JPH0734918B2 - Flow dryer control method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for obtaining a drying load and a water content of a raw material of an airflow dryer for airflow drying a raw material such as sewage sludge using an airflow pipe.

2. Description of the Related Art For example, in a sludge drying and incinerator as shown in Japanese Examined Patent Publication No. 57-6007, a combustion gas generated in an incinerator is supplied to a dryer and is used for pretreatment of sludge. ing. Generally, the air flow dryer is most effective when it is operated at the design capacity, and the basic unit such as fuel cost and electric power cost is the minimum at the design rated load. Therefore, it is necessary to increase the processing amount when the drying load is too small and decrease the processing amount when the drying load is too large. Also, since the drying load is greatly affected by the water content, the processing amount of the raw material is set primarily according to the water content of the raw material, and the processing amount of the raw material is secondarily adjusted by the drying load. Doing so will result in efficient operation of the flash dryer. Conventionally, it has been difficult to continuously grasp the drying load and the water content of the raw material when the water content of the raw material such as sludge varies greatly.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a control method capable of continuously grasping a drying load or a water content of a raw material in order to operate an airflow dryer with a design capacity. is there.

Means for Solving the Problems The present invention provides a method for controlling an air flow dryer in which a raw material to be dried and a gas are guided to a gas flow tube by a fan, and a heat input amount at an inlet of the gas flow tube is a gas flow drying method. The airflow dryer control method is characterized by calculating the drying load as equal to the sum of the heat radiation amount of the machine, the heat output of the gas from the outlet of the airflow tube, and the heat quantity required for drying. is there.

Further, the present invention, the raw material to be dried, and the gas, in the method of controlling the airflow dryer by attracting to the airflow tube with a fan, the heat input amount of the inlet of the airflow tube, the heat radiation amount of the airflow dryer, As the sum of the heat output of the gas from the outlet of the air flow tube and the heat required for drying, the dry load is calculated to obtain the weight of the dried dry matter, and the dry load and the weight are detected. Based on the above, the method for controlling the airflow dryer is characterized in that the water content of the raw material is calculated and obtained.

Action According to the present invention, the heat load at the inlet of the airflow tube is equal to the sum of the heat radiation amount of the airflow dryer, the heat output of the gas from the outlet of the airflow tube, and the heat quantity required for drying. Can be calculated and obtained. The heat input amount at the inlet of the air flow tube can be determined by the flow rate of the gas supplied to the air flow tube, its specific heat, and the air flow tube inlet temperature. The flow rate of the gas supplied to the air flow tube can be determined by subtracting the vapor amount corresponding to the dry water amount from the gas flow rate at the outlet of the air flow tube. The heat radiation amount of the airflow dryer can be assumed to be, for example, 5% of the heat input amount. The heat output of the gas from the outlet of the gas flow tube can be determined by the flow rate of the gas at the gas flow tube outlet, the heat of the flow, and the temperature of the gas at the outlet of the gas flow tube. Further, the amount of heat required for drying per unit weight of water can be determined as a fixed value, assuming a predetermined drying condition. In this way, the drying load, that is, the amount of heat required for drying, can be obtained by calculating from three variables of the gas flow rate at the airflow tube outlet, the airflow tube inlet gas temperature, and the airflow tube outlet gas temperature.

Further, according to the present invention, the water content of the raw material can be calculated from the drying load thus obtained and the weight of the dried product obtained by drying.

Embodiment FIG. 1 is an overall system diagram of an embodiment of the present invention. A gas of high temperature is supplied to the airflow dryer 1 from a pipe line 2, and a raw material to be dried, such as sewage dehydrated sludge, is supplied from a shout 3. Gas and raw material are crusher 4
Is crushed in, and dried when rising the airflow tube 5,
The dried product after being dried is captured by the cyclone 6 and discharged from the shute 7. The weight of the dry matter captured by the short 7 is detected by the weighing machine 8.

The gas cleaned by the cyclone 6 is attracted from the conduit 9 by the attracting fan 10 and passes through the conduit 11 to the exhaust gas treatment device.
It is guided to 12, is dedusted, for example, and is discharged from the conduit 13 via the chimney 14.

The hot-blast stove 15 that supplies high-temperature gas to the pipeline 2 has a burner 16, and fuel, such as heavy oil or digested gas of sludge, is supplied to the burner 16 via a flow control valve 18 via the pipeline 17. To be done. Combustion air is supplied to the hot air passage 15 from a pipe 19. The gas thus supplied to the conduit 2 is the hot air stove 15
It is burning gas from. As another embodiment of the present invention, the pipe 2 may be air or the like, which is indirectly heat-exchanged in the hot stove 15.

The static pressure difference ΔP (mmAq) between the inlet and the outlet of the fan 10 is 21
Detected by. A bypass conduit 22 is connected between the conduit 11 and the conduit 2, and a flow control valve 23 is interposed in this conduit 22. The controller 24 controls the opening degree of the flow control valve 23 so that the static pressure difference detected by the pressure gauge 21 becomes a predetermined constant value. By thus circulating a part of the gas discharged from the fan 10 to the inlet side of the airflow dryer 1, the flow velocity or flow rate in the airflow pipe 5 can be controlled to be constant. By keeping the flow velocity in the air flow pipe 5 constant, the residence time of the raw material to be dried in the air flow pipe 5 can be made constant and the raw material can be sufficiently dried.

At the inlet of the airflow dryer 1, the gas temperature T1 (° C)
A thermometer 25 for detecting Gas temperature T2 of the outlet discharged from the cyclone 6 of the airflow dryer 1 to the pipe line 9
(° C.) is detected by the thermometer 26. It is assumed that the heat radiation amount Ql (kcal / H) of the airflow dryer 1 is, for example, 5% of the heat input amount Q1 of the airflow dryer 1. The specific heat Cp (kcal / Nm ³ ° C) of the gas passing through the pipe 9 is, for example, 0.34. W (kg / H) is the amount of water to be dried containing the raw material input from the shout 3, and the raw material is discharged from the short 7 as dry sludge. The amount of heat required to dry the raw material q (kc
al / kg) is 650 kcal / kg as the amount of heat required for evaporation of water and heating of steam.

When the constants are A and B, the flow rate F (m ³ / H) of the dry gas flowing through the conduit 9 is approximated by the first equation.

F = A · ΔP + B (1) Heat input amount Q1 and heat output amount in order to calculate and obtain the dry water amount W
Q2 and are calculated according to the second and third equations.

Q2 = 0.05 ・ Q1 + F ・ Cp ・ T2 + W ・ q (3) The value 18 in the second equation is the molecular weight of water, and 22.4 is water vapor.
It is the volume per 1 kg mole. Formula 3 terms F ・ Cp ・ T2
Is the heat output of the gas in the conduit 9. The term W in the third equation
-Q is the amount of heat required for drying.

The following formula is established as Q1 = Q2 (4).

(0.323 ・ T1-0.34 ・ T2) ・ F = (0.4 ・ T1 + 650) ・ W… (5) The arithmetic circuit 28 responds to the outputs of the pressure gauge 21 and the thermometers 25 and 26, that is, the temperature T1 and the temperature T2, and calculates and obtains the dry water amount W, that is, the drying load of the airflow dryer 1 based on the sixth equation. .

Furthermore, if the weight of the dry matter, that is, dry powder, detected by the weighing machine 8 for detecting the weight of the dry matter is D (kg / H), the raw material supply amount G (kg / H) from the shut 3 is the seventh. As shown in the formula G = W + D (7) Therefore, the water content η of the raw material is controlled by controlling the gas temperature T2 of the dry product water content ηd discharged to the pipe 9 to a predetermined value. Since it becomes almost constant, for example, 10%, it is as shown in the eighth formula.

The arithmetic circuit 28 calculates and obtains the water content η of the raw material from the eighth small amount based on the output of the weighing machine 8 and the dry water amount W obtained based on the above-mentioned sixth formula.

In this way, the drying load of the airflow dryer 1 and the water content of the raw material can be easily and continuously grasped, so that the airflow dryer 1 can always be operated with the designed capacity. The throughput of the raw material supplied from the short 3 is adjusted.

A pressure gauge 30 is provided in the pipe line 2, and a controller 32 has a flow rate control valve 31 provided in the pipe line 13 for adjusting the opening so that the pressure detected by the pressure type 30 has a predetermined constant value. Make adjustments. This prevents the airflow dryer 1 from becoming a positive pressure so that hot air does not blow out to the outside, and prevents a large negative pressure from causing air to enter the airflow dryer 1 from the outside and lowering the thermal efficiency. .

The output of the thermometer 26 provided in the pipeline 9 is also the adjustment meter.
Given to 33. The regulator 33 controls the opening degree of the flow rate control valve 18 that supplies fuel to the burner 16 so that the temperature of the gas detected by the thermometer 26 becomes a predetermined constant value.

EFFECTS OF THE INVENTION As described above, according to the present invention, the drying load of the airflow dryer or the content rate of the raw material to be dried is calculated and continuously determined, and thereby the airflow dryer is operated with the design capability. The air flow dryer can be operated most efficiently by increasing or decreasing the supply amount of the raw material so that it is possible.

Therefore, it is not necessary to install a flow meter at the place where the gas flowing through the air flow tube and the gas at the cyclone outlet that captures dry matter at the outlet of the air flow tube contain a large amount of solid matter, and to measure the flow rate. The problem of pressure loss that occurs when using a bench lily or orifice for the measurement does not occur, and the problem of dust that occurs when measuring the flow rate with the Pitot tube method is solved.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention. 1 ... Airflow dryer, 4 ... Crusher, 5 ... Airflow tube, 6 ...
… Cyclone, 10… Induction fan, 12… Exhaust gas treatment device, 14… Chimney, 15… ～ Hot stove, 16 …… Burner, 21 ……
Pressure gauge, 25, 26 ... Thermometer, 28 ... Arithmetic circuit

Front Page Continuation (72) Inventor Masakazu Sawai 3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries Ltd. Kobe factory

Claims (2)

[Claims] 1. A method for controlling an air flow dryer in which a raw material to be dried and a gas are guided to a gas flow tube by a fan, wherein the heat input at the inlet of the air flow tube is equal to the heat radiation amount of the air flow dryer. A method for controlling an air flow dryer, characterized in that a drying load is calculated and calculated as an amount equal to the sum of the heat output amount of gas from the outlet of the air flow pipe and the heat amount required for drying. 2. A method for controlling an air flow dryer in which a raw material to be dried and a gas are attracted to a gas flow tube with a fan and the heat input at the inlet of the air flow tube is equal to the heat radiation amount of the air flow dryer. As the sum of the heat output of the gas from the outlet of the air flow tube and the heat required for drying, the dry load is calculated to obtain the weight of the dried dry matter, and the dry load and the weight are detected. A method for controlling an airflow dryer, characterized in that the water content of the raw material is calculated based on the above.