JP2568123B2 - Controller for controlling the flow of fluid-transferred solid particles, pulverized coal flow controller for controlling the flow of coal in a feed pipe, and method for supplying a controlled flow of fluid-transferred solid particles - Google Patents

Description

FIELD OF THE INVENTION The present invention relates generally to pulverized coal flow control systems,
More particularly, it relates to a new and useful flow control system for accurately controlling the mass flow rate of airborne pulverized coal.

[Prior Art] In a pulverized coal combustion boiler, one or more crushers are used to crush a chunk of crushed coal into fine particles of a desired size distribution. Pneumatic pulverized coal (PC) is usually transferred to each burner by pipes ranging in diameter from about 20.32 cm to 60.96 cm (8 to 24 inches).
The number of burners supplied by one crusher may be any number from 2 to 13 supplied by the same number of pipes carrying pulverized coal.

In the operation of a multi-burner boiler, it is highly desirable to maintain a good balance between all burners for high thermal efficiency and to maintain tight control of stack exhaust. Pulverized coal flow is the only most important process variable that needs to be controlled in order to get a balanced operation between several burners. Balanced burner operation requires that the mass flow rates of both air and pulverized coal be the same across all pipes to the burner within some operating limits. Since each supply pipe or feed pipe installed between the crusher and the burner generally has a different total length of each pipeline,
Also, because of the different type and number of bends used in each pipeline, it has a slightly different hydraulic resistance than other supply or feed pipelines. These changes in line resistance can cause primary air and coal flow imbalances between the pulverized coal supply pipelines.
This imbalance must be corrected to ensure efficient combustion.

Conventional industry conventions are shown in FIG. 1 at reference numerals 8 and 9.
By adding a fixed resistance orifice or small diameter pipe section to the line that has a resistance lower than the desired value. The balance of the primary air flow of each line is confirmed by measuring the air flow of each line with a Pitot tube when there is no pulverized coal flow. However, only balancing the primary air flow in the above condition does not necessarily ensure a balanced pulverized coal flow in the system due to the asymmetric flow distribution at the outlet of the crusher and the peculiarities of the solid flow of air transport. Can not. Plant workers use fixed resistance orifices and pipes to balance primary air flow by 10% above average
It has been reported that there is a deviation of the pulverized coal flow that exceeds the range.

[Problems to be Solved by the Invention] Although a large number of pulverized coal flow meters have been developed at various stages of industrial development, there is still no commercially available flow control system for a pulverized coal transfer line. The main reason for the absence of such a system is that it is very difficult to design a reliable control element that can meet the very stringent set of operating requirements. That is: 1. For long-term reliable service, this control element must have high corrosion resistance even when exposed to flowing coal particles. Primary air velocity in the feed pipe is approximately 2133.6 cm / sec (approximately 70 ft / sec) at full load
However, under partial load, it is about 3048 cm / sec (about 10
High speed such as 0 ft / sec) and about 1219.2 cm /
It can be as low as a second (about 40 feet / second). These high-velocity pulverized coals are highly abrasive flow media and erode any conventional metallic intruders or control elements in the flow.

2. This control element must not increase the line pressure drop appreciably. The maximum allowed increase in pressure drop varies from plant to plant, but the allowed increase is generally very small.

3. This control element shall not interfere with the normal flow of primary air that pneumatically transports pulverized coal particles when control functions are not required.

4. This control must be sensitive enough to produce small changes, such as 1-2%, in the mass flow of pulverized coal.

5. The control system should be easily modifiable to fit an existing plant with reasonable installation and operating costs.

US Patent Application No. 07 / 197,9 filed May 24, 1988
No. 26, "Pulverized Coal Flow Control System", is US Patent Application No. 07 / 106,830 filed on October 6, 1987 (JP-A-1-180).
This is a partial continuation application of Japanese Patent No. 17). This U.S. patent application Ser. No. 07 / 197,926 discloses a pulverized coal flow control system in which an aspirator is connected to the outer wall of a bend provided in a supply pipe. The aspirator draws a quantity of the mixture from the feed pipe and reinjects it into the grinder. As a result, the flow of the mixture is controlled through the feed pipe.

The above pulverized coal flow rate control system requires a control bypass line for commutation, and thus has a drawback of high installation cost. The present invention enables a device that does not require these expensive bypass lines altogether, is easier to install and operate, and eliminates the possibility of clogging the bypass lines.

[Means for Solving the Problems] The present invention solves the above-mentioned problems by providing a pulverized coal flow rate control device that controls the flow rate of coal in a feed pipe by reducing the primary air flow rate. is there. Multiple jets or nozzles inject a fluid, such as compressed air, into the pipe, impeding normal primary air flow. The reduction of the primary air flow is controlled by the fluid jet pressure. The injected fluid forms a local recirculation zone. The size of this local recirculation zone is proportional to the injection pressure and the degree of flow reduction is proportional to the size of the recirculation zone.

A reduction in primary air flow rate results in a reduction in coal flow because the amount of coal carried in any one of a group of feed lines fed by a common grinder is proportional to the primary air flow rate in that line. Therefore, the pulverized coal flow control device is designed to reduce the primary air in the feed pipe which has been found to transfer more coal than is required to balance the burner.

In one embodiment of the invention, the device comprises at least one supply for containing a mixture of fluid and airborne particles and for supplying a stream of this mixture from the container to the place of use. It includes a container having a pipe, an injection means for injecting a fluid into each feed pipe to control the flow of the mixture, and a control means for controlling the degree of injection. The present invention uses a plurality of jet nozzles spaced from each feed pipe as the jetting means and uses a computer to control the amount of fluid jetted by each jet nozzle into the feed pipe. The apparatus of the present invention may further include a bypass purge line that provides a limited fluid flow through each injection nozzle to prevent clogging of each injection nozzle when not in use.

The invention also includes suspending the solid particles in a container to form a mixture of solid particles and a fluid, discharging the mixture from the container to the point of use through at least one feed pipe, A method of delivering a solid particle to be transferred and a controlled fluid flow comprising injecting into a feed pipe to reduce the flow of said mixture and controlling the amount of fluid being injected into each feed pipe. I will provide a. The method may further include providing a fluid flow through the bypass purge line to prevent clogging of the injection nozzle. The method preferably injects fluid at an angle against the pipe wall at an angle of about 45 ° against the flow of the mixture.

One aspect of the present invention is to provide an apparatus for supplying a controlled flow of pulverized coal to a pulverized coal combustion boiler.

Another aspect of the invention is to provide a device for controlling solid particles that are fluid transferred.

Another aspect of the invention is to provide a method of providing a controlled flow of solid particles that are transported by an object.

Yet another aspect of the present invention is to provide a pulverized coal flow rate control device which is simple in design, has a robust structure, and can be manufactured economically.

The various features of novelty which are characteristic of the invention are pointed out with particularity in the claims. For a better understanding of the present invention and the operational advantages obtained by using the present invention, reference will now be made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is shown.

Embodiments Referring now to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts throughout the drawings, FIG. 1 shows, in particular, from the crusher 4 through a plurality of feed or feed pipes 2 and 3 to the combustion chamber 7 2 shows a prior art device for balancing the mass flow rate of pulverized coal suspended in air supplied to the burners 5 and 6 of FIG. For this purpose, a fixed resistance orifice pipe 8 is provided in the supply pipe 2 and a fixed resistance pipe 9 is provided in the supply pipe 3. The use of these fixed resistors can still leave an imbalance of 10% or more. It has been predicted that increasing boiler efficiency by 1/2% or more can be achieved by balancing burners to reduce the above 10% imbalance in many existing power plants (power plants).

Balancing the burner to the above efficiency requires control of three process variables: primary air flow, secondary air flow, and pulverized coal flow. Of these, controlling the pulverized coal flow rate is the most difficult, but economically most valuable. The reasons for the difficulty are (1) useful for typical aggressive solutions such as variable valve valves used for many single phase fluids for highly aggressive pulverized coal streams. (2) Flow control is achieved by adding minimal resistance to the line so that when not in operation, the existing primary air transfer system remains essentially as is. It must be done.
The present invention allows for more responsive and efficient control of pulverized coal flow rates, which not only provides cost savings, but also allows for tighter control of stack emissions. Can bring a balanced supply system.

Referring now to FIG. 2, the present invention is illustrated in combination with a grinder 10 having a grinding wheel (not shown) therein for grinding the coal being fed. Primary air
12 is supplied to the crusher 10, and the pulverized coal solid particles generated in the crusher (container) 10 are suspended by air. These solid particles are carried out of the crusher 10 through the outlet pipe 14. The outlet pipe 14 has a bend, but the bend is not critical to the invention. The outlet pipe 14 is connected to a feed or feed pipe 16 which eventually leads to the burner of the furnace or boiler. A pulverized coal flow controller, generally designated by the reference numeral 20, is illustrated in each of the feed pipes 16 in place. Each feed pipe 16 may also be provided with a flow meter (not shown) for measuring the flow rate and providing a signal corresponding to this pulverized coal flow rate for communicating with the computer controller 34 shown in FIG. Good.

FIG. 3 is a schematic configuration diagram of the pulverized coal flow rate control device 20.
Referring to FIG. 3, a plurality of air injection nozzles 26 provided in each feed pipe 16 are shown. Of course, the injection nozzle
26 may include a slit into the feed pipe 16.
A fluid source 22, which is preferably compressed air, provides air via duct 24 for ejection through nozzle 26 into feed pipe 16. Air injection pressure is controlled by a pressure regulator 28 with a current / pressure (I / P) converter 32 that is remotely actuated by a computer 34. The I / P converter 32 is not required for manual adjustment with the manual adjuster 36. A pressure gauge 30 is provided in each feed pipe 16 to adjust the injection pressure of each line.

Injection nozzles 26 are spaced outside each feed pipe 16 by about 7.62 cm (3 inches) or about 10.16 cm (4 inches). At least one injection nozzle is located in each feed pipe 16, although preferably a plurality. For example, about 45.72 cm (18 inches) or about 40.
In the case of a 64 cm (16 inch) feed pipe 16, eight air injection nozzles of about 4.76 mm (3/16 inch) diameter are located on the outside of the pipe about 7.62 cm (3 inches) or about 10.1.
Spaced by 6 cm (4 inches). These injection nozzles 26 are formed by forming holes in an existing feed pipe 16 or by attaching the air injection nozzles 26 to a spool piece having a length of about 30.48 cm (about 1 foot), and attaching the spool piece to the feed pipe 16. It can be installed by inserting into.

A small bypass purge line, indicated generally by the reference numeral 38, provides airflow into the injection nozzle 26 and controls valve 28.
Prevents clogging when the is inactive. The size, pressure, and details of bypass purge line 38 depend primarily on the size and number of injection nozzles 26. The bypass purge line 38 is shown in FIG. 3 as having a fixed resistor 40 and a regulator 42, while in FIG.
Is shown as having only one. In general, the larger the system, the smaller the fixed resistance 40 required in the bypass purge line 38 to ensure airflow that prevents clogging. The purge line pressure upstream of the fixed resistance 40 is close to the supply air pressure 22, but to keep the nozzles 26 open when the nozzles 26 are not operating, 1 or 2 psig
It would be sufficient to apply the pressure of.

The pulverized coal flow control device 20 controls the primary air 12 in the feed pipe 16.
It was designed for the purpose of controlling the flow of coal by reducing the flow rate of coal. Multiple air jets or nozzles 26 inject air from the compressed gas source 22 into the feed pipe 16 and impede the normal flow of primary air 12 through the feed pipe 16, as shown in FIG. The reduction of the primary air flow 12 is controlled by the air injection pressure. The air injection pressure creates a recirculation zone 44. As best illustrated in FIG. 4, the size of this local recirculation zone 44 is proportional to the injection pressure and the degree of flow reduction in the feed pipe 16 is proportional to the size of the recirculation zone 44. To do. When increased coal flow is required, the coal feed rate to the crusher 10 is increased. This will distribute more coal to all feed pipes 16 in the system. Thereafter, the coal flow is balanced by actuating the pulverized coal flow controller 20 on each feed pipe 16. Computer 34 has each feed pipe
In addition to controlling 16 air injection pressures, the flow rate is monitored through the feedback of individual flow meters located on these pipes.

As explained previously, a typical configuration for a coal distribution system is multiple feed pipes 16 which can be any number from 2 to 13.
It includes a plurality of burners 18 fed by a single crusher 10 through. The pipe diameter of the feed pipe 16 may range from about 20.32 cm (about 8 inches) to about 60.96 cm (about 24 inches). The velocity of the primary air 12 in the feed pipe 16 is about 2133.6 cm / sec (about 70 ft / sec) at full load, but is high at about 3048 cm / sec (about 100 ft / sec) at partial load. Speed and about 1219.2 cm / sec (about
Can be as low as 40 ft / sec).

As illustrated in FIG. 4, the injection nozzle 26 is a feed pipe.
It is preferred that the angle is against the flow of the mixture of coal particles to be transferred and the primary air stream in 16. The angle of the injection nozzle 26 in the preferred embodiment is about 45 ° measured from the pipe wall in the direction opposite to the flow of the mixture.

FIG. 5 shows a feed pipe provided with a plurality of injection ports 26.
16 shows a cross section of 16. The pressure gauge 30 indicates the injection pressure adjusted by the regulator 28.

Based on the results of laboratory tests performed on the experimental model, the following observations were noted.

(1) In order to reduce the main flow rate between 0% and 15%, it is necessary to inject an air flow up to about 1% of the main flow rate.

(2) About 1.0 SCFM of control air is required to reduce 1% of the main flow rate.

FIG. 6 is a graph showing the operating characteristics of the test system showing the type of control function desired for computer system 34. For example, if a 7% reduction in a particular feed pipe 16 is desired, the computer 34 issues a command to adjust the pressure to 10 psig. Similarly, if a 5% reduction in feed pipe 16 is desired, the compressed air pressure will be adjusted to 6 psig for operation of the pulverized coal flow controller under similar conditions.

Although the present invention was devised primarily to solve the problems associated with controlling airborne coal particles in a boiler plant, the present invention is broadly applicable to any fluid transfer system that transfers solid particles. The fluid may be a gas or a liquid. When using a liquid fluid system, the pump produces the injection pressure to reduce the fluid flow rate. Alternatively, a gas can be used to reduce the fluid flow rate of the liquid carrying the solid particles.

Although specific embodiments of the present invention have been shown and described in detail in order to illustrate the applications and principles of the present invention, it should be understood by those skilled in the art that certain modifications, changes, and Improvements will occur. All such variations, changes and modifications have been deleted herein for the sake of brevity and clarity of understanding, but it is understood to be within the scope of the appended claims. For example, one variation is to reverse the direction of some of the nozzles 26 to change the flow of primary air 12 in the feed pipe 16. Another variation is to reduce the flow of a liquid fluid carrying solid particles with a jet of a liquid or gaseous fluid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a prior art for supplying pulverized coal to a burner using a fixed resistance orifice and a pipe in order to balance the primary air to the floating pulverized coal supplied to the burner of the combustion chamber. FIG. 2 is a schematic configuration diagram showing an example of the apparatus of FIG. 3, FIG. 2 is a schematic configuration diagram illustrating a feed or supply pipe for transferring coal from a crusher to a burner in a boiler, which is equipped with a control device according to the present invention in place, FIG. 4 is a schematic configuration diagram showing an embodiment of a pulverized coal flow rate control device according to the present invention, FIG. 4 is a longitudinal sectional view showing an enlarged part of a feed pipe, and FIG.
The figure is a cross-sectional view of a feed pipe using the present invention, and FIG. 6 is a characteristic diagram showing test results obtained by an experimental model. 10: Crusher 12: Primary air 14: Outlet pipe 16: Feed (supply) pipe 18: Burner 20: Pulverized coal flow controller 22: Fluid source 24: Duct 26: Nozzle 28: Pressure regulator 30: Pressure gauge 32: Current / pressure converter 34: Computer 36: Manual regulator 38: Bypass purge line 40: Fixed resistance 42: Regulator 44: Recirculation zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 63-97042 (JP, U) Japanese Patent Sho 62-6723 (JP, B2) Actual Sho 62-46992 (JP, Y2)

Claims (6)

(57) [Claims] 1. A control device for controlling the flow of fluid-transferred solid particles, comprising: a container for containing a mixture of fluid and suspended particles; and a container connected to the container for flowing the mixture from the container. At least one feed pipe for supplying, a plurality of jet nozzles for jetting a fluid into the at least one feed pipe to control the flow of the mixture, and control means for controlling the jet nozzles, A bypass purge line coupled to opposite ends of the control means to bypass the control means to provide a fluid flow through the injection nozzles to prevent clogging of the injection nozzles. Characteristic control device. 2. The control device according to claim 1, wherein each of the injection nozzles has an angle against the flow of the mixture. 3. A pulverized coal flow rate control device for controlling the flow of coal in a feed pipe, comprising a crusher for containing a mixture of coal particles suspended in a fluid, and said mixture connected to said crusher. A plurality of feed pipes for supplying a plurality of streams to a plurality of burners in a boiler; a plurality of injection nozzles for injecting fluid into at least one of the feed pipes to reduce the flow of the mixture; Control means for controlling the injection nozzle of the feed pipe to adjust the amount of fluid supplied from the injection nozzle; and a control means coupled to both ends of the control means so as to bypass the control means. A pulverized coal flow rate control device comprising: a bypass purge line for providing a fluid flow through a nozzle to prevent clogging of these injection nozzles. 4. A pulverized coal flow control system according to claim 3 wherein each of said injection nozzles has an angle of about 45 ° against the flow of said mixture. 5. A method of providing a controlled flow of fluid-transferred solid particles, the method comprising: suspending solid particles in a container to form a mixture of solid particles and a fluid; and passing the mixture through at least one feed pipe. Discharging from the container, injecting fluid into at least one feed pipe to affect the flow of the mixture, controlling the amount of fluid being ejected into each feed pipe, Providing a fluid flow through a bypass purge line coupled across the means to bypass the means for performing the control step to prevent nozzle clogging. 6. The method of claim 5 wherein the fluid is jetted at an angle against the flow of the mixture.