JP3160433B2 - Steel ball dusting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing dust from a steel ball, which is applied to, for example, a gas-gas heat exchanger installed before and after an exhaust gas desulfurization unit of a coal-fired boiler.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional steel ball spraying apparatus. The steel balls transported by the steel ball transporter (1) to the steel ball tank (2) are sent to the steel ball disperser (3) above the heat exchanger (4). Dozens of ducts (7) leading to divided areas are connected to the steel ball dispersing machine (3) according to the constituent bundles of the heat exchanger (4). Then, when the rotating chute (3a) in the disperser (3) is connected to these ducts (7), the steel balls are sent to the corresponding dust removal area of the heat exchanger and incorporated in the bundle (5). The dust that collides with the heat transfer surface of the heat transfer tube that is attached is dropped. Therefore, a certain amount of steel balls is periodically sprayed in each section of the heat exchanger (4) for a certain period of time. The scattered steel balls pass through the heat exchanger and fall while removing dust, and from below, pass through the dust separator (6) and pass through the steel ball transporter (1).
Is sent to the lower chute and circulates.

[0003]

The dust adhering to the heat transfer surface of the heat exchanger is periodically dropped by spraying a fixed amount of steel balls. However, as the operation is continued, the dust removing effect decreases and the dust adheres. The amount may increase and eventually impair driving. The causes of the increase in the amount of dust attached include the effect of condensed SO ₃ as a dust binder, the difference in dust adhesion due to the type of coal (particle size, components, etc.) of the boiler fuel, and the dust removal ability covering the above-mentioned adhesion. Shortage,
And so on. Spraying and circulating a large amount of steel balls at all times can enhance the dust removal effect, but there are operational problems such as increased wear of the equipment and cost.

[0004]

In order to solve the above-mentioned conventional problems, the present invention provides a method for removing dust adhering to the surface of a heat transfer tube by spraying steel balls from above a bundle of a heat exchanger. Measuring gas pressures upstream and downstream of the bundle and spraying steel balls when the pressure difference exceeds a first set value
Increase when the pressure difference drops to the second set value.
The present invention proposes a method of dusting and removing steel balls, which is characterized by returning the amount of sprayed steel balls to normal operation .

[0005]

The phenomenon in which the dust removal effect is reduced and the amount of dust attached is increased can be understood by increasing the gas pressure loss of the heat exchanger (the gas pressure difference between the upstream and downstream of the bundle). Therefore, in the method of the present invention, to measure the pressure loss of the gas, whether dust removal of the heat exchanger is properly performed to determine pressure loss rises
When the value becomes higher than the first predetermined value, the amount of sprayed steel balls is increased to increase the dust removing effect. Then, it is confirmed that the pressure loss has dropped below the second predetermined value, and the spraying amount is returned to normal. This prevents dust adhering to the surface of the heat transfer tube of the heat exchanger from accumulating and enlarging, thereby hindering the operation, and continuing stable operation.

[0006]

FIG. 1 is a block diagram showing an example of a steel ball spraying apparatus for carrying out the method of the present invention. Exhaust gas sent from a boiler (not shown) is sent to a heat exchanger (4), and heat of the exhaust gas is recovered by a heat medium while passing through a heat transfer tube group (bundle) (5). Dust adheres to the fin heat transfer surfaces of the heat transfer tubes of the heat transfer tube group (5). In order to remove the dust, steel balls are sprayed on each bundle from above.

FIG. 2 is a plan view of the entire heat transfer tube group (5) of FIG. 1, illustrating the order of spraying steel balls.
The plane of the heat transfer tube group is, for example, 20 areas (one area: ^{3 to} 10 m ² )
And divide the area in the order of the number into a predetermined time (for example, 10
６０60 minutes), a predetermined amount (for example, 1000 to 2000 kg /
m ² h) of steel balls, and spray them for the required time (for example, 3 to ² ).
(0 hours).

[0008] The steel balls that have passed through the heat exchanger (4) are sent to a steel ball transporter (1) through a dust separator (6) for removing mixed or attached dust. Further, the steel balls pass through the switching valve (17) as they are, are sent to the steel ball dispersing machine (3) above the heat exchanger, and are again distributed and dispersed to each area.

As the operation continues, dust is accumulated due to a change in coal type, particularly as a boiler fuel, and the pressure loss of exhaust gas from the heat exchanger increases. In this embodiment, nozzles (9) and (10) are provided at the inlet and outlet of the bundle (5) of the heat exchanger (4), respectively, and the pressure difference is detected by the differential pressure gauge (8). When the pressure loss exceeds a first set value (for example, 50 mmAq), a steel ball stored in the steel ball tank (2) is added according to the signal, and as shown in FIG. 2000-400
0kg / m ² h) to increase dusting performance. When the pressure difference (pressure loss) of the exhaust gas drops to a second set value (for example, 45 mmAq), the operation is returned to the normal operation as shown in FIG. 3 and the standard (for example, 1000 to 2000 kg / m ² h) steel ball is scattered. I do. This switching is performed by detecting the amount of the steel ball returned to the steel ball tank (2) by the switching valve (17) in FIG. 1 and storing the steel ball in the steel ball tank (2) by weight. For this purpose, a weighing scale (12) is installed in the steel ball tank (2), the signal is received by the control panel (11), and the signal is sent to the switching valve (17) to switch automatically.

When the relationship between the thickness of the deposited dust and the pressure loss of the heat exchanger bundle is inferred, the pressure loss has a certain value (for example, 40 mmA).
q) In the following range, dust adhesion to the heat transfer tube fins is mainly enlarged, but if it exceeds a certain value (for example, 50 mmAq),
It is considered that the steel ball adheres and stays and the pressure loss rises rapidly. In this embodiment, when the pressure loss exceeds 50 mmAq, the amount of steel balls sprayed automatically increases, so that the steel balls staying between the fins together with the dust can be dropped together.

[0011]

According to the method of the present invention, it is possible to prevent the accumulation of dust adhering to the surface of the heat transfer tube of the heat exchanger to cause a trouble in the operation, and to continue the stable operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a steel ball spraying device for implementing a method of the present invention.

FIG. 2 is a plan view of the entire heat transfer tube group of FIG. 1 and illustrates the order of spraying steel balls.

FIG. 3 is a diagram showing a relationship between a pressure difference between a heat transfer tube bank entrance and a steel ball spray density.

FIG. 4 is a configuration diagram showing an example of a conventional steel ball spraying device.

[Explanation of symbols]

 (1) Steel ball transporter (2) Steel ball tank (3) Steel ball disperser (3a) Chute (4) Heat exchanger (5) Heat transfer tube group (bundle) (6) Dust separator (7) Duct (8) ) Differential pressure gauge (9), (10) Nozzle (11) Control panel (12) Weight scale (17) Switching valve

Continuation of front page (72) Inventor Haruhiko Kataoka 5007 Itozakicho, Mihara-shi, Hiroshima Mihara Works, Mitsubishi Heavy Industries, Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) F28G 1/12

Claims (1)

(57) [Claims] In a method for removing dust adhering to the surface of a heat transfer tube by spraying steel balls from above a bundle of a heat exchanger, gas pressures upstream and downstream of the bundle are measured, and a pressure difference between the upstream and downstream of the bundle is measured . When the set value is exceeded, the amount of steel ball sprayed
Increases when the pressure difference drops to the second set value.
A dusting method for spraying steel balls, wherein the method returns the amount of sprayed steel balls during operation .