Patent Document

RELATED APPLICATIONS 
     The present application claims priority from Australian Patent Application Serial No. 2003906872 filed on Dec. 15, 2003. Applicant claims priority under 35 U.S.C. §119 as to said application, and the entire disclosure of that application is incorporated herein by reference. 
     FIELD OF INVENTION 
     This invention covers the production of commercial quantities of hydrogen from the electrolysis of water. 
     PRIOR ART 
     The production of hydrogen and oxygen by electrolysis of water in diaphragm cells has been carried out to produce limited commercial quantities of hydrogen and oxygen. Development of the gasification process for fossil fuels using the water gas and the shift converter reactions produced hydrogen at substantially lower cost that was suitable for major industrial requirements such as in ammonia manufacture and hydrogen for oil refining processes. The emerging interest in the technical requirement for hydrogen without carbon oxides for use in Proton Electrolytic Membrane (PEM) fuel cells in transport vehicles has focused interest in producing carbon free hydrogen from gasification gas. One such project is filtering the gasification gas in ceramic filters in one of the projects of the US Department of Energy. The need for carbon oxide-free hydrogen has revived interest in the electrolysis of water for hydrogen production. 
     The electrolysis of water using diaphragm cells to produce hydrogen and oxygen is a well known art.  FIG. 1  shows a diagram of the best method of operating a conventional diaphragm cell for water electrolysis. The ionic circuit is substantially improved by transferring the anolyte from the anode cells to the cathode cells. The diaphragm remains a major problem in water electrolysis because it increases impedance and makes it difficult to agitate the electrolyte to reduce over-voltage. While it must allow electrons to pass through with the least resistance, the diaphragm must not allow mixing of the oxygen produced at the anode with the hydrogen produced at the cathode. 
     The electrolysis of water using diaphragm cells to produce hydrogen and oxygen is a commercial process with the Knowles and the Stuart cells well established. 
     The commercial methods utilize the diaphragm cell with one electrolyte, usually a 28 to 30 weight percent potassium hydroxide solution. The cells are pressurized up to around 40 bars and the cell operating temperature is up to 150 degrees Celsius. Various configurations of the diaphragm cell are used and different coatings on the electrode surface are applied to reduce the impedance of the cells. The efficiency performance and operating conditions of two of the commercial units reported in the mid-1980s are: 
     
       
         
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
           
               
                   
               
             
             
               
                 The Knowles Cell (The International Electrolytic Plant Co. Ltd.): 
               
             
          
           
               
                   
                 Hydrogen Produced per unit cell, Nm 3 /hr. 
                 2.06 
               
               
                   
                 Current, amperes 
                 4,500 
               
               
                   
                 Voltage, volts 
                 1.9 
               
               
                   
                 Electrolyte, w/v % aqueous KOH 
                 28 
               
               
                   
                 Temperature, C. 
                 80 
               
             
          
           
               
                   
                 Gas Purities 
                 Hydrogen, % v/v 
                 99.75 
               
               
                   
                   
                 Oxygen, % v/v 
                 99.5 
               
             
          
           
               
                   
                 Power Consumption, kwh per Nm 3  Hydrogen 
                 4.14 
               
             
          
           
               
                 The Stuart Cell (Efco-Royce Furnaces Ltd.): 
               
             
          
           
               
                   
                 Hydrogen Produced per unit cell, Nm 3 /hr. 
                 2.4 
               
               
                   
                 Current, amperes 
                 5,250 
               
               
                   
                 Voltage, volts 
                 2.04 
               
               
                   
                 Electrolyte, w/v % aqueous KOH 
                 28 
               
               
                   
                 Temperature, C. 
                 85 
               
             
          
           
               
                   
                 Gas Purities 
                 Hydrogen, % v/v 
                 99.9 
               
               
                   
                   
                 Oxygen, % v/v 
                 99.7 
               
             
          
           
               
                   
                 Power Consumption, kwh per Nm 3  Hydrogen 
                 4.9 
               
               
                   
                   
               
             
          
         
       
     
     In these examples, the Knowles cell has an energy efficiency of about 65 percent while the Stuart cell has an energy efficiency of about 55 percent, excluding energy used for pumping and heating. The conventional diaphragm cells used by the Knowles and Stuart electrolytic cells in water electrolysis result in low energy efficiency and low capacity. The capacity of these diaphragm cells is also limited (10.71 Kilowatts for the Stuart Cell and 8.55 kilowatts for the Knowles Cell) and will not meet the high volume demand for electrolytic hydrogen for fuel cells in transport vehicles. Efficiencies and capacities may have improved in current models of these diaphragm type electrolytic cells as the data above is from the mid-eighties. 
     Further information on industrial water electrolysis is provided in “Industrial Electrochemical Processes” A. T. Kuhn, Chapter 4, D. H. Smith p. 127, Elsevier Publishing Company. 
     D. H. Smith discusses why more energy is required than the theoretical to effect the electrolysis of water. “The theoretical decomposition voltage of water is 1.229 volts. Additional energy is required to produce gaseous hydrogen and oxygen at the electrode surface and to overcome depletion of hydrogen and oxygen ions at the electrode surface as the reaction proceeds. This phenomenon is known as the over-voltage at the electrode. Additional energy is required to overcome the electrical resistance between the anode and cathode electrodes. This is a function of the conductivity of the electrolyte, the distance between the electrodes, and the resistance offered by the diaphragm. Commercial water electrolytic diaphragm cells to produce hydrogen and oxygen need to operate between 1.8 to 2.6 volts to overcome all these resistance”. 
     Efforts to increase capacity in the conventional configuration will result in lower efficiency due to the use of the diaphragm cell. 
     The electrolysis of water to produce hydrogen can only be commercially acceptable if the quality of the hydrogen is suitable for application to proton electrolytic membrane or similar fuel cells if the production rate matches the demand for fuel cell transport vehicles and if the cost of the hydrogen is competitive to hydrocarbon fuels. 
     A simple, safe and low cost electrolytic process to produce hydrogen from water over a wide range of capacity is required to use electricity produced from solar, wind, hydro, and geothermal energies. The capacity required of the electrolytic process will range from a few kilowatts to several hundred thousand kilowatts. 
     The object of this invention is to attempt to provide for at least some of these needs or to at least provide a useful alternative. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one form therefor the invention is said to reside in an electrolytic process to produce hydrogen from water, the process comprising the steps of;
     passing a first electrolyte through a diaphragm-less anode cell to produce oxygen wherein the anode cell has an anode connected to a DC power source and an anode solution electrode;   passing a second electrolyte through a diaphragm-less cathode cell to produce hydrogen wherein the cathode cell has a cathode connected to the DC power source and a cathode solution electrode;   the anode solution electrode connected to the cathode solution electrode by an external conductor; and   applying a DC current from the DC power source to the anode and the cathode.   

     In one embodiment of the invention the first electrolyte and the second electrolyte are the same electrolyte and the step of supplying the first electrolyte to the anode cell comprises supplying the second electrolyte and the step of supplying the second electrolyte to the anode cell comprises supplying the first electrolyte. 
     There may be further included the steps of separating hydrogen from the second electrolyte between the cathode cell and the anode cell and separating oxygen from the first electrolyte between the anode cell and the cathode cell. The step of separating hydrogen and oxygen from the second and first electrolytes respectively may comprise the steps of passing the respective electrolytes through an hydrocyclone and a gas liquid separator. 
     Preferably the electrolyte is water that is acidic or basic and make up water can be added as water or as steam. 
     The DC current may be applied at a steady rate or the current applied may be pulsed. The pulsed DC current may have a frequency up to several thousand pulses per second and an amplitude up to 100 times the average value of the current. 
     The pressure in the anode and cathode cells may be up to 100 bars. 
     Regenerative pumps may be used to minimise the energy required to maintain pressure in the anode and cathode cells. 
     There may be further included the step of applying microwaves to the electrolytes. 
     The anode cells and the cathode cells may be operated at a temperature of up to 200 degrees Celsius. 
     Catalyst ions may be added to the electrolyte to reduce the voltage required to produce the hydrogen and increase the production rate of hydrogen. 
     The anode solution electrodes and the cathode solution electrodes may be coated with a substance to increase the over-voltage of the undesired reactions of the catalyst ions. 
     The anode solution electrodes and the cathode solution electrodes may be shrouded with a non-conductor mesh to retain a stagnant layer of electrolyte on the surface of the solution electrodes to avoid undesired reactions of the catalyst ions. 
     Modifiers such as boric acid may be added to the electrolyte to maintain a good quality and consistency of the electrolyte. Modifiers such as surfactants may also added to the electrolyte to make the surface of the anode and cathode electrodes aerophobic to minimize the formation of gas bubbles on the electrode surfaces. 
     The various electrode surface areas may be increased by grooving, by the use of expanded metal sheets and creating pyramids on the electrode surface. The anode and the cathode surfaces may also be coated with a substance to reduce the over-voltage of the desired reactions on these electrodes. 
     In an alternative embodiment the first electrolyte is an alkaline electrolyte and the electrolytic process in the anode cell to produce oxygen is carried out in an anode circuit and the second electrolyte is an acidic electrolyte and the electrolytic process in the cathode cell to produce hydrogen is carried out in a cathode circuit and the anode circuit and the cathode circuit are kept separate except for the electrical connections. 
     The anode circuit may further include a secondary cathode cell and the cathode circuit may further include a secondary anode cell, the secondary anode cell having a secondary anode and a secondary anode solution electrode, the secondary cathode cell having a secondary cathode and a secondary cathode solution electrode, the secondary cathode and the secondary anode are connected by an external conductor, and the secondary cathode solution electrode and the secondary anode solution electrode are connected by an external conductor, the first electrolyte being passed from the anode cell to the secondary cathode cell to produce hydrogen therein before being recycled to the anode cell and the second electrolyte being passed from the cathode cell to the secondary anode cell to produce oxygen therein before being recycled to the cathode cell. 
     There may be further included the steps of separating oxygen from the first electrolyte before transferring it to the secondary cathode call and separating hydrogen after the secondary cathode cell before being recycled to the anode cell and separating hydrogen from the second electrolyte before transferring it to the secondary anode call and separating oxygen after the secondary anode cell before being recycled to the cathode cell. 
     In an alternative form the invention is said to reside in an electrolytic apparatus to produce hydrogen from water, the apparatus comprising a diaphragm-less anode cell to produce oxygen wherein the anode cell has an anode connected to a DC power source and an anode solution electrode, a diaphragm-less cathode cell to produce hydrogen wherein the cathode cell has a cathode connected to the DC power source and a cathode solution electrode, the anode solution electrode connected to the cathode solution electrode by an external conductor, means to supply a first electrolyte to the anode cell, means to supply a second electrolyte to the anode cell and means to apply a DC current from the DC power source to the anode and the cathode. 
     In one embodiment the first electrolyte and the second electrolyte are the same electrolyte and the means to supply the first electrolyte to the anode cell supplies the second electrolyte and the means to supply the second electrolyte to the anode cell supplies the first electrolyte. There may be further included means to separate hydrogen from the second electrolyte between the cathode cell and the anode cell and means to separate oxygen from the first electrolyte between the anode cell and the cathode cell. The means to separate hydrogen and oxygen from the second and first electrolytes respectively may comprise an hydrocyclone and a gas liquid separator. 
     The means to apply a DC current from the DC power source the DC current may be adapted to supply current at a steady rate or pulsed. 
     The means to supply the first and second electrolytes may be regenerative pumps to minimise the energy required to maintain pressure in the anode and cathode cells. 
     There may be further included means to apply microwaves to the electrolytes. 
     The anode solution electrodes and the cathode solution electrodes may be coated with a substance to increase the over-voltage of the undesired reactions of the catalyst ions. They may be shrouded with a non-conductor mesh to retain a stagnant layer of electrolyte on the surface of the solution electrodes to avoid undesired reactions of the catalyst ions. 
     The cathode and anode surface area may be increased by grooving, by the use expanded metal sheets and creating pyramids on the electrode surface and their surfaces may be coated with a substance to reduce the over-voltage of the desired reactions on these electrodes. 
     In an alternative embodiment the anode cell may be in an anode circuit and the cathode cell may be in a cathode circuit and the anode circuit and the cathode circuit are separate, the first electrolyte in the anode circuit comprising an alkaline electrolyte and the second electrolyte in the cathode circuit comprising an acidic electrolyte. 
     The anode circuit may further include a secondary cathode cell and the cathode circuit may further include a secondary anode cell, the secondary anode cell having a secondary anode and a secondary anode solution electrode, the secondary cathode cell having a secondary cathode and a secondary cathode solution electrode, the secondary cathode and the secondary anode are connected by an external conductor, and the secondary cathode solution electrode and the secondary anode solution electrode are connected by an external conductor, the first electrolyte being passed from the anode cell to the secondary cathode cell to produce hydrogen therein before being recycled to the anode cell and the second electrolyte being passed from the cathode cell to the secondary anode cell to produce oxygen therein before being recycled to the cathode cell. 
     The electrolytic apparatus may further comprise means to separate oxygen from the first electrolyte before transferring it to the secondary cathode call and means to separate hydrogen after the secondary cathode cell before being recycled to the anode cell and means to separate hydrogen from the second electrolyte before transferring it to the secondary anode call and means to separate oxygen after the secondary anode cell before being recycled to the cathode cell. 
     Diaphragm-less Electrolytic Process in Conventional Mode 
     The principle of the application of the cell of the present invention to water electrolysis is shown on  FIG. 2 . Oxygen  23  is produced at the anode cell  11  while hydrogen  24  is produced at the cathode cell  12 . Using a potassium hydroxide electrolyte, the theoretical total cell voltage is 1.229 volts with 0.401 volts at the anode and 0.828 volts at the cathode. If the electrolyte composition, temperature, and electrode area are the same at the anode cell and the cathode cell, the voltages of the anode and cathode cells are proportional to the gaps between the solution electrodes and the anode or cathode electrode. Using the appropriate cell voltage, gaps, temperature, pressure and material on the surfaces of the electrodes will optimize the electrolytic cell efficiency. The other important advantage of the electrolytic cell is that oxygen and hydrogen are produced in separate vessels to avoid the danger of mixing. The electrolytic cell will also have less impedance and deliver high capacity per cell than conventional diaphragm cells. 
     The direct electric current applied to the anode and cathode electrodes is usually a steady current but a preferred embodiment of this invention is to apply a pulsed direct current to the anode and cathode electrodes. The frequency may range up to several thousand cycles per second and the amplitude may range up to 100 times the average of the direct current. The objective of the pulsed current is to achieve the desire result at a lower energy cost. 
     Large surface area contact between the electrodes and the electrolyte can be achieved by the construction of the electrode such as a gauze or expanded metal construction where the electrolyte is passed through the electrode. 
     Adding catalysts and modifiers in the electrolyte would also add to the capacity and means to lower the voltage required in the production of hydrogen by this invention. Catalysts can generally be effective in acid electrolyte. In  FIG. 3 , the catalytic reaction at the anode cell  31  using ferric ions in a phosphoric acid electrolyte may be described as follows:
 
2Fe +++ +H 2 O→2Fe ++ +½O 2 +2H + 
 
2Fe ++ −2e − →2Fe +++ 
 
     To assure high current efficiency when using catalysts that are reversible such as the ferrous-ferric ion example above, the surface of the solution electrode at the anode and the solution electrode at the cathode are covered with non-conductive mesh such as a plastic material, to maintain a stagnant layer of electrolyte on the surface of the solution electrodes. This ensures that the solution electrodes act only as current carriers and do not participate in the anode or cathode cell reactions. 
     The electrolytic cells have to operate at high pressure, about 40 bars to reduce gas bubbles from reducing the active surface area of the electrodes. High temperature in the cells reduce the resistance of the electrolyte to reduce the cell voltage. This adds cost to the capital and operation of the electrolytic cell.  FIG. 3  shows one method of operating the cells at high pressure. The regenerative turbine pumps reduce the power requirement. 
     This invention includes another embodiment where the regenerative pumps  40  and  51  are replaced by microwave units. The anolyte  39  is passed through a microwave unit and circulated to the anode cell to complete the reaction described above at a temperature below the boiling point of the electrolyte. 
     The surface of the electrodes may also be plated or covered with a substance that reduces the over-voltage of the electrode. 
     It is relatively easy and quick to establish the optimum parameters in a large-scale laboratory apparatus as a first step in the commercialization of the electrolytic cell. The parameters include electrode material, area and shape, electrolyte composition including catalysts and modifiers, temperature, and pressure to produce hydrogen at the lowest energy at the highest production rate. A large pilot plant may be suitable to supply commercial quantities of hydrogen for a particular purpose such as supplying hydrogen for cooling of equipment in a large steam turbine power plant, or a unit to supply hydrogen to transport vehicles at a remote location. 
     Commercial Electrolytic Production of Hydrogen 
     The commercial production of hydrogen using the electrolytic cell of the present invention is shown on  FIG. 3 . The electrodes could be of the planar type in a cubical cell container or circular in a cylindrical vessel under pressure. The cells are pressurized and operate near or above the boiling temperature of the electrolyte. Large cells may be provided with mechanical agitators. Anolyte  39  containing the hydrogen ion and oxygen is passed through a turbine  40  to lower the pressure and recover power and then to hydro-cyclones  41  to remove more oxygen dissolved in the anolyte. Oxygen recovered may be discharged to atmosphere or delivered to the oxygen storage. The anolyte is then pumped to the cathode cells  32  where hydrogen gas is produced. The catholyte  50  is passed to a turbine  51  to reduce the pressure and recover energy and then to a hydro-cyclone  55  to recover hydrogen dissolved in the catholyte. A discharge vessel may be installed before the hydro-cyclone. The hydrogen produced is cooled and then passed on to the hydrogen storage for use or for sale. Other means of extracting the dissolved hydrogen such as applying vacuum or using a liquid vortex separator may be used. Hydrogen  62  recovered is delivered to the hydrogen storage. Water is added to the catholyte before it is pumped to the anode cells. Water addition may be controlled by a float valve in the anode pump box. Water may also be added to the anode cells as steam for heating. 
     Heat is required to maintain the cells at the optimum operating temperature of about 100° C. or more. Some of this heat may come from the electrical resistance of the electrolyte but some of the heat must be supplied externally through heating of the electrolyte, heating outside the cells or direct steam injection into the anode and cathode cells. 
     Projections of commercial production capacity and electrode sizes of the electrolytic cell of the present invention are shown on Table 2. Efficiencies are based on 10% consumed by pumps and heating and an electrolysis voltage of 1.41335 volts. These projections need to be confirmed in pilot plant tests but are indicative of the efficiency and capacity of the electrolytic process to produce hydrogen. 
     Commercial Production of Hydrogen Using Unipolar Electrolysis 
     The second major portion of this invention is the production of hydrogen from water using unbalanced electrolysis or unipolar activation as a means to reduce the energy consumption. 
     According to W. Latimer&#39;s electromotive data, hydrogen is produced at a reference voltage of zero at the cathode in an acid circuit while oxygen is produced at a reference voltage of −0.401 volts at the anode in an alkaline circuit. If one electrolyte be it acid or alkaline is passed through the primary anode and primary cathode cells, the theoretical voltage required to produce the hydrogen and oxygen is 1.229 volts. 
     Based on classical concept, a solution is always in electronic equilibrium except for very minute layers next to an electrode known as the Helmholtz layer. The number of negative ions equal the number of positive ions. This concept was put to the test using an experimental apparatus similar to the diagram in  FIG. 4 . Separate anode and cathode circuits were set up. The electrodes used are graphite electrodes 50 mm×500 mm×4 mm thick specified as EK72 from National Carbon of the USA. Two electrodes with 3 solution electrodes were used in the anode cell and cathode cell. The gap between the anode and the anode solution electrodes is 2.5 mm and the gap between the cathode and the cathode solution electrodes is also 2.5 mm. The flow diagram in the cathode circuit consisted of a pumping electrolyte to the cathode and the catholyte gravitating to a pump box. A similar flow diagram was used for the anode circuit. The 2 cells were connected electrically by solution electrodes  78  and  79  and an external conductor. 
     After running the apparatus for water electrolysis, the power source was disconnected and a small electric bulb was connected between the anode and cathode. The bulb lit when the electrolytes were circulated again indicating that the electrolytes developed opposite electric potential and this was discharged by the electrodes. The alkaline electrolyte discharged in about 20 seconds while the acid electrolyte discharged over a longer period. When the apparatus was operated with potassium hydroxide through the anode cell and phosphoric acid through the cathode cell with separate pump boxes, the cell voltage for the same cell current was significantly less than when only potassium hydroxide electrolyte was used. Cell voltages were higher than voltages reported for conventional diaphragm cells probably because the unipolar apparatus experiment was not optimized for water electrolysis. 
     The objective of these tests is to determine the power required to pass a certain amount of current through the Electrochemical cell at different concentrations. Another objective is to determine if there is a battery effect after electrolysis has been applied to the electrolyte. 
     The observations are:
         Once the impedance of the cell is overcome, the voltage necessary to pass a certain current through the cell is directly proportional to the current.   The acid solution required a higher voltage to pass the same current as the basic solution.   In the acid solution, the more dilute acid required a lower voltage to pass the same amount of current.   In the basic solution, the more dilute solution required a higher voltage to pass the same amount of current through the cell.   After electrolysis, a residual charge was observed of the same polarity as the impressed voltage.   This residual charge was about the same for the acid and the basic electrolytes but the acid electrolyte seem to hold the potential longer than the basic electrolyte.   The residual voltage after electrolysis seem about half the impressed voltage.   The total voltage impressed on the cell is equal to the voltage across the anode-solution electrode plus the voltage across the cathode-solution electrodes less resistance drop between the power source and the cell.   Voltage required could be further optimised by adjusting the gaps of the electrodes at the anode and at the cathode.   It was observed that the carbon electrodes were attacked by both acid and basic electrolytes.       

     Faraday&#39;s law state that one gram-mole of hydrogen is produced in the primary cell for every faraday (96,500 coulombs) passed through the cell. To reduce the energy required to produce one gram-mole of hydrogen, the voltage must be reduced to as low as possible. To reduce the voltage, the impedance of the system must be as low as possible, and so far, the following are the known and projected factors:
         The voltage impressed on the primary cells is the sum of the voltage between the anode electrode and the anode solution electrode, and the cathode and the cathode solution electrode.   The over-voltage of the electrode surface material where hydrogen and oxygen are evolving must be as low as possible by using the appropriate electrode surface material and adequate mixing of the electrolyte next to the electrode.   The electrical conductivity of the electrolytes must be as high as possible. Low concentration of the acid and high concentration of the alkaline electrolytes are desirable. Measurements show the electrolyte conductivity increases up to the boiling point of the electrolyte.   Large specific surface area and current density on the surface of the electrodes is important and optimum values need to be established. Logically, large current densities require more potential to achieve. Large current densities are necessary for commercial applications.   The hydrogen and oxygen produced at the surface of the electrodes must be removed as quickly as possible to leave the surface of the electrode available for the electrolytic reaction. This is assisted by operating the cells under pressure and also maintaining turbulence at the surface of the electrodes.   The effect of catalysts and modifiers in the electrolyte must be tested to further improve the performance of the electrolytic cell.   The neutralized electrolytes being circulated to the primary cells would help reduce the voltage required for the primary DC power source.       

     A concept for unipolar electrolysis was developed for water electrolysis based on the limited experiments described above. This unipolar concept is described in the diagram shown on  FIG. 5 . 
     The positive terminal of the DC source  95  is connected to the primary anode electrode and the negative is connected to the primary cathode electrode. The solution electrodes electrically connect the primary alkaline electrolyte to the primary acid electrolyte. At the primary anode cell, the following reaction occurs:
 
2OH − −2e − →H 2 O+½O 2 
 
     The alkaline electrolyte  98  exiting from the primary anode cell has excess hydrogen ions so that this electrolyte is positively charged. At the cathode with the acid electrolyte, the following reaction occurs:
 
2H + +2e − →H 2 
 
     The acid electrolyte  108  exiting from the primary cathode cell has excess hydroxyl ions so that this electrolyte is negatively charged. When the electrolytes  98  and  108  are passed through a second set of electrolytic cells, the electrolytes are discharged, causing current to flow from the secondary anode cell  110  to the secondary cathode cell  100  through conductor  101 . This means oxygen is further produced from the secondary anode cell and hydrogen from the secondary cathode cell. The neutralized electrolytes  96  and  113  are recycled to the respective anode and cathode circuits. 
     This unipolar concept to produce hydrogen needs to be confirmed in further tests using optimum conditions such as correct electrode material, electrode area, electrode gap, and cell voltage. Accurate instruments are necessary to measure cell voltage, cell current, temperature and pressure, and the amount of oxygen and hydrogen produced. A diagrammatic presentation of the unipolar commercial production of hydrogen is shown on  FIG. 6 . One separate circuit consists of a set of primary anode cells  120  and another set of secondary cathode cells  132  with an alkaline electrolyte  148  and a separate circuit with an acid electrolyte  149  containing primary cathode cells  126  and secondary anode cells  139 . The projected chemical reactions in the potassium hydroxide alkaline circuit are projected to be:
 
At the anode: 6OH − −6e − → 3/2O 2 
 
At the cathode: 6K + +6OH − +6H + +6e − →6KOH+3H 2 
 
     The projected reactions at the phosphoric acid circuit are:
 
At the cathode: 6H + +6e − →3H 2 
 
At the anode: 2PO −−−   4 +6H + +6OH − −6e − →H 3 PO 4 +3H 2 O+ 3/2O 2 
 
     Water  147  is the only substance consumed in the process and this is simply made up by adding make-up water via a float valve at the anode pump box and cathode pump box or direct addition of water to the anode and cathode cell as steam. The electrodes may be coated with material that is chemically resistant to the electrolytes such as plating with platinum in the acid circuit. The electrodes may be made of conducting material such as metals, graphite and glassy carbon, conducting plastics and ceramic. Special coatings on the electrodes may be used to reduce the over-voltage. Activators and surfactants may be added to the electrolyte. 
     For smaller hydrogen requirements, tangential entry cell in electrolyte series or parallel connections may be used. These tangential entry cylindrical cells have the anode or the cathode electrode for the outer cylinder and an inner cylinder is used as the solution electrode. 
     These type of cells may be suitable for providing hydrogen in strategic locations to provide hydrogen for personal transport vehicles. These cylindrical cells may also suitable for producing hydrogen and oxygen in remote locations using solar cells for electric power. 
     An immediate application of the electrolytic process of this invention is to use off-peak electricity from thermal, nuclear or hydroelectric power plants to produce hydrogen transport fuel cheaper than petroleum fuels such as gasoline or auto-diesel. The water electrolytic system of this invention can be designed to be started and shut-down on demand in stages. As an example shown on Table 1, hydrogen produced for 12 hours by a 114MW off-peak power can supply hydrogen to 3,180 fuel cell cars powered by 75 kw fuel cells operating for 5 hours or 271 buses powered by 250 kw fuel cells operating for 22 hours. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This then generally describes the invention but to assist with understanding reference will now be made to the accompanying drawings in which: 
         FIG. 1  shows a prior art diaphragm cell; 
         FIG. 2  shows schematically the principle of operation of a electrolytic cell according to one embodiment of the invention; 
         FIG. 3  shows a schematic commercial hydrogen production apparatus of the type shown in  FIG. 2 ; 
         FIG. 4  shows schematically the principle of operation of a electrolytic cell according to an alternative embodiment of the invention using unipolar activation; 
         FIG. 5  shows a schematic hydrogen production apparatus of the type shown in  FIG. 4  but including secondary cells; and 
         FIG. 6  shows a schematic commercial hydrogen production apparatus of the type shown in  FIG. 5 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1 : The Conventional Diaphragm Cell in Water Electrolysis 
     The prior art diaphragm cell shown in  FIG. 1  for water electrolysis consists of the cell  1 , the anode electrode  2  and the cathode electrode  3  connected to the DC power source  7 . The anode and cathode electrodes are separated by a diaphragm  4 . In operation, the hydroxyl ions are converted to oxygen  10  and water. The excess of hydrogen ions is the driving force for the hydrogen ions to diffuse through the diaphragm  4  through the catholyte  5  to the cathode electrode  3  where the hydrogen ions are reduced to hydrogen gas  9 . The electronic circuit is from the DC power source to the cathode electrode through the catholyte through the diaphragm through the anolyte to the anode electrode and to the DC power source. The ionic circuit is normally from the anode through the anolyte through the diaphragm through the catholyte to the cathode electrode. This slow diffusion process can be by-passed by mechanically transferring the anolyte to the cathode cell. The reduced catholyte is returned  8   a  to the anode cell. Water  8  is added to the anode cell to replenish the water used in the reaction. 
       FIG. 2 : Principle of the Electrolytic Cell of the Present Invention in Water Electrolysis 
     The electrolytic cell consists of the anode cell  11  and the cathode cell  12 . The diaphragm is replaced by a solution electrode  17  adjacent to the anode electrode  13  and solution electrode  18  adjacent to the cathode electrode  14  and externally connected by a conductor  19 . In operation and using a potassium hydroxide solution  21 , electrons are removed from the anolyte  15  in contact with the anode electrode  13  resulting in the following reaction:
 
2OH − −2e − →½O 2 +H 2 O
 
with the production of oxygen. The anolyte  20  containing the hydrogen ion is transferred to the cathode cell where electrons are added to the catholyte resulting in the following reaction:
 
2H + +2e − →H 2 
 
     The electronic circuit is from the DC power source  22  to the cathode electrode  14  through the catholyte  16  to the solution electrode  18  through the external conductor  19  to the solution electrode  17  at the anode cell  11  to through the anolyte  15  to the anode electrode  13  then to the DC power source  22 . The ionic circuit consists of transferring the anolyte  15  via line  20  to the cathode cell  12  and returning the reduced catholyte  16  via line  21  to the anode cell  11 . Water  25  is added to the anode cell  11  to make up for the water consumed in the reaction. 
       FIG. 3 : 
       FIG. 3  is a schematic presentation of a commercial plant using diaphragm-less electrolytic cell to produce hydrogen from water using either an acid electrolyte or a basic electrolyte. The pressurized anode cell  31  containing the anode electrode  33  and the solution electrode  37  receives reduced catholyte  64  continuously and discharges the anolyte  39  continuously to a turbine pump  40 . Electrons are continuously removed from the anolyte by the anode electrode  33  connected to the DC Power Source  53 . The following reactions occur:
 
With Acid Electrolyte: 2OH − −2e − →½O 2 +H 2 O
 
With Basic Electrolyte: H 2 O−2e − →½O 2 +2H + 
 
     The anolyte containing oxygen and the hydrogen ion is fed into a hydrocyclone  41  or centrifugal separator to remove as much oxygen in the electrolyte to the overflow  42 . The separator  44  separates the liquid from the hydrocyclone overflow to produce the main oxygen stream  45  and electrolyte  46  that joins the hydrocyclone underflow  43  and directed into the cathode pump box  47 . The oxygen may either be released to the atmosphere  48  to maintain the oxygen balance or collected and used as oxidant in fuel cell installations. The anolyte  49  with out oxygen and containing the hydrogen ions is transferred under pressure by turbine pump  51  where the following reactions occur:
 
With Acid Electrolyte: 2H + +2e − →H 2  
 
With Basic Electrolyte: 2H + +2e − →H 2  
 
     The turbine pumps  31  and  51  are used to reduce power consumption in the commercial process. The catholyte  50  containing the hydrogen gas is passed through the turbine pump  51  to the hydrocyclone  55  where the hydrogen gas is separated into the overflow  56  that is directed to separator  58 . The catholyte liquids  57  and  60  are collected into the anode pump box  61  before being pumped by turbine pump  31  to the anode cell  31 . Water  63  is added to the anode pump box  61  to replenish the water used in the reaction. 
     In either acid or basic electrolytes, appropriate metal or compound ions may be used to further reduce the voltage of the cell. The example given in  FIG. 3  is the ferrous-ferric ion and the reaction at the anode with an acid electrolyte is projected as follows:
 
At the Anode with Acid Electrolyte: 2Fe +++ +H 2 O→2Fe ++ +½O 2 +2H + 
 
The Ferrous ion is oxidized to Ferric: 2Fe ++ −2e − →2Fe +++ 
 
     The objective of this commercial process is to produce the quantities of hydrogen shown on Table 1. 
     
       FIG. 4 
     
       FIG. 4  is an embodiment of the diaphragm-less electrolytic cell of the present invention in a unipolar mode where there are separate anode and cathode circuits. There is a separate electrolyte passing the anode cell and a separate electrolyte passing the cathode cell. These electrolytes are connected electrically to the DC power source and through the solution electrodes. Electrons are removed from the anode electrolyte while electrons are added to the electrolyte passing the cathode cell. 
     Water  73  is fed into the anode cell  70  containing the anode electrode  71  and the solution electrode  78 . The oxidized electrolyte is discharged from the anode cell  70  as anolyte  75 . Gas  74  may be produced. Electrons are removed from the anode electrolyte by the DC power source  76  and delivered to the cathode electrode  81  at the cathode cell  80 . Water  83  is fed into the cathode cell  80  and is discharged as catholyte  84  after being reduced. There hydrogen gas  85  is generated. The electronic circuit is from the DC power source  76  to the cathode electrode  81  through the catholyte  82  to the solution electrode  79  to the external conductor  77  to the solution electrode  78  through the anolyte  72  to the anode electrode  71  and to the DC power source  76 . 
     
       FIG. 5 
     
     The concept shown on  FIG. 5  to reduce energy consumption in water electrolysis was developed from tests carried out in our laboratory. The concept has the objective of reducing the energy consumption in the electrolysis of water by reducing the voltage required and utilizing the energy imparted to the electrolytes in the primary cells to produce more hydrogen. 
     The alkaline circuit consists of a storage tank  90  where electrolyte  92  and water  91  are withdrawn by pump  93  and fed to primary anode cell  94  that is connected to DC power source  95 . The primary anode cells solution electrodes are connected by external conductor  97  to the primary cathode solution electrodes. Oxygen is produced at a theoretical voltage of 0.401 volts. The oxidized electrolyte  98  rich in hydrogen ion is passed to an oxygen collector  99  before passing through the secondary cathode cells  100  where the oxidized electrolyte is reduced. Theoretically, a voltage of 0.828 is required to produce hydrogen. Several secondary cathode cells may be connected in series to achieve the required voltage to produce hydrogen. The reduced electrolyte  102  is passed to hydrogen collector  103  before the electrolyte  96  is returned to the alkaline storage tank  90 . 
     The acid circuit consists of a storage tank  104  where electrolyte  105  and water  91  are withdrawn by pump  106  and fed to primary cathode cells  107  that is connected to DC power source  95 . The primary cathode cells solution electrodes are connected by external conductor  97  to the primary anode solution electrodes. Hydrogen is produced at a theoretical voltage of 0.000 volts. The reduced electrolyte  108  rich in hydroxyl ion is passed to a hydrogen collector  109  before passing through the secondary anode cells  110  where the reduced electrolyte is oxidized. Theoretically, a voltage of 1.229 volts is required to produce oxygen. Several secondary anode cells may be connected in series to achieve the required voltage to produce oxygen. The oxidized electrolyte  111  is passed to an oxygen collector  112  before the electrolyte  113  is returned to the acid storage tank  104 . The secondary cathode cell solution electrodes are connected by external conductor  101  to the secondary anode solution electrodes and the secondary cathodes are connected by external conductor  101   a  to the secondary anodes. 
     
       FIG. 6 
     
       FIG. 6  is a diagram of a commercial process to produce hydrogen by unipolar activation using potassium hydroxide electrolyte in one circuit and phosphoric acid in the other circuit. 
     The potassium hydroxide circuit consists of a storage tank  145  provided with heat  152  and make up water  147  controlled by a float valve. Electrolyte  148  is withdrawn by pump  150  and the electrolyte  148  is delivered to the primary anode cells  120  containing the anode electrodes  121  connected to the DC power source  125  and the solution electrodes  122  connected to the external conductor  129 . Oxygen  123  is produced by the reaction:
 
6OH − −6e − → 3/2O 2 +3H 2 O
 
     The oxidized electrolyte  124  exiting the primary anode cell  120  is rich in potassium ions and is passed to the secondary cathode cells  132  containing the secondary cathode electrodes  133  connected by external conductor  136  to the secondary anode electrodes  140  and containing the secondary cathode solution electrodes  134  connected by external conductor  135  to the secondary anode solution electrodes  137 . The theoretical voltage to produce hydrogen is 0.828 volts from the following reaction:
 
6K + +6OH − +6H + +6e − →6KOH+3H 2 
 
     It may require several secondary cathode cells connected in series to generate the hydrogen. The electrolyte  143  is returned to the storage tank  145 . 
     The phosphoric acid circuit consists of a storage tank  146  provided with heat  152  and make up water  147  controlled by a float valve. Electrolyte  149  is withdrawn by pump  151  and the electrolyte  149  is delivered to the primary cathode cells  126  containing the cathode electrodes  127  connected to the DC power source  125  and the solution electrodes  128  connected to the external conductor  129 . Hydrogen  130  is produced by the reaction:
 
6H + +6e − →3H 2 
 
     The reduced electrolyte  131  exiting the primary cathode cell  126  is rich in phosphoric ions and is passed to the secondary anode cells  139  containing the secondary anode electrodes  140  connected by external conductor  136  to the secondary cathode electrodes  133  and containing the secondary anode solution electrodes  137  connected by external conductor  135  to the secondary cathode solution electrodes  134 . The theoretical voltage to produce oxygen is 1.229 volts from the following reaction:
 
2PO −   4 +6H + +6OH − −6e − →H 3 PO 4  +3H 2 O + 3/2O 2 
 
     It may require several secondary anode cells connected in series to generate the oxygen. The electrolyte  144  is returned to the storage tank  146 . 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
             
               
               
             
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Preliminary Projected Hydrogen Production Rate of 
               
               
                 Electrolytic Process of the Present Invention 
               
               
                   
               
             
             
               
                 Assumptions: 
               
               
                   
               
             
          
           
               
                   
                 Ratio of Electrode Depth to Width 
                 1.25 
               
               
                   
                 Current Efficiency, percent 
                 98 
               
               
                   
                 Current Density, amperes per square meter 
                 500 
               
               
                   
                 Theoretical Cell Voltage, volts 
                 1.229 
               
               
                   
                 Ratio of Actual Electrolysis Voltage to theoretical 
                 1.15 
               
               
                   
                 One watt-hour = Joules 
                 3601 
               
               
                   
                 One (1) Std Cubic meter of Hydrogen = moles 
                 44.64286 
               
               
                   
                 One Gram Mole of Hydrogen Requires 
                 96,485 
               
               
                   
                 Efficiency loss to Pumps and heating, percent 
                 90 
               
               
                   
                 One Gram Mole of Hydrogen (H 2 ) = liters at STP 
                 22.4 
               
               
                   
                 Theoretical KWH/normal Cubic meter of hydrogen, kwh 
                 2.69 
               
               
                   
                 Energy Efficiency of Electrolytic Cell, % 
                 76.71 
               
               
                   
                 Energy Efficiency of Electrolytic Cell, % 
                 85.23 
               
               
                   
                 Energy Efficiency of Knowles Cell (4.14 kwh/Nm3), % 
                 65.09 
               
               
                   
                 Energy Efficiency of Stuart Cell(4.9 kwh/Nm3), % 
                 54.99 
               
               
                   
                 Output of Knowles Cell, normal cubic meters of hydrogen per hr 
                 2.06 
               
               
                   
                 Output of Stuart Cell, normal cubic meters of hydrogen per hour 
                 2.4 
               
               
                   
                 Gram moles of H 2  Used by 75 Kw Fuel Cell Car per hour 
                 1,115.92 
               
               
                   
                 Gram moles of H 2  used by 250 kw Fuel Cell Bus per hour 
                 3,719.73 
               
               
                   
                   
               
             
          
           
               
                 Net Power 
                 Gross 
                   
                   
                   
                   
                   
               
               
                 for 
                 Power 
                 Effective 
                 Gram Mols 
                 Std. Meter3 
                 Normal m 3   
                 Energy Eff. 
               
               
                 Electrolysis 
                 Electrolysis 
                 Current 
                 of H 2  prod. 
                 of H 2  prod. 
                 of H 2   
                 KWH per 
               
               
                 Kilowatts 
                 Kilowatts 
                 thru Cell 
                 per day 
                 per day 
                 per hour 
                 N m 3   
               
               
                   
               
               
                 3 
                 3.4 
                 2123 
                 1901 
                 21 
                 0.97 
                 3.51 
               
               
                 5 
                 5.7 
                 3538 
                 3168 
                 35 
                 1.61 
                 3.51 
               
               
                 25 
                 28.3 
                 17688 
                 15840 
                 177 
                 8.07 
                 3.51 
               
               
                 50 
                 56.7 
                 35377 
                 31679 
                 355 
                 16.14 
                 3.51 
               
               
                 75 
                 85.0 
                 53065 
                 47519 
                 532 
                 24.21 
                 3.51 
               
               
                 100 
                 113.4 
                 70754 
                 63358 
                 710 
                 32.27 
                 3.51 
               
               
                 250 
                 283.4 
                 176885 
                 158396 
                 1774 
                 80.69 
                 3.51 
               
               
                 500 
                 566.9 
                 353769 
                 316792 
                 3548 
                 161.37 
                 3.51 
               
               
                 1000 
                 1133.8 
                 707539 
                 633584 
                 7096 
                 322.75 
                 3.51 
               
               
                 10000 
                 11337.9 
                 7075388 
                 6335840 
                 70961 
                 3227.49 
                 3.51 
               
               
                 100000 
                 113378.7 
                 70753883 
                 63358402 
                 709614 
                 32274.88 
                 3.51 
               
               
                   
               
             
          
           
               
                 For 113,379 kw off-peak power, hydrogen produced for 12 
                 31,679,201 
               
               
                 hours, gram moles 
               
             
          
           
               
                 Results: 
               
             
          
           
               
                   
                 For 113,379 KW off-peak power for 12 hrs generating 
               
               
                   
                   
               
               
                   
                 Hydrogen Fuel for the Following Transport Vehicles: 
               
               
                   
                 No. of buses running 22 hrs at 75% Efficiency and 80% 
                 363 
               
               
                   
                 Operating efficiency 
               
               
                   
                 No. of buses running 22 hrs at 56% Efficiency and 80% 
                 271 
               
               
                   
                 Operating Efficiency 
               
               
                   
                 No. of cars running 5 hrs at 75% Efficiency and 100% 
                 4,258 
               
               
                   
                 Operating Efficiency 
               
               
                   
                 No. of cars running 5 hrs at 56% Efficiency and 100% 
                 3,180 
               
               
                   
                 Operating Efficiency 
               
               
                   
                 When comparing fuel cell bus and existing diesel bus, 
               
               
                   
                 include: 
               
               
                   
                 1. Mileage of diesel bus versus fuel cell bus for same amount 
               
               
                   
                 of fuel. 
               
               
                   
                 2. Maintenance cost of diesel bus versus fuel cell bus. 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Projected Commercial Sizes of Electrolytic Cells of the Present Invention 
               
               
                   
               
             
             
               
                 Assumptions: 
               
               
                   
               
             
          
           
               
                   
                 Ratio of Electrode Depth to Width 
                 1.25 
                   
               
               
                   
                 Current Efficiency, percent 
                 98 
               
               
                   
                 Current Density, amperes per square meter 
                 500 
               
               
                   
                 Theoretical Cell Voltage, volts 
                 1.229 
               
               
                   
                 Ratio of Actual Electrolysis Voltage to theoretical 
                 1.15 
               
               
                   
                 One watt-hour = Joules 
                 3601 
               
               
                   
                 One (1) Std Cubic meter of Hydrogen = moles 
                 44.64286 
               
               
                   
                 One Gram Mole of Hydrogen Requires 
                 96,485 
                 Coulombs or ampere seconds 
               
               
                   
                 Efficiency loss to Pumps and heating, percent 
                 90 
               
               
                   
                 One Gram Mole of Hydrogen (H 2 ) = liters at STP 
                 22.4 
               
               
                   
                 Theoretical KWH/normal Cubic meter of hydrogen, 
                 2.69 
               
               
                   
                 kwh 
               
               
                   
                 Energy Efficiency of Electrolytic Cell, % 
                 76.71 
                 Includes energy for heating and 
               
               
                   
                   
                   
                 pumping. 
               
               
                   
                 Energy Efficiency of Electrolytic Cell, % 
                 86.97 
                 Excludes energy for heating and 
               
               
                   
                   
                   
                 pumping. 
               
               
                   
                 Energy Efficiency of Knowles Cell (4.14 kwh/Nm 3 ), % 
                 65.09 
                 Excludes energy for heating and 
               
               
                   
                   
                   
                 pumping. 
               
               
                   
                 Energy Efficiency of Stuart Cell(4.9 kwh/Nm 3 ), % 
                 54.99 
                 Excludes energy for heating and 
               
               
                   
                   
                   
                 pumping. 
               
               
                   
                 Output of Knowles Cell, normal cubic meters of 
                 2.06 
               
               
                   
                 hydrogen per hour 
               
               
                   
                 Output of Stuart Cell, normal cubic meters of 
                 2.4 
               
               
                   
                 hydrogen per hour 
               
               
                   
                   
               
             
          
           
               
                 Net 
                   
                 Effective 
                 Gram 
                 Std. M 3   
                   
                 Energy 
                 Total 
                   
                   
                   
                   
                   
               
               
                 Power 
                 Gross 
                 Current 
                 Mols 
                 of H 2   
                 Normal 
                 Eff. 
                 Area 
                   
                 Area 
               
               
                 for 
                 Power 
                 thru 
                 of H 2   
                 prod. 
                 M 3   
                 KWH 
                 of Electrode 
                   
                 per 
                   
                   
                 Resulting 
               
               
                 Electrolysis 
                 Electrolysis 
                 Cell 
                 prod. 
                 per 
                 of H 2   
                 per 
                 active 
                 No. of 
                 Electrode 
                   
                 Depth 
                 Area 
               
               
                 (Kw) 
                 (Kw) 
                 (A) 
                 per day 
                 day 
                 per hour 
                 N M 3   
                 M 2   
                 Electrodes 
                 M 2   
                 Width M 
                 M 
                 M 2   
               
               
                   
               
               
                 3 
                 3.4 
                 2123 
                 1901 
                 21 
                 0.97 
                 3.51 
                 4.25 
                 2 
                 1.06 
                 0.92 
                 1.15 
                 1.06 
               
               
                 5 
                 5.7 
                 3538 
                 3168 
                 35 
                 1.61 
                 3.51 
                 7.08 
                 4 
                 0.88 
                 0.84 
                 1.05 
                 0.88 
               
               
                 25 
                 28.3 
                 17688 
                 15840 
                 177 
                 8.07 
                 3.51 
                 35.38 
                 10 
                 1.77 
                 1.19 
                 1.49 
                 1.77 
               
               
                 50 
                 56.7 
                 35377 
                 31679 
                 355 
                 16.14 
                 3.51 
                 70.75 
                 10 
                 3.54 
                 1.684 
                 2.11 
                 3.54 
               
               
                 75 
                 85.0 
                 53065 
                 47519 
                 532 
                 24.21 
                 3.51 
                 106.13 
                 10 
                 5.31 
                 1.684 
                 2.11 
                 3.54 
               
               
                 100 
                 113.4 
                 70754 
                 63358 
                 710 
                 32.27 
                 3.51 
                 141.51 
                 20 
                 3.54 
                 1.684 
                 2.11 
                 3.54 
               
               
                 250 
                 283.4 
                 176885 
                 158396 
                 1774 
                 80.69 
                 3.51 
                 353.77 
                 25 
                 7.08 
                 2.38 
                 2.98 
                 7.08 
               
               
                 500 
                 566.9 
                 353769 
                 316792 
                 3548 
                 161.37 
                 3.51 
                 707.54 
                 50 
                 7.08 
                 2.38 
                 2.98 
                 7.08 
               
               
                 1000 
                 1133.8 
                 707539 
                 633584 
                 7096 
                 322.75 
                 3.51 
                 1415 
                 100 
                 7.08 
                 2.38 
                 2.98 
                 7.08 
               
               
                 10000 
                 11337 
                 7075388 
                 6335840 
                 70961 
                 3227.49 
                 3.51 
                 14150 
                 715 
                 9.90 
                 2.814 
                 3.52 
                 9.90 
               
               
                 100000 
                 113378 
                 70753883 
                 63358402 
                 709614 
                 32274.88 
                 3.51 
                 141507 
                 7150 
                 9.90 
                 2.814 
                 3.52 
                 9.90

Technology Category: 8