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V doktorski disertaciji sta predstavljeni dve zamisli o možnosti uporabe obnovljivih surovin za proizvodnjo metanola. Prva zamisel obravnava souporabo bioplina in zemeljskega plina v obstoječem postroju za proizvodnjo metanola, kjer se sintezni plin proizvaja iz zemeljskega plina s parnim reformerjem. V ta namen smo vpeljali postrojenje za komprimiranje bioplina in izbrali najprimernejšo tehnologijo za odstranjevanje vodikovega sulfida. Za dosego zastavljenega cilja smo simulirali proizvodnjo metanola iz zemeljskega plina v obstoječi tovarni. V nadaljevanju smo delež zemeljskega plina zamenjali z bioplinom ter izvedli analizo občutljivosti z variiranjem razmerja med bioplinom in zemeljskim plinom. Predstavljena zamisel je bila ekonomsko ovrednotena. Rezultati analize so pokazali, da je zamenjava deleža zemeljskega plina z bioplinom smiselna, kar dokazujeta visok prihranek in relativno kratek vračilni rok v investicijo postrojenja za uporabo bioplina v proizvodnji metanola. Druga zamisel obravnava souplinjanje toreficirane biomase in premoga. V prvi fazi smo v programu Aspen Plus načrtovali proizvodnjo metanola iz premoga. Simulacija vključuje, sušenje in uplinjanje premoga, odstranjevanje vodikovega sulfida iz sinteznega plina s procesom Rectisol, reakcijo sinteznega plina z vodno paro, odstranitev ogljikovega dioksida iz sinteznega plina in proizvodnjo metanola. V nadaljevanju smo isti model uporabili za souplinjanje toreficirane biomase in premoga v razmerju 1 : 1 glede na kurilnostobeh surovin. Oba procesa smo toplotno integrirali v programu Aspen Energy Analyzer. Proizvedeno paro smo nato uporabili v simulaciji tristopenjske parne turbine za proizvodnjo električne energije. Oba procesa smo primerjali v smislu tehnološkega izkoristka in ekonomske učinkovitosti z metodo neto sedanje vrednosti in interne stopnje donosa, upoštevajoč predvidene cene surovin in produktov. Tehnološki izkoristek je v primeru uplinjanja premoga znašal 70 %, v primeru souplinjanja premoga in toreficirane biomase pa 69,2 %, kar pripisujemo nižji vsebnosti ogljika v biomasi. Izkazalo se je, da je proces proizvodnje metanola, pri katerem uporabljamo samo premog, ekonomsko učinkovitejši. Analize občutljivosti pokažejo, da bi se morala cena biomase znižati vsaj za 20 % ali pa bi morala biti cena takse CO2 višja za 60 %, da bi bila oba procesa ekonomsko primerljiva. This doctoral dissertation presents two ideas regarding the uses of renewable raw materials for the production of methanol. The first idea deals with usage of biogas and natural gas mixtures within the existing plant for the production of methanol, which is based on the steam reforming. The compressor equipment was designed and the technology for the desulphurisation of the biogas chosen. An existing methanol plant that uses natural gas was modelled in Aspen Plus. In the next step the same model was used to simulate the production of methanol from a mixture of biogas and natural gas. Sensitivity analyses were performed by varying the ratio between biogas and natural gas. The results showed that replacing a part of the natural gas with biogas is reasonable, as evidenced by substantial savings and a relatively short payback period for the designed equipment. The second idea deals with the co-gasification of torrefied biomass and coal. Firstly simulation of the production of methanol from coal was modelled in Aspen Plus. Simulation includes the drying and gasification of coal, desulphurisation of synthesis gas, water-gas shift reaction, removal of CO2 from synthesis gas, and the production of methanol. Furthermore, the same model was used for the gasification of a mixture of torrefied biomass and coal with a ratio of 1:1 in relation to the heating value. Both processes were thermally integrated using Aspen Energy Analyser. The produced steam was then used within a simulated triple-stage steam turbine in order to produce electricity. Both processes were compared in terms of technological efficiency and economic feasibility using the net present value and internal return rate. The predicted prices were taken into account for the raw materials and products. Technological efficiency amounted to 70%, for the coal gasification case and 69.2%, for the co-gasification of biomass and coal respectively. It was shown that the coal-only case would perform slightly better in terms of economics than the co-gasification case. Sensitivity analyses showed that if the price of biomass were to decrease by 20% or the CO2 allowance price were to increase by 60%, both processes would be economically comparable.

Economically viable process designs should be, in addition to other criteria, profitable over their entire process lifetimes not only at the present time. An improved process design can be achieved by establishing an appropriate trade-off between product income, raw material, operating costs, and investment. The full lifetime of the processes and future prices have to be considered rather than optimising them on a yearly basis using current prices. Single-period optimisation and synthesis models for processes reflects current prices only. The prices can fluctuate rather quickly and the optimal solution may be very different from one year to the another. Therefore, the traditional superstructural synthesis approach applying a mixed-integer nonlinear programming model was upgraded: i) over time, by considering an entire lifetime, which can be described by a multi-period model and ii) the whole field of variation regarding uncertain future prices. A stochastic approach considering the statistical distribution of price projections over an entire lifetime was used on different case studies instead of the traditional deterministic approach accounting for nominal future price projection. The objective was the maximisation of the expected net present value of a process or the expected incremental net present value of different process subsystem. The heat exchanger network has been one of the subsystem, which can significantly contribute to operating costs due to savings of external utility consumption. For this subsystem a deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) synthesis models have been developed in order to account for future price projections. Considering higher energy prices gives rise to larger initial investments compared to solutions obtained with current prices. However, due to the uncertainties of utility prices' forecasts, retrofitting using an extension of HEN during future years of the lifespan might be a better strategy. The objective is to identify a design that is the most suitable for effective future extensions and preferably with the lowest sensitivity to energy price fluctuations, as there can be various designs featuring similar initial investment. The results supports that it is economically beneficial to consider future utility prices as the incremental investment is not only paid-off but additional savings are achieved. Process-to-process Heat Integration can also significantly affect the trade-off between investment and operating cost. The aim of Total Site (TS) HEN synthesis was to develop a model synthesis for the TS that, besides many other important features, would also consider future utility prices. Two strategies for TS synthesis have been developed: i) sequential, when HI is performed within a process during the first step and then after a process-to-process HI has been performed, and ii) simultaneous, where the HI is performed within and between processes simultaneously. The second strategy can reveal additional opportunities for heat recovery that might not be identified when applying the first strategy. Comparison of the results obtained at consideration of current utility prices and forecasted utility prices indicates that is worth to account for future utility prices. The separation processes also consume a significant amount of energy. The synthesis of a distillation column sequence integrated within its heat exchanger network was used as a case study for the separation of a multi-component stream into pure component products by considering future utility prices. This analysis has been performed in order to evaluate the magnitude of the influence of forecasted utility prices. It can be concluded that forecasted utility prices can be beneficial, however, the technical limits of the systems should be carefully observed. The price fluctuation can also be observed for other prices not only utility prices, e.g. raw material cost, product price, etc Ekonomično upravičeni načrti morajo biti, poleg ostalih kriterijev, tudi dobičkonosni skozi celotno življenjsko dobo procesa, ne samo v sedanjem času. Z vzpostavitvijo primernega trženja med prihodki produkta, stroški surovin, obratovalnimi stroški in investicijo v celotni življenski dobi lahko dosegamo izboljšan načrt procesa. Zato je optimizacija za celotno življenjsko dobo procesa z upoštevanjem napovedanih cen primernejša od optimizacije na letni osnovi. Enoperiodno optimiranje in sinteza za procese odraža le sedanje cene. Optimalna rešitev, dosežena za eno leto, se lahko znatno razlikuje od rešitve za drugo leto, saj se cene spreminjajo precej hitro. Običajni superstrukturni sintezni pristop z uporabo mešano-celoštevilskega nelinearnega programiranja smo zato nadgradili 1) z upoštevanjem celotne življenjske dobe, kar lahko opišemo z večperiodnim modelom in 2) z območjem spreminjanja negotovih prihodnjih cen. Namesto običajnega determinističnega pristopa pri nominalnih projekcijah prihodnjih cen smo uporabili stohastični pristop z upoštevanjem statistične porazdelitve napovedovanja cen za celotno življenjsko dobo. Namen je bil maksimiranje pričakovane neto sedanje vrednosti procesa oz. pričakovane inkrementalne neto sedanje vrednosti izboljšave različnih procesnih podsistemov. Podsistem, ki znatno prispeva k obratovalnim stroškom zaradi prihrankov pri porabi zunanjih pogonskih sredstev, je omrežje toplotnih prenosnikov. Za sintezo tega podsistema smo razvili tako deterministični kot stohastični večperiodni celoštevilski nelinearni programirni (MINLP) model ob upoštevanju prihodnjih cenovnih projekcij. Z upoštevanjem višjih cen energentov se povečajo začetne investicije v primerjavi z rešitvami, ki jim dosežemo pri sedanjih cenah. Zaradi negotovosti napovedovanja cen se je smiselno povečanju začetne investicije izogniti z načrtovanjem možnosti razširitve omrežja toplotnih prenosnikov v kasnejšem obdobju. Namen je doseči načrt, ki je kar najbolj primeren za učinkovito razširitev v prihodnosti, po možnosti z najmanjšo občutljivostjo na spreminjanje cen. Toplotna integracija med različnimi procesi lahko tudi znatno vpliva na trženje med investicijo in obratovalnimi stroški. Tako je bil eden od ciljev sinteze omrežja toplotnih prenosnikov prav upoštevanje prihodnjih cen pogonskih sredstev. Razvili smo dve strategiji za sintezo celotnega območja (ang. Total Site), in sicer: i) zaporedno, pri kateri toplotno integracijo izvajamo najprej na nivoju procesa in potem na nivoju celotnega območja, in ii) sočasno, pri kateri izvajamo toplotno integracijo na nivoju procesa in na nivoju celotnega območja hkrati. Slednja strategija omogoča dodatne možnosti prihranka toplote, kar potrjuje primerjava rezultatov doseženih pri sedanjih in prihodnjih cenah pogonskih sredstev. Separacijski procesi so lahko veliki porabniki energije. Sintezo zaporedja destilacijskih kolon integriranih z lastnim omrežjem toplotnih prenosnikov smo uporabili kot študijski primer za ločevanje večkomponentnega toka v čiste produkte. Analizo smo izvedli tudi z namenom določitve obsega vpliva napovedanih prihodnjih cen pogonskih sredstev. Zaključimo lahko, da z upoštevanjem napovedanih cen lahko dosegamo ekonomsko učinkovitejše procese ali procesne podsisteme, vendar je pri tem potrebno skrbno upoštevati tehnološke omejitve študiranega sistema. Nihanje cen razen pri pogonskih lahko opazimo tudi pri drugih cenah, npr. pri cenah surovin, in produktov. Pričakujemo lahko, da trženje v postopku optimiranja poskuša kompenzirati ta nihanja cen, npr. višje cene pogonskih sredstev bodo izravnane s povečanjem investicije, s čemer se zmanjšajo prihodnji obratovalni stroški. Vendar, ko upoštevamo vse stroške in prihodke hkrati, so lahko trendi vplivov različni od posameznega vpliva le teh, kar smo pokazali tudi s študijskim primerom.

Cilj diplomske naloge je predstavitev dveh tehnološko zahtevnih tehnologij procesa sinteze metanola in tehnologije procesa sinteze bencina. Pri obeh predstavljenih procesih sinteze metanola se je z namenom recikliranja ogljika kot osnovno surovino uporabilo stehiometrijsko določeno razmerje zmesi ogljikovega dioksida in vodika, za sintezo bencina pa se je uporabil proizvedeni metanol. Prva tehnologija proizvodnje metanola je direktna sinteza iz ogljikovega dioksida in vodika, med tem ko ima drugi sintezni postopek dve fazi. V prvi fazi se ogljikov dioksid delno presnovi v ogljikov monoksid (RWGS reakcija), nato se v drugi fazi proizvaja metanol. Izvedena je tudi ekonomska, energetska in tehnološka primerjava obeh procesov proizvodnje metanola. Pri simulaciji obeh sinteznih postopkov s programskim paketom Aspen Plus je bilo upoštevanih nekaj računskih modelov in predpostavk. V drugem delu diplomske naloge pa je predstavljen postopek sinteze bencina iz metanola. Proces sinteze bencina iz metanola je znan kot MTG proces, za katerega je izvedena tudi analiza ekonomske in energetske učinkovitosti. The aim of this diploma work is to present two technologically advanced technologies for methanol production, and one technology for gasoline production. With the aim of carbon recycling the stoichiometric ratio of CO2 and H2 was used as the raw material in both of the discussed processes for the production of methanol. The produced methanol was further used for the production of gasoline. The first methanol production technology includes direct synthesis of methanol from CO2 and H2, meanwhile the second production technology has two steps. During the first step CO2 is partially converted into CO via RWGS reaction, and methanol is produced during the second step. A comparison between these two methods was made in terms of economic, technological, and energy-efficiency bases. Some computational models and assumptions were taken into consideration for the simulation of both production processes using Aspen Plus program package. The gasoline synthesis process, using methanol as starting raw material is presented in the second part of the diploma work. The process is known as MTG process. Furthermore, the energy-efficiency and economic analysis was also done for this process.

V diplomski nalogi smo naredili raziskavo procesa proizvodnje metanola z uvajanjem CO2 v proces. Raziskava je bila narejena za družbo Nafta Petrochem d. o. o. Proces proizvodnje smo simulirali s procesnim simulatorjem ASPEN PLUS. Na proizvodnjo metanola smo vplivali z zmanjševanjem vtoka zemeljskega plina ter z dodajanjem CO2 v proces. Določili smo tudi matematični model z linearno regresijo, vpliv zemeljskega plina na proizvodnjo metanola in vpliv dodatnega vtoka CO2 na dodatno proizvodnjo metanola. Vse modele smo vključili v optimizacijski model GAMS. S podrobno analizo vseh zbranih podatkov smo preučili in ugotovili, katero razmerje med vtokom zemeljskega plina ter dodanim CO2 v proces je najoptimalnejše za proizvodnjo metanola. In this diploma thesis we have researched the methanol production process with the introduction of CO2 into the process. The research was made for the Nafta Petrochem d.o.o. company. The production process was simulated with the ASPEN PLUS process simulator. We affected the methanol production by reducing the flow of natural gas and by adding CO2 into the process. We have also defined a mathematical model using linear regression, the impact of natural gas on the methanol production and the impact of an additional flow of CO2 on the additional methanol production. All models have been included in a GAMS optimization model. With detailed analysis of all collected data we have examined and determined the ratio between the flow of natural gas and the added CO2 into the process, and which is the most optimal for the methanol production.