EP0030321B1 - Method and apparatus for optimizing an electrofiltration plant - Google Patents

Description

The invention relates to a method and a device for optimizing an electric fitness system.

For the separation of dust, electrostatic filters have been known for a long time, in which the dust particles are electrically charged and deposited on electrodes. The separation performance is roughly proportional to the square of the filter voltage. Control methods and circuits for such filters are known for example from Siemens magazine 1971, pages 567-572.

There are now electrostatic precipitators that consist of a series of individual chambers that are connected in parallel and / or in series. If you provide a separate power supply system with control for each of these chambers, you can think of the entire system as being composed of a series of individual electrostatic filters. For reasons of keeping the air clean and / or recovering valuable useful dust, it is often of the greatest interest in an electrostatic precipitator to keep the separation efficiency and thus the degree of dedusting at a predetermined value. For this purpose, the dust load of the smoke or gas leaving the system can be measured and then intervened accordingly in the system.

The object of the present invention is to optimize an electrostatic filter system with regard to energy expenditure and separation.

This object is achieved according to the invention in that the electrical energies supplied to the individual electrostatic filters are automatically changed iteratively in such a way that the total sum of the energies tends to a minimum for a given dust load at the system outlet. Alternatively, for optimization, the dust load to be specified is automatically determined by comparing the total energy to be used with the amount of usable dust that can be separated.

In the first way, the separating power is distributed to the respective filter in such a way that the most favorable efficiency - d. H. electrical effort for the separated amount of dust - results.

In the case of a device for carrying out the method, a master controller controlling dust loading and energy minimum is advantageously superimposed on the energy controllers of the individual filters, which regulates the reference variables for the controllers. In this case, the individual controllers are preferably designed as microcomputer systems which are connected via a collective bus to a master computer serving as a master controller.

The invention will be explained in more detail with reference to an embodiment shown in the drawing;

• Figur 1 ein schematisches Schaltbild der Anlage und
• Figur 2 Zusammenhänge zwischen Staubbeladung und Energieaufwand in den einzelnen Filtern.

show it :

• Figure 1 is a schematic diagram of the system and
• Figure 2 Relationship between dust loading and energy consumption in the individual filters.

The schematically shown electrostatic filter system consists of the individual filters 1, 2 and 3; the gas stream 6 to be cleaned flows through the individual filters 3 to 1 in the direction of arrow 7 one after the other.

As indicated schematically in Figure 1, each electrostatic filter 1 consists of the actual filter part 11 with the electrodes for separating the dust and a voltage drop 12, which is constructed in a manner known per se from a thyristor actuator connected to an AC network, a high-voltage transformer and a secondary-side high-voltage rectifier . By controlling the thyristor actuator via the controller 13, a predetermined DC voltage can be maintained on the secondary side.

The dust load prevailing at the outlet of the system is recorded with a measuring device 5 and the degree of dedusting D _; in a master controller 4 designed as a computer, compared with a predetermined target value D. This then specifies the individual energy setpoints U _s via the data bus 41 to the controllers 13, 23 and 33 of the filters 1, 2 and 3.

The power E1 supplied to the electrostatic filter 1 is e.g. B. detectable by the product of primary voltage and primary current or by the secondary filter sizes. A signal proportional to this power E1 is fed to an energy minimum controller 42 in the master controller 4. At the same time, the signals E2 and E3 of the filters 2 and 3 are supplied with signals proportional to this controller 42. This forms the sum Σ of the energies and influences the master controller 4 in such a way that the energy sum becomes a minimum; This is done by appropriately specifying the individual setpoint energies U _s to the individual controllers 13, 23 and 33.

Figure 2 shows these relationships of the regulation.

It is Z. B. required to keep the dedusting to the value specified with D _a . This occurs up to time t1 through the distribution of the electrical energies E1, E2 and E3 shown on the individual filters 1, 2 and 3. This then gives the total energy ΣE.

At time t1, the energy of filter 1 is reduced by the amount ΔE. This does result in a reduction in the total energy ΣE, but at the same time in a reduction in the actual dedusting degree D _i . At time t2, the power E2 supplied to the filter 2 is therefore increased. This brings the dedusting level back to the old value D _; , but results in an increase in the total energy consumption ΣE compared to the original state. A different strategy is therefore used at time t3, namely the energy E1 is increased. This also increases the rejection degradation above the required dimension D _s , therefore at time t4 the performance of the filter 2 is reduced to such an extent that the predefined degree of dedusting D, results again. As a result of this intervention, the total energy ΣE required for the electrostatic precipitator system is also reduced for a given degree of dedusting. The method described above is then continued iteratively by changing the individual values during the operation of the electrostatic filter system, so that the system always works at the optimum energy.

The procedure described above, which can be carried out relatively easily and relatively quickly with the aid of the computer systems, ensures that no more valuable electrical energy is consumed than is required to achieve a predetermined degree of dedusting.

A further optimization strategy for an electrostatic precipitator with regard to energy consumption and separation is given by placing the cost of electrical energy in relation to the value of the useful dust in the master computer and by this resulting in the degree of dedusting to be specified - which of course must be above the legally prescribed standard - is determined.

Claims (4)

1. A process for optimising the expenditure of energy in an installation consisting of a plurality of electrostatic filters, characterised in that the electric energy levels (E1, E2) fed to the individual electrostatic filters (1, 2, 3) are iteratively automatically changed in such manner that the total energy sum (ΣE) tends towards a minimum for a given dust charge (Dg) at the output of the installation.

2. A process for optimising the dust charge of purified gas in an electrostatic filter installation, characterised in that the dust charge (D_s) to be given is automatically determined from the comparison of the total energy (ΣE) to be used with the quantity of the actual dust.

3. A device for implementing the process as claimed in Claim 1, characterised in that the energy regulators (13, 23, 33) of the individual filters (1, 2, 3) are supervised by a master regulator (4) which controls the purified gas dust charge and the energy minimum and which determines the command variables (U_s) for the regulators.

4. A device as claimed in Claim 3, characterised in that the individual regulators (13, 23, 33) are constructed as micro-computer systems which communicate via a bus-bar (41) with a master computer (4) serving as a master regulator.

Images