A design method for optimum feed location of the upper column for high purity oxygen product in an air separation process.

This paper deals with the design of a new algorithm of PID control based on fractional calculus (FC) in production of technical gases, i.e. in a cryogenic air separation process. Production of low pressure liquid air was first introduced by P. L. Kapica and involved expansion in a gas turbine. For application in the synthesis of the control law, for the input temperature and flow of air to the expansion turbine, it is necessary to determine the appropriate differential equations of the cryogenic process of mixing of two gaseous airflows at different temperatures before entrance to the expansion turbine. Thereafter, the model is linearized and decoupled and consequently classical PID and fractional order controllers are taken to assess the quality of the proposed technique. A set of optimal parameters of these controllers are achieved through the genetic algorithm optimization procedure by minimizing a cost function. Our design method focuses on minimizing performance criterion which involves IAE, overshoot, as well as settling time. A time-domain simulation was used to identify the performance of controller with respect to a traditional optimized PID controller.

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Exergy Analysis of a Novel Cryogenic Concept for the Liquefaction of Natural Gas Integrated Into an Air Separation Process

Volume 6A: Energy ◽

10.1115/imece2016-67221 ◽

2016 ◽

Author(s):

S. Tesch ◽

T. Morosuk ◽

G. Tsatsaronis

Keyword(s):

Natural Gas ◽

Power Consumption ◽

Exergy Analysis ◽

Primary Energy ◽

Separation Process ◽

Air Separation ◽

Total Power ◽

Separation Unit ◽

Total Power Consumption ◽

Liquefaction Temperature

The increasing demand for primary energy leads to a growing market of natural gas and the associated market for liquefied natural gas (LNG) increases, too. The liquefaction of natural gas is an energy- and cost-intensive process. After exploration, natural gas, is pretreated and cooled to the liquefaction temperature of around −160°C. In this paper, a novel concept for the integration of the liquefaction of natural gas into an air separation process is introduced. The system is evaluated from the energetic and exergetic points of view. Additionally, an advanced exergy analysis is conducted. The analysis of the concepts shows the effect of important parameters regarding the maximum amount of liquefiable of natural gas and the total power consumption. Comparing the different cases, the amount of LNG production could be increased by two thirds, while the power consumption is doubled. The results of the exergy analysis show, that the introduction of the liquefaction of natural gas has a positive effect on the exergetic efficiency of a convetional air separation unit, which increases from 38% to 49%.

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Simulation and Analysis of Cryogenic Air Separation Process with LNG Cold Energy Utilization

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.881-883.653 ◽

2014 ◽

Vol 881-883 ◽

pp. 653-658 ◽

Cited By ~ 9

Author(s):

Yong Qiang Xiong ◽

Ben Hua

Keyword(s):

Energy Consumption ◽

Liquid Nitrogen ◽

Electric Energy ◽

Separation Process ◽

Air Separation ◽

Energy Utilization ◽

Utilization Efficiency ◽

Pure Oxygen ◽

Pure Nitrogen ◽

Cold Energy

In this paper, a cryogenic air separation process with LNG cold energy utilization is proposed to produce liquid nitrogen and high pressure pure oxygen gas economically. To reduce the electric energy consumption of air separation products, liquid nitrogen have been produced by condensing the separated pure nitrogen gas with LNG cold energy utilization, and the recycled nitrogen is served to transfer cold energy from LNG stream to cool off air stream in the proposed cryogenic air separation process. The specifications of streams and the major equipments of the air separation process are simulated with Aspen Plus software and the main parameters analysis are performed. The results show that the energy consumption of the proposed air separation process with LNG cold energy utilization decreased about 58.2% compared with a conventional cryogenic air separation process. The compressed pressure of recycled nitrogen has a big impact on the cost of air separation products and utilization efficiency of LNG cold energy. The LNG cold energy could be fully utilized when the recycled nitrogen has been compressed to above 6.5MPa.

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