Facility for cleaning filters and method for operating a facility for cleaning filters

p0001The present invention relates to an installation for cleaning filters, in particular made of textile filter material, with a compressor, via which a cleaning gas to a cleaning pressure is compressible and may be passed into a pressure vessel wherein the pressure vessel, a cleaning tube is connected, by means of which the cleaning gas can be injected via nozzle holes in a filter, and a method for operating a plant for cleaning filters.

p0002The <patcit id="pcit0001" dnum="DE3939645"><text>DE 39 39 645</text></patcit> discloses a dust with tubular filter elements, which are traversed by a raw gas, so that can settle to be filtered particles on the filter. To clean the filter elements, at certain intervals a backflowing purge gas is used, which the filter from the clean gas side to the raw gas flows through so that the dust from the outside of the filter elements is released.

p0003A filter element for such a cleaning system is for example in the <patcit id="pcit0002" dnum="DE9103538"><text>DE 91 03 538</text></patcit> described.

p0004In such dust collectors the cleaning is done with a, for example, 6 bar compressed cleaning gas that is then injected in opposite directions into the tubular filter elements. The blast of compressed air required for cleaning is produced that with almost sound velocity exiting a nozzle propulsion jet secondary air sweeps from its surroundings. However, the generation of high pressure and the throttling losses of the cleaning gas at the valves and the nozzles provide a relatively high energy consumption. It must be considered that gases in an orifice of a nozzle or a valve may only be up to the critical pressure, the Laval pressure, relaxed, no matter how low the back pressure is lowered behind the mouth.

p0005It is therefore an object of the present invention to provide a plant for cleaning of filters which enables effective cleaning of the filter with low energy consumption.

p0006This object is achieved with a system for cleaning filters with the features of claim 1 and a method having the features of claim 15th

p0007According to the invention for closing the pressure vessel connected to the cleaning tube, a, are provided in relation to the cleaning of the compressor pressure in the subcritical range mainly operating diaphragm valve, via which the injection of purge gas is controlled in the filter. This throttling loss can be avoided by to small flow cross-sections or to large pressure differences. The diaphragm valve therefore operates mainly in the subcritical range and the flow cross sections are dimensioned such that only slight throttling losses occur. It should be allowed a supercritical state through a partially open valve body. Only when the valve is fully open to provide a subcritical states. This also allows the output pressure of the cleaning gas can be lowered, which reduces the energy required for compression of the cleaning gas. This allows a demand generating pressure and quantity of the cleaning gas. This ensures that a pressure of the cleaning gas is generated only in the extent that it is necessary for the next cleaning process. In addition, short response times of the diaphragm valve to avoid further loss of compressed cleaning gas so that work can be conducted particularly efficiently the plant.

p0008Preferably, the pressure in the pressure vessel via a controller depending on the required cleaning pressure on the cleaning tube is controllable.

p0009The compressor can supply the pressure vessel immediately after each cleaning process again with compressed cleaning gas so that only the one in the pressure vessel back pressure acting on the compressor.

p0010Furthermore, can be detected by a pressure difference measurement the degree of contamination of the filter, the length of the cleaning intervals depends controllable by the degree of soiling. This can be controlled according to demand the plant for cleaning filters, ie at a lower contamination of filter cleaning intervals can be extended and shortened in heavy contamination. Depending on the necessary length of the cleaning intervals, control can control the power of the compressor for compressing the purge gas in the pressure vessel.

p0011Preferably, the cleaning tube has an essentially constant flow cross section. The cleaning tube may be bent or tubular design, are being reduced or avoided by the constant flow cross section throttling losses.

p0012For a quick control of the diaphragm valve that is preferably connected on the opposite to the pressure vessel side to a ventable line. Further, the diaphragm valve can be connected on the side opposite to the pressure vessel side via a line with a pressurized auxiliary storage can be so that the diaphragm valve either vented or closed quickly. For the effective connection of the membrane valve, a 3-2-way valve is preferably provided, which is connected to a first port for venting a container to ambient pressure and is connected to a second terminal to the auxiliary memory for acting on the membrane valve with compressed cleaning gas.

p0013According to another embodiment of the invention, a cleaning pressure between 2 is provided bar to 3.5 in the pressure vessel. This means the system can be operated with significantly lower pressure in the pressure vessel than in conventional cleaning systems. This reduces the energy consumption of the compressor supplying the pressure vessel. In this case, up to 2.5 bar fall in the pressure vessel during a cleaning process the pressure, which is the pressure amplitude in the pressure vessel, and then recharged to the initial cleaning pressure by the compressor.

p0014To reduce the compressed air consumption, it is also advantageous if the opening time of the diaphragm valve is relatively short, thereby reducing loss of purge gas can be avoided that arise as long as the pressure in the cleaning tube is not the requisite for the purification level has reached or no longer has.

p0015The invention will be explained in more detail using an exemplary embodiment with reference to the accompanying drawings. Show it:<dl id="dl0001"><dt>figure 1</dt><dd>a schematic view of an installation according to the invention for cleaning filters;</dd><dt>figure 2</dt><dd>a pneumatic circuit diagram for operation of the system of <figref idrefs="f0001">figure 1</figref>;</dd><dt>figure 3</dt><dd>a pressure-time diagram for a cleaning cycle;</dd><dt>figure 4</dt><dd>a pressure-time diagram for a cleaning cycle with a slow closing diaphragm valve, and</dd><dt>figure 5</dt><dd>a pressure-time diagram of the pressure vessel.</dd></dl>

p0016A plant 1 for purification of a filter disposed on a filter vessel 2 having an inlet 3 for crude gas which flows into a filter chamber 4th In the filter chamber 4, a plurality of tubular filtering elements 5 is arranged, which flows through the raw gas so that then the filtered raw gas can leave as clean gas through an outlet 6, the filter chamber 4th The individual filter elements 5 are suspended at a fixed intermediate wall 7 in the filter chamber 4 and supported on a tubular holder eighth

p00175 to clean the individual filter elements in certain intervals, one cleaning pipe 9 is arranged above the filter elements 5, provided on the directed to an upper opening of the filter elements 5 nozzles 10th Through the nozzles 10 cleaning gas can be blown into the tubular filter elements 5, so that due to the short-term change in flow direction fall on the filter elements 5 separated dust particles in the filter chamber 4 down into a hopper 11, at the end of a rotary valve 12 is arranged.

p0018Other arrangements of pressure vessels, pipe cleaning, nozzles and filter elements are conceivable.

p0019The cleaning pipe 9 for blowing a purging gas is fed via a pressure vessel 13 which is supplied via a compressor 14 with pressurized cleaning gas. In order to control a cleaning operation, a controller 15 is provided, which detects via lines 16 and 17 the pressure in the pressure vessel 13 and in the filter chamber 4 on the raw gas and the clean gas side. The controller 15 can also detect other parameters via sensors.

p0020In <figref idrefs="f0002">figure 2</figref> is a circuit diagram for the inventive system shown for cleaning the filter elements 5, wherein the cleaning tube 9 is shown only in one end portion. The cleaning pipe 9 is frontally closed by a diaphragm valve 20th The diaphragm valve 20 comprises a valve body 21 which is pressed against the end face of the cleaning pipe 9, in order to close this. The valve body 21 is annularly surrounded by an elastic membrane 23, which is arranged in the region of a recess 22 to the pressure vessel thirteenth At the outer circumference the diaphragm is secured 23 by a cover 30 to the pressure vessel thirteenth The cover 30 comprises a connection 31 which via a line 32 a control chamber formed between the diaphragm 23 and the cover 30 connects with a 3-2-way valve 33rd The 3-2-way valve, the conduit 32 connected to a vent line 35, so that drops in the control chamber, the pressure and the diaphragm valve 20 lifts off the valve body 21 from the end of the cleaning pipe. 9 Thus, the opening of the cleaning tube 9 is opened to the pressure chamber 13 side and disposed in the pressure chamber 13 purge gas can flow into the cleaning tube. 9

p0021The 3-2-way valve 33 is connected to a further line 36 to an additional memory 37, which is fed via a line 38 from the compressor fourteenth Is now on the filter controller 15 which is connected to a control line 34 to the 3-2-way valve 33, the connection of the line 32 is closed to vent line 35, the connection from the auxiliary storage 37 via line 36 and 32 open to the control chamber at port 31 out. Thereby, the diaphragm valve 20 is moved by raising the pressure in the control chamber back to the closed position, and the valve body 21 is pressed against the end of the cleaning pipe. 9

p0022The compressor 14 is connected via a line 39 to the pressure vessel 13, and can be both the pressure vessel 13 and the additional memory 37 supply with a pressurized gas. Both in the line 38 to the auxiliary memory 37 and in the line 39 is a valve 40 or 41 is arranged for shutting off the line.

p0023The operation of the plant for cleaning the filter elements 5 may be such that a substantially constant cleaning pressure between 2.5 bar and 3.5 bar is generated both in the pressure vessel 13 and in the auxiliary memory 37, for example, approximately 2.8 bar. Now if a cleaning process triggered initially flowing a purge gas from the control space between cover 30 and membrane 20 via the vent line 35 to the outside to open the diaphragm valve 20th Then, the cleaning gas from the pressure vessel 13 to flow into the cleaning tube 9, wherein the flow cross-sections and the pressure conditions are such that the flow is in the subcritical range.

p0024Subsequently, 10 cleaning gas is blown into the filter elements 5 from the pressure vessel 13 through the purification pipe 9 and the nozzles. Also at the nozzles 10 preferably prevail subcritical flow conditions, what about the cleaning pressure in the pressure vessel 13 or the flow cross sections of the nozzles 10 is indirectly influenced.

p0025The diaphragm valve 20 can now by closing the 3-2-way valve 33 can be closed again, in which case on the addition memory 37 line 32 and the control room are adjacent applied to the diaphragm valve 20 with pressure. The opening and closing of the diaphragm valve 20 may in a very short period of, for example, less than 0.2 s, in particular less than 0.15 s to take place, so that the flow losses are kept low.

p0026In <figref idrefs="f0002">figure 2</figref> is only shown schematically the pneumatic circuit diagram of the plant. The 3-2-way valve 33 may be arranged directly on the cover 30 in order to minimize the volume of the line 32 and to ensure a fast response of the diaphragm valve 20th In addition, other valves and control lines can be provided in order to ensure the function of the system. The controller 15 can detect the pressure in all the lines.

p0027In <figref idrefs="f0003">figure 3</figref> shows a pressure-time diagram of a cleaning operation. After a time of 0.05 s, the diaphragm valve is opened, so that momentarily increases the cleaning tube 9 of pressure of 0 bar (atmospheric pressure) bar to 2. By opening of the diaphragm valve 20, the purge gas from the pressure vessel 13 in cleaning pipe 9 flows, so that the pressure in the pressure vessel 13 is reduced from initially 2.8 bar to about 2 bar. The pressure amplitude during a cleaning process can be bar in a range between 0.5 to 2.5 bar. Then the diaphragm valve 20 is abruptly closed, and the cleaning pipe 9 will then return to the initial pressure of 0 bar (atmospheric pressure) a. The pressure vessel 13 must be replenished from 2 bar to 2.8 bar above the compressor 14 again. In addition, some cleaning gas in the auxiliary memory 37 has to be initiated so that is replenished at the vent emanated cleaning gas.

p0028Since the cleaning gas must first be generated by the purging, only against the residual pressure in the pressure vessel 13 and are produced to reach the cleaning pressure only to the currently existing in the pressure vessel 13 pressure, thereby considerably electrical energy is saved. The energy consumption of the compressor 13 is strongly dependent on the counter-pressure or pressure ratio. The necessary pressure will be varied cleaning of the filter control and adapted to the operating conditions of the filter system.

p0029<figref idrefs="f0004">figure 4</figref> shows a pressure-time diagram for a cleaning cycle with an overall long opening hours. Before closing the solenoid valve, the pressure in the cleaning tube is already fallen below the necessary level of effectiveness .. The pressure amplitude in the cleaning tube 9 remains the same as for the diaphragm valve with 2.4 bar of<figref idrefs="f0003">figure 3</figref>, The pressure drop in the pressure vessel 13 is, however, bar considerably around. 2 Considering the closing behavior one sees a gently sloping curve, which in turn represents a large loss due to ineffective cleaning gas. In addition, it can be seen that due to the low flow losses in the diaphragm valve, the pressure in the compressed air reservoir 13 and in the cleaning tube 9 during the closing of the membrane valve is almost identical. By the analog measurement of the pressure in the pressure vessel and processing of the pressure in the control, it is possible to close the diaphragm valve in time and to prevent the loss of purge gas.

p0030In <figref idrefs="f0005">figure 5</figref> an example is shown for a pressure-time diagram of the pressure vessel at the start of several cleaning cycles. The generation of compressed air at the first filling process takes about 295 s. After the purging, the form in the compressed air reservoir from dropping by about 0.85 bar to 1.95 bar. The generation of per cleaning consumed pressure takes about 75 seconds. This is the minimum time interval between two Abreinigungsvorgängen is determined.

p0031The filter system can detect the contamination or clogging degree of the filter elements 5 by means of differential pressure measurement. Depending on the degree of clogging, the controller can determine the length of the pause time between each Abreinigungsvorgängen, for example, by controlling the power of the compressor. The minimum time between two Abreinigungsvorgängen is therefore equal to the time it takes The compressor 13 for increasing the pressure of the cleaning gas to the required cleaning pressure. The compressor 13 may then be operated at constant speed for a certain degree of pollution substantially. Furthermore, the maximum pressure in the compressed air accumulator can be controlled via the control.