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Analysis of chosen aspects of a tank gassing-up process on board liquefied petroleum gas carrier. Part II

Wieczorek Agnieszka

Archives of Thermodynamics

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2021

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Vol. 42, no 2

59--69

EN

The paper presents a thermodynamic analysis of the removal of an inert gas from the tank using the vapor of liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose a thermodynamic model was created which considers two extreme cases of this process. The first is ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is the complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. On the example of nitrogen as inert gas and ethylene as a cargo, by thermodynamic analysis an attempt was made to determine the technical parameters of the process, i.e., pressure in the tank, temperature, time at which the operation would be carried out in an optimal way, minimizing the loss of cargo used for gassing-up. Calculations made it possible to determine the amount of ethylene used to complete the operation and its loss incurred as a result of total mixing of both gases.

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An experimental gassing-up operation on an ethylene carrier using two cascades with two tanks each

Wieczorek Agnieszka, Nanowski Dariusz

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2020

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nr 61 (133)

136--140

EN

Ethylene is one of the basic raw materials of the petrochemical industry that is used to produce plastics. One of the largest producers of this compound is the USA, and a substantial increase in the demand for ethylene has also been recently observed in the Middle East, the Far East, and China. This requires the transport of this cargo by sea. Ethylene carriers are a type of LPG ships and are equipped with a cascade cycle that uses propylene or refrigerant R404A as a coolant medium. These vessels have been designed to withstand the minimum temperature of ethylene of –104°C for fully-cooled cargo. A mixture of ethylene and air (from concentrations of 2.75–2.6%) becomes explosive during heating under elevated pressures. Hence, it is necessary to form an inert atmosphere in the tanks using mostly nitrogen before the ethylene cargo is loaded. The process of aerating, inerting, gassing-up, and cooling cargo tanks and cargo is constantly repeated during the operation of LPG carriers. Due to the large amounts of ethylene lost during gassing-up, which results in significant financial losses and disruptions in cargo compressors during the cooling of the tanks and cargo, this operation is the most problematic of all. In this article, a solution is proposed for performing the gassing-up procedure which prevents excessive ethylene loss.

3

An experimental ethylene carrier gassing-up operation

Wieczorek Agnieszka

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2020

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nr 62 (134)

43--48

EN

Gas carriers are one of the most advanced types of ships and are equipped with the latest technological achievements. Due to the development of this industry, the demand for ethylene transport by sea has increased significantly in recent years. Nonetheless, it is one of the most problematic loads in terms of loading operations. Due to the small density differences between ethylene and nitrogen, ethylene is one of the most problematic hydrocarbons with respect to the efficient gasification of cargo tanks. Additionally, ethylene is one of the most expensive cargoes carried on gas carriers. The above aspects make it necessary to carry out a detailed analysis of the flushing of nitrogen-loaded cargo tanks with ethylene vapors to determine the range of technical parameters to enable more efficient tank gassing-up. This paper provides a detailed analysis of an experimental cargo tank gassing-up operation on an ethylene carrier. The process was carried out in accordance with previously-determined assumptions to optimize the discussed operations, assess how the cargo tank pressure influences this process, reduce cargo loss during gassing-up, and eliminate cargo loss during its cooling. The conclusions from this experiment provide guidelines for subsequent tests.

4

Operational problems of ethylene transport by LPG gas carriers

Wieczorek Agnieszka, Giernalczyk Mariusz

Journal of KONES

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2019

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Vol. 26, No. 1

191--197

EN

Ethylene is one of the basic raw materials of the petrochemical industry used for the production of plastics, mainly plastic packaging. The USA is the largest producer of this compound. The enormous increase in demand for Ethylene has been observed in recent years in China as well as in the Middle and Far East. This caused an unprecedented increase in the demand for transport of this cargo by sea. Ethylene carriers for its transport are special construction LPG vessels, having a cascade cycle with Propylene medium (less often the refrigerant R 404 A). They have been designed in such a way as to withstand a working pressure of up to 5.4 bar, and the minimum temperature of the transported load is minus 104⁰C for fully cooled Ethylene. This cargo is explosive in the mixture with air (within concentrations of 2.75-2.6%) and during heating under elevation pressure. Therefore, it is required to transport Ethylene in with an inert gas, most often Nitrogen. During the operation of LPG carriers carrying Ethylene, processes of aeration, inerting, gassing-up, cooling tanks and a cargo are repeatedly carried out. The most problematic to carry is gassing-up operation, because it is associated with significant amounts of Ethylene loss, this causes large financial losses. In the article, the authors attempted to diagnose the most serious problems during carrying out the most important for cargo loss the cargo handling operations.

5

Optimization of gassing-up operation based on comparative analysis of two twin ethylene carriers

Wieczorek A., Giernalczyk M.

Journal of KONES

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2018

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Vol. 25, No. 1

441--446

EN

The article consists comparative analysis of the gassing-up operation – purging cargo tanks with cargo vapour, on gas carriers carrying primarily Ethylene – one of the most expensive cargo of all hydrocarbons carrying by the sea. The source of the problem constitutes similar densities of both gases under specific conditions – Ethylene and Nitrogen – a gas that tanks are purged before gassing-up. The analysis is made for considerable optimization of the process. The comparison of gassing-up methods is based on tests and measurements on two particular twin gas carriers. In both cases different methods – parallel and cascade were chosen to do the gassing-up (parallel means to purge tanks separately at the same time, cascade means to purge tanks one after the other) what allows specifying beneficial procedure. What was estimated during voyages were technical parameters measured during gassing-up, time of the process and the most important information – loss of the cargo. Analysis of particular stages of the operation also allows estimate the level of gas mixing in the tank. The basic purpose of this profile, based on Ethylene loss, is selecting alternative for carrying this operation in more efficient way, what constitutes determining the most proper method of gassing-up – parallel or cascade and setting temperatures, pressures, mass flows which minimize vapour of Ethylene vented to the atmosphere.

6

Numeryczne modelowanie zjawiska dyspersji fizycznej – model rzeczywistej struktury

Gołąbek A., Szott W.

Nafta-Gaz

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2017

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R. 73, nr 2

75--80

PL

Artykuł dotyczy praktycznego rozwiązania problemu związanego z modelowaniem zjawiska dyspersji fizycznej. Jest to kontynuacja poprzednich publikacji autorów, w których obliczenia zostały wykonane na bardzo uproszczonych modelach symulacyjnych. W ramach pracy dostosowano proponowane wcześniej modyfikacje symulatora BOAST do modeli rzeczywistych struktur posiadających złożoną geometrię oraz niejednorodne rozkłady parametrów złożowych. Zmiany te dotyczyły implementacji hybrydowej metody minimalizacji dyspersji numerycznej oraz rozszerzenia standardowych równań nasyceń o dodatkowy człon dyspersji fizycznej. Praca zawiera krótki opis proponowanej metody sterowania wielkością strefy mieszania się gazów wraz z wynikami jej zastosowania. Ponieważ poprawne modelowanie zjawiska dyspersji fizycznej ma szczególne znaczenie przy symulowaniu wytwarzania bufora PMG oraz późniejszej jego pracy, do przetestowania proponowanej metody użyto modelu krajowego złoża gazu ziemnego, które dzięki specyficznej geometrii oraz dobrym własnościom kolektorskim jest naturalnym kandydatem do konwersji na podziemny magazyn gazu. W ramach pracy skonstruowano kilka modeli geometrycznych wybranej struktury, różniących się od siebie rozdzielczością siatki bloków, na których wykonano szereg symulacji. Wszystkie symulacje dotyczyły procesu wytwarzania poduszki buforowej PMG, podczas którego zachodzi zjawisko mieszania się gazu zatłaczanego z gazem rodzimym znajdującym się w strukturze. Przedstawione w pracy, w postaci rysunków i wykresów, wyniki wykonanych symulacji wykazały efektywność stosowanej metody ograniczenia dyspersji numerycznej (zarówno dla obliczeń mobilności z ważeniem wielopunktowym w kierunku napływu, jak i podwójnej siatki dyskretyzacji) oraz efekty zastosowania różnych wielkości parametrów dyspersji fizycznej.

EN

The paper addresses the problem of physical dispersion modeling using a standard reservoir simulator. The paper builds upon the previous works of the authors, where simplified models were used to cope with the problem. Simulator modifications presented there are now applied to a model of real geological structures with complex geometry and inhomogenous distributions of basic reservoir parameters. The modifications include a hybrid method of numerical dispersion reduction and the extension of standard flow equations with physical dispersion terms. The method is briefly described and results of its application are discussed. The proposed approach, is tested on a realistic model of a process to converge a selected domestic gas reservoir with favorable structure and preferred storage parameters, into a practical UGS facility. In particular the first phase of this conversion, i.e. building the gas cushion is modeled where gas-gas mixing phenomena governed by dispersion effects is of significant importance. Several models with different mesh sizes of the structure were constructed and used to simulate the process. The simulation results present the effects of the mixing process between injected and original gases, taking place in realistic porous media and under typical operation conditions. They confirm the practical value of the presented method to successfully reduce unwanted numerical dispersion and efficiently introduce controllable physical dispersion.

7

Numeryczne modelowanie zjawiska dyspersji fizycznej – modyfikacja pełnowymiarowego symulatora złożowego

Gołąbek A., Szott W.

Nafta-Gaz

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2016

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R. 72, nr 7

528--533

PL

W artykule przedstawiono praktyczne rozwiązanie dla modelowania zjawiska mieszania się gazów w złożu w postaci niezbędnych modyfikacji pełnowymiarowego symulatora złożowego typu black oil. Modyfikacje te objęły zagadnienia redukcji efektu dyspersji numerycznej oraz wprowadzenie numerycznego opisu zjawiska dyspersji fizycznej. Zastosowaną metodę przetestowano na trójwymiarowym modelu złoża opisującym procesy wzajemnego wypierania mieszających się gazów (zatłaczanego i rodzimego).

EN

The paper presents a practical solution of gas-mixing modelling in a reservoir by the appropriate modifications of a full-size black oil reservoir simulator. These modifications included techniques for the reduction of numerical dispersion and implementation of physical dispersion phenomena. The method was tested on a 3-D reservoir model of the deposit describing the processes of mutual displacement of miscible gases.

8

Energetyczne wykorzystanie gazów kopalnianych

Postrzednik S.

Energetyka

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2016

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nr 1

15--20

PL

Na terenach eksploatacji węgla kamiennego występują dwa główne gazy kopalniane, zawierające składniki palne (głównie metan CH4 ): gaz pokładowy (odmetanowania pokładów węgla kamiennego) i gaz wentylacyjny (wyprowadzany do otoczenia poprzez szyby wentylacyjne). Energetyczne wykorzystanie tych gazów jest ważnym zagadnieniem technicznym, a także ekologicznym (emisja gazów cieplarnianych), co wynika głównie z obecności metanu CH4 w każdym z tych gazów. W artykule wskazano na celowość realizacji procesu mieszania strumienia gazu pokładowego ze strumieniem gazu wentylacyjnego, bez pobierania dodatkowego strumienia powietrza (tlenu O2) z otoczenia. Do oceny przydatności energetycznej tak pozyskiwanej mieszanki palnej zaproponowano wskaźnik Ω, następnie szacowano oraz analizowano jego wartości.

EN

On the hard coal mining areas two main colliery gases containing flammable components (mainly methane CH4) can be found: seam gas, coming from coal seams methane drainage, and ventilation gas emitted to the atmosphere by ventilation shafts. Utilization of these gases for energy generation purposes is an important technical and ecological (emission of greenhouse gases) problem resulting mainly from the content of CH4 in every one of them. Indicated is advisability of mixing coal seam and ventilation gases only without taking any additional air stream (O2 ) from the atmosphere. For the evaluation of such combustible mixture usability for energy generation purposes a factor Ω was proposed with the consequent estimation and analysis of its value.

9

Modyfikacje symulatora złożowego dla potrzeb modelowania zjawisk mieszania się gazów

Gołąbek A., Szott W.

Nafta-Gaz

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2015

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R. 71, nr 3

177--184

PL

W pracy przedstawiono praktyczne rozwiązanie dla modelowania zjawiska mieszania się gazów w złożu w postaci niezbędnych modyfikacji symulatora złożowego typu black oil. Modyfikacje te objęły zagadnienia redukcji efektu dyspersji numerycznej oraz wprowadzenia numerycznego opisu zjawiska dyspersji fizycznej. Zastosowane metody przetestowano na jedno- i dwuwymiarowych modelach złożowych opisujących procesy wzajemnego wypierania płynów mieszających się (gazów).

EN

The paper presents a practical solution of gas-mixing modelling in a reservoir by appropriate modifications of a standard black oil reservoir simulator. The modifications included techniques for the reduction of numerical dispersion and implementation of physical dispersion phenomena. The modified simulator was tested for 1D and 2D reservoir models describing displacement processes of mixing fluids (gases).