Abstract:
A system and method to vaporize a process or feed water stream does so in a liquid pool zone of a vessel as the stream comes into contact with a heating medium that is less volatile than the process stream. To keep the pool hot, the heating medium can be recirculated through a heater of a pump-around loop or a heater can be placed in the liquid pool. As the process stream is vaporized, any solids present in the process stream come out of the process stream and move into the heating medium. These solids may be further removed from the heating medium in the pool or in the pump-around loop. The vaporized process stream can be further condensed. Any heat recovered can be used to pre-heat the process stream or used in the pump around loop&#39;s heater in case of mechanical vapor recovery.

Description:
BACKGROUND 
       [0001]    This disclosure is in the field of vaporization and desalination processes such as, but not limited to, those used in mono ethylene glycol (“MEG”) reclamation applications, seawater desalination applications, total dissolved solids reduction applications, and general process water treatment for reuse or disposal. 
         [0002]    Current vaporization and desalination processes are complicated, expensive, and typically require extensive pretreatment. In some cases, the cost of pretreatment exceeds the cost of the actual vaporization or desalination processes. U.S. Pat. No. 8,652,304 B2 (“Nazzer”) discloses a method of extracting dissolved or undissolved solids from a mixture of water and a process liquid or stream. The mixture is introduced into a mixing zone within or upstream of a separation vessel where it is further mixed with a recycle fluid extracted from a liquid pool zone of the separator vessel and pumped through a heat exchanger. 
         [0003]    Vaporization occurs in this mixing zone (where more than 99% of the volatile components of the feed stream are vaporized). The resulting stream is then transferred to the separator vessel in which the vapor is separated, with the solid and liquid components falling into the liquid pool zone of the separator vessel. A portion of these solids and liquids that bond to these solids then passes through a stripping zone of the separator vessel. Water residing within the stripping zone displaces the liquids bound to the solids and an aqueous waste stream with dissolved or nondissolved solids results. 
         [0004]    Because this method requires a mixing zone for vaporization outside of the liquid pool, the required equipment is difficult to design and prone to scaling and plugging. The method also does not allow for vaporization within the liquid pool and requires the heating medium—i.e., the recycle fluid, immiscible with the process stream and lighter than the water in the stripping zone—to be recycled at a rate of at least ten times that of the process feed rate. This high recycle rate is required because the method must limit the temperature difference between the recycle fluid and the process stream in order to avoid thermal degradation effects. Additionally, the method does not allow for partial vaporization with a blowdown. 
         [0005]    Last, the method requires a stripping zone for solids removal. A stripping zone is prone to corrosion because of unvaporized (solids) components from the process stream. The stripping zone also presents safety concerns due to the risk of higher temperature oil contacting water. To reduce the safety concern, the oil must be cooled before it touches the water in the stripping zone, but cooling the oil increases its viscosity and ineffective solids separation results. 
       SUMMARY 
       [0006]    The present disclosure simplifies the system and method of vaporizing a process stream and reduces the cost of doing so. 
         [0007]    Vaporization in a mixing zone outside of the liquid pool does not occur in embodiments of the system and method, nor do the system and method have a stripping zone for solids removal. The system and method is not limited to a light heating medium relative to the process stream and, in some embodiments, does not have an immiscible heating medium. Any pre-mixing of the process stream and heating medium may be done at a level below that required for vaporization of the process stream. Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool. 
         [0008]    Embodiments of the system and method may disperse the process or feed water stream into a liquid pool containing a hot heating medium that is less volatile than the process or feed water stream. To keep the pool hot, the heating medium can be recirculated through a heater in a pump-around loop. Alternatively or additionally, a heater can be placed in the liquid pool. 
         [0009]    As the process stream is vaporized, any dissolved or undissolved solids present in the process or feed water stream come out of the stream and move into the heating medium. The solids that move into the heating medium may be further removed from the heating medium within the vessel or in a separator located in the pump-around loop. If the removal of solids and unvaporized liquids occurs in the vessel, the vessel should include internals of a kind known in the art to separate the unvaporized portion of the process or feed water stream from the heating medium. If the removal of the solids and unvaporized liquids occurs in a separator in the pump-around loop, the separator can be a hydrocyclone, centrifuge, particulate filter, settling tank, or some other piece of separation device equivalent to these. 
         [0010]    In some embodiments, the vaporized process or water stream can be condensed or compressed and condensed. Heat recovered during condensing can be used to pre-heat the process stream prior to its introduction into the liquid pool, or to heat the heating medium in the pump around loop. 
         [0011]    The system and method can be used in applications such as but not limited to MEG reclamation; seawater desalination; steam generation; total dissolved solids (“TDS”) reduction for produced water, desalter wash water, fracking flowback water, and amine reclamation. Unlike prior art systems and methods, there is no requirement for pretreatment of the process or feed water stream or low temperature differentials between the vaporization temperature of the stream and heating medium (e.g., limited to 10° C. above the vaporization temperature due to the risk of scaling in the heat exchanger in the pump-around loop). 
         [0012]    The embodiments of this disclosure may simplify the system and method to vaporize a process stream; reduce the costs associated with prior art vaporization systems and processes; generate a much smaller discharge stream relative to prior art systems and methods; and eliminate the design and operational challenges presented by mixing zones located outside of the liquid pool zone of the vessel and stripping zones for solids removal. The disclosure also eliminates the need for light heating mediums relative to the process or feed water stream, and eliminates the need for immiscible heating mediums. The disclosure also does not require the low temperature differential between the stream and heating medium or recycle rates of at least 10 times greater than that of the process feed. 
         [0013]    The disclosure also reduces, and potentially eliminates, pretreatment for the process or feed water stream while at the same time minimizing or eliminating scaling and fouling of equipment. Any pre-mixing of the process or feed water stream and the heating medium that occurs outside of the liquid pool zone may be done at a level below that at which the stream vaporizes. Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    So that the above recited features can be understood in detail, a more particular description may be had by reference to embodiments, some of which are illustrated in the appended drawings, wherein like reference numerals denote like elements. It is to be noted, however, that the appended drawings illustrate various embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments. 
           [0015]      FIG. 1  is a schematic of an embodiment of a system and method to vaporize a process or feed water stream. A process stream having dissolved or undissolved solids is routed to a heating medium pool of a vessel. As the process stream vaporizes, the solids in the process stream, both dissolved and undissolved, come out of the process stream and move into the heating medium. The vessel includes internals to allow the separation of the solids from the heating medium and remove the solids out of the vessel. A pump-around loop recycles and heats the heating medium. If any pre-mixing of the process stream and heating medium occurs outside of the liquid pool (see  FIG. 6 ), the pre-mixing may be at a level below that at which vaporization occurs. Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool. 
           [0016]      FIG. 2  is an embodiment of the system and method. The pump-around loop includes a separator for removing solids. The separator can be a hydrocyclone, centrifuge, particulate filter, settling tank, or some other piece of separation device equivalent to these. 
           [0017]      FIG. 3  is an embodiment of the system and method. The vaporized process stream is partially condensed. 
           [0018]      FIG. 4  is an embodiment of the system and method. Heat recovered from condensing is used to pre-heat the process stream prior to it being routed to the heating medium pool of the vessel. 
           [0019]      FIG. 5  is an embodiment of the system and method. The vaporized process stream is compressed and this pressurized process stream is condensed in the pump-around loop to help heat the heating medium being recycled in the loop. 
           [0020]      FIG. 6  is an embodiment of the system and method. Pre-mixing of the process stream and heating medium occurs outside of the liquid pool zone of the vessel but at a level below that needed for vaporization. The pump-around loop could include a separator for removing solids (see e.g.  FIG. 2 ). Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool. 
       
    
    
     ELEMENTS AND NUMBERING USED IN THE DRAWINGS AND DETAILED DESCRIPTION 
       [0000]    
       
         
           
               10  System or method 
               15  Process stream 
               15 A Process stream prior to preheating 
               15 B Pre-heated process stream 
               17  Mixer within or outside of  20   
               20  Vessel 
               21  Liquid pool zone 
               23  Heating medium 
               24  Interior volume 
               25  Unvaporized (dissolved or undissolved solids) portion of  15   
               27  Vapor separation zone 
               29  Vaporized volatile components of  15   
               30  Vaporized process stream 
               35  Removed heating medium stream or mixture (heating medium  23  and unvaporized portion  25 ) 
               40  Pump-around loop 
               41  Heater 
               45  Heated recycle stream substantially unvaporized portion-free or with a reduced unvaporized portion  25  (relative to removed stream or mixture  35 ) 
               47  Separator or separator device (solids removal device such as a hydrocyclone, centrifuge, particulate filter, settling tank or their equivalents) 
               50  Heating medium stream substantially unvaporized portion-free or with a reduced unvaporized portion  25  (relative to stream or mixture  35 ) 
               60  Condenser 
               65  Partially or totally condensed process stream 
               70  Compressor 
               75  Pressurized stream 
           
         
       
     
       DETAILED DESCRIPTION 
       [0044]    In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
         [0045]    In the specification and appended claims, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connect with” or “in connection with via one or more elements”; and the term “set” is used to mean “one element” or “more than one element”. Further, the terms “couple”, “coupling”, “coupled”, “coupled together”, and “coupled with” are used to mean “directly coupled together” or “coupled together via one or more elements”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and “downwardly”, “upstream” and “downstream”, “above” and “below”, and other like terms indicated relative positions above or below a given point or element and are used in this description to more clearly describe some embodiments of the disclosure. 
         [0046]    Embodiments of a system and method to vaporize volatile components of a process or feed water stream achieve vaporization of those components in the liquid pool zone of the vessel when the stream contacts a heating medium residing in the liquid pool zone. The vessel is arranged to directly receive the process or feed water stream, thereby eliminating pre-treatment between it and the upstream process providing the stream. A pump-around loop heats a portion of the heating medium and recycles this heated portion back to the vessel. 
         [0047]    The heating medium—which can be miscible or substantially immiscible with the stream and can be lighter or heavier than the stream—is maintained at an operating temperature required for the desired vaporization effects. Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool. The vessel can also make use of blowdown to remove solids formed during the vaporization of the process or feed water stream. A separate vessel located in the pump-around loop can be used for liquids-solids separation. 
         [0048]    The different arrangements of the system and method  10  as shown in  FIGS. 1 to 6  route a process or feed water stream  15  into a vessel  20  whose interior volume  24  is defined by a liquid pool zone  21  and a vapor separation zone  27 . A heating medium  23  resides within the liquid pool zone  21  and this heating medium  23  is used to vaporize the volatile components  29  of the process stream  15 . Mixing of the process stream  15  and heating medium  23  occurs naturally within the liquid pool zone  21  as the process stream  15  enters the zone  21 . 
         [0049]    The now vaporized portions  29  of the process stream  15  migrate to a vapor separation zone  27  of the vessel  20  and are removed as a vaporized process stream  30 . The vaporized process stream  30  can be routed to a condenser  60 , as shown in  FIGS. 3 and 4 , to produce a partially condensed process stream  65 . Heat from the condenser  60  can be recovered and used to raise the temperature of the process stream  15 A so that stream  15  flows into the liquid pool zone  21  as a pre-heated process stream  15 B. 
         [0050]    The vaporized process stream  30  can also be routed to a compressor  70 , as shown in  FIG. 5 . The now pressurized process stream  75  is condensed in the pump-around loop  40 , with heat being recovered and used to heat the recycle stream  45 . 
         [0051]    As the volatile components  29  of the process stream  15  vaporize, the unvaporized (dissolved and undissolved solids) portion  25  of the process stream  15  moves into the liquid pool zone  21  along with the heating medium  23 . The solids  25  can be separated from the heating medium  23  either within the vessel  20  or within a separator  47  located in the pump-around loop  40 . No stripping zone is used for solids  25  removal. 
         [0052]    The separator  47  used in the pump-around loop  40  can be any separator suitable, including but not limited to a hydrocyclone, centrifuge, particulate filter, settling tank, or some other piece of separation device equivalent to these. A heating medium stream  50  with reduced amounts of, or without, unvaporized portion  25  exits the separator  47  and passes through the heater  41 . The heated recycle stream  45  then recycles back to the liquid pool zone  21  of the vessel  20 . The heated recycle stream  45  may include some portion of the dissolved or undissolved solids  25  of the process stream  15 . 
         [0053]    The heating medium  23  is maintained at an operating temperature that provides the desired vaporization effects. The heating medium  23  can be any heating medium depending on the make-up of process or feed water stream  15  and application-specific requirements. For example, the heating medium  23  could be one that one that is lighter than, heavier than, or the same density as the process stream  15 . The heating medium  23  could also be one that forms either a homogeneous or heterogeneous mixture with the process stream  15 . However, the heating medium  23  is less volatile than the volatile components  29  of the process stream  15 . 
         [0054]    To keep the heating medium  23  at the selected operating temperature, a heater (not shown) can be placed in the liquid pool zone  21 . Alternatively or additionally, a removed stream  35  of the heating medium  23 , which may include solids  25  residing within the liquid pool zone  21 , can be removed from the vessel  20  and routed to the pump-around loop  40  and its heater  41 . A heated recycle stream  45  that may include dissolved and undissolved solids  25  then recycles back to the liquid pool zone  21 . 
         [0055]    An embodiment of a method to vaporize a process stream includes:
       routing the process (or feed water) stream  15  directly into the liquid pool zone  21  of the vessel  20  where it becomes mixed with a heating medium  23  that is less volatile than the process stream  15  and maintained at an operating temperature determined by vaporization requirements to vaporize a volatile components portion  29  of the process stream  15 ; and   removing the vaporized portion  29  of the process stream  15  from the vapor separation zone  27  of the vessel  20  as a vaporized process stream  30 .       
 
         [0058]    Prior to the process stream  15  entering the liquid pool zone  21  there may be no pre-treatment of the stream  15  as it exits the upstream process providing the stream  15  and there may be no mixing of the process stream  15  with the heating medium  23 . Pretreatment means treatment such as but not limited to chemical dosing, filtration using selectively permeable membranes, separators, or the use of ion exchange, deaerators or blowdown prior to the process stream  15  entering vessel  20  (or some combination of the above pretreatment methods). (Coarse straining of a kind known in the art and typically done ahead of pretreatment might be used if the feed is taken directly from a natural body of water or from a source with excessive undissolved solids.) If any pre-mixing of the process stream  15  and heating medium  23  occurs outside of the liquid pool zone  21  (see e.g. mixer  17  in  FIG. 6 ), the pre-mixing may be done at a level below that at which vaporization occurs. Therefore, vaporization of the process stream  15  occurs within the liquid pool zone  21  of the vessel  20 . 
         [0059]    Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid  15 ,  45  when it enters the liquid pool  21 . The amount of vaporization that occurs in pre-mixing may be less than that which occurs in the liquid pool. For example, during normal (non-turndown) operations no more than about 20% or about 5% of the volatile components in the stream  15  may vaporize during pre-mixing. If the amount of vaporization does exceed that of the liquid pool, during normal operations vaporization during pre-mixing should not exceed about 80% or about 90% of the volatile components. Limiting the amount of vaporization during pre-mixing helps avoid the design challenges and scaling and plugging problems associated with the mixing zone of the prior art (see Background). 
         [0060]    The heating medium  23  and process stream  15  can form a heterogenous or homogenous mixture when residing within the liquid pool zone  21 . Additionally, the density of the heating medium  23  can be greater than, less than, or equal to that of the process stream  15 . 
         [0061]    The method can also include removing a portion  35  of the heating medium  23  residing in the liquid pool zone  21  of the vessel  20 ; raising a temperature of the removed portion or stream  35  to produce a heated recycle stream  45 ; and routing the heated recycle stream  45  back to the liquid pool zone  21 . The removed stream  35  can also be routed to a separator  47  to produce a heating medium stream  50  substantially unvaporized portion-free or with a reduced unvaporized portion  25 . Once heated by heater  41 , it can be returned to the liquid pool zone  21  as the heated recycled stream  45  (also substantially unvaporized portion-free or with a reduced unvaporized portion  25 ). 
         [0062]    Last, the method can also include condensing at least a portion of the vaporized process stream  30 . Heat recovered from the condenser  60  can be used as pre-heating to raise the temperature of at least a portion of the process stream  15 A prior to the process stream  15 B directly entering the liquid pool zone  21  of the vessel  20 . Alternatively or additionally, the method can include compressing at least a portion of the vaporized process steam  30 . The pressurized stream  75  is then condensed in the pump-around loop  40  and used to raise the temperature of the recycle stream  45 . 
         [0063]    An embodiment of a system to vaporize a process stream includes a vessel  20  arranged to contact a process or feed water stream  15  exiting an upstream process and route the process stream  15  into a heating medium  23  residing within the liquid pool zone  21  of the vessel  20 . The interior volume  24  of the vessel  20  does not include a stripping zone for solids  25  removal. The heating medium  23  is less volatile than the process stream  15  and maintained at an operating temperature determined by vaporization requirements. The vaporized volatile components  29  of the process stream  15  migrate to the vapor separation zone  27  of the vessel  20 . 
         [0064]    A pump-around loop  40  is arranged to receive a portion  35  of the mixed heating medium  23  along with the non-volatile (dissolved and undissolved) components  25  of the process stream  15  that have moved into the heating medium  23  and then return the portion  35  back to the liquid pool zone  21  as a heated recycle stream  45 . The pump-around loop  40  of the system can also include a heater  41  as well as a separator  47  arranged upstream of the heater  41  so that a substantially solids-free or reduced solids stream  45  is being returned to the vessel  20 . 
         [0065]    Prior to contacting the heating medium  23 , the process stream  15  may not be mixed with the heating medium  23  outside of the liquid pool zone  21  of the vessel  20 . If any pre-mixing of the stream  15  and heating medium  23  occurs, the mixing may be at a level below that required for vaporization of the volatile components  29 . Pre-mixing may also be done to provide a relatively small amount of vaporization to enhance the pre-mixing and accelerate the fluid when it enters the liquid pool  21 . 
         [0066]    The system can also include a condenser  60  arranged to receive at least a portion of a vaporized process stream  30  exiting the vapor separation zone  27  of the vessel  20 . Heat recovered from the condenser  60  can also serve as a pre-heater to raises the temperature of the process stream  15 A prior to the process stream  15 B directly entering the liquid pool zone  21  of the vessel  20 . 
         [0067]    The system may include a compressor  70  arranged to receive at least a portion of the vaporized process stream  30 . Heat recovered from condensing the pressurized stream  75  can be used in the pump-around loop  40  to raise the temperature of the recycle stream  45 . 
         [0068]    Although the preceding description has been described herein with reference to particular means, materials, and embodiments, it is not intended to be limited to the particulars disclosed herein; rather, it extends to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims.