DE3245634C2 - Process for regulating the residual oxygen content in the exhaust gases from fan firing systems and equipment for carrying out the process - Google Patents

Abstract

Power-controlled firing systems are operated by a power regulator (9, 10) with a drive (14) and actuators (16, 17) with a fixed fuel / air ratio. An oxygen detector (20) for keeping the residual oxygen content in the exhaust gas duct (19) low influences a drive (26) of an additional flap (27) via a controller (22). The adjustment range of the additional flap (27) is limited by an additional regulator (28, 30) depending on the condition of the combustion air. When the limit positions are reached, alarm (44) is triggered and the air supply is increased again to prevent operation with a lack of air. This allows a basic setting with a small excess of air and a correspondingly increased degree of efficiency.

Description

solves.

The invention is characterized in claims 1 and 3.

The invention relates to a method for re-The following is a Ausführungsbc.spiel the invention

gelation of the residual oxygen content in the exhaust gases from 65 dung explained in more detail with reference to the drawing. It means fan firing systems as well as a facility.

to carry out the method according to the upper Fig. 1 shows a simplified structure c.ner

eriff of claims 1 and 3. furnace and

F i g. 2 a schematic detail

In both figures, connecting lines are provided with triangular arrows. These should be for indicate the direction of the signal flow in the corresponding line for a better understanding.

In FIG. 1 means 1 the combustion chamber of a fan firing system. A flame sensor (not shown) is used to monitor the presence of a ram a burner control 2, which the fuel with a drive 3 of a first fuel valve 4 releases in a fuel line 5 and completely blocks when a flame is extinguished. The valve 4 only has two stable positions, completely open or completely closed.

A burner 6 is provided by a fan, not shown, via a main air duct 7 with the necessary Combustion air supplied. The same fan feeds an additional air duct connected in parallel to the main air duct 7 8, the purpose of which is explained below.

The burner 6 can be a so-called modulating burner. His performance will be continuously regulated according to the current heat demand. In the example described, a temperature sensor is used for this 9, but this could also be a pressure sensor, a position transmitter of a steam valve actuator or be a steam meter. The temperature sensor 9 belongs to a power controller 10 of the combustion system and is via a line 11 to the power regulator 10 connected. On the one hand, the power regulator 10 gives the automatic furnace 2 a command to maintain it the combustion, which is indicated by a line 12, and on the other hand influenced via a Connection 13 the position of an actuator 14, which in turn also from the burner control 2 via a Line 15 is monitored. The actuator 14 actuates a valve 16 in the fuel line 5 and influences the amount of fuel supplied to the burner 6 over time. In the example described, this is oil or gas, it could but autf · be coal dust or some other fuel. The actuator 14 also actuates a flap 17 in the main air channel 7. The position of the valve 16 and the flap 17 is set to each other so that theoretically optimal combustion results for every degree of opening. The actuator 14 also operates a Positioner 18, the purpose of which is explained below is.

In a directly adjoining the combustion chamber 1 Exhaust gas channel 19 is an oxygen detector influenced by the residual oxygen content in the exhaust gases 20. which is connected via a line 21 to an exhaust gas regulator 22 which regulates the residual oxygen stands. Four further connections 23, 24, 25 and 39 go from the exhaust gas regulator 22, of which the first one closes a drive 26 of an auxiliary air flap 27 arranged in the additional air duct 8. In the example explained the additional air duct 8 conveys combustion air to the burner 6 parallel to the main air duct 7. If so the auxiliary air flap 27 opens, then more air is available for the combustion process than when it is closed Air flap 27. The additional air duct 8 could, however, also lead to the outside after the air flap 27. The control function of the air flap 27 would then be reversed in that with the air flap 27 open the burner 6 there would be less air available than with the air flap closed.

A temperature sensor 28, which is connected via a connection 29 is connected to an additional controller 30. The additional controller 30 acts on the drive 26. wczn a line 31 serves. The purpose of the additional controller 30 is the permissible setting range of the drive 26 and thus the Auxiliary air flap 27 to change depending on the state of the supplied combustion air. The setting range is then referred to as "permissible" if its changeable limit values are defined in such a way that that in every conceivable operating state of the furnace, a minimal excess of air is always guaranteed.

In the example described, only the temperature is taken into account when changing the setting range. In addition, it would be conceivable to also include the atmospheric pressure and / or the moisture content of the air. The additional controller 30 ensures that the permissible setting range of the auxiliary air flap 27 is adapted in accordance with the temperature of the combustion air in the direction of reducing or increasing the setting range and thus the residual oxygen content. For this purpose, as shown in FIG. 2 can be seen, in the drive 26 there are border-near 32, 33, 34, which come into action at graded intervals from the end position of the auxiliary air flap 27 corresponding to the minimum residual oxygen content. In the example described , the limit switches 32, 33, 34 and the limit switch 40 change their switching position during the closing process of the auxiliary air flap 27 in the order listed. The border guards 32, 33, 34 provide the option of preselecting different border end positions. as explained below, and in which the possible end positions of the auxiliary air flap 27 can be changed in three fixed stages. Such a change could also be made in other ways, e.g. B. steadily between two limit positions achieve.

In the example of FIG. 2, the additional controller 30 contains three switching elements 35, 36 and 37. Their switching positions can be influenced by the temperature sensor 28. The commands coming from the exhaust gas regulator 22 via the connection 39 for reducing the residual oxygen content as a function of the temperature of the combustion air are fed to a motor 38 of the drive 26. For this purpose, a command on the connection 39 is forwarded, depending on the setting of the switching elements 35, 36, 37, through one of the lines 31 to one of the limit switches 32, 33, 34, which restrict the setting range to different degrees. One output each of the limit switches 32, 33, 34 is connected to a closed connection 41 of the motor 38 via the limit switch 40. A neutral conductor N and an open connection 42 also lead to the motor 38. A second limit switch 43 is connected between the connection 23 and the open connection 42. The two limit switches 40 and 42 determine the overall setting range of the auxiliary air flap 27.

An alarm device 44 is via the connection 25 (Fig. 1) directly with the exhaust gas regulator 22 and with a Line 45 connected to the two limit switches 32 and 33 (FIG. 2).

The position transmitter 18 continuously reports the current output of the combustion system based on the degree of opening of the actuator 14 to a guide transmitter 46, which influences the setpoint value of the exhaust gas regulator 22 via the connection 24. Depending on the fuel, in the example described! oil or gas, a different behavior of the guide sensor 46 is necessary, which is indicated by a switch 47. The Füh ^r tJngsgeber 46 causes, for example, the sampling of various cams for controlling the fuel / air

Ratio and the setpoint of the exhaust gas regulator 22, depending on whether oil or gas is being burned.

The system works as follows:

The power controller regulates the current heat demand, recorded by the temperature sensor 9 10 a certain position of the valve 16 and the flap 17, the opening ratio of which is fixed to one another what is predetermined is what is advantageously achieved mechanically via the cams mentioned. When assigned The opening ratio would theoretically result in optimal combustion with an ideal setting, which, however, cannot be achieved in practice because variables are not recorded. The oxygen detector 20 therefore compares the residual oxygen content of the exhaust gases with that specified by the command transmitter 46 on the exhaust gas regulator 22 Setpoint and influences the drive 26 and thus the auxiliary air cap via the connections 23 and 39 27

If unfavorable conditions coincide, the command from the exhaust gas regulator 22 goes too far given to drive 26 to reduce the residual oxygen content, an alarm is triggered, as described below:

The switching elements 35, 36, 37 are set, for example, so that the switching element 35 at an air temperature below 30 ^° C.

the switching element 36 at an air temperature below 10 ⁰ C, and

the switching element 37 at an air temperature below 20 ^° C

its in the fig. 2 assumes left switch position. This triggers an alarm at different limit positions of the auxiliary air flap 27. In the example shown in FIG. 2, the switching element 37 is in its right position and the switching elements 35 and 36 are on the left. The temperature of the combustion air is accordingly between the values 10 and 20 ^e C. The close commands coming from the exhaust gas regulator 22 through the connection 39 on the additional regulator 30 pass through the switching elements 37 and 36 and one of the lines 31 to the limit switch 33, which is now activated for the limitation of the extreme position of the auxiliary air flap 27, and from there via the limit switch 40 to the motor 38. Provided that the close command is only issued so long that the auxiliary air flap 27 is not in the The closed position assigned to the limit switch 33 is running, the control process of the exhaust gas regulator 22 is not intervened. Its open commands go via line 23 directly to motor 38. If, under the conditions described, the auxiliary air flap 27 closes so far that the limit switch 33 switches, then the alarm device 44 is switched on via line 45. Simultaneously with an alarm, this causes this A detuning of the exhaust gas regulator 22 via connection 25 (FIG. 1), which opens the auxiliary air flap 27 again by an open command at its connection 23 has less of an impact than CO and soot formation.

Instead of the described structure of the system with an additional air duct 8, the drive 26 can instead of the additional air duct also act directly on the connection between the flap 17 and the valve 16 and thus also influence the fixed fuel / air ratio. In this case the maximum possible influencing of the fuel / air ratio by the additional controller 30 who is limited

In addition, it should be noted that instead of an action of the exhaust gas regulator 22 on the air supply the amount of fuel can also be influenced in order to then influence the fuel / air ratio in this way to reach.

Due to the constant monitoring and the included recording of the condition of the combustion air including the continuous review of the position of the auxiliary air flap 27, it is possible when The basic setting on the occasion of the commissioning of a system is a generally lower residual oxygen content than before, which allows a general reduction in the residual oxygen content and thus in large System enables considerable energy savings.

1 sheet of drawings

Claims (1)

1 2 oil-. Gas or coal dust burners must be Claims against a complete combustion the stoichiometrically required air volume always with air 1 Procedure for regulating the residual oxygen excess can be operated in order to prevent soot and CO build-up in the ASLs. The losses mean in the combustion IAIE% mhtek Rines power controller by a non-participating Luftante.le, we-Be ^g einnussung of the supplied air before BrerLtoff- and the efficiency reducing to K.emhal ^ · quantitative comparison in a mutually fixed tong According to the CH-I ^ 6 15 496 hook, these losses are continuously known to the current heat demand, with a solid-state electrolytic Sauer-EeOaBt wirT i ° substance detector in the exhaust gas duct continuously the remaining heat. in the case of measuring an oxygen content with a residual oxygen detector ^ and with an exhaust gas regulator, which acts on an actuator to additionally control the ratio of fuel and change the amount of air to be fixed by the capacity regulator. split fuel / air ratio, which in large systems such as district heating plants or industrial Setpoint of the second controller depending on the thermal systems, so-called modulating burners of the current output of the combustion system are used. needs to be adapted. The necessary simultaneous identification ^; chnet adjustment of a fuel and an air actuator that the second control range of the actuating value (26, 27) influenced by the second control 20 must always be dependent on one another in a certain ratio (22). This is usually done using jCurvenscne.oen. The **. U Kiekeit on the state of the supplied combustion resulting residual oxygen content in the exhaust gases will be planning air changed and then b by the exhaust regulator in addition ausgeregeltJ * " that if the value falls below a limit, this makes the control more difficult. that the Adjustment range with simultaneous enlargement of 25 burners for stable operation at partial load with one the bell in Ala ^ is triggered. larger excess air, that is, with larger ones Z The method according to claim 1. characterized by residual oxygen content, must be operated as in that for the detection of the state of the combustion full load This is explained by the at full load according to a temperature sensor (28) of an additional greater turbulence and better diameter of the combustion chamber knob (3P is used, according to the 30 research of fuel and air as at low load It temperature of combustion air to the setting range is, therefore, necessary to set the target value of the exhaust regulator in Abdes actuator (26, 2 /) in Rica Tung a Reduce depending on the current burner output to increase or increase the setting range and so control, whereby, depending on the fuel, different dependencies of the residual oxygen content must be adjusted and used as a basis Apart from the combustion air-dependent limit position, the alarm still follows the influence already mentioned de triggers variables and at the same time taking into account the actuator (26, 27) in: Direction of the increase in the residual oxygen temperature, atmospheric pressure and humidity. stop running ^{speed of the} combustion stage, 3 device for carrying out the method 40 network fluctuations and their effect on the Genach claim 2 characterized. blowing power as well that the actuator (26, 27) one of a drive calorific value fluctuations. SS operated auxiliary air flap (27) is. that in one So that the exhaust gas regulator can cope with all these disturbance variables can close parallel to a main air duct (7), and thus it never becomes an operation set air duct (8) is arranged. and 45 comes with soot or CO build-up, the setpoint must be that in the drive (26) of the auxiliary air flap (27) limit the residual oxygen content relatively high set werschalter (32,33,34) are present, which are graduated. The likelihood of meeting th distances from the minimum residual acidity of several unfavorable states is relatively small and substance content corresponding end position of the auxiliary cores, albeit with their simultaneous occurrence If the air flap (27) responds and soot formation may occur, then the combustion that the additional controller (30) switching elements (35, 36, voltage during the rest of the time Zwangswe.se with a 37) contains the switching positions of which can be influenced from the temperature to the high residual oxygen content sensor (28) so that a motor must also be taken into account in the event of a de (38) of the drive (26) which happens from the second controller (22) fect in the exhaust gas controller A system could Commands to reduce the remaining air for a long time will then be left with a lack of air. Oxygen content as a function of temperature without this being noticed in time, the combustion air over one control area each The invention is based on the object, e.ne Em- different restrictive limit switches (32,33, direction to create which can be operated with general 34) contains lower residual oxygen content in the exhaust gases than up to 60 and an alarm is triggered in the event of a fault.