8.4 Development of major auxiliary equipment

8.4.1 R&D Goals

8.4.1.1 Research Objective

8.4.1.2 Scope of research

In this fiscal year, we conducted the basic engineering requirements for designing overall system of air separation and supply units as a fuel of hydrogen combustion turbine power plants completely and consequent assignment of other heat exchangers and emergency unit.

Economical study and subjects in future proposed are conducted. For very hot side exchangers, consequent assignment of the two re-entrusted manufacturers' conceptual design as completion scheme sre conducted and selection of the best technology between them and subject in future are decided.

8.4.2 Results in FY 1998

(1) Development of utilization of cryogenic from liquid hydrogen

1. Review of oxygen production units using cryogenic from liquid hydrogen
   Overall system analysis was studied in case of emergency shutdown of air separation units for 1000MW power plants (two 500MW-hydrogen combustion turbine power plants), and for back-up system against the shut-down, two hours supply of hydrogen and oxygen with proper temperature and pressure is required to the system. Fig 8-4-1 shows hydrogen-oxygen supply system.

2. Study of back-up system of air separation units.
   Necessary units for back up are hydrogen vaporization units, storage tanks for liquid hydrogen with capacity of 2 hours and oxygen vaporization units. Concept design for both vaporization units and storage tanks were conducted. Fig 8-4-2 shows the back-up system.

3. Trial design of heat exchangers for air separation oxygen production units
   Based upon the specification of raw material air booster pump 1 and 2, and air compressors which were decided in last year, trial design was conducted for main heat exchangers and oxygen vaporizers.

   As a result of this study such as introduction of high performance plate fin type of heat exchangers, which can exchange simultaneously heat transfer for multi fluids, main heat exchangers and oxygen vaporizers are confirmed to be feasible to commercial use. For instant, Fig 8-4-3 shows the specification of main heat exchangers and over view of them.

4. Cost estimates and economical evaluation
   In order to conduct economical evaluation, subcoolers, reboiler condensers and low heat exchangers designed in last fiscal year and main condensers and oxygen vaporizers and back-up system designed in this fiscal year were subjects to cost estimates, then effect of cryogenic utilization was verified through the cost calculation of oxygen production in this R&D.

   Oxygen production cost of air separation units using cryogenic energy of liquid hydrogen is 0.286 kWh/Nm³ as comparing one of conventional system with 0.595kWh/Nm³. And oxygen production cost is 10.92 yen/Nm³ (7.65yen/kg) and it is shared of 2.58yen/kWh for hydrogen combustion turbine power plants.

(2) Development of very hot side heat exchangers

1. Concept design of very hot side heat exchangers
   One re-entrusted firm (Toshiba) proposed cylindrical type of the heat exchangers with several features such as introduction of high performance heat transfer tube with serrated fins, introduction of austenite stainless alloy (sus310j1tb) tubes at exchangers 14 and 15 besides hastelloy X at maximum temperature portion of outlet headers of the exchanger 15, self support structure of the exchangers with the mechanism of sliding bearing at the bottom and inner- outer insulation of the heat exchangers.

   Fig 8-4-4 shows the concept design of Toshiba.

   Fig 8-4-5 shows the description of Mitsubishi's very hot side heat exchanger.

2. Evaluation of optimum technology
   Two re-entrusted firms presented their design results to third major equipment committee held on January 19, 1999. And then through questions and answers by fax and e-mail between committee members and re-entrusted firms via JAPEIC, the committee members evaluated their technology according to evaluation items discussed and decided in last fiscal year meeting.

   This evaluation result was discussed at final committee meeting on February 1999 and Dr. Taniguchi; the chairman of the committee summarized the results as follows.

   Based upon the study results by the re-entrusted firms, the committee performed fair and transference evaluation for them. Two achieved the project goal sufficiently, and also we evaluated their positive attitude for the study and reliable results were proposed. As a final evaluation for them, self-support type cylindrical structure design proposed by Toshiba was slightly higher evaluation than Mitsubishi'.

   Toshiba's result is to deeply consider given draft loss and to achieve compactization of the heat exchangers. Then this committee recommends Toshiba' technology as optimum.

   Table 8-4-1 shows the evalution result of hot heat exchanger