Abstract:
The invention is a method and apparatus for asynchronous blending and supply of chemical solutions. The method of the present invention includes a continuous blending system. This continuous blending system monitors the output and continuously adjusts the blending system to achieve a predetermined formulation of at least a first solution. A centralized monitoring system continuously evaluates the solutions and adjusts the output of the blender as needed to maintain the predetermined formulation of the solution. The system includes at least a first tank system. Any solutions that are delivered from this tank system are also continuously monitored, evaluated, and adjusted as needed by the centralized monitoring system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part of application Ser. No. 10/939,570, filed Sep. 13, 2004, which is a divisional of application Ser. No. 09/468,411, filed Dec. 20, 1999, now U.S. Pat. No. 6,799,883, which is a continuation-in-part of application Ser. No. 09/051,304, filed Apr. 16, 1998, now U.S. Pat. No. 6,050,283. 

   BACKGROUND 
   The combining of two or more fluids (liquids or gases) together to form a defined mixture is fundamental to many industrial processes and commercial products. Typically, this combining is performed in discrete batches. In such a batch process, a quantity of the first fluid is added, followed by a quantity of the second fluid. These two fluids are mechanically mixed, and the resulting mixture is sampled. If necessary, additional quantities of either the first or second fluid can be further added to refine the composition of the mixture. Once the desired composition is achieved, the batch is transferred to an intermediate or end user. 
   This type of batching or blending process is common to many industrial segments including semiconductor processing, pharmaceutical products, biomedical products, food processing products, household products, personal care products, petroleum products, chemical products, and many other general industrial liquid products. 
   Batch processing, or batching, entails many drawbacks and limitations. For example, usually large tanks are required, and since this process can be time consuming, large volume batches are typically prepared at the same time. This large scale requires substantial manufacturing space, and large batch volumes dictate a relatively fixed, and inflexible manufacturing schedule. Large volumes are typically batched in order to overcome the relative imprecision of constituent fluid measurement. Large volumes help to reduce these errors as a percentage of the total batch quantity. Another drawback of batching is that the batch frequently changes its rheological or chemical properties over time. This aging effect is common to many formulations and over time it forces many adjustments to be made prior to sending the composition to the intermediate or end user. Batching can also lead to open, or partially open tanks and to fluids exposed to the atmosphere. This can lead to unwanted chemical contamination, chemical degradation and to microbial contamination. 
   Batching can also lead to difficulties in mixing together the fluid components in large volumes. It is often true that the components can be mixed only with difficulty and require prolonged agitation to become homogeneous. It is also well known that it is common for different levels of a large tank to have different proportionate mixtures of the fluids. It is also true that the large volumes typically committed to batching cause cleaning to be slow, laborious, and difficult to automate. Large volumes of cleaning effluents are produced, leading to issues of waste and contamination. 
   Because of these numerous and substantial shortcomings, and limitations, alternative means of fluid products manufacturing have been sought. One alternative method to batch processing is known as continuous blending. 
   Continuous blending embodies the notion of combining constituent fluids to form a fluid product only as needed or on a demand basis. Essentially, the product is made on demand and at the rate required. The rate required is typically based on the demand of the fluid filling machine packaging the liquid product. 
   The appeal of a continuous blending system, as distinct from a batch processing system, is clear. The ability to eliminate the large batch preparation and holding tanks leads to a small system volume, more product compounding flexibility, faster product formulation turn around, and a substantially lower capital cost. Continuous blending can also yield superior product formula accuracy, and quality, and can eliminate the barrier between fluid products processing, and fluid products packaging. Continuous blending can greatly reduce waste, cleanup time, and effluent volumes. Furthermore, the mixing is simplified and results in far more homogeneous formulations. The product aging effects are also largely eliminated. The real issue is how to build and operate a continuous blending system, with the maximum degree of accuracy, flexibility of use, and versatility of application in a broad range of commercial sectors. 
   Numerous designs for continuous stream blending have been proposed, originating from various liquids processing industries, particularly beverage processing and food processing. These designs have been attempts to develop and market continuous flow proportioning, or blending systems based upon ratio flow control using flow meters, and proportional-integral-derivative (PID) feedback control loops. 
   This is a type of feedback controller whose output, a control variable, is generally based on the error between some user-defined set point, and some measured process variable. Each element of the PID controller refers to a particular action taken on the error.
         Proportional: error multiplied by a gain, K p . This is an adjustable amplifier. In many systems, K p  is responsible for process stability; too low and the PV can drift away; too high and the PV can oscillate.   Integral: the integral of error multiplied by a gain, K i . In many systems, K i  is responsible for driving error to zero, but, to set K i  too high, is to invite oscillation or instability or integrator windup or actuator saturation.   Derivative: the rate of change of error multiplied by a gain, K d . In many systems, K d  is responsible for system response; too high and the PV will oscillate; too low and the PV will respond sluggishly. The designer should also note that derivative action amplifies any noise in the error signal.       

   An example of this type of continuous mixer would be the “Contimix”, which was introduced by H &amp; K Inc., of New Berlin, Wis. In general, these designs rely on regulating a continuous flow of the liquid streams using variable orifice valves or speed controlled pumps, where the flow rate signal from a flow meter, most often a Coriolis mass flow meter, is used to proportionately modulate the flow control device in order to attempt to maintain a desired ratio of flows among the streams, and where another signal representing overall system demand rate is used to proportionately modulate the summed flow of the entire system. 
   Several major design problems are encountered with continuous blending systems, utilizing this flow architecture. First, as the overall output of the system is increased or decreased, the rate of change capability, or response time constant of each stream, will vary one from the next. Thus, with a varying output command signal, each stream reacts at a different rate causing loss of ratio flow, and this is further aggravated by the overshoot or undershoot of each stream as a new set point is reached. Also, as each stream flow rate changes, it can perturb the flow rate of the other stream, or streams causing hunting or oscillations. These common control problems can cause serious loss of blended stream accuracy. Clearly, PID loop controllers are designed to control complex systems that are not inherently designed for stability or ease of control. They deal with the interacting, multiple dependent and independent variables of a flow stream in a non-real time, statistical way and “fight” changing parameters on an historical basis. 
   Still, another problem can arise when a feedback signal change causes the flow to briefly go below or above the permissible range of the flow meter generating, the feedback signal. Even with software or hardware safeties, this can occur, and as will be discussed fully further on, the requirement to maintain flow through a Coriolis mass flow meter within a defined range to achieve satisfactory accuracy is clearly demonstrable. 
   Perhaps, the major problem encountered with these designs, and the PID control architecture arises with the inevitable need to start and stop the flow stream system. When a stop-start event occurs, it is very difficult to bring the system back on-line with balanced, and accurate flow, and blending. This problem has been so persistent, that nearly all installed systems have resorted to the use of a surge tank, of up to several hundred gallons capacity to allow blending flow to continue during brief filler machine stoppages. 
   Even with the use of a surge tank, if blending flow must stop, because of a prolonged filler stoppage, upon re-start the flow streams must either be diverted until correct flow rates are reestablished, or the surge tank must be quite large to allow poorly matched flow ratios to be statistically “diluted” to prevent loss of accurate blending. Either method results in substantial waste, decreased blending accuracy, increased system complexity, and increased system volume, thus depleting the sought after advantages of continuous blending. 
   Therefore, there is a need in the industry for a blending system that addresses all these issues. A blending system is needed that can accommodate continuous changes in demand, while maintaining a highly precise blend accuracy. There is also a need for a blending system that integrates into an overall chemical supply and inventory scheme. A need exists for a blending system that can produce multiple blended solutions and, supply them to multiple end-users, at a high production rate, and with high resolution. A need exists for a blending system that can correct blended product that may have been temporarily stored in vessels, prior to delivery to the end-user. A need exists within the industry for a blending system that has the ability to track and confirm the chemical compositions of the initial components, intermediate blends, and final solution blends. 
   SUMMARY 
   The present invention provides a chemical blending system. The system includes:
         Mixing continuously at least a first chemical stream with a second chemical stream in a blender system. This blender system, comprising a mixing zone in a conduit system, and in a real time controlled manner, form a first solution. In this system, the first chemical stream, and the second chemical stream are continuously introduced into the mixing zone.   Monitoring continuously the first solution, wherein this monitoring results in a first solution output signal that is sent to a centralized monitoring system.   Adjusting continuously the flow rate of the first chemical stream and the flow rate of the second chemical stream to maintain the predetermined formulation of the first solution.   Introduction of the first solution into a first tank system, wherein the first tank system is connected to a chemical distribution system. The first tank system further comprises at least a first tank and a second tank.   Delivering a second solution having a predetermined formulation from the first tank system to the chemical distribution system.   Monitoring continuously the second solution, wherein this monitoring results in a second solution output signal that is sent to the centralized monitoring system.   Delivering the first solution to the first tank system, and adjusting continuously the flow rate of the first chemical stream, and the flow rate of the second chemical stream in order to maintain the predetermined formulation of the second solution.       

   These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein: 
       FIG. 1  is a stylized diagram of an illustrative embodiment of a blending system in accordance with the present invention; 
       FIG. 2  is a stylized diagram of another illustrative embodiment of a blending system in accordance with the present invention; 
       FIG. 3  is a stylized diagram of yet another illustrative embodiment of a blending system in accordance with the present invention; 
       FIG. 4  is a stylized diagram of an illustrative embodiment of a multiple blending system in accordance with the present invention; 
       FIG. 5  is a stylized diagram of another illustrative embodiment of a multiple blending system in accordance with the present invention; and 
       FIG. 6  is a stylized diagram of yet another illustrative embodiment of a multiple blending system in accordance with the present invention. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   As disclosed in application Ser. No. 09/468,411, filed Dec. 20, 1999, herein incorporated by reference, a continuous blender has been developed that addresses the shortcomings of the prior art, as well as others known and unknown to those in the industry. 
   As used with respect to instruments and process monitoring equipment of this invention, the term “continuous”, refers to an uninterrupted, real time monitoring, and adjustment of the formulation of the solutions, including digital controls and algorithms. The use of the term “continuous” is not intended to imply that this system or apparatus must only use analog, or continuous, signals and may not use discrete, or digital, signals to perform this monitoring and adjustment. 
   As used with respect to processes and process equipment of this invention, the term “continuous” is used to describe a process that substantially simultaneously feeds and removes product without interruption of the process and to distinguish this system, and apparatus from a batch system, or apparatus. The use of the term “continuous” is not intended to imply that this system or apparatus will run, or is required to run, endlessly without any interruption. 
   As used herein, the term “centralized monitoring” or “centralized monitoring system,” refers to any system known to one of skill in the art that allows the centralized monitoring of remote sensors, and control of remote process actuators (stitches, valves, flow controllers, etc.). This centralized monitoring system can be located somewhat locally, or can be located at a remote station that is accessed through a server or other data transfer system known to one skilled in the art. This centralized monitoring system may have the capability of being interfaced by field operators, via laptops or other hand held devices, to perform diagnostics or repair operations. Some examples of such centralized monitoring systems are a Distributed Control System (DCS), or a Supervisory Control and Data Acquisition (SCADA) network. 
   The basic principle is to blend a product in a continuous process cycle, while maintaining accuracy and quality in a controlled manner. This is accomplished by varying the supply of the components at injection points using a concentration monitor signature as the main control of each component injection rate. This process blends the production a continuous process cycle by adding components in individual calibrated stages, then controlling these stages with the concentration monitors instrumentation sets. 
     FIG. 1 , is a stylized diagram depicting an illustrative embodiment of a blending system  100  according to the present invention. The blending system  100  comprises a first chemical stream  104 , a second chemical stream  110 , a blender system  113 , a first tank system  117 , and a chemical distribution system  123 . 
   The first chemical stream  104  passes through a first flow control means  105 , which generates a first control means output signal  106 , which is monitored by the centralized monitoring system  124 . The second chemical stream  110  passes through a second control means  111 , which generates a second control means output signal  112 , which is monitored by the centralized monitoring system  124 . The first chemical stream  104  and the second chemical stream  110  are then mixed in the blender system  113 , wherein a first solution  114  is formed. A first solution output signal  115  is generated, which is monitored by the centralized monitoring system  124 . Based on the nature of first solution output signal  115 , the centralized monitoring system  124  will direct either the first flow control means  105  and/or the second flow control means  111  to adjust the flow rate of the first chemical stream  104  and/or the flow rate of the second chemical stream  110 , in order to achieve a predetermined formulation for first solution  114 . Until the centralized monitoring system  124  receives a first solution output signal  115  that indicates that the predetermined formulation for the first solution  114  is within specification, the output stream from blender system  113  is directed to drain  116 . 
   Once the first solution  114  is within specification, is no longer directed toward drain  116 , but is directed instead to a first tank system  117 . As required, a second solution  120  is removed from the first tank system  117  and directed toward the chemical distribution system  123 . As this second solution  120  is removed from the first tank system  117 , a second solution output signal  121  is monitored by the centralized monitoring system  124 . Based on the nature of second solution output signal  121 , the centralized monitoring system  124  will direct either the first flow control means  105  and/or the second flow control means  111  to adjust the flow rate of the first chemical stream  104  and/or the flow rate of the second chemical stream  110 , which will be directed to the first tank system  117 , in order to achieve a predetermined formulation for second solution  120 . Until the centralized monitoring system  124  receives a second solution output signal  121  that indicates that the predetermined formulation for the second solution  120  is within specification, the output stream from the first tank system  117  is recycled  122  back to first tank system  117 . Once the second solution  120  is within specification, it is no longer recycled  122 , but is directed instead to chemical distribution system  123 . Alternately, first solution  114  may bypass  125  the first tank system  117  and be directed toward chemical distribution system  123 . 
   The blender system  113  comprises a mixing zone in a conduit system. The first chemical stream  104  and the second chemical stream  110  are continuously mixed in this mixing zone and controlled in a real time manner as discussed above, thereby forming a first solution  114  with a predetermined formulation. 
   Should there arise a situation where more than one adjustment is required from the blender system  113  simultaneously, for example the chemical distribution system  123  may receive a signal that the second solution  120  is not at the predetermined formulation at the same that it receives a signal that the first solution  114  is not at the predetermined formulation, then the adjustment to the second solution  120  may have a higher priority than the adjustment to the first solution  114 . One embodiment is that the closer that the maladjustment in solution formulation is to entering the chemical distribution system  123 , the higher the priority that that adjustment has. 
   The first chemical stream  104  may be obtained from a first component tank  101 . This first component tank  101  may have a first weighing means  102 , which may generate a first weighing means output signal  103 , which is monitored by the centralized monitoring system  124 . The second chemical stream  110  may be obtained from a second component tank  107 . This second component tank  107  may have a second weighing means  108 , which may generate a second weighing means output signal  109 , which is monitored by the centralized monitoring system  124 . 
   The first tank system  117  comprises at least two tanks, a first tank and a second tank, which are operated either in parallel or in series. These tanks may have a third weighing means  118 , which may generate a third weighing means output signal  119 , which is monitored by the centralized monitoring system  124 . These first and second tanks may have a recirculation system, which may be used to maintain a homogeneous blend within the tanks. Should a deviation arise in the second solution  120  from the predetermined formulation, the time that it will take to adjust the flowrates of either the first chemical stream  104  or the second chemical stream  110  in order to return the solution to the predetermined formulation may be less than about 15 minutes. These first and second tanks may be sized for at least 3 days of constant use by the chemical distribution system. 
   The drain cycle discussed above regarding drain  116  may be designed to take less than 8 seconds, before achieving the target predetermined formulation. The drain cycle discussed above regarding drain  116  may be designed so that less than 1 gallon is directed to the drain before achieving the target predetermined formulation. 
   The blender system  113  may be designed to have a design flow rate of less than about 80 liters per minute. The blender system  113  may be designed to have a design flow rate of less than 1,000,000 gallons per month. The blender system  113  may be designed to have a design flow rate of less than 1,500,000 gallons per month. 
   The predetermined formulation of either first solution  114  and/or second solution  120  may be maintained by the blender system  113  to within an accuracy of greater than about 0.003 wt %. The predetermined formulation of either first solution  114  and/or second solution  120  may be maintained by the blender system  113  to within an accuracy of greater than about 0.01 wt %. 
   The first and/or second solution may be monitored for at least one concentration criteria selected from the following group:
         a) conductivity;   b) sound velocity;   c) density;   d) viscosity;   e) refractive index;   f) turbidity;   g) auto titration; and   h) a manual analytical verification.       

   The first and/or second flow control means  105 ,  111  may control and/or monitor both flow rate and pressure. The first and/or second flow control means  105 ,  111  may monitor temperature. The combined flow rate, pressure and temperature measurements made by the first and/or second flow control means  105 ,  111  may be used to index for temperature during concentration calculations for either the first and/or second solutions  114 ,  120 . 
   The flow rate output signals from the first flow control means  105 , the second flow control means  111 , and the first solution output signal  115 , may be used in conjunction with the first weighing means output signal  103  in order to verify the initial concentration of the contents of the first component tank  101 . The flow rate output signals from the first flow control means  105 , the second flow control means  111 , and the first solution output signal  115 , may be used in conjunction with the second weighing means output signal  109  in order to verify the initial concentration of the contents of the second component tank  107 . 
   The change in the first weighing means output signal  103  as a function in time and the change in the second weighing means output signal  109  as a function of time, may be used to verify the flow rate of the first solution  114 . 
   The change in the first weighing means output signal  103  as a function in time, the change in the second weighing means output signal  109  as a function of time, and the change in the third weighing means output signal  115  as a function of time may be used to verify the flow rate of the second solution  120 . 
     FIG. 2  is a stylized diagram depicting another illustrative embodiment of a blending system  200  according to the present invention. The blending system  200  comprises a first chemical stream  204 , a second chemical stream  210 , a blender system  213 , a first tank system  217 , a second tank system  223 , and a chemical distribution system  229 . 
   The first chemical stream  204  passes through a first flow control means  205 , which generates a first control means output signal  206 , which is monitored by the centralized monitoring system  230 . The second chemical stream  210  passes through a second control means  211 , which generates a second control means output signal  212 , which is monitored by the centralized monitoring system  230 . The first chemical stream  204  and the second chemical stream  210  are then mixed in the blender system  213 , wherein a first solution  214  is formed. A first solution output signal  215  is generated, which is monitored by the centralized monitoring system  230 . Based on the nature of first solution output signal  215 , the centralized monitoring system  230  will direct either the first flow control means  205  and/or the second flow control means  211  to adjust the flow rate of the first chemical stream  204  and/or the flow rate of the second chemical stream  210 , in order to achieve a predetermined formulation for first solution  214 . Until the centralized monitoring system  230  receives a first solution output signal  215  that indicates that the predetermined formulation for the first solution  214  is within specification, the output stream from blender system  213  is directed to drain  216 . 
   Once the first solution  214  is within specification, it is no longer directed toward drain  216 , but is directed instead to a first tank system  217 . As required, a second solution  220  is removed from the first tank system  217  and directed toward the second tank system  223 . As this second solution  220  is removed from the first tank system  217 , a second solution output signal  221  is monitored by the centralized monitoring system  230 . 
   Based on the nature of second solution output signal  221 , the centralized monitoring system  230  will direct either the first flow control means  205  and/or the second flow control means  211  to adjust the flow rate of the first chemical stream  204  and/or the flow rate of the second chemical stream  210 , which will be directed to the first tank system  217 , in order to achieve a predetermined formulation for second solution  220 . Until the centralized monitoring system  230  receives a second solution output signal  221  that indicates that the predetermined formulation for the second solution  220  is within specification, the output stream from the first tank system  217  is recycled  222  back to the first tank system  217 . 
   Once the second solution  220  is within specification, it is no longer recycled  222 , but is directed instead to second tank system  223 . Alternately, first solution  214  may bypass  231  the first tank system  217  and be directed toward second tank system  223 . As required, a third solution  226  is removed from the second tank system  223  and directed toward the chemical distribution system  229 . As this third solution  226  is removed from the second tank system  223 , a third solution output signal  227  is monitored by the centralized monitoring system  230 . Based on the nature of third solution output signal  227 , the centralized monitoring system  230  will direct either the first flow control means  205  and/or the second flow control means  211  to adjust the flow rate of the first chemical stream  204  and/or the flow rate of the second chemical stream  210 , which will be directed to the second tank system  223 , in order to achieve a predetermined formulation for third solution  226 . Until the centralized monitoring system  230  receives a third solution output signal  227  that indicates that the predetermined formulation for the third solution  226  is within specification, the output stream from the second tank system  223  is recycled  228  back to the second tank system  223 . Once the third solution  226  is within specification, it is no longer recycled  228 , but is directed instead to chemical distribution system  229 . Alternately, second solution  220  may bypass  232  the second tank system  223  and be directed toward chemical distribution system  229 . 
   The blender system  213  comprises a mixing zone in a conduit system. The first chemical stream  204  and the second chemical stream  210  are continuously mixed in this mixing zone and controlled in a real time manner as discussed above, thereby forming a first solution  214  with a predetermined formulation. 
   Should there arise a situation where more than one adjustment is required from the blender system  213  simultaneously, for example the chemical distribution system  229  may receive a signal that the third solution  226  is not at the predetermined formulation at the same that it receives both a signal that the second solution  220  is not at the predetermined formulation and a signal that the first solution  214  is not at the predetermined formulation, then the adjustment to the third solution  226  may have a higher priority than the adjustment of the second solution  220 , which may in turn have a higher priority than the adjustment to the first solution  214 . One embodiment is that the closer that the maladjustment in solution formulation is to entering the chemical distribution system  229 , the higher the priority that that adjustment has. 
   The first chemical stream  204  may be obtained from a first component tank  201 . This first component tank  201  may have a first weighing means  202 , which may generate a first weighing means output signal  203 , which is monitored by the centralized monitoring system  230 . The second chemical stream  210  may be obtained from a second component tank  207 . This second component tank  207  may have a second weighing means, which may generate a second weighing means output signal  209 , which is monitored by the centralized monitoring system  230 . 
   The first and/or second tank system  217 ,  223  comprises at least two tanks each, which are operated either in parallel or in series. These tanks may have a third weighing means  218  and/or a fourth weighing means  224 , which may generate a third weighing means output signal  219  and/or a fourth weighing means output signal  225 , which is monitored by the centralized monitoring system  230 . These tanks may have a recirculation system, which may be used to maintain a homogeneous blend within the tanks. Should a deviation arise in either the second solution  220  and/or the third solution  226  from the predetermined formulations, the time that it will take to adjust the flow rates of either the first chemical stream  204  or the second chemical stream  210  in order to return either of the solutions to the predetermined formulation may be less than about 15 minutes. These tanks may be sized for at least 3 days of constant use by the chemical distribution system. 
   The drain cycle discussed above regarding drain  216  may be designed to take less than 8 seconds, before achieving the target predetermined formulation. The drain cycle discussed above regarding drain  216  may be designed so that less than 1 gallon is directed to the drain before achieving the target predetermined formulation. 
   The blender system  213  may be designed to have a design flow rate of less than about 80 liters per minute. The blender system  213  may be designed to have a design flow rate of less than 1,000,000 gallons per month. The blender system  213  may be designed to have a design flow rate of less than 1,500,000 gallons per month. 
   The predetermined formulation of either first solution  214  and/or second solution  220  and/or third solution  226  may be maintained by the blender system  213  to within an accuracy of greater than about 0.003 wt %. The predetermined formulation of either first solution  214  and/or second solution  220  and/or the third solution  226  may be maintained by the blender system  213  to within an accuracy of greater than about 0.01 wt %. 
   The first and/or second solution and/or third solution may be monitored for at least one concentration criteria selected from the following group:
         a) conductivity;   b) sound velocity;   c) density;   d) viscosity;   e) refractive index;   f) turbidity;   g) auto titration; and   h) a manual analytical verification.       

   The first and/or second flow control means  205 ,  211  may control and/or monitor both flow rate and pressure. The first and/or second flow control means  205 ,  211  may monitor temperature. The combined flow rate, pressure and temperature measurements made by the first and/or second flow control means  205 ,  211  may be used to index for temperature during concentration calculations for either the first and/or second solutions  214 ,  220 . 
   The flow rate output signals from the first flow control means  205 , the second flow control means  211 , and the first solution output signal  215 , may be used in conjunction with the first weighing means output signal  203  in order to verify the initial concentration of the contents of the first component tank  201 . The flow rate output signals from the first flow control means  205 , the second flow control means  211 , and the first solution output signal  215 , may be used in conjunction with the second weighing means output signal  209  in order to verify the initial concentration of the contents of the second component tank  207 . 
   The change in the first weighing means output signal  203  as a function in time and the change in the second weighing means output signal  209  as a function of time, may be used to verify the flow rate of the first solution  214 . 
   The change in the first weighing means output signal  203  as a function in time, the change in the second weighing means output signal  209  as a function of time, and the change in the third weighing means output signal  219  as a function of time may be used to verify the flow rate of the second solution  220 . 
   The change in the first weighing means output signal  203  as a function in time, the change in the second weighing means output signal  209  as a function of time, the change in the third weighing means output signal  219  as a function of time, and the change in the fourth weighing means output signal  225  as a function of time may be used to verify the flow rate of the third solution  226 . 
     FIG. 3  is a stylized diagram depicting yet another illustrative embodiment of a blending system  300  according to the present invention. The blending system  300  comprises a first chemical stream  304 , a second chemical stream  310 , a blender system  313 , a first tank system  317 , a second tank system  323 , a third tank system  329 , and an end user  333 . 
   The first chemical stream  304  passes through a first flow control means  305 , which generates a first control means output signal  306 , which is monitored by the centralized monitoring system  330 . The second chemical stream  310  passes through a second control means  311 , which generates a second control means output signal  312 , which is monitored by the centralized monitoring system  334 . The first chemical stream  304  and the second chemical stream  310  are then mixed in the blender system  313 , wherein a first solution  314  is formed. A first solution output signal  315  is generated, which is monitored by the centralized monitoring system  334 . Based on the nature of first solution output signal  315 , the centralized monitoring system  334  will direct either the first flow control means  305  and/or the second flow control means  311  to adjust the flow rate of the first chemical stream  304  and/or the flow rate of the second chemical stream  310 , in order to achieve a predetermined formulation for first solution  314 . Until the centralized monitoring system  334  receives a first solution output signal  315  that indicates that the predetermined formulation for the first solution  314  is within specification, the output stream from blender system  313  is directed to drain  316 . 
   Once the first solution  314  is within specification, it is no longer directed toward drain  316 , but is directed instead to a first tank system  317 . As required, a second solution  320  is removed from the first tank system  317  and directed toward the second tank system  323 . As this second solution  320  is removed from the first tank system  317 , a second solution output signal  321  is monitored by the centralized monitoring system  330 . Based on the nature of second solution output signal  321 , the centralized monitoring system  330  will direct either the first flow control means  305  and/or the second flow control means  311  to adjust the flow rate of the first chemical stream  304  and/or the flow rate of the second chemical stream  310 , which will be directed to the first tank system  317 , in order to achieve a predetermined formulation for second solution  320 . Until the centralized monitoring system  330  receives a second solution output signal  321  that indicates that the predetermined formulation for the second solution  320  is within specification, the output stream from the first tank system  317  is recycled  322  back to the first tank system  317 . 
   Once the second solution  320  is within specification, it is no longer recycled  322 , but is directed instead to second tank system  323 . Alternately, first solution  314  may bypass  335  the first tank system  317  and be directed toward second tank system  323 . As required, a third solution  326  is removed from the second tank system  323  and directed toward the third tank system  329 . As this third solution  326  is removed from the second tank system  323 , a third solution output signal  327  is monitored by the centralized monitoring system  334 . Based on the nature of third solution output signal  327 , the centralized monitoring system  334  will direct either the first flow control means  305  and/or the second flow control means  311  to adjust the flow rate of the first chemical stream  304  and/or the flow rate of the second chemical stream  310 , which will be directed to the second tank system  323 , in order to achieve a predetermined formulation for third solution  326 . Until the centralized monitoring system  334  receives a third solution output signal  327  that indicates that the predetermined formulation for the third solution  326  is within specification, the output stream from the second tank system  323  is recycled  328  to second tank system  323 . 
   Once the third solution  326  is within specification, it is no longer recycled, but is directed instead third tank system  329 . Alternately, second solution  320  may bypass  336  the second tank system  323  and be directed toward third tank system  329 . As required, a fourth solution  330  is removed from the third tank system  329  and directed toward the end user  333 . As this fourth solution  330  is removed from the third tank system  339 , a fourth solution output signal  331  is monitored by the centralized monitoring system  334 . Based on the nature of fourth solution output signal  331 , the centralized monitoring system  334  will direct either the first flow control means  305  and/or the second flow control means  311  to adjust the flowrate of the first chemical stream  304  and/or the flow rate of the second chemical stream  310 , which will be directed to the third tank system  329 , in order to achieve a predetermined formulation for fourth solution  330 . Until the centralized monitoring system  334  receives a fourth solution output signal  331  that indicates that the predetermined formulation for the fourth solution  330  is within specification, the output stream from the third tank system  329  is recycled  332  to third tank system  329 . Once the fourth solution  330  is within specification, it is no longer recycled  330 , but is directed instead to the end user  333 . Alternately, third solution  330  may bypass  337  the third tank system  329  and be directed toward end user  333 . 
   The blender system  313  comprises a mixing zone in a conduit system. The first chemical stream  304  and the second chemical stream  310  are continuously mixed in this mixing zone and controlled in a real time manner as discussed above, thereby forming a first solution  314  with a predetermined formulation. 
   Should there arise a situation where more than one adjustment is required from the blender system  313  simultaneously, for example the end user  333  may receive a signal that the fourth solution  330  is not at the predetermined formulation at the same time that it receives signals that the third solution  326  is not at the predetermined formulation, the second solution  320  is not at the predetermined formulation and the first solution  314  is not at the predetermined formulation, then the adjustment to the fourth solution  330  may have a higher priority than the adjustment of the third solution  326  which may in turn have a higher priority than the adjustment of the second solution  320 , which may in turn have a higher priority than the adjustment to the first solution  314 . One embodiment is that the closer that the maladjustment in solution formulation is to entering the end user  333 , the higher the priority that that adjustment has. 
   The first chemical stream  304  may be obtained from a first component tank  301 . This first component tank  301  may have a first weighing means  302 , which may generate a first weighing means output signal  303 , which is monitored by the centralized monitoring system  334 . The second chemical stream  310  may be obtained from a second component tank  307 . This second component tank  307  may have a second weighing means  308 , which may generate a second weighing means output signal  309 , which is monitored by the centralized monitoring system  334 . 
   The first and/or second and/or third tank system  317 ,  323 ,  329  comprises at least two tanks each, which are operated either in parallel or in series. These tanks may have a third weighing means  318  and/or a fourth weighing means  324 , which may generate a third weighing means output signal  319  and/or a fourth weighing means output signal  325 , which is monitored by the centralized monitoring system  334 . These tanks may have a recirculation system, which may be used to maintain a homogeneous blend within the tanks. Should a deviation arise in either the second solution  320  and/or the third solution  326  and/or the fourth solution  330  from the predetermined formulations, the time that it will take to adjust the flow rates of either the first chemical stream  304  or the second chemical stream  310  in order to return any of the solutions to the predetermined formulation may be less than about 15 minutes. These tanks may be sized for at least 3 days of constant use by the end user. 
   The drain cycle discussed above regarding drain  316  may be designed to take less than 8 seconds, before achieving the target predetermined formulation. The drain cycle discussed above regarding drain  316  may be designed so that less than 1 gallon is directed to the drain before achieving the target predetermined formulation. 
   The blender system  313  may be designed to have a design flow rate of less than about 80 liters per minute. The blender system  313  may be designed to have a design flow rate of less than 1,000,000 gallons per month. The blender system  313  may be designed to have a design flow rate of less than 1,500,000 gallons per month. 
   The predetermined formulation of either first solution  314  and/or second solution  320  and/or third solution  326  and/or the fourth solution  330  may be maintained by the blender system  313  to within an accuracy of greater than about 0.003 wt %. The predetermined formulation of either first solution  314  and/or second solution  320  and/or the third solution  326  and/or the fourth solution  330  may be maintained by the blender system  313 , to within an accuracy of greater than about 0.01 wt %. 
   The first and/or second solution and/or third solution and/or fourth solution may be monitored for at least one concentration criteria selected from the following group:
         a) conductivity;   b) sound velocity;   c) density;   d) viscosity;   e) refractive index;   f) turbidity;   g) auto titration; and   h) a manual analytical verification.       

   The first and/or second flow control means  305 ,  311  may control and/or monitor both flow rate and pressure. The first and/or second flow control means  305 ,  311  may monitor temperature. The combined flow rate, pressure and temperature measurements made by the first and/or second flow control means  305 ,  311  may be used to index for temperature during concentration calculations for either the first and/or second solutions  314 ,  320 . 
   The flow rate output signals from the first flow control means  305 , the second flow control means  311 , and the first solution output signal  315 , may be used in conjunction with the first weighing means output signal  303  in order to verify the initial concentration of the contents of the first component tank  301 . The flow rate output signals from the first flow control means  305 , the second flow control means  311 , and the first solution output signal  315 , may be used in conjunction with the second weighing means output signal  309  in order to verify the initial concentration of the contents of the second component tank  307 . 
   The change in the first weighing means output signal  303  as a function in time and the change in the second weighing means output signal  309  as a function of time, may be used to verify the flow rate of the first solution  314 . 
   The change in the first weighing means output signal  303  as a function in time, the change in the second weighing means output signal  309  as a function of time, and the change in the third weighing means output signal  319  as a function of time may be used to verify the flow rate of the second solution  320 . 
   The change in the first weighing means output signal  303  as a function in time, the change in the second weighing means output signal  309  as a function of time, the change in the third weighing means output signal  319  as a function of time, and the change in the fourth weighing means output signal  325  as a function of time may be used to verify the flow rate of the third solution  326 . 
   Two or more blending systems  300  may be combined, using a single blender system  313 . If two or more blending systems  300  are combined, using a single blender system  313 , the the performance of the chemical blending system  300  with the highest volume usage has priority over the system with the next highest volume usage. If two or more blending systems  300  are combined, using a single blender system  313 , then prioritization may be controlled manually, in the event of simultaneous demands on the blender system. 
     FIG. 4  is a stylized diagram depicting an illustrative embodiment of a multiple blending system  400  according to the present invention. The blending system  400  comprises a first chemical stream  404 , a second chemical stream  410 , a first blender system  413 , blending system A, blending system B, and blending system C. 
   Blending systems A, B, and C are as described in reference to  FIG. 1 , system  100 . Blending system A comprises, at least, a first chemical stream  404 , a second chemical stream  410 , a blender system  413 , a first solution A 14 , drain A 16 , a first tank system A 17 , a second solution A 20 , and a chemical distribution system A 23 . Blending system B comprises, at least, a first chemical stream  404 , a second chemical stream  410 , a blender system  413 , a first solution B 14 , drain B 16 , a first tank system B 17 , a second solution B 20 , and a chemical distribution system B 23 . Blending system C comprises, at least, a first chemical stream  404 , a second chemical stream  410 , a blender system  413 , a first solution C 14 , drain C 16 , a first tank system C 17 , a second solution C 20 , and a chemical distribution system C 23 . 
   Multiple blending system  400  may represent, as an example, a typical sub-fab installation at a typical semiconductor fabrication facility. In such an installation the first chemical stream may be a developer, a surfactant, de-ionized water, etc. Blending system A may represent a particular blended solution, or a particular concentration of a particular blended solution. First tank A 17  may represent a qualification tank or a day tank at such a facility. When the process as described above with reference to  FIG. 1  is undertaken with respect to blending system A, the first tank may contain sufficient fluid to supply the tool at the fab for several hours or more. At such at time, the blender system  413  may be purged with de-ionized water, re-calibrated and is available to blend the solution or concentration required by either blending system B or blending system C. 
   As described above with reverence to  FIG. 1 , blending system A has numerous points at which the formulation of the solution may be monitored and confirmed. Should corrections become necessary, such corrections may be undertaken as described above with reference to  FIG. 1 . The centralized monitoring system may monitor and adjust numerous blending streams simultaneously. If two or more blending systems  100  are combined, using a single blender system  100 , as defined in system  400 , then the performance of the chemical blending system  100  with the highest volume usage has priority over the system with the next highest volume usage. If two or more blending systems  100  are combined, using a single blender system  100 , then the prioritization may be controlled manually, in the event of simultaneous demands on the blender system. 
   It should be noted that the principles of blending system  400  may be applied to any system wherein two or more blending systems  100  are combined using a single blender system  113 . 
     FIG. 5  is a stylized diagram depicting another illustrative embodiment of a multiple blending system  500  according to the present invention. The blending system  500  comprises a first chemical stream  504 , a second chemical stream  510 , a first blender system  513 , blending system A, blending system B, and blending system C. 
   Blending systems A, B, and C are as described in reference to  FIG. 2 , system  200 . Blending system A comprises, at least, a first chemical stream  504 , a second chemical stream  510 , a blender system  513 , a first solution A 14 , drain A 16 , a first tank system A 17 , a second tank system A 23 , a second solution A 20 , a third solution A 26 , and a chemical distribution system A 29 . Blending system B comprises, at least, a first chemical stream  504 , a second chemical stream  510 , a blender system  513 , a first solution B 14 , drain B 16 , a first tank system B 17 , a second tank system B 23 , a second solution B 20 , a third solution B 26 , and a chemical distribution system B 29 . Blending system C comprises, at least, a first chemical stream  504 , a second chemical stream  510 , a blender system  513 , a first solution C 14 , drain C 16 , a first tank system C 17 , a second tank system C 23 , a second solution C 20 , a third solution C 26 , and a chemical distribution system C 29 . 
   Multiple blending system  500 , may represent, as an example, a typical sub-fab installation at a typical semiconductor fabrication facility. In such an installation the first chemical stream may be a developer, a surfactant, de-ionized water, etc. Blending system A may represent a particular blended solution, or a particular concentration of a particular blended solution. First tank A 17  or second tank A 23  may represent a qualification tank or a day tank at such a facility. When the process as described above with reference to  FIG. 2  is undertaken with respect to blending system A, the first tank may contain sufficient fluid to supply the tool at the fab for several hours or more. At such at time, the blender system  513  may be purged with de-ionized water, re-calibrated and is available to blend the solution or concentration required by either blending system B or blending system C. available to blend the solution or concentration required by either blending system B or blending system C. 
   As described above with reverence to  FIG. 2 , blending system A has numerous points at which the formulation of the solution may be monitored and confirmed. Should corrections become necessary, such corrections may be undertaken as described above with reference to  FIG. 2 . The centralized monitoring system may monitor and adjust numerous blending streams simultaneously. If two or more blending systems  200  are combined, using a single blender system  200 , as defined in system  500 , then the performance of the chemical blending system  200  with the highest volume usage has priority over the system with the next highest volume usage. If two or more blending systems  200  are combined, using a single blender system  200 , then the prioritization may be controlled manually, in the event of simultaneous demands on the blender system. 
   It should be noted that the principles of blending system  500  may be applied to any system wherein two or more blending systems  200  are combined using a single blender system  213 . 
     FIG. 6  is a stylized diagram depicting yet another illustrative embodiment of a multiple blending system  600  according to the present invention. The blending system  600  comprises a first chemical stream  604 , a second chemical stream  610 , a first blender system  613 , blending system A, blending system B, and blending system C. 
   Blending systems A, B, and C are as described in reference to  FIG. 3 , system  300 . Blending system A comprises, at least, a first chemical stream  604 , a second chemical stream  610 , a blender system  613 , a first solution A 14 , drain A 16 , a first tank system A 17 , a second tank system A 23 , a third tank system A 29 , a second solution A 20 , a third solution A 26 , a fourth solution A 30  and an end user A 33 . Blending system B comprises, at least, a first chemical stream  604 , a second chemical second solution B 20 , a third solution B 26 , a fourth solution B 30  and an end user B 33 . Blending system C comprises, at least, a first chemical stream  604 , a second chemical stream  610 , a blender system  613 , a first solution C 14 , drain C 16 , a first tank system C 17 , a second tank system C 23 , a third tank system C 29 , a second solution C 20 , a third solution C 26 , a fourth solution C 30  and an end user C 33 . 
   Multiple blending system  600  may represent, as an example, a typical sub-fab installation at a typical semiconductor fabrication facility. In such an installation the first chemical stream may be a developer, a surfactant, de-ionized water, etc. Blending system A may represent a particular blended solution, or a particular concentration of a particular blended solution. First tank A 17 , second tank A 23 , or third tank A 29  may represent a qualification tank or a day tank at such a facility. When the process as described above with reference to  FIG. 3  is undertaken with respect to blending system A, the first tank may contain sufficient fluid to supply the tool at the fab for several hours or more. At such at time, the blender system  613  may be purged with de-ionized water, re-calibrated and is available to blend the solution or concentration required by either blending system B or blending system C. 
   As described above with reverence to  FIG. 3 , blending system A has numerous points at which the formulation of the solution may be monitored and confirmed. Should corrections become necessary, such corrections may be undertaken as described above with reference to  FIG. 3 . The centralized monitoring system may monitor and adjust numerous blending streams simultaneously. If two or more blending systems  300  are combined, using a single blender system  300 , as defined in system  600 , then the performance of the chemical blending system  300  with the highest volume usage has priority over the system with the next highest volume usage. If two or more blending systems  300  are combined, with the highest volume usage has priority over the system with the next highest volume usage. If two or more blending systems  300  are combined, using a single blender system  300 , then the prioritization may be controlled manually, in the event of simultaneous demands on the blender system. 
   It should be noted that the principles of blending system  600  may be applied to any system wherein two or more blending systems  300  are combined using a single blender system  313 . 
   Illustrative embodiments of the invention are described above. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
   These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. 
   The invention is not limited to the preferred embodiments described above, but rather defined by the claims set forth below.