DE4111673C1 - - Google Patents

Abstract

In this method, a specific number of discharges is provided per time unit DSi in each case in n successive steps, and the voltage Ui which arises is determined, the individual values of the discharge voltage UiD being determined as a function of time t. The values <IMAGE> and <IMAGE> are determined for i = 1 to n, and the values Vhi of in each case two successive steps are compared to one another, this comparison being used in order to select the number of discharges per time unit in succeeding steps. <IMAGE>

Description

The invention relates to a method for determining the optimal number of breakdowns per unit time Ds _n in an electrostatic precipitator.

Process for optimizing the separation of pollutants in electrostatic precipitators are known. In the GB-PS 9 81 147 is a method for automatic Voltage control in an electrostatic precipitator described in which a continuous measurement of the Voltage curve is carried out during operation and ongoing calculation of the voltage difference between the respective breakdown voltage and that actually adjusting voltage. The so determined Voltage difference is given with a Voltage difference compared. Is the default Voltage difference greater than that determined, so the im electrostatic precipitator applied voltage increased. Is the predetermined voltage difference is less than that determined, so it is in the electrostatic precipitator applied voltage reduced. With this procedure the determined voltage difference by varying the applied Tension changes until it changes with the predetermined voltage difference covers.

In DE-AS 10 80 979 a method for independent Regulation of the voltage of electrical gas cleaning systems described in which an interaction of tension-increasing and tension-reducing impulses on the Control transformer acts in addition to the number of in rollovers that occur over a certain period of time Intensity for determining the change in voltage is used.

DE-OS 32 19 664 describes a method for the detection of Breakthroughs in an electrostatic precipitator in which a voltage value with a Reference value compared and deviations from the reference value can be used to control the voltage regulation. Here becomes the voltage difference between two successive measurements and used as a reference value the in-phase voltage difference of the previous one Half wave. The difference in the absolute values of the two Voltage differences are determined and with a Responsiveness determining value X compared.

In US-PS 45 22 634 a method for controlling a described electrostatic precipitator, in which several values of the breakdown voltage of a building smaller electrostatic precipitators can be processed. With this method, the number of punctures per Unit of time reduced.

In US-PS 29 78 065 an electrostatic Dust collector described in which the voltage is automatically set to the highest possible value and excessive breakdowns are avoided.

In GB-PS 9 56 783 a method for regulating the Voltage of an electrostatic precipitator described, where the intensity of each punch during a certain period of time is measured. The single ones Measured values are summed up and with a predetermined value compared. The voltage in the electrostatic precipitator is increased if the sum is smaller than the specified one Value. The sum is greater than that is the specified value, the voltage in the electrostatic precipitators reduced. With this The process is called "intensity" the quantity  the between the precipitation electrodes during the individual carbon copies in a certain time interval to understand flowing electrical charge.

DE-AS 11 54 076 describes a device for contactless constant voltage regulation of electrostatic precipitators depending on the number of rollovers at which a Arrangement to compare one by integrating the Rollovers in a memory actual value with a continuous or pulsed - preferably on one Memory - given setpoint is provided, which at Occurrence of a control deviation for the actuator Separator voltage actuated. With this procedure the from the rollover target and rollover actual values derived electrical quantities to the Control lines from at least one as a comparison arrangement provided magnetic amplifier that the output signal of the magnetic amplifier immediately the control deviation signal for the contactless, constant regulation of the separator voltage delivers.

The invention has for its object to provide a method for determining the optimal number of breakthroughs per unit time Ds _n in an electrostatic precipitator, which can be carried out relatively quickly and in which an adaptation to fluctuating parameters of the exhaust gas, such as temperature and concentration of the Pollutants is possible.

The object underlying the invention is achieved by a method for determining the optimal number of breakthroughs per unit time Ds _n in an electrostatic precipitator, in which in a first step an arbitrarily selected number of breakthroughs per unit time Ds₁ is specified and up to a point in time t₁ individual values of the self-adjusting the operating voltage U1 are determined, and the individual values of the breakdown voltage U1 _D t is determined as a function of time and wherein the values

be determined, then the value

is determined and in a second step an arbitrarily selected number of breakdowns per unit time Ds₂ is specified and up to a point in time t₂ the individual values of the voltage U2 arising during operation are determined, the individual values of the breakdown voltage U2 _D as a function of Time t can be determined and at which the values

be determined, then the value

is determined, the values Vh₁ and Vh₂ are compared with one another and then n-2 further steps are carried out, the values Vh₃ to Vh _{n being} determined in a corresponding manner and for each different choice of the number of breakthroughs per unit time Ds₃ to Ds _n the following conditions apply:

(Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )

with i = 1 to (n-2).  

The optimal number of breakdowns per unit time Ds _n is to be understood as the number of breakdowns per unit time, the default of which is the greatest efficiency of the electrostatic precipitator. With the proposed method, the optimal number of breakthroughs per unit time Ds _n can be determined both in a wet electro separator and in a dry electro separator. The voltage U1 which arises during operation is to be understood as those voltages which are determined in the first step of the method for determining the optimal number of breakdowns per unit time Ds _n in the electrostatic precipitator. The breakdown voltage U1 _D is to be understood as those voltages in the first step at which a voltage drop occurs immediately after their setting. The voltage usually drops to a residual voltage. The voltages U2 and U2 _D are correspondingly related to the second step of the method for determining the optimal number of breakdowns per unit time Ds _n .

It has surprisingly been found that the method according to the invention allows the optimum number of breakthroughs per unit time Ds _{n to} be determined relatively quickly, with fluctuations in the exhaust gas with regard to temperature and concentration of the pollutants being taken into account.

A preferred embodiment of the invention consists in that the individual time spans between the times t _i-1 to T _i with i = 1 to n comprise 10 to 300 seconds. This ensures that the fluctuations in the exhaust gas with regard to temperature and concentration of the pollutants are detected and taken into account to a sufficient extent.

According to a further preferred embodiment of the invention, the values Vh _{i are used} as a quotient

With

determined, where:

with i = 1 to n.

The breakdown voltages in the i-th step of the method for determining the optimal number of breakdowns per unit time Ds _{n are} to be understood as Ui _D. Ui means the voltages that arise in the i-th step.

The efficiency of an electrostatic precipitator is a function of the effective rate of migration of the individual dust particles for a given separation area of the precipitation electrodes and for a given throughput of the exhaust gas. This effective migration speed is in turn a function of the voltage Ui raised to 2. By introducing the correction factor C _i , the dependence of the efficiency on the voltage Ui potentiated with 2 can be taken into account.

The invention is explained below with reference to the drawing ( Fig. 1 to 3).

Fig. 1 shows the breakdown voltage Ui _D as a function of time t.

Fig. 2 shows the adjusting itself in the operating voltage Ui as a function of time t.

Fig. 3a, 3b, 3c, 3d illustrate schematically the value Vh _i as a function of the number of discharges per unit of time Ds _i.

In Fig. 1, the breakdown voltage Ui _D as a function of time t shown below the breakdown voltage curve 1 with the hatched surface 2. In the i-th step of the method for determining the optimum number of discharges per unit of time Ds _n corresponds to the area of the shaded area 2 in the time interval t _i-1 to t _i to the value Fmax _i.

In FIG. 2, which adjusting the operating voltage Ui as a function of time t with the voltage curve 3. The breakdown voltage curve 1 , which describes the functional relationship between the breakdown voltage Ui _D and the time t, is also shown in dashed lines. In an i-th step of the method for determining the optimal number of breakdowns per time unit Ds _n , the area of the hatched area 4 under the voltage curve 3 corresponds to the value fact _i . In each individual step of the method for determining the optimal number of breakdowns per time unit Ds _n , the voltage Ui is first increased until it reaches the value of the breakdown voltage Ui _D. This happens when the voltage curve 3 affects the breakdown voltage curve 1 for the first time, starting from the coordinate origin in the positive direction of the time axis (abscissa), as shown in FIG. 2. In the event of a breakdown, the voltage suddenly drops to a residual voltage 5 .

After deionization of the exhaust gas, the voltage is increased according to the voltage curve 3 until the next breakdown. The process is continued in the same way until the specified time span of the step has expired. The individual values Ui are measured and the voltage curve 3 is completely created. The breakdown voltage curve 1 is created with the aid of the individual values Ui _D , which are also known from the ongoing measurement of the voltage Ui. It is advantageous to connect the measured values Ui _D either by straight lines or to specify a calculated function in the form of a breakdown voltage curve 1 , as shown in FIGS. 1 and 2. After the areas of the hatched areas 2 and 4 have been calculated, the value Vh _i can be determined. In practice, the values Vh _{i are determined} by a computer. The one step of the method for determining the optimal number of breakthroughs per unit time Ds _n is immediately followed by the next step. If the first two steps have been carried out, there are two values Vh _i which are compared with one another. The choice of the number of carbon copies per unit time Ds₃ for the third step is then made taking into account the following conditions, which are illustrated in Fig. 3:

• a) If Vh₂ is greater than Vh₁ and Ds₁ greater than Ds₂, as shown in Fig. 3a, Ds₃ must be chosen smaller than Ds₂.
• b) If Vh₂ is larger than Vh₁ and Ds₁ is smaller than Ds₂, as shown in Fig. 3b, then Ds₃ must be chosen larger than Ds₂.
• c) If Vh₂ is smaller than Vh₁ and Ds₁ larger than Ds₂, as shown in Fig. 3c, then Ds₃ must be chosen larger than Ds₂.
• d) If Vh₂ is less than Vh₁ and Ds₁ less than Ds₂, as shown in Fig. 3d, Ds₃ must be chosen less than Ds₂.

If the third step of the method for determining the optimal number of breakthroughs per time unit Ds _{n is} carried out, the values Vh₃ and Vh₂ are compared in a corresponding manner and the corresponding number of breakthroughs per time unit Ds₄ for the fourth step is selected and specified accordingly. Ideally, the areas of the hatched areas 2 and 4 are the same, so that a value of 1 results for Vh _i . The optimum number of breakthroughs per unit time Ds _n is reached when the value Vh _i can no longer be increased by further steps and the value Vh _n is thus reached.

Claims (3)

1. A method for determining the optimal number of breakthroughs per unit time Ds _n in an electrostatic precipitator, in which in a first step an arbitrarily selected number of breakthroughs per unit time Ds₁ is specified and up to a point in time t₁ the individual values of the values that arise during operation Voltage U1 are determined, the individual values of breakdown voltage U1 _{D being determined} as a function of time t and at which the values be determined, then the value is determined and in a second step an arbitrarily selected number of breakdowns per unit time Ds₂ is specified and up to a point in time t₂ the individual values of the voltage U2 arising during operation are determined, the individual values of the breakdown voltage U2 _D as a function of Time t can be determined and at which the values be determined, then the value is determined, the values Vh₁ and Vh₂ are compared with one another and then n-2 further steps are carried out, the values Vh₃ to Vh _{n being} determined in a corresponding manner and for each different choice of the number of breakthroughs per unit time Ds₃ to Ds _n the following conditions apply: (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} )
⟩ (Vh _{i + 1} <Vh _i ) ∧ (Ds _i <Ds _{i + 1} )
⇒ (Ds _{i + 2} <Ds _{i + 1} ) with i = 1 to (n-2). 2. The method of claim 1, wherein the individual time spans between the times t _i-1 to t _i with i = 1 to n comprise 10 to 300 seconds. 3. The method of claim 1 or 2, wherein the values Vh _i as a quotient With can be determined, where: with i = 1 to n.