Patent Publication Number: US-2011049015-A1

Title: Water removal and management system

Description:
TECHNICAL FIELD 
     This disclosure relates generally to systems for the removal and management of water in hydrocarbon liquids. 
     BACKGROUND 
     Many mechanical systems rely upon liquid hydrocarbons for fuel, lubrication and/or power transmission. These types of mechanical systems can be negatively affected by the presence of excessive water in the system, especially free water. Free water can develop within a system through a variety of ways, such as by flashing to steam out of the liquid hydrocarbon, by condensing out of the liquid hydrocarbon itself or by condensing out of air or water vapor that may be present in the dead space of the liquid hydrocarbon storage tank. Free water can also develop from heat exchanger leaks and wash downs of equipment. One solution that has been developed to eliminate the presence of water in liquid hydrocarbons is the use of a water separator with a collection reservoir that has a water absorption filter. Examples of water absorption filter materials are cellulose and super absorbent polymers (SAP). Water can also be removed from a system through the use of coalescers, centrifuges, and vacuum dehydration systems. Other solutions for removing water in a tank include forcing dried air through the dead space of the tank or through the fluid in the tank. While these solutions can be effective in certain applications, better solutions for the removal and management of water in liquid hydrocarbon systems are desired. 
     SUMMARY 
     A system is disclosed comprising a tank having an interior volume for holding a liquid fuel or oil, a water absorbent filter, which may comprise super absorbent polymers (SAP), in liquid communication with the interior volume of the tank, an air dryer in fluid communication with the water absorbent filter and a fume filter downstream of the air dryer. The water absorbent filter may be oriented inside or outside of the interior volume of the tank. Further, the air dryer and the fume filter may be oriented outside of the interior volume of the tank. 
     A system is also disclosed for removing at least some water from liquid fuel or oil comprising a tank having an interior volume holding a liquid fuel or oil, a water absorption filter, such as a super absorbent polymer (SAP) filter, downstream of and in liquid communication with the interior volume of the tank, a particulate filter downstream or upstream of the SAP filter to remove particulate contaminant from the fuel or oil and apparatus downstream of and in liquid communication with the particulate filter constructed and arranged to utilize at least some of the filtered fuel or oil. Also disclosed is a return channel directing at least some of the fuel or oil from the apparatus back to the tank and an air dryer upstream of and in fluid communication with the interior volume of the tank to remove at least some moisture from the tank. In lieu of an air dryer, a dry gas from another process may be used. Nitrogen gas will also work to dry water from the liquid. A breather filter, which may include a fume filter, may also be in air communication with the tank. Additionally, the SAP filter is constructed and arranged to remove at least some water from the fuel or oil and also to be regenerated by the fuel or oil. The disclosed apparatus may be an engine, a gearbox, or a hydraulic system. A second water absorption filter is also disclosed in a configuration where the first and second water absorption filters can be regenerated directly by the air drying system. 
     A method to manage the amount of water present in a system having liquid fuel or oil is also disclosed. Such a method may comprise the steps of directing dry air into a tank holding the liquid fuel or oil wherein the fuel or oil has water entrained therewithin; directing the fuel or oil from the tank and through a water absorbent filter, such as a super absorbent polymer (SAP) filter, to remove at least some of the water or to regenerate the SAP filter; directing the fuel or oil from the SAP filter through a second filter to remove at least some contaminant from the fuel or oil; directing the filtered fuel or oil from the second filter to apparatus utilizing at least some of the filtered fuel or oil; and directing at least some of the filtered fuel or oil from the apparatus back to the tank. In lieu of dry air, a dry gas, such as nitrogen may also be used. By the use of the term “entrained”, it is meant that water exists in the presence of the liquid fuel or oil as free water in the same vessel that stores the liquid fuel or oil or as dissolved moisture within the liquid itself. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first embodiment of a water management and removal system. 
         FIG. 2  is a schematic view of a second embodiment of a water management and removal system. 
         FIG. 3  is a schematic view of a third embodiment of a water management and removal system. 
         FIG. 4  is a schematic view of a fourth embodiment of a water management and removal system. 
         FIG. 5  is a schematic view of a fifth embodiment of a water management and removal system. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary aspects of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     As illustrated in  FIGS. 1-3 , three embodiments of a water management and removal system  100 ,  200 ,  300  are disclosed. One aspect of each disclosed embodiment is a super absorbent polymer or SAP filter  110 ,  210 ,  310 . In general, super absorbent polymers or SAPs are useful in applications where it is necessary or desired to absorb water. Examples of SAPs are polymers and copolymers of polyacrylates, polyacrylic acids, polyacrylamides, polyesters, polysaccharides. SAPs are particularly useful in water absorption applications because they can absorb a very large amount of water per unit weight of SAP. For example, SAPs can absorb up to 500 times their weight in water in certain configurations and applications. Another feature of SAPs is that absorbed water within the SAP can be driven out such that the SAP can be made available for future water absorption. One method for drying out SAPs includes applying pressure to the SAP. Because SAP expands greatly as moisture is absorbed, placing pressure on the SAP to reduce its volume will cause the dissolved moisture to be expelled. Another method for drying SAP is to expose the SAP to elevated temperatures. Yet another method for drying SAP is to expose the material to the atmosphere or relatively dry air where the moisture will wick out of the fibers and evaporate. This dynamic is also possible when exposing the SAP to a relatively dry liquid, such as a liquid hydrocarbon. In this case, the dry liquid will draw the water out of the SAP up to a point where the liquid hydrocarbon is near its saturation point. Additionally, it should be noted that SAP can become mobile within a liquid system and can cause contamination within the system itself if not contained sufficiently within a housing. SAP filter  110 ,  210 ,  310  is constructed to prevent the SAP material from contaminating system  100 ,  200 ,  300  in this way. 
     In the particular embodiment shown in  FIG. 1 , SAP filter  110  is shown as being used in a liquid fuel or oil system  100  comprising a tank  120 . Tank  120  is for storing the liquid fuel or oil  122 . Tank  120  can be a storage vessel for use in a vehicle or for use in a stationary application, such as a bulk oil or fuel storage tank. As shown, tank  120  has an interior volume  121  wherein the liquid fuel or oil  122  is stored. Above the liquid fuel or oil  122  is a head space volume  121   a . Tank  120  also has a bottom portion  123  at which line  120   a  provides liquid communication between the tank  120  and the SAP filter  110 . The installation of line  120   a  at the bottom portion  123  of tank  120  is advantageous insofar as that any free water  124  that may collect at the bottom portion  123  of tank  120  will be directed to SAP filter  110  where it can be absorbed. 
     It should also be noted that SAP filter  110  may be replaced by water absorption filters of other types without departing from many of the concepts presented herein. For example, cellulosic water absorption filters or cotton based filters, may be used. By the use of the term “water absorption filter” it is meant to include at least cellulosic based filters and SAP based filters. 
     Also shown in  FIG. 1  is breather filter  140 . Filter  140  is for allowing atmospheric air leave tank  120  as the level of the liquid fuel or oil  122  rises within tank  120  or as dried air is introduced into head space volume  121   a  via an air drying system  130 , discussed later. Breather filter  140  is also for scrubbing fumes that are present in head space volume  121   a  before the air is ejected into the atmosphere so as to minimize the negative effects on the environment. Optionally, the ejected air can be routed to another part of the system, such as an engine air intake. In the embodiment shown, breather filter  140  is in fluid communication with head space volume  121   a  via line  140   a . Breather filter  140  can also be configured with a desiccant material or an adsorbent to dry out atmospheric air that may need to enter the tank through breather filter  140  as the liquid level in the tank  120  is reduced and a vacuum or partial vacuum is created. 
     Another aspect of the disclosure is air drying system  130 . Air drying system  130  is used to pump dry air into the head space volume  121   a  of the tank  120  via line  130   a . The dry air delivered by air drying system  130  can be created in a variety of ways. For example, atmospheric air can be compressed to condense and remove the moisture. Atmospheric air can also be dried through the use of refrigeration dryers, pressure swing adsorption dryers, membrane dryers and/or a combination of coolers and blowers. In some applications a combination of air compression and filters may be used. Further, dry gases from other sources or processes within the system may be used instead of dry air. Nitrogen can also be used. By the use of the term “dry gas” and it is meant to include any gas that is capable of absorbing moisture from a liquid hydrocarbon and/or from the head space of a tank holding a liquid hydrocarbon. The term “dry gas source” should be taken to mean any system, including those mentioned above, capable of producing and/or delivering a dry gas. One skilled in the art will appreciate that the water absorbing capability of the dry gas will increase as the moisture content within the dry gas is lowered. In many applications, it is beneficial to utilize a dry gas having a very low initial moisture content. The effect of passing a dry gas through the head space volume  121   a  of tank  120  is that the dry gas will absorb moisture directly out of the liquid fuel or oil  122 , thus creating a drying effect. 
     Air drying system  130  is particularly useful for drying moisture out of liquid fuel or oil  122  when liquid fuel or oil  122  is agitated or has other movement within tank  120 . This is true even in circumstances where the total amount of water within the tank  120  exceeds the saturation point of the liquid fuel or oil  122 . However, in circumstances where the liquid fuel or oil  122  is essentially stationary or stagnant, the length of time for air drying system  130  to remove the moisture from the liquid fuel or oil  122  can dramatically increase. This is especially true in situations where free water  124  that has collected at the bottom of the tank is slow to absorb back into the liquid oil or fuel. This is the case even when the water present in the liquid oil or fuel is well below the saturation point. In any event, air drying system  130 , given adequate time to dehydrate liquid oil or fuel  122 , can reduce the moisture content of liquid oil or fuel  122  to a percent saturation of about 3%. 
     Other factors that affect the effectiveness of air drying system  130  include the temperature of the liquid fuel or oil  122  and the flow rate of dried air introduced into the head space volume  121   a  of tank  120 . As the temperature of the liquid fuel or oil  122  is increased, the air drying system  130  becomes more effective. Thus, a system which includes a mechanism for heating the liquid fuel or oil  122 , which is necessary for some end use applications and/or occurs in end use applications, will have the beneficial effect of allowing the air drying system  130  to remove a greater degree of moisture from the liquid fuel or oil  122 . This benefit occurs because hot fuel or oil has a higher saturation point than fuel or oil at a lower temperature and will therefore have a lower percent saturation at higher temperatures for a fixed amount of dissolved water. With respect to the air flow rate from the air drying system  130 , a roughly proportional drying rate is achieved with a change in air flow rate in some applications. For example, reducing the air flow rate by half can double the length of time that it will take to dehydrate the liquid fuel or oil  122  under certain circumstances. However, it should be noted that these relationships occur within a reasonable range of values and that there is also a minimum and maximum rate within which each particular process will optimally operate. 
     Yet another aspect of system  100  is apparatus  150 . Apparatus  150  represents an end use device that is capable of utilizing the liquid fuel or oil  122  stored within tank  120 . By way of non-limiting examples, apparatus  150  may be an engine, a hydraulic system or a gearbox. As shown in  FIG. 1 , apparatus  150  is in liquid communication with tank  120  via lines  120   a  and  150   a  where a supply of liquid fuel or oil  122  can be delivered to apparatus  150 . Apparatus  150  may include a pump (not shown) to achieve this purpose. Apparatus  150  is also shown as being protected from potentially harmful contaminants by particulate filter  160 . As shown, particulate filter  160  is downstream of SAP filter  110  although other locations may be desirable for a particular application. Many types of filters capable of removing particulate matter from a liquid fuel or oil are useful for this purpose. In applications where apparatus  150  does not consume all of the delivered liquid fuel or oil  122 , the unused portion can be returned to tank  120  via channel or line  150   b . In many applications, the unused portion of liquid fuel or oil  122  is heated by apparatus  150  or a separate device which, as mentioned previously, has the beneficial effect of enhancing the moisture removal process. The system will also effectively remove water from the liquid fuel or oil in applications where all the liquid fuel or oil is consumed at apparatus  150  and no return line  150   b  is present. 
     In operation, system  100  will effectively maintain the moisture content of the liquid fuel or oil  122  at an acceptable level and will also prevent the delivery of free water  124  to apparatus  150  which could cause catastrophic damage. When SAP filter  110  is used in conjunction with air drying system  130 , such as in the configuration shown in  FIG. 1 , an enhanced system is developed. One beneficial aspect of this combination it is that SAP filter  110  can be sized and configured to absorb an initial amount of water within the system that may be difficult to extract from the liquid fuel or oil  122  with air drying system  130 . Such a circumstance can occur for a variety of reasons. For example, the liquid temperature could be initially low at system start-up, free water could have collected in the tank through condensation during a stagnant period, previously dissolved moisture could flash to steam, or the fuel system could have been unexpectedly contaminated with a large volume of water. Additionally, leaks in heat exchangers and rain can also introduce free water into the system. As a result, the use of SAP filter  110  in system  100  will enable the liquid fuel or oil  122  to be maintained at or even slightly below the moisture saturation point under a variety of circumstances. 
     However, another dynamic occurs after the system has been allowed to run for a period of time. Once air drying system  130  is capable of adequately removing moisture from liquid oil or fuel  122 , the moisture level in the liquid or fuel  122  will be reduced to well below saturation, especially if apparatus  150  adds heat to the system. As the liquid oil or fuel  122  continues to become dehydrated below the saturation point, the relatively dry fuel will actually begin to absorb the initially captured moisture out of SAP filter  110 . As this occurs, the liquid fuel or oil  122  will continue to be dried by air drying system  130  and SAP filter  110  will continue to be dried by liquid oil or fuel  122  such that equilibrium is maintained. Initial tests show that SAP material will give up at least 80% of the dissolved moisture when exposed to a liquid hydrocarbon initially at 55° C. and having a percent saturation of about 3%. Thus, liquid fuel or oil  122  will automatically regenerate SAP filter  110  such that SAP filter  110  becomes available to absorb additional moisture when new free water enters the system or when air drying system  130  is no longer available or capable of removing moisture from the system. Thus, SAP filter  110  and air drying system  130  operate cooperatively to result in an effective water management system that automatically regenerates itself without the need for special controls or processes. Even more, system  100  requires no direct supervision and does not need to be shut down in order to regenerate the SAP filter  110 . Further, system  100  will work effectively to remove and manage water under both unsteady and steady state conditions. As a result, system  100  is potentially smaller, more compact, more energy efficient and more efficient at removing water than typical existing technologies. 
     Another feature of the disclosure is that the SAP filter  110  can be configured to act as a safety device for apparatus  150 . SAP material expands significantly as it absorbs water. By taking advantage of this property, a filter housing can be constructed such that flow will be blocked off to apparatus  150  by the expanding SAP material. Thus, SAP filter  110  can be configured to allow flow to pass through the filter under a normal expansion range, but to shut off flow past a certain expansion point. Thus, when SAP filter  110  is exposed to a water concentration that is in excess of its capacity to safely handle, the SAP material in the filter will expand to shut flow off to the system. Thus, the shut off action of SAP filter  110  will protect susceptible end use equipment from potentially catastrophic damage. 
       FIG. 4  shows a modified embodiment of the system shown in  FIG. 1 , the primary difference being the addition of a second water absorption filter, SAP filter  110   a . Therefore, the same figure numbers have been used wherein elements of the schematics are similar. As shown, SAP filter  110   a  is placed in a parallel arrangement with SAP filter  110  via lines  180   a ,  180   b  and  180   c . This arrangement allows for the system to operate with only one SAP filter at a time and adds flexibility to the system in at least two ways. First, should one of the SAP filters fail or shut off fuel flow to apparatus  150 , the other SAP filter can be brought on-line such that apparatus  150  can continue to operate. Second, the SAP filter that is not in use can be regenerated while it is off-line. The alternation of the SAP filters can be controlled by a system (not shown) such that the filters are regenerated on a time based schedule, fluid pressure drop or another relevant variable. In the embodiment shown in  FIG. 4 , additional compressed air lines  130   b  and  130   c  are piped to each SAP filter  110 ,  110   a  such that the filters can be directly regenerated by the air drying system  130 . In such an application, it is beneficial to install vents  170  such that the air injected into the SAP filters,  110  and  110   a  can escape the system.  FIG. 4  also shows an additional particulate filter  160   a  that functions in a similar manner as that described for particulate filter  160 . One skilled in the art will appreciate that  FIG. 4  is a schematic description of the system and does not necessarily show all required piping, valves and controls that an actual system would require. 
       FIGS. 2 ,  3  and  5  show alternative embodiments of systems that are particularly useful in bulk storage applications that also utilize an SAP filter. Many of the elements of the embodiments shown in  FIGS. 2 and 3  are similar to those found in the embodiment of  FIG. 1 . As such, the entire description of  FIG. 1  is hereby incorporated into the descriptions for the embodiments of  FIGS. 2 and 3 . 
       FIGS. 2 and 3  show systems  200 ,  300  for storing and managing the moisture content of a liquid oil or fuel  222 ,  322 . In the exemplary embodiment shown, system  200 ,  300  includes an SAP filter  210 ,  310 ; a tank  220 ,  320 ; an air drying system  230 ,  330 ; and a filter  240 ,  340 . Many aspects of each of these elements are similar in nature to corresponding elements of system  100 . Therefore, these elements will be described here to the extent that they differ significantly from the disclosure for system  100 . 
     One aspect of system  200 ,  300  is tank  220 ,  320  which is for storing liquid oil or fuel  223 . Tank  220 ,  320  can be a storage vessel for use in a vehicle or in a stationary application, such as a bulk oil or fuel storage tank. In the exemplary embodiment shown at  FIGS. 2 and 3 , tank  220 ,  320  has an interior volume  221 ,  321 ; a head space volume  221   a ,  321   a ; and a bottom portion  223 ,  323  that are similar to that described for system  100 . In contrast to the embodiment shown in  FIG. 1 , tank  220 ,  320  is not shown as being directly connected to an air drying system or a fume breather filter. However, it should be appreciated that such a configuration may be desirable in certain applications. Additionally, it should be appreciated that in systems where the tank  220 ,  320  is stationary, as is the case in bulk oil or fuel storage applications, that a large quantity of water can form at the bottom of the tank. If this water is not removed, then it is possible that microbial growth will occur that will contaminate the fuel. Microbial growth represents a significant problem in the bulk fuel and oil storage industry. 
     The SAP filter  210  of  FIG. 2  is for removing moisture from tank  220  and from liquid oil or fuel  222 . As shown, SAP filter  210  is in fluid communication with tank  220  via line  220   a . SAP filter  210  is also in fluid communication with air drying system  230  and filter  240  via lines  230   a  and  240   a , respectively. In the configuration shown, SAP  210  is constructed with a liquid inlet port to which line  220   a  is attached, an air inlet port to which line  230   a  is attached and an air outlet port to which line  240   a  is attached. In operation, liquid oil or fuel  222  and/or free water  224  that has collected at the bottom of tank  220  flow through line  220   a  and into SAP filter  210 . Once the liquid oil or fuel  222  or the free water  224  contacts the SAP filter  210 , the SAP filter  210  begins to absorb moisture. 
     The SAP filter  320  of  FIG. 3  is also for removing moisture from tank  320  and from liquid oil or fuel  322 . As shown, SAP filter  310  is in fluid communication with tank  320  by virtue of being directly placed within the interior volume  321  of tank  320 . In the configuration shown, SAP filter  310  is submerged in the liquid oil or fuel  322  and located at the bottom portion  323  of tank  320 . In the configuration shown, SAP filter  310  is constructed to allow the liquid oil or fuel  322 , or any free water  324  that has collected at the bottom of tank  320 , to enter the SAP filter  310 . Once the liquid oil or fuel  322  and/or free water  324  contacts the SAP filter  310 , the SAP filter  310  begins to absorb moisture. A benefit of placing the SAP filter  310  directly within the tank  320  is that the system  300  can be installed in retrofit applications where a connection port may not exist at the bottom of the tank  320 . System  300  is also useful for in ground tanks where it is not possible to make a connection to the bottom of the tank  320 . 
     In contrast to the embodiment of  FIG. 1 , air drying system  230 ,  330  delivers dried air directly to SAP filter  210 ,  310  through line  230   a ,  330   a . The dry air that is injected into SAP filter  210 ,  310  from air drying system  230 ,  330  acts to absorb the moisture out of the SAP filter  210 ,  310  and to the atmosphere via line  240   a ,  340   a  and fume filter  240 ,  340 . Thus, the SAP filter  210 ,  310  can be continually regenerated such that SAP filter  210 ,  310  always remains available for moisture absorption. In some applications, a control system (not shown) can be provided to cycle the air drying system  230 ,  330  on and off to maintain a specific moisture content level for the liquid oil or fuel  222 ,  322  in the tank  220 ,  320 . A control system can also be installed to cycle the air drying system  230 ,  330  on and off based on sensing an amount of free water  224 ,  324  that has collected at the bottom of the tank. 
     The embodiment of  FIG. 5  is similar in many aspects to that shown and described for  FIG. 2 . Therefore, the same figure numbers have been used wherein elements of the schematic are similar. The primary difference shown in  FIG. 5  is the addition of a kidney loop pump  250 , particulate filter  260  and return channel/line  240   b . As shown, kidney loop pump  250  is piped into line  220   a  via lines  250   a  and  250   b . This arrangement allows for pump  250  to circulate liquid oil or fuel  222  out of tank  220 , through SAP filter  210  and particulate filter  260  and back into tank  220  via lines  240   a  and  240   b . A check valve or isolation valve (not shown) can be installed in line  220   a  between the connection points of lines  250   a  and  250   b  to prevent the reverse flow of liquid through line  220   a  while pump  250  is in operation. The addition of this type of circulation loop is particularly beneficial in a bulk fuel application because there can be long periods where the liquid oil or fuel  222  is stagnant. In such a situation, the gravity flow rate to SAP filter  210  of liquid from tank  220  is sometimes too small to effectively remove water from tank  220  and/or liquid oil or fuel  222 . Thus, the addition of a pump allows for the system to control water levels in the liquid oil or fuel  222  and tank  220  in a manner that is independent of the actual use of the fluid in the tank. The cycling of pump  250  can be controlled by a variety of conditions. For example, pump  250  can be controlled based upon the measured moisture content of the liquid oil or fuel  222  within the tank  220 , the sensed presence of free water at the bottom  223  of the tank  220  and/or a timed schedule. One skilled in the art will appreciate that  FIG. 5  is a schematic description of the system and does not necessarily show all required piping, valves and controls that an actual system would require. 
     The above disclosed systems can be utilized as discussed above and also according to a method wherein dry air is directed into a tank  120  holding the liquid fuel or oil  122  wherein the fuel or oil  122  has water entrained therewithin. The fuel or oil  122  can also be directed from the tank  120  and through a super absorbent polymer (SAP) filter  110  to remove at least some of the water or to regenerate the SAP filter  110 . The fuel or oil  122  can also be directed from the SAP filter  110  through a particulate filter  160  to remove at least some contaminant from the fuel or oil  122  and directed from the particulate filter  160  to apparatus  150  utilizing at least some of the filtered fuel or oil  122 . From apparatus  150 , some of the filtered fuel or oil  122  can be directed from the apparatus  150  back to the tank  120 . 
     The above includes examples incorporating inventive principles. Many embodiments can be made.