FI88430C - ADJUSTMENT OF ORGANIZATION - Google Patents

Description

1 38430

METHOD AND APPARATUS FOR CONTROLLING THE COMBUSTION AIRFLOW IN A HEAT GENERATION PLANT

The invention relates to a method for controlling the combustion air flow in a heat generation installation as defined in the preamble of claim 15.

The invention also relates to a device as defined in the preamble of claim 4 for controlling the combustion air flow in a heat production installation.

10 In current smaller heat production plants with a capacity of less than 5 MW, the combustion air flow adjustment required for the combustion event is carried out by adjusting the combustion air flow to match the fuel flow with a one-off setting. In this case, the combustion air flow 15 corresponds to the ambient, fuel and combustion device conditions prevailing at the time of adjustment.

The disadvantage of current heat generation equipment is that the mass flow of combustion air does not remain constant after the above-mentioned adjustment. This is because 20 the ambient conditions and the characteristics of the combustor, such as resistors, change. Variations in ambient temperature and pressure also affect the density of the combustion air and the change in the resistance of the combustor to the volume flow of the fan. Together, these factors often act simultaneously so that the combustion air flow does not correspond to the fuel flow. The combustion air coefficient often becomes lower than the set value, whereby the fouling of the combustion device is strong and reduces the energy economy and operational reliability of the heat production equipment. 30 For example, existing oil and gas burners in the above power range operate in this way.

Heat generating devices are also known in advance, in which the pressure of the boiler furnace is sought to be kept constant at a set fuel flow. This procedure-35 method is best suited for equipment with a separate flue gas fan. However, this method does not-. 2 88430 changes in environmental conditions are taken into account, which is a prerequisite for optimal combustion.

Heat generating installations are also known in which the pressure difference across the bulb is kept constant at a set fuel flow. However, this procedure requires that a separate air damper be provided in the burner in addition to the actual damper. Changes in environmental conditions are not taken into account in this procedure.

It is also known to use flue gas analyzers for the precise control of the combustion air flow in heat production plants. The disadvantage of such an arrangement is that flue gas analyzers are expensive, susceptible to interference and require constant maintenance and monitoring. In particular, in smaller heat plants 15 with a capacity of less than 5 MW, these are not usually used, but apply to larger heat plants.

The object of the invention is to eliminate the above-mentioned drawbacks.

The method according to the invention is characterized by what is stated in claim 1. In the method according to the invention for controlling the combustion air flow in a heat production installation comprising a burner using gaseous and / or liquid fuel, the parameters corresponding to the characteristics and control values of this burner are known. According to the invention, the pressure difference caused by the combustion air flow over the pressure-causing part in the bulb is measured; the combustion air flow temperature is measured; and by means of the measured quantities and known parameters, adjusting said pressure difference over the pressure-causing part in the burner so as to correspond to the desired combustion air coefficient for said fuel power.

In one embodiment of the method, the prevailing atmospheric pressure is measured; the pressure difference between the measuring point of the difference in pressure caused by said combustion air flow and the environment is measured; these measured values are taken into account when adjusting the desired combustion air factor 3 88430.

In one application of the method, the fuel flow is measured and the effect of its changes on the control of the combustion air flow is taken into account.

The device according to the invention is characterized by what is stated in claim 4.

The device according to the invention for controlling the combustion air flow in a heat generating apparatus comprising a burner using gaseous and / or liquid fuel, the characteristics and control values of which are known, comprises: a differential pressure generating part fitted to the burner; a measuring sensor for measuring the pressure difference over the part causing the pressure difference; a temperature sensor for measuring the temperature of the combustion air flow; an adjusting member such as a damper and a regulator for adjusting the airflow of the bulb; and a data processing unit to which the sensors and the actuator are connected, the data processing unit determining the desired pressure difference over the differential pressure generating part so that the combustion air flow corresponds to the desired combustion air factor for that fuel power, using the measuring variables and bulb characteristics and control values.

In one embodiment of the device, the flame plate of the bulb or a similar member in the burner acts as a part causing the pressure difference.

In one embodiment of the device, it further comprises: a pressure sensor for measuring the prevailing air pressure; and a measuring sensor for measuring the pressure difference between said pressure difference measuring point and the environment, the measurement results being taken into account when adjusting the combustion air flow.

In one embodiment of the device, it includes a fuel flow sensor that can be used to adjust the combustion air flow to match the fuel flow.

The advantage of the invention is that it makes it possible to decisively improve the heat production equipment and the various. especially the combustion of small heat generating equipment • · ·

4 S 8 4 5 O

the amount of flow is such that it is optimal with respect to the amount of fuel flow.

A further advantage of the invention is that the amount of combustion air flow and fuel flow can be kept in an optimal ratio regardless of the variations in the ambient conditions.

A further advantage of the invention is that the burner of the heat production equipment or a part thereof itself forms part of the measuring device required for measuring the combustion air flow, whereby only the actual sensors are installed at the measuring point.

It is also an advantage of the invention that a change in the flow opening of the part causing the differential pressure of the burner, such as the burner flame plate, when the burner is readjusted or 15 parts are replaced only causes new parameters to be set which can be easily fed to the data processing unit.

A further advantage of the invention is that the heat production plant can be reached with relatively small equipment investments, because the device according to the invention does not require a furnace pressure maintenance system or a flue gas extractor.

A further advantage of the invention is that the size or quality level of the heat production equipment does not impose any restrictions on the use of the method and device according to the invention.

A further advantage of the invention is that the burner of the heat production equipment can be adjusted to a certain power or power range already at the factory or in the burner maintenance, regardless of the future place of use.

It is also an advantage of the invention that it achieves a more soot-free combustion result, since the combustion air factor remains constant at the set fuel flow.

The invention will now be described in detail with reference to the accompanying drawings, in which Figure 1 shows a schematic cross-sectional view of a burner in which suitable measuring sensors are mounted on the burner; and Figure 2 shows a data processing unit with peripherals to which the bulb sensors are connected to the data processing unit.

The burner 1 is connected to the boiler 2 in Fig. 1 so that the burner burner 3 is suitably connected to the furnace 5 4. The burner 1 comprises a fan 5, an air duct 6, which leads from the fan through the fire head 3 to the furnace 4. The outlet end 6a of the air duct 6 has a flame plate 7 and a fuel nozzle 8 in the vicinity thereof. A fuel pipe 9 is connected to the fuel nozzle 8.

The following sensors are arranged in connection with the bulb 1: a measuring sensor 10 for measuring the pressure difference over the flame plate 7; a temperature sensor 11 arranged in the air duct 6 relative to the flame plate 7 in the incoming direction of the combustion air flow; and measuring the difference in pressure between the second pressure sensor 12 ilmaka-15 terminal 6 of the inner flame of the plate 7 in the vicinity of ambient pressure (air supply pressure) and at ambient pressure. In addition, the device includes a pressure sensor 13 for measuring the prevailing air pressure. The pressure sensor 13 may be located at a distance from the bulb 1 or in connection with the bulb 1 in a place where the air pressure can be reliably measured without disturbing the fan, such as in connection with the jacket 1a of the bulb 1 at a distance from the burner head 3.

Alternatively, the differential pressure sensors 10 and 12 and the ambient pressure sensor 13 can be connected so that the differential pressure sensor is replaced by separate pressure sensors 10a, 10b (shown in broken lines in Figure 1) and the actual differential pressure sensor 12 is completely omitted. 30 It is thus possible to measure the pressures outside the flame plate with the pressure sensor 10a, inside the flame plate in the air duct 6 with the pressure sensor 10b and the external pressure, i.e. the ambient pressure with the pressure sensor 13.

The fan 5 includes a motor 5a and blades 5b 35 and a combustion air volume control member such as a damper 5c and a damper regulator 5d to provide a combustion air flow 6b to the air duct 6. In connection with the fuel pipe 9 • * 6 88430 has a sensor 14 for measuring the fuel mass flow. The fuel jet directed from the fuel nozzle 8 to the furnace 4 is denoted by the reference number 15. In addition, the ambient pressure is denoted by p «fc, the air duct 5 6 by pressure p * and the flame plate 7 by the furnace pressure 4, i.e. the furnace pressure pa.

Figure 2 shows in block diagram form a control unit 16. The control unit 16 comprises a data processing unit 17, a keyboard 18 or a similar data-10 input device and a printing unit 19 such as a monitor or a printer. The differential pressure sensor 10, the temperature sensor 11, the second differential pressure sensor 12 and the pressure sensor 13 are connected to the data processing unit via a suitable connection unit 20. Alternatively, the pressure sensors 10a, 15 10b replace the differential pressure sensor 10 and the differential pressure sensor 12 is omitted. This interface unit 20 includes, for example, a suitable multiplexer and an A / D converter.

The control unit 16 further comprises an output connection 21 for connecting the control unit to external devices 20, e.g. via a data transmission network. The data processing unit 17 is further connected via a suitable connection unit 22 to an actuator, such as the controller 5d of the combustion air flow damper 5c, for controlling the air flow of the fan 5. The fuel flow sensor 14 is further connected to the data processing unit 17 via a connection unit 20.

With the method according to the invention and a corresponding device, the combustion air flow of the heat production equipment can be selected and adjusted as appropriate to always correspond to the desired combustion air coefficient with the prevailing fuel mass flow. This is based on the following facts.

The amount of combustion air corresponding to the fuel flow used is adjusted so that the desired combustion air factor is achieved. After adjustment, the oxygen content Oa of the flue gases is measured with the burner operating at a known fuel flow and at the same time the combustion air temperature, the 7 88430 pressure difference across the combustion air flow point and the absolute combustion air pressure at the measuring point are measured. The regulated oxygen content Oa corresponds to a certain amount of combustion air qm. The amount of air-5a is calculated, as is known per se, in a pipe provided with a throttling flange, the mass flow of air flowing by the formula (1) as follows; (1) qm «-g.'g» tt «d», ... -if23 · dp '15 where qm is the mass flow of combustion air dp pressure difference across the flange a flow factor e coefficient of expansion Ϋ air density on the inlet side of the flange 20 d diameter of the measuring flange opening

Equation (1) above can be practically represented in the form 25 (2) qm = k r] [dp ^ §1 because the gas J) = f (T, p)? T = gas temperature p «= absolute pressure 30 at the measuring point and at a known fuel flow under changed ambient conditions it is desired to keep qm constant, so by solving the new values of dp ^ the combustion air coefficient can be stabilized. In calculating the value of S, 35 known gas density calculation formulas are generally used.

In the devices according to Figures 1 and 2, by means of the keyboard 18 of the control unit 16, the burner-specific data of the heat production equipment are entered into the data processing! for unit 17. Such burner-specific data, ie 40 parameters, are burner values measured during burner installation and / or maintenance (such as flue gas 02 (%), combustion air temperature (* C), pressure differences Pa (mbar), 8 88430 barometric pressure (mbar) ) and the corresponding fuel powers and other constant burner-specific data. It should also be noted that the number of these burner-specific data need not be limited and the data provided 5 may cover the entire control range of the bulb.

After entering the supply data, the heat generating system is ready for operation. During operation, under the control of the control unit 16, the factors affecting the operation of the bulb 1 are sensed by means of the measuring sensors 10, 11, 10 12, 13 and 14. Thus, the temperature Ti of the combustion air coming through the air duct 6 is known on the basis of the measurement data coming from the sensor 11. The pressure difference apxa = px - pa between the air duct 6 and the furnace 4 is known by means of a message from the differential pressure sensor 10. The pressure difference between the pressure in the air duct 6 and the ambient pressure apx3 - px - p. «. is known from a message received from the second differential pressure sensor 12. Alternatively, the measured pressures px, Pa and p * «can be used to calculate said pressure differences. The amount of fuel flowing through the nozzle 8 20 per unit time is known from the message received from the fuel flow sensor 14.

Based on the operating instructions stored in the memory of the control unit 16, such as formula (1} or formula (2), and the values 25, the control unit controls the combustion air flow 6b in the air duct 6 so that the pressure difference dp «Ap xa corresponds to the fuel mass flow through the nozzle 8. This is achieved by adjusting the fan 30 and in particular the combustion air flow damper 5c so that the combustion air flow 6b flowing through the air duct 6 (i.e. qm in formula 1 or 2) produces the desired pressure difference apxa over the flame plate 7.

In some heat generation installations, it is expedient to apply a simpler method and device for controlling the combustion air flow than described above. In such a simple application, the changes in the ambient pressure p «« can be disregarded. In this case, the pressure difference measurement between the air duct 6 and the environment, i.e. the pressure difference Ap13, is also not performed. Thus, the second differential pressure sensor 5 12 and the pressure sensor 13 are missing from such a device.

In this device application, only the temperature Ta of the combustion air flow 6b coming through the air duct 6 is taken into account. changes and changes in the pressure apxa over the flame plate 7, on the basis of which the combustion air flow 6b is adjusted in principle in the same way as described above. Such an arrangement is often sufficient to prevent excessive variation of the combustion air factor. In this application, the value of the ambient pressure p * «and the value of the pressure difference & pia are set to constants corresponding to the fuel power of the 15 bulbs 1 in use at any given time.

Also, heat generating equipment operating at constant power does not require a fuel flow sensor 14.

According to the embodiment of the invention 20 described above in connection with the drawings, the pressure difference Apia was measured over the flame plate 7. It should be noted, however, that the differential pressure Apia can be measured in another way by means of a differential pressure sensor 10 located. It can be suitably placed in the air duct 6 25 of the bulb 1 or in general in the part connected to the air duct 6. It can also be placed before the blower 5.

The keyboard 18 and the printing unit 19 associated with the device control unit 16 may be located in the same housing as the data processing unit 17, or they may be located in some other suitable location, such as a central control room.

In the above-mentioned embodiment of the invention, one burner 1 was controlled by means of a control unit 16. However, it should be noted that several burners 1 belonging to the same heat generation equipment can be controlled by the same control unit 16 35.

In the operation of the device according to the invention, it should be noted that the device controlling the combustion air flow 6b also allows the burner 1 to operate when the pressure difference across the combustion air flow Apxa flame plate 7 or a corresponding differential pressure component does not correspond to the fuel flow through the nozzle 8, but there is a power shortage in the heat production plant. In this case, the control device 16 can give an alarm, which is detected, for example, in the control room of the heat production equipment.

The invention is not limited solely to the application examples presented above, but many modifications are possible while remaining within the scope of the inventive idea defined by the claims.

Claims (7)

1. A method for adjusting the combustion air stream (6b) in a heat production unit, which comprises a gaseous and / or liquid fuel using burner (1), whose properties and parameters corresponding to the adjustment values are known, are not disclosed. thereof - the pressure difference (Δρ12) caused by the combustion air stream (6b) is measured over a pressure difference existing in the burner; - the temperature (Τχ) of the combustion air stream (6b) is measured; and - with the aid of the measured quantities and known parameters, the said pressure difference is adjusted over the pressure difference contained in the burner, so that the fuel power in question corresponds to the desired combustion air constant. A method according to claim 1, characterized in that - the rescue air pressure (pat) is measured; - the pressure difference (Δρ13) between the pressure difference (Δρ12) of the said combustion air stream (6b) is measured and the environment; and the said quantities are taken into account when the desired combustion air constant is adjusted. A method according to claim 1 or 2, characterized in that the fuel flow is measured and the effect of its changes on the combustion air stream adjustment is taken into account. 4. An apparatus for adjusting the combustion air stream (6b) in a heat generating unit belonging to a gaseous and / or liquid fuel using burner (1), whose characteristics and parameters corresponding to the adjustment values are known, characterized in that, that the device belongs to - a pressure difference causing part which is adapted to the burner (1); - a measurement detector (10) for measuring the pressure difference (Δ12) over the pressure difference producing part; a temperature detector (11) for measuring the temperature of the combustion air stream (6b) (T 2) - an adjusting means, such as a damper (5c), and a regulator (5d) for adjusting the burner air flow (6b); control unit (16), to which the detectors and controller (5d) are connected, and by means of which control unit by utilizing the measured quantities and the characteristics and adjusting values of the desired pressure difference over the pressure difference producing part is determined so that the combustion air The current corresponds to the desired combustion air constant for the fuel effect in question. 5. Apparatus according to claim 4, characterized in that, as a pressure separating part, the burner flame disk (7) or corresponding means in the burner functions. Apparatus according to Claim 4 or 5, characterized in that the device includes - a pressure detector (13) for measuring the rescuing air pressure (Pat); and - a measurement detector (12) for measuring said pressure difference between the measuring point and the ambient pressure (Δρ13 = p - pat), which measurement results are taken into account when adjusting the combustion air flow. Device according to any one of the preceding claims 4, 5 and 6, characterized in that the device belongs to a fuel flow identifier (14), by means of which the combustion air stream can be adjusted to correspond to the fuel flow.