Method and device for improving efficiency of sponge oil absorption (UOP)

CATEGORY: LPG - LIQUEFIED PETROLEUM GAS 
Method and device for improving efficiency of sponge oil absorption (UOP)

Type	Patent
Inventor	Kiran Ladkat
Inventor	Neeraj TIWARI
URL	Free Full Text Source:  http://www.google.com/patents/US20150053590
Assignee	Uop Llc
Patent Number	US20150053590 A1
Issue Date	Feb 26, 2015
Abstract	A method for improving efficiency of sponge absorption includes providing cold flash drum liquid to an inlet of a cold stripper to produce a cold stripper net overhead vapor stream rich in liquid petroleum gas, and separately providing hot flash drum liquid to an inlet of a hot stripper to produce a hot stripper net overhead vapor stream rich in hydrogen. The cold stripper net overhead vapor stream and the hot stripper net overhead vapor stream are separately routed to a sponge absorber to recover a liquid petroleum gas output stream using sponge oil. In particular, the cold stripper net overhead vapor stream and the hot stripper net overhead vapor stream are separately routed to the sponge absorber at different tray locations

Process for liquefaction of natural gas (UOP)

CATEGORY: LNG - LIQUEFIED NATURAL GAS 
Process for liquefaction of natural gas (UOP)

Type	Patent
Inventor	John L. Griffiths
URL	Free Full Text Source:  http://www.google.com/patents/US20150033793
Assignee	Uop Llc
Patent Number	US20150033793 A1
Issue Date	Feb 5, 2015
Abstract	A process and system for production of liquefied natural gas (LNG) from natural gas. The natural gas is first partially purified by removal of water and other contaminants, followed by partial chilling to freeze some contaminants and to allow for production of a purge stream to remove other contaminants. These contaminants may be removed from the stream. The process has advantages of low cost and improved removal of contaminants.

Optimal Synthesis of Cascade Refrigeration in Liquefied Natural Gas Cycles by Pinch-Exergy

CATEGORY: LNG – LIQUEFIED NATURAL GAS
Journal of Oil, Gas and Petrochemical Technology, Article 2, Volume 1, Number 1, Winter 2014, Page 29-41
Optimal Synthesis of Cascade Refrigeration in Liquefied Natural Gas Cycles by Pinch-Exergy
1 Meysam Kamalinejad; 2Majid Amidpour  ; 1Seyed Mojtaba Mousavi Naeenian          
1 K.N.Toosi, Univercity of Technology, Tehran, Iran
2 K.N. Toosi University of Technology, Tehran, Iran.
Abstract
Iran’s vast common natural gas resources and the necessity to extract and export it as Liquefied Natural Gas (LNG) to distances more than 3000Km opens a lucrative field for researchers to optimize LNG cycles. In this article heat integration in cryogenic cycles by determining interacycle partition temperature and optimizing refrigeration features like Subcooler, Presaturator, aftercooler, reboiler, superheater and economizer is investigated to reduce compressor shaftwork.
Better conceptual understanding of design improvement is illustrated on Composite¬ Curve (CC) and Exergetic Grand Composite Curves (EGCC) of Pinch-Exergy analysis diagrams. A program (LNG-Pro) is developed by integrating Visual Basic Application, Refprop(Reference Fluid Thermodynamic and Transport Properties) and Excel MINLP Solver to automate the methodology on an LNG plant with the capacity equal to a south pars gas field phase. Shaftwork is step by step reduced from 1479.36Kj/Kg to 1255.5Kj/Kg and 1158.8Kj/Kg which is 2.46% less than required energy for liquefaction in LNG industry.
Free Full Text Source: http://jogpt.pgu.ac.ir/?_action=articleInfo&article=4779

Integration of light hydrocarbons cryogenic separation process in refinery based on LNG cold energy utilization

CATEGORY: LNG – LIQUEFIED NATURAL GAS
Chemical Engineering Research and Design, Available online 26 April 2014, In Press, Corrected Proof
Integration of light hydrocarbons cryogenic separation process in refinery based on LNG cold energy utilization
Yajun Li, Hao Luo
Key Lab of Heat Transfer Enhancement and Energy Conservation of the Ministry of Education, South China University of Technology, Guangzhou, Guangdong Province 510640, China
Abstract
The recovery of light hydrocarbons from refinery gas has become increasingly significant. However, the cryogenic separation required needs low process temperatures, substantially increasing the refrigeration load requirements and, consequently, the compression requirements associated with the refrigeration system.
Researchers applied the cold energy of liquefied natural gas (LNG) to light hydrocarbons cryogenic separation process to replace the compression refrigeration system on the basis of a China refinery. Results reveal that LNG can provide 14,373 kW cold energy for the separation process, resulting in a direct compression power saving of 7973 kW and making the utilization rate of LNG cold energy as high as 71.9%.
Full Text Source (Subscription or Fee): http://www.sciencedirect.com/science/article/pii/S0263876214001853

Analysis of available data from liquefied natural gas rollover incidents to determine critical stability ratios

CATEGORY: LNG – LIQUEFIED NATURAL GAS
AIChE Journal, Volume 60, Issue 1, pages 362–374, January 2014
Analysis of available data from liquefied natural gas rollover incidents to determine critical stability ratios
Pooya Arjomandnia (1), Moses O. Tade (2), Vishnu Pareek (2), Eric F. May (1)
eric.may@uwa.edu.au
1 Centre for Energy, School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, WA, Australia
2 Dept. of Chemical Engineering, Curtin University, Bentley, WA, Australia
Abstract
Liquefied natural gas (LNG) rollover refers to the sudden mixing of stratified LNG layers, which can cause the generation of significant amounts of boil-off gas. Such events are a significant safety concern in LNG storage but there are no reliable models for its description at industrial scales available in the open literature. In this article, the data and models for LNG rollover existing in the open literature are reviewed and a new framework for quantitatively analyzing the limited available data is presented.
We extended the definition of the hydrostatic stability ratio for binary mixtures to allow its estimation for multicomponent mixtures, either from the reported LNG layer compositions or measurements of the LNG layer densities. By analyzing the graphical data of Bates and Morrison (Int J. Heat Mass Transfer. 1997;40:8) the critical value of the stability ratio, Rc, separating the diffusive phase of LNG rollover from the penetrative convection phase was estimated to be 3.8 ± 0.5. This is significantly larger than the critical ratio of 2 reported for saline solutions and is also larger than the initial stability ratio of 1.7 estimated from the best documented LNG rollover incident at La Spezia in 1971. Lumped-parameter models for LNG rollover reported in the literature have successfully described the La Spezia incident by using the Reynolds analogy to estimate mass transfer rates from heat transfer correlations. However, these same models are unsuccessful when applied to other reported LNG rollover incidents, with the predicted rollover time being too short because the mass-transfer coefficient is overestimated. The results presented here suggest that these limitations could be overcome by using a smaller mass-transfer coefficient (estimated, e.g., from the Chilton-Colburn analogy) and by tracking the multicomponent system's stability ratio until the critical value is reached whereupon the mass transfer regime changes.
Free Full Text Source: http://onlinelibrary.wiley.com/doi/10.1002/aic.14254/full

Method And System To Prevent Carry-Over Of Hydrocarbon Mist From An NGL Column Of An LNG Plant (Chevron U.S.A.)

CATEGORY: LNG – LIQUEFIED NATURAL GAS
PATENT
Method And System To Prevent Carry-Over Of Hydrocarbon Mist From An NGL Column Of An LNG Plant (Chevron U.S.A.)
United States Patent Application 20130055757
Inventors:
Huang, Stanley H. (Sugar Land, TX, US)
Sheth, Kalapi D. (Sugar Land, TX, US)
Application Number:
13/226192
Publication Date:
03/07/2013
Assignee:
Chevron U.S.A. (San Ramon, CA, US)
Abstract:
The present disclosure is directed to a method and system for preventing carry-over of C₂₊ hydrocarbon mist from an NGL recovery column in an LNG plant. A wash loop of recirculating liquid hydrocarbon is provided at the upper portion of the NGL column. A sidestream of liquid hydrocarbons collected within the column is removed from the column and pumped to sufficient height to be returned to the column at a temperature substantially equivalent to the temperature of liquid with the upper portion of the column. In one embodiment, liquid hydrocarbons of a desired composition can be loaded and reloaded to a working medium holding drum in fluid communication with the top of the column. The working medium can be selected to be sufficiently heavy not to be lost from the column and to have a suitable freezing point to avoid freezing within the column. 
Description:
FIELD
The present disclosure relates to methods and systems for operating a natural gas liquids recovery column within a liquefied natural gas plant.
BACKGROUND
In the production of liquefied natural gas (LNG), chilled natural gas is introduced to a natural gas liquids (NGL) recovery column which serves to separate methane to be liquefied from valuable natural gas liquids, i.e., C₂₊ hydrocarbon components to be recovered. The natural gas liquids are removed at the NGL column bottom and are further processed in a series of fractionation columns to recover ethane products, propane products, butane products and C₅₊ products. The NGL column is operated at a lower temperature and higher pressure than the other, aforementioned fractionation columns. When the NGL recovery column is operating relatively close to critical conditions for the fluid at the top of the column, minor fluctuations in the system pressure can result in the formation of NGL mist or fine droplets which can become entrained with the methane leaving the top of the NGL column, a condition referred to as “carry-over.” Demisters in the form of mesh pads are commonly placed at the top of the column to capture such mist, yet such pads alone are sometimes ineffective and the carry-over problem persists. Carry-over results in difficulties in methane liquefaction operations downstream of the NGL column. For instance, the heavier components of the NGL mist may freeze out in the liquefaction operations, resulting in clogging of flow paths.
It is known to provide the NGL recovery column with reflux, in which case the light components leaving the top of the column are condensed in a heat exchanger in which latent heat is removed. The condensed liquid is then separated in a subsequent reflux drum, and returned to the top of the column where the condensed liquid is sprayed into droplets upon which mist is collected and removed from the upward flow of gas. Such reflux operations may reduce carry-over of hydrocarbon mist from the NGL recovery column, at the high energy cost involved in condensing vapor components to liquid components. Furthermore, such operations have been found not to be adequate to control carry-over of hydrocarbon mist under all conditions.
It would be desirable to have a reliable and energy-efficient method for preventing carry-over of hydrocarbon mist from an NGL recovery column in an LNG plant.
SUMMARY
In one aspect, the invention relates to a method for preventing hydrocarbon mist from escaping the top of an NGL recovery column in an LNG plant. The method includes the steps of flowing a hydrocarbon gas stream including a hydrocarbon mist upwardly in an NGL column, spraying droplets of a hydrocarbon liquid into the gas stream to strip at least some of the hydrocarbon mist from the upwardly flowing gas stream, collecting the droplets of the hydrocarbon liquid in a tray within the column, removing a liquid sidestream of the collected hydrocarbon liquid from the column, and returning at least a portion of the liquid sidestream to form the droplets which are sprayed.
In another aspect, the invention relates to a system for preventing hydrocarbon mist from escaping the top of an NGL recovery column in an LNG plant. The system includes a column for recovering NGL. The column includes a natural gas inlet for feeding natural gas to the column, an NGL outlet at a lower portion of the column for dispensing natural gas liquids from the column, a gas outlet at an upper portion of the column for removing gaseous components from the column, at least one tray for collecting liquids within the column, a spray mechanism for generating a spray of droplets which are collected as liquids in the at least one tray, a liquid inlet for receiving and feeding liquid to the spray mechanism and a liquid outlet for receiving liquid from the at least one tray. The system further includes a loop for fluidly connecting the liquid outlet with the liquid inlet to transport a sidestream of liquid, the loop including a pump in fluid communication with the liquid outlet for receiving and pumping the at least a portion of the sidestream to the liquid inlet.
Free Full Text Source: http://www.freepatentsonline.com/y2013/0055757.html

Enhancement of LNG Plant propane cycle through waste heat powered absorption cooling

CATEGORY: LNG – LIQUEFIED NATURAL GAS
Applied Thermal Engineering, Available online 21 April 2012, In Press, Accepted Manuscript — Note to users
Enhancement of LNG Plant propane cycle through waste heat powered absorption cooling
P. Rodgers a, A. Mortazavi b, V. Eveloy a, S. Al-Hashimi a, Y. Hwang b, R. Radermacher b
a The Petroleum Institute, Abu Dhabi, U.A.E
b Department of Mechanical Engineering, University of Maryland, College Park, MD, U.S.A
Abstract
In liquefied natural gas (LNG) plants utilizing sea water for process cooling, both the efficiency and production capacity of the propane cycle decrease with increasing sea water temperature.  Authors address this issue by studying several propane cycle enhancement approaches.  They require minimal modification of the existing plant configuration.
The approaches rely on the use of gas turbine waste heat powered water/lithium bromide absorption cooling to either (i) subcool propane after the propane cycle condenser, or (ii) reduce propane cycle condensing pressure through pre-cooling of condenser cooling water. Two alternative methods of pre-cooling condenser cooling water are considered nn the second approach, consisting of an open sea water loop, and a closed fresh water loop. In all cases, three candidate absorption chiller configurations are evaluated.  They are: single-effect, double-effect, and cascaded double- and single-effect chillers. The thermodynamic performance of each propane cycle enhancement scheme, integrated in an actual LNG plant in the Persian Gulf, is evaluated using actual plant operating data.
Full Text Source (Subscription or Fee): http://www.sciencedirect.com/science/article/pii/S1359431112002748

Improvement of energy utilization in natural gas liquid plant through using self-refrigeration system

World Renewable Energy Congress 2011 – 8-13 May 2011, Linkoping, Sweden

Improvement of energy utilization in natural gas liquid plant through using self-refrigeration system

H.Farzaneh^*, B.Abbasgholi

info@hfarzaneh.com

Science and Research Branch, Islamic Azad University, Tehran, Iran

Abstract:

One of the most energy intensive processes in the oil industry is the natural gas liquid or NGL recovery plant. The main energy consumer in conventional NGL plants is propane refrigeration. Hence, more attention should be focused on the effective utilization of propane chillers in a NGL plant.

In this study, a novel process configuration for recovery of natural gas liquids in NGL plant is purposed. The required refrigeration in this configuration is obtained by a self-refrigeration system. The novel scheme generates refrigeration internally, decreasing cooling load of propane chiller and providing additional refrigeration for inlet gas cooling due to plant capacity increase.

The recycled stripping gas also eliminates the need for external reboiler heat. The warmer the stripping gas, the less demand is placed upon the bottom reboiler, thereby saving fuel and energy cost. In this investigation, a simulation model has been developed using novel configuration in Gachsaran NGL1200 in south of Iran. The model has been applied for evaluating of energy utilization in this plant. Results of the model show decreasing in total electricity demand of the plant from 268 kWh/t_NGL to 175 kWh/t_NGL by decreasing cooling load and electricity consumption in propane chiller. Also, the need for reboiler heat is satisfied and efficacy of demethanizer column is improved from 72% to 84% by more NGL recovery. Finally, economical analysis of the new retrofit has been studied.

Free Full Text Source: http://www.ep.liu.se/ecp/057/vol7/012/ecp57vol7_012.pdf