JPS5942239B2 - Vacuum heat exchange equipment with temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention connects a heat exchanger that exchanges heat using hot gas or combustion exhaust gas generated from a boiler or the like with a vacuum container maintained under reduced pressure in a closed system. Vacuum of a vacuum heat exchange device in which the heat is recovered by the working fluid flowing inside the tube heat exchanger, circulated to the vacuum container, and the heat is taken out to the outside by the heat exchanger loaded in the vacuum container. The present invention relates to a vacuum heat exchange device equipped with a temperature or pressure control device whose purpose is to maintain the inside of a container under reduced pressure at all times.

In recent years, the oil situation has become extremely tense worldwide, and the use of alternative fuels to replace petroleum energy has been discouraged.

On the other hand, in many conventional boilers, the exhaust gas that is combusted is released into the atmosphere at a temperature of 250 to 300°C (exhaust heat recovery as a measure to save energy has been increasingly attracting attention.

However, if the temperature is relatively high, such as boiler exhaust gas, it is sufficient to operate the fluid in the economizer at a temperature above atmospheric pressure, but if the heat is recovered by lowering it to a lower temperature, the fluid temperature in the economizer increases. also needs to be lowered.

However, simply lowering the temperature of the fluid in the economizer has the drawback of causing low-temperature corrosion of the equipment due to the dew point of the exhaust gas.

As a method to eliminate this drawback and achieve the purpose of waste heat recovery at low temperatures, the waste heat recovery system is made into a closed system using a working fluid kept under vacuum, and a vacuum heat exchanger for the working fluid with a lower boiling point is used. Consideration has been given to introducing it.

Typically, within a closed system, a working fluid, such as water or a heat transfer fluid, has a saturated vapor or heat transfer vapor pressure depending on the temperature of the fluid.

For example, water exhibits an internal pressure of 1 atm at 100°C.

In a sealed system as described above, the working fluid inside the heat exchanger heated by hot gas or combustion exhaust gas becomes saturated steam in the vacuum chamber according to the liquid temperature, and its saturated steam pressure is indicated. The pressure inside the vacuum container will increase, but by loading a heat exchanger inside the vacuum container, it becomes possible to take out the amount of heat equal to the amount of heat heated outside, and the pressure inside the vacuum container will be reduced to the same amount as inside the original container. The pressure is maintained at a certain level, which is equal to the pressure, and the heat balance is maintained.

By the way, if this heat balance is disrupted and the amount of heat heated by hot gas etc. is greater than the amount of heat extracted to the outside, the temperature of the circulating fluid inside the vacuum container will rise, and the pressure inside the vacuum container will rise. However, this results in the inability to maintain the inside of the vacuum container under reduced pressure.

Furthermore, in the case of combustion exhaust gas, low-temperature corrosion of the heat exchanger due to dew condensation becomes a problem, so it is necessary to make the exhaust gas temperature at the outlet of the heat exchanger higher than the dew point temperature of the exhaust gas.

This is achieved by constantly maintaining the internal pressure in the vacuum vessel at a certain constant pressure under reduced pressure so that the temperature of the circulating working fluid remains constant, and by controlling the liquid temperature to be higher than the dew point temperature of the exhaust gas.

In conventional exhaust heat recovery equipment, when controlling the flow rate of hot gas or combustion gas flowing into the heat exchanger, a damper is provided for controlling the flow rate on the upstream or downstream side of the heat exchanger. The hot gas or combustion exhaust gas flowing into the exchanger may be influenced by the damper and become biased.
Not only will the heat recovery rate of the heat exchanger decrease (but the damper will also need to be made larger).

In view of the above, the present invention provides a method for connecting working fluid inflow and outflow side pipes of a tubular exchanger containing a working fluid such as hot gas or combustion exhaust gas in a flow path to a vacuum container loaded with a heat exchanger. The working fluid is connected to the tubular heat exchanger and the vacuum container so that heat is extracted from the system by the heat exchanger in the vacuum container, and the hot gas or combustion exhaust gas is A bypass flue equipped with a bypass damper that controls the flow rate of hot gas or combustion exhaust gas is provided in the flow path of the vacuum vessel, and a device (attached to the vacuum vessel) that detects the liquid temperature or pressure of the circulating fluid in the vacuum vessel A device (hereinafter referred to as a temperature or pressure detector) that controls a bypass damper attached to the bypass flue (hereinafter referred to as a control motor) is connected to detect the temperature or pressure of the liquid in the vacuum container by connecting the temperature or pressure detector. Detect and create control mode
The present invention provides a vacuum heat exchange device equipped with a temperature control device that controls a bypass damper by increasing the temperature of the vacuum chamber, and by controlling the flow rate of hot gas or combustion exhaust gas to be bypassed, the pressure inside the vacuum container is constantly reduced. This allows it to be held at the bottom.

The device for controlling the flow rate of hot gas or combustion exhaust gas to be bypassed according to the present invention can easily prevent uneven flow of hot gas or combustion exhaust gas flowing into a tubular heat exchanger, and the control damper can also be configured to take into account the pressure loss of exhaust gas. It also has the advantage of being miniaturized and is indispensable for fully demonstrating its function in a vacuum heat exchange device installed in a steam or hot gas flow path.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an example of the implementation of the present invention, which includes a tubular heat exchanger 4 that exchanges heat with combustion exhaust gas 1 discharged from a flue 2 of a boiler, a bypass flue 3 of the tubular exchanger, and a bypass damper 5. It consists of a control motor that drives the bypass damper 5, a connecting pipe 7 that connects the heat exchanger and the vacuum vessel 8, a heat exchanger 9 installed in the vacuum vessel 8, and a pressure or temperature detector 10.

This tubular heat exchanger 4 and the connecting pipe 7 vacuum vessel 8 are maintained under reduced pressure.

Heat is exchanged between the combustion exhaust gas discharged from the flue of a boiler or furnace, etc., and the water or heat medium fluid held in the vacuum container 8, the connecting pipe 7, and the heat exchanger 4, resulting in heated water or heat medium fluid. is introduced into a vacuum vessel.

The water or heat transfer fluid heated in the vacuum container 8 becomes saturated steam according to the saturated pressure in the container, but the heat is extracted to the outside from the heat exchanger 9 installed in the container, so that it becomes steam or The condensed water drips and accumulates at the bottom of the vacuum container, passes through the connecting pipe, and is returned to the tubular heat exchanger 9 for circulation.

By the way, if the amount of heat heated by the combustion exhaust gas in the water or heat transfer fluid is greater than the amount of heat taken out to the outside, the liquid temperature of the circulating water in the vacuum container 8 will rise, and this will be detected by the temperature or pressure detector 10. and the detector 1
By driving the control motor 6 of the bypass damper connected to 0, the bypass damper 5 is opened, and the combustion exhaust gas 1 is released from the bypass flue 3 to the flue 11, thereby keeping the liquid temperature of the circulating water in the vacuum container at a constant temperature. Control as follows.

Conversely, if the amount of heat heated by the combustion exhaust gas is less than the amount of heat taken out to the outside, the temperature of the circulating water will drop, so the detector 10 detects this and drives the control motor 6 of the bypass damper 5 to prevent the bypass. By closing the damper 5 and causing the combustion exhaust gas to flow toward the heat exchanger 4, the amount of heating of water or heat transfer fluid is increased, and the circulating water in the vacuum container is controlled to a constant temperature.

[Brief explanation of the drawing]

FIG. 1 shows a flow sheet of one embodiment of the present invention. 1... Combustion exhaust gas, 2, 11... Flue, Total -... Bypass flue, 4... Tubular heat exchanger, 5...・Bypass damper, 6...
Control motor, 7°... Connection piping, 8... Vacuum vessel, 9... Heat exchanger, 10... Temperature or pressure detector.

Claims (1)

[Claims] 1. Connect the pipes on the inflow and outflow sides of the working fluid in the pipes of a tubular heat exchanger containing working fluid such as hot gas or combustion exhaust gas in the flow path to a vacuum container loaded with the heat exchanger, by the heat exchanger in the vacuum vessel, such that the working fluid is circulated between the tubular heat exchanger and the vacuum vessel;
A bypass flue is installed in the flow path of the hot gas or combustion exhaust gas to extract heat from the outside of the system, and is equipped with a bypass damper for controlling the flow rate of the hot gas or combustion exhaust gas. A device that detects the temperature or pressure of the circulating fluid in the container (hereinafter referred to as a temperature or pressure detector) is connected to a device that controls the bypass damper attached to the bypass flue, and the temperature or pressure is detected. A vacuum heat exchange device equipped with a temperature control device that controls a bypass damper by detecting liquid temperature or pressure in a vacuum container using a device and activating a device that controls the bypass damper.