To improve the residual ratio of gas in a hydrate in transportation and preservation.
The hydrating rate calculation part 72 of a calculation/control apparatus 60 obtains a hydrating rate x of a gas hydrate product based on the detection signal of a water content sensor 56 and inputs the rate into an evaluation function/control target temperature calculation part 78. A residual ratio calculation part 80 obtains a gas hydrate residual ratio y from the particle diameter of a gas hydrate product obtained from a particle diameter calculation part 76, a production condition and a transportation condition set in a production/transportation condition set part 84 and the gas hydrate residual ratio corresponding to the particle diameter memorized in the residual ratio data memory part 86 and inputs the ratio in the evaluation function/control target temperature calculation part 78. The evaluation function/control target temperature calculation part 78 obtains an evaluation function J=x×y and a formation temperature to maximize the evaluation function J and outputs the temperature as a control target temperature in a control part 82. The control part 82 controls a formation temperature detected by a temperature sensor 54 so as to reach a control target temperature.
MATSUO KAZUYOSHI
MIYATA JUNYA
Okubo Misao