Abstract:
A blending system that accurately produces the desired predetermined fluid composition by continuously monitoring each fluid components mass or volume flow.

Description:
FIELD OF USE  
       [0001]     The invention relates to a method of blending two or more fluid components. In particular the invention relates to a blending method that accurately achieves desired component ratios by continuously monitoring the mass or volume flow rates throughout the blending delivery system and constantly comparing the total delivered amount of each component against the desired recipe for component concentrations.  
       BACKGROUND OF THE INVENTION  
       [0002]     There are many apparatus for blending two or more fluid components. The use of blenders to continuously mix two or more components to achieve a final composition of determined concentrations is known. Current continuous blenders achieve the desired component ratio(s) in the final composition by using control methods that attempt to control the blend ratio in “real-time” throughout the entire delivered volume. As the components are flowing, a controller uses a control-method, which is an algorithm typically implemented by software that continuously and essentially instantaneously varies valves, positive displacement pumps and/or other flow control means, based on mass or volume flow information, to constantly maintain the desired blend ratio at the blender output. A known method is disclosed in U.S. Pat. No. 4,876,053, which teaches a blending system utilizing individual closed loop control under an algorithm for comparing the ratio of actual accumulated volumes of the fluids relative to a statistical determined ratio of ideal volume of each component for a pre-selected blend ratio.  
         [0003]     A problem with known blending methods is that the over-all accuracy of the resulting component composition is only as exact as the instantaneous control accuracy of the hardware. In general, control valves, positive displacement pumps and other flow control means have less control accuracy at the low end of their operating range resulting in poor instantaneous accuracy at low flow rates. Thus, the blend systems using the known control method have low blend accuracy when continuously blending at low flow rates. Additionally, the overall accuracy of the blend is affected at high flow rates when flow start-up of a delivery sequence is considered. Therefore, existing control methods rely upon a large batch size, the blended volume during a particular operating period, delivered over a relatively long period to “average out” the errors encountered at flow start-up.  
         [0004]     There is a need for a blending method that overcomes the instantaneous accuracy limitations of the current blender control methods. The present invention is a novel method that overcomes the instantaneous accuracy limitations of the known blender control methods. This novel method continuously monitors and stores mass or volume flow information from the start of the blending process, that is, the start of a particular operating period, and continuously compares the concentration of the component in the total blended volume against the desire recipe for fluid concentrations, and, should the concentration of one or more of the components drift from the prescribed recipe, this method controls and adjusts the delivery rates to bring the total delivered volume into compliance, even if that causes the instantaneous ratio to fall outside of normal accuracy limits.  
         [0005]     An advantage of the invention over the known methods is that corrections are made for the delivery accuracy errors at very low flow rates. This is important not only when continuously blending at low flow rates, but the method compensates for poor instantaneous accuracy at start-up and quickly brings the total blended volume into compliance with the desired fluid recipe. Unlike the current blender control methods, the present invention does not rely on a large batch size to “average out” errors encountered at start-up. Hence, the invention allows blenders to have greater blend accuracy at relatively low flow rates and allows blenders to deliver smaller batches with tighter accuracy tolerances when compared to blenders using current control methods.  
       SUMMARY OF THE INVENTION  
       [0006]     The object of the present invention is to provide a blending method that overcomes the instantaneous accuracy limitations of current blender control means. Another object of the invention is to provide a blending method which monitors and stores mass or volume flow information from the start of delivery and constantly compares component concentration in the blended volume against the desire recipe of component concentrations.  
         [0007]     To achieve these objects the present invention provides a method to blend two or more fluid components, wherein N is the number of fluid components comprising: 
        (a) continuously measuring, accumulating and storing flow information on at least N-1 fluid components to be blended since the start of a blending process,     (b) calculating the concentration of at least N-1 fluid component in the total blended volume of fluid,     (c) continuously comparing the calculated concentration of the fluid components in the total blended volume against a blend recipe for fluid component concentrations, and     (d) continuously adjusting flow rates for at least one fluid component to achieve the desired concentration of each component in the total blended volume,     whereby continual control of the concentration of the measured fluid component in the total blended fluid volume. The composition of this invention is blended in the following apparatus for blending two or more fluid components comprising:     (a) at least two inlets that supply the individual fluid components into the blender,     (b) piping for transporting the components through at least one mixing location,and transporting the blended fluid to a blender output;     (c) a means for measuring flow through the piping such that the flow of each individual component can be calculated;     (d) a means for controlling flow rates such that the flow of each individual fluid component from the at least two inlets can be independently varied to control the concentration of the individual components in the blended fluid at the output of the blender; and     (e) a blender controller suitable for executing a control method, wherein the controller is adapted to: 
            (i) receive information to start the blending process,     (ii) continuously measure, accumulate and store flow information since the start of a blending process, and calculating the concentration of one of the following, each fluid component, each fluid component except one, in the total blended volume of fluid,     (iii) continuously compare the calculated concentration of the components in the total blended volume against a recipe for component concentrations, and     (iv) continuously adjust flow rates to achieve and maintain the desired concentration of each component in the total blended volume since the start of the blending process, 
 
 resulting in a blending system capable of accurately blending two or more components to a desired blend recipe. 
   
               
 
         [0023]     The composition of this invention is blended using the method of blending two or more blend components comprising: 
        (a) receiving information about a blend recipe into a system control means;     (b) initiating a flow of individual components by the system control means to a prescribed blend ratio from the blend recipe;     (c) continuously measuring flows and calculating concentrations of the individual components in the total blended volume since the initiation of fluid flow;     (d) continuously comparing the metered concentrations to the concentrations of the blend recipe and continuously adjusting flow rates based upon the comparisons to achieve and maintain the blend recipe concentrations; and     (e) terminating the flow of the components based upon at least one of the following: having reached a total blended volume that is at least the desired batch size, receiving an input signal to terminate blending.        
 
         [0029]     The method of the invention can be used in blend systems designed for a variety of applications including but not limited to ethanol blending into gasoline, methanol blending into gasoline, methanol/butyl alcohol blending into gasoline, multi-component alcohol blending into gasoline, butane blending into gasoline, ethyl-hexyl nitrate into diesel fuel, gasoline grade blending (i.e., premium gasoline blended with regular gasoline to make mid-grade gasoline), dimethyl ether blending into diesel fuel, multi-component blending into diesel fuel, multi-component blending into heating oil, oxygenate blending, gasoline into alcohol (for denaturing), RVP blending, emulsified fuels, hydraulic and gear fluids, and various other industrial fluids, and the like. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]      FIG. 1  is a schematic diagram of one embodiment of a blending system capable of blending one fluid component with another fluid component.  
         [0031]      FIG. 2  is a flow chart illustrating an embodiment of the method of the present invention relating to a method for operating the blender of  FIG. 1 .  
         [0032]      FIG. 3  is a schematic diagram of another blending system capable of blending two fluid components.  
         [0033]      FIG. 4  is a flow chart illustrating another embodiment of the method of the present invention for operating the blender of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     With reference to  FIG. 1 , blending apparatus  1  is shown that includes two fluid component inlets  3 ,  5 , piping  7 , blending location  9 , meters  11 ,  13  and valves  15 ,  17  in the piping, blender output  19  and blender controller  21 . As used herein, a fluid component is any material or mixture of materials that can flow, and which flow can be measured by, either volume or mass, and further can be controlled. Fluid components include, but are not limited to liquids, gasses solid particulates and mixtures thereof, in particular chemicals, fuels, fluid, additives, lubricant oil and the like. Exemplary components include but are not limited to ethanol, methanol, methanol/butyl alcohol, multi-component alcohol, butane, ethyl-hexyl nitrate, gasoline, dimethyl ether heating oil, oxygenate blending, gasoline into alcohol (for denaturing), gasoline, diesel fuel, emulsified fuel and mixtures thereof. The blender inputs  3 ,  5  connect to storage tanks, pipe lines or other fluid providing means (not shown) that supply the blender location  9  with the individual fluid components to be blended. Inputs  3 ,  5  may each include a pump, a manual isolation valve, a check valve, filters, connector and/or other devices that are known in the art. The piping  7  transports the individual fluid components from the individual inlets  3 ,  5  to blending location  9  and the blended fluid components from the blending location  9  to the blender output  19 . Blender output  19 , which may include pump, manual isolation valve, check valve, filters, connector and/or other devices that are known in the art, is where blended fluid exits blender apparatus  1  and is typically connected to an appropriate device such as a storage tank, a delivery tank, a pipe line or other receptacle while the blender is in use. Blending location  9  is where the two individual fluid components from inlets  3 ,  5  are mixed. The mixing may occur by merging the two fluid streams. Meter  11  and valve  15  are located in piping  7  between inlet  3  and blending location  9 . Meter  11  measures the amount, which can be either a volume or mass, of fluid component supplied from inlet  3  that flows through piping  7  and provides an output of the amount measured to blender controller  21  through communication conduit  23 . Whether mass or volume flow of the fluid component is measured depends upon the type of meter used. Valve  15  controls the flow of fluid component from inlet  3  through piping  7  to blending location  9  as determined by an output signal from blender controller  21  through communication conduit  25 . That is, signals can be sent to valve  15  to increase, decrease or stop the flow of fluid from inlet  3 . Similarly, meter  13  and valve  17  are located in piping  7  between inlet  5  and blending location  9 . Meter  13  measures the amount, which can be either a volume or mass, of fluid component supplied from inlet  5  that flows through piping  7  and provides an output of the amount measured to blender controller  21  through communication conduit  27 . Valve  17  controls the flow of fluid component from inlet  5  through piping  7  to blending location  9  as determined by an output signal from blender controller  21  through communication conduit  29 . Blender controller  21  receives signals from meters  11 ,  13  and provides output to valves  15 ,  17  based and inputs and/or outputs information with external devices(not shown) such as a computer, key pad, switch, monitor, sensor, mechanical preset, electronic preset, programmable logic controller (PLC), terminal automation system (TAS) or other, through information conduit  31 .  
         [0035]     With continued reference to  FIG. 1 , in blender controller  21  of blender apparatus  1  receives information through conduit  31 , which can include blend recipe, batch size, start and finish of blend process and other information. Based on that information and a above described method, which is typically implemented by software stored in blender controller  21 , the blender controller  21  monitors meters  11 ,  13  and control valves  15 ,  17  to achieve the desired concentration of the two fluid components supplied from inputs  3 ,  5  in the blended fluid delivered from blender apparatus  1  at blender output  19 . Blender controller  21  reports information about the blend process and the blended fluid during and/or after the blending process through conduit  31  to provide information outputs for process operators and/or to document the blending-process/blended-fluid.  
         [0036]      FIG. 2  show a flow chart of blend method  35 , which is one embodiment of the present invention that can be used with blender apparatus  1  of  FIG. 1  to provide improved blend accuracy for blended fluid of any batch size. Blend method  35  begins in block  37  when a blend recipe, which specifies the concentration of the two fluid components in the blended fluid output of the blender, and a batch size, which specifies the total amount of fluid to be produced by the blender during the blending process, is downloaded to the blender controller  21  through a communication conduit  31  from one or more input devices such as a key pad, programmable logic controller (PLC), terminal automation system (TAS), or other input devices known in the art. For example, in blender apparatus  1  of  FIG. 1  the information is downloaded to blender controller  21  from device(s) (not shown) through communication conduit  31  to blender controller  21 . After receiving the blend recipe, method  35  proceeds to block  39  where either from receiving a separate signal or automatically after the information is received the method commands the blender controller  21  to turn the blender “on” by sending signals to the blender valves. For example blender controller  21  sends signals to valves  15  and  17  to allow the appropriate flow of the fluid components to be blended. Method  35  determines in block  41  if the controller has received a signal to stop blending. The blender controller  21  may receive a stop signal from an input device such as a switch, sensor, key pad, programmable logic controller (PLC), terminal automation system (TAS), or other input devices known in the art. Various reasons to stop blending include an equipment failure, a stop in the supply of one of the fluid components, blender output exceeding the capacity of the receptacle receiving the blended fluid, detection an unsafe blending condition and completion of the blend recipe. If the determination in block  41  is “yes”, then in block  43  method  35  commands the blender controller  21  to turn the blender “off” by sending signals that stop the flow of all fluid components such that there is no output from the blender. For example, blender controller  21  of  FIG. 1  send signals to valves  15 ,  17  to close. Further, in block  45  method  35  commands the blender controller  21  to send a report that can indicate that the blend process has stopped and/or that documents the batch of fluid blended. For example blender controller  21  of  FIG. 1  could send an audible or visual signal using communication conduit  31 , that is heard or seen by an operator or a report could be sent, that details the amount of fluid blended, concentrations of the fluid components, and/or other information to a monitor, a printer, a TAS, and/or other information display, storage or analysis device. If the determination in block  41  is “no”, method  35  in block  47  commands the blender controller  21  to accumulate and store the amount of each fluid component delivered through the blender since the blender was turned “on”. The, blender controller  21  of  FIG. 1  using communication conduits  23  and  27  monitors the outputs of meters  11  and  13  respectively to accumulate and store the total amounts of fluid components delivered through inputs  3  and  5  respectively since the blending process for a particular batch began. For example, the fluid component delivered by input  3  is defined herein as the base fluid, and the fluid component delivered by input  5  is defined herein as the “additive”. Hence, in block  47  method  35  accumulates and stores the total amount of base fluid and additive delivered since the blender was turned “on” in block  39 . In block  49 , method  35  calculates the total blended volume since the blender was turned “on” and the concentration of additive in the total blended volume using the accumulated amounts of base fluid and additive stored in block  47 , and in block  51  the method  35  determines if the calculated total blended volume is greater than or equal to the batch size downloaded in block  37 . If the determination is “yes” then in block  43  method  35  commands the blender controller  21  to turn the blender “off”, and in block  45  to send a blend report. If the determination of block  51  is “no”, in block  53  method  35  determines if the additive concentration is greater than that required by the recipe downloaded in block  37 . If the determination is “yes”, in block  55  method  35  commands the blender controller  21  to send a signal to decrease the flow of additive in the blender, for example controller  21  of  FIG. 2  sends a signal to valve  17  to reduce the additive flow through inlet  5 . If the determination of block  53  is “no”, in block  57  method  35  determines if the additive concentration is less that that required by the recipe, and if the determination is “yes”, in block  59  the method  35  commands the controller send a signal to increase the additive flow in the blender. If the determination of block  57  is “no”, then method  35  does not command a change in the additive flow. If the additive flow rate is decreased in block  55 , increased in block  59  or remains the same due to a “no” determination in block  57 , the method  35  returns to block  41  and the steps of determining if a “stop” signal was received, accumulating and storing total base fluid and additive since the blender was turned “on”, calculating total blended volume and additive concentration in the total blended volume, comparing total volume and concentration to the downloaded information and, if necessary, adjusting the flow of additive continues until method in block  41  receives a signal to stop blending or until the total volume blended equals or exceed the desired batch size in block  51 . In this manner method  35  assures that the concentration of additive in the total amount blended, independent of batch size, is the amount specified in the recipe downloaded in block  37  even though at any instant the concentration of additive in blender output  19  may be greater or less than the desired recipe concentration since instantaneous concentration information is not used in calculation in block  49  or the determinations of blocks  53  and  57 . Further, method  35  is not limited by a blender&#39;s ability to be instantaneously controlled since the method is continuously controlling the additive flow rate base on total component deliveries since the blender is turned “on” in block  39 .  
         [0037]     Method  35  of  FIG. 2  controls the concentration of the additive by varying the additive flow rate, another embodiments of the invention may in block  55 ,  59  increase or decrease respectively the flow of the base fluid to achieve the desired change in additive concentration, or may vary the flow of both the base fluid and the additive to achieve the desired concentration of the additive in the output of a batch of fluid from a blender of the type shown in  FIG. 1 .  
         [0038]     Method  35  of  FIG. 2  calculates and compares the concentration of the additive to the downloaded blend recipe, it is understood that this is calculating and comparing the base fluid concentration.  
         [0039]      FIG. 1  shows blender apparatus  1  with meters and valves that measure and control flow respectively for the individual fluid components in the piping  7  before blend location  9 . The method of this invention is not limited to having all meters and flow control means located before the blending location  9 . The meters and valves need only be located such that from one or more meter outputs the concentration or each individual fluid component can be measured and controlled to achieve a desired blend recipe in the fluid output of the blender.  
         [0040]      FIG. 3  is blender apparatus  61  where components that are the same as the blender apparatus  1  of  FIG. 1  are numbered the same. Blender apparatus  61  includes two fluid component inlets  3 ,  5 , piping  7 , blending location  9 , meters  13 ,  63  and valves  17 ,  65  in the piping, blender output  19  and blender controller  21 . Meter  63  and valve  65  are in piping  7  between blend location  9  and output  19  such that the meter measures and the valve controls the flow of the blended amount, which can be either a volume or mass, of the two fluid components supplied to inlets  3 ,  5  that flow through piping  7  to outlet  19 . Information of the amount of fluid measured by meter  63  is communicated to blender controller  21  through conduit  67 . Blender controller  21  controls valve  65  by outputs to the valve communicated through conduit  69 . Meter  13  and valve  17  measures and controls respectively the flow of the fluid component, for example the additive, delivered through inlet  5 .  
         [0041]     Blender apparatus  61  of  FIG. 3  operates similar to blender apparatus  1  of  FIG. 1  except the blend method calculates the concentration of the additive using accumulated and stored total amounts as in the present invention, from measured amounts of blended fluid, with meter  63 , and one of the components, with meter  13 , instead of from measured amounts of the two components individually. Also the blend method for blender apparatus  61  controls the concentration of the additive by controlling the total flow with valve  63  and/or by controlling the flow of the additive from input  5  with valve  11 .  
         [0042]      FIG. 4  is a flow chart of blend method  73 , which is one embodiment of the present invention that can be used with blender apparatus  61  of  FIG. 2 . Blocks of method  73  that are the same as blocks in blend method  35  of  FIG. 2  are identically labeled. Blend method  73  begins in block  75  where the blend recipe is downloaded to a blender controller  21 . After receiving the blend recipe, as in method  35  of  FIG. 2 , method  73 , either from receiving a separated signal or automatically, commands the blender turned “on” in block  39  and determines if a “stop” signal is received in block  41 . If the determination is that a “stop” signal is received, in block  43 , method  73  commands the blender controller  21  to turn the blender “off”. In this embodiment, method  73  does not send a blend report when the blender is turned “off”. If the determination in block  41  is “no”, method  73  in block  77  commands the blender controller  21  to accumulate and store the total blended volume delivered by the blender and the amount of the additive delivered to the blender since it was turned “on”. For example, blender controller  21  of  FIG. 3  would use communication conduits  67 ,  27  to monitor the outputs of meters  63 , and  13  and would accumulate and store the total amount of blended fluid delivered from outlet  19  and the total amount of additive delivered through inlet  5  since the blending process began. Using the accumulated and stored total blended volume and the additive volume of block  77 , in block  79  method  73  calculates the concentration of the additive in the total amount of fluid that has been blended since the blender was turned “on” in block  39 . In blocks  53  and  57 , method  73  determines if the concentration is greater than or less than the recipe concentration, downloaded in block  75 . If the concentration of the additive is too great, method  73  appropriately decreases the additive flow in block  55 . If the concentration of the additive is too small method  73  increases the additive flow in block  59  or makes no change in the flow of the additive before returning to block  41 . Method  73  continuously repeats the steps of determining if a “stop” signal was received, accumulating and storing total blended volume and additive volume since blender was turned “on”, calculating additive concentration in the total blended volume, comparing the additive concentration to the downloaded recipe and, if necessary, and adjusting the flow of the additive until the method in block  41  receives a signal to stop the blending process. In this manner method  73  assures that the concentration of the additive in the total blended volume is the amount specified in the recipe downloaded in block  75  even though at any instant the concentration of the additive in blender output  19  may be greater or less than the desired recipe concentration.  
         [0043]     Method  73  of  FIG. 4  controls the concentration of the additive by varying the additive flow rate, other embodiments of the invention in blocks  55 ,  59  can increase or decrease respectively the total flow rate. For example by blender controller  21  of  FIG. 3  sending signals to valve  65  through conduit  69 , to achieve the desired change in additive concentration, or may vary both the additive flow and total flow to achieve the desired concentration of the additive in the blender output  19  of a batch of fluid from a blender apparatus  61  shown in  FIG. 3 .  
         [0044]     Although method  73  of  FIG. 4  calculates and compares the concentration of the additive to the downloaded recipe, it is understood that this is essentially the same as calculating and comparing the base fluid concentration since what is not additive in the blended fluid is base fluid.  
         [0045]      FIGS. 1 and 3  show blenders that blend only two fluid components delivered through inlets  3 ,  5 ; however, the method of this invention is not limited to controlling blenders for only two fluid components.  
         [0046]     The method of the present invention can be used in blend systems designed for a variety of applications including ethanol blending into gasoline, methanol blending into gasoline, methanol/butyl alcohol blending into gasoline, multi-component alcohol blending into gasoline, butane blending into gasoline, ethylhexyl nitrate into diesel fuel, gasoline grade blending (i.e., premium gasoline blended with regular gasoline to make mid-grade gasoline), dimethyl ether blending into diesel fuel, multi-component blending into diesel fuel, multi-component blending into heating oil, oxygenate blending, gasoline into alcohol (for denaturing), RVP blending, etc. Additization can be provided for all of the above blending applications, with provisions for single or multiple additive injection.  
         [0047]     While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications maybe made therein without departing from the invention in its broadest aspects. Various combinations of these embodiments can be made, and the tailoring of the invention to fit the needs of the individual blending system is a feature of the invention.