Patent ID: 12215555

When describing the simplified schematic illustrations ofFIGS.1-3, many of the numerous valves, temperature sensors, pressure sensors, electronic controllers, and the like, which may be used and are well known to a person of ordinary skill in the art, may not be depicted. Further, accompanying components that are often included in systems such as those depicted inFIGS.1-3, such as air supplies, heat exchangers, surge tanks, and the like may also not be depicted. However, a person of ordinary skill in the art understands that these components are within the scope of the present disclosure.

Additionally, the arrows in the simplified schematic illustrations ofFIGS.1-3refer to process streams. However, the arrows may equivalently refer to transfer lines, which may transfer process steams between two or more system components. Arrows that connect to one or more system components signify inlets or outlets in the given system components and arrows that connect to only one system component signify a system outlet stream that exits the depicted system or a system inlet stream that enters the depicted system. The arrow direction generally corresponds with the major direction of movement of the process stream or the process stream contained within the physical transfer line signified by the arrow.

The arrows in the simplified schematic illustrations ofFIGS.1-3may also refer to process steps of transporting a process stream from one system component to another system component. For example, an arrow from a first system component pointing to a second system component may signify “passing” a process stream from the first system component to the second system component, which may comprise the process stream “exiting” or being “removed” from the first system component and “introducing” the process stream to the second system component.

Moreover, two or more lines intersecting in the simplified schematic illustrations ofFIGS.1-3may refer to two or more process streams being “mixed” or “combined”. Mixing or combining two or more process streams may comprise mixing or combining by directly introducing both streams into a like reactor, separation device, or other system component. For example, two lines intersecting prior to entering a system component may signify the introduction of the two process streams into the system component, in which mixing or combining occurs.

Reference will now be made in greater detail to various aspects of the present disclosure, some of which are illustrated in the accompanying drawings.

DETAILED DESCRIPTION

The present disclosure is directed to methods for operating candle filter systems for removing solids, such as total dissolved solids, from an MEG rich stream recovered from drilling or pipeline operations. In particular, the present disclosure is directed to methods for operating candle filter systems for removing solids from an MEG rich stream, where the methods enable adaptation of the candle filter systems to accommodate MEG rich streams with high concentrations of Total Dissolved Solids (TDS), such as concentrations of TDS greater than or equal to 100,000 mg/L. Referring now toFIGS.1and3, the methods of the present disclosure for operating a candle filter system130for removing solids from an MEG rich stream116may include passing the MEG rich stream116to the candle filter system130, which may comprise a plurality of candle filter units200operated in parallel and a slurry vessel180disposed downstream of the candle filter system130. The MEG rich stream116comprises at least the MEG and dissolved solids. Each of the plurality of candle filter units200comprises a vessel210, a register230, and a plurality of filter candles232fluidly coupled to the register230. The methods of the present disclosure may further include determining a concentration of total dissolved solids in the MEG rich stream116, determining whether to operate the candle filter system130in a low TDS mode or a high TDS mode based on the concentration of total dissolved solids (TDS) in the MEG rich stream116, filtering the MEG rich stream116in the plurality of candle filter units200to produce a filtrate132and a filter cake deposited on outer surfaces of the filter candles232of the candle filter units200, determining to conduct a cleaning cycle for one or more of the plurality of candle filter units200based on a pressure differential across the plurality of candle filter units200, and conducting a cleaning cycle to remove the filter cake from the outer surfaces of the filter candles232. Conducting the cleaning cycle may comprise reducing a pressure in the one or more candle filter units200; draining a residual volume136of the MEG rich stream116all the way to the slurry vessel180disposed downstream of the candle filter system130; after the draining, pulsing the plurality of filter candles232with a compressed gas242, where the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles232; allowing solids from the solid filter cake to settle in a bottom of the vessel210for a sedimentation duration; and removing the solids from the vessel210. The methods may further include resuming filtering operation of the one or more candle filter units200after the cleaning cycle.

As used in the present disclosure, a “separation unit” refers to any separation device that at least partially separates one or more chemicals in a mixture from one another. For example, a separation unit may selectively separate different chemical species from one another, forming one or more chemical fractions. Examples of separation units include, without limitation, distillation columns, fractionators, flash drums, knock-out drums, knock-out pots, centrifuges, filtration devices, traps, scrubbers, expansion devices, membranes, solvent extraction devices, high-pressure separators, low-pressure separators, and the like. It should be understood that separation processes described in this disclosure may not completely separate all of one chemical constituent from all of another chemical constituent. It should be understood that the separation processes described in this disclosure “at least partially” separate different chemical components from one another, and that even if not explicitly stated, it should be understood that separation may include only partial separation. As used in this disclosure, one or more chemical constituents may be “separated” from a process stream to form a new process stream. Generally, a process stream may enter a separation unit and be divided or separated into two or more process streams of desired composition.

As used in this disclosure, the term “fractionation” may refer to a process of separating one or more constituents of a composition in which the constituents are divided from each other during a phase change based on differences in properties of each of the constituents. As an example, as used in this disclosure, “distillation” refers to separation of constituents of a liquid composition based on differences in the boiling point temperatures of constituents of a composition.

As used in this disclosure, the terms “upstream” and “downstream” may refer to the relative positioning of unit operations with respect to the direction of flow of the process streams. A first unit operation of a system may be considered “upstream” of a second unit operation if process streams flowing through the system encounter the first unit operation before encountering the second unit operation. Likewise, a second unit operation may be considered “downstream” of the first unit operation if the process streams flowing through the system encounter the first unit operation before encountering the second unit operation.

As used in the present disclosure, passing a stream or effluent from one unit “directly” to another unit may refer to passing the stream or effluent from the first unit to the second unit without passing the stream or effluent through an intervening reaction system or separation system that substantially changes the composition of the stream or effluent. Heat transfer devices, such as heat exchangers, preheaters, coolers, condensers, or other heat transfer equipment, and pressure devices, such as pumps, pressure regulators, compressors, or other pressure devices, are not considered to be intervening systems that change the composition of a stream or effluent. Combining two streams or effluents together also is not considered to comprise an intervening system that changes the composition of one or both of the streams or effluents being combined.

As used in the present disclosure, the term “effluent” refers to a stream that is passed out of a reactor, a reaction zone, or a separation unit following a particular reaction or separation. Generally, an effluent has a different composition than the stream that entered the separation unit, reactor, or reaction zone. It should be understood that when an effluent is passed to another system unit, only a portion of that system stream may be passed. For example, a slip stream or bleed stream may carry some of the effluent away, meaning that only a portion of the effluent may enter the downstream system unit. The term “reaction effluent” may more particularly be used to refer to a stream that is passed out of a reactor or reaction zone.

As used in the present disclosure, the term “filter candle” refers to each of the individual cylindrical shaped filter elements contained within a candle filter unit.

It should further be understood that streams may be named for the components of the stream, and the component for which the stream is named may be the major component of the stream (such as comprising from 50 wt. %, from 70 wt. %, from 90 wt. %, from 95 wt. %, from 99 wt. %, from 99.5 wt. %, or from 99.9 wt. % of the contents of the stream to 100 wt. % of the contents of the stream). It should also be understood that components of a stream are disclosed as passing from one system component to another when a stream comprising that component is disclosed as passing from that system component to another. For example, a disclosed “rich MEG stream” passing to a first system component or from a first system component to a second system component should be understood to equivalently disclose “disulfide oil” passing to the first system component or passing from a first system component to a second system component.

As previously discussed, glycols, such as MEG, are used in hydrocarbon drilling and pipeline applications to reduce formation of hydrates, which can block conduits and other equipment. To reduce formation of hydrates, MEG is injected into the pipeline or the wellbore to reduce or prevent the formation of hydrates. Afterwards, the MEG is recovered from the hydrocarbon drilling or pipeline applications. However, recovered MEG streams can include produced water and suspended solids, dissolved solids, or both in addition to the recovered MEG. The recovered MEG stream is further processed in an MEG recovery system to remove the suspended and dissolved solids and concentrate the MEG for reuse back in the drilling or pipeline application.

Referring now toFIG.1, one embodiment of an MEG recovery system100for removing solids from a recovered MEG stream and concentrating the MEG to produce a lean MEG stream is schematically depicted. The MEG recovery system100can include an MEG pretreatment unit110, an MEG recycle pump120, a candle filter system130, and an MEG distillation column140comprising a reflux condenser150and an MEG reboiler. The MEG recovery system100may further include a lean MEG storage tank170. In embodiments, the MEG recovery system100may further include a slurry vessel180and a plate filter system190. The MEG recovery system100may include other unit operations or equipment typically used in the process of recovering MEG from drilling materials and or pipeline materials.

After an initial separation to produce the recovered MEG stream102, the recovered MEG stream102may be introduced to the MEG pretreatment unit110. The MEG pretreatment unit110may be operable to further treat the recovered MEG stream102to remove additional volatile organic compounds (VOC) in a VOC stream112and non-volatile hydrocarbon liquids in a liquid hydrocarbon stream114to produce an MEG rich stream116. The MEG recycle pump120may be disposed downstream of the MEG pretreatment unit110. An inlet of the MEG recycle pump120may be in fluid communication with an outlet of the MEG pretreatment unit110. The MEG recycle pump120may be operable to convey the MEG rich stream116from the MEG pretreatment unit110to the candle filter system130.

The candle filter system130may be disposed downstream of the MEG pretreatment unit110and the MEG recycle pump120. The candle filter system130may be in fluid communication with an outlet of the MEG recycle pump120to receive the MEG rich stream116from the MEG recycle pump120. The candle filter system130is operable to remove dissolved solids from the MEG rich stream116to produce a filtrate132and a solids slurry134. The candle filter system130may comprise one or a plurality of candle filter units and a candle filter control system300. The candle filter system130will be described in further detail in the present disclosure.

Referring again toFIG.1, the MEG recovery system100may further comprise an MEG distillation system140disposed downstream of the candle filter system130. The MEG distillation system140may be in fluid communication with the candle filter system130to receive the filtrate132from the candle filter system130. The MEG distillation system140may be operable to concentrate the MEG in the filtrate132to produce a lean MEG stream162. In particular, the MEG distillation system140may be operable to separate the filtrate132into an aqueous stream154and the lean MEG stream162through distillation, where the boiling point temperature of the water in the filtrate132is less than the boiling point temperature of the MEG in the filtrate132.

The MEG distillation system140may comprise an MEG distillation column142, a reflux condenser150, and an MEG reboiler. The MEG distillation column142may be downstream of the candle filter system130. The MEG distillation column142may be in fluid communication with one or more outlets of the candle filter system130so that the filtrate132can be passed from the candle filter system130to the MEG distillation column142. For instance, the main filtrate outlet, one or more vents, or both may be passed to the MEG distillation column142for concentration of the MEG in the filtrate132. The MEG distillation column142may be operated at a distillation temperature that separates water from MEG to produce the overhead stream144and a distillation bottom stream146, where the overhead stream144may comprise primarily water and the distillation bottom stream146may comprise primarily MEG. In embodiments, the MEG distillation column142may include a water feed148to introduce water to the MEG distillation column142above the inlet of the filtrate132to the MEG distillation column142. In embodiments, the water feed148may be a sour water.

The overhead stream144may comprise primarily water from the filtrate132and, optionally, the water feed148. The overhead stream144may comprise at least 80%, at least 90%, at least 95%, at least 98%, or even at least 99% of the water from the filtrate132. The overhead stream144may be passed to the reflux condenser150, which may be operable to condense constituents of the overhead stream144to produce an aqueous stream154. At least a portion of the aqueous stream154may be refluxed back to the MEG distillation column142. In embodiments, the reflux condenser150may be operable to produce a reflux stream152, which may comprise a greater concentration of MEG compared to the aqueous stream154. The majority of the aqueous stream154may be passed out of the MEG recovery system100, and may be passed to one or more downstream processes for further treatment of the aqueous stream154.

Referring again toFIG.1, the distillation bottom stream146may be passed to the MEG reboiler160. The MEG reboiler160may be operable to heat the distillation bottom stream146and to produce the lean MEG stream162and the MEG return stream164. The MEG return stream164may be passed back to the MEG distillation column142to provide heat to the MEG distillation column142to maintain the temperature at the separation temperature. The lean MEG stream162may be passed to a lean MEG storage tank170disposed downstream of the MEG reboiler160. In embodiments, the MEG recovery system100may include a lean MEG pump166, which may be operable to convey the lean MEG stream162from the MEG reboiler160to the lean MEG storage tank170. The lean MEG from the lean MEG stream162may be stored in the lean MEG storage tank170for reuse in the drilling or pipeline application.

Referring again toFIG.1, the MEG recovery system100may further include a slurry vessel180disposed downstream of the candle filter system130. The slurry vessel180may be in fluid communication with one or more outlets of the candle filter system130to pass the solid slurry134from the candle filter system130to the slurry vessel180. The slurry vessel180may provide temporary storage for the solid slurry134and feeding of the solid slurry to the plate filter system190disposed downstream of the slurry vessel180. The slurry vessel180may be agitated to prevent settling of the solids in the slurry vessel180.

The MEG recovery system100may further include the plate filter system190disposed downstream of the slurry vessel180. The plate filter system190may include one or a plurality of plate filters and may be operable to separate the solid slurry to produce a plate filter filtrate192and a solid filter cake194. The plate filter filtrate192, the solid filter cake194, or both may be passed out of the MEG recovery system100for further treatment.

The candle filter system130will now be described in further detail. As previously discussed, the candle filter system130comprises one or more candle filter units. Referring now toFIG.2, one embodiment of a candle filter unit200is schematically depicted. Each candle filter unit200comprises a vessel210, a register230disposed within the vessel210, and a plurality of filter candles232disposed within the vessel210and fluidly coupled to the register230.

The vessel210may be a pressure vessel capable of withstanding the pressures over the entire operating range of the candle filter unit200. The vessel210may comprise a vessel wall212that defines an internal volume214of the vessel210. The vessel210includes an MEG stream inlet220, a filtrate outlet220, a solids outlet224, and a residual volume outlet226. The MEG stream inlet220may be fluidly coupled to the MEG rich stream116to pass the MEG rich stream116to the candle filter unit200. The MEG stream inlet220may include an MEG inlet control valve310operable to control a flow rate of the MEG rich stream116through the MEG stream inlet220into the vessel210.

The filtrate outlet222may be disposed in a side of the vessel210and may be fluidly coupled to the register230. In embodiments, the register230may comprise a plurality of register pipes234traversing the internal volume214of the vessel210, and the vessel210may comprise a plurality of filtrate outlets222, wherein each of the filtrate outlets222is fluidly coupled to one of the register pipes234. The filtrate outlets222may be operable to pass the filtrate132out of the candle filter unit200. The filtrate outlets222may each include a filtrate control valve312, which may be operable to control a flow rate of the filtrate132out of the vessel210through the filtrate outlet222. Referring toFIGS.1and2, the filtrate outlets222may be in fluid communication with the MEG distillation system140to pass the filtrate132from the candle filter unit200of the candle filter system130to the MEG distillation system140.

Referring again toFIG.2, the solids outlet224may be disposed in the bottom of the vessel210. The solids outlet224may be sized to remove a solids slurry comprising pieces of solid filter cake from the vessel210after dislodging the solid filter cake from the outer surfaces of the filter candles232during the cleaning cycle of the candle filter unit200. The solids outlet224may include a solids outlet valve250that may be actuated during a cleaning cycle to remove the solid slurry from the vessel210during the cleaning cycle. The solids outlet224may be operable to pass the solid slurry out of the vessel210. In embodiments, the solid filter cake pieces may be removed from the vessel210as the solids and not as a slurry. In embodiments, the candle filter system130may include a solids blower260fluidly coupled to the solids outlet valve250. The solids blower260may be operable to convey solids from the solids outlet224to the slurry vessel180during the cleaning cycle.

The residual volume outlet226may be disposed in a bottom portion of the vessel210. The residual volume outlet226may be operable to remove a residual volume136of the MEG rich stream from the internal volume214of the vessel210at the start of the cleaning cycle. The residual volume136of the MEG rich stream may comprise the unfiltered MEG rich stream116remaining in the internal volume214of the vessel210prior to the start of the cleaning cycle. The residual volume outlet226may comprise a residual volume control valve316, which may be operable to control the flow of the residual volume136of the MEG rich stream through the residual volume outlet226out of the vessel210.

Referring again toFIG.2, the vessel210may further comprise a compressed gas inlet240, which may be fluidly coupled to a compressed gas source (not shown) to pass a compressed gas242into the internal volume of the vessel210. The compressed gas may be compressed air or a compressed inert gas, such as but not limited to nitrogen, argon, or other inert gas. The compressed gas inlet240may comprise a gas inlet control valve320, which may be operable to control the flow of the compressed gas242into the vessel210, such as during a cleaning cycle. The vessel210may further include a gas outlet244, which may be operable to pass vent gases out of the vessel210. The gas outlet244may include a vent control valve322, which may be operable to control the flow of vent gases246through the gas outlet244and out of the vessel210. In embodiments, the vent gases246may include entrained particulates and may be passed from the candle filter unit200to the plate filter system190for removal of the entrained solids from the vent gas.246.

Referring again toFIG.2, the register230may comprise one or a plurality of register pipes234extending horizontally across the internal volume214of the vessel210, such as extending in the X-Y plane of the coordinate axis ofFIG.2across the internal volume214of the vessel210. Each of the register pipes234may be fluidly coupled to one of the filtrate outlets222. The end of each register pipe234opposite the filtrate outlet222may be a closed end so that filtrate from the filter candles232flows through the register pipes234towards the filtrate outlets222. Each of the register pipes234may have one or a plurality of inlets235, where each of the inlets235is fluidly coupled to one of the filter candles232.

The candle filter unit200further includes a plurality of the filter candles232disposed in the vessel210and fluidly coupled to the register230, such as to one of the register pipes234. Each of the filter candles232may be fluidly coupled to an inlet235of one of the register pipes234by a conduit236. Each filter candle232may comprises a central pipe, which is fluidly coupled to the register pipe234by the conduit236. The filter candle232further comprises a support grid disposed around the central pipe. The support grid may be a perforated cylindrical grid surrounding the central pipe. The support grid may define a filtrate collection chamber between the support grid and the central pipe. The perforations in the support grid may provide for a high flow rate of filtrate through the support grid. The filter candle further includes a filter medium disposed on a radially outer surface of the support grid. The filter medium may be a filter cloth, filter screen, or other structure capable of allowing liquid filtrate to pass through the filter medium while preventing solid particles from passing through.

Referring toFIG.3, in embodiments, the candle filter system130may comprise a plurality of candle filter units200arranged in parallel. In embodiments, the candle filter system130may have 2, 3, 4, 5, 6, or more than 6 candle filter units200. In embodiments, the candle filter system130may comprise 3 candle filter units200operated in parallel.

Referring again toFIG.2, during operation of the candle filter unit200in a filtering mode, the MEG rich stream116is passed into the vessel of the candle filter unit200through the MEG stream inlet220. The MEG rich stream116is introduced at a pressure sufficient to produce a pressure differential across the filter candles232. The pressure differential across the candle filter unit200refers to the difference between the pressure of fluids on the inlet side of the filter candles232and the pressure of fluids on the outlet side of the filter candles232, such as but not limited to the difference between the pressure of the MEG rich stream116and the pressure of the filtrate132passed out of the filtrate outlet222. The pressure differential across the filter candles232causes liquids, which comprise the MEG, to pass radially through the filter medium of the filter candle232into the filtrate collection chamber of the filter candle232. The filter medium prevents solids from passing through, instead capturing the solids on the radially outer surface of the filter medium. Then, the filtrate flows downward, such as in the −Z direction of the axis inFIG.2, of the filtrate collection chamber to an inlet of the central pipe of the filter candle232. The filtrate then flows back up through the central pipe to the register and out of the candle filter unit200through the filtrate outlet222. The filtrate132passed out of the candle filter unit200may be free of solids, such as total dissolved solids. In embodiments, the filtrate132may include less than or equal to 80,000 parts per million by weight total dissolved solids.

As the candle filter unit200operates, a filter cake comprising the filtered solids builds up on the outer surface of the filter medium of the filter candles232. As the filter cake builds up, the pressure differential across the candle filter unit200increases. When the pressure differential across the candle filter increases to a threshold differential pressure, such as a differential pressure of greater than or equal to 480 kilopascals (kPa) (about 70 pounds per square inch (psi)), greater than or equal to 520 kPa (about 75 psi), greater than or equal to 530 kPa (about 77 psi), or even greater than or equal to 550 kPa (about 80 psi), the filtration efficiency of the candle filter system decreases dramatically. At this point, the candle filter unit200may be transitioned to a cleaning mode to undergo a cleaning cycle to remove the filter cake from the outer surfaces of the filter medium.

Referring now toFIG.4, during a conventional cleaning cycle400for the candle filter unit, after filtration402, the candle filter unit is transitioned to a cleaning mode410. In the cleaning mode410, the candle filter unit is pulsed with a compressed gas (step412), which dislodges the solid filter cake from the outer surfaces of the filter candles. The compressed gas pulsation may also break apart the solid filter cake into smaller pieces. In some instances, prior to pulsing with compressed gas, the residual volume of the candle filter is drained at least until the filter candles are exposed and no longer submerged within the liquid. Following compressed gas pulsation412, the cleaning cycle can include a sedimentation step414. In the sedimentation step414, the pieces of the solid filter cake dislodged from the filter candles are allowed to settle in the bottom of the vessel of the candle filter unit. After the sedimentation step414, the filter cake solids settled at the bottom of the vessel are removed from the vessel in the cake transfer step416. The solid filter cake may be removed from the vessel either through the solids outlet224(FIG.2) or through the residual volume outlet226(FIG.2). Referring again toFIG.4, following the cake transfer step416, the candle filter unit may be transitioned back to filtration mode to resume filtering the suspended solids from the MEG rich stream. Transitioning back to the filtration mode402may include filling the vessel back up with the MEG rich stream and increasing the pressure of the MEG rich stream until the filtrate passes through the filter candles into the register and the filtrate outlet.

Referring now toFIG.3, during normal operation of a candle filter system130having a plurality of candle filter units200A,200B,200C, the candle filter system130may be operated in swing mode, where at least one of the candle filter units is maintained in a standby mode while the other candle filter units are operated in filtration mode. For instance, during conventional operation, one or more of the candle filter units, such as first candle filter unit200A and second candle filter200B may be operated in the filtration mode, while at least one candle filter unit, such as candle filter unit200C is maintained in the standby mode. In the standby mode, the candle filter unit is isolated so that no flow of the MEG rich stream116is introduced to the candle filter unit, and the candle filter unit is idle and is not filtering and is not in a cleaning mode. When the first candle filter unit200A (or the second candle filter unit200B) reaches a high differential pressure, which indicates the need for a cleaning cycle, the first candle filter unit200A may be transitioned to the cleaning mode. Upon transitioning the first candle filter unit200A to the cleaning mode, the third candle filter unit200C may be transitioned from the standby mode to the filtration mode to begin filtering the MEG rich stream116, while the first candle filter unit200A undergoes the cleaning cycle. Once the cleaning cycle for the first candle filter unit200A is complete, the first candle filter unit200A may be transitioned to the standby mode. Then, the second candle filter unit200B may reach a high differential pressure indicating a need for a cleaning cycle. At this point, the second candle filter unit200B may be transitioned to the cleaning mode while the first candle filter unit200A is transitioned from standby mode to filtration mode. Once the cleaning cycle for the second candle filter unit200B is complete, the second candle filter unit200B is transitioned to standby. Then, the third candle filter unit200C reaches a high differential pressure indicating the need for a cleaning cycle. The third candle filter unit200C is transitioned to the cleaning mode, while the second candle filter unit200B is transitioned from standby to filtration mode. After the cleaning cycle for the third candle filter unit200C is complete, the third candle filter unit200C is transitioned to the standby mode. The process is repeated to maintain continuous operation of the candle filter system130.

Conventional operation of the candle filter system130provides for continuous operation of the candle filter system130during normal operating conditions, such as during periods when the total dissolved solids (TDS) of the MEG rich stream116is within normal limits. However, when the TDS level of the MEG rich stream116is high, such as a concentration of TDS of greater than or equal to 100,000 mg/L, the filter candles in the candle filter units get blocked quickly, such as in less than one hour. Operating in swing mode according to conventional operating procedures, such as with only two of three candle filter units200in filtration mode and the third in standby mode, results in the candle filter system130becoming quickly overwhelmed with all of the multiple candle filter units200transitioned into the cleaning mode. For instance, with each filter candle unit200getting blocked in less than an hour, the candle filter system130with three candle filter units200typically runs for less than 4 hours under a high TDS condition (≥100,000 mg/L TDS) before all the candle filter units200are transitioned to cleaning mode. Further, the transient high pressure differential spike, which can result from high TDS concentrations in the MEG rich stream116, can cause frequent failure of the candle filter units200to start in the filtration mode.

Further, the conventional cleaning cycles are not efficient, which can result in excess residual salts remaining on the filter candles232after the cleaning cycle. Further, prefilling the vessel210of the candle filter units200takes a long time, such as greater than 30 minutes, which adds to the cleaning cycle time. Switching between candle filter units200during swing mode requires operator intervention and interrupts the flow of MEG through the system. For at least these reasons and more, conventional operating methods for operating candle filter systems130for removing solids from the MEG rich stream116are not able to handle abnormal operating conditions, such as MEG rich streams116with high concentrations of TDS of greater than or equal to 100,000 mg/L TDS.

Thus, there is an ongoing need for operating methods for candle filter system130to improve cleaning efficiency and increase the filtration time of the candle filter system130during abnormal operating conditions, such as when filtering an MEG rich stream116with a high concentration of TDS of greater than or equal to 100,000 mg/L. Referring again toFIG.3, the methods of operating a candle filter system130of the present disclosure may include determining when a high TDS operating condition exists and switching operation of the candle filter system130to a high TDS operating mode. In the high TDS operating mode, all of the plurality of candle filter units200are operated in the filtration mode in parallel so that the total flow rate of the MEG rich stream116is distributed through all of the candle filter units200instead of having one of the candle filter units200in a standby mode. This reduces the flow rate through each of the individual candle filter units200while maintaining the production rate of the candle filter system130as a whole. Further, reducing the flow rate in each of the candle filter units200may reduce the rate at which the solids build up on the outer surfaces of the filter candles232, which may increase the total filtration time that each of the individual candle filter units200are in the filtration mode during a high TDS operating condition.

The methods disclosed herein further include changes to the cleaning cycle to improve the efficiency of the cleaning cycles, which in turn increases the total filtration time of each of the candle filter units200during a high TDS operating condition. In particular, the methods of the present disclosure may include the additional step of draining the residual volume136of MEG rich stream all the way to the slurry vessel180before pulsing the candle filter unit200with the compressed gas. The methods of the present disclosure further include modifications to the compressed gas pulsing to improve breakup and removal of the filter cake solids from the outer surface of the filter candles232and increasing the sedimentation duration to improve removal of the solids from the vessel210. The methods of the present disclosure may further include repeating the cleaning cycle in response to the candle filter system130determining that a high pressure differential across the filter candles232still exists. To improve the transition from cleaning mode back to filtration mode, the methods of the present disclosure may further include overriding or bypassing a high pressure differential shutdown sequence, which may allow startup of the candle filter units200despite transient spike in pressure differential across the candle filter units200.

Referring now toFIG.3, the candle filter system130may comprise a plurality of candle filter units200A,200B,200C, which are operated in parallel. Each of the candle filter units200A,200B,200C may have any of the components and features previously described in the present disclosure for the candle filter unit200ofFIG.2. Each of the candle filter units200A,200B,200C may include a plurality of control valves and a pressure differential system. The candle filter system130may further include a slurry vessel180disposed downstream of the candle filter system130. The slurry vessel180may be operable to receive the solid slurry134, or the residual volume136of the MEG rich stream in the vessel210, or both. The candle filter system130may further include the control system300operable to control operation of the candle filter system130.

The candle filter system130may include a plurality of control valves for each of the candle filter units200. The control valves can include, but are not limited to the MEG inlet control valve310, the filtrate control valve312, solids outlet valve250, residual volume control valve316, gas inlet control valve320, and the vent control valve322for each of the candle filter units200. Each of these control valves can be any type of control valve suitable for the stream in which it is disposed. Each of the control valves may include a valve body placed in a fluid flow, a flow restrictor disposed within the valve body, and an actuator operable to change a position of the flow restrictor to change the flow rate through the control valve. In embodiments, the actuator of the control valve may be operable to transition the flow restrictor between an open position and a closed position. In embodiments, the actuator of the control valve may be operable to change a position of the flow restrictor at one or more positions between fully open and closed to change a flow rate of materials through the control valve. As used in the present disclosure, the term “closed” when used in relation to a valve, refers to the fully closed position that prevents fluid from passing through the valve. It is understood that any reference to changing a position or condition of a control valve refers to operating the actuator to change the position of the flow restrictor of that control valve. The control valves may be communicatively coupled to the control system300, such as by having the actuator communicatively coupled to the control system300through wired or wireless communication channels.

Referring again toFIG.3, each candle filter unit200A,200B,200C may comprise the MEG inlet control valve310, which may be disposed at the MEG stream inlet220. The MEG inlet control valve310may be operable to control a flow rate of the MEG rich stream116through the MEG stream inlet220into the vessel210. The actuator of the MEG inlet control valve310may be operable to change the position of the flow restrictor of the MEG inlet control valve310to a fully open position, a closed position, and a plurality of positions between closed and fully open. The MEG inlet control valve310may be operable to stop the flow of the MEG rich stream116to the vessel210, such as prior to a cleaning cycle, or may adjust the flow rate of the MEG rich stream116to the vessel210, such as by changing the feed flow rate when switching between a low TDS mode and a high TDS mode of operation.

Each of the filtrate outlets222may include a filtrate control valve312, which may be operable to control a flow rate of the filtrate132out of the vessel210through each of the filtrate outlets222. The actuator of the filtrate control valve312may be operable to change the position of the flow restrictor of the filtrate control valve312to a fully open position, a closed position, and a plurality of positions between closed and fully open. In embodiments, the filtrate control valve312may be actuated between a fully open position during filtration and a closed position during a cleaning cycle, which may prevent back flow of the filtrate132into the vessel210during the cleaning cycle.

Each of the candle filter units200A,200B,200C may include a solids outlet valve250disposed at the solids outlet224. The solids outlet valve250may include the solids valve actuator314operatively coupled to the solids outlet valve250. The solids valve actuator314may be operable to transition the solids outlet valve250between the closed position and a fully open position. The solids outlet valve250may be actuated during a cleaning cycle to remove the solid slurry from the vessel210after the sedimentation step of the cleaning cycle. The solids outlet224may be operable to pass the solid slurry out of the vessel210. The solids outlet valve250is transitioned to the closed position after the solids removal step so that the candle filter unit can be transitioned back to filtering operation. The solids outlet valve250may be maintained in the closed position during filtering.

Each of the candle filter units200A,200B,200C may include a residual volume control valve316disposed downstream of the residual volume outlet226. The residual volume control valve316may be operable to control the flow of the residual MEG rich stream136through the residual volume outlet226out of the vessel210. The actuator of the residual volume control valve316may be operable to transition the flow restrictor of the residual volume control valve316between a fully open position and a closed position. In embodiments, the residual volume control valve316of one or more of the candle filter units may be actuated to the fully open position during the step of draining the residual volume136of the MEG from the vessel210at the beginning of a cleaning cycle. The residual volume control valve316may be actuated to transition to the closed position after draining the residual volume136from the vessel210. The residual volume control valve316may be maintained in the closed position during filtering.

Each of the candle filter units200A,200B,200C may include a gas inlet control valve320disposed upstream of the compressed gas inlet240of the vessel210. The gas inlet control valve may be operable to control the flow of the compressed gas242into the vessel210, such as during a cleaning cycle. The actuator of the gas inlet control valve320may operable to transition the flow restrictor of the gas inlet control valve320between a fully open position and a closed position. The gas inlet control valve320may be in the closed position during filtering. In embodiments, during the pulsation step of the cleaning cycle, the gas inlet control valve320may be cycled back-and-forth between the fully open position and the closed position to produce pulses of the compressed gas into the vessel210during the pulsation step of the cleaning cycle.

Each of the candle filter units200A,200B,200C may include the vent control valve322disposed downstream of the gas outlet244of the vessel210. The vent control valve322may be operable to control the flow of vent gases246through the gas outlet244and out of the vessel210. The actuator of the vent control valve322may operable to transition the flow restrictor of the vent control valve322between a fully open position and a closed position. The vent control valve322may be in the closed position during filtering. In embodiments, during the pulsation step of the cleaning cycle, the vent control valve322may be transitioned to the fully open position to allow gases to escape the vessel210during the pulsation step of the cleaning cycle.

Referring again toFIG.3, each of the candle filter units200A,200B,200C may include at least an inlet pressure sensor330and an outlet pressure sensor332. In embodiments, each of the candle filter units may include a pressure differential indicator (PDI)334communicatively coupled to the inlet pressure sensor330or the outlet pressure sensor332. The inlet pressure sensor330may be disposed on the inlet side of the filter candles232, such as in fluid communication with the vessel210on the inlet side of the filter candles232, in fluid communication with the MEG stream inlet220, or upstream of the MEG stream inlet220. The inlet pressure sensor330may be operable to measure a relative fluid pressure on the inlet side of the filter candles232of the candle filter unit200A,200B,200C, such as the pressure of the MEG rich stream116in the vessel210of the candle filter unit.

The outlet pressure sensor332may be disposed on the outlet side of the filter candles232. In embodiments, the outlet pressure sensor332may be in fluid communication with the register230, with one or more of the filtrate outlets222, with the piping downstream of the filtrate outlets222, or combinations thereof. The outlet pressure sensor332may be operable to measure a relative fluid pressure on outlet side of the filter candles232of the candle filter unit200A,200B,200C, such as the relative pressure of the filtrate132in the register230or passing through the filtrate outlets222. The inlet pressure sensor330, the outlet pressure sensor332, or both may be any pressure sensor suitable for measuring the pressure of fluids in the candle filter units.

Referring again toFIG.3, in embodiments, the inlet pressure sensor330, the outlet pressure sensor332, or both may be communicatively coupled to a pressure differential indicator334(PDI334). The PDI334may be operable to receive an inlet pressure indication from the inlet pressure sensor330and an outlet pressure indication from the outlet pressure sensor332. The PDI334may be operable to compare the inlet pressure indication and the outlet pressure indication and calculate a pressure differential across the candle filter unit from the inlet pressure indication and the outlet pressure indication. In embodiments, the PDI334may display the pressure differential on a display, which may be an analog display (differential pressure gauge) or a digital display. In embodiments, the inlet pressure sensor330and the outlet pressure sensor332may be directly communicatively coupled to the control system300, where the control system300may function as the PDI334by comparing the inlet pressure indication and the outlet pressure indication and producing a PDI signal, which may be indicative of the pressure differential across the candle filter units200A,200B,200C. In embodiments, the PDI signal indicative of the pressure differential may be used as a variable to control the candle filter system130. Alternatively or additionally, in embodiments, the PDI signal may be output to a display device for display of the differential pressure to the operator of the candle filter system130.

Referring again toFIG.1, in embodiments, the MEG recovery system100may include one or more downstream sensors350for measuring one or more system parameters downstream of the candle filter system130, such as one or more operating parameters of the MEG distillation system140, the MEG reboiler160, the lean MEG pump166, the lean MEG storage tank170, the slurry vessel180, the plate filter system190, or combinations of these. In embodiments, the downstream sensors350may include one or more of level sensors in the MEG reboiler160, both bundle side and lean MEG side; run sensors on the lean MEG pumps166, which indicate whether the lean MEG pumps are running and lean MEG is flowing; level sensors in the lean MEG storage tank170; level sensors in the slurry vessel180; other sensors; or combinations of these. The downstream sensors350may be operable to identify downstream operating conditions influencing whether to operate or shut down the candle filter system130.

Referring again toFIGS.1-3, the candle filter system130may further include a control system300. The control system300may include one or a plurality of processors302, one or a plurality of memory modules304communicatively coupled to the processors302, and computer readable and executable instructions stored in the memory modules304. The control system300may be communicatively coupled to the MEG inlet control valve310, the filtrate control valve312, the solids valve actuator314, the residual volume discharge control valve316, the gas inlet control valve320, the vent control valve322, the MEG recycle pump120, or combinations of these. The control system300may be configured to control operation or actuation of one or more of the MEG inlet control valve310, the filtrate control valve312, the solids valve actuator314, the residual volume discharge control valve316, the gas inlet control valve320, the vent control valve322, the MEG recycle pump120, or combinations of these during operation of the candle filter system130in the filtering mode, the cleaning cycle, or during transitions between cleaning cycles and the filtering mode.

The control system300may be communicatively coupled to one or more measuring devices, such as but not limited to one or more of the inlet pressure sensor330, the filtrate outlet pressure sensor332, the differential pressure indicator334, one or more of the downstream sensors350, or combinations of these. The control system300may be configured to receive signals from one or more of the inlet pressure sensor330, the filtrate outlet pressure sensor332, the differential pressure indicator334, one or more of the downstream sensors350, or combinations of these measuring devices sensors. The control system300may be configured to process the signals from the measuring devices and control operation of the candle filter system130based on the processing of the signals from the measuring devices.

The machine readable and executable instructions306may be stored on the memory modules304and may be executed by the processors302to cause the control system300to control the candle filter system130according to any of the methods described in the present disclosure. In other words, any of the methods disclosed in the present disclosure may be embodied in the machine readable and executable instructions306.

Referring again toFIGS.1-3, the control system300may further include a display360communicatively coupled to the processors302. The display360may include a user interface362displayed on the display360. In embodiments, the display360may be a touch screen operable to display the user interface362and also accept operator input through contact with the display. In embodiments, the control system300may include one or more user input devices (not shown) separate from the display and operable to enable the operator to make control selections through the user interface362. Separate user input devices may include but are not limited to one or more of a keyboard, mouse, microphone, push button, toggle switches, or other type of user input device.

Referring now toFIG.3, the methods of the present disclosure for operating the candle filter130for removing solids from MEG recovered from drilling fluids will now be described. The methods of the present disclosure for operating the candle filter system130may include passing the MEG rich stream116to the candle filter system130. The candle filter system130may include a plurality of the candle filter units200A,200B,200C, which may be operated in parallel, and the slurry vessel180disposed downstream of the candle filter units. The candle filter system130may have any of the components or features previously discussed herein for the candle filter system130. The MEG rich stream116may comprise at least the MEG and dissolved solids. Each of the plurality of candle filter units200A,200B,200C may comprise the vessel210, the register230, and the plurality of filter candles232fluidly coupled to the register230. The candle filter units200A,200B,200C may have any of the components or features previously described in the present disclosure in relation to the candle filter unit200. The methods of the present disclosure may further include determining the concentration of total dissolved solids in the MEG rich stream116, determining whether to operate the candle filter system130in a low TDS mode or a high TDS mode based on the concentration of total dissolved solids (TDS) in the MEG rich stream116, and filtering the MEG rich stream116in one or more of the candle filter units200A,200B,200C to produce the filtrate132and a filter cake deposited on outer surfaces of the filter candles232. The methods may further include determining to conduct a cleaning cycle for one or more of the candle filter units200A,200B,200C based on the pressure differential across the candle filter units and conducting a cleaning cycle to remove the filter cake from the outer surfaces of the filter candles232.

Conducting the cleaning cycle for one or more of the candle filter units200A,200B,200C may include reducing the pressure in the candle filter unit; draining the residual volume136of the MEG rich stream all the way to the slurry vessel180disposed downstream of the candle filter system130; after draining to the slurry vessel180, pulsing the filter candles232with the compressed gas242, wherein the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles232; allowing solids from the solid filter cake to settle in a bottom of the vessel210for a sedimentation duration; and removing the solids134from the vessel210. Following the cleaning cycle, the methods may include resuming filtering operation of the one or more candle filter units200A,200B,200C.

Referring toFIG.5, a flow chart of the methods510for cleaning the candle filter units is graphically depicted. As shown inFIG.5, after filtration502, the methods510for cleaning the solids from the candle filter units may include the draining step512, during which the pressure in the candle filter unit is reduced and the residual volume of material is drained back to the slurry vessel. Following draining, the method510may include gas pulsation514, during which the compressed gas is pulsed repeated into the vessel of the candle filter unit to dislodge the solid filter cake from the outer surface of the filter candles. The gas pulsation514may be followed by a sedimentation step516, during which the solids from the dislodged filter cake are allowed to settle in the bottom of the vessel. Once the solid filter cake is settled in the bottom at the conclusion of the sedimentation step516, the methods510include a cake transfer step518, during which the solids from the dislodged filter cake are transferred to the slurry vessel. Following removal of the solids during cake transfer518, the differential pressure across the candle filter unit may be measured. If the differential pressure is too high, then one or more subsequent cleaning cycles can be performed, where each subsequent cleaning cycle may comprise the steps of gas pulsation514, sedimentation516, and cake transfer518. If the differential pressure across the candle filter unit is low, then the candle filter unit can be transitioned back to filtration mode for filtration502of the MEG rich stream.

Referring again toFIG.3, determining the concentration of total dissolved solids (TDS) in the MEG rich stream116may include measuring the concentration of the TDS in the MEG rich stream116upstream of the candle filter system130, at the MEG stream inlet220, or in the vessels210of the candle filter units200A,200B,200C. The concentration of TDS of the MEG rich stream116may be measured using one or more instruments suitable for the purpose. The TDS instrument may be operable to produce a TDS signal indicative of the concentration of the TDS of the MEG rich stream116and transmit the TDS signal to the control system130. In embodiments, determining the concentration of TDS in the MEG rich stream116may comprise measuring the pressure differential across one or more of the candle filter units200A,200B,200C and determining a relative concentration of TDS in the MEG rich stream116based on the measurement of the pressure differential. In embodiments, the concentration of TDS may be determined from measuring the change in pressure differential with time for one or more of the candle filter units. Other methods of determining the concentration of TDS or relative concentration of TDS in the MEG rich stream116may be employed.

As previously discussed, based on the concentration of TDS (or relative concentration of TDS) in the MEG rich stream116, the candle filter system130may be operated in a low TDS mode or a high TDS mode. Determining whether to operate the candle filter system130in the low TDS mode or the high TDS mode may comprise determining when the concentration of TDS in the MEG rich stream116is less than a threshold concentration and operating the candle filter system130in the low TDS mode, and determining when the concentration of TDS in the MEG rich stream116is greater than or equal to the threshold concentration and operating the candle filter system130in the high TDS mode. In embodiments, the threshold concentration of TDS in the MEG rich stream116may be 100,000 parts per million by weight (ppmw, wherein 1 ppmw≈1 mg/L). In embodiments, when the concentration of TDS in the MEG rich stream116is less than 100,000 ppmw, the candle filter system130may be operated in the low TDS mode, and when the concentration of TDS in the MEG rich stream is greater than or equal to 100,000 ppmw, the candle filter system130may be operated in the high TDS mode.

In embodiments, operating the candle filter system130in the low TDS mode may comprise operating the candle filter system130in a swing mode in which at least a first candle filter unit is operating in a filtering mode, and a second candle filter unit is in a standby mode. The standby mode refers to a mode of operation where the candle filter unit is idle and is not actively filtering the MEG rich stream and is not undergoing a cleaning cycle. When the at least one first candle filter in filtering mode reaches a high pressure differential condition, the at least one first candle filter unit may be transitioned to cleaning mode while the second candle filter unit is transitioned to filtering mode. A cleaning cycle may be conducted on the first candle filter unit. Following conducting the cleaning cycle on the first candle filter unit, the first candle filter unit may be transitioned to the standby mode until the second candle filter unit reaches a high pressure differential condition. Then, the second candle filter unit may be transitioned to the cleaning mode, and the first candle filter unit may be transitioned to filtering mode, and so forth.

Referring again toFIG.3, in the low TDS mode, the candle filter system130may run with candle filter unit200A and candle filter unit200B in filtering mode, with candle filter unit200C in standby (not filtering or cleaning). When candle filter unit200A reaches a high differential pressure indicating that a cleaning cycle is needed, the candle filter unit200A may be transitioned to cleaning mode, and candle filter unit200C may be transitioned to filtering mode. A cleaning cycle is conducted for candle filter unit200A. When the cleaning cycle is completed, candle filter unit100A may be transitioned to standby mode, with candle filter unit200B and candle filter unit200C in filtering mode. When either of candle filter units200B or200C reach the high differential pressure condition, it would be transitioned to the cleaning mode while candle filter unit200A is transitioned to the filtering mode. The switching between standby mode, cleaning mode, and filtering mode may continue in this manner during operating the candle filter system130in the low TDS mode of operation. In the low TDS mode, the candle filter units operating in filtration mode are operated at 100% of the flow rate capacity of the candle filter unit, and the candle filter unit in standby is idle and filtering at 0% of the flow rate capacity.

Referring again toFIG.3, when the concentration of TDS in the MEG rich stream116is greater than or equal to the threshold concentration of TDS in the MEG rich stream116, such as greater than or equal to 100,000 ppmw, the candle filter system130may be transitioned to and operated in the high TDS mode. In the high TDS mode, each of the plurality of candle filter units200A,200B,200C may be operated in the filtration mode, and none of the candle filter units200A,200B,200C is in standby mode. In the high TDS mode, since all of the candle filter units200A,200B, and200C are in filtration mode at the same time, each of the candle filter units200A,200B,200C may be operated at designed flow rate that is 100% of the full flow rate capacity of each candle filter unit while others are on standby mode or regen cycle. In embodiments, each of the candle filter units200A,200B,200C may be operated simultaneously at 100% of the full flow rate capacity during operation of the candle filter system130in the high TDS mode.

Operating each of the candle filter units200A,200B,200C in the filtration mode at less than full flow rate capacity may reduce the rate at which the solid filter cake builds up on the outer surface of the filter candles232in any one candle filter unit200A,200B,200C, thereby reducing the rate at which the pressure differential increases. In high TDS mode, decreasing the rate at which the solid filter cake builds up on the filter candles232in the candle filter units200A,200B,200C may increase the run time of the candle filter system130before any of the candle filter units200A,200B,200C reach a differential pressure indicating the need for a cleaning cycle. Thus, in high TDS mode, the candle filter system130may be better able to maintain production rate of the filtrate132passed downstream to the MEG distillation system140(FIG.1). In high TDS mode, once one or more of the candle filter units200A,200B,200C reaches a high differential pressure indicative of a need to undergo a cleaning cycle, the candle filter unit200A.200B,200C may be transitioned from the filtering mode to the cleaning mode, and a cleaning cycle may be conducted to remove the solid filter cake from the outer surfaces of the filter candles232.

Referring again toFIG.3, as previously discussed, the methods of operating the candle filter system130of the present disclosure may include determining to conduct a cleaning cycle for one or more of the plurality of candle filter units200A,200B,200C. Determining to conduct a cleaning cycle for one or more of the plurality of candle filter units may include measuring the pressure differential across each one of the plurality of candle filter units200A,200B,200C and determining to conduct the cleaning cycle when the pressure differential across one or more of candle filter units200A,200B,200C is greater than or equal to a cleaning threshold pressure differential. The cleaning threshold pressure differential may be 480 kilopascals (kPa, or about 70 pounds per square inch (psi)), 530 kPa (about 77 psi), or even 550 kPa (about 80 psi). In embodiments, the methods may include determining to conduct the cleaning cycle when the pressure differential across one or more of candle filter units200A,200B,200C is greater than or equal to 480 kPa, greater than or equal to 530 kPa, or even greater than or equal to 550 kPa. As previously discussed, the pressure differential may be determined by measuring the inlet pressure with the inlet pressure sensor330, measuring the outlet pressure with the outlet pressure sensor332, and comparing the outlet pressure and the inlet pressure to determine the pressure differential. The pressure differential may be the absolute value of the difference between the inlet pressure and the outlet pressure. Comparing the outlet pressure and inlet pressure to determine the pressure differential may be performed by the pressure differential indicator334(as inFIG.3) or by the control system300(as inFIG.2).

In embodiments, determining to conduct a cleaning cycle may comprise measuring the pressure differential across the entire candle filter system130, and when the pressure differential across the entire candle filter system130is greater than or equal to the cleaning threshold pressure differential, conducting a cleaning cycle for one or all of the candle filter units200A,200B,200C. Referring toFIG.1, determining the pressure differential across the entire candle filter system130may include measuring a pressure of the MEG rich stream116immediately upstream of the candle filter system130, such as between the MEG recycle pump120and the candle filter system130, and measuring a pressure of the filtrate132passed from the candle filter system130to the MEG distillation system140, and comparing the pressure of the MEG rich stream116to the pressure of the filtrate132. In embodiments, such as when operating the candle filter system130in high TDS mode, all of the candle filter units200A,200B,200C may be transitioned to the cleaning mode and subjected to a cleaning cycle at the same time. In embodiments, one or a subset of the candle filter units200A,200B,200C may be transitioned to the cleaning mode and subjected to the cleaning cycle while the remaining candle filter units are maintained in filtering mode.

As previously discussed, the methods for conducting the cleaning cycle may include draining the residual volume136of the MEG rich stream from the vessel210of the candle filter unit200A,200B,200C all the way to forward to the slurry vessel180. Draining the residual volume136all the way to the slurry vessel180may reduce or prevent reintroduction of solids back into the vessel210when transitioning from the candle filter unit200from the cleaning cycle back to filtration mode. Draining the residual volume136all the way to the slurry vessel180may cause separation of the drained MEG from the filtered solids at the slurry vessel180. The residual volume136may be drained from the vessel210by closing the MEG inlet control valve310and opening the residual volume discharge control valve316. In embodiments, the pressure may be relieved from the vessel210after closing the MEG inlet control valve310and opening the residual volume discharge control valve316. In embodiments, the residual volume136may be conveyed to the slurry vessel180by means of one or more pumps (not shown).

Referring again toFIG.5, after draining512the residual volume back to the slurry vessel, the cleaning cycle includes the gas pulsation step514. During the gas pulsation step514, the filter candles are pulsed with a compressed gas to dislodge the solid filter cake from the outer surfaces of the filter candles. Referring now toFIG.3, pulsing the plurality of filter candles232with the compressed gas242may include introducing the compressed gas242to the internal volume of the vessel210in a plurality of bursts spaced apart over a total gas pulsation duration. In other words, during pulsation, the compressed gas242is turned on for a pulse duration and then turned off for an idle period. After a short time, the compressed gas242is turned on for a subsequent duration, then then turned off again for a subsequent idle period. The pulsing is continued until the end of the total gas pulsation duration.

The compressed gas242may be air, nitrogen, a noble gas such as argon, or other inert gas that does not chemically interact to any significant degree with the MEG or the constituents of the solid filter cake. In embodiments, the compressed gas may be nitrogen gas. In the methods of the present disclosure, the compressed gas242may be supplied at a greater pressure compared to conventional operation of the candle filter system130. In embodiments, the compressed gas242may be supplied to the candle filter units200A,200B,200C at a pressure of from 200 kPa to 400 kPa absolute pressure, such as from 250 kPa to 400 kPa, from 275 kPa to 400 kPa, or from 300 kPa to 400 kPa absolute pressure. In embodiments, the compressed gas242may be supplied to the candle filter units at a gauge pressure of from 170 kPa to 300 kPa gauge pressure, such as from 200 kPa to 300 kPa gauge pressure. The greater pressure of the compressed gas242may improve the ability of the compressed gas242to dislodge the solid filter cake from the outer surface of the filter candles232during the gas pulsation. If the pressure of the compressed gas is less than about 170 kPa gauge pressure, the pressure of the compressed gas242may not be sufficient to dislodge and break apart the solid filter cake that is built up on the outer surface of the filter candles232, which can result in the outer surface of the filter candles232being at least partially blocked by pieces of the solid filter cake remaining on the filter material of the filter candles232. Thus, insufficient pressure can result in reduced filtering efficiency of the filter candle unit200A,200B,200C after the cleaning cycle.

During each pulse of the compressed gas242, the gas inlet control valve320is opened. The vent control valve322may be in the opened or closed positions during the pulse. In embodiments, each of the pulses of the compressed gas242may have a pulse duration of from 5 seconds to 30 seconds, such as from 5 seconds to 25 seconds, from 5 seconds to 20 seconds, from 10 seconds to 30 seconds, from 10 seconds to 25 seconds, from 10 seconds to 20 seconds, from 15 seconds to 30 seconds, from 15 seconds to 25 seconds, or from 20 seconds to 30 seconds. The duration of each pulse of the compressed gas may be greater than the duration of the compressed gas pulses during conventional operation of the candle filter system130. The increased pulse duration of the compressed gas pulses may increase the amount of solid filter cake dislodged and removed from the outer surface of the filter candles during each pulse.

At the conclusion of each pulse, the gas inlet control valve320is closed with the vent control valve322in the open or closed condition. During the duration of the idle period, the gas inlet control valve320may be in the closed position. In embodiments, each of the idle periods may have a duration of from 5 seconds to 60 seconds, such as from 5 seconds to 50 seconds, from 5 seconds to 40 seconds, from 10 seconds to 60 seconds, from 10 seconds to 50 seconds, from 10 seconds from to 40 seconds, from 20 seconds to 60 seconds, from 20 seconds to 50 seconds, from 20 seconds to 40 seconds, or any subranges between these values.

The alternating pulses of the compressed gas242separated by idle periods may be continued for a total gas pulsation duration. The total gas pulsation duration may be greater than the total duration of gas pulsation during conventional operation of the candle filter system130. In embodiments, the total gas pulsation duration may be greater than or equal to 10 minutes, such as from 10 minutes to 20 minutes. The greater total gas pulsation duration may further improve and increase the removal of the solid filter cake from the outer surfaces of the candle filters232. Improved removal of the solid filter cake from the outer surfaces of the candle filters232may provide lower pressure differential and greater filtration efficiency of the candle filter units200A,200B,200C when the candle filter units are returned to filtration mode. When the total gas pulsation duration is less than 10 minutes, the number and duration of compressed gas pulses may not be enough to dislodge all of the solid filter cake from the outer surfaces of the candle filters232, which can result in increased pressure differential and reduced filtration efficiency once the candle filter unit200A,200B,200C is transitioned back to the filtration mode.

In embodiments, pulsing the plurality of filter candles232with the compressed gas242may comprise generating a compressed gas pulsation signal and communicating the compressed gas pulsation signal to the gas inlet control valve320on a compressed gas inlet240of the candle filter unit200A,200B,200C. The compressed gas pulsation signal may cause the gas inlet control valve320to cycle between the open condition and the closed position for the plurality of alternating pulses and idle periods. In embodiments, the compressed gas pulsation signal may cause the gas inlet control valve320to remain in the open condition for a pulse duration of from 5 seconds to 30 seconds for each occurrence of the open condition, and remain the closed condition for a closed duration of from 5 seconds to 60 seconds during each of the idle periods. The modifications to the gas pulsation step of the cleaning cycle may improve removal of the solid filter cake from the outer surfaces of the filter candles232, which may reduce the pressure differential across the candle filter unit200upon transitioning from the cleaning cycle back to the filtration mode.

Referring again toFIG.5, after the gas pulsation step514, the method for conducting a cleaning cycle for the candle filter units includes the sedimentation step516. Referring again toFIG.3, during sedimentation, the solid filter cake dislodged from the filter candles232are allowed to settle in the vessel210for a period of time prior to discharging the pieces of the solid filter cake from the vessel210. In conventional operation of the candle filter system130, the sedimentation step of the cleaning cycle is typically less than 30 minutes. However, it was found that a sedimentation duration of less than 30 minutes for the sedimentation step was insufficient to allow all the solids to settle in the bottom of the vessel210of the candle filter units200when using the candle filter system130to remove dissolved solids from the MEG rich stream116. These solids remaining in the vessel210have to be filtered again using the candle filter unit200and end up deposited back onto the outer surfaces of the filter candles232when the candle filter unit200is transitioned back to filtration mode.

It was further found that settling and sedimentation of the solid filter cake pieces in the vessel210may be improved by increasing the sedimentation duration of the sedimentation step, which may reduce the residual solids remaining in the vessel210after removing the solid filter cake pieces from the vessel210. Reducing the amount of residual solids remaining in the vessel210may reduce the concentration of solids in the candle filter unit200when transitioning the candle filter unit200back to filtration mode. In other words, increasing the sedimentation duration may reduce the quantity of solids that must be filtered again using the candle filter system130. In embodiments, the sedimentation duration may be greater than or equal to 30 minutes, greater than or equal to 45 minutes, greater than or equal to 60 minutes, greater than or equal to 75 minutes, or greater than or equal to 90 minutes. In embodiments, the sedimentation duration may be from 30 minutes to 2 hours, such as from 30 minutes to 90 minutes, from 60 minutes to 2 hours, or from 60 minutes to 90 minutes.

Referring again toFIG.5, in embodiments, the methods510for conducting a cleaning cycle of the present disclosure may include conducting one or more subsequent iteration of at least a portion of the cleaning cycle if the pressure differential across the candle filter unit200is still high, such as greater than or equal to about 480 kPa (about 70 psi). The subsequent iterations of the cleaning cycle may further improve removal of the solid filter cake from the filter candles, which may increase the separation efficiency of the candle filter unit200once the candle filter unit200is transitioned back to the filtration mode. Referring toFIGS.3and5, in embodiments, the methods510for cleaning the one or more of the candle filter units200may include conducting an initial cleaning cycle; determining the pressure differential across the candle filter unit200as in step520inFIG.5; and when the pressure differential across the candle filter unit200after the initial cleaning cycle is greater than a subsequent cleaning cycle PDI threshold of about 480 kPa (about 70 psi), about 530 kPa (about 77 psi), about 550 kPa (about 80 psi), or even about 565 kPa (about 82 psi), then conducting one or more subsequent cleaning cycles in succession. A differential pressure greater than about 69 kPa (about 10 psi) may indicate that at least portions of the outer surfaces of the filter candles232may still be covered with solid filter cake, indicating that a subsequent cleaning cycle may be needed. In embodiments, the method may include conducting one or more subsequent cleaning cycles in succession when the pressure differential across the candle filter unit200is greater than or equal to about 69 kPa (10 psi).

Referring again toFIG.5and step520, determining the pressure differential across the candle filter unit200may be performed after the cake transfer step518of the initial cleaning cycle. Referring toFIG.3, determining the pressure differential across the candle filter unit200may include pressurizing the vessel210of the candle filter unit200and measuring the inlet pressure in the vessel210on the inlet side of filter candles232, measuring the outlet pressure on the downstream or outlet side of the filter candles232, and determining the differential pressure from the inlet pressure and the outlet pressure. In embodiments, determining the differential pressure may include measuring the inlet pressure of the MEG rich stream116at the MEG stream inlet220, measuring the outlet pressure of the MEG filtrate132at the filtrate outlet222, and determining the differential pressure from the inlet pressure and the outlet pressure, where the differential pressure is the absolute value of the difference between the inlet pressure and the outlet pressure. In embodiments, the inlet pressure may be measured with the inlet pressure sensor330. In embodiments, the outlet pressure may be measured with the filtrate outlet pressure sensor332. In embodiments, determining the differential pressure may comprise directly measuring a pressure difference between the MEG filtrate132at the filtrate outlet222and the MEG rich stream116at the MEG stream inlet220, such as by using a differential pressure transmitter.

Referring again toFIG.5, conducting each of the one or more subsequent cleaning cycles may comprise repeating the gas pulsation step514, followed by the sedimentation step516, and then followed by the cake transfer step518. Referring toFIG.3, conducting each of the subsequent cleaning cycles may include pulsing the plurality of filter candles232with the compressed gas242, wherein the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles232. Conducting each of the subsequent cleaning cycles may further include allowing solids from the solid filter cake to settle in the bottom of the vessel210for a sedimentation duration and removing the solids from the vessel210. In embodiments, when the pressure differential across the candle filter unit200after the initial cleaning cycle is less than the subsequent cleaning cycle PDI threshold, then a subsequent cleaning cycle may not be needed and the methods may include transitioning the candle filter unit200back to the filtration mode to resume filtering operations.

Referring again toFIG.3, conducting the one or more subsequent cleaning cycles for the candle filter unit200may further comprise providing the user interface device262having an extra cleaning cycle user input264, and activating the extra cleaning cycle user input262. Activating the at least one extra cleaning cycle user input262may cause the candle filter system130to automatically conduct a subsequent cleaning cycle after the initial cleaning cycle. In embodiments, the candle filter control system300and user interface device262may be configured, such as through the computer readable and executable instructions, to only display the extra cleaning cycle user input264when the differential pressure is greater than or equal to the subsequent cleaning cycle PDI threshold. In embodiments, conducting the one or more subsequent cleaning cycles may further comprise displaying a message on the user interface device262, where the message provides a recommendation for conducting a subsequent cleaning cycle based on the pressure differential after conducting the initial cleaning cycle. In embodiments, the machine readable and executable instructions306, when executed by the processors302, may cause the candle filter control system300to automatically determine the differential pressure across the filter candles232after the cake removal step518(FIG.3) and, when the pressure differential is greater than the subsequent cleaning cycle DPI threshold, display a message on the user interface device262indicating that a subsequent cleaning cycle is recommended. The message may indicate which candle filter unit200may have a pressure differential greater than the subsequent cleaning cycle DPI threshold, such as greater than or equal to about 69 kPa (about 10 psi).

In embodiments, the machine the machine readable and executable instructions306, when executed by the processors302, may cause the candle filter control system300to automatically determine the differential pressure across the filter candles232after the cake removal step518(FIG.3), and automatically conduct one or more subsequent cleaning cycles when the differential pressure is greater than the subsequent cleaning cycle DPI threshold. In other words, the candle filter control system300may be configured to automatically conduct the one or more subsequent cleaning cycles, when needed, without further input from the user interface device262.

Following the cleaning cycle, and any subsequent cleaning cycles, the candle filter system130or one or more of the candle filter units200of the candle filter system130may be returned to the filtration mode. In embodiments, the methods may include determining a pressure differential across the filter candles232after the initial cleaning cycle or a subsequent cleaning cycle, and when the pressure differential is less than the subsequent cleaning cycle PDI threshold, transitioning the candle filter unit200from the cleaning cycle mode back to the filtration mode to resume filtering. In embodiments, the methods disclosed herein may include resuming filtration of the MEG rich stream116after the cleaning cycle or subsequent cleaning cycles.

In certain circumstances, such as when the incoming MEG rich stream116has high TDS or when the cleaning cycles did not remove all of the solid filter cake from the outer surfaces of the filter candles232, the candle filter control system300may have a high pressure differential shutdown sequence. During the high pressure differential shutdown sequence, the candle filter control system300may identify a high pressure differential condition during start-up of a candle filter unit200, such as a spike in pressure differential experienced while transitioning the candle filter unit200from the cleaning cycle mode to the filtration mode to begin filtering, and may shutdown the candle filter unit200or prevent the candle filter unit200from starting up in the filtration mode in response to the high pressure differential condition. When the high pressure differential shutdown occurs during start-up or during transitioning to the filtration mode, the candle filter unit200or the candle filter system130as a whole may be shut down and prevented from filtering. This can cause disruptions in the recovery of the MEG from the MEG rich stream116. In some circumstances, such as when the spike in pressure differential is caused by high TDS of the MEG rich stream116, shutdown of the candle filter system130or one of the candle filter units200may not be required.

In embodiments, the candle filter system130may comprise a start-up override, which may be operable to bypass the high pressure differential shutdown sequence automatically while transitioning one or more of the candle filter units200from the cleaning cycle mode to the filtration mode. Referring toFIGS.1and3, in embodiments, resuming filtering operation of the one or more candle filter units200may comprise overriding the high pressure differential shutdown sequence. In embodiments, overriding the high pressure differential shutdown sequence may comprise verifying that sufficient volumes of MEG are present in downstream processes, such as but not limited to the MEG distillation column142, the MEG reboiler160, the lean MEG storage tank, or combinations of these; starting a filtration sequence or opening a filtrate control valve312on filtrate outlet222of the vessel210for one or more of the candle filter units200A,200B,200C; determining that the pressure differential is greater than or equal to 70 psi (482 kPa); and bypassing the high differential pressure shutdown sequence.

The candle filter control system300may include a reboiler trip shutdown sequence. During operation of the candle filter system130, certain downstream operating conditions, such as a reboiler trip alarm, may cause the candle filter system130to shutdown or fail to startup. This reboiler trip shutdown sequence may prevent the candle filter system130from operating or may prevent one or more candle filter units200A,200B,200C from starting filtration mode. In embodiments, the candle filter control system300may comprise the reboiler trip override sequence, which may be operable to confirm that sufficient MEG is present in downstream systems and then, when sufficient MEG is present, overriding the reboiler trip shutdown sequence. The candle filter control system300may be communicatively coupled to one or more downstream sensors350, which may be operable to send signals indicative of conditions of one or more downstream systems. The downstream sensors350may include but are not limited to one or more of an MEG level sensor in the MEG reboiler160, a run dry sensor for the lean MEG pump166, other sensor, or combinations thereof. The candle filter control system300may have machine readable and executable instructions306that, when executed by the processors302, may cause the candle filter control system300to receive one or more control signals from the downstream sensors350, confirm that sufficient MEG is in the downstream systems, and when sufficient MEG is present in the downstream systems, bypass the reboiler trip shutdown sequence.

Referring toFIG.1, as previously discussed, the candle filter control system300may include the one or more processors302and one or more memory modules304. The one or more processors302may include any device capable of executing computer-readable executable instructions stored on a non-transitory computer-readable medium. Accordingly, each processor302may include an integrated circuit, a microchip, a computer, and/or any other computing device. The one or more memory modules304are communicatively coupled to the one or more processors302over a communication path. The one or more memory modules304may be configured as volatile and/or nonvolatile memory and, as such, may include random access memory (including SRAM, DRAM, and/or other types of RAM), flash memory, secure digital (SD) memory, registers, compact discs (CD), digital versatile discs (DVD), and/or other types of non-transitory computer-readable mediums. The one or more memory modules304may be configured to store machine readable and executable instructions306for operating one or more components of the candle filter system130.

Embodiments of the present disclosure include logic stored on the one or more memory modules304that includes machine-readable and executable instructions or an algorithm written in any programming language of any generation (e.g., 1GL, 2GL, 3GL, 4GL, and/or 5GL) such as, machine language that may be directly executed by the one or more processors302, assembly language, obstacle-oriented programming (OOP), scripting languages, microcode, etc., that may be compiled or assembled into machine readable instructions and stored on a machine readable medium. Similarly, the logic and/or algorithm may be written in a hardware description language (HDL), such as logic implemented via either a field-programmable gate array (FPGA) configuration or an application-specific integrated circuit (ASIC), and their equivalents. Accordingly, the logic may be implemented in any conventional computer programming language, as pre-programmed hardware elements, and/or as a combination of hardware and software components.

In a first aspect of the present disclosure, method of operating a candle filter system for removing solids from monoethylene glycol (MEG) recovered from drilling fluids may comprise passing an MEG rich stream to a candle filter system comprising a plurality of candle filter units operated in parallel and a slurry vessel disposed downstream of the candle filter system. The MEG rich stream may comprise at least the MEG and dissolved solids and each of the plurality of candle filter units comprises a vessel, a register, and a plurality of filter candles fluidly coupled to the register. The method may further comprise determining a concentration of total dissolved solids in the MEG rich stream, determining whether to operate the candle filter system in a low TDS mode or a high TDS mode based on the concentration of total dissolved solids (TDS) in the MEG rich stream, filtering the MEG rich stream in the plurality of candle filter units to produce a filtrate and a filter cake deposited on outer surfaces of the filter candles of the candle filter units, determining to conduct a cleaning cycle for one or more of the plurality of candle filter units based on a pressure differential across the plurality of candle filter units, and conducting a cleaning cycle to remove the filter cake from the outer surfaces of the filter candles. Conducting the cleaning cycle my comprise reducing a pressure in the one or more candle filter units; draining a residual volume of the MEG rich stream all the way to the slurry vessel disposed downstream of the candle filter system; after the draining, pulsing the plurality of filter candles with a compressed gas, where the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles; allowing solids from the solid filter cake to settle in a bottom of the vessel for a sedimentation duration; and removing the solids from the vessel. The method may further include resuming filtering operation of the one or more candle filter units.

A second aspect of the present disclosure may include the first aspect, where the determining a concentration of total dissolved solids in the MEG rich stream may comprise measuring the concentration of total dissolved solids (TDS) in the MEG rich stream.

A third aspect of the present disclosure may include either one of the first or second aspects, where whether to operate the candle filter system in a low TDS mode or a high TDS mode may comprises: when the concentration of TDS in the MEG rich stream is less than a threshold concentration, then operating the candle filter system in the low TDS mode; and when the concentration of total dissolved solids in the MEG rich stream is greater than or equal to the threshold concentration, then operating each of the plurality of candle filter units in the high TDS mode.

A fourth aspect of the present disclosure may include any one of the first through third aspects, comprising operating the candle filter system in the low TDS mode, where in the low TDS mode, the candle filter system may be operated in a swing mode in which at least a first candle filter unit is operating in a filtering mode, and a second candle filter unit is in a standby mode. When the at least one first candle filter in filtering mode reaches a high pressure differential condition, the at least one first candle filter unit may be transitioned to cleaning mode while the second candle filter unit is transitioned to filtering mode. The method may further comprise, following conducting the cleaning cycle on the at least one first candle filter unit, transitioning the first candle filter unit to the standby mode.

A fifth aspect of the present disclosure may include any one of the first through fourth aspects, comprising operating the candle filter system in the high TDS mode, where in the high TDS mode, the candle filter system may be operated with each of the candle filters in a filtering mode and none of the candle filter units in the standby mode.

A sixth aspect of the present disclosure may include the fifth aspect, where in the high TDS mode, each of the candle filter units may be operated in parallel at 100% capacity or at 50% capacity.

A seventh aspect of the present disclosure may include any one of the first through sixth aspects, comprising, in the low TDS mode, operating each of the candle filter units of the candle filter system at 100%, and in the high TDS mode, operating each of the candle filter units at 50%.

An eighth aspect of the present disclosure may include any one of the first through seventh aspects, where the pulsing the plurality of filter candles with the compressed gas may comprise generating a compressed gas pulsation signal, and communicating the compressed gas pulsation signal to a gas inlet control valve on a compressed gas inlet of the one or more candle filter units, where the compressed gas pulsation signal may cause the gas inlet control valve to cycle between an open condition and a closed position for to produce a plurality of alternating pulses and idle periods.

A ninth aspect of the present disclosure may include the eighth aspect, where the compressed gas pulsation signal may cause the compressed gas control valve to remain in the open condition for an open duration of from 5 seconds to 30 seconds for each occurrence of the open condition, and remain the closed condition for a closed duration of from 5 seconds to 60 seconds during each open-close cycles.

A tenth aspect of the present disclosure may include any one of the first through ninth aspects, where the compressed gas may be nitrogen gas.

An eleventh aspect of the present disclosure may include any one of the first through tenth aspects, where the pressure of the compressed gas may be from 275 kPa to 400 kPa absolute pressure.

A twelfth aspect of the present disclosure may include any one of the first through eleventh aspects, comprising pulsing the plurality of filter candles with the compressed gas for a total pulsation duration of greater than or equal to 10 minutes.

A thirteenth aspect of the present disclosure may include any one of the first through twelfth aspects, where the sedimentation duration may be greater than or equal to 30 minutes.

A fourteenth aspect of the present disclosure may include any one of the first through thirteenth aspects, further comprising conducting an initial cleaning cycle and measuring the pressure differential across the candle filter unit, where the pressure differential is indicative of a difference between an inlet pressure of the MEG rich stream at an MEG stream inlet and an outlet pressure of the filtrate at a filtrate outlet. The method may further comprise, when the pressure differential across the candle filter unit after the first cleaning cycle is greater than 69 kPa (10 psi), then conducting one or more subsequent cleaning cycles in succession.

A fifteenth aspect of the present disclosure may include the fourteenth aspect, where conducting each of the one or more subsequent cleaning cycles may comprise repeating the steps of pulsing the plurality of filter candles with a compressed gas, wherein the pulsing causes separation of the solid filter cake from the outer surfaces of the filter candles; allowing solids from the solid filter cake to settle in a bottom of the vessel for a sedimentation duration; and removing the solids from the vessel.

A sixteenth aspect of the present disclosure may include either one of the fourteenth or fifteenth aspects, where when the pressure differential across the candle filter unit after the initial cleaning cycle is less than 69 kPa (about 10 psi), transitioning the candle filter unit to a filtering mode to resume filtering operations.

A seventeenth aspect of the present disclosure may include any one of the fourteenth through sixteenth aspects, where conducting the one or more subsequent cleaning cycles may comprise providing a user interface device having an extra cleaning cycle user input and activating the extra cleaning cycle user input. Activating the at least one extra cleaning cycle user input may cause the candle filter system to automatically conduct the one or more subsequent cleaning cycles after the initial cleaning cycle.

An eighteenth aspect of the present disclosure may include the seventeenth aspect, where conducting the one or more subsequent cleaning cycles further may comprise displaying a message on the user interface device, where the message may provide a recommendation for conducting a subsequent cleaning cycle based on the pressure differential after conducting the first cleaning cycle.

A nineteenth aspect of the present disclosure may include any one of the first through eighteenth aspects, where resuming filtering operation of the one or more candle filter units may comprise overriding a high pressure differential shutdown sequence.

A twentieth aspect of the present disclosure may include the nineteenth aspect, where overriding the high pressure differential shutdown sequence may comprise verifying that sufficient volumes of MEG are present in downstream processes; starting a filtration sequence or opening a filtrate control valve on filtrate outlet of the vessel; determining that the pressure differential is greater than or equal to 70 psi (482 kPa); and bypassing the high differential pressure shutdown sequence.

A twenty-first aspect of the present disclosure may include any one of the first through twentieth aspects, where determining to conduct a cleaning cycle for one or more of the plurality of candle filter units may comprise measuring a pressure differential across the plurality of candle filter units and determining to conduct the cleaning cycle when the pressure differential across the plurality of candle filter units is greater than a threshold pressure differential.

A twenty second aspect of the present disclosure may include the twenty-first aspect, where the threshold pressure differential is 70 psi, 75 psi, 77 psi, or even 80 psi.

Examples

The various aspects of the present disclosure will be further clarified by the following examples. The examples are illustrative in nature and should not be understood to limit the subject matter of the present disclosure.

An MEG rich stream having a constant concentration of total dissolved solids was introduced to a candle filter system having 3 candle filter units as shown inFIG.3. The candle filter system was operated at a constant overall flow rate through the candle filter system. The candle filter system was first operated in a normal operating mode, such as a low TDS mode, in which the MEG rich stream was filtered through two of the candle filter units while the third candle filter unit was maintained in a standby condition pending one of the other two candle filter units having to switch to a cleaning mode. In the low TDS mode, the total flow through the candle filter system was divided between the two candle filter units operating in filtration mode. Referring now toFIG.6, during low TDS mode of operation, the candle filter system experienced an initial pressure differential (PDI) across the candle filter system of 16 psig (110 kPa gauge pressure), which rapidly increased to close to 74 psig (510 kPa gauge pressure) in 48 minutes, at which point the candle filter system had to be shut down manually for cleaning.

After a cleaning cycle, the operation of the candle filter system was then restarted in the high TDS operating mode. In the high TDS mode, the candle filter system was operated with all three candle filter units in filtration mode, and the overall flow rate through the candle filter unit was divided between the three candle filter units. Referring toFIG.6, when operated in high TDS mode, the overall pressure differential across the candle filter system was about 2 psig (14 kPa gauge pressure) initially. Over a period of about six hours, the pressure differential across the candle filter system only increased to a maximum pressure of 21 psig (145 kPa gauge pressure). In the high TDS operating mode, the candle filter system was able to be operated continuously for more than about 14 hours before requiring shutdown for cleaning the solids from the filter candles. This demonstrates that the new high TDS operating mode can greatly increase the total run time of the candle filter system when filtering MEG rich stream having high TDS.

It is noted that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure.

It is noted that one or more of the following claims utilize the term “where” as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”

Having described the subject matter of the present disclosure in detail and by reference to specific aspects, it is noted that the various details of such aspects should not be taken to imply that these details are essential components of the aspects. Rather, the claims appended hereto should be taken as the sole representation of the breadth of the present disclosure and the corresponding scope of the various aspects described in this disclosure. Further, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims.