1 Views from Expert Groups on Criteria: A Case of AHP Application for LNG Cold Utilisation Phatthi Punyasukhananda, JGSEE, KMUTT, and Athikom Bangviwat, JGSEE, KMUTT. Abstract--Liquefied natural gas (LNG) cold energy utilisation technologies which are the techniques of making use of the cold energy from LNG cryogenic temperature (-163 degree Celsius) during re-gasification process, instead of wasting it into seawater, have been studied to identify the most appropriate LNG cold utilisation technology for Maptaphut LNG receiving terminal, Thailand. Analytical Hierarchy Process (AHP) which is the scientific decision-making tool has been applied to analyse and identify the best option of LNG cold utilisation for the terminal. Expert opinions from business and non-business group are interviewed and the prioritisation result are evaluated, the outcome from experts opinions shows totally different weights for criteria. Experts from business group show the highest concern on economic criteria while experts from non-business group show the high concern on social and environmental criteria. This criteria weighting results represent the interests of the organisations. Business group (mostly are the profit maximisation organisation) tends to focus on economic factor while non-business group (mostly are non-profit organisation) tends to focus on environmental and social factors. The differences in criteria weighting results from different expert groups are important concerns for AHP application. When AHP method is chosen to be a decision making tool on the project, careful grouping of the interviewees is highly recommended during the participant selection process. Otherwise the input data for AHP can be too complicated and difficult for analysis. L I. INTRODUCTION NG is the natural gas in liquid phase which is kept under minus one hundred sixty three (-163) degree Celsius for the purpose of cost effective in long distance transportation by ships. In order for efficient utilization and in-land transportation of LNG, LNG has to be transformed from liquid phase to gas phase at LNG receiving terminal by regasification process. Instead of using seawater to boil up LNG from liquid phase to gas phase for pipeline utilisation without any value added from cryogenic temperature of LNG, LNG cold energy P. Punyasukhananda is with The Joint Graduate School of Energy and Environment, King Mongkut s University of Technology Thonburi, 126 Pracha-Uthit Road, Bangmod, Tungkru, Bangkok 10140, Thailand (e-mail: phatthi@hotmail.com). Center of Energy Technology and Environment, Ministry of Education, Thailand A. Bangviwat is with The Joint Graduate School of Energy and Environment, King Mongkut s University of Technology Thonburi, Center of Energy Technology and Environment, Ministry of Education, Thailand (e-mail: athikom.bangviwat@outlook.com). utilisation techniques to harvest this potential cold energy from LNG are to be explored. At present, there are more than 10 concepts of LNG cold energy utilisation available around the world but only one (1) technology is required to be implemented at the Maptaphut LNG receiving terminal due to land limitation and investment constraint. Thus, technology selection and prioritisation process to identify the best technology is required. The application of Analytical Hierarchy Process (AHP) which is one of the scientific multi-criteria decision making tools is selected for the technology selection process [1]. II. LNG COLD ENERGY UTILISATION TECHNOLOGIES CONCEPT In regasification process, LNG absorbs heat from a heat source to raise its temperature up until reaching the boiling point which in turn cools down the heat source. In a general regasification process, seawater is usually used as a heat source of the process and its temperature will be reduced at the end of the process without any benefit to the system. This situation initiated the idea of an exploration for LNG cold energy utilisation. Energy and cost of energy which are concealed in LNG should not just be wasted into surrounding. Technologies for the harvest of the benefit of the cold energy should be identified and applied to make the most out of it. Utilisation of LNG cold energy means how to effectively utilise the benefit of LNG at cryogenic temperature during its vaporisation process. The amount of latent heat and sensible heat required for transforming LNG at very low temperature (- 163 degree Celsius) to working condition at room temperature is the main factor to identify the potential heat exchange process for the utilisation of LNG cold energy. By matching the different amounts of required heat and temperatures during LNG regasification process, eleven (11) LNG cold utilisation techniques to cover all potential industrial sectors can be identified. Examples of the technologies are 1) integration of LNG regasification process with air separation and liquefaction process, 2) integration of LNG regasification process with liquefaction and solidification of carbon dioxide production process (LCO2-LNG Integration Plant), 3) integration of LNG regasification process with cryogenic power generation process, 4) integration of LNG regasification process as a heat sink for the chemical industry, 5) integration of LNG regasification process with the refrigeration and freezing process and etc.
2 Fig. 1. Integration of LNG Cold on differences kind of application, separated by required cooling temperature. As show in Fig. 1, difference kinds of applications are potentially matched with LNG cold by its required cooling temperature on each process. As required utilised temperature becomes lower, the advantage of LNG cold utilisation becomes larger. Thus LNG cold energy can be utilised more effectively at lower temperature (not higher than -100 degree Celsius). From the study of LNG cold utilisation technology at Maptaphut LNG receiving terminal [2], by technical and nontechnical constraints for example the limitation of site specific constraints and high send-out pressure requirement of natural gas to gas grid at Maptaphut LNG receiving terminal, some LNG cold utilisation options in portfolio are screened out. As the screening result, there are only four (4) technologies which have potential to be applied at the terminal which are; 1. air separation and liquefaction, 2. liquefaction/solidification of carbon dioxide production, 3. rankine cycle cryogenic power generation, and 4. chilled water for refrigeration.typefaces and Sizes Fig. 2. AHP structure for LNG cold energy utilisation technology prioritisation and selection. AHP criteria based on 4 pillars of technology analysis which are technological aspect, economical aspect, environmental aspect and social aspects are identified as the main criteria of AHP structure and each sub criteria are logically identified as a parameter to analyse each alternative characteristic in order to perform the best systematic and reasonable factor for the prioritisation process, the criteria and sub criteria with their definition have been identified by the author as show in Table 1; TABLE I CRITERIA FOR LNG COLD ENERGY UTILISATION SELECTION Aspect Criteria Definition by the Author Technological Aspect % of Energy Recovery (%ER) Reliability of Alternative and LNG Receiving Terminal (RoA) Ease of Operation (EoO) Site Condition (SC) How much energy benefit from LNG stream which LNG cold utilisation technique can be extracted as a sensible and latent heat by the principle of difference temperature and pressure Since LNG cold utilisation require LNG stream as a heat sink or coolant of the system, without LNG enters the system, the system will have an effect on its operating conditions and performance. LNG cold utilisation has to work as regasification unit for the terminal thus the system has to have high reliability to satisfy NG demand from customer which is the 1st priority function of terminal. Complexity of the system a nd level of expert that require to operate the system LNG Cold Utilisation unit has to be nearby LNG terminal to reduce investment in high price LNG pipeline and the utilisation area has to be fit in with the availability land space near LNG terminal (~ 350 rai or 560,000 m 2, maximum distance is 2-3 km) III. ANALYTICAL HIERARCHY PROCESS (AHP) APPLICATION Analytical Hierarchy Process (AHP) is a tool which is mainly used to solve a multiple criteria decision-making problem and it aims at quantifying relative priorities for a given set of alternatives on a ratio scale. Tangible and intangible factors related to the problems are systematically organised based on the principle of Eigen value and pair-wise comparison to create a consistency of the comparison of alternatives and the relationship among the decision factors in the decision-making process. According to the principle of AHP, the problem is structured into 3 layers as shown in Fig. 2 with the goal to identify best LNG cold energy utilisation technology at Maptaphut LNG receiving terminal by the assessment of 9 criteria on each alternative Economical Aspect Environmental Social Demand of Product (DoP) Supply or Resources (SoR) Competitiveness of Product (CoP) Pollution and Environmental (PnE) Social Wealth Creation (SWC) Product that each LNG cold utilisation unit produce has to be on demand in the market or for terminal internal use Availability of resources required to operate the system until get the finishing product. It can be explain and measure term of cost of commodity, availability, accessibility and sustainability. Saving from the a pplication of LNG cold (baht/kg of LNG) when compare to that system without LNG cold utilisation. Cost of product that each LNG cold utilisation produce has to be lower than the system without LNG in order to make competitive advantages Low (and not excess the limit) CO 2 and VOCs emission and other pollution which is generated from the system when each LNG cold utilisation is installed The system generates positive e ffect on social around LNG receiving terminal and country, for example job opportunity creation.
3 TABLE II VALUE AND DEFINITION OF RELATIVE IMPORTANCE FOR PAIRWISE COMPARISON SCALE Value Definition of relative importance for pairwise comparison scale Explanation 1 Equal importance Two items contributes equally 2 Equally to moderately 3 Moderately importance Judgment slightly favours one over another 4 Moderately to strongly 5 Essential or strong importance Judgment strongly favours on over another 6 Strongly to very strongly 7 Very strong or demonstrated importance The dominance of one over another is demonstrated in practice 8 Very strongly to extremely 9 Extremely or Absolutely importance On is favoured over another with highest affirmation IV. EXPERT GROUPS TO BE INTERVIEWED To prioritise the result, two groups of experts from business sector and non-business sector are chosen to give their opinions for AHP evaluation process. The members of business group are mainly chosen from the energy related sectors, and the members from the non-business group are chosen from academic sector, government sector and other non-profit organisations who have background knowledge on engineering and energy. TABLE III EXPERT OPINION EVALUATION PROCESS TEMPLATE FOR AHP EVALUATION Fig. 3. Criteria weight result of the experts from business group. Fig. 4. Criteria weight result of the experts from non-business group. V. RESULTS AND DISCUSSION A. AHP Result and Discussions The interview of 14 experts (7 experts from business group and 7 experts from non-business group) was conducted as the results were shown in Fig.2. The relative weights of the different criteria were calculated (detailed in Appendix A). For the criteria weight, the result from the business group indicates that the most important criteria is the economic aspect, where the highest weight is given for competitiveness of product and followed by the supply of resource and the demand of product criteria with the percentages of 24.7, 24.2 and 19.5 respectively as shown in Fig.3. On the other hand, the non-business group, who mostly were the experts from government and academic sector, emphasised on the environmental and social aspects. The highest weight is given to the social wealth creation (26.5%) and followed by the pollution and regulation criteria (23.1%), as shown in Fig.4. B. Effect of Criteria Weight on the AHP Result From the weight criteria results, it is clearly shown that expert opinion from business and non-business group have a different criteria priority in the set of AHP criteria as shown in Fig. 5. Experts from business group express their high concern on the economic factors while show the relatively low concern on environmental and social factors. The experts from nonbusiness group express their highest concern on social and environmental factors and give a very low concern on economic factors. When analyse the criteria weight result against characteristic of expert group will see that the criteria weight results from business group represents their professional purpose which are maximising benefit and income of their organisation, thus the result settle in the high concern on economic factors. The experts from non-business group who mostly are from the non-profit organisations clearly indicate very low concern on economic factor and illustrate high concern on noneconomic factors which are environmental, social and technical factors.
interest may be necessary. Otherwise the input data for AHP can be too complicated and difficult for analysis. 4 Fig. 5. Comparison of criteria weight result between business and nonbusiness group. The effect on criteria weighting from different groups of interviewees represents an important issue on the application of AHP method. Even though the set of criteria are exactly the same, the opinions are drawn from different groups of experts with different areas of interest. The weights given for criteria can be totally different based on each expert group s point of view. The result can greatly affects the final AHP result on the prioritisation of alternatives. VI. CONCLUSION During the evaporation process in LNG regasification unit, LNG releases a large amount of cold energy (about 850 kj/kg) by exchanging heat with seawater and the released LNG cold energy has potential to be utilised through certain processes to enhance energy efficiency and economic performance of the whole terminal system. More than ten (10) technologies were initially listed as possible LNG cold energy utilisation technologies (detailed in Appendix B) to be installed at LNG receiving terminal. The site specific constraints scope the possible LNG cold utilisation at Maptaphut LNG receiving terminal to only four (4) LNG cold energy utilisation technologies, which are 1. Air Separation and Liquefaction, 2. Rankine Cycle Cryogenic Power Generation, 3. Liquefaction/Solidification of Carbon Dioxide, and 4. Chill Water Production. Analytical Hierarchy Process (AHP) is selected to be a multi-criteria decision making tool to prioritise and identify best LNG cold utilisation technology for the terminal. Expert opinions from business and non-business groups are designed to be interviewed as inputs for AHP evaluation. The interview results show vast differences in weights given for criteria. The business group has high concern on economic factors, while the non-business group has high concern on social and environmental factors. An important point drawn from the interview of this study is the bias of criteria weightings given by different expert groups. The results clearly show that different expert groups who have different expertise and points of view tend to weight more on the criteria of their concerns. Thus, the selection of interviewees in the AHP method has to be clearly identified and grouping of those who have the same area of expertise and Fig. 6. Comparison of criteria weight result between business and nonbusiness group. From Fig. 6 show that if we group the environmental, social and technical criteria into Community Concern Aspect and group the remaining criteria regarding to the business parameter as Private Concern Aspect, we will see that the business group tends to have low community concern degree parameter which reflect their main characteristic to maximise organisation profit. On the other hand, non-business group show the high degree of community concern which also reflects their organisation purpose to contribute the most to community. Appendix A VII. APPENDIX The data of pair-wise comparison of the different technologies with respect to each criteria from business group (interviewed from 7 experts) that was analysed in the LNG cold energy utilisation technology selection. TABLE IV PAIR-WISE COMPARISON OF THE DIFFERENT CRITERIA AND THEIR RELATIVE WEIGHT FOR BUSINESS GROUP (CONSISTENCY RATIO, CR = 0.0231) CR=0.0231 %ER RoA EoO SC DoP SoR CoP PnE SWC RW %ER 1 1/2 1/2 1 1/5 1/5 1/5 1 1 0.0423 RoA 2 1 2 1 1/4 1/4 1/4 2 2 0.0738 EoO 2 1/2 1 1 1/5 1/5 1/5 1 1 0.0499 SC 1 1 1 1 1/5 1/5 1/5 1 1/2 0.0457 DoP 5 4 5 5 1 1/2 1/2 4 4 0.1954 SoR 5 4 5 5 2 1 1 4 4 0.2420 CoP 5 4 5 5 2 1 1 5 4 0.2473 PnE 1 1/2 1 1 1/4 1/4 1/5 1 1/2 0.0443 SWC 1 1/2 1 2 1/4 1/4 1/4 2 1 0.0592 Sum 23.04 16.00 21.50 21.97 6.35 3.85 3.80 21.00 18.00 TABLE V PAIR-WISE COMPARISON OF THE DIFFERENT CRITERIA AND THEIR RELATIVE WEIGHT FOR NON-BUSINESS GROUP (CONSISTENCY RATIO, CR = 0.0252) CR=0.0252 %ER RoA EoO SC DoP SoR CoP PnE SWC RW %ER 1 2 3 3 2 2 5 1/2 1/2 0.145 RoA 1/2 1 1 2 1 1 3 1/3 1/3 0.078 EoO 1/3 1 1 2 1 1 3 1/4 1/4 0.071 SC 1/3 1/2 1/2 1 1 1 1 1/6 1/6 0.045 DoP 1/2 1 1 1 1 1/2 1 1/5 1/5 0.053 SoR 1/2 1 1 1 2 1 1 1/3 1/3 0.070 CoP 1/5 1/3 1/3 1 1 1 1 1/6 1/5 0.042 PnE 2 3 4 6 5 3 6 1 1/2 0.231 SWC 2 3 4 6 5 3 5 2 1 0.265 Sum 7.37 12.83 15.83 23.00 19.00 13.50 26.00 4.95 3.48
5 Appendix B List of existing LNG cold energy utilisation technologies and their description in brief. 1. Integration of LNG regasification process with air separation and liquefaction process (ASU-LNG Integration Plant) 2. Integration of LNG regasification process with gas separation plant process (GSP-LNG Integration Plant) 3. Integration of LNG regasification process with liquefaction and solidification of carbon dioxide production process (LCO2-LNG Integration Plant) 4. Integration of LNG regasification process with cryogenic power generation process (Rankine Cycle) 5. Integration of LNG regasification process with cryogenic power generation process (Direct Expansion) 6. Integration of LNG regasification process as a heat sink for the chemical industry 7. Integration of LNG regasification process with Boil-Off Gas (BOG) liquefaction system 8. Integration of LNG regasification process with freeze seawater desalination process 9. Integration of LNG regasification process with gas turbine process (to increasing turbine efficiency) 10. Integration of LNG regasification process with the refrigeration and freezing process (in warehouses and frozen food or etc.) 11. Integration of LNG regasification process with snow flake production process (for artificial production snow in amusement winter park) Technical aspect and operating principle of potential LNG cold utilisation technologies above are explained in Table VI. VIII. ACKNOWLEDGMENT The authors gratefully acknowledge the contributions of A. Bangviwat, C. Menke, C. Sorapipatana, P. Wongwises and D. Gvozdenac for brilliant comments and suggestions on the original version of this document. IX. REFERENCES [1] Subramanian, N. and Ramanathan, R. (2012), A Review of Application of Analytical Hierachy Process in Operations Management, International Journal of Production Economics [2] Punyasukhananda P., and Bangviwat A. (2011), Utilisation of LNG Cold Energy at Maptaphut LNG Receiving Terminal, 4th International Conference on Sustainable Energy and Environment (SEE 2011): A Paradigm Shift to Low Carbon Society, 23-25 November 2011, Bangkok, Thailand [3] Kanagawa, T. (2011), Japan s LNG Utilisation and Environmental Efforts. [4] Kusagawa, M., Hamatani, E., Sakamoto, Y., Takubo, M., Ogawa, E., Ikeda, K. and Emi, H. (2008), A Fully Optimized Cascaded LNG Cold Energy Utilisation System. [5] Otsuka, T. (2006), Evolution of an LNG Terminal: Senboku Terminal of Osaka Gas, Proceeding of the 23rd World Gas Conference. [6] Hirakawa, S. and Kosugi, K. (1981), Utilisation of LNG cold. IPC Business Press Ltd and IIR. Volume 4 Number 1 January 1981 [7] Lina, W., Zhangb, N. and Gua, A. (2010), LNG (liquefied natural gas): A necessary part in China's future energy infrastructure, Energy, 35, pp. 4383 4391. [8] CNOOC. (2006), LNG Cold Energy Utilisation Outlook, China-USA Oil and Gas Forum, Hangzhou, China. X. BIOGRAPHIES TABLE VI LNG COLD ENERGY UTILISATION TECHNOLOGIES AND THEIR FEATURES [3-8] LNG Cold Energy Principle of Operation with LNG Cold Energy Utilisation Utilisation Product/Benefit Integrate with air separation and liquefaction Integrate LNG stream with air separation and liquefaction process in order to produce liquid nitrogen, oxygen and argon. LNG is used as cold Liquid nitrogen, oxygen and argon / reduce system power source of the system to reduce power in the process. Integrate with gas separation plant Integrate LNG stream with propane and ethane separation process to reduce power Reduce GSP system power from the system. Integrate with liquefaction/ solidification of carbon Integrate LNG stream with liquid carbon dioxide production process. LNG is used as cold source of Liquid CO2, Dry iced / reduce power dioxide production the system to reduce power in the process. Integrate with cryogenic power generation (Rankine Use LNG as heat sink of the system in Rankine Cycle power generation which has pr opane as Electricity/ electrical energy with free operating cost Cycle) intermediate medium and has seawater as heat source. Integrate with cryogenic power generation (Direct Use high pressure LNG from LNG pump to expand through direct expander turbine to produce Electricity/ electrical energy with free operating cost expansion) mechanical power to drive generator for power generation. Integrate with chemical industry Integrate LNG stream with industrial process which require cold source or heat rejection for reducing Reduce system power overall power of the process. Integrate with Boil-Off Gas (BOG) liquefaction system Use PCM to extract heat from BOG to make BOG condense and become LNG again. LNG re-liquefaction/ Reduce power cost Integrate with seawater desalination Use LNG as a cold source of system to freeze seawater before separate salt and water in the Fresh water/ reduce operating cost desalination process Integrate with gas turbine Use LNG to cool down compressor inlet air of the Increase system efficiency power plant system to increase overall system efficiency. Integrate with refrigeration process Integrate LNG stream with refrigeration process and use LNG as cold source of the process to Chilled air or water / reduce operating cost reduce power Integrate with snow flake production process Integrate LNG stream with snow flake production process and use LNG as cold source of the process to reduce power Snow flake / reduce operating cost Phatthi Punyasukhananda was born in Chaiyaphoom, Thailand on March 20, 1979. He graduated from the King Mongkut s University of Technology Thonburi (KMUTT), Thailand, and studied Master degree at the University of Canterbury, Christchurch, New Zealand for Master of Engineering in Management. Now he is currently a PhD candidate in Energy Technology Study at the Joint Graduate School of Energy and Environment (JGSEE), Thailand. Phatthi received honorary degrees for his bachelor of mechanical engineering (KMUTT), and a Gold Medal by academic recorded from Engineering Institute of Thailand. In 2014, he received the Chartered Industrial Gas Consultant (CIGC) Certificate by Gas Technology Institute (GTI), USA. His employment experience started at PTT Public Company Limited, Thailand National Oil Company from 2004 until now. He has been worked as a researcher in Energy Application Technique and Engine Lab Department under PTT Research and Technology Institute. His special fields of interest are natural gas technology and technology analysis frameworks.