JPS6157445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling waste heat generation equipment.

Waste heat power generation equipment is attracting attention in various fields as an energy-saving measure. TECHNICAL FIELD The present invention relates to a control method for optimal waste heat utilization to cold energy utilization, and in particular to a control method for an LNG cold utilization power generation system.

Figure 1 shows a general system diagram of a conventional power generation facility that utilizes the cold energy of LNG. In Fig. 1, LNG enters the LNG evaporator 1 from the conduit 6,
Here, the LNG is gasified by the heat of condensation of the circulating medium of the Rankine cycle, and is sent out from the conduit 7. Meanwhile, the circulating medium is condensed by LNG evaporator 1,
After being pressurized in the pump 2 via the conduit 8, it is evaporated in the medium evaporator 3 through the conduit 9 by seawater from the conduit 12, and enters the expansion turbine 4. Here, the circulating medium is expanded and electric power is generated by the generator 5. The circulating medium leaving the expansion turbine 4 is circulated again to the LNG evaporator 1 via a conduit 11. In this cold energy power generation facility, it is important to keep in mind when designing it that the circulating medium must be in a liquid state on the suction side of the circulation pump 2, so
When determining the heat transfer area of the evaporator 1, in order to design the circulating medium to completely liquefy, it is necessary to provide a margin for the heat transfer area from the viewpoint of safety design. If the circulating medium at the inlet of pump 2 becomes supercooled, there will be no particular problem in operation, but from the point of view of recovering energy by making more effective use of the cold energy of LNG. It's not a good idea. In other words, the available cold energy is the amount of heat held by LNG, and assuming this amount of heat is constant, supercooling the circulating medium means adding the degree of supercooling to the amount of heat of condensation, and the amount of heat per unit flow rate of the circulating medium is To increase. Therefore, the amount of circulating medium to be circulated is reduced.
Furthermore, if the circulating medium in the LNG evaporator 1 and the medium evaporator 3 is supercooled, the circulating medium in the LNG evaporator 1 will be condensed and supercooled, but compared to the condensation heat transfer coefficient, the Since the heat transfer coefficient is a low value, a larger heat transfer area is required. The same applies to the medium evaporator 3. Therefore, in the case of the conventional technology, when considering the point of using cold energy more effectively, the generated power,
The current state of the heat exchanger is insufficient from the economic point of view.

The present invention aims to increase the efficiency of waste heat recovery by reducing the degree of subcooling during condensation of the circulating medium in conventional waste heat utilization power generation equipment.

The present invention utilizes the cooling of LNG to condense and liquefy a circulating medium, and after increasing the pressure of the liquefied circulating medium, evaporates it and introduces it into an expansion turbine. In waste heat power generation equipment that condenses and liquefies the circulating medium that has exited, the temperature of the condensed and liquefied circulating medium and the pressure of the circulating medium at the outlet of the expansion turbine are detected and sent to a controller, which controls the pressure at the inlet of the expansion turbine. The feature is that it is adjusted to an appropriate value.

Hereinafter, an embodiment of the method for controlling a waste heat generation equipment according to the present invention will be described with reference to FIG. 2. In FIG. 2, the same parts as in FIG. 1 are denoted by the same reference numerals and explanations will be omitted. The condensation temperature of the circulating medium discharged from the LNG evaporator 1 is detected by the temperature detector 16, and the controller 14 calculates so that the circulating medium has a saturated pressure with respect to this detected temperature, and the outlet pressure of the expansion turbine 4 is It is adjusted by the throttle valve 15 at the inlet of the expansion turbine 14 so that the target value is achieved. The pressure at the outlet of the expansion turbine 4 is also detected by a pressure detector 13, and the temperature and pressure of the circulating medium are always sent as information to the controller 14, so that the outlet pressure of the expansion turbine 4 can be appropriately controlled.

As described above, according to the present invention, the condensation temperature of the circulating medium can be maintained near the saturated state at all times, and the heat exchanger is in a heat exchange state only by evaporation and condensation of the circulating medium, so that the same transmission With a thermal area, the amount of evaporation and condensation of the circulating medium can be increased compared to when the circulating medium is supercooled. Therefore, the amount of circulating medium to be circulated can be increased, which has the effect of increasing the amount of circulating medium entering the expansion turbine and increasing the generated and recovered power.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a power generation facility using the cold energy of LNG according to the prior art, and FIG. 2 is a system diagram showing an example of a device implementing the control method for a power generation facility using waste heat according to the present invention. 1... LNG evaporator, 2... pump, 3... medium evaporator, 4... expansion turbine, 5... generator,
6-12... Conduit, 13... Pressure detector, 14...
...controller, 15...throttle valve, 16...temperature output device.

Claims (1)

[Claims] 1 Using the cold of LNG, the circulating medium is condensed and liquefied, and the liquefied circulating medium is pressurized and then evaporated and introduced into the expansion turbine to drive the generator connected to the expansion turbine. In waste heat power generation equipment that condenses and liquefies the medium again, the temperature of the condensed and liquefied circulating medium and the pressure of the circulating medium at the outlet of the expansion turbine are detected and sent to a controller, and the controller adjusts the pressure at the inlet of the expansion turbine to an appropriate value. A method for controlling waste heat power generation equipment, characterized by adjusting the power generation equipment.