INCREASING HYDROGEN PURITY BY ABSORPTION

Sažetak Sukladno današnjim visokim ekološkim zahtjevima, procesi hidroobrade postaju prioritetni procesi prerade nafte. To se prije svega odnosi na sadržaj sumpora u gorivima što dovodi u pitanje opstanak mnogih prerađivača nafte. To je bio i glavni razlog za izgradnju novog postrojenja za HDS/BHK težih frakcija nafte u Rafineriji nafte Rijeka. Time su količine i čistoća vodika postali vrlo bitni parametri koji utječu na optimiranje rada rafinerije. O raspoloživosti dostatne količine i čistoće vodika ovisi ne samo iskorištenje procesa nego i zadovoljenje najstrožih zahtjeva na sadržaj sumpora u produktima. U Rafineriji nafte Rijeka, kao i u mnogim drugim rafinerijama platforming proces je jedini proizvođač vodika. Čistoća vodika ovisno o procesnim parametrima u postojećim RNR platforming procesima kreće se od 65 do 75% vol. Budući da se pokazalo da je ta čistoća predstavljala znatno ograničenje za procese hidroobrade i hidrokrekinga, tražen je način za obogaćivanje ”net-separator plina” platforminga. Rafinerijskim stručnjacima već odavno su poznati procesi proizvodnje čistog vodika iz lakših i težih frakcija nafte ili prirodnog plina. Međutim, izgradnja takvih procesa zahtijeva značajna dodatna ulaganja i vrijeme. Isto tose odnosi i za izgradnju poznatih tehnoloških procesa za pročišćavanje plinova bogatih vodikom. Navedene činjenice prisilile su nas da što hitnije pronađemo optimalno rješenje unutar rafinerije. To je osim optimiranja rada platforming procesa rezultiralo i iskorištenjem dijela procesne opreme u svrhu novog načina pridobivanja vodika više čistoće u RNR. Na osnovi idejnog rješenja izrađene su teoretske, tehnološke i tehničke podloge za realizaciju procesa pridobivanja vodika više čistoće postupkom apsorpcije na koloni 17 C-1 koja je fizički u sklopu Tatoray procesa i ne koristi se više od 12 godina. Kolona 17 C-1 tehničk-tehnološki postaje apsorber na kojem se apsorbiraju lagani ugljikovodici iz ”net-separator plina” proizvedenog na platformingu 2. Kao apsorbens u našem slučaju koristimo stabilizirani i ohlađeni platformat koji ima iznimno dobre apsorpcijske karakteristike. Spajanjem kolone 17–C1 sa stabilizator kolonom platforminga 2, kolona za stabilizaciju je preuzela ulogu stripiranja apsorbiranih ugljikovodika iz apsorbensa (ohlađeni platformat) koji će se izdvajati kao suhi i tekući plin na vršnoj posudi kolone za stabilizaciju. Uključivanje kolone za kontinuiranu apsorpciju u proces platforminga 2 imalo je višestruke pozitivne učinke. 1. Postignut je glavni cilj, a to je obogaćivanje proizvedenog plina platforminga 2 na preko 83 % vol. vodika. 2. Istodobno, apsorbiranjem vrijednih ugljikovodika iz platformingovog plina (C3 i C4 ugljikovodici) značajno je povećan iscrpak tekućeg plina na samom postrojenju platforminga. 3. Čistoća plina od preko 83% vol. udjela vodika osigurala je rad i HDS i BHK postrojenja na maksimalnim kapacitetima i oštrinama, te pridobivanje optimalno kvalitetnih produkata. 4. HDS načinom rada pridobiva se na postrojenju maksimalna količina i kvaliteta plinskog ulja odnosno dizelskog goriva. 5. BHK načinom rada pridobiva se maksimalna količina i kvaliteta šarže za FCC postrojenje. Na FCC postrojenju preradom kvalitetno hidroobrađene šarže postižu se dodatni pozitivni učinci, a to su prvenstveno povećani iscrpci benzina, tekućeg plina i lakog katalitičkog ulja, na račun manje vrijednog dekantiranog ulja i suhog plina. Svi proizvodi FCC-a imaju minimalan sadržaj sumpora što se kao konačan pozitivan učinak reflektira u procesu namješavanja komercijalnih proizvoda.Abstract High environmental standards are nowadays being growingly adopted as requirements of the market and, subsequently, hydrotreating is gaining priority in oil processing. This, first of all, refers to sulphur content in fuels, which ultimately endangers the future existence of many refiners worldwide. This was the main reason for constructing the new plant for HDS/MHC of heavier oil fractions at the Rijeka Refinery. Hydrogen quantities and its purity have become a very significant parameter in optimizing the Refinery’s operation. The availability of sufficient hydrogen and its purity not only influence the level of process utilization but are also the key factor in meeting the highly severe requirements on sulphur content in oil products. In Rijeka Refinery, like in many others, the Platformer unit is the only hydrogen producing unit. The purity of hydrogen ranges from 65 to 75% vol., depending on process parameters in the existing platformers. Since hydrogen purity proved to be quite a limiting factor for hydrotreating and hydrocracking processes, the ways of enriching platformer “net-separator gas” were sought for. The Refinery experts are well acquainted with the processes for the production of pure hydrogen from light and heavy oil fractions and natural gas. However, construction of such process units would involve significant additional costs and time. The same applies to processes for purification of hydrogen-rich gases. These facts have triggered the search for the optimum solution leaning on the Refinery’s own resources. The results were not only the optimization of the Platformer unit but also the utilization of a part of the existing refinery’s process equipment for the generation of higher purity hydrogen. The conceptual design was developed and theoretical, technological and technical documents elaborated to support the realisation of the process for the production of higher purity hydrogen by means of absorption, which should take place on the 17 C-1 column. It should be mentioned that the 17 C-1 column is physically incorporated into the Tatoray process and has been out of service for some 12 years. Thus, the 17 C-1 column becomes the absorber in the technical-technological sense, absorbing light hydrocarbons from “net-separator gas” produced on Platformer 2. In our case, the absorbent is the stabilized and cooled down platformate showing high absorbing characteristics. By connecting the 17-C1 column with the Platformer 2 stabilizer, the stabilizer has taken over the role of stripping the absorbed hydrocarbons from the absorbent (cooled platformate) which is separated as dry gas and LPG at the stabilizer overhead vessel. The inclusion of the continuous absorbtion column into the Platformer 2 process has proved to have multiple favourable effects: 1. The main target has been achieved: that of upgrading the Platformer 2 gas to contain over 83% vol. of hydrogen; 2. Through absorbtion of valuable hydrocarbons from the platformer gases (C3 and C4) the LPG yields at the Platformer unit have been significantly increased; 3. The gas purity with over 83% vol. of hydrogen content has enabled us to run the HDS/MHC plant in both modes at its maximum capacity and operating severity, yielding optimum quality products; 4. The plant run in HDS mode produces the maximum quantity and quality of gas oil, i.e. of diesel fuel; 5. MHC mode generates the maximum quantity and the required quality of the FCC feed. By processing the properly hydrotreated feed, additional favourable effects are achieved. These are, first of all, increased yields of gasoline, LPG and LCO at the expense of less valuable decanted oil and dry gas. All FCC products show the minimum sulphur level which ultimately has a favourable influence on the blending of commercial products

THE IMPACT OF THE CATALYTIC REFORMING OPERATION SEVERITY ON CYCLE DURATION AND PRODUCT QUALITY AT THE RIJEKA OIL REFINERY

Sažetak Za oktanski broj reformata od 99 jedinica, smanjenje protoka sirovine s projektnih 90 m3/h na 75 m3/h ima za posljedicu sniženje Start of Run ulazne reaktorske temperature a 515,2 na 511°C uz omjer vodika nasuprot ugljikovodicima 7,3:1 i 23 bara na visokotlačnom separatoru Platforminga 2. Poznavajući maksimalne ulazne reaktorske temperature od oko 528°C za postojeći tip katalizatora na Platformingu 2, proizlazi da se time temperaturno područje iskoristivosti katalizatora povećava s 12,8 na 17,1°C. Na taj način se od 116 dana ciklusa dolazi do prihvatljivije duljine ciklusa od 198 dana. Ovakva duljina ciklusa omogućava dvije regeneracije katalizatora godišnje. Iako Platforming 2 danas radi pod reaktorskim tlakom od 21 do 24 bara, zbog sljedljivosti podataka, za proračun je uzeta konstantna vrijednost tlaka recirkulirajućeg plina. Ne treba zaboraviti da svaka promjena u sastavu sirovine može uzrokovati nepredvidive promjene volumne koncentracije vodika u recirkulirajućem plinu odnosno varijacije u računsko određenoj vrijednosti trajanja ciklusa reforming katalizatora. Duljina ciklusa od približno godinu dana a oktanskom vrijednošću reformata od 99 jedinica mogla bi se postići spuštanjem kapaciteta svježe šarže ispod 65 m3/h. Proces katalitičkog reformiranja na postrojenju Platforming 2 u RNR bi s kapacitetom od 62,5 m3/h svježe sirovine, omjerom H2/HC>9 omogućio duljinu ciklusa katalizatora od 357 dana.Abstract For the reformate octane number of 99 the reduction of charge from the designed 90 m3/h to 75 m3/h results in the lowering of the Start of Run inlet reactor temperature from 515.2 to 511°C with a hydrogen/hydrocarbons share of 7.3:1 and 23 bar at the high pressure separator. Knowing the maximal inlet reactor temperatures at Platforming 2 of around 528°C for the existing catalyst type, it turns out that the temperature range of catalyst usability goes up from 12.8 to 17.1°C. In this way, from 116 cycle days we come to a more acceptable cycle length of 198 days. Such cycle length enables two catalyst regenerations per year. Although Platforming 2 today operates under reactor pressure from 21 to 24 bar, in order to be able to keep track of the data, for calculation presentation in Tables 1 and 2 we have taken a constant value of the recycle gas pressure. We should not forget that every change in charge composition may cause impredictable changes of the volumetric hydrogen concentration in the recycle gas i.e. variations in the calculated reforming catalyst life value. Cycle duration of approximately one year with the reformate octane value of 99 units could be reached by the fresh charge capacity lowering below 65 m3/h. The catalytic reforming process at the Platforming 2 plant at Rijeka Oil Refinery would, with the capacity of 62.5 m3/h of fresh charge, and a H2/HC ratio >9, enable the catalyst cycle length of 357 days

ISOMERIZATION OF n-HEXANE ON Pt/SO4-ZrO2 CATALYST

Izomerizacija C5/C6 ugljikovodika je proces blagog reformiranja koji se koristi za dobivanje motornih benzina visokog oktanskog broja. Cirkonijev sulfat je predstavnik nove generacije katalizatora u procesu izomerizacije, koji ima svojstva visoke učinkovitosti, te je ekološki prihvatljiviji od dosadašnjeg komercijalnog katalizatora kloriranog aluminijevog oksida. U svrhu istraživanja procesa izomerizacije n-heksana uz cirkonij-sulfatni katalizator (Pt/SO4-ZrO2) dizajnirana je aparatura za provođenje procesa izomerizacije lakih ugljikovodika u prisutnosti vodika. Provođenjem niza eksperimenata i određivanjem pet ključnih komponenti: n-heksana, 2-metilpentana, 3-metilpentana 2,2-dimetil-butana i 2,3-dimetilbutana, kao i produkata krekiranja, opisan je utjecaj temperature i prostorne brzine na sastav produkata procesa izomerizacije. Dobiveni rezultati pokazuju porast konverzije n-heksana s porastom temperature i smanjenjem prostorne brzine u ispitivanom području vrijednosti, uz istovremeni rast udjela nepoželjnih reakcija krekiranja.C5/C6 hydrocarbon isomerization is a mild reforming process, which is used to obtain gasoline with high octane number. Zirconium sulfate catalyst is a representative of a new generation of catalysts in the isomerization process, which has properties of high efficiency and is environmentally more acceptable than the current commercial chlorinated aluminum oxide. In order to study isomerization process on the zirconium sulfate catalyst (Pt/SO4-ZrO2), laboratory apparatus for the isomerization process of light hydrocarbons in the presence of hydrogen is designed. By conducting a series of experiments and analysis of five key components: n-hexane, 2-methylpentane, 3-methylpentane and 2,2- and 2,3-dimethylbutanes, as well as cracking products, the impact of temperature and space velocity on the product composition of the isomerization process of n-hexane on zirconium-sulfate catalyst is described and explained. Obtained results show n-hexane conversion increase with the temperature increase and space velocity decrease in the investigated range of values, but is accompanied with the unwanted cracking reactions increase

THE POSSIBILITIES OF ADVANCING ISOMERIZATION PROCESS THROUGH CONTINUOUS OPTIMIZATION

Sažetak Proces izomerizacije jedan je od ključnih procesa prerade nafte u proizvodnji motornih benzina zadane kvalitete, pa je cilj svake rafinerije njegova maksimalna iskoristivost. U tu se svrhu provode unapređenja procesa uvođenjem novih jedinica kao što su pretfrakcionacija sirovine izdvanjem izopentana u koloni deizopentanizera, te separacija produkata izomerizacije primjenom molekulskih sita ili kolone za frakcionaciju. Daljnja unapređenja procesa temelje se na kontinuiranom optimiranju u stvarnom vremenu, koje omogućava svladavanje i minimizaciju utjecaja uskih grla procesa, te maksimizaciju iskoristivosti kapaciteta. Postavljeni su matematički modeli s ciljem iznalaženja optimalnih radnih uvjeta, a istražene su mogućnosti primjene kontinuiranog optimiranja u stvarnom vremenu, s naglaskom na primjenu u rafinerijskoj proizvodnji.Abstract The process of isomerization is one among the key processes of oil generation in the production of motor gasoline of a given quality, and so, it is the purpose of every refinery for the process to be used to the fullest. To this end, there have been process advancements through the introduction of new units, such as feed prefractionation in deisopentanizer column, and separation of isomerization products through the application of molecular sieves or fractionation column. Further process advancements are based on a continuos optimization in real time, enabling the mastering and minimization of the impact of process bottlenecks, as well as maximum capacity use. Mathematical models have been set up consisting of both dependent and independent values, for the purpose of exploring optimal working conditions, while the paper explores the possibilities of a continuous optimization in real time, the stress being on field application

INFLUENCE OF BENZENE ON THE PROCESS OF n-HEXANE ISOMERIZATION ON Pt/SO42-/ZrO2 CATALYST

Izomerizacijom n-heksana dobivaju se izomeri s visokim vrijednostima oktanskog broja koji se, kao ekološki prihvatljive komponente, koriste za namješavnje motornih benzinskih goriva. Jedan od modernih katalizatora koji se koristi u rafinerijskim procesima izomerizacije je Pt/SO42-/ZrO2 katalizator čija katalitička aktivnost ovisi o sastavu sirovine i procesnim uvjetima u sustavu. Povećana potražnja za derivatima nafte u posljednjih nekoliko godina dovodi do potrebe za obradom sirovine manje kvalitete, sa sadržajem spojeva koji negativno utječu na kinetiku i termodinamiku procesa. U ovom radu je proučavan utjecaj sadržaja benzena na proces izomerizacije n-heksana. Kao sirovina za proces pripravljane su otopine benzena u n-heksanu u masenom udjelu od 1, 2, 3 i 4 %. Temperaturni raspon u kojem su vođena ispitivanja je 130-170 °C. Kao dodatni parametri čijom se promjenom pratila učinkovitost procesa bili su omjer vodika kao plina nosioca i sirovine, te prostorna brzina protoka sirovine, odnosno volumni protok sirovine po volumenu katalizatora (eng. LHSV). Dobiveni rezultati ukazuju na smanjenje konverzije n-heksana s povećanjem udjela benzena u sirovini, poglavito pri nižim temperaturama i višim vrijednostima prostornih brzina i omjera vodika i sirovine.Isomerization of n-hexane is a process that produces high octane value isomers, which are ecologically acceptable components for blending of motor fuels. One of the latest generation isomerization catalysts is Pt/SO42-/ZrO2 catalyst, whose activity depends on feed properties and process parameters. Increased demand for petroleum products in last few years lead to the need for processing feeds of decreased quality, containing compounds that negatively affect the kinetics as well as thermo-dynamics of the process. In this paper we studied the effect of benzene on the isomerization process of n-hexane. Solutions of benzene in n-hexane were used as feed, with benzene contents of 1, 2, 3 and 4 wt.%. The temperature range in which tests were conducted was 130-170 °C. Additional process parameters which were used to control process efficiency are hydrogen to hydrocarbon ratio and liquid hourly space velocity (LHSV). The results indicate a decrease in conversion of n-hexane with increasing benzene content in the feed, especially at lower temperatures and higher values of space velocity and the hydrogen to hydrocarbon ratio