DE1551963B2 - CONTROL DEVICE FOR BOILER - Google Patents

Description

The invention relates to a control device for boilers for solid fuels, which are filled in stock in which the combustion air supply is regulated depending on the heat demand and part of the supplied combustion air as secondary air in the hot gases behind the fuel supply is fed.

In a known control device of this type, it is controlled how much combustion air in total is fed; the secondary air is branched off from the supplied combustion air in an uncontrolled manner, the remainder of which is supplied as primary air (British patent 493 390). at This device is disadvantageous that the chemically correct assignment of combustion air to reacting Fuel is usually not available and there are often considerable deviations from the one used for theoretical air requirement required for perfect combustion. This results in either an excess of air with heat losses caused by the heating of the excess combustion air are conditional, or lack of air, because of the partial combustion that occurs of the fuel to carbon monoxide leads to incomplete fuel utilization. The feed of combustion air in the right amount for perfect combustion can be achieved with the help of a constant Exhaust gas analysis can be achieved. However, this is very complex.

The object of the invention is to provide a control system for boilers of the type mentioned at the outset to create, which makes it possible with simple means, always largely just those for a perfect one To supply the required amount of combustion air to combustion; it is characterized by one of the Combustion air supply control independent control of the secondary air volume, which depends on the The direction of change of the flue gas temperature behind the boiler changes the amount of secondary air so that the exhaust gas temperature reaches a maximum. This results in a very sensitive one in a simple manner and quickly reacting control of the "supply of combustion air is achieved.

From the French patent 806 460 it is known for central heating boilers and the like to add additional air the combustion chamber above the solid fuel independent of the combustion air supply control initiate. However, according to this patent specification, compressed air is blown in intermittently from above, to loosen up the compact fuel block. The blower delivering the compressed air is controlled by a Thermostat on and off, responding to changes in temperature of the heated in the boiler Water responds, so that a very precise monitoring of the water temperature is guaranteed. That the temperature of exhaust gases with complete combustion of the fuel, that is, with chemical correct admixture of combustion air, reached a maximum, is from the German patent specification 540 711 known.

In an embodiment of the invention it is provided that to measure the amount of secondary air a permanent circumferential throttle element is provided, the cross-section of which is constantly increasing and decreasing, and that a temperature tendency sensor is provided in the exhaust gas flow to the change the exhaust gas temperature responds, this temperature tendency sensor the direction of movement of the Throttle body for the secondary air reverses when the exhaust gas temperature begins to fall. Through this becomes an inexpensive, simple and very reliable control device created with the while largely adhering to the optimal. Secondary air volume a special one exact and direct regulation is possible.

The structure and mode of operation of the invention are shown below on the basis of an exemplary embodiment described, which is shown with the essential details in several figures.

In Fig. 1 and 2 is a cross-section and elevation of a solid fuel boiler 1 of conventional design shown for hot water heating, which is equipped with a regulation of the secondary air according to the invention is. The boiler 1 has an ash chamber 3, a grate 5, a space 7 for the fuel, an overlying free space 9 and the post-heating space, which is particularly effective due to ribbing 12 on. The primary air enters the ash chamber 3 and flows through the designated ones in sequence Rooms and leaves as exhaust gas through a smoke pipe 14 with a draft-limiting flap 16 boiler 1. 18 is the ash door, 20 is the drum door. According to the invention, the boiler 1 is additional equipped with a pipe system for the supply of the combustion air, which of course is also more integrated Could be part of boiler 1. The combustion air is regulated by a throttle device 24 and is controlled by a rotary valve 26 on the primary air line 30 and the secondary air lines 32 distributed. The throttle member 24 is via a cable 34, a lever 36 and a temperature sensor 38 controlled by the boiler temperature, there is also a stop 40 for the throttle element 24 forming Throttle valve provided, namely a Bourdon tube connected to a liquid thermometer 42 is connected in the exhaust gas flow and prevents the fire in the boiler 1 from going out. The rotary valve 26 is rotated slowly by a motor 28. Its rotary movement is controlled by a temperature sensor 44 in the exhaust gas flow and determined by a control unit 47. For a good mix the heating gases and the secondary air is provided by the supply of the secondary air via many holes in the two secondary air lines 32 and a grid 46 made here of bars. The reaction of secondary air and oxygen is ensured by a catalyst 48, which in usual Way consists of a bed of catalyst material in a wire cage.

In Fig. 3 and 4, the rotary valve 26 for distributing primary air and secondary air is shown larger. Fig. 3 shows a longitudinal section, Fig. 4 shows a cross section through rotary valve 26 and pipe branching. The contour of the rotary valve 26 is here half a circular cylinder, the surrounding housing with the two control edges 33 is designed so that the sum of the control cross-sections approximately is constant. A small bypass line 31 bypasses the control cross section of the rotary valve 26 and also connects the primary air line 30 to the air inlet 29. This prevents that when the regulation goes out of action, the primary air supply is completely shut off and the fire goes out.

Fig. 5 shows an embodiment of the temperature tendency sensor 44 in longitudinal section. It consists of

whose cross-section is constantly increasing and decreasing, and that a temperature tendency sensor in the exhaust gas flow (44) is provided, which is responsive to the change in the exhaust gas temperature, this temperature tendency sensor (44) the Direction of movement of the throttle member (rotary valve 26) for the secondary air reverses when the exhaust gas temperature begins to drop.

5. Control device according to claim 4, characterized in that the temperature tendency ίο Sensor (44) has a tube (52) closed on both sides, in which a second tube closed at the top Tube (54) is arranged, which is down in a mercury filling (60) in the outer tube (52) immersed that both tubes (52, 54) are filled with the same gas and that in the outer tube

(52) a pair of contacts (56, 58) is arranged, which is closed by the mercury (60), when it rises in the annulus between the outer and inner pipe.

6. Control device according to claim 4 or 5, characterized in that the direction of rotation the drive motor (28) of the throttle member (rotary valve 26) by a reversing relay with two Pole pairs is determined, the two switching positions of which are stable without coil current, wherein to switch over the coil (68) of the relay via the switchover contact (56, 58, 60) in the temperature tendency sensor (44) is connected to a capacitor (70), the charging of which is polarized via the outputs of the reversing relay with interposed protective resistors (72, 74).

1 sheet of drawings