155 Full Rnge Nturl Gs Processing Heinz C. Buer Andres Bu (speker) Linde Engineering, Pullch, Germny Astrct Lrge nd untpped nturl gs reservoirs offer the opportunity to design verstile nd efficient gs processing complex. An optimized concept for the integrted production of liquid helium, liquid nitrogen, LNG (optionl), sles gs with on-spec nitrogen content, ethne, nd C 3plus will e discussed for plnt with out 49 BCM (5.1 BCF) feed gs flow rte. Introduction Virtully every inspired chemicl engineer drems out n opportunity to design complex green field nturl gs processing plnt from ottom up. This pper will tlk out such rre sitution nd the findings evolving from this process synthesis. deleted Feed Gs Amine Wsh Unit Liquefction Liquid He Wter Dryer Purifiction LIN Til Gs Methne Unit NRU Het Pump LNG Figure 1 Block Digrm of n integrted Gs Processing Plnt (igpp)
Process rrngement The overll tsk is full processing nd seprtion of lrge nturl gs strem, which rrives t the plnt site vi long distnce pipeline in dew point controlled conditions. The min products include seprted into ethne nd dditionl C 3plus frctions Sles gs with controlled nitrogen content elow 2 mol% Liquid helium grde 5.5 with 99.9995 mol% purity Other products comprise Liquid nitrogen s utility for the helium liquefier Nitrogen rich til gs (prtly used s utility, lnce to tmosphere) LNG (optionl) The plnt concept hd to e flexile with respect to feed gs composition, esy to strt-up nd operte nd lst ut not lest energy nd cost efficient. Overll pressure profile Compression systems re expensive in investment nd opertion. Thus, their use shll e minimized in clever overll concept. Idelly, the process sequence should e operle with the net ville pressure drop over the entire plnt. If, however, the BL pressure of the sles gs product is higher thn the highest possile operting pressure of ny min process step, t lest sles gs compression will e required. Now, the trget ws to identify n efficient rrngement, with which compression of the min gs strems except for sles gs cn e voided. In ddition to the pth feed gs sles gs there is nother min gs route: feed gs nitrogen/helium frction. A compression system in this second line cn e circumvented only, if nitrogen rejection is done t pressure level, which is high enough for the susequent helium clen-up nd liquefction. In nutshell, the use of so-clled doule column for nitrogen rejection would not e comptile with the desire to minimize compression steps. Eventully, the following overll concept ws selected: extrction nd methne stripping relies on feed gs work expnsion nd sles gs compression, which is the only min strem compression step Nitrogen rejection (NRU) is operted slighted elow the demethnizer pressure nd is supported y het pump system Nitrogen/helium seprtion is operted slighted elow the NRU pressure nd does not require compression except for smll recycle gs compressor
liquefction is chieved with n open loop helium cycle including work expnsion, ccordingly, there is no single compressor in the min pth etween feed gs inlet nd liquid helium product The detils of the process rrngement will e descried in the following section. For the ske of etter understnding het exchnge systems, rectifiction column rrngements nd compression trins re represented in simplified mnner. N2/He Methne Feed Gs Figure 2 nd NRU section of the integrted gs processing plnt
recovery unit (left hnd side in Figure 2) extrction nd methne stripping is sed on proven GSP 1 concept with two side reoilers (strems nd in Figure 2). High ethne recovery cn e chieved using prt of the NRU column ottoms s dditionl reflux. This feture compres in efficiency to RSV 2 design, ut voids dditionl lod to the sles gs compressor. The operting pressure of the demethnizer hs to e kept t 30 r (450 psi) or higher to estlish the correct operting conditions in the susequent NRU column. Nitrogen rejection unit / NRU (right hnd side in Figure 2) As explined ove doule column design is not desirle, s the nitrogen/helium frction would require compression upstrem of the helium purifiction nd liquefction step. Thus, well proven nd esy-to-operte single column concept hs een chosen. Insted of tking prt of the NRU column ottoms s overhed condenser refrigernt, side drw ehind prtition wll is selected s refrigernt source. This ptented 3 concept minimizes the risk of refrigernt contmintion with CO 2 or C 2plus components, which might cuse opertionl prolems in the cold end of the plnt. If the CO 2 content in the feed gs is elow certin threshold n mine system cn e voided completely. The perceived power consumption disdvntge of single column versus doule column concept is offset y the integrtion of side condenser for the NRU column, which unlods the recycle compressor significntly. The nitrogen/methne seprtion inside the NRU column is driven y het pump system (lue lines in Figure 2), in which the HP fluid is condensed in the NRU column reoiler nd vporized t two different pressure levels in the side condenser nd the overhed condenser. purifiction nd liquefction (Figure 3) The overhed product of the NRU column is still sufficiently pressured for purifiction nd finl liquefction without need for compression in the min strem (red lines in Figure 3). The process sequence in this min strem is proven rrngement of ctlytic H 2 nd CH 4 conversion, dehydrtion, cryogenic processing nd finl helium purifiction in PSA. Only the til gs of the PSA plus some minor recycle strems from the cold ox need to e recompressed. Thus the pressure energy provided y the helium frction is well utilized. The driving force contined in the pressure of the feedstock s nitrogen frction, is used in the flowing mnner: fter condensing the ulk of the nitrogen frction the nitrogen rich liquid is stripped under pressure to recover dissolved helium. The resulting pure liquid nitrogen frction (green lines in Figure 3) is vporized prtly t elevted pressure, so tht its energy cn e recovered y mens of work expnsion. The overll enthlpy lnce llows for liquid nitrogen extrction from the cold ox in sufficient quntities to stisfy the needs of the helium liquefier nd the storge tnk rdition shields.
Til Gs Air N2/He Ctlytic H2 Removl Dehydrtion Recycle Compression PSA Liquefier Wter LIN Figure 3 section of the integrted gs processing plnt LNG production (optionl) Even though the min products of the integrted gs processing plnt re s, sles gs nd helium there my e demnd for some quntities of LNG, if they cn e produced t resonle expense. An elegnt method for mrginl LNG production is drining prt of the LP refrigernt from the overhed condenser of the NRU column. This fluid (strem LNG in Figure 4) is lmost pure methne with less thn 1% nitrogen. No dditionl equipment is required. The production is limited, however, to few tons per hour, which is just good for mke-up purposes. In cse more LNG (up to 10 % of the feed gs) cn e mrketed loclly supplementry cooling systems re required. Figure 4 shows in green dotted lines tie-ins of two dditionl gs expnders, which provide refrigertion for LNG condenstion nd sucooling of prt of the NRU column ottoms (strem LNG ). In this cse the CO 2 concentrtion of the feed gs cnnot exceed 100 vppm to void freezing prolems in the sucooled LNG product.
N2/He Methne Feed Gs LNG LNG Figure 4 nd NRU section of the integrted gs processing plnt with optionl LNG extrction AMUR GPP Smrt concepts need proof of competitiveness in rel projects. This proof ws delivered end 2015, when Gzprom 4 (vi its generl contrctor NIPIgs) selected Linde Engineering 5 for the design nd supply of the min process units for the Amur GPP. The plnt is prt of Gzprom s project for the supply of Russin gs to Chin y the Power of Sieri pipeline from Estern Sierin gs fields nd will e uilt in five phses up until 2024. In lte Decemer 2015 Linde nd NIPIgs entered into inding engineering nd supply contrct in respect of the sid units for ll five construction phses of the Amur GPP. Phse one will consist of two ethne nd (propne, utne, pentne, hexne) extrction nd nitrogen rejection units s well s one helium production unit. Relted engineering works re in progress. When completed, the Amur GPP will e one of the lrgest gs processing plnts in the world with cpcity of up to 49 illion stndrd cuic meters of nturl gs per yer. It will lso include liquefied helium production lock with n nnul output of up to 60 million cuic meters (2,100 MMSCFA) the most extensive one round the gloe.
Figure 5 Mp of Gzprom s Estern Gs Progrm including Amur GPP nd helium plnt close to Belogorsk Conclusions This pper demonstrtes the technicl spects of successful synthesis of full rnge gs processing plnt. A highly ttrctive solution hd een developed while voiding technologicl step-outs. References 1 Gs Sucooled Process, US ptent 4,157,904 2 Recycle Split Vpor process, US ptent 5,568,737 3 US ptent 9,003,829 nd further ptents in other countries 4 http://www.gzprom.com/press/news/2015/octoer/rticle249177/ 5 http://www.the-linde-group.com/en/news_nd_medi/press_releses/news_20160121.html