JP2009526981A - Apparatus and method for measuring mass flow rate of fine-grained material, especially coal fuel - Google Patents

Abstract

The object of the present invention is an apparatus and method for measuring the mass flow rate of fine-grained material, in particular coal fuel, in a chain conveyor or chain feeder (1). According to the invention, the belt conveyor (6) with weighing means (13) is arranged inside the housing (18) of the chain conveyor or chain feeder so that the mass flow passes through this belt conveyor (6). Arranged.
[Selection] Figure 2d

Description

  The object of the present invention is an apparatus and method for measuring the mass flow rate of fine-grained material, in particular coal fuel, as described in the preamble of the independent claim.

  In coal-fired power plants, it is important to control the mass flow rate of fuel in order to regulate the combustion process and maintain the required power level. Since large volume fluctuations can cause blockage and other mechanical problems, especially in conveyors and boilers, the volume flow of fuel must also be controlled.

  Coal fuel is not homogeneous with respect to its properties. There are various types of charcoal, and the weight per volume can vary greatly. Furthermore, the weight per volume is particularly affected by moisture and particle size. Therefore, a sufficiently accurate adjustment cannot be obtained simply by controlling the volume flow rate.

  In existing facilities, the mass flow rate is most often controlled indirectly by controlling only the volumetric flow rate of fuel at the chain conveyor or chain feeder between the silo and boiler. For example, the control is implemented by adjusting the speed of the feeder conveyor and / or by adjusting the height of the material on the conveyor with a mechanical adjustment / restriction plate. Therefore, this control method is indirect and inaccurate as it is.

  Since the chain conveyor or chain feeder has a closed steel structure, it has not been possible to use a known technique based on weighing for mass flow measurement such as a belt scale. Since the weight of the material being transported is very small compared to the static load of a heavy-duty conveyor, it is not feasible to weigh the entire conveyor.

  One object of the present invention is to alleviate or eliminate some of the above-mentioned problems that have become apparent in the prior art.

  One of the objects of the present invention is to provide a solution that allows accurate mass flow measurement of the fuel flow, in particular in addition to volumetric flow control.

  One of the objects of the present invention is to provide a measurement method suitable not only for mass flow measurement in the required units (kg / second, t / hour, t / a) but also for cumulative measurement of the entire material flow. It is.

  One of the objects of the present invention is to provide a solution that allows accurate mass flow measurement of fuel flow in a gravity based manner.

  To achieve the above object, the invention is particularly presented in the characterizing part of the independent claims.

  Although not necessarily explicitly shown, the example embodiments and advantages referred to herein relate to both the apparatus and method according to the invention as appropriate.

  An exemplary apparatus according to the present invention for measuring the mass flow rate of fine grain material in a chain conveyor or chain feeder comprises a belt conveyor arranged inside the housing of the chain conveyor or chain feeder. The material to be conveyed is arranged to pass through a belt conveyor. According to the invention, the weighing means are arranged on a belt conveyor.

  Since chain conveyors, chain feeders and belt conveyors are known per se, their function or structure will not be described in further detail here.

  The present invention is very suitable for the measurement of coal fuel in power plants and similar facilities. The present invention can be applied to the measurement of any bulk material conveyed on a chain conveyor. The present invention is particularly suitable for any fine grain solid fuel such as wood chips, shredded wood, sawdust, bark, peat.

  Surprisingly, it became clear that the mass flow rate of the material moving through the chain conveyor or chain feeder can be easily measured by installing the belt conveyor inside the chain conveyor housing and providing the belt conveyor with weighing means. It was.

  One of the greatest advantages of the present invention is that the data that can be obtained with real-time mass flow and the possibility of controlling the mass flow with the present invention improves the controllability of the combustion process.

  In one embodiment of the present invention, the belt conveyor is configured with an upper surface and a lower surface of the chain conveyor so that a material flow falling from the upper surface of the chain conveyor or chain feeder to the lower surface falls on the belt conveyor. It is arranged between. This type of structure is simple and easy to implement.

  In one embodiment of the invention, one or several weighing sensors, such as strain gauges or semiconductor weighing sensors, are arranged on the belt conveyor frame. This type of weighing sensor is highly reliable.

  In one embodiment of the invention, the belt conveyor has a front pulley and a rear pulley and no support rollers between them. This is a simple structure. This type of structure is usually only feasible on a relatively short belt conveyor.

  In one embodiment of the invention, the belt conveyor pulley and conveyor belt are disposed within the housing of the chain conveyor or chain feeder, and the pulley shaft and the frame of the belt conveyor are at least partially arranged outside the housing. In one embodiment, the pulley bearing and metering means according to the invention are located outside the housing. The advantage of this type of construction is that sensitive parts of the device such as bearings and metering means are arranged so that they are not exposed to coal dust. Parts placed outside the housing are easy to service.

  In one embodiment of the invention, the belt conveyor frame is pivoted so that its pivot axis is essentially on the same vertical line as the point on the belt conveyor where the material flow falls from the top surface. Connected. This minimizes or completely eliminates the impact of the impact on the measurement according to the invention by the coal falling on the belt conveyor.

  In one embodiment of the invention, the weighing means are arranged near the end of the belt conveyor that is furthest from the pivot axis. At this location, the belt conveyor movement or deflection caused by the mass flow is maximal, so the measurement results are maximally accurate.

  Next, the present invention will be described in more detail with reference to the accompanying drawings.

  The same reference numbers are used for parts that correspond to each other in different drawings. The flow of coal through the device is indicated by arrows in the figure. The layer formed by coal is indicated by dots.

  FIG. 1 shows a feeder conveyor 1 installed under a coal storage silo 14. The feeder conveyor 1 according to the present invention includes a chain conveyor that is controlled from a coal storage silo 14 to a power plant boiler (not shown) to carry coal. The movement of coal from the silo to the conveyor 1 and from the conveyor to the power plant boiler itself is a known technique and will not be described in further detail here.

  2c and 2d show the chain feeder 1. In this chain feeder, the belt conveyor 6 shown alone in FIGS. 2a and 2b is arranged. The chain feeder 1 is surrounded by a steel housing 18. A belt conveyor 6 having a special structure that is particularly suitable for measuring fine-grained materials such as coal fuel is arranged at the tip 15 of the chain feeder 1 so that the entire mass flow passes. Coal entering from the silo 14 or preceding conveyor first falls to the upper surface 3 of the chain conveyor or chain feeder and enters the space 16. From the space 16, the conveyor chain or scraper chain 2 carries coal under the mechanical restriction element 4. The restricting element 4 limits the height of the coal bed and spreads the coal bed evenly on the scraper chain 2. The chain 2 carries the coal past the end 17 of the upper surface 3, from which the coal falls onto the belt conveyor 6 arranged on the lower surface 5. The belt conveyor 6 is disposed at a point where coal falls from the upper surface. The dimensions of the belt conveyor 6 are selected so that essentially all the falling coal remains on the conveyor belt 7. The belt conveyor 6 further passes over the end of the belt conveyor 6 and carries the coal layer to the lower surface 5. On the lower surface 5, the scraper chain 2 carries the coal to the next conveyor or power plant boiler.

  The belt conveyor 6 is attached to the torsion-resistant frame 11 such that the belt conveyor pulleys 8 and 9 and the conveyor belt 7 are arranged inside the feeder conveyor housing 18. The pulley bearing 10 and the metering sensor 13 are arranged outside the housing 18. The frame 11 is pivotally connected to the floor 19 and the rest of the chain feeder so that the pivot shaft 12 is basically on the same vertical line as the point on the belt conveyor 6 where the coal falls. The This eliminates the impact effect of coal falling on the belt 7.

  The front pulley 8 of the belt conveyor is driven by an electric motor 21. The belt conveyor 6 has a front pulley 8 and a rear pulley 9 with no support rollers between them.

  The weighing sensor 13 is for example a strain cage or a semiconductor weighing sensor and is arranged on one side 20. Here, the lever arm is longer than the rotating shaft 12 of the frame 11. Due to this geometry, the mass of the material on the belt 7 is indicated directly at the output of the weighing sensor 13. The speed of the belt 7 is measured in a known manner, for example at the axis of the front pulley 8, and the electronic components (not shown) of the device are used to determine the mass flow rate (eg kg / sec or t) / Hour). A current signal may be output for the quantity in question. In this case, the acquired data can be sent to a point where data is required, such as a control room and process management. Thereby, the amount of coal carried to the boiler can be monitored in real time using a regulator according to the prior art. For example, the amount of coal can be controlled by controlling a drive mechanism (not shown) of the electric motor 21 of the belt conveyor, the mechanical limiter 4 or the scraper chain 2.

  The pulley shafts 8 and 9 of the belt conveyor have a sealing body that passes through the housing wall 18 of the feeder conveyor 1 and has a bearing 10 with a special structure. Since the sealing body does not transmit the force from the housing wall 18, the measurement result is not distorted.

  The figure shows only one preferred embodiment according to the present invention. The figures do not clearly show some aspects that are not important to the main idea of the present invention. These embodiments are known per se or obvious to those skilled in the art. It will be apparent to those skilled in the art that the present invention is not limited to the examples shown above, and that the invention can vary within the scope of the claims. The dependent claims present some possible embodiments of the invention and therefore the dependent claims should not be regarded as limiting the protection scope of the invention.

1 shows a chain feeder according to the present invention installed under a coal silo. It is a front view of the belt conveyor concerning the present invention. It is a side view of the belt conveyor concerning the present invention. It is a front view of the apparatus which concerns on this invention. It is a side view of the apparatus which concerns on this invention.

Claims (11)

A device for measuring the mass flow rate of fine-grained material, especially coal fuel, in a chain conveyor or chain feeder,
A belt conveyor (6) with weighing means (13) is arranged inside the housing of the chain conveyor or chain feeder, and the material to be conveyed is arranged to pass through the belt conveyor (6) A device characterized.   The belt conveyor (6) is connected to the upper surface (3) and the upper surface (3) so that the flow of the material falling from the upper surface to the lower surface of the chain conveyor or chain feeder falls on the belt conveyor (6). Device according to claim 1, characterized in that it is arranged between the lower surface (5).   Device according to claim 1 or 2, characterized in that one or several weighing sensors (13) are arranged in the frame (11) of the belt conveyor.   Device according to any one of claims 1 to 3, characterized in that the belt conveyor has a front pulley (8) and a rear pulley (9) and no support rollers.   A pulley (8, 9) and a conveyor belt (7) of the belt conveyor are arranged inside the housing (18) of the chain conveyor or chain feeder, and the pulley bearing (10) and the weighing means (13) are A shaft according to any one of the preceding claims, characterized in that the shaft of the pulley and the frame (11) of the belt conveyor are arranged at least partly outside the housing (18) so that they are outside the housing (18). The apparatus according to claim 1.   The frame (11) of the belt conveyor is pivotally connected so that the rotation shaft (12) is basically on the same vertical line as the point of the belt conveyor (6) where the material flow falls. The device according to any one of claims 1 to 5, characterized in that   7. A device according to claim 6, characterized in that the weighing means (13) are arranged in the vicinity of the end (20) of the belt conveyor located farthest from the pivot axis (12). A method for measuring the mass flow rate of fine grain material, in particular coal fuel, in a chain conveyor or chain feeder (1),
Method according to claim 1, characterized in that the mass flow rate is measured when the material is on a belt conveyor (6) arranged inside the housing (18) of the chain conveyor or chain feeder.   9. The mass flow rate is measured after the material has dropped from the upper surface of the chain conveyor or chain feeder and before the material reaches the lower surface of the chain conveyor or chain feeder. The method described in 1.   10. Method according to claim 8 or 9, characterized in that the mass flow rate is measured by one or more weighing sensors that measure the movement of the belt conveyor frame (11).   The belt conveyor frame (11) is pivotally connected to a rotation shaft (12), and the weighing means (13) is located at the end of the belt conveyor (furthest from the rotation shaft (12)). The method according to any one of claims 8 to 10, wherein the mass flow rate is measured in the vicinity of 20).

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