Patent Publication Number: US-2019168271-A1

Title: Reduced emissions method of cleaning hydrocarbon separator and storage tanks

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 62/593,748 filed Dec. 1, 2017 and hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This disclosure relates generally to the field of maintenance of storage tanks of production liquids, and more specifically to the field of cleaning storage tanks. 
     A storage tank is an atmospheric tank used for storing and separating output from a well into separate components. For example, some wells produce liquids such as water and oil, gases such as natural gas, solids such as sand and iron sulfide, or some combination thereof. A storage tank allows the different products to settle and separate within the tank and stores production liquids until transport. The separated components are then removed by different outlets. After a period of use, the storage tank may be overfull of solids and need to be cleaned to remove the solids from within the storage tank. Disclosed herein is a method of cleaning a storage tank which may reduce emissions and cleaning down time. 
     SUMMARY 
     Described herein is a method of cleaning a storage tank including isolating the tank; creating a vortex within the tank by pumping fluid through one or more nozzles disposed within the tank, which dislodges sediment within the tank; and connecting a suction source to a drain located on the bottom of the tank, which removes the fluid and sediment from the tank without exposure to air. In some embodiments, isolating the tank includes closing all lines into and out of the tank under a predetermined height except for the one or more nozzles. The predetermined height is chosen based on at least the anticipated height of sediment build-up within the tank and the anticipated volume of fluid required to dislodge the sediment. In some embodiments each nozzle includes one or more sub-nozzles to direct the flow of fluid within the tank to assist in creation of a vortex and removal of the fluid and sediment through the drain. 
     A storage tank and a nozzle assembly for use in connection with the disclosed method of cleaning a storage tank are also described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a storage tank according to one or more embodiments. 
         FIG. 2  shows a close-up view of a nozzle in a storage tank according to one or more embodiments. 
         FIG. 3  shows an overhead view of an example arrangement of the nozzles and drain within a storage tank according to one or more embodiments. 
         FIG. 4  shows, in flow chart form, an example process for cleaning a storage tank according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is directed to a storage tank and a method of cleaning storage tanks. According to one or more embodiments, the disclosed method of cleaning storage tanks may be safer and more environmentally friendly, as well as quicker and more efficient, than traditional methods of cleaning storage tanks. The described example storage tanks include one or more nozzles disposed within the tank, through which fluid may be pumped at a sufficient volume and pressure to create a vortex and dislodge sediment within the tank and flush it through a drain located on the bottom of the tank. The number of nozzles within the tank is chosen based on the size of the tank and the sediment to be cleaned from the tank. In some examples, each nozzle includes two or more sub-nozzles, which direct the fluid within the tank to ease creation of the vortex and to flush the sediment and fluid towards the drain. This may reduce the likelihood of clogs in the drain. In some embodiments, a suction source is applied to the drain to facilitate removal of the fluid and sediment within the tank and direct it to an appropriate waste removal system without exposure to air. 
     In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed concepts. As part of this description, some of this disclosure&#39;s drawings represent structures and devices in block diagram form in order to avoid obscuring the novel aspects of the disclosed embodiments. In this context, it should be understood that references to numbered drawing elements without associated identifiers (e.g.,  100 ) refer to all instances of the drawing element with identifiers (e.g.,  100   a  and  100   b ). Further, as part of this description, some of this disclosure&#39;s drawings may be provided in the form of a flow diagram. The boxes in any particular flow diagram may be presented in a particular order. However, it should be understood that the particular flow of any flow diagram is used only to exemplify one embodiment. In other embodiments, any of the various components depicted in the flow diagram may be deleted, or the components may be performed in a different order, or even concurrently. In addition, other embodiments may include additional steps not depicted as part of the flow diagram. The language used in this disclosure has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the disclosed subject matter. Reference in this disclosure to “one embodiment” or to “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment, and multiple references to “one embodiment” or to “an embodiment” should not be understood as necessarily all referring to the same embodiment or to different embodiments. 
     It should be appreciated that in the development of any actual implementation (as in any development project), numerous decisions must be made to achieve the developers&#39; specific goals (e.g., compliance with system and business-related constraints), and that these goals will vary from one implementation to another. It will also be appreciated that such development efforts 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. 
     Referring to  FIG. 1 , an example storage tank  100  is shown, according to one or more embodiments. Storage tank  100  includes nozzles  110 A-N and a drain  120 . Fluid may be pumped through nozzles  110 A-N to create a vortex within storage tank  100  and dislodge sediment within the tank. The dislodged sediment and fluid pumped through nozzles  110 A-N may then be drained through drain  120 , passively according to the weight of the sediment and fluid or actively according to an external suction force applied to drain  120 . Fluid pressure, volume, flow rate, and the like may be chosen based on the size of storage tank  100  and the type of sediment within it. For example, a larger tank requires higher fluid volume and pressure than a smaller tank under the same conditions. Similarly, heavier sediment with larger particles requires higher fluid volume and pressure than lighter sediment with smaller particles. 
     The number of nozzles  110 A-N may be determined based on the size of storage tank  100 . Generally, there should be a sufficient number of nozzles  110 A-N to dislodge sediment from the entire bottom of storage tank  100 . In some embodiments, where the bottom of storage tank  100  is particularly large, a single nozzle  110  may be insufficient because the available fluid pressure decreases over distance until it is insufficient to dislodge the sediment at a point within the tank farthest from the single nozzle. In those embodiments, two or more nozzles  110 A-N are implemented according to the size of storage tank  100  and the fluid pressure required to dislodge the sediment. Similarly, the placement of the one or more nozzles  110 A-N within storage tank  100  is determined based on the size of storage tank  100 . In some embodiments where two or more nozzles  110 A-N are implemented, the nozzles  110 A-N may be spaced throughout storage tank  100  such that all areas of storage tank  100  experience fluid pressure sufficient to dislodge sediment. For example, where three nozzles  110 A-C are implemented in storage tank  100 , the nozzles  110 A-C may be spaced evenly around the cylindrical sides of storage tank  100 , approximately 120 degrees apart. In some embodiments, the one or more nozzles  110 A-N are positioned within the tank such that the fluid pressure dislodges the sediment at or near the bottom of storage tank  100 . For example, if the one or more nozzles  110 A-N are positioned on the side walls of storage tank  100  at a short height off the bottom of storage tank  100 , the fluid pressure from the one or more nozzles  110  may be used to dislodge the sediment at the base of storage tank  100  and by extension, substantially all sediment in storage tank  100 , rather than merely the top layers of sediment. The position of the one or more nozzles  110 A-N at a short height off the bottom of storage tank  100  may also facilitate draining of the fluid and sediment through drain  120  by decreasing the likelihood of clogs in drain  120 . 
     In some embodiments each of the one or more nozzles  110 A-N may include one or more sub-nozzles for more efficient dislodgment of sediment within storage tank  100 . The number and positioning of sub-nozzles may be chosen to optimize dislodgment of sediment and ease of draining storage tank  100 . For example, each nozzle  110  may include two bi-directional sub-nozzles positioned such that one sub-nozzle aids in dislodging sediment from the bottom of storage tank  100  and the second sub-nozzle aids in flushing the fluid and sediment through drain  120 . 
     Storage tank  100  also includes drain  120  located at the bottom of storage tank  100 . Fluid pumped through nozzles  110 A-N and sediment dislodged by it are removed from storage tank  100  through drain  120 . In some embodiments, the fluid and the sediment passively drain through drain  120  according to the weight of the fluid and sediment. In other embodiments, the fluid and sediment actively drain through drain  120  according to an external suction source applied to drain  120 . For example, a suction source may connect to drain  120  and remove the fluid and sediment from storage tank  100  through drain  120  without exposure to air. In some embodiments, the suction source includes a hose to be connected from drain  120  to a sediment disposal container, such that the sediment may be removed from storage tank  100  and placed within the sediment disposal container without exposure to air. This may be advantageous where the sediment includes iron sulfide, which may ignite when exposed to air. The suction source may be connected to drain  120  by a clear nipple which indicates storage tank  100  is clean when the fluid sucked from the storage tank no longer appears to carry sediment. For example, where the fluid pumped into storage tank  100  is water, storage tank  100  is clean and may be returned to operation when the clear nipple shows the water running clear. 
     In some embodiments including an external suction source applied to drain  120 , any lines into and out of the storage tank  100  under a predetermined height except for the one or more nozzles  110 A-N are sealed before the suction is applied to drain  120 . Because lines into and out of the storage tank  100  above the predetermined height remain open, pressure within the tank is equalized. The predetermined height may be selected any number of ways based at least in part on the configuration of nozzles  110 A-N and lines into and out of storage tank  100 . For example, the predetermined height may be selected based on the estimated volume of sediment within storage tank  100  and the estimated volume of fluid necessary to dislodge and flush the sediment out of storage tank  100 . To illustrate, if the sediment within storage tank  100  is estimated at three feet high and the fluid necessary to clean the sediment out of storage tank  100  is estimated to be two feet, the predetermined height may be set at five feet. 
     Referring to  FIG. 2 , a close-up view of an example nozzle  210  in a storage tank  200  is shown. Example nozzle  210  includes sub-nozzles  240 A-B and external connection point  230 . As discussed previously with reference to  FIG. 1 , the number and positioning of the one or more sub-nozzles may be chosen to optimize fluid pressure for creating a vortex and dislodging sediment from storage tank  200  and further to facilitate draining of the fluid and sediment through a drain in storage tank  200  by decreasing the likelihood of blockages in the drain. The size of storage tank  200  and the drain, the height of the one or more nozzles  210  off the bottom of storage tank  200 , the type of sediment, and the like may be considered in choosing the number and position of the one or more sub-nozzles  240 . The position of sub-nozzle  240 A directs fluid towards the drain in storage tank  200  to encourage the flow of fluid and sediment and decrease the likelihood of blockages in the drain line by sediment build up. Sub-nozzle  240 A may be positioned 45-90 degrees inward towards the center of storage tank  200  from the tangent line to the circumference. For example, sub-nozzle  240 A may be positioned 22.5 degrees inward towards the center of storage tank  200  from the tangent line to the circumference. Sub-nozzle  240 B is positioned to direct fluid flow perpendicular to the wall of storage tank  200  to aid in creating a vortex and dislodging sediment within storage tank  200 . External connection point  230  connects the nozzle  210  through the wall of storage tank  200  to the outside and allows external fluid sources and pumps to connect to nozzle  210 . These external fluid sources and pumps connect to external connection point  230  and pump fluid through nozzle  210  into storage tank  200  to clean it. In some embodiments, external connection point  230  may be sealed when storage tank  200  is in use, such that the external fluid sources and pumps may be disconnected and used elsewhere as needed. When storage tank  200  must be cleaned, the external fluid sources and pumps may be reconnected to external connection point  230 , which is opened, allowing the fluid to be pumped through nozzle  210 . 
     Referring to  FIG. 3 , an overhead view of the arrangement of nozzles  310 A-C and drain  320  in an example storage tank  300  is shown. Storage tank  300  is cylindrical with three nozzles  310 A-C spaced 120 degrees apart around the wall and six inches from the bottom of storage tank  300 . Drain  320  is placed at the bottom of storage tank  300  to allow for removal of the water and sediment from storage tank  300  without exposure to air. If drain  320  were placed on the wall instead of the bottom of storage tank  300 , the suction source would eventually suck up air from within storage tank  300  once the fluid and sediment level is below the height of drain  320  from the bottom of storage tank  300 . In one embodiment, a 4×3 centrifugal pump may be used to pump water through nozzles  310 A-C at a rate of 880 gallons per minute allowing storage tank  300  to be cleaned more quickly than traditional methods, which require days of disuse. 
       FIG. 4  shows, in flow chart form, an example process for cleaning a storage tank. The flow chart begins at step  410 , where the storage tank is isolated. When the particular storage tank is included in a tank battery, isolating the particular storage tank allows the other tanks in the tank battery to continue operating while the particular tank is cleaned. Isolating the storage tank may optionally include step  415 , where all lines into and out of the storage tank under a predetermined height except for the one or more nozzles are closed. Because lines into and out of the storage tank above the predetermined height remain open, pressure within the tank is equalized. As discussed previously, the predetermined height may be selected any number of ways. Next, at step  420 , a vortex may be created within the storage tank by pumping fluid through the one or more nozzles in the storage tank. As discussed previously, the nozzles may comprise two or more sub-nozzles positioned to dislodge sediment within the storage tank and keep the drain in the storage tank clear of blockages. The process continues at step  430 , where a vacuum source is connected to the drain in the storage tank to remove the fluid and sediment from the storage tank. As discussed previously, where the drain is located at the bottom of the storage tank, the fluid and sediment may be removed from the storage tank without exposure to air. This may be advantageous where the sediment includes iron sulfide, which ignites when exposed to air, because it reduces the associated fire hazard. 
     The scope of the inventions contained within the disclosed subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”