Exhaust Heat Recovery System

The present invention relates to an exhaust heat recovery system.

The effective use of thermal energy has become increasingly important in recent years due to energy conservation and environmental issues.

Patent Document 1 discloses a heat recovery compressor and a centralized control device for the purpose of efficiently using energy.

In the system of Patent Document 1, exhaust heat is not recovered from some gas compressors, and there is room for further improvement from the viewpoint of effective use of thermal energy contained in the exhaust heat. Further, the configuration described in Patent Document 1 assumes that a part of the gas compressor is not connected to the exhaust heat recovery device. Therefore, the situation in which all gas compressors are connected to the waste heat recovery device is not considered.

Therefore, an object of the present invention is to effectively utilize thermal energy in a system in which all gas compressors are connected to a exhaust heat recovery device.

An example of the means for solving the above problem is as follows.

An exhaust heat recovery system comprising: a plurality of gas compressors; a exhaust heat recovery equipment; and a controller, wherein further comprising a exhaust heat recovery path connecting the plurality of gas compressors and the exhaust heat recovery equipment, and the plurality of gas compressors can select whether or not to use the exhaust heat recovery path based on instructions from the controller,

According to the present invention, thermal energy can be efficiently recovered by recovering exhaust heat from all gas compressors constituting the system.

Further composition and effects of the present invention will become apparent through the entire text of the specification below.

The exhaust heat recovery system according to the present invention includes a gas compressor that generates compressed gas, a exhaust heat recovery device that recovers heat generated in the process of generating compressed gas, and a control device that oversees them. And carrying out operation in accordance with the parameters for operation.

In this specification, the gas compressor has an electric motor that drives the compressor body. Then, a gas compressor that mechanically controls loading (making compressed air) and unloading (waiting in non-making air operation) by driving an electric motor is called a constant speed machine.

In a gas compressor, a gas compressor that controls the rotational speed of an electric motor by changing the operating frequency by an inverter is called a variable speed machine. In addition, when the variable speed machine operates the rotational speed of the electric motor at full speed according to the command of the control device or control device, it is called full-speed operation.

According to the operating parameters, the gas compressor first operates a frequency-controlled variable speed machine, then a full-speed operation machine, and finally a constant-speed machine. And stopping in the same order.

In the embodiment described below, as an example, a exhaust heat recovery system including four gas compressors, one exhaust heat recovery device, and one control device that controls them will be described.

is a block diagram showing the configuration of the present invention. The exhaust heat recovery equipmentis connected to the gas compressorvia an output pipingthat supplies the heat transfer fluid to the gas compressorand a return pipingthat captures the heat transfer fluid from the gas compressor. Heat is exchanged between the circulating water taken in from the input pipingand the heat transfer fluid. The hot water obtained by the heat exchange is supplied via the output piping. The controllerincludes a signal linefor performing RS 485 communication with the exhaust heat recovery equipmentand a signal linefor performing RS 485 communication with the gas compressor. And from the operating state and temperature of the gas compressor, the controllertakes charge in control of this invention and control each device according to the program stored inside. The partition solenoid valveopens and closes according to the command of the exhaust heat recovery equipmentto prevent heat transfer fluid from flowing to the gas compressor that is not subject to exhaust heat recovery. The check valveprevents the heat transfer fluid returning to the exhaust heat recovery equipmentfrom flowing back to the gas compressor.is the air tank that stores the compressed air generated by the gas compressor. In addition, in, the controlleris separately disposed from the exhaust heat recovery equipment, but the case where it is configured as an integral part is also within the scope of the disclosure of this embodiment.

In the present invention, a exhaust heat recovery path is constructed between the gas compressorand the exhaust heat recovery equipmentby the output pipingand the return piping. The exhaust heat at this time means the heat generated in the gas compressordue to the operation of the gas compressor. Therefore, by recovering the heat generated in the gas compressorby this exhaust heat recovery path, energy efficiency is improved.

At the same time, the recovery of this heat also functions as a cooling loop of the gas compressor. Therefore, in some cases, it is possible to reduce the scale of the heat dissipation mechanism to be provided in the gas compressor, and in such a case, it also contributes to reducing the cost of the gas compressoritself.

The gas compressorin the present invention is configured so that it is possible to select whether or not to use a exhaust heat recovery path. This selection can be realized based on instructions from the controller, for example, by opening and closing a valve provided in the exhaust heat recovery path in the gas compressor.

In addition, the case where a valve is provided between the gas compressorand the exhaust heat recovery equipment, and the use or non-use of the exhaust heat recovery path can be selected by opening and closing the valve is also included in the scope of the present invention.

In the configuration of, first, for example, the controllercompares the set required water temperature with the supply water temperature, which is the temperature of the supply water supplied from the exhaust heat recovery equipmentto the outside by the output piping. When the supply water temperature is lower than the required water temperature, a exhaust heat recovery system can be realized by instructing at least one of the plurality of gas compressors to use the exhaust heat recovery path.

is an example in which the controllerperforms whether or not to use the exhaust heat recovery path by controlling the opening and closing of the partition solenoid valve.

By means of the signal line, the controllercontrols the opening and closing of the partition solenoid valvecorresponding to the gas compressor to be indicated, and as a result, at least one of the plurality of gas compressors is instructed to use the exhaust heat recovery path. Thus, exhaust heat recovery system can be realized.

As shown inand, for example, in the present invention, specification, the expression “the gas compressor can be selected based on instructions from the controller whether or not to use the exhaust heat recovery path”, or, various expressions such as “instructing at least one of the gas compressor to use the exhaust heat recovery path”, even if it is realized by instructing the gas compressor itself, or by opening and closing the valve of the exhaust heat recovery path in the middle, the technical concept is substantially the same. For this reason, as an expression that includes both instructions to the gas compressor itself and instructions to valves and the like in any case, for example, the expression “the gas compressor can be selected based on instructions from the controller whether or not to use the exhaust heat recovery path”, or the expression “at least one of the gas compressor is instructed to use the exhaust heat recovery path” is used.

is a flowchart illustrating the operation of the present invention. The operation based on the flowchart is as follows.

Stepis a process for determining the presence or absence of the gas compressorin a stop according to the internal program of the controller. Specifically, the controllerperforms RS 485 communication with the gas compressorand acquires the operating state. If there is a stopped gas compressor, the process proceeds to step. If there is no stopped gas compressor, the process proceeds to step.

Stepis a process of stopping the exhaust heat recovery effective from the exhaust heat recovery equipmentwith respect to the stopped gas compressor. Specifically, by closing the partition solenoid valvecorresponding to the stopped gas compressorby the command of the exhaust heat recovery equipment, the supply of heat transfer fluid supplied from the exhaust heat recovery equipmentto the gas compressorvia the output pipingis cut off.

In the present invention, the partition solenoid valveincludes both cases of being incorporated into the gas compressoror being placed separately.

Stepis a process for determining whether or not exhaust heat recovery is necessary according to the internal program of the exhaust heat recovery equipment. Specifically, the user can set the necessity of exhaust heat recovery in the operation of the exhaust heat recovery equipment, and the setting value is recorded in the internal memory of the exhaust heat recovery equipment. If it is determined that exhaust heat recovery is necessary, the process proceeds to step. If it is determined that exhaust heat recovery is not necessary, the process is ended.

Stepis a process for determining whether or not the required amount of heat can be recovered by exhaust heat recovery according to the internal program of the exhaust heat recovery equipment. Specifically, in the operation of the exhaust heat recovery equipment, the user can set the required water temperature, and the setting value is recorded in the internal memory of the exhaust heat recovery equipment. The exhaust heat recovery equipmentacquires the temperature of the water temperature from the internal temperature sensor, and determines by comparing it with the required water temperature set by the user. If it is determined that the water temperature required by the user is satisfied, the process proceeds to step. If it is determined that the water temperature is not satisfied, the process proceeds to step.

Stepis a process for determining whether or not the amount of heat being recovered is excessive for the water temperature required by the user according to the internal program of the exhaust heat recovery equipment. Specifically, it is calculated and determined whether or not the water temperature obtained from the temperature sensor is rising by comparing it with the required water temperature set by the user. If it is determined that the amount of heat is excessive, the process proceeds to step. If it is determined that the amount of heat is not excessive, the process is ended.

Stepis a process for reducing the gas compressorto be recovered with exhaust heat. Specifically, by closing the partition solenoid valvecorresponding to the gas compressorto be recovered with the command of the exhaust heat recovery equipment, the supply of heat transfer fluid supplied from the exhaust heat recovery equipmentto the gas compressorvia the output pipingis cut off, and the process is ended.

Stepis a process of increasing the gas compressorto be recovered from exhaust heat. Specifically, by opening the partition solenoid valvecorresponding to the gas compressorto be recovered with the command of the exhaust heat recovery equipment, the heat transfer fluid is supplied from the exhaust heat recovery equipmentto the gas compressorvia the output piping, and the process is ended.

is a flowchart showing a process for determining the priority of which of the plurality of gas compressorsto perform exhaust heat recovery for when the process of stepis executed in. This is an example of the details of the contents to be executed in step.

Stepis a process in which the controlleracquires the operating state of the gas compressorvia RS 485 communication via the signal line.

Steprefers to the operating state acquired in stepand is a process of determining loading or unloading according to the internal program of the controller. In the case of loading, proceed to step. In the case of unloading, proceed to step.

Stepis a process of determining whether or not there is a constant-speed gas compressoraccording to the internal program of the controller. Specifically, in the operation of the controller, the user registers in advance whether the gas compressorconnected to the controlleris a constant speed or a variable speed, and the setting value is recorded in the internal memory of the controller. If there is a constant-speed gas compressor, the process proceeds to step. If not, proceed to step.

Stepis a process in which the controllerdetermines whether or not there is a variable speed gas compressorand in full speed operation according to an internal program. Specifically, in the operation of the controller, the user registers in advance whether the gas compressorconnected to the controlleris frequency control or full-speed operation, and the setting value is recorded in the internal memory of the controller. If there is a gas compressorin full-speed operation, the process proceeds to step. If not, proceed to step.

Steprefers to the operating state acquired in stepand determines whether or not there is a gas compressorhaving a rotation speed less than the number of revolutions required for exhaust heat recovery according to an internal program. Specifically, the operating state of the inverter inside the gas compressoris acquired by the controllervia RS 485 communication, and judge by comparing required water temperature recorded in the internal memory and the minimum operating frequency X [Hz] of the electric motor required for exhaust heat recovery calculated by the internal program. If there is a gas compressorhaving an operating frequency of the electric motor less than X [Hz], the process proceeds to step. If not, proceed to step.

Steprefers to the operating state acquired in stepand is a process for determining whether or not there is a gas compressorthat exceeds the rotation speed required for exhaust heat recovery according to an internal program. The specific process is the same as in step. If there is a gas compressorhaving an operating frequency of X [Hz] or higher of the electric motor, the process proceeds to step. If not, proceed to step.

In step, by processing stepsand, in the configuration of the gas compressor in the present invention, it can be seen that the gas compressorhaving an electric motor operating frequency of less than X [Hz] and the gas compressorhaving an electric motor operating frequency of X [Hz] or more are mixed. Since the gas compressorhaving an operating frequency of the electric motor of less than X [Hz] is considered to have a small amount of heat that can be recovered even in a loaded state, and by removing such a gas compressor from the exhaust heat recovery target, it is a process to recover exhaust heat by giving priority to the gas compressorhaving a large amount of heat.

In step, since the gas compressorduring full-speed operation has a larger amount of heat that can be recovered compared to the gas compressorduring rotation control, the gas compressorother than the gas compressorduring full-speed operation is excluded from the exhaust heat recovery target.

In step, since the gas compressorof the constant speed is stopped after the gas compressorof the variable speed, the possible exhaust heat recovery time is long, and stable exhaust heat recovery is possible, by removing the gas compressorother than the gas compressorof the constant speed from the exhaust heat recovery, exhaust heat is recovered in priority from the gas compressorof the constant speed machine.

In step, when the exhaust heat cannot be recovered and the water temperature required by the user cannot be satisfied, guidance of “less than the set temperature” is displayed on the display of the controller, and the process is ended.

Stepstarts exhaust heat recovery by opening the partition solenoid valvecorresponding to the gas compressorthat stops at the end according to the internal program of the controller. The specific process is the same as in step. By setting the gas compressorto stop at the end, it is possible to secure a long time for exhaust heat recovery.

is a flowchart showing a process for determining the priority of stopping exhaust heat recovery for which of the plurality of gas compressorswhen the process of stepis executed in. This is an example of the details of the contents of stepof.

Stepis a process in which the controlleracquires the operating state of the gas compressorvia RS 485 communication via the signal line.

Stepis a process of determining whether or not there is a gas compressorunder frequency control according to the internal program of the controller. The specific process is the same as in step. If there is a gas compressorunder frequency control, the process proceeds to step. If not, proceed to step.

Stepis a process in which the gas compressorduring frequency control is set to a target of priority exhaust heat recovery stopping, as the gas compressorduring frequency control is difficult to do stable exhaust heat recovering since the amount of heat varies depending on the operating conditions

Stepstops exhaust heat recovery by closing the partition solenoid valvecorresponding to the gas compressorthat first stops according to the internal program of the controller. The specific process is the same as in step. By leaving the gas compressorthat stops at the end, it is possible to secure a long time for exhaust heat recovery.