Dysonian electrolysis


Chlorine. Several methods are available for generating chlorine from HCl. These include electrolysis of metallic chloride solutions, electrolysis of hydrochloric acid, oxidation of hydrogen chloride to chlorine with nitric acid, and oxidation of hydrogen chloride to chlorine using oxygen in the presence of catalysts (Deacon process and the modified Deacon process). As of this writing, only about 60,000 to 65,000 metric tons of CI2 is produced via electrolysis of HCl in the United States annually. Details related to electrolytic and chemical routes for manufacturing CI2 from HCl are given in the hterature (89) (see Alkali and cm ORiNE products, cm ORiNE and sodiumhydroxide).  [c.450]

Most of the magnesium is cast iato iagots or billets. The refining of the molten metal extracted from the electrolysis is performed continuously ia large, stationary brick-lined furnaces of proprietary design (25). Such iastaHations have a metal yield better than 99.5% and negligible flux consumption.  [c.318]

The production of sodium chlorate is very energy intensive requiring between 4950—6050 kWh of electricity per metric ton of sodium chlorate produced (38). More than 95% of the energy is used in the electrolysis step. Increases in energy cost have resulted in use of highly efficient noble metal coated titanium anodes and elimination of the less efficient graphite anodes (39). The by-product hydrogen generated from the cell is also recovered for its fuel value. Advances in electrical bus connection design have also been incorporated to reduce the ceU-to-ceU voltage drop. The use of noble metal anodes requires that hardness, ie, Ca " and Mg " ions, and metals be removed from the sodium chloride brine, hence the brine treatment technology that was originally developed for chlor-alkali industry has now become an integral part of sodium chlorate manufacture (see Alkali and chlorine products). Sodium chlorate manufacturing technology now incorporates a low chloride—chlorate solution manufacture coupled with a chromium removal system, or the use of a crystallizer to produce crystal chlorate as the final project.  [c.496]

Electrolyzer System. The basic criteria for electrolyzer system design is to minimize capital and operating costs. There are about a dozen electrolyzer system configurations being used for sodium chlorate manufacture. These combinations range from high capital/low operating cost to low capital/high operating cost (53—90). Electrolyzer systems have four basic components an electrolysis zone, a reaction zone, a cooling zone, and a circulation zone.  [c.497]

Brine Preparation. Rock salt and solar salt (see Chemicals frombrine) can be used for preparing sodium chloride solution for electrolysis. These salts contain Ca, Mg, and other impurities that must be removed prior to electrolysis. Otherwise these impurities are deposited on electrodes and increase the energy requirements. The raw brine can be treated by addition of sodium carbonate and hydroxide to reduce calcium and magnesium levels to below 10 ppm. If further reduction in hardness is required, an ion-exchange resin can be used. A typical brine specification for the Huron chlorate ceU design is given in Table 6.  [c.499]

Design possibilities for electrolytic cells are numerous, and the design chosen for a particular electrochemical process depends on factors such as the need to separate anode and cathode reactants or products, the concentrations of feedstocks, desired subsequent chemical reactions of electrolysis products, transport of electroactive species to electrode surfaces, and electrode materials and shapes. Cells may be arranged in series and/or parallel circuits. Some cell design possibiUties for electrolytic cells are  [c.70]

Heat Transfer. Cells are designed to minimize electrical power consumption. Heat removal, however, is probably a requirement because of the electrical resistive heating of the electrolyte. Although not economical, this becomes a convenient method of cell temperature control. Heat removal for the commercial electrolysis system is generally carried out by internal or external evaporative cooling circulation of electrolyte through external heat exchangers or internal cooling with coils, jackets, or tubes that may act as electrodes. Each of these methods has found some appHcation ia the commercial context. The standard chemical engineering practice (53,54) is followed for other aspects of cooling system design.  [c.88]

Of the three key criteria that govern electrode processes, ie, product selectivity, electric power usage, and electrolysis system capital, any one of these may become paramount in the cost analysis. Eor instance, power cost is critical in a large-scale process such as the hydrodimerization of acrylonitrile. On the other hand, in smaU-scale high value added processes product selectivity is foremost. An important factor in the design of an electrolysis process is the intensity with which the ceUs can be driven, ie, how high a current density can be used. If it is assumed that the selectivity of the process is independent of current density, then capital and power costs are determining factors. The higher the current density, the less ceU related capital is required. To balance this, the higher current density requires an increased power cost. When these two main factors are computed, a minimum total process operating cost is found at a particular current density. Thus the optimum capital and electrical energy usage point is found, and is used to size ceUs and rectifiers, etc.  [c.95]

Mixing is a unit operation that is practiced widely to meet a variety of process requirements. The specific mixing system design, operating arrangement and power requirements depend largely on the desired form of the intermediate or final products. Mixing is applied to achieve specified results in the following situations creating a suspension of solid particles the blending miscible liquids dispersing gases through liquids blending or dispersing immiscible liquids in each other and promoting heat transfer between a fluid (liquid) and the coil or jacket of a heat exchanging device. The operating characteristics and design configuration of a mixing system are established on the basis of the required energy expenditure to create or approximate a homogeneous fluid system. For example, in producing an emulsion one must supply sufficient energy to "break up" the dispersed phase. In doing so, high shear stresses, which depend on velocity gradients, are developed in the mixing medium. In the zones in which the velocity gradient approaches a maximum, an intensive breaking up of the dispersed phase occurs. Mixing reduces concentration and temperature gradients in the processed system, thus exerting a favorable effect on the overall rates of mass and heat transfers. This applies in particular to dissolving applications, electrolysis, crystallization, absorption, extraction, heating or cooling, and heterogeneous chemical reactions, which proceed for the greater part in a liquid medium. Increased turbulence of the fluid system caused by mixing leads to a, decrease in the fluid s boundary layer thickness. This is derived from a continuous renewal of the surface contact area, resulting in a pronounced rate of increase in heat and mass transfer mechanisms. Regardless which medium is mixed with the liquid, i.e., gas, liquid or solid particles, two basic methods are employed. These arc mechanical mixers, which utilize different types of impellers, and pneumatic mixers, which utilize air or an inert gas to effect mixing. In addition to these designs, mixing also is achieved in normal fluid handling operations, such as in pumps and Jet flows.  [c.435]

The Diaphragm Cell Process. E. A. Le Sueur is credited with the design of the first chlorine cell incorporating a percolating asbestos diaphragm in the 1890s. Brine flows continuously into the anolyte and subsequently through a diaphragm into the catholyte. The diaphragm separates the chlorine Hberated at the anode from the sodium hydroxide and hydrogen produced at the cathode. Failure to separate the chlorine and sodium hydroxide leads to the production of sodium hypochlorite [7681-52-9], NaClO, which undergoes further reaction to sodium chlorate [7775-09-9], NaClO. The commercial process to produce sodium chlorate is, in fact, by electrolysis of brine in a cell without a separator (see Chlorine oxygen acids and salts).  [c.488]

Fluorosulfuric acid may be used to prepare diazonium fluorosulfates, ArN SO.F (44), which decompose on heating to give aryl (Ar) fluorosulfates (36,45). Aryl fluorosulfates are also obtained from arylsulfonyl chlorides and fluorosulfuric acid (35). Alkyl and other organofluorosulfates form during electrolysis of fluorosulfuric acid in the presence of organic species (46,47).  [c.249]

A.queous Jilkaline E.kctrolysis. The traditional process employs potassium hydroxide, KOH, added to the water to improve the conductivity through the ceU. Table 9 shows operating parameters for industrial electrolyzers. All of these systems use a diaphragm to separate the cathode and anode, and keep the product oxygen and hydrogen from mixing. There are basically two types of units offered tank type and filter press. In the tank type, many individual cells are coimected in parallel and fed from one low voltage source. This requires large current flows at low voltage, as well as large transformers and rectifiers. Most commercial electrolyzers are of the filter press type, where cells are stacked and coimected in series. The back side of the cathode for one cell is the anode for the next. This is called a bipolar arrangement. The voltage required to mn the whole module is the sum of the voltages for each individual cell, so low voltages are not needed. However, a series arrangement means that if one cell fails, the module fads. Some units operate at high pressures. This is considered an efficient way to compress hydrogen. Much work is being directed toward improving traditional alkaline electrolysis (157,158). New cell geometries that lower resistances, better electrodes to reduce overvoltages, and better diaphragm materials, so that higher temperatures can be used, are ad. being considered. Higher temperatures enable the electrodes to function more efficiently. Improvements in design and materials are manifested in higher ceU current densities.  [c.425]

The H-D process development, begun in the eady 1980s, is intended for on-site production of dilute alkaline hydrogen peroxide for direct use in the pulp and paper industry. Operated on a pilot scale for many years, it was commercialized in 1991 when improvements in the electrolytic cell design and its current efficiency were achieved (93—100). The newest cell design (94—96) consists of a porous cathode and a platinum-coated titanium anode separated by a diaphragm and an ion-exchange (qv) membrane (see Membrane technology Metal anodes). The diaphragm consists of multiple layers of a porous polypropylene composite, which assures uniform flow of the electrolyte. The electrolyte enters near the base of the anode, and the product solution exits near the base of the cathode. Oxygen gas enters near the top of the porous cathode, and oxygen made through the anodic oxidation of hydroxyl ion exits the top of the anode compartment. The ion-exchange membrane is claimed to control the migration of ions into and out of the cathode compartment, reducing peroxide losses and improving the current efficiency. This latter is claimed to be 95% for the electrolysis.  [c.477]

The chemistry of the process has not changed significantly since its invention. Improvements in the energy efficiency and operation of modern plants have been achieved mainly by improved cell design and better control of the electrolysis through the use of computers to monitor the pot conditions. The electrolysis of an all-chloride mixture in a cell of a new bipolar design has been tested successfully on a small commercial scale with an energy consumption below that of the HaH-Hiiroult cell, but problems encountered in the production of the aluminum chloride feed from bauxite have prevented further development as of this writing (see Aluminumand aluminum alloys).  [c.175]

Electrolysis of Fused Sodium Chloride. Although many cells have been developed for the electrolysis of fused sodium chloride (8,55—60), the Downs cell (3) has been most successful (see Electrochemical processing). In cells in general use by 1945, a single cylindrical anode constmcted of several graphite blocks was inserted through the center of the cell bottom and surrounded by an iron-gau2e diaphragm and a cylindrical iron cathode. In the 1940s, the single anode and cathode were replaced by a multiple electrode arrangement consisting of four anodes of smaller diameter in a square pattern, each surrounded by a cylindrical diaphragm and cathode, as shown in Figure 2. Without increasing the overall cell dimensions, this design iacreased the electrode area per cell, aHowiag iacreased amperage.  [c.165]

Cells for the electrolysis of water are available from several sources. These cells have been described (50,51). Water electrolysis cells must operate at low voltages to achieve good energy efficiency. The theoretical decomposition voltage for hydrogen and oxygen production is 1.23 V. Actual cell voltages are 1.8—2.6 V. Current efficiencies closely approach 100%. Cells are usually of a filter-press design incorporating bipolar electrodes, porous diaphragms or ion-exchange membranes, alkaline electrolyte, KOH, and cataly2ed electrodes. Most cells operate at high pressures, about 3 MPa (30 atm) (52,53).  [c.78]

ICI. In 1981ICI made available the EM 21 cell for the chlor-alkah industry. EM 21 refers to filterpress, monopolar, 21 dm membrane area. This successhil cell was soon modified to the EM 21-SP (superior performance) for general electrolysis processes and particularly electroorganic synthesis by ICI C P Ltd. in the UK. An overall view of the cell is shown in Eigure 11. The cell can be either divided or undivided, and uses internal manifolding of electrolyte which is fed to the cell pack in parallel. Electrodes can be flat plate, bladed, or other enhanced surface area forms. The electrodes are spaced as low as 2 mm, and have a nominal projected area of 0.21 m. Electrical connection is monopolar by a copper bus attached along the long edge of the electrode. The cathode connection is on top and the anode on the underside. Several organic processes have been described as mn in this cell (85,86). ICI has developed this design and other cells for lab to commercial-scale use. Some features of the range of cells available are summarized in Table 3. The benchtop cell version of the EM 21-SP is the EMOl-LC unit. The EB series cells also have internal manifolding and are of a filter press design. However, they are bipolar in electrical connection, allowing a wider range of electrode materials to be used. Therefore, as with the SU cell, lab bench to pilot-plant-scale operation can be carried out in the same cell design. The cost of these cells is in the range of 7,000—15,000 per square meter depending on quantity and materials used. The North American agent for these cells is Electrosynthesis Co., Inc. (Lancaster, New York).  [c.93]

The first industrial production of NHj began in 1913 at the BASF works in Ludwigshaven-Oppau, Germany. The plant, which had a design capacity of 30 tonnes per day, involved an entirely new concept in process technology it was based on the Haber-Bosch high-pressure catalytic reduction of N2 with H2 obtained by electrolysis of water. Modem methods employ the same principles for the final synthesis but differ markedly in the source of hydrogen, the efficiency of the catalysts, and the scale of operations, many plants now having a capacity of 1650 tonnes per day or more. Great ingenuity has been shown not only in plant development but also in the application of fundamental thermod)mamics to the selection of feasible chemical processes. Except where electricity is unusually cheap, reduction by electrolytic hydrogen has now been replaced either by coke/H20 or, more recently, by natural gas (essentially CH4) or naphtha (a volatile aliphatic petrollike fraction of crude oil). The great advantages of modem hydrocarbon reduction methods over coal-based processes are that, comparing plant of similar capital costs, they occupy one-third the land area, use half the energy, and require one-tenth the manpower, yet produce 4 times the annual tonnage of NH3.  [c.421]


See pages that mention the term Dysonian electrolysis : [c.315]    [c.164]   
The science and technology of carbon nanotubes (1999) -- [ c.149 ]