonator, at least one mean to supply nitrogen to the decarbonator and at least one means to vent a mixture containing nitrogen and carbon dioxide.

The decarbonator can optionally be equipped with a stirring device and/or a heating system. This is usually for speeding up the removal of carbonates ions from the brine.

The form, dimensions and/or materials of the decarbonator can be as disclosed above for the vessel containing the anolyte, preferably the brine.

The nitrogen is usually supplied from any source, like from cylinders or from a nitrogen pipeline, and preferably from a nitrogen pipeline. Cylinders are usually not part of the electrolyte treatment module.

The removal of iron and aluminum from the brine, preferably a brine 5, can be carried out by any means, preferably at least by filtration. Unit (D) contains preferably at least one filtration column. The pH of the brine is preferably adjusted before passing onto the filtration column. The treatment is preferably carried out at a pH higher than or equal to 4 and lower than or equal to 7. A pH of about 5.5 is convenient. The pH adjustment, if necessary, is preferably carried out in a vessel upstream of the column. Therefore, unit (D) contains preferably at least one filtration column and at least one vessel upstream said column for pH adjustments. Unit (D) preferably contains at least one flow regulating system for adding the pH control agent to the brine, and at least one mean for controlling the pH of the brine in the vessel before feeding the filtration column. The pH control agent is preferably caustic soda. The filtrating agent can be of any type, but is preferably anthracite. The columns and/or the vessel for adjusting the pH can be equipped with a heating system. The vessel for adjusting the pH can be equipped with a stirring device.

The form, dimensions and/or materials of the vessel for adjusting the pH can be as disclosed above for the vessel containing the anolyte, preferably the brine.

The filtration column has a diameter usually higher than or equal to 0.05 m, preferably higher than or equal to 0.10 m and most preferably higher than or equal to 0.12 m. This diameter is usually lower than or equal to 0.6 m, preferably lower than or equal to 0.3 m and most preferably lower than or equal to 0.2 m. This column has a height usually higher than or equal to 1.0 m, preferably higher than or equal to 2 m and most preferably higher than or equal to 2.5 m. This height is usually lower than or equal to 5.0 m, preferably lower than or equal to 3.5 m and most preferably lower than or equal to 3.0 m.

A brine epurated in iron and aluminum will be called brine 6.

The removal of divalent metals from the brine, preferably from a brine 6, can be carried out by any means, preferably at least by ion-exchange. Unit (E) can be as described in Handbook of Chlor-alkali Technology, Springer 2005, pages 606-626. . Unit (E) contains preferably at least one ion-exchange column. The pH of the brine is preferably adjusted before passing onto the ion-exchange column. The treatment is preferably carried out at a pH higher than or equal to 8 and lower than or equal to 10. A pH of about 9 is convenient. The adjustment is preferably carried out in a vessel upstream of the columns. Therefore, unit (E) contains preferably at least one ion-exchange column and at least one vessel upstream said column for pH adjustment. Unit (E) preferably contains at least one flow regulating system for adding the pH control agent to the brine, and at least one mean for controlling the pH of the brine in the vessel before feeding the ion exchange column. The pH control agent is preferably caustic soda, especially if a brine 6 is to be treated for removing divalent metals. The ion- exchanger can be of any type of ion-exchange resin, but is preferably a cation exchange resin, as for example TP208 resins from Lanxess.

The treatment is preferably carried out at a temperature higher than or equal to 50° C and lower than or equal to 70° C. For this purpose, the columns and/or the vessel for adjusting the pH can be equipped with a heating system. In particular, an heat exchanger placed between the vessel and the resin columns is particularly preferred. A plate heat exchanger made of Haste Hoy Grade "C" or titanium is particularly convenient. The vessel for adjusting the pH can be equipped with a stirring device.

The form, dimensions and/or materials of the vessel for adjusting the pH can be as disclosed above for the vessel containing the anolyte, preferably the brine.

The ion-exchange column has a diameter usually higher than or equal to 0.05 m, preferably higher than or equal to 0.10 m and most preferably higher than or equal to 0.12 m. This diameter is usually lower than or equal to 0.6 m, preferably lower than or equal to 0.3 m and most preferably lower than or equal to 0.2 m. This column has a height usually higher than or equal to 1.0 m, preferably higher than or equal to 1.5 m and most preferably higher than or equal to 2.0 m. This height is usually lower than or equal to 4.0 m, preferably lower than or equal to 3.0 m and most preferably lower than or equal to 2.5 m.

A brine epurated in divalent metals will be called brine 7.

After treatment on the ion-exchange columns, a brine 7 can be further filtrated to remove ion-exchange resin particles and optionally stored in the anolyte storing tank.

A brine epurated in ion-exchange resin particles will be called brine 8.

Therefore, the treatment module 2 preferably contains at least a least one cartridge filters for filtering a brine 7 and at least one tank for storing a brine 8.

The tank is as described above for the tank for storing the anolyte.

The cartridge filter is preferably a Pall filter of the PUY series with a cutoff lower than 100 micron.

The brine from the brine storing tank preferably feeds the anodic compartment of the electrolyser of the electrolysis module.

The removal of iodide from the brine can be carried out by any means, preferably at least by oxidation and ion-exchange, more preferably as disclosed in patent application EP 94203514.8 of Solvay (Societe Anonyme), the content of which is incorporated by reference. Unit (F) is preferably as disclosed in EP 94203514.8 from column 5, line 15 to column 6, line 52. The person of ordinary skill in the art will easily know how to adapt the equipment dimensions to be compatible with the dimensions of support.

The removal of bromide from the brine can be carried out by any means, preferably at least by oxidation, more preferably as disclosed in patent application WO 2005/068686 of Solvay (Societe Anonyme), the content of which is incorporated by reference. Unit (G) is preferably as disclosed in EP 94203514.8, examples 1 to 3. The person of ordinary skill in the art will easily know how to adapt the equipment dimensions to be compatible with the dimensions of support.

The removal of silicon from the brine can be carried out by any means, preferably at least by aluminium addition, precipitation and filtration, more preferably as disclosed in patent application WO 2009/133074 of Solvay (Societe Anonyme), the content of which is incorporated by reference. The person of ordinary skill in the art will easily know how to select the equipment for carrying out the removal of silicon, in particular equipment dimensions compatible with the dimensions of support.

The removal of mercury from the brine can be carried out by any means, preferably at least by precipitation, ion-exchange or adsorption as disclosed in Euro Chlor, Guideline for decommissioning of mercury Chlor- Alkali Plants, Env Prot 3, 5 ^th Edition September 2009 Euro Chlor Publication, pages 15-16.

Precipitation is usually carried out by sulfide addition and ionic mercury is precipitated as HgS which is further separated by filtration. Adsorption is usually carried on active charcoal after conversion of ionic mercury in to metallic mercury with the help of a reducing agent, such as sulfite.

Unit (M) is usually connected downstream to unit (J) and possibly downstream to unit (K).

The removal of ammonia from the brine can be carried out by any means, preferably at least by oxidation and stripping. Ammonia is usually oxidized into nitrogen which is removed by stripping. Unit (N) is usually connected downstream to unit (E) or (G).

The removal of chlorine from the brine can be carried out by any means, preferably at least by acid treatment and stripping. This treatment is usually followed by an adsorption treatment.

Unit (I) contains preferably at least one vessel for carrying the acid treatment and at least one column for the stripping treatment. The acid treatment is carried out by any means, preferably by addition of hydrochloric acid. The treatment is preferably carried out at a pH higher than or equal to 0 and lower than or equal to 3. A pH of about 1.8 is convenient. Venting is preferably carried out with an inert gas or air, and more preferably with air. Unit (I) therefore preferably contains at least one pump for adding acid to the vessel, at least one mean for controlling the pH of the brine in the vessel, at least one mean to supply air to the stripping column and at least one means to vent a mixture containing air and chlorine. Unit (I) may also comprise an adsorption column placed after the stripping column. The adsorption column preferably contains active coal.

The vessel for carrying out the acid treatment can be equipped with a stirring device and/or a heating system. The vessel is preferably equipped with a heating system, more preferably with an electrical resistance as heating system. The form, dimensions and/or materials of that vessel can be as disclosed above for the vessel containing the anolyte, preferably the brine.

The air is usually supplied from any source.

The stripping column and the adsorption column are as described in Handbook of Chlor-alkali Technology, Springer 2005, pages 665-696.

Unit (I) for chlorine removal may also contain at least one pump for adding a base to the vessel. Indeed if chlorates are to be removed, the pH has to be adjusted to a value usually lower than 1 for converting chlorates into chlorine, and then reverted back to a higher value for chlorine removal by stripping.

Unit (I) may be part of the electrolysis module, instead of being part of a treatment module.

A dechlorinated brine will be called brine 9.

The removal of chlorate from the brine can be carried out by any means, preferably at least by acid treatment and venting, optionally followed by catalytic hydrogenation.

Part of Unit (J) dedicated for acid treatment and venting can be as described for Unit (I) here above for acid treatment and venting. The treatment is preferably carried out at an HC1 excess higher than or equal to 20 g/1 of brine and lower than or equal to 50 g/1 of brine.

Part of unit (J) for catalytic hydrogenation is preferably as described in patent US 5779915 of SOLVAY UMWELTCHEMIE GmbH, the content of which is incorporated by reference. The person of ordinary skill in the art will easily know how to select the equipment for carrying out the removal of chlorate, in particular equipment dimensions compatible with the dimensions of support.

The removal of sulphates from the brine can be carried out by any means, preferably at least by addition of BaCl ₂ and filtration or by nano filtration with membranes. Unit (K) can be as described in Handbook of Chlor-alkali

Technology, Springer 2005, pages 636-647

Unit (K) includes preferably at least one vessel, one pump for pH adjustment, one pump for BaCl ₂ addition and a filter for brine filtering after BaCl ₂ addition. Preferred agent for pH adjustment is caustic soda. The treatment is preferably carried out at a pH higher than or equal to 8 and lower than or equal to 12. A pH of about 10 is convenient.

The removal of organic compounds from the brine can be carried out by any means, preferably at least by oxidation, more preferably by oxidation with a chlorine containing compound, more preferably as disclosed in patent application WO 2009/095429 of Solvay (Societe Anonyme), the content of which is incorporated by reference. The person of ordinary skill in the art will easily know how to select the equipment for carrying out the removal of organic compounds, in particular equipment dimensions compatible with the dimensions of support.

In the movable electrolysis plant according to the invention, the units (A), (B), (C), (D) and (E) are preferably part of a first support mounted module for treating the brine (skid 2). Such module may in addition comprise unit (F) and unit (G), and possibly unit (H).

In the movable electrolysis plant according to the invention, unit (I) and possibly the units (J) and (K) are preferably part of a second support mounted module for treating the brine (skid 3), different from the first support mounted module for treating the brine.

In the movable electrolysis plant according to the invention, unit (L) is preferably part of a third support mounted module for treating the brine (skid 4).

In the movable electrolysis plant according to the invention:

■ The adjustment of the salt concentration of the brine in unit (A) is preferably at least by salt addition to the brine;

■ The removal fine solid particles from the brine in unit (B) is preferably at least by filtration;

■ The removal of carbonate ions from the brine in unit (C) is preferably at least by acidification and venting;

■ The removal of iron and aluminium from the brine in unit (D) is preferably as least by adsorption;

■ The removal of calcium and magnesium from the brine in unit (E) is preferably at least by ion exchange;

■ The removal of iodide from the brine in unit (F) is preferably at least by oxidation and ion exchange;

■ The removal of bromide from the brine in unit (G) is preferably at least by oxidation and stripping; ■ The removal of silicon from the brine in unit (H) is preferably at least by precipitation and filtration;

■ The removal of chlorine from the brine in unit (I) preferably at least by

acidification, stripping and adsorption

■ The removal of chlorate from the brine in unit (J) is preferably at least by acidification or catalytic hydrogenation;

■ The removal of sulphate from the brine in unit (K) is preferably at least by precipitation and filtration, or nano filtration using membranes;

■ The removal organic compounds from the brine in unit (L) is preferably at least by oxidation;

■ The removal of mercury in unit (M) is preferably at least by precipitation, ion- exchange reduction or adsorption,

■ The removal of ammonia in unit (N) is preferably at least by oxidation and stripping.

In the movable electrolysis plant according to the invention, when present the units (A), (B), (C), (D) and (E) are preferably part of a first support mounted module for treating the brine and the units (I), (J), and (K) are preferably part of a second support mounted module for treating the brine.

In a first configuration, the electrolysis plant according to the invention consists of one electrolysis skid.

In a second configuration, the electrolysis plant according to the invention consists of one electrolysis skid and one first treatment skid, as described above. In a more preferred configuration, the first treatment skid is connected upstream to the electrolysis skid.

In a third configuration, the electrolysis plant according to the invention consists of one electrolysis skid, one first treatment skid and one second treatment skid, as described above. In a more preferred configuration, the first treatment skid is connected upstream to the electrolysis skid and the second treatment skid is connected downstream to the electrolysis skid.

In a fourth configuration, the electrolysis plant according to the invention consists of one electrolysis skid, one first treatment skid, one second treatment skid and one third treatment skid, as described above. In a more preferred configuration, the first treatment skid is connected upstream to the electrolysis skid, the second treatment skid is connected downstream to the electrolysis skid and the third treatment skid is connected upstream to the second treatment skid. In a fifth configuration, the electrolysis plant according to the invention consists of one electrolysis skid, one first treatment skid, one second treatment skid and one third treatment skid, the first treatment skid is connected upstream to the electrolysis skid, the second treatment skid is connected downstream to the electrolysis skid, the third treatment skid is connected upstream to the first treatment skid.

In the movable electrolysis plant according to the invention, the support mounted electrolysis module and the support mounted module for a treatment of the electrolysis module electrolyte are preferably connected via quick

connectors. By quick connectors, one intends to denote clamped fittings.

In the movable electrolysis plant according to the invention, one or more of the electrolysis module and the module for a treatment of the electrolyte are preferably equipped with one or more sensors for monitoring one or more parameters such as temperature, pressure, pH, voltage, current, flow rate, electrolyte composition or fluid level. The sensors are preferably interconnected with one or more first computers. The first computers are preferably being linked to one or more second computers in a control room via a communication network. The control room can be close or remote from the movable electrolysis plant. It is preferably close to the movable electrolysis plant.

Said first computer(s) is/are (a) computer(s) which take(s) care of the control and safeguarding of the movable electrolysis plant. Preferably, said first computer(s) is/are placed in close proximity of the movable electrolysis plant, i.e. in the same location as the plant. Said second computer(s), via which the plant parameters can be analyzed and monitored and the plant according to the present invention controlled, preferably by one or more qualified operators, preferably chlorine operators, is/are placed in a control room which is remote from the plant. The control room can be remote from the movable electrolysis plant, but still on the same production site as the plant. The control room can also be at a different site which can be located in the same country, but also in another country or even on another continent. The communication network through which the first and second computer(s) are linked can for instance be the Internet. Alternatively, the communication network can be an extranet or an intranet.

Said sensors on said skids are part of a monitoring system conventionally used in the art for monitoring the performance of an electrolysis plant. A suitable monitoring system has, for instance, been described in US 6,591,199. The movable electrolysis plant according to the invention is

advantageously built as follows: the support mounted electrolysis module and the support mounted module for a treatment of the electrolyte are advantageouly assembled in the same container or in separate containers on a first site, and transported, preferably by road, to a second site.

The movable electrolysis plant according to the invention is preferably built as follows: the support mounted electrolysis module and the support mounted module for a treatment of the electrolyte are preferably assembled in separate containers on a first site and transported, preferably by road, to a second site.

In a second embodiment, the invention relates to a movable electrolysis plant for electrolysis of a brine into a depleted brine, containing at least one electrolysis module and at least two different support mounted modules for the treatment of the brine and/or of the depleted brine, wherein the electrolysis module and the treatment modules are connected to each other allowing the operation of the plant to be started with only one treatment module or with any combination of two or more treatment modules, and allowing at any time one of the treatments to be switched off and/or an additional treatment to be added, and/or the order of the treatments to be modified.

In a third embodiment, the invention relates to the use of a movable electrolysis plant comprising at least one electrolysis module mounted on a support which can be moved as a whole, and optionally at least one module for a treatment of the cell electrolyte mounted on a support which can be moved as a whole for chlorine production.

In a fourth embodiment, the invention relates to a process for chlorine production comprising electrolyzing an electrolyte in the electrolysis module of the movable electrolysis plant according to the invention wherein the electrolyte is a brine, and preferably a sodium chloride brine.

In that fourth embodiment, the electrolyser of the electrolysis module is advantageoulsy a membrane type electrolyser, the anolyte in the electrolysis module is advantageoulsy a sodium chloride brine, and the catholyte in the electrolysis module is advantageoulsy is an aqueous solution of sodium hydroxide.

In that fourth embodiment, the sodium chloride brine is preferably a brine selected from the group consisting of a depleted brine from an process for manufacturing chlorine, a brine from an epoxide manufacturing process, preferably ethylene oxide, propylene oxide, butylene oxide or epichlorohydrin, and more preferably epichlorhydrin, a brine from an epoxide derivative manufacturing process, preferably epoxy resin, a brine from a process for manufacturing a chlorinated organic product, preferably 1 ,2-dichloroethane or 1,2-dichloroethylene, and more preferably 1 ,2-dichloroethane, a brine from a process for manufacturing a monoisocyanate or a polyisocyanate, preferably 4,4'-methylenediphenyl diisocyanate (MDI), toluene diisocyanate (TDI) or hexamethylene-l,6-diisocyanate (HDI), a brine from a process for manufacturing a polycarbonate, preferably 2,2-bis(4-hydroxyphenyl)propane polycarbonate (bisphenol A polycarbonate), and any mixture thereof.

In that fourth embodiment, the brine has preferably been treated in at least one of the support mounted brine treatment module of the movable electrolysis plant, more preferably prior to electrolysis in the support mounted electrolysis module.

In that fourth embodiment, the process for chlorine production preferably comprises electrolysing an entering brine into a depleted brine, comprising feeding at least one first vessel intermittently with a brine, subjecting this brine to at least one treatment in order to obtain the entering brine, feeding at least one electrolyser of the electrolysis module continuously with the entering brine in order to obtain the depleted brine, and withdrawing continuously the depleted brine from said electrolyser.

The movable chlor-alkali electrolysis plant according to the invention presents the advantage that it can be used as such without separation from its support. This allows reducing greatly the efforts to be made for its installation before use.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

Figures 1 to 3 are intended to illustrate the invention without, however, limiting it.

Figure 1 is a top view and Figure 2 is a side view of an example of the movable electrolysis plant according to the invention. The plant is intended for the production of chlorine by membrane electrolysis of a brine, preferably a sodium chloride brine. The plant comprises one electrolysis skid (I) and one brine treatment skid (II). Both skids are 11.55 m long, 1.00 m wide and 2.20 m tall. They are installed on a concrete floor and separated by a metallic duckboard (III). Figure 2 shows that when in place both skids and the duckboard can be covered by dismountable roofs (IV) fitted with open windows (V).

The support mounted electrolysis module of Figure 1 comprises an electrolyser (1), one tank for brine (2) and one tank for caustic soda (3), pumps (4,5) for feeding the anodic compartment of the electrolyser (not represented) with the brine and pumps (6,7, 44) for feeding the cathodic compartment of the electrolyser (not represented) with the caustic soda , and for adding water to the caustic soda, heat exchangers for heating the brine (8) and the caustic soda (9), hydraulic guard for the anodic (10) and the cathodic (11) compartment of the electrolyser, a heater (12) for hot water production, a current rectifier (13), an electrical cabinet (14) for connecting the rectifier to the source of electrical current and an instrument cabinet (15) for the junction boxes and a unit for chlorine and/or chlorate removal (16).

The support mounted treatment module of Figure 1 comprises one solid salt supply system (17), one saturator (18), one vessel for storing a saturated brine (19), one vessel (20) for adjusting the pH of a brine less concentrated in salt which is to be saturated, one decarbonator (21), one vessel (22) for adjusting the pH of a saturated brine which is to be submitted to a removal of iron and aluminium, one vessel (23) for adjusting the pH of a saturated brine which is to be submitted to a removal of divalent metals, one vessel (24) for storing the brine which is to be fed to the electrolyser, one anthracite filtration system (25) for removing low size solid particles, one filtration column (26) for removing iron and aluminum, two ion-exchange resin columns (27,28) for removing calcium and magnesium, one filtration system (29) for removing ion-exchange resin particles, pumps for circulating the brine between the various vessels, columns and filtration system (30-39) and for adding pH adjusting agents (40-43).

In Figure 1, distances (a), (b), (c), (d), (e) and (f) are respectively of 1.00 m, 2.00 m, 0.66 m, 0.88 m, 1 1.55 m and 7.50 m.

Figure 3 is a top view of two containers placed side by side and in which an electrolysis module and a treatment module are assembled.

The support mounted electrolysis module of Figure 3 comprises an electrolyser (1), one tank for brine (2) and one tank for caustic soda (3), pumps (4,5) for feeding the anodic compartment of the electrolyser (not represented) with the brine and pumps (6,7) for feeding the cathodic compartment of the electrolyser (not represented) with the caustic soda , heat exchangers for heating the brine (8) and the caustic soda (9), a hydraulic guard for the cathodic (10) compartment of the electro lyser, a heater (11) for hot water production, a current rectifier (12), an electrical cabinet (13) for connecting the rectifier to the source of electrical current and an instrument cabinet (14) for the junction boxes and a unit for chlorine and/or chlorate removal (15).

The support mounted treatment module of Figure 3 comprises one solid salt supply system (16), one saturator (17), one vessel for storing a saturated brine (18), one vessel (19) for adjusting the pH of a brine less concentrated in salt which is to be saturated, one decarbonator (20), one vessel (21) for adjusting the pH of a saturated brine which is to be submitted to a removal of iron an aluminium, one vessel (22) for adjusting the pH of a saturated brine which is to be submitted to a removal of divalent metals, one vessel (23) for storing the brine which is to be fed to the electrolyser, one anthracite filtration system (24) for removing low size solid particles, one filtration column (25) for removing iron and aluminum, two ion-exchange resin columns (23,27) for removing calcium and magnesium, one heat exchanger (45) for heating the brine before the ion- exchange resin columns, one filtration system (28) for removing ion-exchange resin particles, pumps for circulating the brine between the various vessels, columns and filtration system (29-38) and for adding pH adjusting agents (39- 42).

In Figure 3, distances (a), (b), (c) and (d) are respectively of 11.55 m, 2.20 m, 0.88 m and 0.91 m.

In Figure 3, arrows (A), (B), and (C) designate the entrances of the containers, double-arrows (D) and (E) designate the passage-ways between the containers.

In Figure 3, both containers are about 12.2 m long, about 2.5 m wide and about 3.1 m tall.