JP2002022363A - Dryer for powder and granular material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the outlet moisture content of powder and granular material to be dried at a constant level even when the inlet moisture content varies significantly. SOLUTION: A plurality of heat exchanger tubes 7 are arranged in a drum 3 turning about an inclining axis in parallel with the axis of the drum 3, pulverized coal to be dried is fed into the heat exchanger tubes and heat source fluid, i.e., steam, is fed into the space between the outer circumferential surface of the heat exchanger tubes 7 and the inner circumferential surface of the drum 3 thus drying the pulverized coal. Dry air is sucked into the heat exchanger tubes by means of an induced draft fan 45 and exhaust gas, i.e., mixture gas of steam generated from the pulverized coal during drying operation and the sucked air, is discharged. When suction of dry air increases, relative humidity on the periphery of the pulverized coal decreases to accelerate drying. Furthermore, since oxygen concentration in the exhaust gas also increases, moisture of the pulverized coal can be controlled accurately in safety by controlling the flow rate of exhaust gas such that the oxygen concentration in the exhaust gas has a target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granule dryer, and more particularly to a granule dryer suitably used for drying coking coal.

[0002]

2. Description of the Related Art Conventionally, rotary indirect heating dryers have been used as dryers for powdery and granular materials. The rotary indirect heating dryer includes a substantially cylindrical rotatable drum and a plurality of heat transfer tubes provided in the drum and extending in the axial direction of the drum. In this dryer, for example, an object to be dried is supplied into a heat transfer tube, and steam as a heat source is supplied to a space between the outer peripheral surface of the heat transfer tube and the inner peripheral surface of the drum. The object to be dried moves from the inlet side to the outlet side as the drum rotates, while being indirectly heated by the steam.

[0003] The control of the outlet moisture in this dryer is performed by adjusting the drying capacity as follows. (A) The drying capacity is adjusted by adjusting the pressure of steam as a heat source. That is, when increasing the drying capacity, the pressure of the steam is increased, and when decreasing the drying capacity, the pressure of the steam is decreased. (B) Adjust the drying speed by adjusting the rotation speed of the drum. That is, when increasing the drying capacity, the rotation speed is decreased to increase the residence time, and when decreasing the drying capacity, the rotation speed is increased to decrease the residence time.

[0004] Such a conventional adjustment method has the following problems. In the method of adjusting the pressure of steam, the maximum pressure must be increased in order to increase the pressure adjustment amount, and if the maximum pressure is increased, the heat transfer tube or the drum may be damaged. Therefore, it is necessary to increase the thickness of the heat transfer tube and the thickness of the drum. This leads to an increase in the weight of the dryer and an increase in equipment costs. In the method of adjusting the rotation speed of the drum, when the rotation speed is reduced, the drying capacity increases, but the amount of stagnation increases, and the productivity decreases. On the other hand, if the rotation speed is excessively increased, the rotating power increases and the object to be dried is pressed against the heat transfer tube by the centrifugal force, which makes it difficult to move the object to be dried. Therefore, in the conventional granule dryer, upper limits are set for the pressure of steam and the rotation speed of the drum, and the operation is performed within the range.

[0005]

As described above, since the upper limit is set for the pressure of steam and the rotation speed of the drum in the conventional powder dryer, the control range of the outlet moisture is narrow. There is a problem that it is difficult to keep the outlet moisture content constant when the supply flow rate of the material to be dried and the inlet moisture content vary greatly.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a powder granule capable of keeping the outlet moisture content constant even when the supply flow rate of the granules to be dried and the inlet moisture content vary greatly. It is to provide a body dryer.

[0007]

SUMMARY OF THE INVENTION The present invention is a kiln having a kiln body divided into first and second spaces by a heat transfer member, wherein the kiln body is driven to rotate about its axis, A kiln in which the powdery material to be dried supplied to the first space from one end in the direction is indirectly heat-exchanged by the heat source fluid supplied to the second space and discharged from the other end in the axial direction; and the one end of the kiln Gas transport means for discharging gas supplied from any one of the section or the other end and gas generated from the granular material during indirect heat exchange, a heat source fluid source for supplying a heat source fluid to the second space, Gas component concentration detecting means for detecting the concentration of the composition component of the gas discharged from the kiln by the gas conveying means, and the flow rate of the gas discharged from the kiln by the gas conveying means in response to the output of the gas component concentration detecting means A dryer particulate material which comprises a control means for controlling.

According to the present invention, the concentration of a composition component of a gas discharged from the kiln, for example, oxygen or nitrogen, is detected, and the flow rate of the gas discharged from the kiln is controlled according to the detected concentration. The gas discharged from the kiln is composed of water vapor evaporating from the granular material to be dried and gas supplied from at least one of the one end and the other end of the kiln, for example, air. By detecting the oxygen or nitrogen concentration of the gas
It is possible to know the mixing ratio of water vapor and air, that is, the humidity of the gas around the granular material. Since air is a relatively dry gas compared to water vapor, the humidity decreases as the supply amount of air increases. In addition, the drying speed of the granular material to be dried increases as the humidity of the surrounding gas decreases,
Higher is lower. Further, the flow rate of air supplied to the kiln is proportional to the flow rate of gas discharged from the kiln. Therefore, as the flow rate of the gas discharged from the kiln is increased, the concentration of oxygen or nitrogen in the gas increases, and the humidity of the gas around the granular material decreases. Thus, by detecting the composition of the gas discharged from the kiln, it is possible to know the mixing ratio between the gas supplied from the outside and the water vapor, so if the discharge flow rate of the gas is adjusted accordingly, The humidity around the granules can be adjusted, and the drying speed of the granules can be controlled. Therefore,
The outlet water content can be kept constant even when the supply flow rate of the powder to be dried and the inlet water content vary greatly. In addition, since the composition of the gas discharged from the kiln is detected, the oxygen concentration can be controlled below the explosive limit concentration even if the pulverized material is, for example, pulverized coal, thereby preventing explosion and ignition during drying. can do.

According to the present invention, the kiln has a cylindrical kiln body, the axis of which is inclined such that the one end is higher than the other end, and the heat transfer member is a kiln. A plurality of heat transfer tubes parallel to an axis of the main body, wherein the first space is one of a space between an inner peripheral surface of the kiln main body and an outer peripheral surface of the heat transfer tubes or a space in the heat transfer tubes; The second space is either the space between the inner peripheral surface of the kiln body and the outer peripheral surface of the heat transfer tube or the space inside the heat transfer tube, and the heat source fluid source is a steam source that supplies steam whose pressure can be adjusted. It is characterized by being.

According to the present invention, since the kiln is inclined, the granular material can be transferred while drying by rotating the kiln. Further, since the residence time of the granular material can be adjusted by adjusting the rotation speed, the drying speed can be controlled. Further, the first space to which the granular material is supplied is either one of the space inside the heat transfer tube and the space outside the heat transfer tube, and the second space to which the heat source fluid is supplied is opposite to the first space across the heat transfer tube. Because it is a space of
The granular material can be indirectly heated by the heat source fluid.
Therefore, as compared with direct heating such as hot-air drying, the carry-out energy of the exhaust gas can be reduced, and the thermal efficiency can be increased. In addition, since the heat source fluid is water vapor, heat of condensation can be generated and heating can be performed efficiently.

Further, the present invention is characterized in that the gas conveying means is an inducing fan for inducing gas.

According to the present invention, since the gas conveying means is an induction fan, it is possible to prevent the gas from escaping to the outside and reduce the amount of dust generated.

Further, the present invention is characterized in that an inlet flow control valve for controlling a flow rate of gas supplied to one end of the kiln is provided.

According to the present invention, since the flow rate of the gas supplied to one end of the kiln is controlled by the inlet flow control valve, the humidity of the gas around the granular material is adjusted to reduce the drying speed of the granular material. Can be controlled. For example, if the opening degree of the inlet flow control valve is increased, the flow rate of the gas supplied to the first space by the gas conveying means is increased, and the humidity of the gas around the granular material is reduced, so that the drying speed of the granular material is reduced. Can be raised.

Further, the present invention is characterized in that an outlet flow control valve for controlling the flow rate of gas supplied to the other end of the kiln is provided.

According to the present invention, the flow rate of the gas supplied to the other end of the kiln is controlled by the outlet flow control valve. Can be controlled. For example, if the opening of the outlet flow control valve is increased by closing the inlet flow control valve, most of the gas discharged by the gas conveying means is occupied by the gas supplied to the other end of the kiln, so that the first space The flow rate of the gas supplied to the powder decreases, the humidity of the gas around the powder increases, and the drying speed of the powder decreases.

Further, according to the present invention, the gas supplied to one end or the other end of the kiln is a gas other than air, and a return pipe for returning a part of the gas discharged by the gas discharging means to one end of the kiln. Is provided.

According to the present invention, gas consisting of gas other than the space is supplied to one end or the other end of the kiln, and a part of the gas discharged by the gas discharging means is returned to one end of the kiln. In addition, the consumption of gas other than air, for example, nitrogen gas can be reduced. Also, since a gas composed of a gas other than air is supplied, even if the supply amount of the gas is increased, the oxygen concentration around the granular material can be kept low,
Explosion and ignition during drying can be prevented even if the pulverized material is pulverized coal. Therefore, the drying speed of the granular material can be safely increased.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing a schematic configuration of a granular material dryer 1 according to an embodiment of the present invention.
FIG. 2 is a simplified cross-sectional view showing the configuration of a main part of the granular material dryer 1 shown in FIG. 1, and FIG.
It is sectional drawing seen from -III. The granule dryer 1 (hereinafter, abbreviated as “dryer”) is used for drying coke coking coal (hereinafter, referred to as “pulverized coal”), which is a granule, for example. Even if the moisture content of the coal fluctuates, drying is performed so that the moisture content of the pulverized coal after drying becomes a predetermined value.

The dryer 1 has a kiln 2, and the kiln 2 has a drum 3 as a kiln body. The drum 3 is partitioned into a first space and a second space by a heat transfer tube 7 that can be called a plurality of tubes that are heat transfer members. In the present embodiment, the first space is set to a space inside the heat transfer tube 7,
The second space is set as a space between the inner peripheral surface of the drum 3 and the outer peripheral surface of the heat transfer tube 7. The first and second spaces may be set oppositely. The drum 3 is driven to rotate around its axis 3a, pulverized coal to be dried is supplied to the first space from one end in the axial direction, and steam as the heat source fluid is supplied to the second space. The pulverized coal to be dried is indirectly heat-exchanged by steam and discharged from the other end in the axial direction.
Hereinafter, the one end in the axial direction (left side in FIG. 1) to which pulverized coal is supplied may be referred to as an inlet, and the other end in the axial direction may be referred to as an outlet. The axis 3a of the drum 3 is inclined such that the one end is higher than the other end.

The drum 3 includes a substantially cylindrical body plate 4 and a body plate 4.
And inlet and outlet tubesheets 5 and 6 for closing one end and the other end, respectively. The dimensions of the drum 3 are, for example, diameter:
3 to 8 m, length: 7 to 12 m. In the drum 3,
A plurality of heat transfer tubes 7 extending in parallel along the axis of the drum 3 are provided, and both end portions of each heat transfer tube 7 pass through the inlet and outlet tube plates 5 and 6 and open to the outer surface, respectively. I have. The diameter of the heat transfer tube 7 is, for example, 200 mm.

First and second rotating shafts 8, 9 of the drum 3 are provided at central positions of the inlet and outlet tube sheets 5, 6, respectively, so as to protrude outward from the outer surface. The first and second rotating shafts 8 and 9 are hollow bodies, and the axes of the first and second rotating shafts 8 and 9 are on an extension of the axis 3 a of the drum 3. The first and second rotating shafts 8 and 9 are provided with first and second rotating shafts 8 and 9 respectively.
The first rotating shaft 8 is connected to an electric motor 12 rotatably supported by bearings 10 and 11. The electric motor 12
The drum 3 is driven to rotate around the axis. The rotation speed of the electric motor 12, that is, the rotation speed of the drum 3 is controlled by an inverter. The motor 12 is provided with a tachometer 47 as a tachometer.
Detects the rotation speed of the drum 3. The rotation speed of the drum 3 is, for example, 3 to 15 rpm.

A steam introducing pipe 13 for guiding steam into the drum 3 is coaxially arranged in the second rotating shaft 9 and the internal space of the drum 3. The distal end of the steam introduction pipe 13 is disposed on the inlet tube plate 5, and the base end of the steam introduction pipe 13 projects outward from the shaft end of the second rotating shaft 9. Steam introduction pipe 1
In a portion existing in the drum 3, a plurality of steam outlets 14 are formed at intervals in the axial direction. In the space between the outer peripheral surface of the steam introduction pipe 13 and the inner peripheral surface of the second rotating shaft 9, a condensed water discharge pipe 15 is provided at an interval radially outward of the steam introduction pipe 13.

In the vicinity of the outlet tube sheet 6 of the drum 3, a condensed water collecting pipe 16 is provided at an interval outward from the outer surface of the outlet tube sheet 6. One end of the condensed water collecting pipe 16 is connected to a corner formed by the body plate 4 and the outlet tube plate 6, and the other end of the condensed water collecting pipe 16 is connected via the second rotating shaft 9 to the condensed water collecting pipe 16. It is connected to the discharge pipe 15. The base end of the steam introduction pipe 13 is connected to a rotary joint 18, and the condensed water discharge pipe 15 is connected to the rotary joint 18 via a connecting pipe 19. The rotary joint 18 has a steam inlet 20 and a condensed water outlet 2.
The steam inlet 20 is rotatably connected to the steam inlet pipe 13, and the condensed water outlet 21 is connected rotatably to the condensed water outlet pipe 15 via the connecting pipe 19.

A plurality of charging chutes 23 are provided in the vicinity of the inlet tube sheet 5 of the drum 3. Throwing chute 23
Supplies the pulverized coal 17 to be dried toward the inlet tube sheet 5, and supplies the pulverized coal 17 into the plurality of heat transfer tubes 7 opened on the outer surface of the inlet tube sheet 5. In each heat transfer tube 7, a retarder 22 for stirring the pulverized coal 17 supplied into the heat transfer tube is provided. The input chute 23 and the vicinity of the inlet tube sheet 5 of the drum 3 are surrounded by an inlet hood 24. An inlet gas inlet 25 is provided below the inlet hood 24, and an inlet flow control valve 26 is provided in the inlet gas inlet 25. The inlet gas inlet 25 takes in an inert gas which is air or a gas other than air. Inert gas is
For example, nitrogen gas.

An inlet conveyor 28 is provided above the inlet hood 24, and the inlet conveyor 28 supplies the pulverized coal to be dried to the charging chute 23. The inlet conveyor 28 is provided with an inlet moisture meter 29 and a powder flow meter 30. The inlet moisture meter 29 detects the moisture content of the pulverized coal to be dried, and the particulate material flow meter 30 detects the supply weight of the pulverized coal supplied by the inlet conveyor 28 per unit time. As shown in FIG. 3, the pulverized coal 17 supplied into the heat transfer pipe 7
After moving along the inner wall of the heat transfer tube 7, it moves from the inlet to the outlet while repeating the falling motion. The air or inert gas taken into the inlet hood 24 from the inlet gas inlet 25 is supplied into the heat transfer tube 7 and transports the steam generated from the pulverized coal 17 during drying from the inlet to the outlet. As described above, the reason why the inlet gas inlet 25 is provided below the inlet hood 24 is to facilitate introduction of air or inert gas into the heat transfer tube 7.

A steam supply pipe 48 is connected to the steam inlet 20, and a pressure control valve 49 is connected to the steam supply pipe 48.
And a pressure gauge 50 as pressure detecting means. The pressure adjusting valve 49 adjusts the pressure of steam supplied from a steam source (not shown). The pressure control valve 49 and the steam generation source constitute a heat source fluid source. The pressure gauge 50 is interposed between the pressure regulating valve 49 and the steam inlet 20, and detects the pressure of steam as a heat source fluid.

The water vapor supplied from the water vapor source is guided to the water vapor introduction pipe 13 via the pressure regulating valve 49 and the rotary joint 18, and is discharged from the water vapor outlet 14 into the second space. The water vapor ejected into the second space flows between the outer peripheral surfaces of the plurality of heat transfer tubes 7 and contacts the outer peripheral surfaces of the heat transfer tubes 7. The water vapor that has come into contact with the heat transfer tube 7 is condensed to generate condensed water and also generates heat of condensation. The heat of condensation is transferred to the pulverized coal in the heat transfer tube to dry the pulverized coal. Water vapor generated from pulverized coal during drying is mixed with air or an inert gas supplied into the heat transfer tube to form exhaust gas. The condensed water generated on the outer peripheral surface of the heat transfer tube 7 flows down along the outer peripheral surface of the heat transfer tube 7,
It is stored near the lowest point of the corner formed by the body plate 4 and the outlet tube sheet 6. The stored condensed water flows into the condensed water collecting pipe 16 when the condensed water collecting pipe 16 reaches the lowermost point of the corner portion by the rotation of the drum 3 as shown in FIG.
The condensed water that has flowed into the condensed water discharge pipe 1
5 is reached, the condensed water discharge pipe 15
Spills into. The condensed water which has flowed into the condensed water discharge pipe 15 is condensed water discharge port 2 of the rotary joint 18 via the connecting pipe 19.
Emitted from 1.

The vicinity of the outlet tube sheet 6 of the drum 3 is surrounded by an outlet hood 33. An outlet gas inlet 34 is provided below the outlet hood 33, and the outlet gas inlet 3
4 is provided with an outlet flow control valve 35. The outlet flow control valve 35 takes in air or an inert gas. An outlet conveyor 36 is provided below the outlet hood 33,
The outlet conveyor 36 conveys the dried pulverized coal. The outlet conveyor 36 is provided with an outlet moisture meter 37, and the outlet moisture meter 37 detects the moisture content of the dried pulverized coal. An upper end of the outlet hood 33 is connected to one end of an exhaust gas pipe 39, and the other end of the exhaust gas pipe 39 is connected to a chimney 40. The exhaust gas channel 39 guides exhaust gas transported from inside the heat transfer tube to the downstream side. In the exhaust gas line 39, a gas component concentration detecting means 41, a thermometer 42, a bag filter 4
3. The exhaust gas throttle valve 44 and the induction fan 45 are provided in this order from the upstream side to the downstream side in the exhaust gas flow direction. The exhaust gas throttle valve 44 may be provided downstream of the induction fan 45.

The gas component concentration detecting means 41 is an analyzer for detecting the concentration of the constituent components of the exhaust gas, and is realized, for example, by an oxygen meter for detecting the oxygen concentration in the exhaust gas. The gas component concentration detecting means 41 may be a nitrogen meter for detecting the nitrogen concentration in the exhaust gas. The thermometer 42 detects the temperature of the exhaust gas, and the bag filter 43 collects dust contained in the exhaust gas. The exhaust gas throttle valve 44 adjusts the valve opening degree to adjust the exhaust gas flow rate. The induction fan 45 is, for example, a centrifugal fan, and generates a suction force to form a gas flow in the dryer 1. Since the gas flow is formed by the suction force, the ejection of the gas to the outside is prevented, and the amount of dust generation can be reduced.

The pulverized coal to be dried supplied from the inlet conveyor 28 is guided into the heat transfer tube via the inlet hood 24 and is heated and dried by the steam supplied to the outer peripheral surface of the heat transfer tube 7. It moves to the outlet side with rotation and is led out onto the outlet conveyor 36 via the outlet hood 33. The air or the inert gas taken in from the inlet and outlet gas inlets 25 and 34 by the suction force of the attraction fan 45 is mixed with water vapor generated from the granular material during transportation to form an exhaust gas. From the chimney 40 to the atmosphere.

FIG. 4 is a block diagram showing the electrical configuration of the granular material dryer 1 shown in FIG. Inlet moisture meter 29, powder flow meter 30, rotational speed meter 47, pressure gauge 50, oxygen meter 4
1 and the thermometer 42 detect each physical quantity to be detected and derive an output representing the physical quantity. The processing circuit 53, which is a control means, responds to each of the outputs, and
The motor 12, the pressure regulating valve 49, and the exhaust gas are set so that the steam pressure and the target value of the oxygen concentration in the exhaust gas are respectively set so that the rotational speed of the drum 3, the pressure of the steam and the oxygen concentration in the exhaust gas become the target values. The throttle valve 44 and the inlet and outlet flow control valves 26 and 35 are drive-controlled.

In the present embodiment, a dry gas, that is, air or an inert gas is sucked and taken in from the outside into the heat transfer tube, and mixed with water vapor generated from the pulverized coal to be dried in the heat transfer tube to remove the exhaust gas. The pulverized coal is configured to control the drying rate of pulverized coal by adjusting the amount of exhaust gas discharged to control the suction amount of dry gas from the outside and the relative humidity around the pulverized coal. In addition, since the concentration of the constituent components of the exhaust gas fluctuates depending on the amount of dry gas sucked from the outside, the relative humidity is adjusted based on the concentration of the constituent components of the exhaust gas to control the drying speed of the pulverized coal. Have been.
Further, pressure control of steam as a heat source fluid and drum 3
The drying speed of pulverized coal is controlled by controlling the rotation speed of the pulverized coal. Such control is performed as described below based on the following experimental results on which the present invention is based.

FIG. 5 is a graph showing the relationship between the difference in water content at the entrance and exit of pulverized coal and the rotation speed of the drum 3. The rotational speed of the drum 3 is a constant upper limit rotational speed Rmax in a region where the difference in moisture content at the entrance and exit of the pulverized coal (hereinafter, may be abbreviated as “moisture difference”) is W1 or less.
And in a region where the moisture difference exceeds W1, it is set to decrease as the moisture difference increases. The upper limit rotation speed is set because the smaller the difference in moisture, the shorter the residence time of the pulverized coal in the heat transfer tube,
Although the productivity can be improved by increasing the rotation speed of the drum 3, if the rotation speed is too high, the driving power increases, and the pulverized coal is pressed against the inner wall of the heat transfer tube by centrifugal force, making it difficult to move. This is because productivity decreases. The reason why the rotation speed decreases as the moisture difference increases is that the residence time of the pulverized coal in the heat transfer tube needs to be increased as the moisture difference increases. The water difference W
1 and the upper limit rotation speed Rmax are set in advance for each dryer 1 based on experimental results.

FIG. 6 is a graph showing the relationship between the difference in water content at the entrance and exit of pulverized coal and the pressure of steam as a heat source fluid. The water vapor pressure is set to be higher as the water difference increases in a region where the water difference is small,
In the region where the moisture difference exceeds W2, a certain upper limit pressure Pmax
Is set to The reason why the water vapor pressure is set to be higher as the water difference increases in the region where the water difference is small is that the drying ability can be increased in accordance with the water difference. The upper limit pressure Pmax is set to the steam pressure in the region where the moisture difference is large because the upper limit pressure Pma
If a pressure exceeding x is applied, the drum 3 may be damaged. The water difference W2 and the upper limit pressure Pmax are set in advance for each dryer 1 based on a pressure resistance standard.

FIG. 7 is a graph showing the relationship between the oxygen concentration and the coal dust concentration in the boundary region between the explosion region and the non-explosion region of pulverized coal. The hatched area in FIG. 7 indicates an explosion area, and the symbols △, ，, and □ indicate coal types. From FIG. 7, there is a risk of explosion regardless of the coal type and coal dust concentration when the oxygen concentration exceeds 14%. Conversely, if the oxygen concentration is suppressed to 14% or less, regardless of the coal type and coal dust concentration, It turns out that the explosion can be prevented.

FIG. 8 is a graph showing the relationship between the relative humidity of the exhaust gas and the difference in the water content at the entrance and exit of pulverized coal. FIG. 8 shows that the water difference increases as the relative humidity of the exhaust gas decreases. In other words, it can be seen that when the water difference is large, it is necessary to reduce the relative humidity of the exhaust gas. That is, if the relative humidity of the exhaust gas is reduced, the drying speed of the pulverized coal can be increased, and the drying ability of the dryer can be increased. With this, if you set the moisture difference,
A target value of the relative humidity of the exhaust gas can be set.

FIG. 9 is a graph showing the relationship between the oxygen concentration in the exhaust gas and the relative humidity of the exhaust gas when air is supplied from the outside into the heat transfer tube. Straight lines 54, 55, 56 in FIG.
Is a graph when the exhaust gas temperature is 70 ° C., 80 ° C., and 90 ° C., respectively. FIG. 9 shows that the relative humidity of the exhaust gas decreases as the oxygen concentration in the exhaust gas increases. In addition, comparing the same concentration of oxygen in the exhaust gas, it can be seen that the higher the exhaust gas temperature, the lower the relative humidity of the exhaust gas. The relative humidity of the exhaust gas is preferably 70% or less. This is because the relative humidity of the exhaust gas is 70%
This is because if the ratio exceeds, the drying speed becomes slow and large equipment is required. As described above, the oxygen concentration in the exhaust gas is limited to 14% or less due to the explosion limit of pulverized coal. Therefore, in order to reduce the relative humidity of the exhaust gas to 70% or less, the exhaust gas temperature must be 8% or less.
It must be at least 0 ° C.

FIG. 10 shows the oxygen concentration in the exhaust gas and the relative humidity of the exhaust gas when nitrogen gas as an inert gas is blown into the inlet hood 24 and a mixed gas of nitrogen gas and air is supplied into the heat transfer tube. 6 is a graph showing the relationship of. Straight lines 57, 58, 59, and 60 in FIG. 10 are graphs when the nitrogen concentration in the exhaust gas is 45%, 55%, 65%, and 75%, respectively. The exhaust gas temperature in FIG.
It is. The straight line 55 in FIG. 10 is the same as the straight line 55 in FIG.

FIG. 10 shows that as the oxygen concentration in the exhaust gas increases, the relative humidity of the exhaust gas decreases irrespective of the nitrogen concentration in the exhaust gas. In addition, when the oxygen concentration in the exhaust gas is made the same and compared, it is found that the higher the nitrogen concentration in the exhaust gas, the lower the relative humidity of the exhaust gas. Comparing the straight line 55 in which only the air is supplied without blowing the inert gas and the straight lines 57 to 60 in which the inert gas is blown, in the region where the oxygen concentration in the exhaust gas is 14% or less of the explosion limit, Straight line 5 where the nitrogen concentration in the exhaust gas is 55% or more
It can be seen that the relative humidity at 8,59,60 is lower than the relative humidity at line 55.

As a result, the relative humidity of the exhaust gas can be reduced and the oxygen concentration can be easily reduced to 14% or less of the explosion limit as the amount of nitrogen gas, which is an inert gas, is increased. If a graph as shown in FIG. 10 is created for each exhaust gas temperature, the relationship among the relative humidity of the exhaust gas, the exhaust gas temperature, and the concentrations of oxygen and nitrogen in the exhaust gas can be easily grasped.

FIG. 11 is a flowchart for explaining the operation of the processing circuit 53 shown in FIG. 4 when supplying air from outside to the heat transfer tube. In step a1, the outlet moisture content of the pulverized coal after drying is set and the operation is started.
In step a2, the inlet water content before drying and the supply flow rate of pulverized coal are detected. In step a3, a water difference which is a difference between the outlet water content and the inlet water content is obtained.

In step a4, target values of the rotation speed of the drum 3 and the pressure of steam as the heat source fluid are set. This is set according to the moisture difference based on FIGS. 5 and 6, respectively. In step a5, the rotation speed of the drum 3 and the pressure of water vapor are detected.
In step a6, it is determined whether or not the rotation speed of the drum 3 and the pressure of the water vapor match the respective target values. If this determination is negative, the process proceeds to step a7,
If affirmative, the process proceeds to step a8.

In step a7, adjustment is performed so that the rotation speed and the pressure of steam match the target values, and the process returns to step a5 again. This step a5, step a
6, the processing of steps a7 and a5 is repeated until the determination of step a6 becomes positive. Step a
In step 8, the concentration of oxygen in the exhaust gas is measured, and step a
At 9, the exhaust gas temperature is measured.

In step a10, a target value of the oxygen concentration in the exhaust gas is set. The target value of the oxygen concentration in the exhaust gas is obtained by calculating the relative humidity of the exhaust gas corresponding to the obtained moisture difference from FIG. 8, and calculating the oxygen concentration in the exhaust gas corresponding to the obtained relative humidity and the measured exhaust gas temperature in FIG. Is set by asking for When the oxygen concentration in the exhaust gas thus set exceeds the explosion limit of 14%, the oxygen concentration of 14% or less is reset as the target value. In step a11, it is determined whether or not the measured value of the oxygen concentration in the exhaust gas matches the target value. If the determination is negative, the process proceeds to step a12. If the determination is positive, the process proceeds to step a13.

In step a12, the flow rate of the exhaust gas is adjusted so that the oxygen concentration in the exhaust gas matches the target value. This adjustment is performed by increasing the valve opening of the exhaust gas throttle valve 44 when it is necessary to increase the oxygen concentration, increasing the amount of dry air introduced from the inlet, and reducing the oxygen concentration by reducing the oxygen concentration. This is performed by reducing the valve opening of the valve to reduce the amount of dry air introduced from the inlet. Further, when the moisture difference and the supply flow rate of the pulverized coal are large and it is necessary to increase the drying speed of the pulverized coal, the exhaust flow control valve 26 is opened, and the outlet flow control valve 35 is closed. Adjustment of valve 44 is performed. This facilitates introduction of dry air from the inlet into the heat transfer tube, and facilitates increasing the drying speed. In addition, the water difference and the supply flow rate of pulverized coal are small,
When it is necessary to reduce the drying speed of the pulverized coal, the exhaust gas throttle valve 44 is adjusted with the inlet flow control valve 26 closed and the outlet flow control valve 35 opened. As a result, exhaust gas does not contribute to drying.
Since the ratio of the air taken in from Step 5 becomes very large and the flow rate of air introduced from the inlet into the heat transfer tube is greatly reduced, the drying speed can be reduced. Step a1
After the adjustment of the exhaust gas flow rate in step 2, the process returns to step a8 again. After Steps a8 to a12, Step a8 is performed again.
Is repeated until the determination in step a11 becomes affirmative. In step a13, the operation of the processing circuit 53 for one cycle ends.

As described above, the relative humidity of the exhaust gas is set according to the moisture difference, and the target value of the oxygen concentration in the exhaust gas is set based on the relative humidity. Since the flow rate is controlled, the drying speed of the pulverized coal can be accurately controlled. Therefore, even when the inlet moisture content and the supply flow rate of the pulverized coal to be dried vary greatly, the outlet moisture content can be kept constant. Further, since the target value of the oxygen concentration in the exhaust gas is set, the oxygen concentration can be controlled to a concentration below the explosion limit, and explosion and ignition can be prevented.

In the flow chart shown in FIG. 11, although only air is introduced as a humidity adjusting gas into the heat transfer tube, nitrogen gas, which is an inert gas, is blown into the inlet hood 24, and the heat transfer tube To supply a mixed gas of nitrogen gas and air taken in at the time of pulverized coal supply. The flowchart showing the operation of the processing circuit 53 in this case is exactly the same except that the measurement of the oxygen concentration in the exhaust gas in step a8 in FIG. 11 is replaced with the measurement of the oxygen concentration and the nitrogen concentration in the exhaust gas. Illustration is omitted.

The target value of the oxygen concentration in the exhaust gas in this case is obtained by calculating the relative humidity of the exhaust gas corresponding to the moisture difference obtained as described above from FIG. It is set by obtaining the oxygen concentration in the exhaust gas corresponding to the nitrogen concentration in FIG. When the oxygen concentration in the exhaust gas set in this way exceeds the explosion limit of 14%, the oxygen concentration becomes 14%.
Although the following oxygen concentrations are reset as target values,
In the case of blowing nitrogen gas, the oxygen concentration in the exhaust gas is reduced, so that it is hardly reset. The other operations of the processing circuit 53 are the same as the operations shown in FIG. As the amount of nitrogen gas, which is an inert gas, is blown in a larger amount, the degree of decrease in relative humidity can be increased, and the oxygen concentration can be reliably reduced to 14% or less of the explosion limit of oxygen concentration. Therefore, there is no danger of explosion as compared with the case where only air is introduced by blowing nitrogen gas which is an inert gas, and the drying speed of pulverized coal can be increased. The inert gas is not limited to nitrogen gas, and another inert gas may be blown.

FIG. 12 is a simplified diagram showing an example of the configuration of the exhaust gas throttle valve 44 shown in FIG. Exhaust gas throttle valve 4
Reference numeral 4 denotes a so-called louver-shaped flow control valve in which a plurality of angularly displaceable valve elements 61 are arranged across the flow path, and the plurality of valve elements 61 are simultaneously angularly displaced to adjust the exhaust gas flow rate. In the present embodiment, there is no need to reduce the exhaust gas flow rate to zero, so it is not necessary to airtightly close the exhaust gas line 39. Therefore, a throttle valve that is less expensive than such a butterfly valve is preferably used.

FIG. 13 is a system diagram showing a schematic configuration of a granular material dryer 63 according to another embodiment of the present invention.
The granule dryer 63 is similar to the granule dryer 1, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.
It should be noted that a return line 64 for returning a part of the exhaust gas to the inlet hood 24 is provided. One end of the return pipe 64 is connected to the outlet side of the induction fan 45 of the exhaust gas pipe 39, and the other end is connected to the inlet hood 24. A condenser 65 and an on-off valve 66 are provided at an intermediate position of the return pipe 64. The condenser 65 includes a return line 64.
Condenses the water vapor in the exhaust gas passing through and removes it from the exhaust gas. The on-off valve 66 opens / closes the return line 64 and controls the flow of exhaust gas passing through the return line 64. The on-off valve 66 is opened only when nitrogen gas, which is an inert gas, is blown into the inlet hood 24, and is closed at other times. When nitrogen gas, which is an inert gas, is blown into the inlet hood 24, the exhaust gas flows into the return line 64,
After passing through the on-off valve 66 and the condenser 65, the inlet hood 24
Will be returned within. As a result, dry exhaust gas having a lower oxygen concentration than air is returned into the inlet hood 24, so that the consumption of nitrogen gas, which is an inert gas blown into the inlet hood 24, can be reduced.

(Example 1) In a dryer 1 capable of drying pulverized coal having a moisture content of 11% to an outlet moisture content of 5%, when the inlet moisture content rises from 10% to 11%, the heat source fluid Without changing the steam pressure and the rotation speed of the drum 3, the oxygen concentration of the exhaust gas is reduced from 10% to 1%.
The exhaust gas flow rate was adjusted to 3%. As a result, the outlet water content could be kept constant at 5%.

(Example 2) In the dryer 1 capable of drying pulverized coal having a moisture content of 12% to an outlet moisture content of 6%, the inlet moisture content was reduced from 12% to 8%. Was reduced to the lowest value, and the rotation speed of the drum 3 was increased to the highest value. However, since the outlet water content was reduced to 4%, the flow rate of the exhaust gas was adjusted so that the oxygen concentration of the exhaust gas from 13% to 10%. As a result, the outlet water content could be restored to 5%.

(Example 3) In the same dryer as in Example 2, since the water content at the inlet was increased from 12% to 15%, the steam pressure was increased to the maximum pressure, and the rotation speed was reduced as much as possible. To secure a residence time. However, since the outlet water content did not decrease sufficiently, the operation was performed with the oxygen concentration of the exhaust gas as high as possible. However, since the outlet moisture content was 7%, air was introduced into the dryer from the inlet gas inlet 25 of the inlet hood 24, and the outlet gas inlet 34 of the outlet hood 33 was sealed.
As a result, the outlet water content was reduced to 5%.

As described above, in the present invention, pulverized coal is supplied to the space inside the heat transfer tube, and steam as the heating fluid is supplied to the space between the outer peripheral surface of the heat transfer tube and the inner peripheral surface of the drum. However, it may be configured to supply steam to the space inside the heat transfer tube and supply pulverized coal to the space between the outer peripheral surface of the heat transfer tube and the inner peripheral surface of the drum. in this case,
Pulverized coal is supplied by a screw conveyor. Further, the configuration of the kiln is not limited to such a configuration, and may be another configuration. Further, the gas conveying means is not limited to the induction fan, and may have another configuration. Also, the inlet and outlet flow control valves need not be provided. The exhaust gas flow rate may be adjusted by controlling the rotation speed of the induction fan 45.

[0056]

As described above, according to the first aspect of the present invention, by detecting the composition of the gas discharged from the kiln, it is possible to know the mixing ratio between the gas supplied from the outside and the water vapor. Therefore, if the flow rate of the gas is adjusted accordingly, the humidity around the granular material can be adjusted, and the drying speed of the granular material can be controlled. Therefore, the outlet moisture content can be kept constant even when the supply flow rate of the granules to be dried and the inlet moisture content vary greatly. In addition, since the composition of the gas discharged from the kiln is detected, even if the pulverized material is pulverized coal, for example, the oxygen concentration can be controlled below the explosion limit concentration, thereby preventing explosion and ignition during drying. can do.

According to the second aspect of the present invention, the first space to which the granular material is supplied is one of the space inside the heat transfer tube and the space outside the heat transfer tube, and the heat source fluid is supplied. Since the second space is a space opposite to the first space with the heat transfer tube interposed therebetween, the granular material can be indirectly heated by the heat source fluid. Therefore, as compared with direct heating such as hot-air drying, the carry-out energy of the exhaust gas can be reduced, and the thermal efficiency can be increased. In addition, since the heat source fluid is water vapor, heat of condensation can be generated and heating can be performed efficiently.

According to the third aspect of the present invention, since the gas conveying means is an induction fan, the amount of dust generated can be reduced.

According to the fourth aspect of the present invention, the flow rate of the gas supplied to one end of the kiln is controlled by the inlet flow control valve, so that the humidity of the gas around the granular material is adjusted and the powder is controlled. The drying speed of the granules can be controlled.

According to the fifth aspect of the present invention, since the flow rate of the gas supplied to the other end of the kiln is controlled by the outlet flow control valve, the humidity of the gas around the granular material is adjusted. The drying speed of the powder can be controlled.

According to the sixth aspect of the present invention, a gas consisting of a gas other than air is supplied to one end or the other end of the kiln, and a part of the gas discharged by the gas discharging means is used for the kiln. Since it is returned to one end, the consumption of gas other than air, for example, nitrogen gas can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a schematic configuration of a granular material dryer 1 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a simplified configuration of a main part of the granular material dryer 1 shown in FIG.

FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a block diagram showing an electrical configuration of the granular material dryer 1 shown in FIG.

FIG. 5 is a graph showing the relationship between the difference in moisture content at the entrance and exit of pulverized coal and the rotation speed of the drum 3.

FIG. 6 is a graph showing the relationship between the difference in water content at the entrance and exit of pulverized coal and the pressure of steam as a heat source fluid.

FIG. 7 is a graph showing a relationship between an oxygen concentration and a coal dust concentration in a boundary region between an explosion region and a non-explosion region of pulverized coal.

FIG. 8 is a graph showing the relationship between the relative humidity of exhaust gas and the difference in moisture content at the entrance and exit of pulverized coal.

FIG. 9 is a graph showing the relationship between the oxygen concentration in the exhaust gas and the relative humidity of the exhaust gas when air is supplied from the outside into the heat transfer tube.

FIG. 10 shows the relationship between the oxygen concentration in the exhaust gas and the relative humidity of the exhaust gas when nitrogen gas, which is an inert gas, is blown into the inlet hood 24 and a mixed gas of nitrogen gas and air is supplied into the heat transfer tube. It is a graph shown.

11 is a flowchart for explaining the operation of the processing circuit 53 shown in FIG. 4 when supplying air from outside to the heat transfer tube.

12 is a simplified diagram showing an example of the configuration of the exhaust gas throttle valve 44 shown in FIG.

FIG. 13 is a system diagram showing a schematic configuration of a granular material dryer 63 according to another embodiment of the present invention.

[Explanation of symbols]

 1,63 Granule dryer 2 Kiln 3 Drum 7 Heat transfer tube 12 Motor 23 Input chute 24 Inlet hood 25 Inlet gas inlet 26 Inlet flow control valve 29 Inlet moisture meter 33 Outlet hood 34 Outlet gas inlet 35 Outlet flow control valve 37 Outlet moisture meter 39 Exhaust gas line 41 Gas component concentration detecting means 42 Thermometer 44 Exhaust gas throttle valve 45 Induction fan 64 Return line 65 Condenser 66 Open / close valve

Claims (6)

[Claims] 1. A kiln having a first heat transfer member.
And a kiln body partitioned into a second space. The kiln body is driven to rotate around its axis, and the powdery material to be dried supplied to the first space from one end in the axial direction is supplied to the second space.
A kiln that is indirectly heat-exchanged by the heat source fluid supplied to the space and is discharged from the other end in the axial direction; and a gas supplied from one of the one end or the other end of the kiln and the indirect heat exchange. Gas transfer means for discharging gas generated from the granular material, a heat source fluid source for supplying a heat source fluid to the second space, and a gas component concentration for detecting the concentration of a constituent component of the gas discharged from the kiln by the gas transfer means A dryer for a granular material, comprising: a detection unit; and a control unit that responds to an output of the gas component concentration detection unit and controls a flow rate of a gas discharged from a kiln by a gas conveyance unit. 2. The kiln has a cylindrical kiln body, the axis of which is inclined such that the one end is higher than the other end, and the heat transfer member is an axis of the kiln body. The first space is either one of a space between an inner peripheral surface of the kiln body and an outer peripheral surface of the heat transfer tube or a space in the heat transfer tube, and the second space is a second space. Is either the space between the inner peripheral surface of the kiln body and the outer peripheral surface of the heat transfer tube or the space inside the heat transfer tube, and the heat source fluid source is a steam source that supplies steam whose pressure can be adjusted. The dryer for a granular material according to claim 1, wherein: 3. The dryer for a granular material according to claim 1, wherein the gas conveying means is an attraction fan for inducing gas. 4. The dryer for a granular material according to claim 1, further comprising an inlet flow rate control valve for controlling a flow rate of a gas supplied to one end of the kiln. 5. The dryer for a granular material according to claim 1, further comprising an outlet flow rate control valve for controlling a flow rate of the gas supplied to the other end of the kiln. 6. A gas supplied to one end or the other end of the kiln is a gas other than air, and a return pipe is provided for returning a part of the gas discharged by the gas discharging means to one end of the kiln. The dryer for a granular material according to any one of claims 1 to 5, characterized in that: