JPH0379906A - Cyclone for circulating fluidized bed boiler - Google Patents

Abstract

PURPOSE:To make it unnecessary to install a cleaning device by means of air or steam and take a measure against erosion by making variable the height of the inner cylinder that is provided at the outlet of a cyclone. CONSTITUTION:At the outlet of a cyclone 2 an inner cylinder 4 is provided so as to make variable its height. As the inner cylinder 4 is made shorter, the limit caught particle diameter of solid particles becomes larger. In the ordinary operation, the inner cylinder 4 of the cyclone 2 descends to the position of the broken line and takes the position at which the efficiency of catching of the cyclone 2 is highest, and solid particles that fly from a combustion furnace 1 are caught by the cyclone 2 and returned to the combustion furnace 1. Solid particles of smaller diameters which are not caught by the cyclone 2 gradually attach the heat transfer face 3 in the downstream. When the heat transfer efficiency of the heat transfer face 3 is lowered due to the attachment of solid particles, the inner cylinder 4 of the cyclone 2 is, for instance, raised up to the position of the solid line. Then the limit caught particle diameter of the cyclone 2 becomes larger, and when the solid particles fly to the heat transfer face 3, the particles that have attached it are removed by the particles of larger diameters and the heat transfer face 3 is cleaned. Then the inner cylinder 4 is again lowered and the operation returns to the ordinary operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cyclone for a circulating fluidized bed boiler, and more particularly to a cyclone structure that eliminates the need for a cleaning device for the heat transfer surface downstream of the boiler.

Conventional technology A conventional circulating fluidized bed boiler is illustrated in FIG.

In FIG. 3, reference numeral 1 represents a combustion furnace, 2 represents a cyclone, 3 represents a heat transfer surface, and 5 represents an air or steam cleaning device.

In such a circulating fluidized bed boiler, the combustion furnace! The solid particles that fly out are collected by the cyclone 2, but the solid particles that are not collected by the cyclone 2 adhere to the downstream heat transfer surface 3, reducing heat transfer efficiency. Conventionally,
An air or steam type cleaning device 5 is provided directly above the heat transfer surface, and air or steam is directly injected onto the heat transfer surface 3 to clean the heat transfer surface 5 and restore heat transfer efficiency.

Problems to be Solved by the Invention There is a limit to the particle size of solid particles collected by a cyclone, and particles below the limit particle size will be scattered to the heat transfer surface 3 in the wake; The small solid particles have a property of easily adhering to the heat transfer surface 3.

In order to restore the heat transfer efficiency of the heat transfer surface, which decreases due to the adhesion of solid particles to the heat transfer surface 3, an air or steam type cleaning device 5 is provided, but such a device requires large-scale equipment. In addition, it is necessary to take measures against erosion of the heat transfer surface 3 due to solid particles being drawn in by the cleaning device at a high flow rate, and furthermore, the disturbance to the control of the boiler is large.

The present invention has been made in view of the above circumstances, and has the function of a leaning device as described above, thus eliminating the need for such a leaning device, and providing benefits to erosion countermeasures and boiler control that were necessary when using a cleaning device. An object of the present invention is to provide a cyclone for a ring fluidized bed boiler that can eliminate external turbulence.

Means for Solving the Problems The present invention achieves the above object by guiding exhaust gas containing solid particles from inside a fluidized bed furnace to a cyclone, separating the solid particles from the exhaust gas, and returning the solid particles to the fluidized bed. A cyclone for a circulating fluidized bed boiler that cleans the heat transfer surface by injecting exhaust gas mixed with solid particles onto the heat transfer surface, characterized in that the height of the inner cylinder provided at the outlet of the cyclone is variable. A cyclone for a circulating fluidized bed boiler can be provided.

Normally, a cylinder is installed at the outlet of the cyclone to improve collection efficiency, but by pulling up this inner cylinder, the limit particle size for collection of the cyclone is increased, and large particles are placed in the wake of the cyclone. By scattering particles with a large diameter, small solid particles attached to the heat transfer surface are removed.

EXAMPLES Below, preferred embodiments of the present invention illustrated in FIGS. 1 and 2 will be described in detail.

FIG. 1 shows a circulating fluidized bed boiler including a cyclone according to the invention, and FIG. 2 shows the main parts of the cyclone according to the invention.

At the outlet of the normal cyclone 2, an inner cylinder 4 is installed to improve the collection efficiency by reducing the critical collection particle size of solid particles. There is a correlation between the length of the inner cylinder 4 and the limit collection particle size, and the shorter the inner cylinder 4 is, the larger the limit collection particle size becomes. In the present invention, this inner cylinder 4 is not fixed;
As shown in Figure 2, it is installed so that its height can be varied.

During normal operation, the inner cylinder 4 of the cyclone 2 is lowered to the position shown by the broken line in FIG. 2, which is the position where the cyclone 2 has the highest collection efficiency. Solid particles scattered from the combustion furnace 1 are collected by the cyclone 2 and returned to the combustion furnace 1, but small solid particles that are not collected by the cyclone 2 gradually adhere to the heat transfer surface 3 in the wake. I'm going to go.

When the heat transfer efficiency of the heat transfer surface 3 decreases due to the adhesion of solid particles, the cyclone inner cylinder 4 is temporarily raised, for example, to the position shown by the solid line in FIG.

For this reason, the critical collection particle size of cyclone 2 becomes larger,
The exhaust gas discharged from the cyclone 2 contains solid particles having a large particle size. When large-sized solid particles are scattered onto the heat transfer surface 3, the heat transfer surface 3 is cleaned due to a self-sweeping effect in which the attached particles are removed by the large-sized particles.

Once the heat transfer surface 3 is cleaned, the inner cylinder 4 is lowered again and normal operation is resumed.

Effects of the Invention In the present invention, the cyclone itself has the function of a conventional heat transfer surface cleaning device, so there is no need to install a large-scale cleaning device using air or steam.
Measures to prevent double lotion due to air or steam entraining particles at high flow rates and impinging on the heat transfer surface are no longer necessary. Moreover, the influence on control when air or steam is injected can be ignored, and the reliability of boiler operation is also improved.

[Brief Description of the Drawings] Fig. 1 is a diagram showing the configuration of a circulating fluidized bed boiler including a cyclone according to the present invention, Fig. 2 is an enlarged view showing the main parts of the cyclone according to the present invention, and Fig. 3 is a conventional diagram. FIG. 2 is a diagram showing the configuration of a circulating fluidized bed boiler. ! ... Combustion furnace, 2. Cyclone, 3. Heat transfer surface, 4.
・Inner cylinder.

Claims (1)

[Claims] Exhaust gas containing solid particles is led from inside the fluidized bed furnace to a cyclone, the solid particles are separated from the exhaust gas and returned to the fluidized bed, and the exhaust gas mixed with solid particles is injected onto the heat transfer surface for cleaning. A cyclone for a circulating fluidized bed boiler, characterized in that the height of an inner cylinder provided at an outlet of the cyclone is variable.