ENVIRONMENTALLY FRIENDLY TECHNOLOGY
High temperature generator safety control
SUPER ABSORPTION
The absorption cycle
When the temperature of the high temperature generator is higher | Together with the cooling water safety control and absorbent crystallization pro- | ||||||||||||||||
than a certain temperature level, the steam consumption is controlled to | tection control, the safety operating zone is broadened. | ||||||||||||||||
sustain safe operation. |
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Graph 8. Safety control chart |
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C) |
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| 100 |
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generator(temp.highofTemperature° |
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| Steam consumption ratio |
| ratio(%)consumptionSteam | ||||
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| 80 |
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| Steam consumption |
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| control for 10 minutes |
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160 |
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| 60 |
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| 40 |
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150 |
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| Temperature of |
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| 20 |
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| high temperature generator |
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140 |
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| 0 |
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0 | 5 | 10 | 15 | 20 | 25 | 30 | 35 |
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Time(minutes)
The absorption cooling cycle, like the compression refrigeration cycle, uti- lizes the latent heat of evaporation of a refrigerant to remove heat from the entering chilled water. The compression refrigeration system uses a chlorine based refrigerant and a compressor to transport the refrigerant vapor to be condensed in the condenser. The absorption system, however, uses water as the refrigerant and an absorbent to absorb the vaporized refrigerant. Heat is then applied to the solution to release the refrigerant vapor from the absor- bent. The refrigerant vapor is then condensed in the condenser.
The basic absorption cycle (see Figure 1) involves generator, condenser, evaporator and absorber with refrigerant (liquid) and lithium bromide as the working solutions. The generator utilizes a heat source (burner, steam or hot water) to vaporize the diluted lithium bromide solution. The water vapor that is released travels to the condenser where it is condensed back into a liquid, transferring the heat to the cooling tower water. Once condensed, the liquid refrigerant is distributed over the evaporator tubes, removing the heat from the chilled water and vaporizing the liquid refrigerant. The concentrated lithium bromide solution from the generator passes into the absorber, absorbs the refrigerant vapor solution from the evaporator and dilutes itself. The diluted lithium bromide solution is then pumped back to the generator where the cycle is started again.
Figure 1. Simplified absorption cycle
| Refrigerant vapor |
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| Condenser |
| Generator | |
Cooling | Liquid | Concentrated |
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water | Heat source | |||
refrigerant | solution | |||
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Cooling water
Chilled water
Evaporator | Absorber |
Absorbent pump
Expansion of safety operating zone
This ensures quick response to rapid changes and maintains stable operation.
Double effect type
The generator section is divided into a high temperature generator and a low temperature generator. The refrigerant vapor produced by the high tempera-
Figure 2. Double effect absorption cycle
Safety operating zone is between 19° C and 34° C of cooling water
temperature. (In case cooling inlet water temperature is 32° C)
Graph 9. Safety operating chart
100 |
ture generator is used to heat the LiBr solution in the low temperature gen- erator in which the pressure (hence the boiling point) is lower. Thus the heat of condensation is effectively utilized.
Refrigerant vapor
Condenser
Low temperature generator
Cooling water
Refrigerant vapor
Hight temperature generator
input(%) | 80 |
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60 |
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Maximum | 40 |
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20 |
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| 0 |
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| (Variable from 20° C to 33° C) |
| ★ | ★+2 | ||||
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Cooling water inlet temperature(° C)
Liquid refrigerant
Evaporator
Chilled water
Intermediate solution
Concentrated solution
Absorber
Cooling water
Diluted solution
Absorbent pump
Heat source
Crystallization protection
As mentioned in the single effect type, the refrigerant vapor produced by the low temperature generator is sent to the condenser to become liquid refriger- ant. On the other hand, the refrigerant vapor produced by the high tempera-
Figure 3. Detail of generator
Refrigerant vapor to condenser
Microprocessor observes the absorbent concentration. Steam supply is stopped and the unit is recovered to the normal operation when the con- centration is over certain limit, to prevent the crystallization of absorbent.
Space saving by compact design
With the high performance heat transfer tubes, weight and size is re- duced by 10% of the previous C model.
ture generator turns to water as it releases heat to the intermediate LiBr solution. This happens inside the heat transfer tubes in the low temperature generator. The refrigerant vapor produced by both low and high temperature generators turns to refrigerant liquid and mixes in the condenser before re- turning to the evaporator.
Low temperature generator
Condensed refrigerant
Refrigerant vapor
High temperature generator
Heat source
Intermediate solution
Concentrated solution
Diluted solution
10 | 11 |
