improvements to conﬁgurations of natural gas liquefaction ... · pdf filefloating liquefied...

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Improvements to configurations of naturalgas liquefaction cycles

Said Al Rabadi1∗

�∗ Department of Chemical Engineering

Al Balqa Applied University, P.O. Box 50, 21510 Huson Jordan

Tel: +962 2 7010400, Email: [email protected]

The Eighth Jordan International Chemical Engineering Conference (JIChEC 2017)

November 7-9, 2017

mailto:[email protected]

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Abstract-- The most important challenge in anatural gas liquefaction plants is to improve theplant energy efficiency. A process topology should beimplemented, which results in a considerablereduction of energy consumption as the natural gasliquefaction process consumes a large amount ofenergy. In particular, system design focusing onconfiguring cold part cycle is an attractive option. Inthis study, various energy recovery-oriented processconfigurations and the potential improvements ofenergy savings for small- & mid-scale LNG plantswere proposed and compared with almost exclusivelycommercial trademarks processes. The proposedconfigurations were validated by modeling andsimulation runs under the variation in feed gaspressure, MR cooling reference temperature and thepinch temperature of cryogenic PFHE. Thesimulation results exhibited considerable reductionof specific total energy consumption. Therefore, theproposed liquefaction cycles have a simple topologyhence lower capital cost and compacter plant layout,which is compatible for power-efficient, offshore,floating liquefied natural gas liquefaction plants.

Keywords: Liquefaction, natural gas, MRC, PFHE,design parameters

1. IntroductionLiquefaction process of natural gas includes thephysical conversion of NG from gas to liquidphase. Liquefied natural gas takes up a factor ofabout 1/600th the volume of natural gas in thegaseous state. The natural gas is then condensedinto a liquid phase at close to atmosphericpressure by cooling it to approximately −160 °C(−260 °F) [1, 2]. Cryogenic LNG carriers orcryogenic road/trail tankers are used for itstransport. LNG is principally used fortransporting natural gas, where it is then re-gasified and distributed to the markets.

The natural gas fed into the LNG plant will betreated to remove condensate, Mercury, H2S,COx and NOx that will freeze under thecryogenic temperature ranges [4]. A typical LNGprocess is shown in Fig. 1. NG is first extractedand transported to a processing plant, where thefeed gas pressure is presumed at a certain figure.After that NG is treated against any heavyhydrocarbons and mud/ slug, it is then purifiedby removing acid gases such as CO2, NOx andH2S by utilizing an Amine washing solvent. Thissolvent is regenerated by introducing it tostripper column (by products like sour gas andwaste water are obtained and disregarded to abattery limit). At this stage the sweet NG streamis wet and still might contain traces of Mercury,LNG process train is designed to remove any Hgcontent to prevent mercury amalgamizing withaluminium in the cryogenic heat exchangers,

while the water content is adsorbed in a specialdehydration unit. The drier is regenerated by theboil off gas obtained from downstream storageunit. The gas is then cooled down in stages untilit is liquefied. LNG is finally stored in storagetanks to be loaded and shipped.

Fig. 1: Block diagram of a LNG process

The heart of a LNG plant, as highlighted in Fig.1, is NG liquefaction and refrigeration cycle,where these stages are the highest energy densityunits of a LNG plant. Hence then designing theseunits will have the major impact on the capitaland operating costs of the plant. In order to reachthe cryogenic temperature ranges for liquefyingNG, a mixture of Nitrogen and lighthydrocarbons mainly Methane, Ethane andPropane is implemented as refrigerant. As shownin PT curve for different gases presented in Fig.2, where the vapour pressure is plotted as afunction of gas temperature. Such a refrigerantmixture can reduce the process temperature to acryogenic range lower than -190°C at 1 bar,which is quite enough for liquefying NG. Thecomposition of MRC is subject to alternationdepending on the NG composition as well to thefeed gas operating pressure (shown in thevariation of NG condensation curves at pressureof 1 bar and 25 bar) and the reference coolingrefrigeration temperature.

Fig. 2: PT diagram from different gases [1]

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In this study, theoretical investigations on theNG liquefaction and refrigeration cycle withdifferent topologies were performed, utilizing theso called UNISIM as the process simulator. Alsothese investigations are valid for small- & mid-scale plants from the plant capacity point ofview. The purpose of these theoreticalinvestigations is to identify the improvements ofprocess configurations of natural gas liquefactioncycles, and to be compared with trademarks ofrefrigeration processes. The comparing criteriainclude the specific energy consumption withrespect to the variation in feed gas pressure, MRcooling reference temperature and the pinchtemperature of PFHE.

The pre-defined process parameters are listed intable 1. Three main streams are foreseen thathave their process flow conditions have themajor impacts on the design criteria of PFHE,named as NG stream to PFHE, LNG productstream from PFHE routed to LNG storage tankand Fuel stream obtained as boil off gas streamobtained from storage tank. The Fuel stream isprincipally a cold temperature stream that shouldbe warmed to near room temperature conditionsfor better combustion conditions as well to getbenefit of its cooling duty in PFHE, hence todecrease cooling duty of MRC compressor. Atypical lean natural gas feed stream is consideredfor the theoretical investigations, where itsMethane content concentrates to more than 90mol % due to upstream processing units (namelySlug Catcher for capturing solid particulates inNG feed, Amine washing and dehydration [3 –6]) of other associated components in NG.Ethane and Propane contents in LNG stream arepresumed around the typical figures in order tomeet the foreseen heating value of LNG; typicalLNG heating values in the range of 17,500 -21,500 BTU/lb [7]. Nitrogen due to its lowerboiling temperature than that of Methanebasically concentrates in the fuel gas stream,which can be operated by conventional gasturbine without further obstacles [8].

Table 1: Process parameters of natural gasstreams

LNG processes are licensed by large oil and gascompanies, but are generally based on a one- ormulti-stage cooling process with pure or mixedrefrigerants. The main types of LNG process arelisted in table 2, including mainly cascade, MRand expander/ booster processes. Each processhas different characteristics in scalability,investment cost and energy efficiency. Forfloating LNG, e.g., possibly lower weight isdesired due to its low CAPEX, even its energyefficiency is significantly lower than the bestcascade or MR processes. The reason is that thegas has a heat load to temperature (Q/T) curvethat will improve stability, throughput andefficiency. The curve tends to show three distinctregions; pre-cooling, liquefaction and sub-cooling. All of these zones are characterized byhaving different curve behaviours, or specificheats, along the process. Keep in mind that the(Q/T) curve shape is different for different gascompositions.

Table 3 shows the boundary conditions for allMRC processes. These boundary conditions arevalid for a MR cooling reference temperature of30°C and an outlet pressure of 65 bar from 2nd

stage cycle compressor.

Table 2: List of commercial LNG refrigeration processes

Process Licenser Features

SMR

RRI CO [16] Black & Veatch SMR, Limited capacity ≤ 1.3 MTPA, low CAPEXDMR [14] Shell Two refrigerant cycles, large scale, high CAPEXMFCP [7, 8, 10] Statoil/ Linde Mixed refrigerant cycles, large capacity, need for

external refrigerants storage, high CAPEXLIMUM [12] Linde SMR, large scale, need for external refrigerants

storage

Cas

cade

Cascade cycle[13, 15]

Conoco Phillips Separate refrigerant cycles with C3, Ethylene and C1,large capacity, high CAPEX

C3MR[13] APCI Utilizes two C3 and MR cycles, widely spread, largecapacity ≥ 5 MTPA, low energy density

Stream NG LNG FuelTemp [K] 303.2 112.0 299.0P [bar] 65 1.2 1Massflow

[t/h] 339.7 300 39.7

CH4 [mol %] 91.7 92.9 81.98C2H6 [mol %] 5.25 5.9 0.01C3H8 [mol %] 0.35 0.4 traceN2 [mol %] 2.7 0.8 18.01

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Self-refrigeratedLNG [11]

BP No compressor, low production rate (high energydensity), capacities ≥ 1.3 MTPA

Exp

ande

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oste

r

Expander cycle[9, 10]

Kryopak Expander/ booster, no liquid refrigerant, high energydensity

Table 3: Overview of MRC boundary conditions for all investigated processes valid for a MR coolingreference temperature of 30 ºC and an outlet pressure of 65 bar from MRC 2nd stage cyclecompressor.

Process

Symbol [Unit]

Simulation value *

1 2 3 4 5 6 7

PFHEdTmin [K] 2.0 3.7 3.7 3.8 3.6 3.6 3.6dpFuel [bar] 0.2 0.2 0.2 0.2 0.2 0.2 0.2dp [bar] 0.4 0.4 0.4 0.4 0.4 0.4 0.4Qiso [kWh/tLNG] 3.33 3.33 3.33 3.33 3.33 3.33 3.33MRC 1st Stage Compressorηisen [%] 80 80 80 80 80 80 80Tinlet [K] 299.9 298.2 298.6 300.5 299.5 300.6 298.9Toutlet [K] 376.9 409.6 383.5 389.6 376.3 373.4 385.2Poutlet [bar] 6.2 39.0 25.9 17.3 24.8 25.8 26.1dp [bar] 0.3 0.3 0.3 0.3 0.3 0.3 0.3MRC 2nd Stage Compressorηisen [%] 80 80 80 80 80 80 80Toutlet [K] 423.1 339.4 369.0 393.7 380.6 370.5 395.6Poutlet [bar] 40.6 65 65 65 65 65 65MRC pumpPinlet [bar] - - 25.4 16.8 24.3 25.3 -Cooling Water Heat ExchangersdpMR [bar] 0.5 0.5 0.5 0.5 0.5 0.5 0.5* These figures are deduced from reference operating plants

Based on practice of the MRC processes forsmall- & mid-scale plants with differentconfigurations, seven topologies are presentedbelow for the purpose of these investigations.They utilize two stages MRC compressors. In thefirst stage the pressure is increased from suctionpressure of about 2 bar to MP figures, and in thesecond stage the MP values are increased to HPof 65 bar. This value is kept at identical value of65 bar for all investigated processes. Process 1and 7 represent the so called PRICO and theenhanced PRICO processes respectively, while 2till 5 actual topologies collected from diversesmall- & mid-scale LNG plants, which wereconstructed and taken in operation underdifferent metrological regions. Process 6 isenriched with potential modifications with theaim to increase the refrigeration processefficiency as well as plant stability.

In principle, process 1 is a MRC process withoutMRC pump nun MP separator, Fig. 3. The

cooling is provided by a closed MRC, whichconsists of a components mixture like Nitrogen,Methane, Ethane and Propane, its compositiondepends on the process operating conditions. Therefrigerant is withdrawn from PFHE at atemperature of approx. 299.9K and a pressure ofapprox. 1.9 bar (Minimum suction pressure isforeseen about 2 bar). It is compressed in the 1st

stage refrigerant cycle compressor, and cooledagainst cooling water in Cycle Compressor Aftercooler to a MR cooling reference temperature of30°C. The gaseous refrigerant is furthercompressed in the 2nd stage cycle compressorand afterwards cooled against cooling water to aMR cooling reference temperature of 30°C. Thegas will be partially condensed. Liquid and gasare separated in HP Separator. The liquid fromthe HP separator is rooted to PFHE where it issub-cooled and then is used for the pre-coolingof the natural gas after expansion in a Joule-Thomson expansion valve. The gas MR from HPseparator is cooled in PFHE and provides the

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final cold for the natural gas sub-cooling afterexpansion in Joule-Thomson expansion valve.After expansion to a pressure of approx. 2.6 bar,the gas MR stream is warmed up in PFHE andreturns to the suction side of the 1st stage CycleCompressor. The composition of the MRCstream to the 2nd stage cycle compressor ischanged due to mixing the liquid MR streamrouted from HP separator to PFHE with theoutlet stream from 1st stage after cooler. Thecycle liquid refrigerant stream routed from HPseparator to PFHE is overheated above dewpoint temperature with a temperature margin of 5K for protecting the downstream MRCcompressor from two-phase flow. Make up forthe refrigerant system is required mainly due toMR losses via the gas seals of the MRCCompressor.

Process 2: MRC Process is without MRC pumpidentical to process 1, nevertheless withinclusion of MP separator, refer to Fig. 4, otherprocess flow conditions are almost similar. MPseparator is foreseen to have an impact on thebehaviour of (Q/T) diagram in the pre-coolingregion, through the inclusion of liquid MP MR toPFHE and hence changing the NG pre-coolingduty. HP MR liquid stream provides the pre-cooling duty of NG after expansion in JT valveat the warm end of PFHE. While HP MR gasstream provides the sub-cooling duty of NG atthe cold end of PFHE after expansion in JTvalve.

Fig. 3: Descriptive sketch of process 1

Fig. 4: Descriptive sketch of Process 2

Process 3: MRC Process with MP separator likein process 2, with the difference the liquid MRfrom MP separator is pumped and combinedwith the partially condensed outlet MR streamfrom MRC 2nd stage compressor after cooler,then it is routed to HP separator. Although of theexpected higher energy consumption due toMRC pump as well the increased CAPEX,Process 3 is modified to meet certain coolingprocess demands, refer to Fig. 5.

Fig.5: Descriptive sketch of Process 3

Process 4: MRC Process with mixing liquid andgaseous MR streams from both warm & coldends of PFHE, refer to Fig. 6, other MRCprocess conditions are identical to process 3. TheMR gas stream from HP separator is combinedwith the MR liquid stream (mixing cold and

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warm parts of PFHE), then both streams arejoined and warmed up in PFHE and return to thesuction side of the 1st stage Cycle Compressor.Although keeping this stream at a safety marginfrom dew point to protect the downstream 1st

stage MRC compressor, the combination of bothstreams have to a great extent an impact onliquefaction duty of PFHE.


Process 5: Refrigeration Process with mixingliquid and gas HP MR streams from both warm& cold ends of PFHE, and using a cold MRCseparator at the cold end of PFHE, other MRCprocess conditions are identical to process 4,refer to Fig. 7. The liquid from the cold MRCseparator is sub-cooled in PFHE and is used asrefrigerant for PFHE after expansion in a JouleThomson expansion valve. The gas stream fromthe cold MRC separator is cooled, hence ispartially condensed in PFHE to provide the finalcold for NG sub-cooling after expansion in aJoule Thomson expansion. Then the HP MR gasstream is warmed up in PFHE and mixed withthe cycle MR liquid stream from the cold MRCseparator after expansion at the cold part ofPFHE, then the resulting two phase stream iswarmed up in PFHE. The two phase stream ismixed again with the cycle liquid MR streamafter expansion at the warm part of PFHE thenreturns to the suction side of the 1st stage CycleCompressor. In spite of the increased CAPEX ofthis process, it is believed that the combined twophase MR stream would provide moresignificant pre-cooling duty of PFHE, as wellachieve a considerable safety margin from dewpoint of this stream to protect 1st Stage MRCcompressor.

Process 6: MRC Process with PFHE, isconsidered for the comparison in theseinvestigations and is briefly presented in Fig. 8.Two MRC pumps are implemented in thisprocess. First to pump liquid MR stream fromMP separator to HP separator, the second pumpis used to transport liquid MR from HP separatorto be combined with the gas MR from HPseparator. Combined stream, after expansion inJT valve, it provides the liquefaction and pre-cooling duties of PFHE. It is believed, even ofthe increased number of pumps, that the PFHE iscompacter compared to process 5. Hence then asignificant lower layout of the cold box isachieved.

Process 7: MRC (Enhanced PRICO) process ispresented in Fig. 9. Briefly, this process topologyis almost similar to that of process 5, with thedifference that liquid MR from HP separator isrouted back after expansion in JT valve to aclassical shell and tube heat exchanger, where itis warmed against the liquid MR from MPseparator to essentially provide the pre-coolingduty of PFHE through the liquid MR from MPseparator after its JT expansion at the warm endof PFHE. As mentioned above, the presence ofcold MR separator promotes the sub-coolingduty of PFHE.


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Fig.8: Model Refrigeration Process 6

Fig.9: Descriptive sketch of Process 7

2. Results and DiscussionsThe findings of the theoretical investigations ofabove mentioned processes are deduced from thebehavior of (Q/T) diagram of PFHE for eachprocess, and the specific total energyconsumption (energy consumed per producedton of LNG) under the variation of the MRcooling reference temperature as well the feedgas pressure. Fig. 10 shows (Q/T) diagram ofthe cold and warm streams of PFHE (leftabscissa) as well the temperature difference(right abscissa) as a function of specific heattransfer within the PFHE for process 1. As bothwarm and cold streams of PFHE lay close toeach other without intersection; it can beindicated that the work done by MRCcompressor is minimum. Here the maximaltemperature difference of about 16 K is found onthe warm part of PFHE, providing a phasechange in MR, while a temperature difference of

about 6K is obtained on the cold part of thePFHE referring to the exergy losses on the coldpart of the process. This adaptability in (Q/T)diagram is, in general, taken as an indication tothe effectiveness of the relevant MRC process.

Fig. 10: PFHE (Q/T) diagram of Process 1

As Fig. 11 shows the specific energyconsumption as a function of MR coolingreference temperature and feed gas pressure. Ingeneral, the MRC process is more effective (lessspecific energy consumption) when feed gas isoperated under high pressures and lower MRcooling reference temperatures (low to moderateclimate conditions), since lower cooling duty onMRC Compressor is required. By optimizedprocess conditions achieving a pinch temperature(minimum temperature difference between coldand warm streams) for PFHE of 2K, the specificenergy consumption for this process1 is readingthe value of 285 kWh/tLNG at 65 bar feed gaspressure and MR cooling reference temperatureof 30C, which is within the range ofconventional single MRC process (typically 250– 350 kWh/tLNG [3, 4]).

Fig. 11: Specific energy consumption ofprocess 1

Fig. 12 shows (Q/T) diagram of the cold andwarm streams of PFHE (left abscissa) as well thetemperature difference (right abscissa) as afunction of specific heat transfer within thePFHE for process 2. As expected the inclusion ofMP separator enhances the pre-cooling duty of

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PFHE. An improvement on total energyconsumption is achieved for process 2 withrespect to process 1, enhancement of pre-coolingduty means a significant reduction on theisentropic work done by 1st MRC stagecompressor. The maximal temperature differenceis reduced to 13K, obtained at the warm part ofPFHE, that is synchronized with a temperaturedifference of 18K, this is due to the phase changein the light and heavy MR streams in PFHE. Onthe other hand, the cold and warm streams arelaying closer, which is in turn an indication forthe further improvement of the effectiveness ofprocess 2.


Fig. 13 shows the specific energy consumptionas a function of MR cooling referencetemperature and feed gas pressure. Incomparison to scheme 1.3 lower specific energyconsumption is obtained with respect to that ofprocess 1 by a factor of 3%.

Fig. 13: Specific energy consumption ofProcess 2

Fig. 14 shows (Q/T) diagram of the cold andwarm streams of PFHE (left abscissa) as well thetemperature difference (right abscissa) as afunction of specific heat transfer within thePFHE for process 3. The maximal temperaturedifference is reduced to 12K on the warm part ofPFHE in comparison to that of process 1, atemperature difference of about 14K obtained onthe cold part of PFHE.


Findings in Fig. 15 are similarly obtainedcompared to those of previous 11 & 13.


Fig. 16 presents (Q/T) diagram of the cold andwarm streams of PFHE (left abscissa) as well thetemperature difference (right abscissa) as afunction of specific heat transfer within thePFHE for process 4. A reduce of about 7% intotal specific Here the effect of the furtherimprovements (MRC pump and mixing the coldand warm parts of PFHE) on MRC processperformance highlights that a maximaltemperature difference of about 12 K on thewarm part of PFHE and 18K on the cold part ofPFHE are obtained. This process reads a furtherreduction in the specific energy consumption ofabout 12 % in comparison to that of process 1.Fig. 17 presents that the findings are in goodagreement with previous relevant schemes.energy consumption in comparing to that ofprocess 1 at 65 bar inlet feed pressure and MRcooling reference temperature of 30 ºC. It isobserved that the behaviour of temperaturedifference in the liquefaction region of PFHE hastwo jumps, due to enhancement in thecondensation curve for NG. This is achievedbecause of MRC pump.

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Fig. 16: PEHE (Q/T) diagram of Process 4


Fig. 18 presents (Q/T) diagram of the cold andwarm streams of PFHE (left abscissa) as well thetemperature difference (right abscissa) as afunction of specific heat transfer within thePFHE for process 5. The relevant improvementsinclude MRC pump, mixing of cold and warmstreams as well MR cold separator. Theseimprovements indicate significant enhancementson pre-cooling and liquefaction duties comparedto those obtained in process 4, furtherenhancement is gained for sub-cooling duty ofPFHE because of MR cold separator. Thisfinding is proven in the behavior of temperaturedifference curve with respect to that of process 4.


Obtaining a maximal temperature difference ofabout 8K on the warm part of PFHE, 8K around

the mixing point and 14K at cold part of PFHE.Also findings in Fig. 19 are in good agreementwith above mentioned facts. The MRC process ismore effective (less specific energyconsumption) with a factor about 14% withrespect to that of process 1.


Fig. 20 presents (Q/T) diagram of the cold andwarm streams of PFHE (left abscissa) as well thetemperature difference (right abscissa) as afunction of specific heat transfer within thePFHE for process 6. Obtaining a maximaltemperature difference of about 8K on the warmend and 18K on the cold end of PFHErespectively, due to the warming of two phasestream fed from the position of mixing gas andliquid MR from HP separator prior to be routedto PFHE and finally expanded in JT to providethe essential sub-cooling duty of PFHE. Bothwarm and cold streams in PFHE are closelylaying, which shows, in turn, an indication ofrelatively higher process effectiveness.


Fig. 21 shows the simulation outputs of specificenergy consumption as a function of a MRcooling reference cooling temperature and feedgas pressure. Effectiveness of process 6 reads anenhancement factor of about 16% of total energyconsumption compared to process 1.

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The results of process 7 regarding (Q/T) diagramof the cold and warm streams of PFHE (leftabscissa) as well the temperature difference(right abscissa) as a function of specific heattransfer within the PFHE is presented in Fig. 22.Obtaining a maximal temperature difference ofabout 12K on the warm end and 17K on cold endof PFHE, due to the cooling of MP MR withexpanding HP MR prior to be routed to PFHE,the other process configurations are identical tothose of process 5.

Achievements on specific energy consumptionof process 7 is shown in Fig. 23. This processrecords a further improvement in the energyconsumption of a factor of about 14%, which isnear to that of process 5 under identical MRCconfigurations.

Fig. 22: PFHE (Q/T) diagram of process 7


From the above findings, the improvements,performed for all above processes, are achievingthe best readings for process 6. These findingwill be further examined under different feed gaspressures and MR cooling referencetemperatures, moreover will be compared withprocess 7, where enormous effects of processtopology variation cause the process to besignificantly effective. Designing of PFHE withminimal temperature difference less than 2K isnot preferable due to economic reasons, hencethen a PFHE with a relatively large heat transferarea is required. By comparing between theMRC processes 1 to 5, generally process 2 isrecording the best results for the investigatedrange of minimal temperature difference of 2K.Other reasons for considering its topology hencelower process complexity as well for therelatively simplest automation scenario. So thatprocess 2 will also be considered for furtherinvestigations.

The Fig. 24 - 26 summarize the difference inspecific total consumption energy as a functionof the investigated range of feed gas pressures,for processes 2 and 7 with respect to process 6,considering similar conditions of PFHEminimum temperature of 2K and variousreference temperature refrigerant of 15, 30 and45 ºC, for simulating the diverse of metrologicalconditions for different regions around theworld. The process calculations are done forPEHE minimal temperature difference with 2K.It is obvious that the process is showing a betterperformance with lower minimal temperaturedifference on PFHE, and higher inlet feed gaspressure. More over lower specific energyconsumption is obtained with the low MRcooling reference temperature, since then lowerduty on the MRC compressor is required.

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Fig. 24: Difference in total consumptionenergy for 15 ºC as MR cooling referencetemperature

Fig. 25: Difference in total consumptionenergy for 30 ºC as MR cooling referencetemperature

Fig. 26: Difference in total consumptionenergy for MR cooling 45 ºC as referencetemperature

Process 2 and 7 are recording higher figures fordifference in total energy consumption withrespect to those of process 6. As observed fromFig. 24 the figures for process 2 decreases withfeed gas pressure. The major influencing factoron the specific energy consumption in therefrigerant condensation process is the attainableenthalpy difference, hence the more refrigerant,condensed with using the cooling water, themore energy efficient is the condensationprocess. Considering the situation in process 7, itis reading a relatively better performance due toinclusion of cold MR separator on the cold end

of PFHE. The difference for process 7 reaches amaximum around the feed gas pressure of 50 bardue to thermodynamic equilibrium betweenliquid and gas phases of MR. This could be for aprocess limitation.

The findings in Fig. 25 take a different trend thatseems to be almost identical difference for eachprocess starting from a feed gas pressure of 40bar. Meaning that the process configurations, ofMR cooling reference temperature refrigerant of30 ºC, are recording almost the same level ofspecific energy consumption. Whereas in warmmetrological regions the trend of difference intotal energy consumption is increased for bothprocesses 2 and 7, hence then higher energyconsumption figures are expected on the MRCcompressors.

Conclusion

From the above findings, it can be concludedthat the new improvements, proposed andcompared with almost exclusively commercialtrademarks processes in NG plant design, whichmainly include the design of NG liquefactionand refrigeration cycle, are achievingconsiderable energy savings as well potentiallyare reducing the capital and operating costs ofthe plants, through reducing its footprint. Theseimprovements are compatible for power-efficient, off- & onshore liquefaction plants,decreasing plant complexity scenarios fromautomation engineering point of view, as well forecological reasons. So can assembly simulationsparameters, be concerning energy density andequipment design, have the major impact oncost, or the so called benefit ratio, this is definedas the ratio between the price of the product andthe plant efficiency. These parameters areindication on the potential energy savings bymeans of integration the traditional liquefactionprocesses with the proposed improvements onthe plant layout, as well merging withoptimization of the process conditions of MRC.More investigations are required to account for amoderate scalability of the modeled processimprovements with respect to large scale plants.Furthermore, considerations for plant designwith other commercial types of cryogenic heatexchangers are meriting a further work.

References[1] Smith, J. M., Van Ness M. M. Abbott,

Introduction to Chemical EngineeringThermodynamics, 5th edition, McGRAW-HillInternational Editions 1996, ISBN 0-07-059239-X.

[2] Çengel Y.A., Boles M.A., Thermodynamics an

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engineering approach. McGraw-Hill, New York,2002.

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Glossary of abbreviationsAcronym DescriptionAPCI Air Products & Chemicals, Inc.BP British Pertoleum Corp. North America

C3MR Propane mixed refrigerantdTmin Minimal Temperature differencedpFuel Pressure drop on Fuel gas streamdp Pressure drop on MRC steamsDMR Dual mixed refrigerantJT Joule-ThomsonQiso Insulation heat lossηisen Isentropic compressor efficiencyTinlet Inlet temperatureToutlet Outlet temperaturepoutlet Outlet PressurePinlet Inlet pressureCAPEX Capital costsdpMR Mixed refrigerant stream pressure dropHP High pressureLNG Liquefied natural gas

MP Medium PressureMR Mixed refrigerantMTPA Million tonne per annumNG Natural gasMFCP Mixed fluid cascade processMRC Mixed refrigerant cyclePFHE Plate Fin Heat ExchangerPRICO Poly Refrigerant Integrated Cycle

OperationsSMR Single mixed refrigerant

Said Al Rabadi, holds a BS degree in ChemicalEngineering from Jordan University of Science &Technology - Irbid/ Jordan in 2000, a MS degree and aPhD in Process Engineering from Hamburg Universityof Technology - Hamburg/ Germany in 2002 resp.2007. Worked as Process Engineer of natural gasliquefaction plants 2008 till 2014 – Munich/ Germany.Since 2015 is an Assistant Professor at the Departmentof Chemical Engineering at Al Balqa AppliedUniversity – Huson/ Jordan. Major fields of researchare plant design, energy and environment, fluidmechanics and thermodynamics.

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