JPH09168712A - Method for forming bag filter powder layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for correcting the formation of a powder layer on a filter cloth in each bag filter chamber when it deviates from a proper range and a method for detecting the abnormality of the powder layer and the filter cloth. SOLUTION: In a method for forming the powder layer of a bag filter, the inlet pressure gn and outlet pressure hn of each bag filter are measured, and the pressure loss ΔPn of a bag filter chamber is calculated. In a chamber the pressure loss of which is higher than a prescribed value, an outlet damper is actuated in the closing direction by a controller, and the flow velocity of gas accompanied by powder is reduced so that a powder layer formation velocity is decreased. In a chamber where the pressure loss is lower than a prescribed value, the outlet damper is actuated in the opening direction to increase the flow velocity of gas son that the powder layer formation velocity is increased. When the pressure loss is lower than a lower alarm value, the outlet damper is closed by judging the breakage of a filter cloth so that the outflow of untreated gas is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a bag filter powder layer used in an exhaust gas treating apparatus in a combustion furnace for waste and other fuels.

[0002]

2. Description of the Related Art FIG. As shown in FIG. 3, the untreated gas b is injected together with the powder layer forming chemical f into the chambers a1, a2, ... An of the bag filter.

The powder layer forming agent f forms a powder layer on the surface of the bag filter, and captures fine powder such as dust when the untreated gas b passes through the bag filter. Then, after passing through the bag filter, it becomes the processing gas c and exits, but it has no means for controlling the powder layer in each chamber.

That is, according to the prior art, in order to form a uniform powder layer on the filter cloth in each chamber of the bag filter, the geometrical shape of the bag filter device largely depends. The amount is not adjusted individually. Further, there is no means for determining an abnormality in the formation of the powder layer or an abnormality in the filter cloth.

[0005]

SUMMARY OF THE INVENTION According to the present invention, the geometrical shape of the bag filter device main body and the restrictions on the arrangement of peripheral ducts, etc. impede the uniform formation of the powder layer on the filter cloth, or somehow. An object of the present invention is to provide a method for correcting the powder layer on the filter cloth in each chamber when it is out of an appropriate range for the reason, and a method for detecting an abnormality in the powder layer or the filter cloth.

[0006]

A bag filter powder layer forming method according to the present invention comprises an outlet damper for opening and closing the outlet of each bag filter chamber, a controller for operating the outlet damper, and an inlet of the bag filter. In a device having means for calculating a pressure loss from the pressure and the outlet pressure, (A) measuring the inlet pressure and the outlet pressure of each bag filter, and (B) calculating the pressure loss of the bag filter chamber from the measured value of the pressure. Then
(C) In a chamber in which the pressure loss is larger than a predetermined value, the outlet damper is operated in the closing direction by the controller to reduce the flow velocity of the gas entraining the powder, thereby slowing the powder layer forming speed. (D) In the chamber where the pressure loss is smaller than a predetermined value, the outlet damper is operated in the opening direction,
By increasing the gas flow velocity, the powder layer forming speed is increased, and (E) If the pressure loss becomes smaller than the low alarm value, consider that the filter cloth is damaged and close the outlet damper. This prevents the untreated gas from flowing out.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS.
Shown in FIG. 1 is a diagram showing a control flow of an embodiment of the present invention, and FIG. 2 is a diagram showing a method of the present invention.

In the method of the present invention, as shown in FIGS. 1 and 2, a controller e for receiving the differential pressure signals of the chambers a1 ', a2', ... An 'and operating the outlet dampers d1, d2 ,.
Use equipment equipped with 1, e2, ... en.

The differential pressure of the bag filter is not always controlled to be constant for each chamber, but the maximum differential pressure (ΔPma).
x) or the differential pressure immediately before backwashing is controlled (FIG. 1 (B)).
Three types of pressure are set: maximum pressure loss PMAX, minimum pressure loss Pmin, filter cloth abnormal pressure loss Pemg.

At the same time, the differential pressure adjusting means (Pressvive
Differernce, Control Alarm, also referred to as PdCA below)
To issue a high alarm and a low alarm. That is, the method of the present invention is provided with means for detecting the static pressure at the inlet and the outlet of each bag filter chamber, and adjusts the opening of each chamber so that the static pressure difference (pressure loss) in each chamber falls within a predetermined control range. Provide a possible exit damper. The predetermined static pressure difference is, for example, a function of the elapsed time after backwashing.

[0011]

Since the method of the present invention is configured as described above, it has the following effects. (1) By the method of the present invention, a powder layer can be uniformly formed in each chamber of the bag filter.

Therefore, it is possible to prevent the outflow of the untreated gas from the filter cloth, or the outflow of the insufficiently treated gas, and to effectively perform the exhaust gas treatment with a low pressure loss as the entire bag filter device.

Therefore, the entire surface of the filter cloth can be effectively used. (2) Further, it is possible to detect the abnormality of the powder layer and the filter cloth based on the abnormality of the pressure loss, recover the abnormality of the device, or take an emergency measure.

[Brief description of the drawings]

FIG. 1 is a control flow diagram according to an embodiment of the present invention.

FIG. 2 is a diagram showing an apparatus used in the method of the present invention.

FIG. 3 is a diagram showing a conventional technique.

[Explanation of symbols]

a ... bag filter room, an ... nth bag filter room (n = 1, 2, ...
n), b ... untreated gas, c ... treated gas, d ... bag damper outlet damper, dn ... nth bag filter outlet damper (n =
1, 2, ... N), e ... Controller of outlet damper of bag filter chamber, en ... Controller of outlet damper of nth bag filter chamber (n = 1, 2, ... N), f ... Powder Layer forming agent, g ... inlet pressure of bag filter chamber, gn ... inlet pressure of nth bag filter chamber (n = 1,
2, ... N), h ... Outlet pressure of bag filter chamber, hn ... Outlet pressure of nth bag filter chamber (n = 1,
2, ... n), ΔP ... differential pressure in bag filter chamber, ΔPn ... differential pressure in nth bag filter chamber (n = 1,
2, ... N), PdCA ... Differential pressure adjustment alarm.

Claims (1)

[Claims] 1. An outlet damper (dn) for opening and closing the outlet of each bag filter chamber, a controller (en) for operating the outlet damper, and means for calculating a pressure loss from the inlet pressure and the outlet pressure of the bag filter. In the device having (A) the inlet pressure (gn) and outlet pressure (hn) of each bag filter are measured, and (B) from the measured values (gn, hn) of the pressure,
Calculate the pressure loss (ΔPn) in the bag filter chamber and (C)
In the chamber where the pressure loss (ΔPn) is larger than a predetermined value, the controller (en) operates the outlet damper (dn) in the closing direction to reduce the flow rate of the gas entrained with the powder. In the chamber in which the layer formation speed is slowed and (D) the pressure loss (ΔPn) is smaller than a predetermined value, the outlet damper (dn) is operated in the opening direction to increase the gas flow rate, thereby reducing the powder. When the layer formation speed is increased and (E) the pressure loss (ΔPn) becomes smaller than the low alarm value, it is considered that the filter cloth is broken, and the outlet damper (dn) is closed to remove untreated gas. A method for forming a bag filter powder layer, characterized in that the outflow of (b) is prevented.