JPH0757359B2 - Evaporative load control method for steam dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention controls the evaporation load and controls the evaporation load when the moisture of an object to be dried such as sludge is dried by a steam dryer. The present invention relates to an evaporation load control method for a steam dryer that adjusts the amount of water contained in a dried product.

[Conventional technology]

In the conventional indirect heating steam dryer, for example, sludge supplied to the dryer is indirectly heated by steam supplied from the boiler and condensed in the dryer to a drain wrap or the like provided in the dryer outlet side line. I was draining the drain.
However, only by indirectly heating the sludge with steam in this way, if the amount of steam supplied to the dryer is the same and the heat transfer area is constant, the evaporation amount will be constant, and the sludge water content at the dryer outlet side No control is available.

[Problems to be solved by the invention]

Therefore, conventionally, it has been attempted to reduce the amount of sludge retained in the dryer for the purpose of adjusting the water content of the sludge, but there are problems in responsiveness, operability, etc., and it has not yet been put to practical use. .

Further, when actually adjusting the water content of the sludge, a device capable of continuously measuring the water content of the sludge is required, and various studies have been made on such a device in the past, but it has reached the range of practical application. There wasn't. However, recently, a highly reliable continuous moisture measuring instrument capable of continuously measuring the water content has been developed.

The present invention makes it possible to control the amount of water contained in the dry matter on the outlet side of the steam dryer, that is, to control the evaporation load, and to control the amount of water contained in the dried matter on the outlet side of the dryer. It is an object of the present invention to provide an evaporation load control method for the above.

[Means for solving problems]

The present invention adopts the following means in order to solve the above problems. That is, in a steam dryer for indirectly heating and drying an object to be dried with a steam, a pressure control valve provided on the steam inlet side of the dryer, a drain pot provided on the drain outlet side of the dryer, Drain pot water level control valve installed on the drain pot discharge line to control the liquid level of the drain pot, and a measuring device and a moisture content meter, which are respectively installed on the dried product outlet side of the dryer to continuously measure the discharged amount of dried product. And a moisture measuring device for continuously measuring, measuring the amount of moisture contained in the dried material on the dryer outlet side by the measuring device and the moisture measuring device, and using this moisture amount as a control element of the pressure control valve. Evaporation load control is performed to control the opening to keep the vapor pressure constant at the target value of vapor pressure according to the drying load, and the liquid level of the drain pot is monitored by a level controller. By controlling the opening of the drain pot water level control valve so that the liquid level is constant and discharging the drain amount corresponding to the heat exchange amount in the steam dryer, fluctuations in the dryer internal pressure are prevented. The steam pressure in the steam dryer is kept constant.

[Action]

Therefore, in such an evaporation load control method for a steam dryer, the amount of water contained in the dried material on the outlet side of the dryer measured by the measuring device and the water content measuring device is used as a control element to open the pressure control valve. If the temperature is adjusted and the vapor pressure is kept constant at the target value of the vapor pressure according to the drying load, the temperature control of the dryer heat transfer surface is performed and the supplied heat amount is also controlled.
The moisture on the outlet side of the dryer can be kept constant, and the moisture contained in the dried product can be made uniform.

Also, the level of the drain pot is monitored by a level controller, and the opening of the drain pot water level control valve is controlled so that the level of the drain pot is constant, and the drain that matches the amount of heat exchanged in the steam dryer is controlled. By discharging a certain amount, the drain pot water level holding plays the role of a liquid valve in the steam and drain flow paths of the pressure control valve-dryer-drain pot-drain pot water level control valve-drain discharge port. By keeping the pressure at a constant level, it is possible to prevent fluctuations in the internal pressure due to steam discharge due to liquid leakage, and
Stable operation can be performed under a wide range of operating conditions.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a system configuration for explaining an evaporation load control method for a steam dryer according to the present invention. In FIG. 1, reference numeral 1 denotes a dryer for indirectly heating sludge with steam to remove water content, and steam is supplied from a boiler 2 to the dryer 1, and pressure is supplied to the steam supply line. A control valve 3 is provided. Further, 4 is a drain pot provided in the drain line of the drain water condensed in the dryer 1, and the drain pot 4 stores the drain discharged from the dryer 1, and the liquid level thereof is monitored by the level controller LC. And the drain water level control valve 5 provided in the discharge line of the drain pot 4 so that the liquid level is always constant.
To control opening and closing. 6 and 7 are dryers 1.
A measuring instrument and a moisture measuring instrument, which are respectively provided on the discharge lines of the sludge dried in, the measuring instrument 6 continuously measures the discharge amount of the dried sludge, and the moisture measuring instrument 7 measures the water content of the dried sludge. It measures continuously. On the other hand, 8 is an arithmetic unit for obtaining the valve opening degree based on a target value by using the amount of water contained in the dried sludge of the dryer 1 measured by the measuring device 6 and the water content measuring device 7 as a control element of the pressure regulating valve 3. Then, the valve opening control signal obtained by the calculator 8 is applied to the pressure control valve 3 to control the steam pressure supplied from the boiler 2 to the dryer 1.

Next, a method for controlling the evaporation load of the steam dryer having the above system configuration will be described. Now, it is assumed that steam, which is a heating source, is supplied from the boiler 2 to the dryer 1 while the sludge is contained in the dryer 1 through the steam pressure control valve 3. In this case, on the steam side in the dryer, condensed water and saturated steam are mixed due to heat absorption on the sludge side. In such a state, the sludge is indirectly heated and dried in the dryer 1, and the drain condensed at that time is discharged from the drain outlet of the dryer 1 to the drain pot 4. This drain pot 4
The drain water level control valve 5 is controlled by the level controller LC so that the liquid level of the drain water accumulated in is always constant. Further, the dry sludge is discharged from the sludge outlet of the dryer 1, and at this time, the amount of the dry sludge and the moisture contained therein are continuously measured by the measuring device 6 and the moisture measuring device 7 provided in the discharge line. The measured values are input to the computing unit 8, respectively. In this computing unit 8, the amount of water contained in the dried sludge at the outlet of the dryer 1 measured by the measuring unit 6 and the moisture measuring unit 7 is also used as a control element of the pressure control valve 3 as a target value input from the setting unit 9. Then, the valve opening is obtained and the opening control signal is given to the pressure control valve 3 to control the steam pressure supplied from the boiler 2 to the dryer 1. That is, the amount of water contained in the dried sludge on the outlet side of the dryer measured by the measuring device 6 and the moisture measuring device 7 is used as a control element of the pressure control valve 3 based on the target water content of the dried sludge. By the so-called cascade control for controlling the inlet steam pressure, the temperature of the heat transfer surface of the dryer and the amount of heat supplied can be controlled to control the evaporation load. Note that it is possible to input the furnace temperature and the like as the target value of the computing unit 8. In this case, the total amount of water contained in the dried sludge at the dryer outlet side and the furnace temperature and the like are control elements of the steam pressure control valve 3. Becomes

By enabling the evaporation load control of the dryer 1 in this manner, it becomes possible to control the furnace temperature of the incinerator in, for example, the drying-incineration process. Further, the water content and the supply amount of the sludge may change before entering the dryer 1, but by performing the evaporation load control as described above,
The water content on the sludge outlet side of the dryer 1 can be kept constant,
It is possible to make the water content of the dried sludge uniform. Therefore, it can greatly contribute to the stable operation of equipment after the drying equipment, for example, incineration equipment. Further, the liquid level of the drain pot 4 provided on the outlet side of the dryer is monitored by the level controller LC, and the opening of the drain pot water level control valve 5 is controlled so that the liquid level of the drain pot becomes constant, and drying is performed. By discharging the amount of drain commensurate with the amount of heat exchanged in the machine 1, the drain pot water level in the steam and drain flow paths of the pressure control valve 3 to the dryer 1 to the drain pot water level control valve 5 to the drain outlet The holding plays the role of a liquid valve, and by keeping this at a certain level, it is possible to prevent fluctuations in the internal pressure due to steam discharge due to liquid leakage, that is, the internal pressure on the steam side is controlled and controlled within a predetermined range. Since the temperature is controlled, stable operation can be performed under a wide range of operating conditions.

That is, when the drain condensed in the dryer 1 is discharged uncontrolled by a so-called steam trap or the like, the flow rate of the drain fluctuates at any time due to load fluctuation and the steam side pressure, that is, the surface temperature, fluctuates. Although the controllability is impaired, by controlling the liquid level of the drain pot 4 to be constant as described above, it is possible to stably maintain the drying performance of the dryer.

FIG. 2 shows another embodiment of the present invention. In the system configuration of FIG. 1, a sludge supply pump 10 for supplying sludge to the dryer 1 is further provided with a measuring device 6'as described above at the outlet side. A moisture measuring device 7'is provided, and the total amount of water in the sludge supplied to the dryer 1 is measured by the measuring device 6'and the moisture measuring device 7 '. By inputting it to the calculator 8 as a control element of the pressure control valve 3 together with the amount of water contained in, the evaporation load control can be performed more strictly.

In each of the above-mentioned embodiments, the case where the sludge is used as the material to be dried to remove the moisture is described, but it goes without saying that the present invention may be another material containing moisture.

〔The invention's effect〕

As described above, according to the present invention, the vapor pressure is the target value of the vapor pressure according to the drying load with the amount of water contained in the dried material on the dryer outlet side measured by the measuring instrument and the moisture measuring device as the control element. When the opening of the pressure control valve is adjusted to maintain a constant value, the temperature of the heat transfer surface of the dryer is controlled and the amount of heat supplied is also controlled. This makes it possible to make the water content of the dried product uniform. Further, the level of the drain pot is monitored by a level controller, and the opening of the drain pot water level control valve is controlled so that the level of the drain pot is constant, and the drain amount corresponding to the heat exchange amount in the steam dryer is adjusted. By discharging the amount of water, the drain pot water level retains a liquid valve role in the steam and drain flow paths, and by keeping this at a certain level, fluctuations in the internal pressure of the machine due to vapor discharge due to liquid leakage can occur. It is possible to provide a method for controlling an evaporation load of a steam dryer, which can prevent and perform stable operation under a wide range of operating conditions.

[Brief description of drawings]

FIG. 1 is a control system block diagram of a steam dryer showing an embodiment of the present invention, and FIG. 2 is a control system block diagram of a steam dryer showing another embodiment of the present invention. 1 ... dryer, 2 ... boiler, 3 ... pressure control valve, 4 ...
… Drain pot, LC …… Level controller that controls the liquid level in the drain pot, 5 …… Drain water level control valve, 6 ……
Measuring device, 7 ... Moisture measuring device, 8 ... Computing device, 9 ... Setting device, 10 ... Sludge supply pump.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akitsugu Ohno 12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Yokohama Works (56) References JP-A-61-256180 (JP, A)

Claims (1)

[Claims] 1. A steam dryer for indirectly heating and drying an object to be dried by steam, wherein a pressure control valve provided on a steam inlet side of the dryer and a drain pot provided on a drain outlet side of the dryer. And a drain pot water level control valve provided in the drain pot discharge line for controlling the liquid level of the drain pot, and a measuring device provided continuously at the dried product outlet side of the dryer for continuously measuring the discharged amount of dried product And a moisture measuring device for continuously measuring the contained moisture, and measuring the amount of moisture contained in the dried material on the outlet side of the dryer by the measuring device and the moisture measuring device, and using the moisture amount as a control element to control the pressure. Evaporation load control is performed to control the opening of the control valve to keep the vapor pressure constant at the target value of the vapor pressure according to the drying load, and the level of the drain pot is monitored by a level controller. By controlling the opening of the drain pot water level control valve so that the liquid level is constant and discharging the drain amount corresponding to the heat exchange amount in the steam dryer, fluctuations in the dryer internal pressure are prevented. A method for controlling the evaporation load of a steam dryer, characterized in that the steam pressure inside the steam dryer is kept constant.