JPS59215514A - Drying and transporting facility for particulate fuel for boiler - Google Patents

Abstract

PURPOSE:To save a fuel consumption in a hot furnace and to prevent an explosion of coal dust in the system in advance by a method wherein a held calory of the burnt and discharged gas of the boiler and the characteristic of inert are effectively utilized. CONSTITUTION:A temperature control system is employed and performed in a drying processing device 2 and the lines L4 and L5 of hot gas induced by the blower 3 are connected, a collection and separator 7 is arranged at the upstream side of the blower 3 in the line L5, a flow rate control part composed of a flow rate sensor 60, flow rate indicating and adjusting meter 61 and an adjusting valve 62 is arranged in the line L7 between the collection and separator 7, a flow rate of gas passing in the drying processing device 2 is adjusted to make a stable classification function in the drying and processing device 2 and at the same time the transporting speed of the particulate is kept to accumulate the particulate fuel in the line L5. In the midway of the line L4 are arranged a temperature stabilization device 15, temperature decreasing device 16 and temperature increasing device 17 in an order of flow of discharged gas of boiler. Therefore, it is possible to save the fuel consumption in the temperature increasing furnace 6 and to prevent the explosion in the system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to drying and
This article relates to the improvement of transportation equipment, and in particular to equipment that is superior in terms of both fuel economy and operational safety.

Up until now, petroleum-based fuels such as heavy oil have been the mainstream fuel for boiler operation, but due to the sharp rise in the price of heavy oil after the oil crisis and the accompanying rise in the price of high-calorie gas, large-scale boilers at various thermal power plants have been , and other small and medium-sized boilers in general industry, alternatives to heavy oil, etc. are being explored, and the use of granular fuels (e.g. pulverized coal, coke powder, etc.) as fuel is becoming more economical and operationally flexible. It is considered to be very effective from these points of view, and is being actively adopted in various fields.

In order to supply such granular fuel to the fuel supply port of a boiler, conventionally, it is dried and then transported as a gas, passed through a granular fuel collection and separation device to be separated from the gas, and then It is temporarily stored in the boiler fuel supply port (
(hereinafter also referred to as coal feed port). That is, if its form is explained based on the diagrammatic system diagram of the drying and transportation equipment shown in FIG. 3
%). Furthermore, lines L4+L5 of high-temperature gas induced by the blower 3 under temperature control are connected to the drying processing apparatus 2, and a temperature raising furnace 6 is further disposed in the line L4, while the inlet of the blower 3 in the line L A granular fuel collection/separation processing device 7 is disposed on the side.

The heating furnace 6 is filled with fuel A such as light oil and city gas! : Combustion air B is sent through lines L, L2, respectively, and mixed and combusted to generate high temperature (iooo~1300'C) combustion exhaust gas. C is supplied as air through the line L3 to the heating furnace 6, mixed with the combustion exhaust gas, and then supplied to the drying device 2. The mixed gas sent to the drying processing device 2 is transported to the collection/separation processing device 7 while drying the raw material to a target moisture content (for example, 3 parts) while passing through the device 2. The granular fuel separated and collected by the device 7 is supplied to and stored in the coal bin 11, while being discharged to the outside of the mixing system 7'/subB blower 3.

The granular fuel thus supplied and stored in the coal bin 11 enters the transportation air line L via the distribution device 12, for example, and is fed to the coal feed port 14 of the boiler 13.

However, as mentioned above, a large amount of combustion exhaust gas obtained by burning fuel such as light oil in the heating furnace 6 is used as the high-temperature gas used for drying and transporting the powdered fuel in such equipment. The drawback is that the consumption is excessive and running costs are extremely high. Moreover, since the temperature of the combustion exhaust gas reaches a high temperature of over 1000℃, it is necessary to dilute and cool it with air before use, and the concentration of 02 in the mixed gas increases, raising the risk of a coal explosion. accompanied by. There, they had to deal with coal dust explosions like
It is necessary to incorporate into the above equipment a device that can detect the initial state of a coal dust explosion, such as a sudden rise in pressure or a rise in CO concentration, and inject extinguishing agent into the system in response to this. The equipment configuration becomes complicated, which increases equipment costs and maintenance costs. However, since the above-mentioned device is not capable of preventing coal dust explosions, it has the drawback of lacking reliability in ensuring operational safety.

Therefore, in the conventional equipment as described above, improvement measures are required from three viewpoints: (1) saving fuel consumption, (2) simplifying equipment and maintenance, and (2) ensuring safety against coal dust explosions.

The inventors of the present invention have also conducted various studies in order to develop a technology that can fully satisfy these requirements. We obtained the knowledge that all of the above requirements could be satisfied by adopting a simple control means, and we were able to confirm this result through further research.

In other words, the boiler exhaust gas that the present inventors intend to use has a relatively high temperature (approximately 120 to 360 degrees Celsius), but conventionally it has only been used to preheat combustion air and fuel, and it has not been fully utilized. It is hard to say that it is being utilized. In addition, the current situation is that the boiler exhaust gas after use still has sensible heat of 100° C. or more, but is dissipated into the atmosphere as it is. Therefore, the present inventors focused on the characteristic (Incrt property) that the boiler exhaust gas is relatively high temperature and the oxygen concentration in the exhaust gas is relatively low (approximately 3 inches or less). Emphasis is placed on the fact that is always stably obtained as the boiler operates, and the boiler exhaust gas is used as a drying and transport medium for granular fuel, and a device that can appropriately control the temperature of this is adopted. They planned this and completed the present invention.

However, in the equipment of the present invention, the high-temperature gas line on the high-temperature gas inlet side of the drying treatment apparatus is formed with a boiler combustion exhaust gas introduction line, and the high-temperature gas line on the high-temperature gas inlet side of the drying treatment apparatus is formed with a boiler combustion exhaust gas introduction line, and a line is formed on the downstream side of the drying treatment apparatus. A temperature raising device is arranged nearby, and a temperature stabilizing device and a temperature lowering device are arranged in any order in the line upstream of the temperature raising device, or only a temperature lowering device is arranged. The main point is that when operating the equipment, the temperature of the gas at the outlet of the drying process is kept constant, that is, the boiler that is fed to the drying process is designed to ensure that the moisture in the raw material is dried. The feeding temperature of the combustion exhaust gas can be controlled by three devices: a temperature increase device, a temperature stabilization device, and a temperature decrease device, or by two devices, a temperature increase device and a temperature decrease device (whichever is located on the upstream side in the line is fine). ) is appropriately controlled by any combination of the following.

As described above, since the present invention effectively utilizes the retained heat capacity and inertness of boiler combustion exhaust gas (hereinafter simply referred to as boiler exhaust gas), it is possible to save fuel consumption in the heating furnace.
Moreover, coal dust explosion within the system can be prevented.

The trrt configuration and effects of the present invention will be explained below based on the drawings of the embodiments. However, the following embodiments are merely representative examples and are not intended to limit the present invention. Any appropriate design changes along these lines are within the technical scope of the present invention.

FIG. 2 is a diagrammatic system diagram illustrating the drying and transportation equipment for boiler granular fuel according to the present invention. This is a drying device for drying to a moisture content (for example, about 3%). Further, the drying processing device 2 is connected to lines L, , L of high-temperature gas induced by a blower 3 while adopting and implementing a temperature control method (split control method) as described below, and a line L4 is connected to the boiler exhaust gas. Line L is used as a flow path for transporting granular fuel. Also, the line L.

A collection/separator tlJA7 is disposed upstream of the blower 3, and a flow rate detection end 60. Flow rate: A flow rate control unit consisting of an indicating controller 61 and a control valve 62 is provided.

The flow rate control unit performs the classification function in the drying device 2 by regulating the flow rate of high temperature gas passing through the drying device 2 (that is, the flow rate at the outlet of the drying device 2) by the blower 3. This serves to ensure stable transportation and to ensure that the transportation speed of the granular fuel is above a certain level, thereby preventing the granular fuel from accumulating in the line L5. The structure after the cole bin 11 connected to the collector/separator 7 is the same as that shown in FIG.

Furthermore, a temperature stabilizing device 15, a temperature decreasing device 16, and a temperature increasing device 17 are arranged in the flow direction of the boiler exhaust gas in the middle of the line L4.

The temperature stabilizing device 15 is installed for the purpose of smoothing out the change characteristics of the boiler exhaust gas temperature to maintain a substantially constant temperature. In other words, the temperature of the boiler exhaust gas varies from approximately 120 to 360 degrees Celsius due to fluctuations in the amount of coal supplied to the boiler.
The temperature changes non-periodically within a temperature range of . Therefore, the temperature of the boiler exhaust gas is kept approximately constant by the temperature stabilizing device 15 before being fed to the drying device 2. To explain a specific configuration example, as shown in the figure, a heat exchanger 18 is provided in the line L, boiler combustion air is introduced into the heat exchanger 18, and a portion of the heat is recovered by heat exchange with the boiler exhaust gas. Meanwhile, the heat exchanger 18
The front and back of the heat exchanger 18 are connected by a high-speed line L+3, and the boiler exhaust gas temperature at the outlet of the heat exchanger 18 is controlled to 11? Assumed to be fixed. 2° is an on-off valve, 21 is a temperature detection end, and 22 is a temperature indicating controller.

Further, the temperature lowering device 16 is a discharge line L from the blower 3.

and line L4 are connected by bypass line L0,
A line L downstream from the connection point. A control valve 25a is provided in the bypass line L, and an on-off valve 25b is provided in the bypass line L. By operating these valves 25a and 125b, a portion of the exhaust gas whose temperature has decreased relatively in the discharge line L8 is transferred to the line L. , and mixes with the boiler exhaust gas in line L4 to lower the temperature of the boiler exhaust gas in line L4. The operation of the control valve 25a and the on-off valve 25b is as follows:
This is done according to a command from a control device 37, which will be described later.

Furthermore, the temperature raising device 17 is provided with a temperature raising furnace 6 in the line L4, and the temperature raising furnace 6 is provided with a line Ll 1 for supplying fuel A such as light oil or city gas, and a line Ll 1 for supplying fuel A such as light oil or city gas, and air B for combustion of the fuel A. A supply line I-+ 2 is connected to each line LI I I Ll□, and control valves 30, 31 and passing detection ends 32,33 are connected via flow rate indicating controllers 34,35, respectively. There is. In addition, Torera's stream: Indication controller 3
4.35 is connected to a control device 37 via an air-fuel ratio control circuit 36.

A temperature detection end 38 for measuring the gas temperature in line L is attached to a portion of line L near the drying processing device 2, and furthermore, this detection end 38 is controlled via a temperature indicating controller 39. It is connected to device 37. A so-called split control circuit is incorporated in the control device 37, and in order to keep the detected temperature from the temperature detection terminal 38 almost constant, that is, to ensure that the moisture in the raw material is dried, the drying processing device 2 is operated. Valve 25a and 25b of temperature lowering device 16 depending on the outlet temperature.
It also performs a control function of issuing a command for switching between the temperature decreasing device 16 and the temperature increasing device 17 while simultaneously adjusting the valves 3o and 31 of the temperature increasing device 17, respectively. That is, the temperature of the boiler exhaust gas sent from the line L4 to the drying device 2 needs to be changed depending on the moisture content in the raw material and the amount of raw material supplied to the drying device 2. When the amount of water increases or when the amount of raw material supplied increases, the amount of heat held in the boiler exhaust gas alone is insufficient to dry the moisture. The occurrence of such a state is detected by a temperature drop at the temperature detection end 38, and after the temperature rate to be increased is transmitted from the temperature indicator controller 39 to the control device 37, a command to increase the generation of high temperature combustion exhaust gas is issued. The temperature increasing device 17 is connected to the control device 37 via the air-fuel ratio control circuit 3G.
transmitted to. Specifically, the opening degree of the control valves 30, 31 is adjusted in accordance with the new settings of the fuel amount and air amount. As a result, the boiler exhaust gas is mixed with the 41F gas combusted in the heating furnace 6 to increase the amount of heat before being supplied to the drying processing device 2, so that sufficient drying can be performed. Moreover, since the heating furnace 6 is operated to always achieve complete combustion by controlling the air-fuel ratio, the combustion exhaust gas is an inert gas, and even if it is mixed with the boiler exhaust gas, the inertness of the entire mixed gas will be impaired. Never.

In this way, the temperature raising device 7 is fully functioning, that is, the control valves so and si are wide open, and a large amount of fuel and air enters the temperature raising furnace 6 and is combusted. In this case, when the temperature of the temperature detection end 38 increases due to a decrease in the moisture content in the raw material or the decrease in the amount of raw material supplied, and therefore the temperature ratio to be decreased is transmitted from the temperature indication adjustment frt 39 to the control device 37, high temperature combustion exhaust gas is generated. The decrease command is sent to the temperature increasing device 17 via the air-fuel ratio control circuit 36 from the control device 37.
transmitted to. In that case, contrary to the above, the control valve 30°31
The degree of opening becomes smaller, the amount of high-temperature exhaust gas burned in the heating furnace 6 decreases, and the temperature at the temperature detection end 38 eventually returns to a predetermined temperature (about 80° C.). Furthermore, due to a decrease in the moisture content in the raw material or a decrease in the amount of raw material supplied, the required amount of high-temperature combustion exhaust gas decreased and became below the minimum operable capacity (minimum burner capacity) of the heating furnace 6. In this case, the heating furnace 6° is operated at its minimum burner capacity and the temperature cooling device 1 is
The temperature lowering device is operated by fully opening the on-off valve 25b of No. 6.

That is, the amount of heat held by the mixed gas amount of the minimum high-temperature combustion exhaust gas amount and the boiler exhaust gas amount is too large for drying the granular fuel, leading to waste of thermal energy. Such a change in state is detected by a temperature rise at the temperature sensing terminal 38, and the temperature rate to be decreased is determined by the temperature indicating controller 3.
9 to the control device 37 , the bypass exhaust gas amount increase command is transmitted from the control device 37 to the temperature lowering device 16 . Specifically, the opening degree of the control valve 25a is reduced to allow more of the exhaust gas whose temperature has decreased in the discharge line L8 to bypass the line L, thereby reducing the amount of heat of the boiler exhaust gas in the line L4.

Even in this case, since the bypassed exhaust gas is an inert gas, even if it is mixed with the boiler exhaust gas, the inertness of the entire mixed exhaust gas will not be impaired.

As described above, in the present invention, when drying and transporting raw materials, the retained heat capacity and inertness of the boiler exhaust gas are fully utilized, so the amount of fuel 'Fc in the heating furnace 6 is greatly reduced. Running costs can be reduced, coal dust explosions can be prevented in the drying and transportation system, and there is no need to install complicated and expensive explosion-proof equipment as in the past.

As mentioned above, in order to properly dry the raw material, it is necessary to change the temperature of the high-temperature gas fed from the line L4 to the drying equipment 2 depending on the raw material temperature and the amount of raw material supplied to the drying equipment H2. However, in the Examples, results as shown in Table 1 were obtained. In Table 1, the horizontal shelf indicates the raw material temperature Mc (modified), and the net shelf indicates the raw material supply amount p (dry-k
g/hr) respectively, and the intersection column between Mc and F represents the temperature (°C) on the high temperature gas inlet side of the drying processing apparatus 2. For drying, the gas temperature at the outlet of the drying processing device 2 is 80°C.
The test was carried out outside the thread so that the water content in the granular fuel was 1 liter.

Table 1 shows an example of the results of experiments to confirm the effect of reducing fuel consumption in the heating furnace 6 as described above (drying conditions were the same as in the above experiments). That is, 13,000 (dry-kg, 41
r) and when boiler exhaust gas is used in the equipment of the present invention (i.e., when the equipment of the present invention is operated),
When not used at all (i.e. when operating conventional equipment)
When comparing the COG gas fuel consumption in the heating furnace 6 for each of the above, it was confirmed that when boiler exhaust gas is used, savings of about 50% or more can be achieved compared to when it is not used.

In the above embodiment, the temperature raising furnace 6 shown in the temperature raising device 17 was used as is, but for example, as shown in FIG.
It can also be heated through.

Furthermore, as for the temperature lowering device 16, instead of using the bypass method as in the embodiment, it is also possible to adopt a method in which the boiler exhaust gas is directly or indirectly cooled by a heat exchanger 51 or a fan cooling method as shown in FIG. If the oxygen concentration is within the safe limits, it is also possible to directly introduce atmospheric air into the line for mixed cooling.

Further, in the embodiment, a bypass type is shown as the temperature stabilizing device 15, but for example, as shown in FIG.
A cooling medium or a heating medium is directly flowed into the control valve 53 via the temperature indicating controller 52 so that the temperature of the boiler exhaust gas in the line L4 at the outlet of the heat exchanger 18 is approximately constant.
This may be done by adjusting the opening degree of the cooling medium or the heating medium and controlling the flow rate of the cooling medium or heating medium. Furthermore, as shown in FIG. By directly mixing the heating or cooling medium,
The temperature of the boiler exhaust gas on the downstream side may be adjusted to be approximately constant.

Furthermore, in the above embodiment, the temperature stabilizing device and the temperature lowering device are arranged independently, but when using a temperature stabilizing device that has both a temperature stabilizing function and a cooling function, , no cooling device is required. For example, as shown in FIG. 7, when an air fin type heat exchanger 54 with adjustable ventilation rate is disposed as a temperature stabilizing device 15' in the line L4, the temperature of the bypass system as shown in the embodiment shown in FIG. Since both the stabilizing device 15 and the temperature lowering device 16 of the same type can be removed from the line L4, the process is simplified and it is also possible to reduce equipment costs.

The equipment for drying and transporting raw materials according to the present invention is configured as described above, but the point is that the raw material is dried and transported by effectively utilizing the heat capacity and inertness of the boiler exhaust gas.
The fuel consumption of conventional heating furnaces can be reduced, and coal dust explosions within the system can be completely prevented, greatly improving the fuel economy and operational safety of the equipment. .

[Brief explanation of drawings]

Fig. 1 is a diagrammatic system diagram showing conventional equipment, Fig. 2 is a diagrammatic system diagram illustrating the equipment of the present invention, Fig. 3 is a modification of the heating device according to the invention, and Fig. 4 is the present invention. FIGS. 5 and 6 show a modification of the temperature lowering device according to the invention, and FIG. 7 is a diagrammatic system diagram showing another embodiment of the equipment of the invention. be. 1... Raw material supply device 2... Drying treatment device 3...
・Prower 6...Temperature raising furnace 7...Collection/separator 13...Boiler 15.15'...Temperature stabilizing device 16...Temperature lowering device 17...Temperature increasing device 18.
50.51 Heat exchanger 36 Air-fuel ratio control circuit 37 Control head Applicant: Kobe Steel, Ltd. Figure 3 Figure 5 Figure 4 Figure 6

Claims (1)

[Claims] (]) Introducing the raw material to be powdered fuel for a boiler from the raw material supply device to the drying processing device, and drying the powdered fuel by introducing temperature-controlled high-temperature gas into the drying processing device. while discharging from the drying treatment equipment,
In drying and transport equipment for boiler powder and granular fuel that is transported to a separately provided powder and granular fuel collection and separation processing device, the high temperature gas line on the high temperature gas inlet side of the drying processing device is connected to the boiler combustion exhaust gas. At the same time, a temperature raising device is arranged downstream of the line and near the drying processing device, and a temperature stabilizing device and a temperature lowering device are arranged in the line upstream of the temperature raising device. 1. Equipment for drying and transporting granular fuel for boilers, characterized in that the equipment is arranged in any order, or only the temperature lowering equipment is arranged.