JPS64632B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for rationally controlling the operation of a hot air drying apparatus for drying slurry, paste-like materials, powder-like materials, etc.

[Conventional technology]

Conventionally, there are many types of drying equipment for slurry, paste-like materials, powder and granular materials, etc. (hereinafter referred to as "materials to be dried"), but the model is determined depending on the requirements regarding the shape and quality of the dried product. In other cases, the agitation drying device with internal stirring blades is the best in terms of downsizing the device.
Further, stirring is particularly effective for materials with strong cohesion.

The main types of stirring drying equipment are the stirring hot air drying equipment, which feeds hot air into the main body and uses stirring blades to crush the material to be dried while increasing the surface area in contact with the hot air, and the other, which uses steam as a heat source. There is an indirect heating agitation drying device which uses a heating jacket in the main body to allow steam to flow therethrough, and is further equipped with hollow stirring blades inside which steam flows. However, the operation control of the latter indirect heating type stirring dryer is extremely troublesome and equipment-intensive, as it involves controlling the steam temperature or pressure on the outlet side and adjusting the rotation speed of the stirring blade, which also serves as a heat transfer wall. The former type of stirring hot air drying equipment is often used because it is complicated, susceptible to qualitative changes in materials, and the range of usable heat sources is limited by the boiler capacity.

Operation control of the stirring hot air drying equipment is performed by empirically determining the amount of hot air and the amount of material to be dried, and adjusting the amount of fuel in the hot air generating furnace so that the temperature of the drying exhaust gas remains constant. . This is because adjusting the hot air temperature has a faster response and makes it easier to maintain the heat balance inside the device. However, there are qualitative and quantitative fluctuations in the heat source, such as when handling materials with variable properties such as dehydrated cakes of slurry, or when using waste heat from other processes. It becomes very difficult to drive if it includes. To deal with this, it is necessary to mix materials to homogenize them, or to compensate for fluctuations in hot air using auxiliary fuel such as heavy oil, which is not only unreasonable from an energy conservation perspective. This results in an increase in the complexity of the device and the cost of the device.

Further, the set value of the dry exhaust gas temperature is usually 180 to 200°C when the hot air temperature is 700 to 900°C, and this value includes a margin for safe operation of the device. From a drying theory, the lower the temperature of the drying exhaust gas, the higher the thermal efficiency.However, the balance between the amount of water to be evaporated, that is, the amount of material to be dried, and the amount of heat brought in by the hot air is lost, and the amount of heat increases. If there is a shortage, discharge undried materials,
There is a risk that serious problems such as material clumping may occur, leading to the inability to operate. For this reason, more heat is brought in, and the exhaust gas temperature is raised to avoid serious problems, which inevitably results in lower thermal efficiency. However, such a disadvantage in terms of thermal efficiency can be said to be unavoidable in the conventional method.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned drawbacks in operation control in a stirring hot air drying device, and improves hot air conditions, quality of materials,
The objective is to provide a rational control method that can adequately cope with quantitative fluctuations, has high thermal efficiency, and has high control accuracy.

[Means for solving problems]

The present invention is an agitating hot air drying device equipped with an internal agitating device, and measures the body surface temperature of a portion that comes into contact with the material to be dried staying inside, or the difference between this temperature and the drying exhaust gas temperature, and measures the temperature or the temperature difference. This is a method of controlling a drying device, characterized by adjusting the supply amount of a material to be dried so that the temperature is maintained within a preset temperature range.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the device includes, for example, a rotary stirring blade 2 disposed inside a rigid cylindrical body 1,
A hot air introduction pipe 4 connected to a hot air supply device 3 is opened at the bottom, and a supply pipe 6 connected to a drying material supply device 5 is opened.

This supply pipe 6 is preferably opened at the bottom of the machine body 1 or at the lower part of the side wall, in order to increase the drying efficiency by creating a parallel flow with the hot air, and furthermore, it is in contact with the material layer staying inside the machine body 1. It is quickly mixed by feeding it to the site. Further, the material supplying device 5 to be dried is preferably a high-pressure pump type that can be transported through a pipe, and this is effective in improving responsiveness and press-fitting the material into the material layer.

Further, a dry exhaust gas duct 7 is connected to the upper part of the machine body 1, and a product discharge chute 8 opens at a height of about 1/3 or more of the diameter of the machine body 1, and is guided to the outside via an airtight damper 9. Further, the rotary stirring blade 2 is driven by a drive device 10 via a gear box 11, and the shaft torque of the rotary stirring blade 2 is detected by a torque detector 12.

The hot air is introduced into the lower part of the machine body 1 from the hot air supply device 3 through the hot air introduction pipe 4, and after coming into direct contact with the material layer to be dried which has been crushed by the rotation of the rotary stirring blades 2, the upper part is dried. The material to be dried is discharged from the exhaust gas duct 7 and remains in the machine body 1 for a certain period of time to become a dried product, which is then taken out from the product discharge chute 8 via an airtight damper 9 to the outside.

The material to be dried that remains in the body 1 has almost completely dried material in the upper part of the layer, and material that is still quite wet in the lower part. However, since the mixing is carried out by the rotating stirring blade 2, the difference in the moisture content between the upper and lower layers is not very large, and the entire layer is in a state where the material is dispersed in granular form, which is desirable for drying, and this operating state is maintained. It is preferable to do so. In this way, the supplied material to be dried is mixed with the dispersed particles, spread over the particle surfaces, and subjected to drying.

However, when a large amount of material to be dried is supplied and comes into contact with hot air, according to drying theory, the material first passes through a preheating period and then enters a constant rate drying period. In this section,
The temperature of the material is at or below the wet bulb temperature relative to the hot air temperature. For example, under normal hot air conditions (600
~800℃), the material temperature will be 65-75℃. Also,
If the supply of material is cut off and only drying proceeds,
The moisture content of the retained material gradually decreases and enters the lapse rate drying section according to drying theory, during which the material temperature gradually increases.

Therefore, when obtaining a dry product within a certain moisture range, it is sufficient to measure the temperature change of the material itself and adjust the feed rate of the material; it is not necessary to insert a thermometer into the material layer to measure the temperature. It is also structurally difficult. However, this problem can be solved by measuring the surface temperature of the aircraft body 1. That is, since the fuselage 1 is usually made of iron, it has high thermal conductivity and can quickly follow internal temperature changes. The surface temperature of the fuselage 1 is measured with a thermometer 13 for the fuselage surface. As the thermometer 13, a radiation thermometer or the like can be used, but a thermocouple or a thermometer may also suffice from the viewpoint of cost. It is best to fix thermocouples by pressing them against the surface with push bolts.
The temperature measurement site is preferably a wall portion in contact with the layer of the material to be dried, where the degree of temperature change is large and the response is fast, for example, a location close to both the hot air inlet and the material supply port to be dried.

The temperature of the machine body 1 measured in this way is input to the control device 14, and is compared with a preset value range set by the control device 14. If it exceeds the high set value, it is determined that the temperature has increased due to the progress of drying. When the temperature falls below the low set value, it is determined that the temperature has dropped due to excessive supply, and the supply of the material to be dried is stopped or the supply amount is reduced. , can always balance the heat and material within the layer.

The above control is suitable when the fluctuations in the hot air are relatively small, but when the fluctuations in the hot air are large, it is necessary to control the fluctuations in the material temperature not only by the degree of drying progress but also by the fluctuations in the hot air temperature. This may cause the control circuit to malfunction. In this case, the difference between the surface temperature of the airframe 1 and the dry exhaust gas temperature measured with the dry exhaust gas thermometer 15 attached to the dry exhaust gas duct 7 is calculated, and this is input into the control device 14 to control the influence of hot air fluctuations. can be avoided. This takes advantage of the property that the degree of influence on fluctuations in hot air temperature is approximately the same between the temperature of the airframe 1 and the temperature of the dry exhaust gas.

In addition, in the setting value range set in the control device 14, the difference between the high setting value and the low setting value is preferably within 20°C because if it is too large, it will cause variations in the quality of the dried product. .

Furthermore, in order to perform even more precise control, it is possible to introduce the same idea as the D operation in automatic control, that is, the differential operation. in this case,
The measured temperature is input to a control device having a differential calculation mechanism, the slope of the temperature rise or fall curve is determined, and the supply amount is set in proportion to the magnitude of the slope, or the value of the slope is set. It is preferable to operate and stop the supply device according to the set value.

In order to perform the above control method with higher accuracy, the shaft torque of the rotary stirring blade 2 is detected by the torque detector 12, and this torque value is detected by the
It is also effective to use the surface temperature or the difference between the surface temperature and the dry exhaust gas temperature. For example, the changes in the surface temperature of the machine body 1 and the torque value during operation are based on the property that, as shown in Figure 2, the torque value increases when there is an oversupply of material to be dried, and the torque value decreases as drying progresses. It is something.

〔Effect of the invention〕

As described above, according to the present invention, the supply amount of the material to be dried is adjusted to the optimum amount by closely following the hot air conditions in the stirring hot air drying device and the qualitative and quantitative fluctuations of the material. Make effective use of heat,
Moreover, it is highly accurate, extremely rational, and can have a great effect in terms of energy saving.

[Brief explanation of the drawing]

Fig. 1 is a partial vertical sectional view of a device showing an embodiment of the present invention, and Fig. 2 is a line showing the operating state of the material supplying device to be dried and changes in the machine body temperature and the shaft torque value of the rotary stirring blade. It is a diagram. DESCRIPTION OF SYMBOLS 1... Body, 2... Rotating stirring blade, 3... Hot air supply device, 4... Hot air introduction pipe, 5... Dry material supply device, 6... Supply pipe, 7... Dry exhaust gas duct, 8... ... Product discharge chute, 9 ... Airtight damper, 10 ... Drive device, 12 ... Torque detector,
13... Aircraft surface thermometer, 14... Control device,
15... Thermometer for dry exhaust gas.

Claims (1)

[Claims] 1. In an agitation hot air drying device equipped with an internal agitation device, the surface temperature of the machine body at a portion in contact with the material to be dried staying inside or the difference between this temperature and the drying exhaust gas temperature is measured, and the temperature or A method of controlling a drying device, comprising adjusting the amount of material to be dried such that the temperature difference is maintained within a preset temperature range. 2. Claim 1, wherein the difference between the high set value and the low set value of the set temperature range is within 20°C.
A method of controlling the drying device described in Section 1.