JPH03110315A - Device for preventing accumulation of ahses in flue - Google Patents

Abstract

PURPOSE:To prevent accumulation of ashes and to enable removal of the accumulated ashes in a way to cause floating of the ashes by a method wherein through discharge of compressed gas through a plurality of discharge nozzles mounted on the bottom part of a flue and pointing approximately to the flow direction of the flow of combustion gas, the flow of gas at the bottom part of the flue is accelerated. CONSTITUTION:A plurality of discharge nozzles 3 are mounted on the bottom part of a flue 1 and pointed approximately to the flow of combustion gas 2. A compressor 4 is run when the velocity of flow of the combustion gas 2 in the flue 1 is low, and through discharge of pressurized air as a jet 8 through the discharge nozzle 3, the flow of gas on the bottom part of the flue is accelerated to prevent the drop and accumulation of ashes. Or, the compressor 4 is run at intervals of a specified time, and by means of the jet 8 through the discharge nozzle 3, ashes 9 already accumulated are floated for removal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to a horizontal flue with a circular cross section that guides combustion gas to a chimney, and relates to prevention and removal of ash accumulation at the bottom of the inside of the flue. It is.

[Conventional technology]

The ash particles contained in the gas flowing in the flue will be transported along with the gas flow if the gas flow rate is 10 times or more the gravitational fall velocity, but if the gas flow rate is less than 10 times the gravitational fall velocity, the ash particles will be transported as smoke. It falls and accumulates on the road bottom.

When ash accumulates in the flue, the stability of the flow is hindered, and this is also a problem in terms of the strength of the flue.

If the gas flow velocity in the flue is high, it is possible to prevent the fall and accumulation of ash, but increasing the gas flow velocity is not economically advantageous;
In addition, in equipment such as commercial boilers, which have severe load fluctuations, it is virtually impossible to maintain a high gas flow rate at all times. It was often removed.

[Problem to be solved by the invention]

As mentioned above, in the past, the plant was shut down at regular intervals, the gas was cut off, and the inside of the flue was cleaned, but inspections and cleaning could not be carried out frequently, so it was necessary to prevent ash accumulation while the equipment was in operation.・Removal was necessary.

(Means for Solving the Problems) In order to solve the above-mentioned conventional problems, the present invention provides a flue with a circular cross section that guides combustion gas containing ash in the lateral direction. An apparatus for preventing ash accumulation in a flue is proposed, which is characterized by comprising a plurality of blow-off nozzles facing in the flow direction of the smoke and a means for feeding compressed gas to the blow-off nozzles.

[Function] In the present invention, when the gas flow velocity in the flue decreases, compressed gas is blown out from the blow-off nozzle at the bottom of the flue to accelerate the gas flow at the bottom of the flue, thereby preventing the accumulation of ash. Also, if there is already accumulated ash, it will be suspended and removed by a jet stream.

〔Example〕

FIG. 1 is a vertical cross-sectional view of a flue showing an embodiment of the present invention.
In the figure, (1) is a horizontal flue with a circular cross section, which guides combustion gas (2) containing ash to the chimney, and (3) is a plurality of blowout nozzles, which are located at the bottom of the flue (1). The combustion gas (2) is located in the direction of flow of the combustion gas (2). (4)
is a compressor, which includes a reservoir (5) and an air pipe (6).
), compressed air can be supplied to the blowing nozzle (3) through the branch pipe (7).

This embodiment is configured as described above, and when the flow velocity of the combustion gas (2) in the flue (+) is low, the compressor (
4) and blows out pressurized air as a jet (8) from the blow-off nozzle (3), thereby accelerating the gas flow at the bottom of the flue and preventing ash from falling and accumulating. Alternatively, by driving the compressor (4) at regular intervals, the jet (8) from the blowout nozzle (3) removes the ash (9) that has already accumulated.
Float and remove.

Note that when considering the removal of accumulated ash by jet flow, a flue with a circular cross section is most advantageous (rectangular cross sections require multiple rows of nozzles). Limited.

The specifications of the above blowing nozzle (3) are as follows. That is, as shown in Figure 2, the diameter of the flue is D.
In the case of ・Direction of the blowing nozzle lad≧0.0IXD ・Nozzle installation height: h = (0.02~0.1) x D・
The nozzle should be installed at an angle of θ-0 to 5 degrees (downward deviation from the flue axis direction) ・Blowout velocity from the nozzle: v = 35 to 50 m/s ・The nozzle should be installed at a pitch of 2l≦0.9XD do. The above specifications are based on the results of an experiment in which the Froude number was matched as a phase condition for ash accumulation and scattering, and it was confirmed that ash accumulation could be prevented and removed.

The above experiment conducted to confirm the effects of the present invention will be described in more detail. The experimental conditions were as follows.

- Flue diameter D: 800 degrees - Flue flow rate ■: 5 to 101 I/s - Nozzle diameter d: 4 to 20 degrees - Nozzle height h: 15 to 160 degrees - Nozzle angle θ: 0 to 10 degrees - Blowout flow rate v: 30 to 50 s/s In the experiment, V, d, h, θ, and V were variously changed within the above range, and the distance M1. (C nozzle installation is a pinch) was measured and determined. The results are shown in Figure 3 and can be summarized as follows.

・Nozzle diameter d: Almost directly proportional to l.

- Nozzle height h: When h is outside the range of 0.02D to 0.1D, l decreases dramatically.

・Nozzle angle θ: At an angle of 5 degrees or more, l decreases dramatically.

・Almost directly proportional to the blowout flow velocity v;2.

In other words, an effective range can be defined for the nozzle installation height h and the nozzle angle θ, but the larger the nozzle diameter d and blowing flow velocity V, the better the prevention of ash accumulation.
The result is that the removal range is also large. Therefore, once the nozzle diameter d and the blowing flow velocity V are determined, the nozzle can be installed with the ash accumulation prevention/removal range set to pitch 2 under those conditions.

From a practical standpoint, it is undesirable to insert a large nozzle into the flue, so for flues with a diameter of several meters, which are used in ordinary power plants, etc., d ≥ 0.01 number I or less). Regarding V, in order to eliminate the flue deposition method, a blowout flow rate of at least 2 S is required, but if the flow rate is low, the nozzle installation pitch must be shortened, and if the flow rate is too high, the nozzle installation pitch must be shortened. Since the pressure loss increases, as a practical guideline, the nozzle mounting pitch was selected as described above within a range that was approximately equal to the flue diameter. Then, the nozzle pitch l under the above conditions is defined.

〔Effect of the invention〕

In the present invention, when the gas flow rate decreases in a horizontal flue that guides combustion gas containing ash, compressed gas is ejected from the blow-off nozzle to accelerate the flow near the bottom of the flue, thereby suspending the ash. , can be transported and prevented from accumulating.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a flue showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the specifications of a nozzle, and FIG. 3 is a diagram showing experimental results confirming the effects of the present invention. 1--Flue, 2--Combustion gas, 3--Nozzle, 4--Compressor, 5--Reservoir, 6--Air pipe, 7--Branch pipe, 8--Jet stream, 9--Ash.

Claims (1)

[Claims] In a flue having a circular cross section that laterally guides combustion gas containing ash, a plurality of blow-off nozzles provided at the bottom of the flue and facing substantially in the flow direction of the combustion gas, and means for feeding compressed gas to the blow-off nozzles. A device for preventing ash accumulation in a flue, characterized by comprising: