Abstract:
A natural gas odorant injection system for injecting odorant into a main gas line includes a by-pass line, an odorant tank, a flowmeter, a control valve, and a controller communicably coupled to the flowmeter and the control valve. The by-pass line includes an inlet that is in fluid communication with an upstream section of the main gas line, and an outlet that is in fluid communication with a downstream section of the main gas line. The odorant tank, the control valve, and the flowmeter are disposed in the by-pass line. The flowmeter senses a characteristic of a fluid flow through the flowmeter and, accordingly, generates a fluid flow signal. The controller is programmed to operate the control valve based on the fluid flow signal received from the flowmeter.

Description:
RELATED APPLICATION DATA  
       [0001]     The present application is a non-provisional application based on, and claiming the priority benefit of, co-pending U.S. provisional application Ser. No. 60/537,572, which was filed on Jan. 20, 2004, and is expressly incorporated by reference herein. 
     
    
     FIELD OF THE DISCLOSURE  
       [0002]     The present disclosure generally relates to gas odorant injection systems and, more specifically, to natural gas odorant injection systems using flowmeter controls.  
       BACKGROUND OF THE DISCLOSURE  
       [0003]     Traditional natural gas odorant injection systems have used small by-pass systems for low natural gas flow demand applications, and pump based systems for high flow rate applications. The advantage of by-pass systems is that they are inexpensive. Their disadvantage is they have limited rangeability, resulting in under odorization if natural gas flow rates increase significantly or over odorization if they decrease significantly. By-pass systems also require a pressure drop in the pipeline, such as a control valve, regulator, or other pressure reduction station to operate, as well as pressurization of the odorant storage tank. Pump based systems have somewhat higher rangeability and do not require a pressure differential or pressurized storage tanks for operation, but are much more expensive and tend to have reliability issues. As a result, a by-pass system is used in low flow and lower pressure applications where installation cost is an issue. Pumps are used in high flow and high-pressure applications where control of odorant injection rates are critical and the costs for large high-pressure storage tanks offset the higher costs of the pump system.  
         [0004]     Natural gas odorant injection systems having a pressure injection mechanism have been recently introduced that provide an alternative for intermediate and low flow/pressure applications. Like the by-pass systems, they require a pressure differential and a pressurized storage tank to operate. This is a disadvantage over pump based systems for very high-pressure transmission applications. Pressure injection systems utilize solenoid valves to control injection rates. Both the duration of valve opening and the dwell time between openings can be controlled. This results in unmatched rangeability, a key advantage over both pump and by-pass systems. Solenoid valves are also inherently more reliable than pumps. By-pass systems, however, still have a niche for very small flow applications due their low cost.  
         [0005]     A key issue with pressure injection systems is that they utilize a calibrated cylinder to monitor injection rates and recalibrate solenoid timing. This results in a somewhat large and complex system. It also requires release of a small amount of highly odorant-saturated natural gas to atmosphere every time the calibration/injection cylinder is refilled. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a schematic diagram of a natural gas odorant injection system constructed in accordance with one example of the teachings of the present disclosure;  
         [0007]      FIG. 2  is a schematic diagram of another example of a natural gas odorant injection system;  
         [0008]      FIG. 3  is a schematic diagram of one example of a tank used in the natural gas odorant injection system of  FIG. 2 ;  
         [0009]      FIG. 4  is a schematic diagram of another example of a tank used in the natural gas odorant injection system of  FIG. 2 ;  
         [0010]      FIG. 5  is a schematic diagram of one example of a controller as used in the natural gas odorant injection system of  FIG. 2 ;  
         [0011]      FIG. 6  is a schematic diagram of another example of a natural gas odorant injection system;  
         [0012]      FIG. 7  is a schematic diagram of yet another example of a natural gas odorant injection system; and  
         [0013]      FIG. 8  is a flowchart of one example of an operation of the natural gas odorant injection system of  FIG. 2 . 
     
    
       [0014]     While the method and device described herein are susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure and the appended claims.  
       DETAILED DESCRIPTION  
       [0015]     A natural gas odorant injection system, as described below, is generally utilized to add odor to otherwise odorless natural gas. Basically, the odorizing of the natural gas may be accomplished by by-passing the odorless natural gas from a main gas line, and then odorizing the gas via a liquid odorant and/or using the odorless natural gas to pressurize an odorant, thereby injecting the odorized gas and/or odorant back into the main gas line.  
         [0016]     Referring now to the drawings and with specific reference to  FIG. 1 , a natural gas odorant injection system as constructed in accordance with the teachings of the disclosure is generally depicted by reference numeral  20 . As shown therein, the natural gas odorant injection system  20  in one exemplary embodiment includes a by-pass line  22  including a tank  24 , a control valve  26 , a first flowmeter  28 , and a controller  30 .  
         [0017]     As seen in  FIG. 1 , the by-pass line  22  may be fluidly connected to a main gas line  32  at an inlet  34  of the by-pass line  22 , and may reenter the main gas line  32  at an outlet  36  of the by-pass line  22 . The main gas line  32 , at the inlet  34 , contains odorless natural gas having a pressure that may be in the range of 60 psi to 1500 psi. For reasons of brevity and clarity, however, the natural gas odorant injection system  20  will herein be described as operating in an environment wherein the non-odorized main gas line pressure at the inlet  34  is approximately 500 psi.  
         [0018]     To ensure that the odorized gas and/or the odorant can be injected into the main gas line  32  at the outlet  36  of the by-pass line  22 , the pressure of the by-pass line  22  at the outlet  36  must be more than the pressure in the main gas line  32  at the outlet  36 . This differential pressure between the main gas line  32  and the by-pass line  22  may be accomplished in several ways. For example, as seen in  FIG. 1 , the pressure of the main gas line  32  may be reduced between the inlet  34  of the by-pass line  22  and the outlet  36  of the by-pass line  22  by a regulator  38 . The regulator  38  may include, but is not limited to, a differential pressure regulator and a constant pressure regulator, and may be any type of regulator able to reduce a first pressure to a second pressure. In this exemplary embodiment, the regulator  38  may be a constant pressure regulator set at approximately 300 psi, such that the pressure of the main gas line  32 , after the regulator  38 , is approximately 300 psi. As such, the pressure of the by-pass line  22  at the outlet  36  may be approximately 500 psi and the pressure in the main gas line  32  at the outlet  36  would be approximately 300 psi, thereby ensuring that a proper differential pressure is created and that the odorized gas and/or the odorant can be injected from the outlet  36  into the main gas line  32 .  
         [0019]     Alternatively, in another exemplary embodiment, as seen in  FIG. 2 , the by-pass line may undergo a pressure change as well as the main gas line  32 , and more specifically, may undergo a pressure reduction. For example, as seen in  FIG. 2 , a regulator  40  may be disposed in the by-pass line  22  between the inlet  34  and the outlet  36 . The regulator  40  may be substantially similar to the regulator  38 , or may be any other type of regulator able to reduce a first pressure to a second pressure. In this exemplary embodiment, the regulator  40  may be a constant pressure regulator set at approximately 400 psi, such that the pressure of the by-pass line  22 , after the regulator  40 , is approximately 400 psi. As such, the pressure of the by-pass line  22  at the outlet  36  may be approximately 400 psi and the pressure in the main gas line  32  at the outlet  36  would be approximately 300 psi, thereby ensuring that a proper differential pressure is created and that the odorized gas and/or the odorant can be injected from the outlet  36  into the main gas line  32 .  
         [0020]     The tank  24 , as seen in  FIGS. 1, 2 ,  3 , and  4 , contains the odorant which may, as in this exemplary embodiment, be stored in liquid form to odorize the natural gas. More specifically, as seen in  FIG. 3 , the odorless gas may enter the tank  24  at an inlet  42  and become saturated with odorant by bubbling through the odorant, or otherwise becoming saturated, and then exit the tank  24  at an outlet  44  as odorized gas. Alternatively, as seen in  FIG. 4 , the odorless gas may enter the tank  24  at an inlet  42  thereby causing a pressure in the tank  24 . The pressure of the odorless gas in the tank  24  may cause the odorant to exit the tank  24 , without gas, at an outlet  44 . The state of the odorant leaving the tank  24  at the outlet  44  may, however, be a combination of the above embodiments. For example, the odorant leaving the tank  24  may be entirely gaseous, entirely liquid, or a mixture thereof. As such, the odorant leaving the tank  24  at the outlet  44  may be part gas and part liquid.  
         [0021]     Returning to  FIG. 2 , the odorant, prior to reentering the main gas line  32 , may travel though the control valve  26  and the flowmeter  28 . The control valve  26 , may be any type of valve able to regulate the flow of fluid, whether in liquid and/or in gaseous form. For example, the control valve  26  may be a solenoid valve able to open and close for specific periods of time, or may be able to open and close incrementally. Furthermore, as in this exemplary embodiment, the control valve  26  may be communicably coupled to the controller  30 , and more specifically, may be communicably coupled via a hard wire and/or wireless technology.  
         [0022]     The flowmeter  28  may be any type of flowmeter able to meter the flowrate of the fluid, whether in liquid and/or gaseous form. For example, the flowmeter  28  may be one of many types of flowmeters, including but not limited to, a coriolis, a vortex, a turbine, a variable area, an electromagnetic, and an ultrasonic type flowmeter. Depending on the type of flowmeter that is used, one or more variables of the fluid may be measured. In this exemplary embodiment, the coriolis type flowmeter  28  measures the mass of the liquid odorant as it passes through the flowmeter  28 . More specifically, the flowmeter  28  measures the flow of the odorant by analyzing changes in a Coriolis force of the odorant. The Coriolis force is generated in a mass which is moving within a rotating frame of reference. That rotation produces an angular, outward acceleration, which is factored with linear velocity to define the Coriolis force. With the mass of the odorant, the Coriolis force is proportional to the mass flowrate of that fluid. Furthermore, the flowmeter  28  may be communicably coupled to the controller  30 , and more specifically, may be communicably coupled via a hard wire and/or wireless technology.  
         [0023]     A second flowmeter  46 , as seen in  FIG. 2 , may be located between the inlet  34  of the by-pass line  22  and/or the first regulator  38 , and the outlet  36  of the by-pass line  22 . The second flowmeter  46 , like the flowmeter  28 , may be one of many types of flowmeters, including but not limited to, a coriolis, a vortex, a turbine, a variable area, an electromagnetic, and an ultrasonic type flowmeter. Depending on the type of flowmeter that is used, one or more variables of the fluid may be measured. In this exemplary embodiment, the flowmeter  46  measures the volumetric flowrate of the unodorized natural gas flowing through the flowmeter  46 .  
         [0024]     The controller  30 , as seen in  FIG. 5 , may comprise a program memory  52 , a microcontroller or microprocessor (MP)  54 , a random-access memory (RAM)  56 , and an input/output (I/O) circuit  58 , all of which may be interconnected via an address/data bus  60 . It should be appreciated that although only one microprocessor  54  is shown, the controller  30  may include additional microprocessors. Similarly, the memory of the controller  30  may include multiple RAMs  56  and multiple program memories  52 . Although the I/O circuit  58  is shown as a single block, it should be appreciated that the I/O circuit  58  may include a number of different types of I/O circuits.  
         [0025]     Additionally and/or alternatively, the controller  30  may be a programmable Logic Controller (“PLC”) or any other type of mechanical and/or electrical device able to activate, deactivate and/or control the control valve  26 , the first flowmeter  28 , and/or the second flowmeter  46 .  
         [0026]     The above exemplary embodiments may include many variations thereof to achieve and/or create additional or alternative features. For example, the location of the various components in the natural gas odorant injection system  20  may be changed and/or altered. For example, the regulator  40  may be positioned before or after the tank  24 , and similarly, the flowmeter  28  and/or the control valve  26  may be positioned before or after the tank  24 , as seen in  FIG. 7 . The control valve  26  also need not be located after the flowmeter  28  in the line of flow of the fluid, but may be located anywhere before the flowmeter  28 , as seen in  FIG. 6 . The natural gas odorant injection system  20  may also include additional components such as one or more check valves  62  ( FIG. 7 ) located along the by-pass line  22 . As seen in  FIG. 7 , a check valve  62  may be located between the control valve  26  and the outlet  36  of the by-pass line  22 , thereby preventing the unodorized gas from the main gas line  32  from entering the by-pass line  22  through the outlet  36  of the by-pass line  22 .  
         [0027]     A method for operating the natural gas odorant injection system  20  is illustrated by the flowchart in  FIG. 8 . An operation  100  of such an exemplary embodiment may begin at block  102  by providing a main gas line  32  that holds unodorized natural gas having a first pressure. At block  104 , the unodorized natural gas from the main gas line  32  may be by-passed at an inlet  34  into a by-pass line  22  and control may be passed to block  106 . At block  106 , the pressure of the by-pass line may be reduced to a second pressure by a regulator  40  or the like. At block  108 , the natural gas may enter a tank  24  of odorant, thereby pressurizing the tank  24  and forcing the odorant from the tank  24  toward an outlet  36  of the by-pass line  22 . Alternatively and/or additionally, at block  110  the natural gas may enter the tank  24  and become saturated with odorant, which is then forced from the tank  24  toward the outlet  36  of the by-pass line  22 . At block  112 , a flowrate of the odorant from block  108  and/or the flowrate of the saturated gas from block  110  may be obtained, and control may be passed to block  114 . At block  114 , the flowrate obtained at bock  112  may be sent to a controller  30 , and control may pass to block  122 .  
         [0028]     At block  116 , the unodorized natural gas in the main gas line  32  may be reduced to a third pressure that is less than the second pressure by a regulator  38 , or the like. At block  118 , a flowrate of the unodorized gas from block  102  and/or block  116  may be obtained, and control may be passed to block  120 . At block  120 , the flowrate obtained at block  118  may be sent to the controller  30 , and control may pass to block  122 .  
         [0029]     At block  122 , the controller  30  may compare the information obtained at block  122  and block  120 , and more specifically, may compare the flowrate of the natural gas obtained at block  118  to the flowrate of the odorant and/or the flowrate of the saturated gas obtained at block  112 . In this exemplary embodiment, the flowrate obtained at block  118  may be 1,000,000 scfh and the flowrate obtained at block  112  may be 1 lb/hr. Control may then pass to block  123 , where the flowrates are analyzed by the controller  30  to determine whether the natural gas in the main line  32  is being odorized properly by the odorant in the by-pass line  22 . For example, if the controller  30  is programmed to obtain an odorized gas having 1 pound part per million (ppm) of liquid odorant per 1,000,000 standard cubic feet of natural gas, the controller may determine at decision diamond  124  that the ratios or flowrates obtained at block  118  and block  112  properly odorize the natural gas in the main line  32 , and no action will be taken by the controller  30 . Control may then pass to block  122 .  
         [0030]     If, however, the flowrate obtained at block  118  is 2,000,000 scfh, and the flowrate obtained at block  112  is 1 lb/hr, the controller  30  may determine at decision diamond  124  that the ratio or flowrate obtained at block  118  is too great compared to the flowrate at block  112 . As such, the controller  30 , at decision diamond  124  may pass control to block  126 , thereby causing the control valve  26  to open or open more to achieve the 1 pound part per million (ppm) of liquid odorant per 1,000,000 standard cubic feet of natural gas. Control may then pass to block  122 .  
         [0031]     Similarly, if the flowrate obtained at block  118  is 500,000 scfh, and the flowrate obtained at block  112  is 1 lb/hr, the controller  30  may determine at decision diamond  124  that the ratio or flowrate obtained at block  118  is too low compared to the flowrate at block  112 . As such, the controller  30 , at decision diamond  124  may pass control to block  126 , thereby causing the control valve  26  to close or close more to achieve the 1 pound of liquid odorant per 1,000,000 standard cubic feet of natural gas. Control may then pass to block  122 .  
         [0032]     While the present disclosure describes specific embodiments, which are intended to be illustrative only and not to be limiting of the disclosure, it will be apparent to those of ordinary skill in the art that changes, additions or deletions may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure.