RU204286U1 - DEVICE FOR AUTOMATIC CONTROL AND CONTROL OF SOLID FUEL BOILER - Google Patents

Abstract

The device refers to automated coal-fired boilers operating on any kind of coal, and can be used to control boilers with a screw fuel supply. The device includes a controller, which is a housing with printed circuit boards placed in it, performing the functions of discrete inputs and outputs, an analog-to-digital converter, a processor board, a screen and a keyboard. Discrete inputs are intended for connection to sensors installed on a solid fuel boiler. The power unit is configured to control the drive of the fuel supply screw in the "work - reverse" mode, depending on the value of the shaft rotation frequency of the fuel supply screw electric motor, determined through the shaft rotation speed meter. When the controlled value of the frequency of rotation of the shaft of the electric motor, converted into an electrical signal, exceeds the predetermined threshold level, the device sends a control signal to the drive of the fuel supply screw. The frequency meter of the electric motor shaft can be made in the form of rotary angle sensors - an encoder or in the form of a digital Hall sensor. The solved task of the utility model is to develop a control device with increased reliability, efficiency, durability of uninterrupted operation of the boiler gear motor with a screw feed. 3 C.p. f-ly, 4 dwg.

Description

The utility model relates to the field of heat power engineering and can find practical application in heating small industrial buildings, private houses, including cottage housing. The device refers to automated coal boilers operating on any kind of coal, and can be used to control automatic solid fuel boilers with a screw feed.

The main problem that arises when organizing a continuous supply of solid fuel to the combustion chamber of the furnace is jamming of the screw. If there is a piece of metal or rock in the incoming coal that the auger cannot grind, and this piece gets into the coal supply zone from the bunker (the place where the auger conveyor body mates with the coal supply shaft from the bunker), the auger will jam. In existing designs of screw conveyors, a safety key is placed on the electric drive shaft, which is cut off when it is jammed. This is inconvenient for the consumer, since in order to restore work, it is necessary to stop the screw conveyor and change this part.

Known automated coal boiler containing a bunker for solid fuel, perpendicular to it located a fuel supply device, a burner device, an air supply device, a water-cooled furnace, consisting of a combustion chamber and an afterburner, internally lined with refractory bricks, a heat exchanger, an ash pan, and an automation unit and an electric drive, and the boiler is additionally equipped with two gravity filters installed in series with the heat exchanger in the chimney, while the heat exchanger is located between the filters, and the solid fuel supply device is made in the form of a screw conveyor enclosed in a cylindrical body, the axis of which runs from the bunker through the boiler furnace , the combustion chamber along the axis of the burner so that the inner half-pipe of the burner is a continuation of the screw conveyor body and has a diameter equal to the diameter of the pipe of the screw conveyor body, and refractory pipes are located in the combustion chamber and afterburner Secondary air supply unit (RF patent 2451239, m.cl. F23B 40/00, publ. 20.05.2012). In the known patent, the fuel is supplied by means of an auger, and the problem of jamming is solved by periodically turning the auger on in the opposite direction, i. E. the auger constantly repeats the following operation: forward movement - to supply fuel, backward movement - to wedge the auger, if a jam has occurred. The operating time of the auger in the forward direction is always longer than the operating time in the opposite direction, this is what ensures the supply of fuel in the forward direction from the fuel storage to the combustion zone.

The disadvantage of this device is the possibility of jamming the auger, failure of the gear motor due to the fact that the force developed by the auger is not controlled in any way, the system has no feedback and does not know whether the jam has occurred or not. If a foreign body has jammed the auger immediately after the auger starts moving, the auger will not stop until it completes its cycle time. Foreign matter can break the auger blades and cause seizure, which will require serious system maintenance.

The closest in technical characteristics to the claimed one is a device for automatic monitoring and control of a solid fuel boiler (RF patent 200548, MCL F23N 1/00, publ. 28.10.2020). The device includes a calculator, which is a housing with printed circuit boards placed in it, performing the functions of discrete inputs and outputs, an analog-to-digital converter, a processor board, a screen and a keyboard. Discrete inputs are intended for connection to sensors installed on the boiler. The device is equipped with a power unit designed to control the drive of the fuel supply screw in the "work - reverse" mode. The power unit is made in the form of a power element supplying current to the winding of the forward stroke of the fuel supply auger drive and a power element supplying current to the reverse winding of the fuel supply auger drive, connected in parallel to the relay output of the controller and the sensor of the current consumption meter of the auger drive. Depending on the value of the current consumption of the screw drive, determined through the current meter, the device sends a control signal to the drive of the fuel supply screw in the "reverse" mode when the controlled value of the current consumption of the screw drive exceeds the specified threshold level. The device provides optimal conditions for the operation of the boiler by automatically controlling the supply of fuel and air, ensuring the circulation of the coolant using pumps and maintaining the temperature of the coolant at a given level using preset values of control parameters, taking into account the current monitored parameter values.

The disadvantages of the prototype device are: the need to fine-tune the threshold current, since the stability of the operation depends on it; too low a threshold current will lead to false positives of the reverse, too high - to jam the auger and failure of the electric motor; limited area of application when used with motors of different power, since it is necessary to provide a wide range of current measurement; as well as the complex connection of three-phase electric motors, since switching and current measurement in three phases is required.

The problem to be solved by the claimed utility model is the creation of a device for automatic monitoring and control of a solid fuel boiler, which makes it possible to eliminate the shortcomings of the prototype.

Technical results achieved when using the claimed utility model:

- expansion of the arsenal of technical means intended for automatic control and management of a solid fuel boiler;

- increasing the safe operation of solid fuel boilers in an emergency;

-increasing the degree of protection against breakdowns of the electric motor caused by jamming of the auger;

- increasing manufacturability and reducing labor intensity when performing work on connecting electric motors;

- improving the usability of the device.

The technical result is achieved by the fact that in a device for automatic control and management of a solid fuel boiler, including a controller, which is a housing with printed circuit boards placed in it, performing the functions of discrete inputs and outputs, an analog-to-digital converter, a processor board, a screen and a keyboard; while discrete inputs are designed to connect to sensors installed on a solid fuel boiler and a power unit configured to control the drive of the fuel supply screw in the "work - reverse" mode, in accordance with the claimed device, the power unit is configured to control the drive of the fuel supply screw depending on the rotational speed of the electric motor of the fuel auger, determined through the shaft speed meter, and the possibility of supplying a control signal to the drive of the fuel auger in the "reverse" mode when the controlled value of the rotational speed of the electric motor shaft, converted into an electrical signal, of a predetermined threshold level.

The device is complemented by specifying particular distinctive features that contribute to the achievement of the claimed technical result

The meter of the frequency of rotation of the shaft of the electric motor is made in the form of sensors of the angle of rotation - an encoder.

The shaft speed meter is designed as a digital Hall sensor.

The power unit includes relays that supply current to the forward winding of the fuel supply auger drive and to the reverse winding of the fuel supply auger drive, connected in parallel to the discrete outputs of the controller and to the motor of the auger drive gear motor.

FIG. 1 shows a diagram of the claimed device. The device for automatic control and management of a solid fuel boiler with a screw reversing function includes:

1a - a device that implements the logic of the boiler controller (can be implemented in the form of an integrated microcircuit of a microcontroller, a programmable logic controller (PLC) or an industrial computer);

1 - power element - relay supplying current to the winding of the forward stroke of the electric motor of the fuel supply auger;

2 - power element - relay supplying current to the reverse winding of the electric motor of the fuel supply auger;

3 - measuring the frequency of rotation of the electric motor shaft of the auger fuel supply;

4 - electric motor of the fuel supply auger;

5 - digital bus for communication with modules that extend the functionality of the controller;

6 - bunker cover sensor;

7 - air temperature sensors of the heated room;

8 - coolant temperature sensor in the underfloor heating circuit;

9 - coolant temperature sensor in the general-purpose circuit;

10 - temperature sensor of outgoing flue gases;

11 - outdoor temperature sensor;

12 - auger tube temperature sensor;

13 - hot water supply circuit temperature sensor;

14 - central heating boiler temperature sensor;

15 - screen and system for entering information into the controller;

16 - module for communication with the Internet;

17 - power element that controls a three-four-way valve;

18 - three-four-way valve;

19 - power element that controls the fuel turner in the bunker;

20 - electric motor of the agitator;

21 - power element controlling the boiler ash removal system;

22 - electric motor of the ash removal auger;

23 - central heating circuit pump;

24 - power element that controls the central heating pump;

25 - hot water supply circuit pump;

26 - power element that controls the pump of the hot water supply circuit;

27 - underfloor heating circuit pump;

28 - power element that controls the floor heating circuit;

29 - general purpose circuit pump;

30 - power element that controls the pump of the general-purpose circuit;

31 - sound emitter for informing the user by means of sound information;

32 - blower fan for supplying air to the combustion chamber;

33 - thermostat interrupting the supply of current to the fan when the critical temperature of the thermostat is exceeded;

34 - power element that smoothly controls the fan speed;

35 - end sensor allowing the controller to control boilers with pump fuel supply (type of boilers with pump fuel supply instead of screw);

36 - optical sensor indicating the presence of a flame in the burner;

37 - the lambda sensor, which is involved in the analysis of the oxygen concentration in the flue gases, is needed in order to judge the excess of oxygen in the combustion zone, i.e. the quality of solid fuel combustion;

38 - the auto-ignition channel is used to ignite the fuel without human intervention, in the event of the boiler fading out or when it is first fired up.

The controller 1a is a housing with printed circuit boards placed in it, which perform the functions of discrete inputs and outputs, an analog-to-digital converter, a processor board, a screen and a keyboard (not marked in the figure). Discrete inputs are intended for connection to sensors installed on the boiler, and discrete outputs are for connecting power elements.

The power unit includes relays 1 and 2, which control the electric motor of the fuel auger. If relay 1 closes, the auger rotates in the forward direction, if relay 2 closes, the auger rotates in the opposite direction. The direction of rotation of the auger is taken for the direct supply of fuel, when the fuel in the auger conveyor moves in the direction from the hopper to the burner, for the reverse - when the fuel moves from the burner to the hopper.

Relay 1 and relay 2 can never work at the same time, because this will cause overheating of the windings and very quick failure of the electric motor, even when used without load.

The boiler control device operates in the following way: the fuel supply screw supplies fuel in portions to the combustion area, the blower fan 32 pumps air, thus ensuring the combustion of solid fuel. In the process of combustion, thermal energy is generated, which is spent on heating the coolant. The temperature of the heating medium is set by the user, the current temperature is measured by the sensor 14 of the current temperature of the central heating boiler. The device also provides control of pumps for mixing the coolant. The power element 17 controls the three-four-way valve 18, controls the damper, in the 100% open position at the outlet of the valve, hot water, in the 0% position - completely cold, with a different position of the damper damper, any intermediate temperature can be achieved in this sense of three or four-way valve - mixing coolant from different circuits. The valve 18 is designed as an electronic mixing valve.

In order to ensure safety against fire in the hopper, a screw tube temperature sensor 12 is used, which continuously measures the temperature of the auger tube and prevents the spread of flame from the burner into the hopper.

The device is capable of controlling an indirect heating boiler using a pump and an indirect heating boiler temperature sensor. The hot water supply circuit: pump 25, power element 26 and sensor 13 measuring the current value of the circuit temperature, allow you to prepare water in the indirect heating boiler at the required temperature for household needs.

To connect water heated floors, two circuits are used - circuit No. 1 and No. 2, each circuit consists of a pump 23, 25, which moves the coolant along a closed and isolated from the main circuit of the boiler and a temperature sensor 8, 9 of the coolant of this circuit, which allows the system to measure temperature in each circuit separately from other circuits and maintain the temperature required by the user.

The start of the solid fuel boiler control device is carried out in manual mode by preliminary firing up dry fuel, waiting for an extensive ignition and then turning on the automatic mode of operation with preset fan blowing forces.

In the automatic mode, the system is started using the auto-ignition channel 38, which heats the dry fuel to the ignition temperature, then the combustion process is stabilized, and the device switches to the automatic supply of fuel and air by the blowing fan 32.

After the fuel on the burner has started to generate heat energy steadily, the temperature of the boiler water jacket begins to rise, the circulation pump is turned on, ensuring the circulation of the coolant.

The mode of fuel supply to the furnace by the auger is selected in such a way that the fuel level on the burner is constant and uniform extensive combustion of the entire fuel layer is ensured. To do this, adjust the time of the coefficients of the algorithm for regulating the air supply and the coefficients for regulating the fuel supply. The control device independently decides to change the amount of fuel supply and the blowing power being guided by the flue gas temperature sensor 10, the coolant temperature sensor 13, 14 and the flue gas lambda sensor 37 in order to maintain the set temperature and at the same time consume the minimum amount of fuel.

When the temperature measured by the temperature sensor 12 of the auger pipe in the auger pipe is exceeded, the fire protection system is triggered and the fuel in the pipe is accidentally pushed into the combustion zone, then the fan and the electric motor of the fuel supply auger stop.

To improve the operational properties, prevent accidents, the device provides for the reverse of the fuel supply screw and control of its movement, depending on the frequency of pulses from the frequency meter 3, which measures the rotational speed of the electric motor of the fuel supply screw. Often screw jamming occurs with retort burners, i.e. those in which even more effort is required from the electric motor in order to turn the retort additionally together with the auger. Also, often jamming occurs due to difficult operating conditions, violation of the technology for manufacturing a cast-iron retort, the ingress of foreign objects (stones, nails, etc.) into the fuel.

The frequency meter 3 is a sensor that converts the shaft rotation frequency into an electrical signal, which is a series of alternating rectangular pulses, where "0" is taken for the absence of potential, and "1" for the potential equal to the supply voltage of the sensor. The frequency of electrical pulses depends on the frequency of rotation of the shaft, the higher the frequency of rotation, the higher the frequency of the pulses and vice versa (Fig. 4).

The frequency meter 3 can be made using factory sensors, for example, commercially available rotary angle sensors (encoder), and custom-made (Figs. 2, 3).

In the system, the frequency meter 3 can be installed either on the shaft of the electric motor or on the shaft of the fuel supply auger. Since the shaft of the electric motor is connected to the shaft of the fuel supply auger by means of a gearbox, the installation location does not matter. Regardless of where the frequency meter is installed, the device can unambiguously determine whether the auger is rotating or not.

The device does not require any preliminary adjustment to work with different electric motors, the main criterion for detecting jamming is to reduce the pulse frequency from the frequency meter to 0. If the system detects a drop in frequency to 0, then the shaft does not rotate and it is necessary to stop the direct fuel supply, and then turn on the reverse feed. fuel (reverse) for a few seconds to try to wedge the auger and prevent the electric motor from coming out of a standing position. In addition, the reverse rotation of the auger causes the solid fuel in the auger to change its position, which can get rid of jamming during the next forward feed.

FIG. 2 shows a diagram of an optical frequency meter, where 39 is a disk opaque to IR radiation, 40 is a shaft transmitting rotation to a disk, 41 is an IR emitter, 42 is an IR receiver, 43 is a window in a disk transparent for IR radiation. The emitter 41 and the receiver 42 are fixedly mounted on the same axis. The disk 39 is fixedly mounted on the shaft 40, while the shaft can rotate freely around its axis. The shaft 40 is connected to the shaft of the electric motor, or to the shaft of the fuel supply auger using an adapter coupling.

The optical frequency meter works as follows: the emitter 41 works constantly, the receiver 42 registers the radiation of the emitter, if there is radiation, the receiver gives out a logical "1" equal to the supply voltage of the receiver, if there is no radiation, the receiver gives out a logical "0" equal to the zero potential. Rotation from the electric motor or from the auger is transmitted through the adapter and shaft 40 to the disc 39. Rotating, the disc periodically blocks the luminous flux from the emitter 41 to the receiver 42, thus, the receiver registers the change in the luminous flux. The receiver generates a square wave (meander) signal at the output. The signal frequency is directly proportional to the rotational speed of the shaft 40.

FIG. 3 shows a diagram of a frequency meter based on a digital Hall sensor, where 44 is a disc made of ferromagnetic material, 45 is a shaft transmitting rotation to the disc, 46 is a Hall sensor, 47 is an air gap between the Hall sensor and the disc, 48 is a recess in the disc. ... The Hall sensor 46 is fixedly fixed, while an air gap 47 is provided between the edge of the Hall sensor and the disc. The disc 44 is fixedly mounted on the shaft 45, and the shaft can rotate freely about its axis. Shaft 45 will be connected to the shaft of the electric motor, or to the shaft of the fuel supply auger using an adapter coupling.

The frequency meter based on a digital Hall sensor works as follows: rotation from the electric motor or from the auger is transmitted through the adapter and shaft 45 to the disc 44, the Hall sensor works constantly and when the disc 44 rotates, it registers the alternation of protrusions and depressions. Each change of "ledge-trough" causes the Hall sensor to switch its logical state. Thus, when the disc rotates, the Hall sensor generates a square-wave signal (meander) at the output. The signal frequency is directly proportional to the rotational speed of the shaft 45.

FIG. 4 shows graphs, where 49 is the shaft rotation speed f ₁ (t), 50 is the signal from the shaft rotation frequency meter f ₂ (t). Three areas can be distinguished on the graphs. Section 51 - is characterized by a constant shaft rotation speed and a constant signal frequency; section 52 — decreasing the shaft rotation speed and decreasing the signal frequency; section 53 - locked shaft and zero signal frequency.

Auger jam detection algorithm:

1. We turn on the supply of current through relay 1 (direct stroke) to the electric motor of the fuel auger.

2. We calculate the average value of the shaft rotation frequency based on the results of 3 measurements.

3. Compare the average frequency value with the threshold value X: if the average frequency is greater than X, then the rotation is taking place; if the value is less than or equal to X, then the rotation of the shaft has stopped, the auger jammed has been detected, it is necessary to switch to the reverse mode (point 4).

4. If jamming is detected, then turn off the supply of current through relay 1, turn on the supply of current through relay 2 (reverse) for a few seconds.

5. We repeat steps 1-3.

6. If jamming is detected 3 times in a row, the device stops the fuel supply, puts the boiler into the “stop” mode, turns on the error signaling.

The use of the proposed device will have a positive effect on the operational characteristics and durability of the boiler because the autonomy of the boiler is increased, the mechanical parts do not have to work during overloads, the electric motor does not work in the rotor jamming mode.

Practical implementation.

Devices for control of solid fuel boilers with auger feed have been developed and tested. The table shows the main technical characteristics of the control device.

Table
Main technical characteristics of the controller for solid fuel boilers Supply voltage, V 230 Maximum power consumption of the controller, W 10 Enclosure protection IP40 Temperature measurement range of CH / DHW sensors, ° С 0-100 Central heating temperature setting range, ° С 40-95 DHW temperature setting range, ºС 40-95 Operating temperature range, ° С 0-50 Central heating pump maximum power, W 250 Maximum power of the hot water pump, W 250 Maximum power of the screw, W 700 Maximum fan power, W 250 Fuse insert for power outputs, A 6.3

The problem of the utility model is to develop a control device for an automatic boiler of increased reliability, efficiency, durability, uninterrupted operation of an automatic boiler with a screw feed and an increase in the time of non-stop operation for retort burners that were produced in violation of the casting technology.

Claims (4)

1. A device for automatic control and management of a solid fuel boiler, including a controller, which is a housing with printed circuit boards placed in it, performing the functions of discrete inputs and outputs, an analog-to-digital converter, a processor board, a screen and a keyboard; while the discrete inputs are designed to connect to sensors installed on a solid fuel boiler and a power unit made with the ability to control the drive of the fuel supply screw in the "work - reverse" mode, characterized in that the power unit is configured to control the drive of the fuel supply screw depending on on the frequency rotation of the shaft of the electric motor of the fuel supply auger, determined through the meter of the rotation frequency of the shaft, and the possibility of supplying a control signal to the drive of the screw of supply of fuel in the "reverse" mode when the controlled value of the frequency of rotation of the shaft of the electric motor, converted into an electrical signal, of a predetermined threshold level is exceeded. 2. An automatic control device according to claim 1, characterized in that the shaft rotation speed meter is made in the form of rotation angle sensors - an encoder. 3. The automatic control device according to claim 1, characterized in that the shaft speed meter is made in the form of a digital Hall sensor. 4. The automatic control device according to claim 1, characterized in that the power unit includes relays that supply current to the forward winding of the fuel supply auger drive and to the return winding of the fuel supply auger drive, which are connected in parallel to the discrete outputs of the controller and to the engine. auger drive reducer.

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