Abstract:
A chemical generator having inlets for receiving multiple reactant and water streams; a dilution chamber; a reaction chamber operably connected to the inlets and to the dilution chamber; an eductor operably receiving the water stream from the one of the inlets and communicating with the reaction chamber for drawing first and second reactant streams into the reaction chamber for mixing. Float control valves interrupt the water stream to the eductor when desired amounts of the first and second reactant streams have entered the reaction chamber, the eductor drawing the activated solution of first and second reactant streams from the reaction chamber into the dilution chamber. The float control valves limit the residence time of the first and second reactants in the reaction chamber and selectively interrupt flow of the water stream into the dilution chamber.

Description:
RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 60/187,898, filed Mar. 8, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of chemical generation, and more particularly but not by way of limitation, to the generation of chemicals such as chlorine dioxide using hydrologic systems. 
     BACKGROUND OF INVENTION 
     Chemical generation systems and methods often involve complex equipment and abundant energy sources to produce the quantity, quality and concentration of the chemical. Such generators are often expensive and bulky so that the end-user must rely on a commercial generation source to produce the chemical needed which involves both transportation and storage costs and concerns. In the case of sensitive chemicals, such as chlorine dioxide, commercial generation is not usually an acceptable solution for consumers. Chlorine dioxide is a widely used sanitizer in a number of fields such as food processing and water treatment. Some recent approvals by the Food and Drug Administration have made chlorine dioxide a popular choice for sanitizing fruits, vegetables, and seafood. Since chlorine dioxide gas is explosive in nature and cannot be safely transported, it should be generated on-site. 
     A common method for the generation of chlorine dioxide is the acidification of chlorite or chlorate salts. In food related uses, chlorite salts prevail because of their ability to break down into non toxic by-products. Among acids, any food grade acid, including phosphoric, hydrochloric or citric acid, can be used for this purpose. 
     Chlorine dioxide generation is most efficient when the precursors are mixed as concentrates. The optimum pH for the reaction is between 2 and 3. At pH values higher than 3, the reaction is not very efficient. On the other hand, at pH values lower than 2, unwanted by-products may be formed. Typically, a 1 to 5 percent chlorite solution is mixed with a selected acid to generate chlorine dioxide. Mixing of the acid with the precursor (chlorite or chlorate) ion is referred as “activation.” The time between mixing of the precursors and dilution of the activated mixture is known as the “activation time.” To achieve good efficiency of chlorine dioxide generation, 1 to 10 minutes of activation time is usually recommended. This is the time that must lapse before the concentrate is diluted to the target usage concentration. For most sanitary and odor removal applications, the usage concentration typically falls between 1 to 600 ppm of activated product so the product is usually diluted to a concentration within this range. As an alternative to dilution, the concentrate can be metered directly into a flowing water stream; or a batch of concentrate can be dumped directly into a larger water system, such as a vegetable flume, a water storage vessel or a cooling tower, to attain and maintain the proper level of chlorine dioxide concentration. 
     Mixing of precursors for the production of chlorine dioxide can be accomplished using automated systems. There are several commercial companies that manufacture acid/sodium chlorite generators, such as Belazon Incorporated and Alldos Corporation. However, all commercially available generators known to the marketplace are electrically powered, and all such commercially available generators utilize high cost electronic control logic. 
     There is a need for a chemical generator that is non-electric, can be installed to operate in remote locations where electrical power is unavailable, can store a reasonable supply of the generated chemical, and is inexpensive to manufacture and maintain. 
     SUMMARY OF THE INVENTION 
     The present invention provides a chemical generator having inlets for receiving multiple reactant and water streams; a dilution vessel; a reaction chamber operably connected to the inlets and to the dilution vessel; and an eductor operably receiving the water stream from the one of the inlets and communicating with the reaction chamber for drawing first and second reactant streams into the reaction chamber for mixing. Float control valves are provided for interrupting the water stream to the eductor when desired amounts of the first and second reactant streams have entered the reaction chamber, with a second eductor drawing the mixture of first and second reactant streams from the reaction chamber into the dilution vessel. The float control valves also limit the time the first and second reactants reside in the reaction chamber and interrupt flow of the water stream into the dilution vessel. 
     The chemical generator is operated in the following sequence: i) first and second chemicals are selectively educed into the reaction chamber; ii) the first and second chemicals are permitted to react for a pre-set time to produce the required product concentration; iii) the generated product is transferred into the dilution vessel; and iv) the generated product is diluted to a pre-set concentration. The chemical generator is particularly suited to generate a chlorine dioxide solution at ready-to-use concentrations of between about 1 to 600 ppm in a safe manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a chemical generator vessel that is constructed in accordance with the present invention. 
         FIG. 2  is an exploded, perspective view of the generator vessel of  FIG. 1 . 
         FIG. 3  is a top plan view of a chemical generator platform constructed in accordance with the present invention and adapted to cooperate with the generator vessel of  FIG. 1 . 
         FIG. 4  is a perspective view of the chemical generator vessel of  FIG. 1 , showing the reaction chamber, eductors and reactant sources without the chemical generator platform of  FIG. 2 . 
         FIG. 5  is a cross-sectional view of one of the eductors of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of one of the valves and attached floats of the chemical generator of  FIG. 2 . 
         FIG. 7  is a cross-sectional view of the needle valve of the chemical generator of  FIG. 2 . 
         FIG. 8  is a schematic of the chemical generator of  FIG. 1  depicting one step in the generation of chlorine dioxide. 
         FIG. 9  is a similar schematic to that of  FIG. 8  depicting the next step in the generation of chlorine dioxide. 
         FIG. 10  is a similar schematic to that of  FIG. 9  depicting the next step in the generation of chlorine dioxide. 
         FIG. 11  is a similar schematic to that of  FIG. 10  depicting the next step in the generation of chlorine dioxide. 
         FIG. 12  is a similar schematic to that of  FIG. 11  depicting the next step in the generation of chlorine dioxide. 
         FIG. 13  is a similar schematic to that of  FIG. 12  depicting the next step in the generation of chlorine dioxide. 
         FIG. 14  is a diagrammatical flow chart of the sequence of operation of the chemical generator depicted in  FIGS. 8–13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in general and particularly to  FIG. 1 , shown therein is a chemical generator vessel  10  constructed in accordance with the present invention. While the present invention will be described in relation to the embodiment shown in the appended drawings, the applicants do not consider their invention to be limited to that shown, and it will be understood that the present invention can be adapted to other embodiments. 
     The chemical generator  10  has an open top cylindrical dilution vessel  12  with a bottom  14  and is constructed of a material suitable to contain the activated solution that is generated therein. Typically, the chemical generator  10  preferably will be a tank of about 7 gallons, an amount which will usually maintain a proper depth for operation of logic function floats and other components described hereinbelow. Of course, the dimensions and capacity can be adjusted as required for a particular installation. 
     The chemical generator  10  serves several purposes, including: holding the activated solution; serving as a dilution vessel; and providing mounting surfaces for the components of the chlorine dioxide generation system. The latter mentioned feature is most useful as the mounting of valves and plumbing on the chemical generator  10  is particularly economically advantageous. As will be clear hereinbelow, the height dimension of the chemical generator  10  is determined such that an adequate water level is maintained for proper float functioning. It will also become clear herein that, since the operational liquids only contact non-moving parts, all critical contact areas can be made of a highly chemical resistant plastic such as PVC, CPVC, PVDF, Kynar®, Teflon®, Carilon® or of a highly resistant metal such as some types of stainless and titanium alloys. 
     The chemical generator  10  has a cylindrical lip  15  supported at the top of the cylindrical vessel  12  that forms a support shoulder  16  as shown in  FIG. 2 . A lid member  18  is dimensioned to fit over the support shoulder  16 . The chemical generator  10  has a water or diluent inlet  20  to receive water via an appropriate conduit (not shown) from a local water source, such as a municipal water supply that is typically pressurized at about from 25 to 80 psig. Of course, the inlet pressure can be established at any desirable value by pressure reducing or pressure elevating pumps (not shown) as may be necessary. Preferably, an inlet water pressure of between 30 to 50 psi will be available for optimum and safe generation. The motive force of water delivered to the water inlet  20  operates the floats, valves, eductors and needle valves described hereinbelow. 
     The chemical generator  10  has a first inlet  22  with an orifice to receive a first reactant stream for a first reactant source and a second inlet  24  with an orifice to receive a second reactant stream for a second reactant source. The chemical generator  10  also has an outlet  26  to which is connected a product tube  28  disposed within the chemical generator  10  and which extends below the level of a resultant reactant product  30  produced by the present invention. The outlet  26  via the product tube  28  provides for the removal of the resultant reactant product  30  from the bottom of the chemical generator  10  via the product tube  28  that has its proximal end positioned near the bottom  14 . 
     The outlet  26  is connected via a product conduit  32  to a user valve  34  to which is connected a user outlet  36 , both the user valve  34  and the user outlet  36  supported by support ribs  38  which extend upwardly from the lid  18 . A support portion of the support ribs  38  serves as a support plate to which the user valve  34  is attached via an attaching member not separately designated. 
     A cylindrically shaped equipment platform  40 , shown in  FIG. 3 , is dimensioned for support on the cylindrical lip  15  of the chemical generator  10 . The equipment platform  40  has a central opening  42 , for access, and a cylindrically shaped reaction chamber  44  extends through, and is supported in, another opening in the equipment platform  40 . The reaction chamber  44  is a vacuum tight chamber that acts as a container for receiving the first and second reactants and retaining the reactants for a determined reaction time. 
     The equipment platform  40  has a first eductor  46 , shown in  FIG. 4 , which allows fluid to flow through the eductor in the direction indicated by arrow  48 . Fluid passing through the first eductor  46 , as shown in  FIG. 5 , causes a pressure differential to develop. The pressure differential causes fluid to move in an attached conduit in the direction of arrow  50 . In fluid communication with the first eductor  46 , as shown in  FIG. 2 , is a first valve  52 . The first valve  52  is known as a normally closed valve. The valve can be a magnetically coupled, mechanically actuated valve, such as the Dema AquaMaster™ series manufactured by Dema Engineering Company (10020 Big Bend Blvd. St. Louis, Mo. 63122) which have flow ratings of 0.5 to 6 gallons per minute at 40 psi. or a similar mechanically float-actuated valve by Hydro® Systems (3798 Round Bottom Road, Cincinnati, Ohio 45244) which have valves with flow rates from 4.5 to 44 gallons per minute. If a magnet is used, the magnet is attached to a moving device that actuates the opening and closing of the valve. The magnetic field that is produced as a result of the magnet movement, positions the valve pilot armature in an on or off position. Therefore, various float parameters such as the shape, size and density, as well as the unique plumbing features are the determining factors involved in the construction of these units. Toilet tank valves and water tank fill valves can also be adapted to perform the required functions. Generally, the first valve  52  operates by an up and down movement which is well understood by those skilled in the art. 
     Attached to the first valve  52  is a first float  54  shown in  FIG. 2 . The first float  54  is specially built to trip the first valve  52  at a specific water level and is a short, medium to large (1.2″ to 6″ diameter) diameter float. The first float  54  is of sufficient weight that when the fluid level is low the first valve  52  trips to an open condition and when the fluid level is high the first valve  52  trips to an closed condition. The relationship between the first float  54  and the first valve  52  is such that the valve will go from a closed to an open position when the fluid level drops in the dilution vessel or chamber  12  is equal to the amount of fluid that is displaced by the first float  54 , for example, an 8.86 cm diameter float displaces 56.0 grams of water per cm of float length. In order to get the 368 grams of float weight needed to trip the first valve  52 , the first float  54  has to be out of the water 6.5 cm beyond neutral buoyancy. The first float  54  is made slightly heavier than a 1.0 density so that the first float  54  will not float on the surface of the product  30 . The first float  54  is also made somewhat heavier and longer than theory to accommodate variations in the valve springs and take advantage of the valve spring hysteresis phenomenon. The actual first float  54  used measured 8.86 cm in diameter by 11.3 cm in length weighing 724 grams for a density of 1.06. This configuration allows for 75 grams of downward pull and the first float  54  remains submerged. 
     The equipment platform  40  also has a second eductor  56 , shown in  FIG. 2 . The second eductor  56  acts like the first eductor  46  discussed above and is in fluid communication with the second valve  62 . The second valve  62  is placed in an upside down position to facilitate a normally open instead of a normally closed function that is used for the first valve  52 , and all other valves of the present invention. No normally open float actuated valve is commercially available at this time so a normally closed valve such as the Dema Aquamaster™, is turned upside down so that the valve becomes a normally open valve. The second valve  62  is connected to a second float  64  which is a short (4″ to 6″) and wide (4″ to 6″) float and has similar dimensions to the first float  54 . The second valve  62  is open when the fluid level is high and closed when the fluid level is low.  FIG. 6  shows the second float  64  attached to the second valve  62 . The second valve  62  has a spring hanger  66  and a valve seat  68 . When the second float  64  moves up or down, the float activates the spring hanger  66  which in turn seats or unseats the valve from the valve seat  68 , allowing fluid flow past the second valve  62  or stopping any flow past the second valve  62 . 
     The configuration of the second float  64  in relationship to the second valve  62  and spring hanger  66  can be altered even further by increasing the density of the second float  64  within the confines of about 100 grams (approximately 2 cm on a 8.86 cm diameter float) of spring tension that is supplied by the spring before the valve switches to off. This is done in order overcome the added resistance of the reverse second valve  62 . In other words the weight to turn the second valve  62  on is 368 grams and the reverse cycle to turn the second valve  62  off is only 250 grams. The float can be made at a slightly higher density to always exert downward pressure of up to 175 grams when submerged. This allows for fine tuning of the float for the lowest cm of exposed float needed to actuate the valve to the on position. The above configuration has a density of about 1.13 which gives an extra 75 grams (1.34 cm shorter) of downward pull while the float is submerged, which in turn shortens the amount of exposed float needed to reach the critical 368 grams to 5.2 cm. 
     The equipment platform  40  shown in  FIG. 2  shows a third valve  72  connected to a third float  74 . The third float  74  is long, with a small diameter (0.5 to 2.0″). The third float  74  is long and slim so that the third valve  72  will not turn on until the tank is at its lowest level of product in the logic cycle or turn off until the fluid level in the dilution chamber  12  is at the highest level, the level designed to be lower than an overflow fluid cutoff level. The third valve  72  stays open longer than would be anticipated based on the buoyancy of the third float  74  because the third valve  72  is set by a spring or magnet to have a delayed closing. The third valve  72  operates like the first valve  52  discussed above and is in fluid communication with a timing needle valve  76 . The timing needle valve  76 , shown in  FIG. 7 , consists of a needle  80  with an adjustable threaded portion  78  that controls placement of the needle  80  in a flow-line. The adjustable threaded portion  78  in the timing needle valve  76  allows for adjustment of the delay-time (subsequent activation of the reactants in reaction chamber  44 ) activation for the second valve  62  and on through the second eductor  56 . 
     The equipment platform  40  shown in  FIG. 2  shows a fourth valve  82  connected to a fourth float  84 . The fourth float  84  has different dimensions then the first float  54 , the second float  64  and the third float  74  which allows the fourth valve  84  to operate open at a wider range of conditions (for example the ability to be open at the lowest operating fluid level and also at a highest operating fluid level but closed at a predetermined overflow level). The fourth valve  82  operates like the first and third valves  52 ,  72  discussed above and is in fluid communication with the first three valves  52 ,  62 , and  72 . 
     All the floats discussed above actuate the mechanical valves at the predetermined water levels as demanded by the sequence of events during the process. The combination of the mechanical valves and the various float diameters, lengths, sizes, densities and shapes facilitate the control logic functions required to operate the generator, coupled with proper routing of water sequencing as needed to properly operate the water actuated chemical generator. The floats utilized with, the Dema 440 valve discussed above, are specially built to trip the valves at different fluid levels. Each float is of sufficient weight (submerged) when the fluid level is low to trip the valve to an open or closed condition (depending on the valve). For example, the Dema 440 valve actuates from a closed position to an open position with a downward pull of approximately 370±10 grams. The crucial design feature of the float described above displaces only 5.2 cm instead of 6.5 cm of its length before the 368 gram trip point is reached. 
     Floats for the chemical generator  10  are made to the following criteria to fit a tank of only 15 inches in height. Larger tank sizes or finished product concentration needs will require floats of different diameter, length and weight to control the logic functions. 
     The float dimensions used in this are given in the following table: 
     
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Diam- 
                   
                   
                   
                   
                   
                 Exposed* 
               
               
                 Float 
                 eter 
                 Length 
                 Weight 
                 Volume 
                 Density 
                 Wgt. 
                 Length 
               
               
                 # 
                 (cm) 
                 (cm) 
                 (g) 
                 (cc) 
                 (g/cc) 
                 (g) 
                 (cm) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 8.86 
                 11.3 
                 724 
                 684 
                 1.06 
                 40 
                 6.5 
               
               
                 2 
                 8.86 
                 11.3 
                 724 
                 684 
                 1.06 
                 40 
                 6.5 
               
               
                 3 
                 4.23 
                 34.0 
                 606 
                 476 
                 1.27 
                 130 
                 26.5 
               
               
                 4 
                 4.84 
                 32.0 
                 754 
                 588 
                 1.28 
                 166 
                 21.5 
               
               
                   
               
               
                 *Length of weight exposed at 368 g trip point 
               
             
          
         
       
     
     The operation of the chemical generator  10  will be described with reference to  FIGS. 8 through 13 , each of which depicts a step in the generation of chlorine dioxide, and with reference to  FIG. 14  which is a flow chart of these steps. It should be noted that, in general, chlorine dioxide generation is most efficient when the precursors are mixed as concentrates, and the optimum pH for the reaction is between 2 and 3. At pH values higher than 3, the reaction is not very efficient. On the other hand, at pH values lower than 2, unwanted by-products may be formed. 
     A GRAS acid, an acid that is “generally regarded as safe” as defined in the CFR, is mixed with the precursor (chlorite or chlorate ions in a 1 to 5% solution) in what is referred as “activation” to form an activated solution  29 . The time between mixing of the precursors and dilution of the activated solution  29  is known as the “activation time.” 
     To achieve good efficiency of chlorine dioxide generation, 5 to 10 minutes of activation time is usually recommended. This is the time that must lapse before the concentrate is diluted to the target usage concentration. For most sanitary and odor removal applications, the usage concentration typically falls between 1 to 600 ppm of activated product so the product is usually diluted to a concentration within this range. 
     The counter cations for the chlorite and chlorate ions include, but are not limited to sodium, potassium, calcium, magnesium and transition metal ion. The preferred concentration, 1 to 5% solution of sodium chlorite, can be used in combination with one of the following acids: hydrochloric, phosphoric, citric, acetic, sulfuric, perchloric, or nitric. The concentration of the acid is dependent on the initial concentration of the chlorite ion and the activation level required. Any combination of reactants that produce chlorine dioxide can be used, for example, with a 2% sodium chlorite solution typically 75% phosphoric or 33% hydrochloric acid can be used. Another combination is a first reactant of 40% sodium chlorate and 10% hydrogen peroxide and a second reactant of 78% sulfuric acid. The concentration and activation levels of the finished product can be altered by changing the intake orifice  22 ,  24  sizes, precursor chemical concentrations and types, as well as the first and second eductor  46 ,  56  size and the flow volume through the needle valve  76 , as will be discussed below. 
     When the product  30  in the chemical generator  10  drops to a level that the first float  54  activates the first valve  52  then water flows through the first eductor  46 . When water flows through the first eductor  46  in the direction shown by arrow  48 , as shown in both  FIG. 4  and  FIG. 5 , then the first eductor  46  creates a flow, as indicated by the arrow  50 , of air from the reaction chamber  44 . As air is evacuated from the reaction chamber  44 , a vacuum develops in the vacuum tight reaction chamber  44 . The vacuum created in the reaction chamber  44  draws reactants from inlet orifices  22  and  24  that are connected to the sodium chlorite and the acid containers. The reaction chamber  44  provides the protected environment needed for activation before the activated solution  29  is expelled. As shown in  FIG. 12 , when the first valve  52  closes, water ceases to flow through the first eductor  46 . The design of the first eductor  46  used is such that the first eductor  46  allows the venting of any pressure that may be generated from the reaction of the precursors. 
     The combination of the float size, density and length of the float for the first valve  52  coupled with the water flow volume through the first eductor  46 , and the eductor&#39;s efficiency, controls the vacuum on the first and second inlet orifices  22 ,  24  that are individually sized to pass, under vacuum, the proper amounts of precursors (sodium chlorite and acid) into the reaction chamber  44 . The volumes of chlorite and acid educted into the reaction chamber  44  and the total volume of water used by the logic functions determines the final product&#39;s concentration in the dilution chamber  12 . 
     As the level continues to rise, the second float  64  activates the second valve  62  that is coupled to the second eductor  56 , as shown in  FIG. 13 . The second valve  62  is placed in an upside down position, as discussed above, to facilitate a normally open instead of a normally closed function. When the second valve  62  is actuated by a rising fluid level, the activated solution  29 , which is a chlorine dioxide solution, is pulled from the bottom of the reaction chamber  44  as water flows through the second valve  62 . The activated solution  29  is diluted in the dilution chamber  12 . When the second float  64  falls with the falling product  30  level, the second float  64  will pull tension on spring hanger  66  so the valve will seat in the valve seat  68 . This stops the water flow in the flow-line between the second valve  62  and the second eductor  56 . 
     As shown in  FIG. 2 , a third float  74  controls a third valve  72 . The length, density, and diameter of the third float  74  adjusts the fill height required to actuate the function of the third valve  72 . The third float  74  controls the water stream that will be utilized by a timing needle valve  76  in conjunction with the first and second valves  52 ,  62  in preparing the activated solution  29  and in the further dilution of the activated solution  29  in the dilution chamber  12 . The third float  74  is long and slim and will not turn on third valve  72  until the fluid level in the dilution chamber  12  is at its lowest level or turn off third valve  72  until the fluid level in the dilution chamber  12  is at the highest level, the level designed to be lower than a overflow fluid cutoff level. The third valve  72  stays open longer then would be anticipated based on its buoyancy because the third valve  72  is set by a spring or magnet to have a delayed closing. This is an example of another way the hydrologic system of the chemical generator  10  can be adjusted to control the steps necessary to achieve the desired final product. 
     The timing needle valve  76 , as shown in  FIG. 7 , continues to fill the dilution chamber  12  during and after the first eductor&#39;s  46  precursor eduction is complete and the first valve  52  is closed. The motive water ceases to flow through the first eductor  46 , but continues to flow through the timing needle valve  76 . The regulated flow through the timing needle valve  76  controls the time that the combination sodium chlorite and acid are allow to react in the reaction chamber  44 . The time period can be adjusted by changing the tension on an adjustable threaded portion  78  of needle  80  that controls placement of the needle  80  in the flow-line from the water inlet  20 . The timing needle valve  76  allows for proper reaction time for the reactants in the reaction chamber  44  before the flow from the timing needle valve  76  raises the level in the dilution chamber  12  to the point that the second float  64  activates the second valve  62 . 
     As discussed above, the water from the second valve  62  provides motive for the second eductor  56 . The vacuum created by water flow through the second eductor  56  pulls the activated solution  29  from the reaction chamber  44  and dilutes the activated solution  29  with the motive water and discharges the resulting solution into the dilution chamber  12 . Water continues to flow through the timing needle valve  76  and the second eductor  56  until the third float  74  actuates the third valve  72  returning the system to a static state. 
     As shown in  FIG. 2 , a fourth float  84  controls a fourth valve  82  to provide overflow protection for the system. If the system starts to overflow, the fourth valve  82  shuts off all water flow to the system. The fourth valve  82  is on at all times unless an accidental overflow condition is present. The fourth float  84  for the fourth valve  82  is set high in the dilution chamber  12 , and the high level position of the fourth float  84  prevents interference with other valves that are involved in the production cycle of the generator system. The fourth valve  82  is not involved in any of the logic functions needed to generate the resultant reactant product  30 . The fourth valve  82  can be equipped with a safety interlock mechanism that keeps the fourth valve  82  from refilling the dilution chamber  12  until the fourth valve  82  is manually reset. This unit can produce up to about 5 pounds of chlorine dioxide in a 24 hour period. Through the use of an adjuster on the user valve  34 , the user outlet  36  can generate a stream, a spray, or a mist of resultant product  30 . The user outlet  36  can be attached to a separate structure  38  which is fitted to the lid  18  of the chemical generator  10 . 
     The method of the present invention will now be described with relation to  FIGS. 8 through 14  which are flow diagrams of describing the steps involved in the generation of a chemical such as chlorine dioxide. The chemical generation process will be described from the time the motive water is stopped at valve  72 , as depicted in  FIG. 8 . This means that the water level in the dilution chamber  12  is high which would not be the case if there was no product in the dilution chamber  12 , say at the beginning of the process. If that was the case, those skilled in the art would know ways to get the process started, such as filling the dilution chamber  12  with water or resetting the valves. In  FIG. 8 , there is no influx of motive water to the chemical generator  10  thus product concentration is at a preset level. During this step valves  52 , and  72  are closed and the system is reset to a static condition. 
     When product  30  is removed from the dilution chamber  12 , as shown in  FIG. 9 , the product  30  level starts to drop in the dilution chamber  12 . As the product  30  level drops, float  64  activates valve  62 , which closes. Then, as depicted in  FIG. 10 , float  54  activates valve  52 , which in turn opens. 
     Finally, as the product level  30  drops even more, as depicted in  FIG. 11 , float  74  activates valve  72  which opens and allows the motive water to flow into the chemical generator ( 10 ). 
     As  FIG. 11  shows, once the motive water flows into the chemical generator  10  through first valve  52 , the motive water flows on to the first eductor  46  and on to the dilution chamber  12 . As motive water flows through first eductor  46 , the motive water pulls a vacuum on the top of the reaction chamber  44 . This vacuum in turn pulls the precursors from the first and second inlet orifices  22 ,  24  into the reaction chamber  44 . The water that has flown flowed through the first eductor  46  also causes the water level to rise in the dilution chamber  12 . There is a check valve  85  on the reaction chamber that prevents the flow of air into the reaction chamber  44  through second eductor  56  while the first eductor is operational. 
     As depicted in  FIG. 12 , first float  54  activates first valve  52  as the water level raises in the dilution chamber  12 , causing first valve  52  to close. This causes flow through the first eductor  46  to stop. Thus no more chemical precursors flow into the reaction chamber  44 . The timing of all the steps that involve motive water can be adjusted by adjusting the timing needle valve  76  shown in  FIGS. 8–13 . For example, the amount of chemical flowing into the reaction chamber  44  could be reduced if the timing valve  76  was adjusted to speed up the flow rate through the timing valve  76  and the whole generator  10 . In a similar way the activation time can be adjusted, as shown in  FIG. 12 . 
     As depicted in  FIG. 13 , the rising water level activates second float  64  to open second valve  62 . Motive water flows through second valve  62  to the second eductor  56 . The second eductor  56  pulls a vacuum on the bottom of the reaction chamber  44  and pulls the activated solution  29  into the dilution chamber  12 . As explained above, the activation time is related to the fill rate of dilution chamber  12  through the needle valve  76 . At this time the product  30  concentration is at the lowest level but that level starts to rise as activated solution  29  flows into the dilution chamber  12 . 
     As the system is drawn down to activate valve third  72  again the cycle outlined above will repeat. The cycle time is dependent on the setting of the timing needle valve  76  that controls the length of time that the reactants will remain in the reaction chamber  44 . The time for an entire cycle can be as low as 2 minutes and as long as 30 to 40 minutes. The timing cycle is determined by the concentrations of the reactants that are drawn into the reaction chamber  44  and the amount of chlorine dioxide gas yield from the reactants that is desired. Longer reaction times equate to more chlorine dioxide gas. 
     It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been described for purposes of this disclosure, numerous changes may be made which will readily suggest themselves to one skilled in the art and which are encompassed in the spirit of the invention disclosed and as defined in the appended claims.