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1

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.

2

Simplified methods for the assessment of consequences of navigational accidents as a tool for development of port regulations: Liquefied Petroleum Gas ships in Świnoujście–Szczecin waterway taken as example

Gucma L., Bąk A.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2016

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nr 46 (118)

134--140

EN

The paper presents research performed in order to indicate the threats posed to liquid petroleum gas (LPG) carriers maneuvering in the ports and fairway of Szczecin–Świnoujście. The effects of collision with another vessel, going aground, or striking a stationary object are taken into account. As a safety criterion, the possibility of damage to the cargo tanks is taken. As a result of the research, recommendations for ship movement in the ports and fairway were issued. The research method applied in this study consisted of several stages. In the first stage, experts determined possible scenarios of collision and grounding, taking into consideration local and navigational conditions. In the following steps, the external energy was calculated and an empirical model was used to determine the damage to the LPG carrier. In the last step, the necessary measures to be introduced port regulations are presented as conclusions of the research.

3

Analiza wydajności chłodniczej kaskadowego obiegu skraplania etylenu i stanu izolacji zbiorników ładunkowych podczas transportu ładunku na gazowcu LPG o pojemności 22500 m3

Nanowski D.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2014

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z. 86 [290], nr 2

225--230

PL

W pracy przedstawiono metody analizy służące do oceny efektów schładzania etylenu podczas transportu morskiego tego ładunku. Wykonano je na statku transportującym etylen, gdzie stwierdzono znaczne różnice pomiędzy zakładanymi przez projektantów prędkościami schładzania w zbiornikach ładunkowych, a tymi uzyskiwanymi podczas podróży morskiej. Temperatura ładunku wynosiła około minus stu stopni Celsjusza. Problemy stwierdzono po dziesięciu latach eksploatacji statku. Przeprowadzone obliczenia i testy miały za zadanie przeanalizowanie dwu głównych możliwości spadku prędkości chłodzenia ładunku, tj. obniżenia współczynnika wydajności chłodniczej systemu kaskadowego skraplania ładunku oraz stanu izolacji zbiorników ładunkowych. W tym celu połowa ładunku została odcięta od instalacji skraplającej na okres czterdziestu ośmiu godzin, a druga połowa etylenu w zbiornikach była w tym czasie schładzana przez wszystkie trzy układy instalacji kaskadowej. Wzrost temperatury w zbiornikach w okresie dwu dni testu umożliwił dokonanie obliczeń ilości ciepła napływającego poprzez izolację termiczną do ładunku. W celu obliczenia wydajności chłodniczej obiegów kaskadowych wykonano szczegółowe pomiary w dwu różnych okresach czasu i w różnej konfiguracji. Obliczenia przeprowadzono na oceanie Atlantyckim w okolicy wysp Azorskich przy średniej temperaturze otoczenia wody i powietrza ok. 19°C.

EN

The paper presents methods of analysis used to assess results of precooling of ethylene during sea transport. The analysis was done during carrying ethylene, when significant differences between designed and performed speed of precooling in the cargo during sea transport was observed. Temperature of ethylene was around minus 100°C. The problems appeared on the board of ten years old ship. Calculation and tests were done in order to investigate two main reasons for the decrease of precooling speed of cargo, i.e. decreasing of refrigeration capacity of reliquefaction plant and the condition of the cargo tank insulation. For this purpose precooling of half cargo tank was stopped for 48 hours and reliquefaction of operated by all three installation systems. The increase of temperature in tanks during two days enabled to perform the calculation of heat quantity flow through the cargo tank insulation. The calculations of cooling capacity of cascade cycles were taken in two different periods of time and configuration. Calculations were made near the Azores in the Atlantic Ocean with average ambient and sea water temperature approximately of 19°C.

4

Cargo loading rate assessment for CC4 mixtures carried on board LPG ships

Nanowski D.

Zeszyty Naukowe Akademii Morskiej w Gdyni

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2013

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nr 81

93--97

EN

This paper presents a method of calculations in order to assess possible cargo loading rate for CC4 cargo when its composition is taken into account. Cargo loading rate is essential in use of LPG carriers. After short description of C4-Crude (CC4) cargoes, composition of sample cargo is shown. Example of LPG carrier loading log is discussed and explained. Reliquefaction system used on board ship is taken into account and its refrigeration capacity is discussed. Microsoft Excel is used to calculate total cargo loading rate for CC4 cargoes. Assumptions for preparing its formulas are explained, final result as a diagram is shown. Conclusions are discussed.

PL

W publikacji zaprezentowano metodę obliczeniową służącą do określania raty załadunkowej dla ładunku CC4, kiedy jego skład chemiczny jest brany pod uwagę. Rata załadunkowa jest istotną wielkością przy eksploatacji gazowców LPG. Po krótkim opisie ładunków C4-Crude czyli CC4 przedstawiono jego przykładowy skład chemiczny. Przedyskutowano i wyjaśniono okrętowe parametry załadunkowe istotne przy tej operacji. Przeanalizowano wpływ instalacji skraplania ładunku statku. Wyjaśniono założenia przyjęte w arkuszu kalkulacyjnym Excel, dzięki któremu oblicza się raty załadunkowe, do budowy zastosowanych formuł obliczeniowych. Przedstawiono wykresy możliwe do wykorzystania w praktyce. We wnioskach przedyskutowano uzyskane rezultaty.

5

The comparison of theoretical to practical cargo loading rate of butane - analysis of LPG carrier reliquefaction plant

Nanowski D.

Journal of KONES

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2013

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Vol. 20, No. 1

227--231

EN

This paper presents a performance of reliquefaction plant analysis in order to assess possible cargo loading rate for Butane (C4H10). The highest cargo loading rate is essential in use of LPG carriers because of economical point of view. Loading and discharging cargo time at ports substantially influences on a financial effect of the ship owner. Because of different cargo grades, which number is continuously increasing, crucial is to know real efficiency of gas plan, before signing some contract with customer. On board these types of ships the highest efficiency of reliquefaction plant is crucial. After short description of fully refrigerated gas carrier, theoretical data of analysed ship, taken from ship documentation is shown. Taking into account this data, expected cargo compressors parameters and cargo loading rate are discussed, explained and assumed. In next step, real ambient Butane loading process carried out on board LPG carrier is described. All essential values and reliquefaction plant readings, taken in loading port are presented. The comparison of theoretical result based on available documentation to practical effects obtained in the port is performed. Analysis, mainly taking into account gas plan, answers if it operated with the highest possible efficiency and met cargo loading parameters expected according to ship manuals. Conclusions are discussed.