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Development of Simplified Feed-water Heating System using
Multi-stage Steam Injectors for Nuclear and Thermal Power Plant
1．Summary
A steam injector (SI) is a passive jet pump
with no movable parts, able to drive water by supersonic steam jet,
reaching a discharge pressure even higher than the supply steam pressure.
Moreover the SI works as a direct contact heat exchanger between steam and
water. We developed multi-stage SIs by using steam directly extracted from
the turbine, which has high performance in wide operation range and can be
used in parallel-operation to simplify feed-water heating system of
nuclear and thermal-power plant.
2．Details of the Technique
The “simplified feed-water heating system
using multi-stage SIs” has been developed for the feed-water system of the
current ABWR(Advanced Boiling Water Reactor). Figure 1shows the current low-pressure
feed-water heating system, in which the heaters are set up above the
condenser as necked heaters. We have developed the multi-stage SIs system
as shown in Fig.2, composed of in-line
four SIs and a jet deaerater. The feed-water heating system can be greatly
simplified by replacing the current low-pressure heaters with the compact
multi-stage SIs as shown inFig.3.
Moreover, the multi-stage SIs system can be applied to the feed-water
heating system of thermal power plants.
The multi-stage SIs system
makes it possible to reduce the volume and weight of the low-pressure
feed-water heating system by around one third of that of ABWR and the
height of the turbine building by around 3.5m, it would be possible to cut
down construction cost consequently. Moreover, the maintenance cost and
the loss of electricity generation can be reduced since it becomes
unnecessary to replace the feed-water heaters two times with 6 months in
the plant life cycle.
We are planning to make the system wide use in
the small-sized system before applying to the large-sized system.
3．Endurance Test
We carried out endurance tests by continuous
operation using steam from the thermal-power station at SIET in Italy and
confirmed that there was no performance degradation and erosion damage
under more severe conditions than those for normal feed-water heater.
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