With the increased consumption of LNG, more and more attention is given to the utilization of LNG-based cryogenic energy in various industries. Tokyo Electric has been involved in the development of cryogenic power generating systems with high efficiency and good load following capability to attain the goal of energy conservation. In 1979, as the first of its kind in the world a demonstration plant built by us in the premises of the Sodegaura Power Station was successfully put into operation. This 442kW demonstration unit adopted the direct expansion/propane Rankin system consuming LNG at the rate of 10tons/hour, which was selected among other systems and passed thorough design review in terms of system optimization best suited configuration and control system during the conceptual design stage. This was followed by another 241kW demonstration unit with 5ton/hour LNG consumption adopting mixed working fluid Rankine cycle system in December, 1980. They were subjected to various tests to verify their plant performance, load following capability, durability etc. under a number of conditions and proved suitable for commercial operation. Tokyo Electric as a utility company consuming more than half the total LNG imports, is promoting a commercial cryogenic power plant project in view of energy conservation through the utilization of cryogenic energy. We disire to make it efficient and best designed by incorporating the technologies established by and experiences acquired from the demonstration units, and also latest operational and technological suggestions given by other cryogenic power plants in operation.
Osaka Gas Co., Ltd. has been receiving LNG from Brunei and Indonesia at the Senboku Works I and II since 1972 and 1977, respectively. As well known LNG has cold energy about 200kcal/kg LNG, and power generation plants which utilize LNG cold are being highlighted as a process in many LNG receiving terminals to reduce their operation cost and to save energy. To realize these plants it is mentioned that the most important problem is how we can design the economical heat exchanger. For that purpose we have developed new types of LNG vaporizer named OG-TRI-EX. It offers a number of advantages in terms of economy construction and operation compared with conventional LNG vaporizer-open rack type vaporizer. Using these technologies two commercial power generation plants by LNG cold were constructed in 1979 and 1982 at Senboku Works II. Since then, have been in operation without any trouble and contribute to the reduction in power cost in the Works.
Power generation systems using the cold energy of LNG have been introduced at some LNG receiving terminals in accordance with the increase of LNG consumption as a substitute for oil in Japan. Tokyo Gas Co., Ltd., has been engaged in intensive research and experiments for the power generation system to recover the cold energy of LNG effectively, jointly with Chiyoda Chemical Engineering & Construction Co., Ltd. This system is called MFR (Multi-component Fluid Rankine) Cycle using a mixture of light hydrocarbons (CH4, C2H6, C3H8, C4H10) as working fluid. The principle applied for this cycle is categorized as Rankine Cycle utilizing sea water as the heat source and LNG as the heat sink. The high recovery rate of exergy from LNG cold energy is the feature of the MFR Cycle. A pilot plant of the MFR Cycle was constructed at Negishi Works of Tokyo Gas Co., Ltd. with vaporizing capacity of 5t/H of LNG in August, 1980. The experiment was completed in April, 1981 with maximum electricity of 130kW. On the basis of the experiment, a commercial plant has been investigated with vaporizing capacity of 100t/H of LNG and maximum electricity of 4, 000kW. In this paper, results of the research and development for the MFR Cycle are reported such as the analysis of the pilot plant experiment and the basic conception for the commercial plant.