JPH0437345B2 - - Google Patents

Description

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

Conventional technology It is known that heat pump devices are based on compression type and absorption type, and the heat exchanger is used as a method of heat recovery using this type of heat pump, and the enthalpy is increased by suction into a heat compressor, which is used as a heat source. A reuse method is being used. At this 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 type 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 the two devices. For example, even if both devices are the same type of distillation tower, the operating temperature conditions of both columns will affect the operating conditions and operating efficiency of the heat pump device connected in between. 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 remains 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, so it approaches the surging region.
The compressor will be operated in an unstable condition.
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 outside surface of the tube, resulting in a decrease in the overall heat transfer coefficient, making it difficult for the heat pump to operate stably. There was also the drawback that it was not available.

Means for Solving the Problem Therefore, the present invention provides stable operation of the heat pump device incorporated in the front-stage device and the other device in the rear-stage,
A water evaporator control device is built into the heat pump device in order to harmonize the operating conditions of the front and rear devices, and a temperature or pressure sensor is installed in the heat medium circulation pipe of the water evaporator. The main idea is to control the opening and closing of the control valves in the circulation pipes using a controller, and instead of installing the heat pump device only in the heat circuit, it also has the function of matching devices within the system. It is intended to do so. In other words, the amount of heat exchanged in the water evaporator is Q=A・U・△
Represented by T. 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.

Embodiments Hereinafter, preferred embodiments of the present invention will be described based on drawings shown in the form of flow sheets.

Shown generally at 10 in FIG. 1 is a falling film heat exchanger. This heat exchanger is a known one, and includes a vertically long shell 11, a tube 12 made up of a large number of heat transfer tubes supported above and below the shell 11,
It consists of an evaporator 13 communicating with the lower part of the shell,
A circulation pipe 17 for water, which is a heat medium, is configured from the lower part 14 of the shell 11 through the circulation pump 15 to the top 16 of the shell 11. Reference numeral 18 is an inlet for introducing steam from the previous device, and reference numeral 19 is an outlet for the steam condensate, which is returned to the device.

Next, reference numeral 20 denotes a turbo vapor compressor driven by an electric motor M. Its suction side is connected to the top 21 of the evaporator 13 through a pipe 22, and its discharge side is connected to the next stage equipment through a pipe 23. connected to. 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 regulator 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 PIC.
is replaced to control valve V.

Effects Since the configuration of the present invention is as described above, the effects of the present invention will be explained below using specific modes of operation of the present device.

The aforementioned equipment is shown as an acetic acid recovery column 30 in a synthetic fiber plant, and the equipment is shown as a methanol distillation column 40. Top 31 of recovery tower 30
The vapor of the organic solvent is discharged, and the heat contained in the vapor is introduced from the upper part 18 to the shell 11 side of the heat exchanger 10, raising the temperature of the water flowing inside the heat transfer tube of the tube 12, and the solvent is condensed. It is returned to the recovery tower 30 from the lower part 19 of the shell. heat exchanger 10
Inside, water passing through the tube 12 is evaporated on the tube wall, ejected into a liquid reservoir at the bottom, and 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, so that the heat retained in the solvent vapor is sent to the compressor.

On the other hand, the condensed water in the liquid reservoir 14 is sent to the upper part 16 of the shell 11 via the pump 15, flows down the tube 12 with a membrane, and is circulated through the circulation pipe 17 for heat exchange. 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 increases and the specific volume of the vapor decreases, so the compressor The suction vapor capacity of the compressor decreases and approaches the compressor surging region, resulting in fluctuations in suction side conditions.

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, so that the amount of circulating water is adjusted to increase, and the water is The U-value of the evaporator decreases, the boiling point of the water in the evaporator remains constant, and the compressor 20
It will be stabilized by returning the suction side conditions to the constant side.

For such changes in heat transfer, the recovery tower 30
This occurs not only due to changes in the amount of organic solvent vapor associated with moment-to-moment operating fluctuations, but also due to relatively long-term fluctuations associated with scale formation. Control is possible in both directions as closed.

Further, regarding fluctuations on the methanol distillation column 40 side, the controller similarly operates in the open and close directions. That is, when the conditions change on the discharge side of the compressor 20, this fluctuation appears in a change in the load of the motor M, which causes a change on the suction side.
The steam conditions within the reactor will change and will be 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 for each environmental condition of the plant.

Effects of the Invention The heat pump device used in 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.
Not only is this heat pump device perfect for its original purpose of heat recovery, but it can also be used to effectively utilize heat. The system itself performs a harmonizing action, and also constantly matches external conditions associated with various fluctuations in the upstream and downstream stages, including the environmental conditions of the plant, thereby enabling stable plant operation.

[Brief explanation of drawings]

The drawing shows a preferred embodiment of the present invention in the form of a flow sheet, and the heat source side and the supply side for heat recovery are shown as part of a plant system. 10...Liquid film undersulfur heat exchanger, water evaporator, 11
... Ciel, 12 ... Tube, 13 ... Evaporator, 15 ... Circulation pump, 17 ... Circulation pipe, 2
0...vapor compressor, 22,23...pipe, TIC...
Temperature indicating controller, V...control valve, S...sensor,...previous device,...subsequent device.

Claims (1)

[Scope of Claims] 1. A liquid film falling heat exchanger, which is a water evaporator, and a vapor compressor are provided between the front-stage device and another device in the rear-stage, and a shell communicating with the shell of the heat exchanger. A circulating heat medium pipe is provided to circulate water, which is a heat medium, from the bottom of the shell to the top of the shell via a circulation pump, and a control valve inserted into the pipe and a sensor that detects the steam temperature of the water evaporator are provided. A control device consisting of a temperature controller is provided, and the retained heat of the steam from the preceding stage device is introduced into the shell side of the liquid film falling heat exchanger, and is replaced with the retained heat of the steam generated on the tube side, thereby providing indirect heat. 1. A heat recovery device characterized by interposing a heat pump device which collects water vapor, raises the temperature of the recovered water vapor in the vapor compressor, and uses the recovered water vapor as a heating source for other devices in the subsequent stage. 2. The heat recovery device according to claim 1, wherein a second type absorption heat pump is installed in place of the vapor compressor. 3. The heat recovery device according to claim 1, wherein the control device comprises a control valve and a pressure detection type temperature controller that senses the pressure inside the water evaporator can as a temperature controller. 4. The heat recovery device according to claim 1, wherein the control device comprises a control valve and a temperature controller that senses the temperature inside the water evaporator can.