Method for controlling flow volume of coal/kerosene slurry, and apparatus for producing upgraded brown coal

Abstract

A method and apparatus that deterioration of the flow state of a coal/kerosene slurry while preventing the damage caused by overloading to thereby achieve excellent solid-liquid separation performance. In a solid-liquid separation supplying a dehydrated coal/kerosene slurry to a decanter-type centrifugal separator to separate the coal/kerosene slurry into a solid fraction and a liquid fraction, an opening degree target value is determined on the basis of the difference between a target value and an actually measured value of a torque that acts on a screw conveyor of the decanter-type centrifugal separator, and the opening degree of a flow volume control valve, which is arranged in the middle of a supply line for supplying the coal/kerosene slurry into the decanter-type centrifugal separator, is adjusted to the opening degree target value.

Claims

1. A method for controlling the flow volume of coal/kerosene slurry in a solid-liquid separation process of supplying dehydrated coal/kerosene slurry to a decanter-type centrifugal separator and separating the coal/kerosene slurry into a solid fraction and a liquid fraction, comprising: deciding an opening degree target value on the basis of the difference between a torque target value and a value of a torque acting on a screw conveyer of the decanter-type centrifugal separator measured by a torque detection sensor; adjusting the opening degree of a flow control valve to the opening degree target value, wherein the flow control valve is arranged in the middle of a supply line for supplying the coal/kerosene slurry into the decanter-type centrifugal separator; driving the decanter-type centrifugal separator; and adjusting the torque target value on the basis of the rotary torque detected by the torque detection sensor.

2. A method for controlling the flow volume of coal/kerosene slurry according to claim 1, wherein the opening degree of the flow control valve increases and decreases at a predetermined cycle of opening and closing of the flow control valve.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view showing the outline of an upgraded brown coal producing apparatus according to First Embodiment.

(2) FIG. 2 is a view showing the outline of an upgraded brown coal producing apparatus according to Second Embodiment.

(3) FIG. 3 is a view showing the outline of an upgraded brown coal producing apparatus according to Third Embodiment.

(4) FIG. 4 is a view showing the outline of an upgraded brown coal producing apparatus according to Fourth Embodiment.

(5) FIG. 5 is a graph showing the change of a flow volume in a supply line of an upgraded brown coal producing apparatus according to Fifth Embodiment.

DESCRIPTION OF EMBODIMENTS

(6) Embodiments according to the present invention are explained hereunder in reference to the attached drawings.

First Embodiment

(7) FIG. 1 shows the outline of an upgraded brown coal producing apparatus according to First Embodiment. The upgraded brown coal producing apparatus includes a tank 1 to retain coal/kerosene slurry and a decanter-type centrifugal separator 2 to separate the coal/kerosene slurry supplied from the tank 1 into a solid fraction and a liquid fraction.

(8) The coal/kerosene slurry is supplied arbitrarily to the tank 1. Usually the coal/kerosene slurry is supplied so that a liquid level in the tank 1 may be maintained at a nearly constant level. The liquid level of the coal/kerosene slurry in the tank 1 is detected by a liquid level detection sensor 3.

(9) A pump 5, a first valve 6, and a second valve 7 are connected in sequence from the side of the tank in the middle of a supply line 4 ranging from the tank 1 to the decanter-type centrifugal separator 2. The role of the first valve 6 is to regulate the flow volume of the coal/kerosene slurry supplied into the decanter-type centrifugal separator 2. The role of the second valve 7 is to increase and decrease the flow volume of the coal/kerosene slurry in a predetermined range in the supply line 4 (the detail will be explained in Fifth Embodiment that will be described later). Further, a reflux line 8 to connect a point between the pump 5 and the first valve 6 to the tank 1 is arranged.

(10) The decanter-type centrifugal separator 2 is configured by arranging a cylindrical body 10, which contains a screw conveyer (not shown in the figure), in a separator main body 9. A rotary cylindrical section 12 to rotate by the drive of a motor 11 protrudes from an end section of the screw conveyer. The rotary cylindrical section 12 is supported rotatably by a support plate 13 arranged on the one end side of the separator main body 9. Further, the rotary cylindrical section 12 is connected to the supply line 4 and the coal/kerosene slurry flows in the interior. A rotary shaft 14 protrudes from the other end section of the screw conveyer and is supported rotatably by a support plate 15 arranged on the other end side of the separator main body 9. The rotary torque of the screw conveyer is detected by a torque meter 16. The rotary torque detected by the torque meter 16 is converted into an electric signal (4 to 20 mA DC) by a transmitter 17 and transmitted to a regulator 18. The regulator 18 outputs a control signal to the first valve 6 on the basis of the received detected value of the rotary torque and regulates the opening degree thereof. Although it is not shown in the figure, a solid substance discharge port for discharging a cake (solid substance) obtained by separating a solid from a liquid and a liquid substance discharge port for discharging a liquid substance are formed at the other end section of the separator main body 9.

(11) In an upgraded brown coal producing apparatus configured as stated above, coal/kerosene slurry is separated into a solid fraction and a liquid fraction as follows.

(12) Firstly, on the basis of the relationship between the supply load condition of coal/kerosene slurry supplied to the decanter-type centrifugal separator 2 (the flow volume of coal/kerosene slurry, the concentration of a solid substance contained in the coal/kerosene slurry, or the like; the flow volume of the coal/kerosene slurry is used here) and a torque set value of the decanter-type centrifugal separator 2, a torque target value (SV value: Set Variable) is set beforehand on the basis of an empirical value such as an experimental result.

(13) Then it is also possible to: actually drive the decanter-type centrifugal separator 2; and fine-tune the torque target value (SV value) on the basis of the rotary torque detected by a torque detection sensor (torque detected value).

(14) Successively, an operator inputs the torque target value (SV value) through a DCS (Distributed Control System) in accordance with the difference of the operation condition of the decanter-type centrifugal separator 2 and other conditions. Then feedback control (here, PID control) is applied on the basis of the deviation between the inputted torque target value (SV value) and a torque detected value (PV value: Pressure Variable) sent from the transmitter 17 and an obtained computation value (MV value: Manipulative Variable) is transmitted to the first valve 6 as a manipulation signal. As a result, the opening degree of the first valve 6 is changed in accordance with the manipulation signal and the flow volume is adjusted.

(15) Concretely, the opening degree of the first valve 6 is decided in accordance with the following expression.

(16) $\begin{array}{cc}MV=\frac{100}{PB}\left\{e\left(t\right)\frac{1}{\mathrm{Ti}}e\left(t\right)\mathrm{dt}+\mathrm{Td}\frac{\mathrm{de}\left(t\right)}{\mathrm{dt}}\right\}& \left[\mathrm{Exp}.1\right]\end{array}$
Mv(t): Control output,
e(t): Control deviation (torque target value SVtorque detected value PV),
PB: Proportional band (%),
Ti: Integral time (min.), and
Td: Derivative time (min.)
(PB, Ti, and Td are regulation parameter of control deviation).

(17) The coal/kerosene slurry is supplied from the tank 1 to the decanter-type centrifugal separator 2 by driving the pump 5 while the opening degree of the first valve 6 is regulated as stated above. In the decanter-type centrifugal separator 2, the screw conveyer rotates by the drive of the motor 11 and the coal/kerosene slurry supplied into the rotary cylindrical section 12 is separated into a solid fraction and a liquid fraction. The separated solid substance and liquid substance are discharged from the solid substance discharge port and liquid substance discharge port, respectively.

(18) According to First Embodiment, since the opening degree of the first valve 6 is regulated on the basis of the rotary torque (torque target value SV and torque detected value PV) of the screw conveyer, it is possible to: control the flow volume of the coal/kerosene slurry so as not to overload the decanter-type centrifugal separator 2; and prevent the solid-liquid separation performance from deteriorating.

Second Embodiment

(19) FIG. 2 shows the outline of an upgraded brown coal producing apparatus according to Second Embodiment. The upgraded brown coal producing apparatus is different from an apparatus according to First Embodiment on the following point. Here, in the following explanations, a part corresponding to a configuration according to First Embodiment is represented by an identical code and the explanation thereof is omitted.

(20) The torque meter 16 only detects a rotary torque acting on the screw conveyer and is not used for controlling the opening degree of the first valve 6. Then the value of the electric current applied to the motor 11 to rotate the screw conveyer and the opening degree of the first valve 6 are controlled as follows on the basis of a detection signal of the liquid level detection sensor 3 to detect the liquid level of the coal/kerosene slurry in the tank 1.

(21) That is, cascade control is applied on the basis of the liquid level detected by the liquid level detection sensor 3 and the electric current value of the motor 11 and a set value (SV value) of the electric current applied to the motor 11 is decided so that the liquid level in the tank 1 may take a constant value. Then a computation value (MV value) is calculated in accordance with the expression [Exp.1] stated earlier on the basis of the deviation between the decided set value (SV value) and an actually measured value (PV value), which is detected by a torque detection sensor, of the rotary torque of the screw conveyer. Then the opening degree of the first valve 6 is controlled in accordance with the calculated computation value.

(22) According to Second Embodiment, since the value of the electric current applied to the motor 11 to rotate the screw conveyer and the opening degree of the first valve 6 are controlled on the basis of the liquid level of the coal/kerosene slurry in the tank 1, it is possible to: control the flow volume of the coal/kerosene slurry so as not to overload the decanter-type centrifugal separator 2 while the liquid level of the coal/kerosene slurry in the tank 1 is maintained at a constant level; and prevent the solid-liquid separation performance from deteriorating.

Third Embodiment

(23) FIG. 3 shows the outline of an upgraded brown coal producing apparatus according to Third Embodiment. The upgraded brown coal producing apparatus is different from apparatuses according to First Embodiment and Second Embodiment on the following point. Here, in the following explanations, a part corresponding to a configuration according to First Embodiment or Second Embodiment is represented by an identical code and the explanation thereof is omitted.

(24) In the same manner as First Embodiment, a first torque target value (SV1 value) is set on the basis of the relationship between the supply load condition of coal/kerosene slurry supplied to the decanter-type centrifugal separator 2 and a torque set value of the decanter-type centrifugal separator 2. Then a first computation value (MV1 value), which is a first opening degree target value, is calculated in accordance with the [Exp.1] on the basis of the deviation between the first torque target value (SV1 value) that has been set and a first actually measured value (PV1 value), which is detected by the torque detection sensor, of the rotary torque of the screw conveyer.

(25) Further, in the same manner as Second Embodiment, cascade control is applied on the basis of a liquid level detected by the liquid level detection sensor 3 and an electric current value of the motor 11, and a second set value (SV2 value) of the electric current supplied to the motor 11 is decided so that the liquid level in the tank 1 may take a constant value. Then a second computation value (MV2 value) that is a second opening degree target value is calculated in accordance with the [Exp.1] on the basis of the deviation between the decided second set value (SV2 value) and a second actually measured value (PV2 value) of the electric current supplied to the motor 11 to rotate the screw conveyer.

(26) Then the calculated first computation value (MV1 value) and second computation value (MV2 value) are compared (Low Select) and the opening degree of the first valve 6 is controlled on the basis of the smaller computation (electric current) value.

(27) According to Third Embodiment, since the opening degree of the first valve 6 is regulated by the smaller of the first computation value (MV1 value) and the second computation value (MV2 value), rapid change of the opening degree does not occur. As a result, it is possible to appropriately separate the coal/kerosene slurry into a solid fraction and a liquid fraction while the coal/kerosene slurry is conveyed in a more stable state in comparison with First Embodiment and Second Embodiment.

Fourth Embodiment

(28) FIG. 4 shows the outline of an upgraded brown coal producing apparatus according to Fourth Embodiment. The upgraded brown coal producing apparatus is different from an apparatus according to First Embodiment on the following point. Here, in the following explanations, a part corresponding to a configuration according to First Embodiment is represented by an identical code and the explanation thereof is omitted.

(29) In the same manner as First Embodiment, a first torque target value (SV1 value) is set on the basis of the relationship between the supply load condition of coal/kerosene slurry supplied to the decanter-type centrifugal separator 2 and a torque set value of the decanter-type centrifugal separator 2. Then a first computation value (MV1 value) that is a first target opening degree is calculated in accordance with the [Exp.1] on the basis of the deviation between the first torque target value (SV1 value) that has been set and a first actually measured value (PV1 value), which is detected by the torque detection sensor, of the rotary torque of the screw conveyer.

(30) Further, in the same manner as Second Embodiment, cascade control is applied on the basis of a liquid level detected by the liquid level detection sensor 3 and an electric current value of the motor 11, and a second set value (SV2 value) of the electric current supplied to the motor 11 is decided so that the liquid level in the tank 1 may take a constant value. Then a second computation value (MV2 value) that is a second target opening degree is calculated in accordance with the [Exp.1] on the basis of the deviation between the decided second set value (SV2 value) and a second actually measured value (PV2 value) of the electric current supplied to the motor 11 to rotate the screw conveyer.

(31) Further, a slurry flow volume to be a target is decided so that the liquid level of the coke/kerosene slurry in the tank 1 may take a constant value. Furthermore, a slurry flow meter 19 is arranged in the supply line 4 and the flow volume of the coke/kerosene slurry flowing in the supply line 4 is detected. Then cascade control is applied on the basis of the deviation between the target value of the slurry flow volume and the detected value of the slurry flow volume detected by the slurry flow meter 19 and a third computation value (MV3 value) that is a third opening degree target value is calculated by the [Exp.1].

(32) Successively, the opening degree of the first valve 6 is controlled on the basis of the smallest value of the calculated first computation value (MV1), second computation value (MV2), and third computation value (MV3).

(33) According to Fourth Embodiment, since the opening degree of the first valve 6 is subjected to feedback control on the basis of the smallest value of the first computation value (MV1), the second computation value (MV2), and additionally the third computation value (MV3) of the first valve 6 calculated from the set value (SV3 value) and the actually measured value (PV3) of the slurry flow volume, it is possible to appropriately separate the coal/kerosene slurry into a solid fraction and a liquid fraction while the coal/kerosene slurry is conveyed in a still more stable state in comparison with Third Embodiment.

Fifth Embodiment

(34) In an upgraded brown coal producing apparatus according to Fifth Embodiment, the following control capable of being adopted in any of the configurations according to First to Fourth Embodiments is applied.

(35) That is, a tiny variation is given to the opening degree of the first valve 6 in the supply line 4. Concretely, as shown in the graph of FIG. 5, the opening degree of the first valve 6 is increased and decreased at a constant period (t) and so-called tact control is applied. As a result, it is possible to prevent the clogging of the supply line 4, in particular the first valve 6. Here, the period (t) and the amplitude of the increase and decrease (X %: for example 1%) may arbitrarily be set in response to the flow condition (the difference of the inner diameter of the supply line 4 and others) of the coal/kerosene slurry and can be set at appropriate values by experiment or the like. Further, when tact control is applied by the first valve 6, it is also possible to apply flow control by changing the opening degree of the first valve 6 or by changing the opening degree of the second valve 7.

(36) According to Fifth Embodiment, it is possible to effectively prevent the clogging of the coal/kerosene slurry in the supply line 4, in particular in the flow control valve by increasing and decreasing the flow volume of the coal/kerosene slurry in the supply line 4 in a certain range.

REFERENCE SIGNS LIST

(37) 1 Tank 2 Decanter-type centrifugal separator 3 Liquid level detection sensor 4 Supply line 5 Pump 6 First valve (flow control valve) 7 Second valve 8 Reflux line 9 Separator main body 10 Cylindrical body 11 Motor 12 Rotary cylindrical section 13 Support plate 14 Rotary shaft 15 Support plate 16 Torque meter 17 Transmitter 18 Regulator