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(11) | EP 1 666 794 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Air control |
(57) The invention relates to a method for controlling a fire bed, which method comprises
the steps of:
The invention further relates to a device for controlling a fire bed in a combustion chamber, which device comprises:
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[0002] In an incinerator waste is burned in a fire bed. The flue gases from this fire bed are discharged into the open air via a chimney. The flue gases contain a large quantity of carbon dioxide but, as a result of incomplete combustion, these flue gases also contain harmful substances, such as for instance carbon monoxide. It is of great importance in such incinerators that the quantity of harmful substances discharged into the outside air be kept as low as possible.
[0003] It is known with incinerators to blow in, at the fire bed, the air necessary for complete combustion. This quantity of air is usually adapted to the amount of material to be burned. In order to determine the required quantity of air the composition of the flue gases is measured, and the quantity of air to be blown onto the fire bed is determined on the basis hereof.
[0004] The incineration of waste is never homogeneous, whereby there are zones in the fire bed which burn better, more rapidly and more cleanly than other zones in the fire bed. These latter zones often produce a higher content of carbon monoxide than the zones where incineration takes place properly.
[0005] When additional air is blown in to prevent harmful gases, the problem occurs that the amount of flue gases in kilos increases per kilogram of waste, which in turn entails higher costs for cleaning the flue gas.
[0006] The cost of maintenance and purchase of the installation for blowing in air further depends on the required quantity of air. This installation also consumes energy during use, which reduces the efficiency of the incinerator as a whole. It is therefore important to keep the air supply installation as small as possible, while a low level of harmful substances in the flue gases is nevertheless achieved.
[0007] It is now an object of the invention to provide a control which makes it possible to achieve a low content of harmful substances with a minimal quantity of air.
[0008] This object is achieved with a method according to the invention, which method comprises the steps of:
- scanning the intensity of the fire bed; and
- blowing in air at the position of a zone of increased intensity.
[0009] Using this method the fire bed is monitored, and, as soon as a zone is present in the fire bed where the combustion process is incomplete, a gas such as air is blown in at the position of this zone so as to ensure that sufficient air is available locally to bring about a complete combustion process, and whereby the amount of harmful substances is minimized.
[0010] The invention further comprises a device for controlling a fire bed in a combustion chamber, which device comprises:
- scanning means arranged above the fire bed for scanning the intensity of the fire bed;
- blow-in means for blowing in air locally above the fire bed;
- control means for controlling the blow-in means on the basis of the scanned intensity of the fire bed.
[0011] The scanning means monitor whether the fire bed is homogeneous and, as soon as there is a peak in the fire bed, the blow-in means are actuated so as to blow in locally a gas such as air.
[0012] In a preferred embodiment the scanning means comprise a matrix for optically detecting the intensity of the fire bed. Sensors can here preferably comprise an optical fibre and a light-sensitive element connected thereto.
[0013] Because of the high temperatures in an incinerator the sensors must meet high standards. It is possible by applying optical fibres to place the more sensitive equipment outside the combustion gases.
[0014] In another preferred embodiment of the device according to the invention the blow-in means comprise a matrix of nozzles. Air can be blown in locally using these nozzles.
[0015] A highly preferred embodiment of the device according to the invention comprises a number of pipes which extend substantially horizontally above the fire bed and through which flows coolant, which pipes are connected to each other by separating walls to form a hollow element. Because a coolant flows through the pipes, the temperature in the hollow element is considerably lower than the temperature of the flue gases just outside the hollow elements.
[0016] In a preferred embodiment the device according to the invention comprises a number of such hollow elements in which the scanning means and the blow-in means are arranged. Because the temperature in these hollow elements is low, it is still possible to place more sensitive equipment in the flue gases.
[0017] When the hollow elements have a great width relative to the channel in which the elements are arranged, the further advantage is then achieved of a good mixing of the flue gases. Blowing-in of air also contributes thereto.
[0018] These and other features of the invention are further elucidated with reference to the accompanying drawings.
Figure 1 shows a side view of an incinerator having therein a device according to the invention.
Figure 2 shows a perspective view of a hollow element of the device of figure 1 seen from below.
Figure 3 is a perspective top view of two mutually opposite hollow elements as according to figure 2.
Figure 4 is a top view of the device according to the invention.
[0019] Figure 1 shows an incinerator with side walls 2, a fire grate 3 on which burning waste V is being incinerated. Above this grate 3 is placed a device according to the invention which consists of hollow elements 1. These hollow elements 1 are connected to side walls 2.
[0020] A hollow element 1 according to the invention is shown in more detail in figure 2. Side walls 2 consist of pipes 4 and partitions 5. A coolant runs through pipes 4 in order to thus hold the side walls at a reasonable temperature. These pipes 4 are bent out of the plane of side wall 2 so that pipes 6 and 7 form together with separating walls 8 and 9 a hollow element. Arranged in separating wall 9 are openings 10 through which air can for instance be blown, or behind which openings a sensor can for instance be placed.
[0021] Figure 3 shows a perspective view of two hollow elements placed opposite each other. An opening 11 is provided through hollow elements 1 so that access is created to hollow elements 1 from outside side walls 2. Air L can for instance be blown in or the cables for the sensors can run via this opening 11.
[0022] Figure 4 shows a top view of the whole device according to the invention. This device consists of a lower layer of hollow elements 12 which at different points L1-L12 can blow in air directed at the fire bed, as shown in figure 1. Above this layer of air-blowing hollow elements 12 is placed a second layer of hollow elements 13 which incorporate sensors. These sensors S1-S12 detect the intensity of the fire bed lying thereunder. When for instance sensor S2 detects an increased intensity of the fire bed, which means that the combustion is not complete and harmful substances are therefore being released, the control can blow in air via holes L1, L2, L5 and L6, whereby extra air is provided locally and whereby the combustion process can still be complete, so that the formation of harmful gases is reduced. In the simplest form of the hollow elements, air is simultaneously blown out via two openings when the air is blown in. It is however also possible to provide valves, whereby blowing-in can take place more locally. When for instance sensor S9 measures an increased fire intensity, it is possible to ensure with hollow elements 12 provided with valves that air is blown in only via openings L6, L7, L10 and L11. In this manner the fire bed can be controlled by blowing in extra air at the correct positions, and the emission of harmful flue gases is reduced.
1. Method for controlling a fire bed, which method comprises the steps of:
- scanning the intensity of the fire bed; and
- blowing in air at the position of a zone of increased intensity.
2. Device for controlling a fire bed in a combustion chamber, which device comprises:
- scanning means arranged above the fire bed for scanning the intensity of the fire bed;
- blow-in means for blowing in air locally above the fire bed;
- control means for controlling the blow-in means on the basis of the scanned intensity of the fire bed.
3. Device as claimed in claim 2, wherein the scanning means comprise a matrix of sensors
for optically detecting the intensity of the fire bed.
4. Device as claimed in claim 3, wherein the sensors comprise an optical fibre and a
light-sensitive element connected thereto.
5. Device as claimed in any of the claims 2-4, wherein the blow-in means comprise a matrix
of nozzles.
6. Device as claimed in any of the claims 2-5, comprising a number of pipes which extend
substantially horizontally above the fire bed and through which flows coolant, which
pipes are connected to each other by separating walls to form a hollow element.
7. Device as claimed in claim 6, comprising a number of hollow elements in which the
scanning means and the blow-in means are arranged.