JPS6051622B2 - Effective energy utilization method in heat supply equipment consisting of a combination of heat pump cycle and cogeneration steam cycle - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention was made to increase the heat utilization rate when supplying heat for district heating and cooling, process heating, and factory work. This paper relates to a method for effectively utilizing energy in a heat supply facility consisting of a combination of a combined heat and steam cycle.

[Conventional technology]

When supplying heat for district heating and cooling, process heating, and factory work, it is effective to use various types of waste heat or cogeneration power, but currently, methods that use dedicated boilers are mainly used. ing.

Traditionally, combined heat and power systems generate electricity by burning fuel.
This is a system that uses the exhaust heat of the working fluid after driving the turbine to supply medium-temperature heat, while generating power by rotating the turbine. In addition, the dedicated boiler method is a method that uses a dedicated boiler to supply heat, and the high-temperature heat generated by burning fuel is adjusted to an appropriate temperature such as medium temperature depending on the purpose of use. However, this method has a large exergy loss, and even if the heat loss to the end of use is small, the effectiveness is inevitably reduced due to a decrease in the energy level. In addition, when a centralized cogeneration system is applied, piping loss along the way may increase, and its advantages may be canceled out compared to using individual boiler systems. Furthermore, a heat storage device consisting of a combination of a heat pump cycle and a cogeneration steam cycle has been known (Japanese Patent Publication No. 54-36328).

In this heat storage device, the compressor of the heat pump cycle is driven by the steam turbine of the steam cycle, and the heat of condensation of the nasal steam discharged from the steam turbine and the heat of condensation of the high temperature refrigerant discharged from the compressor are combined. Since heat is utilized by discharging the refrigerant into a single heat storage medium tank and exchanging heat in parallel, the heat utilization rate is low, and the expansion of the high-pressure liquid refrigerant in the heat pump cycle is performed using a throttle valve. The energy from the expansion of the refrigerant is not used effectively. [Problems to be Solved by the Invention] The present invention is intended to solve the various drawbacks of the conventional combined heat and power generation system, and combines a heat pump cycle with a combined heat and steam cycle, and eliminates large load fluctuations. The purpose of this study is to find a method for effectively utilizing energy that can be efficiently adapted to the environment.

[Means for solving problems]

In order to effectively utilize energy in a heat supply facility consisting of a combination of a heat pump cycle and a cogeneration steam cycle, the screw compressor of the heat pump cycle is driven by the screw expander of the cogeneration steam cycle, and the liquid of the heat pump cycle is driven by the screw expander of the cogeneration steam cycle. In order to make use of the pressure change when the refrigerant is throttled and expanded, the screw-type two-phase flow expander is rotated during this pressure change, and this rotational force also drives the screw-type compressor. let

〔Example〕

Next, the present invention will be explained with reference to embodiments.

In the figure, A is a cogeneration steam cycle including a boiler and a heat engine, and B is a heat pump cycle.

Superheated steam from the boiler 1 flows into the screw expander 2 through the steam pipe 6, rotates the expander 2, and then passes through the steam outlet pipe 7 to the medium temperature heat exchanger (secondary heat exchanger) 8. flows into. Here, it exchanges heat with the load-side fluid flowing in the heat exchange tube 25, condenses, and is returned to the boiler 1 from the liquid tube 9 by the liquid feeding pump 10, and thereafter flows through this circulation path. On the other hand, the screw compressor 3 for the heat pump is driven because it is connected to the screw expander 2 by the rotating shaft 18, and the fluorocarbon refrigerant in the system is compressed and becomes a high-temperature, high-pressure gas through the discharge pipe 11 to the condenser. (primary heat exchanger) 12.

here. It exchanges heat with the load-side fluid flowing in the heat exchange pipe 23, condenses, and flows into the screw type two-phase flow expander 4 through the condensate pipe 13, where it is rotated using pressure energy. The screw type two-phase flow expander 4 is connected to the screw type compressor 3 by a rotary shaft 19, so after driving this and recovering power, the two-phase liquid-gas mixed fluid is passed through the conduit 14. It flows into the steamer 15. As it flows through the evaporation pipe 16, it exchanges heat with the exhaust heat fluid having an inlet 20 and an outlet 21, evaporates, and absorbs heat from the outside of the system.
It is sucked into the screw compressor 3 through the. On the other hand, the load-side fluid flows into the condenser 12 via the return pipe 22 through the heat exchange pipe 2
3, and then flows into the medium temperature heat exchanger 8 via the communication pipe 24. While passing through the heat exchange pipe 25, it is further heated to raise the temperature, and is returned to the load side via the hot water supply pipe 26. Next, the operation of this embodiment will be explained.

Since the screw type two-phase flow expander 4, which corresponds to a throttle valve, is connected to the screw type compressor 3 by the rotating shaft 19, the power is recovered, and the driving force by the screw type expander 2 is reduced by the amount of power recovered. This means that the amount of heat pumped up from the outside world by heat pump cycle B with the same power generated by the heat engine increases. A quantitative example of comprehensive heat utilization is as follows.

Now, when the superheated steam generated from the boiler 1 of the combined heat and steam cycle A is 544k91h1380°C and 11ta, this superheated steam flows into the screw expander 2 and drives it, and then the intermediate temperature heat exchanger 8 When the efficiency of the screw expander 2 is assumed to be η=0.85, 88.6 KW is obtained.

At this time, the exhaust steam from the expander 2 is 75°C and 0.4a
ta, and this exhaust steam enters the medium temperature heat exchanger 8 and is condensed. On the other hand, the load-side fluid flowing into the heat exchange tube 23 at a temperature of 30°C via the return pipe 22 reaches a temperature of 55°C and enters the communication pipe 23.
4, then flows into the heat exchange tube 25 of the medium temperature heat exchanger 8, and is heated to 70° C. by the heat of condensation.

The amount of heat of condensation here is 302,000 Kca11h.
Here, the water vapor is condensed and becomes hot water of 752c10.4ata, which is sent to the boiler 1 again by the liquid sending pump 10, heated, and turned into water vapor again.
circulate within. On the other hand, the screw compressor 3 of the heat pump cycle B uses the 88.6
The refrigerant gas Rl2 is driven by the input of KW, and the screw compressor performs gas compression work with a total efficiency of 0.85, and is introduced into the condenser 12 at 75°C and 15.51 ita into the discharge pipe 11, where it undergoes heat exchange. By exchanging heat with the return hot water of the load-side fluid at 30°C flowing inside the pipe 23, the
It becomes the condensate of a.

The amount of heat of condensation here is 490,000 Kac11h.
Also, the return hot water of 30°C flowing into the condenser 12 is 55°C.
It is heated to ℃ and flows into the medium temperature heat exchanger 8, but if this heat exchange coefficient η = 0.95, at 70℃ it is 18800k91
h amount of hot water is obtained and is returned to the load side through the conduit 26 for use.

The liquid refrigerant of Rl2 condensed in the condenser 12 is 15.5 at
The mixed fluid of the two-phase flow is injected into the screw type two-phase flow expander 4 at a pressure of 15.degree.
The screw type two-phase flow expander 4 is rotated with a pressure difference of .

This pressure energy becomes a two-phase flow of flashed liquid and gas, acts on the expander 4, and is recovered as rotational energy. Assuming that the efficiency of this expander is η=0.5, approximately 6.3 KW of power is transmitted to the compressor 3 via the rotating shaft 19 and recovered. Therefore, even if the input power transmitted from the screw expander 2 is 88.6 KW, the compressor 3 will perform compression work of 88.6+6.3=94.9 (KW). In other words, it takes 88.6 kW of power to make the screw type compressor j of heat pump cycle B perform 94.9 kW of compression work. The waste heat fluid flows into the evaporator 15 from the inlet 20, heats the refrigerant flowing in the evaporator tube 16, reaches a temperature of around 30'C, and is discharged from the outlet 21, while the gas amount is 16,100 kg.
Refrigerant gas having an evaporation heat amount of 424,000 Kca11h is sucked into the screw compressor 3. In this example, the amount of hot water in the heat supply equipment is 18,800k91h, which is 3.
Since the temperature is being raised from 0°C to 70°C, we are gaining heat.

The amount of heat of the fuel supplied to the boiler 1 in the heat supply equipment is.

The heat utilization coefficient COP of this heat supply equipment is as follows.Comparing this heat supply equipment to heating by boiler combustion alone, it is as follows.2. This will bring out the heating ability of Hao.

When the temperature of the waste heat fluid flowing in from the inlet 20 of the evaporator 15 of the heat pump cycle B is high, about 60 to 80°C,
The temperature of the condenser 12 can be as high as 100-200°C. In such cases, Rll4 or "Florinol 85", a mixture of 85 mol% trifluoroethanol and 15 mol% water (85 mol% CF3CH2OH + 5 mol% H2Ol), is used as a stable refrigerant without aging even at high temperatures. It will be done. In addition, when the condensation temperature is 100 to 130°C, Rll4 and 1
"Florinol 85" is suitable when the temperature is 30 to 200°C. Further, these are examples of refrigerants that are stable even at high temperatures, and it goes without saying that refrigerants containing different mole percentages of "florinol" can be appropriately selected and used depending on the temperature conditions, etc. Further, in the above embodiment, the temperature of the refrigerant gas flowing into the condenser 12 from the discharge pipe 11 and the temperature of the steam flowing into the medium temperature heat exchanger 8 from the steam outlet pipe 7 were both 75°C. The temperature of the refrigerant gas flowing through the discharge pipe 11 may be higher than the temperature of the refrigerant gas flowing through the discharge pipe 11 due to fluctuations in the amount of heat of the external heat source flowing into and out of the co-supply steam cycle A and/or heat pump cycle B, and fluctuations in the temperature and flow rate of the load-side fluid flowing into the equipment. If the temperature becomes higher than the temperature of the steam flowing through the pipe 7, the temperature difference may be detected and the flow direction of the load-side fluid may be reversed.

The load-side fluid enters from conduit 26 and first passes through medium temperature heat exchanger 8 and then through condenser 12 where it is heated before passing through return pipe 2.
Switch the flow so that it flows out from 2 to improve the heat transfer coefficient. For example, when the temperature of the exhaust heat source flowing into the evaporator 15 of the heat pump cycle B increases, the temperature of the refrigerant gas discharged from the screw compressor 3 also increases, for example to 80'C, and the temperature of the refrigerant gas discharged from the screw expander 2 increases. Discharge temperature 7
Since the temperature is higher than 5°C, the flow of the fluid on the load side is reversed.
Note that if a screw type liquid pump is used for the combined heat and steam cycle, high pressure can be obtained and high speed rotation can be obtained, which has the advantage of being compact, durable, and less noisy.

It is also cheaper than centrifugal turbine pumps. Next, with reference to FIG. 2, the advantage of utilizing the pressure change when the liquid refrigerant is throttled and expanded by the screw type two-phase flow expander in the method of the present invention will be explained.

A heat pump cycle that uses a throttle valve to expand the refrigerant under reduced pressure is A-+B-+C→J-+A.

C-) J is the expansion process. In this case, the amount of refrigeration heat [the amount of heat that can be pumped up by the evaporator 15] is (1A-
1j) Kcallk9. Conventional technology (Japanese Patent Application Laid-Open No. 1986-
100551) using the expansion turbine, the heat pump cycle is A→B-+C-+H-+A.

C−+H is the expansion process. In this case, although the efficiency is poor due to the expansion turbine, the amount of refrigeration heat can be increased somewhat, resulting in (IA-IH) Kcallk9. On the other hand,
In the present invention, a screw type two-phase flow expander is used, so when the refrigerant is expanded from point C, the heat pump cycle becomes A→B-+C-+G-+A, and the amount of refrigeration heat is (IA-1.

) Kcallk9 can be further increased. In addition, in the present invention, since it is possible to further perform a supercooling process on C, this heat pump cycle is A→B→C→E.
→F→D→A, and the amount of freezing heat is the largest (IA-1
D) can be Kcallkg. In this process, the working fluid in region 1 is liquid, and in region m, it is a two-phase flow fluid of gas-liquid mixture, but the screw type two-phase flow expander works efficiently with both of these working fluids. I can do it.
The relationship between the magnitude of the refrigeration heat amount is as follows.

〔Effect of the invention〕

This invention uses a centralized heat supply system to first convert high-temperature steam generated by combustion into power using a screw expander, which then drives a screw compressor in a reheat pump cycle to pump heat from a low heat source. , a system that supplies medium-temperature heat in addition to the exhaust heat generated during power generation, effectively utilizes the pressure change of the refrigerant during the throttle expansion process of the heat pump cycle, and when using this, the gas and liquid generated during the expansion process are effectively used. The heat utilization efficiency can be further improved by rotating a screw-type two-phase flow type expander that uses a mixed fluid as the working fluid, and thereby recovering power.

By making the two-phase flow expander of heat pump cycle B a screw type, the pressure difference between the refrigerant inflow side and the outflow side of the expander fluctuates. Even if the installed capacity fluctuates, the volumetric efficiency η remains the same as with other airfoils, centrifugal turbines, and reciprocating engines.
, does not decrease.

Therefore, stable operation is possible. In addition, in order to increase the efficiency of the expansion machine that expands the refrigerant under reduced pressure, it is desirable that the pressure difference between the refrigerant inflow side and the outflow side of the expansion machine be large, but conversely, if this becomes large, the compression ratio of the compressor will increase. This is a disadvantage for conventional turbo type and reciprocating type. On the other hand, the screw type two-phase flow expander used in the present invention is extremely advantageous because its volumetric efficiency η is higher than other turbo type and reciprocating types. In addition, the boiler's high-temperature steam provides driving force. Since the expander is also a screw type and a positive displacement type, the fluctuation in efficiency is small even when conditions change, so the capacity of boiler 1 will fluctuate, and the pressure difference between the inflow of steam into the expander and the outflow side will fluctuate. liquid may occur in the expander, or the boiler capacity may be small.
Efficient operation can be ensured even in cases where a low pressure ratio cannot be obtained due to excessive heat or the boiler capacity is small. For example, if the temperature of the load-side fluid flowing into the condenser (primary heat exchanger) from the return pipe changes due to load fluctuations, the temperature of the fluid flowing into the medium-temperature heat exchanger (secondary heat exchanger) via the communication pipe changes. Since the temperature of the load side fluid also changes,
The temperature and pressure of the exhaust steam flowing from the screw expander of the steam cycle to the medium temperature heat exchanger will also fluctuate.

For example, if the amount of waste heat in a boiler that uses factory waste heat or municipal waste incineration heat changes, the temperature and pressure of the generated steam will also change. In such a case, the steam conditions at the steam outlet or steam inlet of the screw expander in the steam cycle will fluctuate, resulting in fluctuations in the pressure difference between the inflow and outflow sides, but since it is a positive displacement type, it can withstand a wide range of pressure fluctuations. It operates without a significant drop in efficiency and without cavitation or other failures, allowing safe operation.

In the case of conventional airfoil-type or centrifugal steam turbines, performance decreases significantly when the temperature and pressure of the steam generated from the boiler decreases, so a reboiler must be installed to compensate for fluctuations in steam conditions. However, the cost of equipment will inevitably increase. Furthermore, in this invention, the compressor of the heat pump cycle, the two-phase flow expander, and the steam expander of the steam cycle are all screw types, so the machines can be matched well and can respond to load fluctuations with high performance. This improves the operational balance of the entire heat supply system and improves energy usage efficiency.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a heat supply facility implementing the method of the present invention, and FIG. 2 is a Mollier diagram for explaining that the heat pump cycle of the present invention exhibits better performance than the prior art. A... Combined heat steam cycle, B... Heat pump cycle, 2... Screw type expander, 3... Screw type compressor, 4... Screw type two-phase flow expansion machine.

Claims (1)

[Claims] 1. In a heat supply facility consisting of a combination of a heat pump cycle and a cogeneration steam cycle, the screw compressor of the heat pump cycle is driven by the screw expander of the cogeneration steam cycle, and when the liquid refrigerant of the heat pump cycle is throttled and expanded. A method for effectively utilizing energy, characterized in that a screw type two-phase flow expander is rotated using the pressure change, and the screw type compressor is also driven by this rotational force.