The history of crude oil desalting/dehydration plant (DDP) has been marked in progressive phases-the simple gravity settling phase, the chemical treatment phase, the electrical enhancement phase and the dilution water phase. In recent times, the proper cachet would be the control-optimisation phase marked by terms such as "DDP process control", "desalter optimisation control" or "DDP automating technology". Another less perceptible aspect, but nonetheless important, has been both a punch listing of traditional plant boundaries and a grouping of factors that play the essential roles in a desalting/dehydration plant (DDP). Nowadays, modelling and optimising of a DDP performance has become more apparent in petroleum and chemical engineering, which has been traditionally concerned with production and refinery processing industries. Today's desalting/dehydration technology finds itself as an important factor in such diverse areas as petroleum engineering, environmental concerns, and advanced technology materials. The movement into these areas has created a need not only for sources useful for professionals but also for gathering relevant information essential in improving product quality and its impact on health, safety and environmental (HSE) aspects. All of the foregoing, clearly establishes the need for a comprehensive knowledge of DDP and emulsion theories, process modelling and optimisation techniques. The main objective of this work is to model and qualitatively optimise a desalting/dehydration plant. In due course, the contents of this thesis will cover in depth both the basic areas of emulsion treatment fundamentals, modelling desalting/dehydration processes and optimising the performance of desalting plants. In addition, emphasis is also placed on more advanced topics such as optimisation technology and process modifications. At the results and recommendation stage, the theme of this work-optimising desalting/dehydration plant will practically be furnished in an applicable scheme. Finally, a significant compendium of figures and experimental data are presented. This thesis, therefore, essentially presents the research and important principles of desalting/dehydration systems. It also gives the oil industry a wide breadth of important information presented in a concise and focused manner. In search of data quality and product on-line-improvement, this combination will be a powerful tool for operators and professionals in a decision support environment.

<p><strong>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</strong></p><p>Ispitana je ekstrakcija timijana (<em>Thymus vulgaris L.</em>) primenom ugljendioksida u superkritičnom stanju kao ekstragensa. Razrađen je postupak tečne hromatografije pod visokim pritiskom (HPLC) za određivanje farmakolo&scaron;ki aktivnih fenolnih jedinjenja, timola i karvakrola, koji obezbeđuje visok stepen reproduktivnosti određivanja (za timol K_w = 1,29%). Za kvalitativnu i kvantitativnu analizu proizvoda na bazi timijana, etarskog ulja i ekstrakata, primenjen je metod gasne hromatografije (GC) sa masenom spektrometrijom (MS). Sadržaj etarskog ulja određen oficinalnim postupkom koji propisuje jugoslovenska farmakopeja iznosi 1,75% (V/m). Dominantna komponenta etarskog ulja timijana je timol čiji je sadržaj 50,06% (m/m), dok je karvakrol prisutan, praktično, u tragovima (1,15%). Od prisutnih parafina u etarskom ulju, največi sadržaj ima n-tetradekan (16,11%). U totalnom ekstraktu timijana dobijenom metilen- hloridom primenom ekstrakcije sa povremenim ispu&scaron;tanjem ekstrakta (Ekstrakcija po Soxhlet-u), koji je dobijen u prinosu 4,95% (m/m), dominantna komponenta je n-tetradekan (47,18%), dok je sadržaj timola 16,11%.<br />Kinetika ekstrakcije timola se može uspe&scaron;no predstaviti analogno izrazu za kinetiku reakcije prvog reda, primenom koje se dobija največa vrednost konstante brzine ekstrakcije (k) 0,2209 h^-1 za selektovani protok superkritičnog ugijendioksida 97,725 dm³/h.<br />Primenom timijana stepena usitnjenosti d₂ srednjeg prečnika 0,35 mm za ekstrakciju superkritičnim ugijendioksidom (100 bar; 40&deg;C; 2,5 sata) postiže se kvantitativna ekstrakcije prisutnog etarskog ulja. Po svom sastavu ovaj ekstrakt je najsličniji etarskom ulju timijana dobijenom destliacijom pomoću vodene pare. Produžavanje vremena ekstrakcije iznad 2,5 sata ima za posledicu povećani prinos, pre svega, parafina.<br />Primenom ugljendioksida male moći rastvaranja (80 bar; 40⁰C;&nbsp; d=0,1918 g/cm³) ne postiže se kvantitativna ekstrakcija etarskog ulja. Povećavanjem radnog pritiska od 100 do 400 bar, usled povećanja moći rastvaranja, dobijaju se ekstrakti koji su po svom sastavu sve sličniji totalnom ekstraktu dobijenom ekstrakcijom metilenhloridom.<br />Za modelovanje ekstrakcionog sistema timijan - superkritični ugljendioksid je primenjena jednačina Reverchon-a i Sesti Osseo-a:<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Y = 100 [1-exp(-t/t_i)]<br />gde je: Y - normalizovani ekstrakcioni prinos (%); t - vreme ekstrakcije (s) i t_i -&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; vreme unutra&scaron;nje difuzije (s)<br />odnosno njen modifikovani oblik:<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Y = 100 [1 - ehr (at + b)]<br />Izračunate vrednosti standardne gre&scaron;ke regresije (S_Y,X) ukazuju da u osnovi modifikovana jednačina bolje fituje normalizovane prinose kako totalnog ekstrakta, tako i timola, u odnosu na polaznu jednačinu.<br />Jednačine:<br />&nbsp;&nbsp; log S = a m_rel + b<br />i<br />&nbsp;&nbsp; log S = a <em>d</em>_C02 + b<br />gde je: S - rastvorljivost totalnog ekstrakta (g/dm³), odnosno timola (mg/dm ) u ugljendioksidu; m_rel - relativna masa ugljendioksida (g CO2/g timijana) i <em>d</em>_CO2 zapreminska masa ugljendioksida (g/cm³)<br />se mogu, takođe, uspe&scaron;no primeniti za modelovanje ekstrakcije ispitivanog sistema.<br />Primenom ugljendioksida u tečnom stanju (65 bar; 23&deg;C) se dobija ekstrakt timijana sličan po svom sastavu ekstraktu dobijenom ekstrakcijom superkritičnim ekstragensom na pritisku 100 bar.<br />U cilju dobijanja ekstrakta timijana koji je po svom kvalitativnom i kvantitativnom sastavu najsličniji etarskom ulju dobijenom oficinalnim postupkom destilacije pomoću vodene pare, neophodno je za ekstrakciju koristiti ugljendioksid zapreminske mase 0,6302 g/cm³( 100 bar;40&deg;C), biljni materijal stepena usitnjenosti d₂, vreme ekstrakcije 2,5 sata i protok ekstragensa 97,725 dm³/h.</p> / <p><strong>Abstract was processed by technology for Optical character recognition (OCR).</strong></p><p>The extraction of thyme (Thymus vulgaris L.) by supercritical carbon dioxide as an extragent was investigated. The developed HPLC (High Pressure Liquid Chromatography) method for determination of pharmacologically active phenolic compounds, thymol and carvacrol, showed a high reproducibility (Kw for thymol 1.29%). Qualitative and quantitative analyses of thyme products, essential oil and extracts, were carried out by gas chromatography - mass spectrometry (GC-MS). The content of essential oil determined by an official procedure given by Yugoslav pharmacopoeia was 1.75% (V/w). The predominant compound of the essential oil is thymol (50.06%; w/w), while carvacrol is present, practically, in traces (1.15%; w/w). The content of n-tetradecane in the thyme essential oil (16.11%; w/w) is higher than that of other paraffins. In the total thyme extract obtained by methylene chloride using extraction with periodical exchange of the extract (Soxhlet extraction) in a yield of 4.95%(w/w), the predominant compound was n-tetradecane (47.18%), while the content of thymol was 16.11%.</p><p>The extraction kinetic of thymol can be successfully expressed by analogy to first order reaction kinetic, and a highest value of extraction rate constant (k) of 0.2209 h-1 for the selected flow rate of supercritical carbon dioxide of 97.725 dm3/h.<br />A quantitative extraction of thyme essential oil by supercritical carbon dioxide (100 bar; 40&deg;C; 2.5hours) was obtained using thyme of the grinding degree d2 (mean particle diameter 0.35 mm). The composition of this extract is very similar to that of the essential oil obtained by steam distillation. A higher yield of extraction, primarily of paraffins, was obtained by prolonging the extraction time over 2.5 hours. The use of carbon dioxide of low solubility power (80 bar; 400C; d =0.1918 g/cm3) did not yield a quantitative extraction of thyme essential oil.<br />Ву increasing extraction pressure from 100 to 400 bar, i.e. solubility power, the extract composition was more and more similar to the composition of total extract obtained by methylene chloride.<br />То model extraction of the system thyme - supercritical carbon dioxide use was made of the Reverchon - Sesti Osseo equation:</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Y = 100 [1-exp(-t/ti)]</p><p>where: Y - normalized extraction yield (%); t - extraction time (s) and ti - internal diffusion time (s)<br />i.e. of its modified form:<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Y = 100 [1 - ехр (at + b)]<br />The calculated values of standard error of regression (SY,X) show that the modified equation is generally a better fit for the normalized yields of total extract and thymol compared to the original equation.<br />Equations:</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; log S = a mrel + b<br />and<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; log S = a dC02 + b<br />where: S - solubility of total extract (g/dm3), i.e. of thymol (mg/dm3) in carbon dioxide; mrel - relative mass of carbon dioxide (g CO2/g thyme) and dCO2 carbon dioxide density (g/cm3)</p><p>could be successfully used for modelling of the investigated extraction system.<br />The composition of thyme extract obtained by liquid carbon dioxide (65 bar; 23&deg;C ) is very similar to that obtained by supercritical extragent at a pressure of 100 bar.<br />То obtain a thyme extract whose qualitative and quantitative characteristics are most similar to those of the essential oil obtained using official procedure by steam distillation, it is necessary to use a carbon dioxide density of 0.6302 g/cm3 (100 bar; 400C), grinding degree of thyme d2, extraction time of 2.5 hours and extragent flow rate of 97.725 dm3/h.</p>