JP2008070087A - Air heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air heater capable of preventing condensate from staying inside the heater. <P>SOLUTION: A steam supply pipe 2 is connected to a fin tube 8 of a heat exchanger 1 via a control valve 3 and an opening and closing valve 4. An air temperature detecting member 7 is attached to an outlet side of the heat exchanger 1. The air temperature detecting member 7 is connected electrically to the control valve 3. A heat-exchanger internal pressure detecting member 6 and a steam trap 5 are attached respectively to an outlet side of the fin tube 8. The heat-exchanger internal pressure detecting member 6 is connected electrically to the opening and closing valve 4. When the condensate stays in the fin tube 8 with pressure drop in the fin tube 3, the pressure drop therein is detected by the heat-exchanger internal pressure detecting member 6, to close the opening and closing valve 4, and the stayed condensate is discharged from the steam trap 5 to an outside, by control of enlarging a valve opening of the control valve in accompaniment to an decrease of air temperature and by control of opening the closed opening and closing valve. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air heating apparatus that heats air using steam as a heat source.

Conventional air heating devices use fin-tube heat exchangers to control the amount of steam supplied to the heating device with an adjustment valve, and use a check valve and a thermal valve together in the heating device. Thus, when the inside of the heating device is evacuated, the check valve is opened to prevent the condensate from being discharged by sucking outside air into the heating device.

The conventional air heating device has a problem that the condensate inside the heating device cannot be completely discharged. That is, when the inside of the heating device is evacuated, it is possible to prevent the differential pressure between the inlet side and the outlet side of the steam trap for sucking outside air and discharging condensate from being negative pressure, Both the pressures on the outlet side are atmospheric pressures, and the substantial differential pressure remains zero, and the condensate staying in the recesses and narrow pipes inside the heating device cannot be discharged to the outside. If condensate stays inside the heating device, it will stay until the next operation of the heating device, corroding the inside of the heating device, and depending on the case, a hole may be made in the fin tube and damaged.
Japanese Patent Publication No.51-31998

  The problem to be solved is to obtain an air heating device that does not retain condensate inside the device.

  The present invention connects a steam supply pipe for supplying steam for heating inside a heat exchanger composed of a plurality of stages, and attaches a control valve for controlling the amount of steam supplied to the steam supply pipe. A heat exchanger for attaching an air temperature detection member for detecting the temperature of air heated by steam while passing and controlling the valve opening degree of the control valve according to the detection value from the air temperature detection member. An on-off valve is installed on the steam inlet side of the heat exchanger, and a heat exchanger internal pressure detection member that detects the internal pressure of the heat exchanger is attached, and the on-off valve is opened and closed according to the detected value of the heat exchanger internal pressure detection member. To do.

  The present invention attaches a control valve and an on-off valve to the steam inlet side of a heat exchanger, and also attaches a heat exchanger internal pressure detection member for detecting the pressure inside the heat exchanger, and this heat exchanger internal pressure detection member By opening and closing the on-off valve according to the detected value, the pressure inside the heat exchanger decreases to, for example, about atmospheric pressure, and condensate stays inside the heat exchanger. By detecting the decrease and closing the on-off valve, the amount of steam supplied to the heat exchanger is reduced, and the temperature of the heated air is also reduced, so that the valve opening of the control valve on the inlet side is reduced. A large amount of steam is supplied into the heat exchanger, and the open / close valve that has been closed is opened again, so that the low-temperature condensate that has remained is immediately pushed out and discharged.

  As the control valve, one that can control the amount of steam to be supplied is increased or decreased, and as the on-off valve, one that can be switched between fully open and fully closed can be used. .

  In FIG. 1, a heat exchanger 1 that heats air passing from below to above, a steam supply pipe 2 that supplies steam to the heat exchanger 1, a control valve 3 attached to the steam supply pipe 2, and heat exchange Three on-off valves 4 attached to the steam inlet side of the steam generator 1, a steam trap 5 connected to the outlet side of the heat exchanger 1, and a pressure detection member 6 in the heat exchanger attached to the inlet side of the steam trap 5 And an air heating device.

A control valve 3 for controlling the steam pressure supplied to the heat exchanger 1 to a predetermined value is attached to the steam supply pipe 2. An air temperature sensor 7 as an air temperature detection member is attached to the upper outlet side of the heat exchanger 1 and is electrically connected to the control valve 3 via a control unit (not shown).

The heat exchanger 1 is a fin-tube heat exchanger having a vertically long cylindrical shape in this embodiment, and has a plurality of stages, in this embodiment, three-stage fin tubes 8 attached to the heat exchanger 1. While the air as an object passes through the heat exchanger 1 from the lower side to the upper side as indicated by an arrow, it is heated to a predetermined temperature by the steam passing through the inside of the fin tube 8. The condensed water that has been taken away and condensed is discharged from the steam trap 5 and the condensate discharge pipe 9 to the outside.

  The temperature of the heated air is detected by an air temperature sensor 7 attached to the upper air outlet of the heat exchanger 1, and when the air temperature is higher than the set temperature, the valve opening of the control valve 3 is reduced. By reducing the amount of steam to be supplied, the air temperature is maintained at a set temperature, and when the air temperature is lower than the set temperature, the valve opening of the control valve 3 is increased to increase the amount of steam to be supplied. Thus, the air temperature is raised to the set temperature.

  A pressure sensor 6 as a heat exchanger internal pressure detection member detects the pressure in the fin tube 8 on the inlet side of the steam trap 5. The pressure sensor 6 is electrically connected to the on-off valve 4 via a control unit (not shown).

  When the heated air temperature detected by the air temperature sensor 7 is lower than the set temperature, the valve opening degree of the control valve 3 is largely controlled, and all the three on-off valves are kept open.

When the heated air temperature detected by the air temperature sensor 7 is higher than the set temperature, the valve opening of the control valve 3 is reduced and the amount of steam supplied is reduced. When the throttle amount of the control valve 3 is increased, the supply steam amount is extremely reduced, and the steam pressure in the fin tube 8 is lowered, so that the condensate amount discharged from the steam trap 5 to the condensate discharge pipe 9 is also extremely reduced. The condensate is retained in the fin tube 8.

By detecting the stagnation of the condensate with the pressure sensor 6 in the heat exchanger, the on-off valve 4 on the inlet side of the fin tube 8 whose pressure has dropped is closed. When a part of the on-off valve 4 is closed, the amount of steam supplied to the heat exchanger 1 decreases, so when the heated air temperature decreases and becomes lower than the set temperature, the valve opening of the control valve increases. In this way, a large amount of steam is supplied, and at the same time, the on-off valve 4 that has been closed is controlled to open, so that a large amount of steam is supplied into the fin tube 8 and stays inside. By pushing the condensed water from the steam trap 5 to the condensed water discharge pipe 9, the condensate can be prevented from staying.

When the state where the heated air temperature is higher than the set temperature continues, there is a high possibility that condensate remains in the plurality of fin tubes 8, and therefore the plurality of on-off valves 4 are periodically closed sequentially. By switching from valve opening to valve opening, it is possible to prevent a large amount of condensate from staying in the fin tube 8 and to prevent the water hammer phenomenon.

The block diagram which shows the Example of the air heating apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Steam supply pipe 3 Control valve 4 On-off valve 5 Steam trap 6 Heat exchanger internal pressure detection member 7 Air temperature detection member 8 Fin tube 9 Condensate discharge pipe

Claims (1)

A steam supply pipe for supplying steam for heating is connected to the inside of the heat exchanger consisting of a plurality of stages, a control valve for controlling the amount of steam supplied to the steam supply pipe is attached, and while passing through the heat exchanger An air temperature detection member that detects the temperature of air heated by steam is attached, and the valve opening degree of the control valve is controlled according to the detection value from the air temperature detection member. A heat exchanger internal pressure detection member that detects the pressure inside the heat exchanger, and opens and closes the open / close valve according to the detection value of the heat exchanger internal pressure detection member. Air heating device.

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