JPH01312315A - Mill warming control device for coal burning boiler - Google Patents

Abstract

PURPOSE:To reduce thermal impact to an impeller and hence prevent the crack and deformation of said impeller by allowing a primary air flow rate to flow little by little when starting mill warming. CONSTITUTION:When a mill warming start command is output, an ignition torch is ignited and a mill outlet damper 1 and a primary air damper are full opened. If an attempt is made to purge residual coal when a mill is brought to a halt, a cooled air damper makes opening motion for T1 seconds. After the damper is slightly open, the opening is maintained for (T2-T1). Then, the cooled air damper is controlled in automatic mode, gradually increasing the temperature to be cast into the mill. When this temperature exceeds a specified value, the warming operation is completed. Since crack or deformation in a burner impeller is attributed to thermal impact produced by drastic change in the temperature of impeller metal, thermal impact can be reduced and the generation of crack in the impeller can be also inhibited by avoiding a rapid cooled air flow when starting warming up and opening the cooled air damper slightly and passing the air little by little as described above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a millwarming control device for a coal-fired boiler suitable for reducing thermal shock of a coal burner impeller during millwarming.

[Conventional technology]

Figure 4 shows a schematic diagram of the surrounding area of a coal-fired boiler.

Coal is fed into a mill 2 from a coal feeder 1, and is pulverized into pulverized coal inside the mill 2. On the other hand, the hot air that has passed through the air heater passes through the hot air damper 3 and enters the mill 2, and the cold air passes through the cold air damper 4 and enters the mill 2.

The hot air and cold air are properly distributed and mixed in the confluence section 5, and the amount of each air is adjusted by the hot air damper 3 and the cold air damper 4 so as to maintain the mill outlet temperature at a constant value. The total amount of air is also adjusted by the hot air damper 3 and the cold air damper 4.

The coal pulverized inside the mill 2 is carried by the air that has passed through the primary air damper 6 and enters the burner 7, from where it is thrown into the furnace 8 and burned.

Incidentally, the impeller 9 is attached to the tip of the burner 7 in order to improve the combustion performance in the burner 7 and to give swirl to the combustion air.

By the way, in order to reliably and stably burn pulverized coal, it is necessary to dry the pulverized coal sufficiently.

Therefore, it is necessary to sufficiently warm up the temperature inside the mill 2 by mill warming before the coal is introduced into the mill.

As a method for this, a warming logic as shown in FIG. 3 is used. That is, first, the ignition torch 10 is ignited, the cold air damper 4 and the primary air damper 6 are opened, and the minimum flow rate of the mill 2 is ensured.

If there is any remaining coal inside the mill 2, this air carries the remaining coal to the burner 7, where it is burned by the ignition torch 10.

If the minimum flow rate in mill 2 is too low, the combustion flame will
There is a risk of backfire inside the mill 2 and an explosion of the mill 2, so it is important to ensure the minimum amount of air inside the mill 2 as fast as possible.

After securing the minimum flow rate in the mill 2, the hot air damper 3 is gradually opened to gradually increase the outlet temperature of the mill 2. When the temperature reaches the specified value or higher, mill warming is completed, and coal is fed into the mill 2 from the coal feeder. Start putting it in.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology only takes into account ensuring the minimum flow rate of the mill as quickly as possible, and does not take into account thermal shock to the burner impeller. The burner impeller of a resting mill is at about 1,200°C to 1,500°C, but in this state mill warming begins and if cold air is suddenly introduced, the impeller will crack or become deformed due to thermal shock.

An object of the present invention is to reduce this thermal shock to the impeller and prevent the impeller from cracking or deforming.

[Means for solving problems]

The above object is achieved by gradually increasing the air flow rate at the beginning of mill warming.

[For production]

When mill warming starts, the cold air damper and the primary air damper are slightly connected to gradually start flowing cold air. This allows the impeller temperature to gradually decrease and then
- By performing mill warming by raising the air flow rate to a specified level, it is possible to prevent impeller cracking during mill warming.

[Embodiments of the invention]

The system configuration around the mill is similar to that shown in FIG. 4 above.

Coal is fed from a coal feeder 1 to a mill 2 and pulverized into pulverized coal. Hot air enters from a hot air damper 3 and cold air enters from a cold air damper 4, are mixed at a confluence section 5, and enter the mill 2 through a primary air damper 6.

The pulverized coal is then dried and sent to the burner 7.

The millwarming logic used in the embodiment of the present invention is shown in FIG. Further, the movement of each damper is shown in FIG. 2 as a time chart.

When a warming start command is issued, the ignition torch is ignited and the mill outlet damper and primary air damper are fully opened. If the remaining coal barge is performed when the mill is stopped, the cold air damper opens for T1 seconds, opens slightly, and then maintains its opening for (T2-T1) seconds, as shown by the solid line in FIG.

After that, the cold air damper control (air volume side?ll1) is automatically activated to ensure a sufficient air volume that does not exceed the mill minimum flow rate. Then, hot air damper control B (mill outlet temperature control) is automatically entered, and the temperature introduced into the mill gradually increases, and when this temperature reaches a specified value or higher, warming is completed. If the remaining coal purge is not completed when the mill is stopped, as shown by the broken line in FIG. 2, the air volume control by the cold air damper is automatically activated at the same time as warming starts to ensure a specified flow rate. Then, temperature control is started using a hot air damper, and warming is completed when the mill outlet temperature exceeds a specified value.

If the air flow rate during mill warming is not ensured at a specified value or higher, there is a risk of a mill explosion when there is residual coal in the mill. Mill warming according to the present invention is only possible when there is no residual coal in the mill. becomes possible.

〔Effect of the invention〕

Cracks and deformation of the burner impeller are caused by thermal shock caused by sudden changes in the impeller metal temperature. Therefore, when starting warming, instead of flowing cold air suddenly, the cold air damper is opened slightly as in the present invention, and gradually By flowing air, thermal shock can be reduced and the occurrence of cracks in the impeller can be suppressed.

[Brief explanation of the drawing]

Figure 1 is a logic diagram of millwarming according to the present invention.
Fig. 2 is a time chart showing the operation of each damper according to the mill warming logic of the present invention, Fig. 3 is a logic diagram of mill warming according to the prior art, and Fig. 4 is the surrounding area of a coal-fired boiler in which the present invention can be implemented. FIG. 1,000,000 likes;

Claims (1)

[Claims] In a coal-fired boiler equipped with a combustion device that supplies pulverized coal crushed in a mill together with air to a burner equipped with an impeller, warming characterized by supplying a small amount of air to the impeller for a predetermined period during mill warming. Control device.