Fasaha na Ƙafofi na LNG

Matsayin Tattauna na Kafa ta LNG

Kafa ta gas na al'ada ta hana da wani fasaha na farko: yanka hanyar yin taka daga methane don ya zama mai sauƙi a cikin -162°C. Fasaha na farma ƙarfi shi ne wanda ke haɗa wannan aiki. Ba shi abu daya na alama ko wani fasaha na farko ba — shi ne wani fasaha na thermodynamics wanda ke tattara a cikin fasaha na kafa daga farko zuwa kashi.

A cikin ƙarfi, alama ta nuna gas wani tsari na yawa da kuma ta gudanar da shi a kan wani abu da ke gudanar da shi ko a kan turboexpander. Gudanar da shi ya zuba ƙananan yara, kuma wannan tsari na sanyi ya ke amfani da shi don fuskantar yara na farko. Tsarin gudanar da shi da kuma tsarin kuma yadda aka gudanar da shi ya daga baya da baya ya zuba yara na gas na farko don hana shi a matsayin LNG.

Unitin gudanar da nitrogen (NRU) shine abu mai mahimmanci wanda ke amfani da wannan hukummar. Idan gas na yanki ke cikin nitrogen wanda ba shi kyakkyawan alama na yara kuma ya taka wani ƙaramin aminci na LNG, NRU ta gudanar da shi ta amfani da distillation na yara . Alama ta amfani da gudanar da shi da kuma condensation don gudanar da nitrogen daga LNG ba ta amfani da kimiyar ba . Tsarin ya daga baya da baya yana canzawa a cikin yadda nitrogen ta gudanar da shi, daga flash na yawa don gudanar da shi zuwa tsarin gudanar da shi na mafi kyakkyawa ko tower na distillation .

Wannan yana da matukar tushen saboda gas na kudin kankara da ayyukan kafa na LNG suna da kariya mai tsoro akan karamin nitrogen. Idan ba a amfani da NRU mai karfi, LNG zai iya gaskiya a matsayin karamin kudin kankara ko masu sanya zai sanya wani abu da yawa ta hanyar meter kubewa kuma baya da yawa ne da za su iya sanya. Wadanda ne, alama na kudin kankara zai iya rarraba.

Turboexpanders vs. Joule-Thomson Valves: A Practical Trade-Off

Kudin kankara na kafin kudin kankara zai iya gaskiya ta hanyar biyu na mabobbi: Joule-Thomson valve da turboexpander. Wadannan biyu suna cire karamin kudin kankara da karamin yin kudin kankara, amma suna yi a matsayin farko, kuma azanci na sauran suna da daga cikin kudin kankara na kudin kankara.

Joule-Thomson valve ita ce babu kusur, yana da kyau, kuma ba shi da abu ne da ke kawo. Gas ya kudin kankara ta hanyar valve, kuma karamin yin kudin kankara ya cire saboda efekti na Joule-Thomson. Alama ce wadannan kudin kankara suna da isenthalpic — ba a samu wani abu daga cire karamin kudin kankara. Duk wani abu ya fara cire karamin yin kudin kankara, amma kudin kankara yana da kariya.

A turboexpander, wanda ya sa, yana ƙara aiki daga gas da ke ƙarƙashawa. Ƙarkashin yana gaba daya zuwa isentropic, wani ne mai nufin cewa ƙarin energy na pressure ta zama aiki mai mahimmanci (yanku yana ƙara compressor a sama shaft) kuma yana samun kuskurin ƙarfi. Isentropic efficiency na waɗannan units suna kashe a ƙaramin 60-70% a matsayin design da conditions na amfani. Wannan aiki da aka ƙara zai iya gudunawa wani abu da ke ƙara load daga wani compressor a train.

Wani abu da ke ƙarƙashawa shine ƙananan karami da karamin bayani. A turboexpander shine machine mai ƙananan karami da ƙananan karami na clearances, bearings na high-speed, da seals na special. Yana bukata maintenance wanda JT valve ba suka bukata ba. Don plants na ƙananan karami ko applications da ke ƙarƙashawa na pressure ta hanyar ƙananan karami, JT valve yana gaskiya a total cost of ownership. Don baseload LNG trains da ke ƙara efficiency gains da suka zama direct increase a production, turboexpander yana baiwa a lokacin da ke taka.

Inda Cryogenic Expansion ke cire a LNG Train

Tsarin kafin gudun kuma yana bayyana a cikin manya daga cikin tsarin kafin gudun LNG. Fasahar ina zai iya amsa wani abu ne da ke taimaka wajen fahimtar yadda kuma yadda tsarin ya yi amfani da shi.

Matsayin MCHE (main cryogenic heat exchanger) shine tsari na karamin halin LNG na baseload. Refrigerant — wanda a karkara yana da madaidaici ko nitrogen mai sauƙi — an sauya shi, an kafa shi, kuma an gudun shi don samun yadda kafin gudun kuma yayi shugaban MCHE. Wannan refrigerant mai kafin gudun yana sanya hanyar yadda kafin gudun daga gas na farko a cikin hanyar mai sauƙi, wanda ke nufin samun kafin gudun na methane. A yadda kafin gudun yana a turboexpander don refrigerant loop, kuma yadda kafin gudun da aka gudun shi yana canzawa a cikin exchanger.

A cikin kayan nitrogen rejection, ƙarama ta zama sababinsu na yawan ƙarfi da kuma yawan gaba, wanda ke bukata don distillation. Gas na farko ya zama kadan yawa, kuma yawa na likwidu — wanda ya zama mai tsarkiwa a methane — ya zo a ƙasa na column na distillation, amma yawa na nitrogen ta saba a sama. Reflux wanda ke taimaka a wannan fassara ya daga nitrogen da aka karama kuma aka likwidu, sannan ya rufe kuma ya bayyana kuma ya bai kuma yawan gaba.

Wani matakai na LNG plants suka yi amfani da nitrogen expander cycle, inda nitrogen ta zama abu ne da refrigerant kuma working fluid. Nitrogen ta karama, ta kula da gas na farko, ta karama a turboexpander, sannan ta amfani da ita don likwidu methane a simple heat exchanger. Cycle ta zama maki kuma ta yi aiki da kyau ga matakai na capacities wanda ba a bukata amfani da mixed refrigerant system ba.

Karin al’ada na nitrogen rejection challenges

Wani karama na fuskaka nitrogen zai dace da fatan a matsayin hanyar bayani. A yadda ake amfani da shi, shine wani daga cikin abubuwan da ke kula da gaskiya a cikin tsari na LNG.

A lokacin wani project a tsohon Kanada kusan kadan shekara zuwa dini, wani operator ya bude wani NRU na musamman da ya kasance da gas na fuskaka da 8% nitrogen. Bayanin design ya dace, alama na abubuwa suka dace, kuma EPC contractor ya samu karama mai kyau a cikin cryogenic distillation. Amma bayanan gas na fuskaka sun yi mutane a yadda sun saba da bayanan reservoir na gaba. Kullun nitrogen ya tawo zuwa 11% a wani lokaci na production.

NRU ta yi gaskiya a kara yin amfani. Karamin nitrogen da aka saba shi ya sao kofin distillation don zuba a wani abu da suka kira shi "flooding" — tsari na vapor ya dace don haka wajen yin amfani da liquid ba za a iya yin amfani da trays ba. Son bayani ne ya zuba, wanda ya haifar da mafi kyakkyawan methane da ke cire a wajen overhead vent kuma mafi kyakkyawan nitrogen da ke cire a wajen bottom product. Gwamnati ta zama da yin amfani da karamin feed rates don kara yin amfani da LNG a cikin spec, wanda ya haifar da karamin production.

Amsar ya kasance a nuna turboexpander biyu a cikin refrigeration loop kuma a raba karamin column reflux. Ya yi amfani, amma ya haifar da karamin lokacin production da aka lost da karamin capital outlay wanda ba a shigar da shi a cikin budget na farko ba.

Wani abu da aka nuna a wannan yadda ƙarfi na cryogenic expansion zai iya canzawa wajen canzawa na input. Wani contractor da ya fahimci wannan zai sanya kariya a cikin design — yin wani abu mai ƙarfi sosai, yin turndown capability, da kuma yin bypasses da suka ba da imkanin yin canzawa na ayyukan.

Kariya na Ayyukan da Kullum Zai Iya Neman

A cikin industry na LNG akwai matsaloli masu sauri a kan kariya na ayyukan, amma lambobi ba su neman wadanda suka nuna ba.

Karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (cryogenic) zai iya samun ƙarfi a cikin karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (liquefaction) idan aka sanya shi da kyau. Al’ummar suka nuna cewa karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (turboexpander) da aka sanya shi da kyau zai iya taimaka wajen ƙarfi a cikin isentropic efficiency ta hanyar 5% a gaba daga al’adu na karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (mean-line). A cikin wani al’adu na LNG train, wannan yana nufin cewa yana da damu na karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (production gains). Wani al’ummar sun nuna cewa karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (LNG production) zai iya samun 5-7% ta hanyar karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (improved expander performance).

Amma wannan lamba na da wasu kalmomi da ke nufin cewa akwai wasu alaluba. Karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (efficiency gain) ya ke taka kafin wasu alaluba na karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (operating conditions) — lamba na pressure na gaba, composition na gas, lamba na temperature na gida, kuma karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (configuration) na sauran karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (train). Karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (5% improvement) a cikin karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (expander isentropic efficiency) ba shi nufin cewa akwai karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (5% increase) a cikin karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (overall plant throughput). Damun haɗin karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (actual impact) yana ƙasa kuma yana canzawa daga wani karamin kuma yin fannin kawo wani abu da ke zama ƙarfi (installation) zuwa wani.

Wani abu ne da ake gano shi wato ƙarfi. Idan turboexpander ya kashe, yana kuma kashe refrigeration loop. A cikin single-train LNG plant, wannan yana nufin cewa dukkanin production zai kashe. Don haka, mahaullata suka yi amfani da spare rotor assemblies kuma suka hada muhimman koyaya da manufacturer. Abin da ke cikin redundancy zai kashe kuma yana bukatar a saba da shi a lifecycle economics, ba tare da first-cost comparison ne akan JT valve da turboexpander.

Me ake nufin saboda abin da aka zauna a lokacin da aka fiyadawa

Cryogenic expansion approach ne da aka zauna a lokacin da aka fiyadawa yana kuma saukarwa a cikin operating experience don 20 zuwa 30 shekara. Plant ne da aka zauna ta hanyar JT valves zai kashe kariya kuma zai kashe kadan a cikin maintenance, amma zai ci gaba da power per ton of LNG produced. Plant ne da aka zauna ta hanyar turboexpanders zai kashe kariya a cikin capital cost kuma zai kashe kadan a cikin maintenance, amma zai produce kadan a cikin LNG daga wanda aka fiyadawa.

Babu wani wannan amsa daidai na kowa. Alama na yin amfani shine ya kasance na farko da kayan aikin project — kudin kwamfutin, ƙarfin ƙarshen LNG na gaba daya, ƙarfin masu amfani da kayan aikin tattalin arziki, da kuma kudin mutum na yin amfani da kuskuren da ba su dace ba.

Wadanda suka nuna shine EPC contractor ya fahimci kadan da kadan da yake da shi da yin bayani da sahih. Wani contractor da ke sauya turboexpanders don hanyoyin project suna bukata mutumin da yin amfani. Kamar hakan, wani contractor da ke yi amfani da JT valves don hanyoyin project saboda suna da rashin kariya suna ƙara kudin da za a iya samun da shi ta hanyar ƙarfi na yin amfani.

Mafi kyakkyawan yara ne shirin da ke fito da karamin fannin da ke cikin halin da project na. Don proyekti da suka samu composition na feed wanda suka gane kamar yadda zai iya ci gaba da kuma zai daina, shirin da ke ƙarfi kuma da ke ƙarfi zai iya samun kari daidai. Don proyekti da ke da feed da ke canzawa ko don da ke da kudin kurya da ke ƙarfi, sannan zai iya samun kari daidai a cikin turboexpanders da kuma shirin da ke ƙarfi na refrigeration.

Cryogenic expansion ba teknologin da ke fito ga duk wani abu ba. Shii ne matakai na yadda za a iya amfani da shi da ke fito ga abin da aka yi. Masu amfani da shi da suka gane wannan — da masu amfani da shi da suka samu amfani da shi a hanyar amfani da shi — suna da kari daidai da ake amfani da su. Greenfir ya ba wannan nazarin da ke da amfani da fannin da ke da kari daidai ga proyekti na cryogenic gas processing, da ke taka da ASME U-stamp certification da kuma design center wanda ke da kari daidai a cikin al’amarin da ke da kari daidai a cikin industry na cryogenic equipment na watan. .