JP2016176604A - Absorption refrigeration machine and controlling method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorption refrigeration machine that at the time of starting, supplies sufficient solution to an exhaust gas heat exchanger to prevent ebullition of solution, even when a float valve opening is made small.SOLUTION: An absorption refrigeration machine 101 includes an evaporator 105, an absorber 106, a condenser 104, a high temperature regenerator 102, a low temperature regenerator 103, an exhaust gas heat exchanger 107, and a pipeline connecting them. In the middle of a solution pipeline in which solution of the absorber flows to the high temperature regenerator via the exhaust gas heat exchanger, provided is a float valve 102b configured to adjust a flow rate of solution. The solution pipeline has a bypass pipeline 124 connecting the upstream side and downstream side of the float valve.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an absorption refrigerator and a control method thereof.

  Conventionally, an absorption refrigerator using, for example, a lithium bromide aqueous solution as an absorbent and water as a refrigerant is generally known. In the absorption refrigerator cycle, in order to regenerate the solution that has absorbed the refrigerant, heat is applied to the solution from a heating source and the refrigerant is evaporated to concentrate. A combustion gas generated by a burner is used as a heating source, and a heating operation can be performed, which is called a direct-fired absorption refrigerator, and is widely used as a heat source for air conditioning. In addition, since the absorption chiller can use various heat sources, high-temperature combustion exhaust gas discharged from the gas turbine can be driven as a heat source.

  In order to increase the energy efficiency of such an absorption refrigerator, it is desirable to provide an exhaust gas heat exchanger that recovers heat from the exhaust gas after the heat is applied by the high-temperature regenerator. For example, there is a triple effect absorption refrigerator proposed in Patent Document 1.

  The triple effect absorption refrigerator will be described below.

  High temperature regenerator, medium temperature regenerator and low temperature regenerator, condenser, absorber, evaporator, multiple solution heat exchangers, solution piping and refrigerant piping connecting these devices, solution pump for circulating the solution and refrigerant in the cycle And a refrigerant pump, and has a structure in which a pipe for sending a dilute solution from the absorber in parallel to at least the high temperature regenerator and the low temperature regenerator is provided. The high-temperature regenerator is a once-through type, and includes a burner that burns fuel, a heat transfer tube group that is concentrically arranged around the burner and heats and concentrates the solution.

  The dilute solution that has flowed into the high-temperature regenerator is introduced into the heat transfer tube, heated and concentrated by heat exchange with the combustion gas to become a concentrated solution, and then installed along with the generated refrigerant vapor at the outlet of the high-temperature regenerator. Led to the gas-liquid separator. Then, it is separated from the refrigerant vapor in the gas-liquid separator. The concentrated solution separated from the refrigerant vapor by the gas-liquid separator is sent to the float box and from there to the high temperature heat exchanger.

  On the other hand, the dilute solution sent to the high temperature heat exchanger exchanges heat with the concentrated solution and rises in temperature. Further, the dilute solution sent to the exhaust gas heat exchanger heats up with the combustion gas after being used for heating the high-temperature regenerator and rises in temperature. These dilute solutions join together and flow into the high-temperature regenerator through a float valve installed in the float box. This float valve is a flow rate adjusting means for adjusting the amount of dilute solution sent to the high temperature regenerator according to the level of the concentrated solution in the float box. That is, the solution sent from the high temperature regenerator changes the liquid level of the float box, the float valve is driven according to the amount of change in the liquid level, and the dilute solution is sent to the high temperature regenerator.

JP 2004-132553 A

  When the absorption refrigerator is started, the system is operated with a small amount of solution circulation. Since the pressure difference between the high-temperature regenerator and the absorber is small at the time of startup, the amount of solution circulation is suppressed to a small amount. It is a float valve that adjusts the amount of solution circulation. That is, when the absorption refrigerator is started, the opening degree of the float valve is reduced in order to reduce the amount of solution circulation.

  Moreover, in the connection system of solution piping currently disclosed by patent document 1, when the amount of solution circulation is small, the amount of solution circulation sent to an exhaust gas heat exchanger is also suppressed to a small amount. The exhaust gas heat exchanger uses the exhaust gas after burning in the high-temperature regenerator as a heating source. When heat exchange with a relatively high temperature exhaust gas is performed for a small amount of solution, The solution may boil. The solution boiling leads to a problem that the pressure loss of the solution flow path increases due to the retention of bubbles generated at that time, and further the efficiency of the refrigerator decreases.

  An object of the present invention is to supply a sufficient solution to the exhaust gas heat exchanger and prevent boiling of the solution even when the float valve opening is small when the absorption refrigerator is started.

  The absorption refrigerator of the present invention includes an evaporator, an absorber, a condenser, a high-temperature regenerator, a low-temperature regenerator, an exhaust gas heat exchanger, and a pipe connecting them, and the solution of the absorber passes through the exhaust gas heat exchanger. A float valve for adjusting the flow rate of the solution is provided in the middle of the solution pipe toward the high-temperature regenerator, and the solution pipe has a bypass pipe that connects the upstream side and the downstream side of the float valve.

  According to the present invention, when the absorption refrigerator is started, even when the float valve opening is small, a sufficient solution can be supplied to the exhaust gas heat exchanger to prevent boiling of the solution.

1 is a schematic configuration diagram illustrating an absorption refrigerator of Example 1. FIG. FIG. 3 is a schematic configuration diagram illustrating an absorption refrigerator according to a second embodiment.

  Hereinafter, means used in the absorption refrigerator according to the embodiment of the present invention will be described.

  The first means comprises a high-temperature regenerator that mainly uses the combustion heat of the burner as a drive source and controls the supply amount of the solution by a float valve, and an exhaust gas heat exchanger downstream of the high-temperature regenerator. In the absorption chiller, a bypass pipe that bypasses the solution is connected from the middle of the outlet side solution pipe of the exhaust gas heat exchanger to the middle of the outlet side solution pipe of the float valve. Due to the structure, a fixed amount of solution is always supplied to the exhaust gas heat exchanger regardless of the float valve opening.

  The second means is to install a flow rate adjusting valve (hereinafter also referred to as “flow control valve”) in the middle of the bypass pipe and a solution temperature sensor in the middle of the outlet side solution pipe of the exhaust gas heat exchanger. To do. The solution boiling temperature is set in advance from the relationship between the exhaust gas temperature and the solution temperature. Next, the opening degree of the flow control valve is controlled based on the measurement result of the solution temperature so that the solution temperature inside the exhaust gas heat exchanger does not exceed the set value. By this method, a sufficient solution is always supplied to the exhaust gas heat exchanger regardless of the opening degree of the float valve.

  The temperature measurement is not limited to the solution temperature, and the flow control valve may be controlled by the inlet exhaust gas temperature of the exhaust gas heat exchanger.

  By controlling the opening degree of the flow control valve of the solution bypass pipe based on the temperature measurement result of the outlet solution of the exhaust gas heat exchanger by the first and second means, and ensuring a sufficient amount of solution circulation, the exhaust gas The solution boiling inside the heat exchanger can be prevented, and the heat of the exhaust gas can be efficiently recovered. That is, since the heat recovered in the solution is used as a drive source for the absorption chiller, the refrigeration capacity is increased and the efficiency of the absorption chiller is improved.

  In this specification, the term “absorption refrigerator” will be used for explanation, but the present invention includes what are called “absorption chiller / heater” and “absorption heat pump”.

  Hereinafter, the absorption refrigerator according to the present invention will be described with reference to examples.

  FIG. 1 shows a schematic configuration of an absorption refrigerator according to the first embodiment.

  In this figure, the absorption refrigerator 101 includes a high temperature regenerator 102, a low temperature regenerator 103, a condenser 104, an evaporator 105, and an absorber 106. The high temperature regenerator 102 is provided with a float chamber 102a and a float valve 102b. In addition, the absorption refrigerator 101 includes, as peripheral devices, an exhaust gas heat exchanger 107, a high-temperature heat exchanger 108, a low-temperature heat exchanger 109, a solution pump (bound) 110a, a solution pump (return) 110b, a refrigerant pump 111, cooling A cooling tower (not shown) for releasing the heat of water to the atmosphere and piping for connecting them are provided.

  During operation of the absorption chiller 101, a high vacuum pressure is usually maintained. Further, the vapor pressure decreases in the order of the high temperature regenerator 102, the low temperature regenerator 103, the condenser 104, the evaporator 105, and the absorber 106.

  Hereinafter, description will be made on the assumption that the refrigerant used in the absorption refrigerator 101 is water and a lithium bromide aqueous solution is used as the solution. However, the same effect can be obtained with other refrigerants and solutions.

  The refrigerant vapor generated in the high temperature regenerator 102 and the low temperature regenerator 103 is sent to the condenser 104 through the pipe 113 and the passage 114. In the condenser 104, the refrigerant vapor condenses and becomes a liquid, passes through the pipe 115, and is sent to the evaporator 105.

  The refrigerant sent to the evaporator 105 passes through the pipe 116 by the refrigerant pump 111 and is sprayed from the upper part of the evaporator 105. The sprayed refrigerant evaporates inside the evaporator 105 maintained at a high degree of vacuum, takes away the latent heat of evaporation at that time, and lowers the temperature of the cold water passing through the pipe 117. And the cold water 118 which temperature fell from the evaporator 105 is taken out, and it supplies to load side (not shown), such as an air conditioner.

  The refrigerant vapor evaporated in the evaporator 105 is sent to the absorber 106, and then the refrigerant vapor is absorbed by a relatively high concentration solution (concentrated solution) sent from the high temperature regenerator 102 and the low temperature regenerator 103. The A relatively low concentration solution (diluted solution) that has absorbed the refrigerant vapor is sent to the high temperature regenerator 102 by the solution pump 110a. The dilute solution sent to the high-temperature regenerator 102 is heated and concentrated by the heat obtained by the combustion of fuel such as city gas and kerosene in the burner 119. The refrigerant vapor generated at that time passes through the pipe 113 and is sent to the condenser 104 again.

  Since the dilute solution sent to the high temperature regenerator 102 has a solution temperature as high as possible and the solution temperature of the concentrated solution sent to the absorber 106 needs to be as low as possible, the low temperature heat exchanger 109 and the high temperature heat exchanger 108 are used to concentrate the solution. Heat exchange is performed between the solution and the dilute solution. Further, a part or all of the dilute solution going to the high temperature regenerator 102 is sent to the exhaust gas heat exchanger 107 via the branched pipe 120 and further heated by the exhaust gas 121 sent from the high temperature regenerator 102. By doing so, more heat of the exhaust gas 121 can be recovered and the refrigeration capacity can be improved.

  As described above, the refrigerant is transported by the solution, and it is possible to continue generating cold while repeating evaporation and condensation.

  Next, the flow of the solution when starting up the absorption refrigerator 101 will be described.

  The dilute solution collected at the bottom of the absorber 106 is sent to the high temperature regenerator 102 by a solution pump (bound) 110a. The dilute solution exiting the low temperature heat exchanger 109 is branched and sent to the high temperature heat exchanger 108 and the exhaust gas heat exchanger 107. A part of the rare solution exiting the high-temperature heat exchanger 108 is sent to the low-temperature regenerator 103, and the rest is sent to the high-temperature regenerator 102. On the way, it merges with the diluted solution heated by the exhaust gas heat exchanger 107 and is sent to the high temperature regenerator 102. The diluted solution is sent to the high temperature regenerator 102 through the float valve 102b. The concentrated solution heated and concentrated in the high temperature regenerator 102 is sent to the absorber 106 by the solution pump 110b.

  The amount of the concentrated solution discharged from the float chamber 102a controls the dilute solution supplied to the high temperature regenerator 102 by adjusting the opening of the float valve 102b corresponding to the liquid level 102d detected by the float 102c. .

  However, since the pressure difference between the high-temperature regenerator 102 and the absorber 106 is small when the absorption refrigerator 101 is started, a sufficient amount of solution circulation cannot be ensured only by the driving force of the solution pump 110b. Therefore, since the liquid level 102d of the float chamber 102a does not change, the opening degree of the float valve 102b does not change, and the circulation amount of the solution does not increase. That is, as described above, when the absorption refrigerator 101 is started, the amount of solution circulation is reduced. For this reason, the solution supply amount of the exhaust gas heat exchanger 107 is also reduced. And since the quantity of the solution supplied to the exhaust gas heat exchanger 107 is not sufficient with respect to the amount of heat of the high temperature exhaust gas 121, the solution boils and the solution is less likely to flow. As a result, the performance of the absorption chiller 101 is degraded.

  Therefore, in the present embodiment, the solution pipe 122 that goes from the exhaust gas heat exchanger 107 toward the upstream side of the float valve 102b and the solution pipe 123 that is downstream of the float valve 102b are connected by the bypass pipe 124, and the float valve 102b is connected. Regardless of the opening, the dilute solution is always sent to the high temperature regenerator 102. In other words, the solution pipe 122 is provided with a bypass pipe 124 that connects the upstream side and the downstream side of the float valve 102b. As a result, a certain amount of a rare solution can be supplied to the exhaust gas heat exchanger 107 even at the time of startup. That is, a sufficient solution supply amount can be secured in the exhaust gas heat exchanger 107.

  Note that an orifice may be provided in the bypass pipe 124 according to the capacity of the high-temperature regenerator 102.

  In the present embodiment, the bypass pipe 124 does not have a valve, and therefore is always open. For this reason, it is desirable that the flow path resistance of the bypass pipe 124 be in an appropriate range. For example, when the flow rate of the solution from the bypass pipe 124 is higher than the flow rate of the solution flowing into the high temperature regenerator 102 via the float valve 102b at the rated time, the amount of the solution flowing into the high temperature regenerator 102 is appropriately set. It becomes impossible to adjust. Therefore, in this case, the flow path resistance of the bypass pipe 124 is made larger than the flow path resistance at the rated opening of the float valve 102b, and priority is given to the inflow of the solution from the flow path via the float valve 102b. desirable. On the other hand, at the time of activation, the float valve 102b is almost closed. At this time, it is desirable that the flow path resistance of the bypass pipe 124 is made smaller than the flow path resistance in a state where the float valve 102 b is almost closed, and priority is given to the inflow of the solution via the bypass pipe 124.

  FIG. 2 shows a schematic configuration of the absorption refrigerator according to the first embodiment.

  In this embodiment, a flow control valve 201 (flow rate adjusting valve) is installed in the middle of the bypass pipe 124 of the first embodiment, and the temperature sensor 202 (solution temperature sensor) is connected to the outlet side solution pipe 122 of the exhaust gas heat exchanger 107. Is installed. Since other than this is the same as in the first embodiment, the description is omitted.

  The temperature sensor 202 measures the solution temperature after being heated by the exhaust gas heat exchanger 107. The measured solution temperature is sent to the control unit 203 to control the opening degree of the flow control valve 201.

  The state in which the solution is relatively easy to boil inside the exhaust gas heat exchanger 107 is a case where the solution flow rate is small and heat is exchanged with high-temperature exhaust gas. Therefore, the temperature of the solution is constantly measured, and when the measurement result approaches the boiling temperature, the control unit 203 determines that “there is a possibility of boiling”, and increases the opening of the flow control valve 201 to increase the solution flow rate. Increase. By the control, boiling of the solution in the exhaust gas heat exchanger 107 can be avoided, and an increase in pressure loss of the solution flow can be prevented. Furthermore, more heat of the exhaust gas 121 can be recovered in the solution, and the efficiency of the absorption refrigerator 101 is improved.

  In order to realize the control, the solution boiling temperature is obtained in advance from the relationship between the exhaust gas temperature, the solution temperature, and the solution pressure. Although not shown, it is desirable to provide an exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the inlet of the exhaust gas heat exchanger 107 between the high temperature regenerator 102 and the exhaust gas heat exchanger 107.

  In addition, although the opening degree control of the flow control valve 201 based on the measurement result of the solution temperature is described in the present embodiment, when the temperature relationship between the two is obtained in advance, based on the measurement result of the exhaust gas temperature. You may control.

  Further, the opening degree of the flow control valve 201 may be adjusted based on the temperature measured by the temperature sensor 202 (solution temperature sensor) and the exhaust gas temperature sensor.

  In summary, the control method in this embodiment includes a step of measuring the temperature of the solution by the solution temperature sensor and a step of adjusting the opening of the flow rate adjustment valve based on the temperature measured by the solution temperature sensor.

  Further, the control method in the present embodiment includes a step of measuring the temperature of the solution with the solution temperature sensor, the temperature of the exhaust gas with the exhaust gas temperature sensor, and the flow rate based on the temperature measured with the solution temperature sensor and the exhaust gas temperature sensor. And a step of adjusting the opening of the adjusting valve.

  Next, a flow control valve control method in the present embodiment will be described using Table 1.

  Table 1 summarizes the relationship between the operating state and the opening of the flow control valve. The operating state is shown separately at startup and at rated load. Furthermore, at the time of start-up, it is shown separately according to the magnitude relationship between T and To.

  Here, T represents a set temperature at which the solution does not boil, and To represents the outlet side solution temperature of the exhaust gas heat exchanger 107.

  As shown in this table, the opening degree of the flow control valve 201 is reduced under the condition of To <T when the absorption refrigerator 101 is started. Particularly in the early stage of startup, the burner 119 has a small combustion amount, the pressure of the high-temperature regenerator 102 is low, and the pressure difference between the high-temperature regenerator 102 and the absorber 106 is small, so the flow rate of the concentrated solution flowing out from the high-temperature regenerator 102 is high. It remains few. If the opening degree of the flow control valve 201 is increased in this state, many rare solutions are sent to the high temperature regenerator 102 and the capacity of the refrigerator does not increase.

  Then, after a certain period of time has elapsed after startup, the amount of combustion of the burner 119 increases, and the opening degree of the flow control valve 201 is increased under the condition of To ≧ T. In this state, the pressure of the high-temperature regenerator 102 is high due to the increase in the burner combustion amount, and the pressure difference between the high-temperature regenerator 102 and the absorber 106 becomes large. Become. Accordingly, the liquid level 102d of the float chamber 102a is lowered, and the float valve 102b is opened in conjunction with this, and the flow rate of the rare solution sent to the high temperature regenerator 102 is increased. At the same time, it is necessary to increase the flow rate of the rare solution supplied to the exhaust gas heat exchanger 107 in order to cope with the exhaust gas temperature rise accompanying the increase in the burner combustion amount. Therefore, the opening degree of the flow control valve 201 is increased.

  Thereafter, when the operation is shifted to the rated load operation state, the burner 119 is also burned at the rated state at that time, and the concentrated solution and the rare solution are diluted by the pressure difference between the high temperature regenerator 102 and the absorber 106 and the driving force of the solution pump 110b. The circulation amount of the solution is balanced and a predetermined refrigeration capacity can be maintained. In this state, since the solution circulation can be maintained only by controlling the float valve 102b, the opening degree of the flow control valve 201 may be reduced. Furthermore, when the rated operation state continues stably, the flow control valve 201 may be closed. However, it is desirable to always measure the solution temperature in consideration of switching to partial load operation.

  As described above, by performing the solution circulation control shown in Table 1 in the absorption refrigerator having the solution piping structure shown in FIG. 2, even when the amount of solution circulation is small at the start-up of the absorption refrigerator 101, the exhaust gas heat A large amount of dilute solution can be supplied to the exchanger 107. Thereby, the boiling of the solution inside the exhaust gas heat exchanger 107 can be avoided, and an increase in pressure loss due to the solution flow inside can be prevented.

  To summarize the control method based on Table 1, when starting up, when the temperature of the solution is a temperature at which the solution does not boil and is lower than a preset temperature, the opening of the flow control valve is reduced, and the temperature of the solution is reduced. However, when the temperature is such that the solution does not boil and is equal to or higher than a preset temperature, the opening of the flow rate adjustment valve is increased. And at the time of rated load, the opening degree of a flow regulating valve is made small or closed.

  101: Absorption refrigerator, 102: High temperature regenerator, 102a: Float chamber, 102b: Float valve, 102c: Float, 103: Low temperature regenerator, 104: Condenser, 105: Evaporator, 106: Absorber, 107: Exhaust gas heat exchanger, 108: high temperature heat exchanger, 109: low temperature heat exchanger, 110a: solution pump (going), 110b: solution pump (returning), 111: refrigerant pump, 113: refrigerant piping, 114: passage, 115 : Refrigerant pipe, 116: refrigerant pipe, 117: cold water pipe, 118: outlet cold water, 119: burner, 120: solution pipe, 121: exhaust gas, 122, 123: solution pipe, 124: bypass pipe, 201: flow control valve, 202: Solution temperature sensor, 203: Control unit.

Claims (6)

Including an evaporator, an absorber, a condenser, a high-temperature regenerator, a low-temperature regenerator, and an exhaust gas heat exchanger, and piping connecting them,
A float valve for adjusting the flow rate of the solution is provided in the middle of the solution pipe where the solution of the absorber goes to the high temperature regenerator via the exhaust gas heat exchanger,
The solution pipe is an absorption chiller having a bypass pipe that connects an upstream side and a downstream side of the float valve. The bypass pipe has a flow rate adjustment valve,
The solution pipe is provided with a solution temperature sensor for measuring the temperature of the solution at the outlet of the exhaust gas heat exchanger,
The absorption refrigerator according to claim 1, wherein the opening degree of the flow rate adjusting valve is configured to be adjusted based on a temperature measured by the solution temperature sensor. The bypass pipe has a flow rate adjustment valve,
The solution pipe is provided with a solution temperature sensor for measuring the temperature of the solution at the outlet of the exhaust gas heat exchanger,
Between the high temperature regenerator and the exhaust gas heat exchanger, an exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the inlet of the exhaust gas heat exchanger is attached,
The absorption chiller according to claim 1, wherein the opening degree of the flow rate adjusting valve is configured to be adjusted based on a temperature measured by the solution temperature sensor and the exhaust gas temperature sensor. Including an evaporator, an absorber, a condenser, a high-temperature regenerator, a low-temperature regenerator, and an exhaust gas heat exchanger, and piping connecting them,
A float valve for adjusting the flow rate of the solution is provided in the middle of the solution pipe where the solution of the absorber goes to the high temperature regenerator via the exhaust gas heat exchanger,
The solution pipe has a bypass pipe connecting the upstream side and the downstream side of the float valve,
The bypass pipe has a flow rate adjustment valve,
The solution pipe is provided with a solution temperature sensor for measuring the temperature of the solution at the outlet of the exhaust gas heat exchanger, and is a method for controlling an absorption refrigerator,
Measuring the temperature of the solution with the solution temperature sensor;
And a step of adjusting the opening of the flow rate adjustment valve based on the temperature measured by the solution temperature sensor. Including an evaporator, an absorber, a condenser, a high-temperature regenerator, a low-temperature regenerator, and an exhaust gas heat exchanger, and piping connecting them,
A float valve for adjusting the flow rate of the solution is provided in the middle of the solution pipe where the solution of the absorber goes to the high temperature regenerator via the exhaust gas heat exchanger,
The solution pipe has a bypass pipe connecting the upstream side and the downstream side of the float valve,
The bypass pipe has a flow rate adjustment valve,
The solution pipe is provided with a solution temperature sensor for measuring the temperature of the solution at the outlet of the exhaust gas heat exchanger,
Between the high-temperature regenerator and the exhaust gas heat exchanger, an exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the inlet of the exhaust gas heat exchanger is attached, the method for controlling an absorption refrigerator,
Measuring the temperature of the solution with the solution temperature sensor, and measuring the temperature of the exhaust gas with the exhaust gas temperature sensor;
Adjusting the opening of the flow rate adjustment valve based on the temperature measured by the solution temperature sensor and the exhaust gas temperature sensor. When starting up,
When the temperature of the solution is a temperature at which the solution does not boil and is lower than a preset temperature, the opening of the flow rate adjustment valve is reduced,
The control method for an absorption chiller according to claim 4 or 5, wherein when the temperature of the solution is a temperature at which the solution does not boil and is equal to or higher than a preset temperature, the opening of the flow rate adjustment valve is increased. .

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