JPS61235656A - Heat pump device for heat recovery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the recovery of relatively low-temperature thermal energy as part of energy saving technology in chemical plants, and more specifically, to the recovery of waste heat from steam generated by evaporation and distillation operations. This relates to the effective use of recovered heat by configuring a heat pump using this as a low-temperature heat source and supplying it to other subsequent devices as a high-temperature heat source.

Conventional technology Heat pump devices are known to be based on the compression type and absorption type, and the heat exchanger is used as a method of heat recovery using this, and the enthalpy is increased by suction into the heat compressor, which is used as a heat source. A reuse method is in place. At that time, a liquid film falling type heating can is used as a heat exchanger, and waste heat is supplied to the shell side, water as a heat medium is circulated to the tube side to generate steam, and the steam is sent to a mechanical compressor. It has already been proposed that the latent heat contained in the waste heat is indirectly converted into water vapor and recovered. On the other hand, in the absorption heat pump system, a configuration using a second absorption heat pump in place of the mechanical compressor is also possible.

Problems to be Solved by the Invention When a heat pump device as described above is incorporated into a chemical plant system, and the heat generated in the first device is recovered as a heat source and used as a heat source for the second device, It is necessary to harmonize the operating conditions between both devices; for example, even if both devices are distillation columns of the same type, the operating conditions and operating efficiency of the heat pump device connected in between will be affected by the operating temperature conditions of both columns. Plant systems are also affected. Focusing on the operation of the intermediate heat pump from this perspective, if the amount of vapor at the tops of the front distillation columns increases or decreases, the pressure at the tops of the distillation columns is constant, so the evaporation temperature of the water evaporator changes, The suction amount of the compressor fluctuates and becomes unstable. On the other hand, it must not be overlooked that fluctuations in conditions on the downstream stage of the discharge side of the compressor will have an effect on the suction side. In particular, when the amount of vapor in the first stage distillation column decreases, the temperature of the water evaporator increases, and the suction capacity of the compressor decreases more than the load reduction, which approaches the surging region and causes the compressor to operate in an unstable state. will be done.

In addition, the heat transfer efficiency of the water evaporator is affected by the chemical substances contained in the vapor from the previous stage equipment forming scale on the outer surface of the tube, resulting in a decrease in the overall heat transfer coefficient, which makes stable operation of the heat pump difficult. There was also the drawback that it was not available.

Means for Solving the Problems Therefore, the present invention aims to achieve stable operation of the heat pump device incorporated in the plant system and to harmonize the operating conditions of the devices in the front and rear stages. The device incorporates a temperature or pressure sensor in the heat medium circulation line of the water evaporator, and a controller controls the opening and closing of the control valve in the circulation line. The device is not installed only for heat recovery, but also has the function of matching devices within the system. That is, the amount of heat exchanged by the water evaporator is expressed as Q=A-U·ΔT.

Here, in order to keep the suction pressure of the compressor constant when Q changes, the overall heat transfer coefficient U of the liquid film falling heat exchanger is determined by the rate-determining film heat transfer coefficient in the pipe, and the liquid film The feature is that the U value is adjusted by utilizing the characteristic that U decreases as the amount of flowing sewage increases.

EXAMPLES Hereinafter, preferred examples of the present invention will be explained based on flow sheet drawings.

Shown generally at 10 in FIG. 1 is a falling film heat exchanger. This heat exchanger is a known one, and consists of a vertically long shell 11, tubes 12 consisting of a large number of heat transfer tubes supported above and below the shell, and an evaporator 13 communicating with the lower part of the shell. A circulation pipe 1T of water, which is a heat medium, is configured from the lower part 14 of the shell 11 to the top 16 of the shell 11 via the circulation pump 15. 1B is an inlet for steam from the equipment in the previous stage, and 19 is an outlet for steam condensate, which is returned to equipment I.

Next, 20 is a turbo vapor compressor driven by an electric motor M, and its suction side is connected to the top 21 of the evaporator 13 and the pipe 2.
2, and the discharge side is connected to the next stage device 2 through a pipe 23. Reference numeral 24 indicates a second type absorption heat pump which is added to a part of the pipe 22 as an auxiliary machine to the compressor 20. The thermal compressor 20 itself can also be replaced with a second type absorption heat pump, and in this case an absorption heat pump is formed, but the structure of the above-mentioned heat pump is a known one.

In the present invention, a controller is added to the above configuration. That is, the controller consists of a control valve V provided in the middle of the heat medium water flow path of the circulation pipe 17, a temperature indicating controller TIC for controlling the control valve V, and a sensor S. The controller TIC controls the opening and closing of the valve V based on the value of the sensor S. The temperature controller can also be of the pressure sensing type, in which case the sensor S detects the pressure and the temperature indicating controller TIC is the pressure indicating controller PI.
C is replaced to control valve V.

Operation Since the structure of the present invention is as described above, the present invention will be explained in detail below by referring to specific aspects of the operation of the present apparatus.

The equipment described above is shown as an acetic acid recovery column 30 in a synthetic fiber plant, and the equipment (2) is shown as a methanol distillation column 40. Organic solvent vapor is discharged from the top 31 of the recovery tower 30, and the amount of heat held by the vapor is transferred to the heat exchanger 10.
The solvent is introduced into the shell 110111 from the upper part 18 to raise the temperature of the water flowing inside the heat transfer tube of the tube 12, and the solvent is condensed and returned to the recovery column 30 from the lower part 19 of the shell. In the heat exchanger 10, water passing through the tubes 12 is evaporated on the tube walls, and is ejected into a liquid reservoir at the bottom, where it is separated into gas and liquid in the evaporator 13. The water vapor is sent from the upper part 21 of the evaporator 13 to the vapor compressor 20 via the pipe 22, and the heat retained in the solvent vapor is sent to the compressor. shell 1
It is sent to the upper part 16 of 1 and flows down inside the tube 12 in a thin film,
The heat is exchanged by circulating through the circulation pipe 17. During this period, the amount of solvent vapor passing through the shell 11 decreases as the load decreases, so the boiling point of the water in the water evaporator becomes high (and the specific volume of the vapor decreases, so it is compressed more than the rate of load decrease). The suction vapor capacity of the machine decreases and approaches the compressor surging region, causing a change in conditions on the suction side.

In such a case, the temperature indicating controller TIC detects the change in the temperature of the sensor S and outputs a control signal to increase the opening degree of the control valve V. Therefore, the amount of circulating water is adjusted to increase, and the water is The U value of the evaporator decreases, the boiling point of water in the evaporator becomes constant, and the conditions on the suction side of the compressor 20 are returned to the constant side and stabilized.

Such changes in heat exchange occur not only due to changes in the amount of organic solvent vapor due to fluctuations in the operation of the recovery tower 30 from time to time (but also due to fluctuations associated with relatively long-term scale formation). , Similarly, the valve V can be controlled in both directions as opening or closing using a controller.

Further, regarding fluctuations on the methanol distillation column 40 side, the controller similarly operates in the open and close directions. That is, the compressor 20
If the conditions change on the discharge side of the pipe 22, this fluctuation will appear as a change in the load of the motor M, causing a change on the suction side.
The steam conditions inside the evaporator 13 change via the evaporator, and are similarly detected and controlled by the controller.

Similarly, the operation of this control device not only responds to varying conditions within the system, but also operates effectively with respect to the operating conditions of the heat pump device itself or the plant system containing it. In other words, stability can be maintained even against sudden local fluctuations caused by long-term seasonal setting control in plant environmental conditions.

Effects of the Invention Although the present invention has a simple configuration in which a control device is added to the circulation drive section of the heat pump device as described above,
It is not only a heat pump device that is perfect for its original purpose of heat recovery (but also has a harmonizing function between the devices connected to the front and rear stages, and is capable of handling various fluctuations in the front and rear stages, including the environmental conditions of the plant). It is designed to constantly match the external conditions associated with the plant to ensure stable plant operation.

[Brief explanation of the drawing]

The drawing shows a preferred embodiment of the present invention in the form of a flow sheet, and represents it as part of a plant system including a heat source side and a supply side for heat recovery. 10... Liquid film falling type heat exchanger, water evaporator 11... Shell, 12... Tube, 13... Evaporator,
15...Circulation pump, 17...Circulation pipe, 2
0...vapor compressor, 22.23...pipe, TIC
...Temperature indicating controller, ■...Control valve, S...
・Sensor, engineering...Previous stage equipment, ■...Later stage equipment agent Masao Miyake and one other person αQ

Claims (4)

[Claims] (1) The heat retained in the steam from the previous stage device is introduced into the shell side of the falling film heat exchanger, and is indirectly recovered by replacing it with the retained heat in the steam generated on the tube side, and the recovered steam is converted into steam. It is a heat pump device in which the temperature is raised by a compressor and used as a heat source for other devices in the subsequent stage, and the heat exchanger is a water evaporator, and a circulating heat medium pipe is provided on the tube side of the heat pump, and the heat exchanger is a water evaporator. 1. A heat pump device for heat recovery, characterized in that it is equipped with a control device consisting of a control valve inserted in a passageway and a temperature controller having a sensor for detecting the steam temperature of a water evaporator. (2) The heat pump device according to claim 1, wherein a second type absorption heat pump is interposed between the vapor discharge side of the water evaporator and the suction port of the vapor compressor. (3) The heat pump device according to claim 1, wherein a second type absorption heat pump is installed in place of the vapor compressor. (4) The heat pump device according to claim 1, wherein the control device comprises a control valve and a pressure regulator that senses the pressure inside the water evaporator.