JPS6234089Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a fluidized bed combustion device, and more specifically to a combustion device such as a fluidized bed boiler that is equipped with a control mechanism that controls primary air and secondary air in relation to increases and decreases in boiler load. It is.

A conventional fluidized bed boiler, as shown in Figure 1,
It has a furnace 1, a fluidized bed 2 provided below the furnace 1, and a plurality of secondary air blowing holes 4 provided sequentially in the vertical direction on the fluidized bed upper side wall (water wall) 3 of the furnace 1. Coal A is fed into the fluidized bed 2 inside the furnace 1 via the coal feed pipe 5 leading into the furnace 1 from below the furnace 1, and comes into contact with the primary air B blown through the wind box 6 at the bottom of the furnace. , most of it, for example 90%, is combusted in the fluidized bed 2 to heat the water in the intrabed heat exchanger tubes 7. The unburned coal moves from the fluidized bed 2 to the upper part of the furnace 1 together with the combustion gas, is burned by the secondary air C blown in from the secondary air blowing hole 4, and is transferred to the boiler drum 8 together with the combustion gas from the primary air B. water wall 3
After heating the water inside, it is discharged as exhaust gas D. The amount of primary air B is determined so that the ratio of the amount of primary air to the amount of coal feed (air ratio in the bed) is an appropriate value in order to reduce the generation of nitrogen oxides (NO _x ) in the fluidized bed 2. The primary air flow rate is adjusted by the primary air flow rate adjustment valve 9. In addition, each secondary air blowing hole 4 is designed to achieve an oxygen partial pressure distribution suitable for burning unburned coal while suppressing the generation of _NOx above the fluidized bed 2.
Secondary air blowing position adjustment valve 10 provided for each
The amount of air blown is adjusted accordingly.

However, in such conventional fluidized bed boilers, the air ratio in the bed was fixed even when the boiler load changed, so if the amount of coal feed was reduced in order to lower the boiler load, The amount of primary air also decreases proportionally, which lowers the combustion efficiency of coal.On the other hand, if you try to increase the amount of primary air to improve combustion efficiency, the temperature within the fluidized bed will locally rise, causing a drop in the exhaust gas. The disadvantage was that the _NO

The purpose of the present invention is to eliminate these drawbacks of the conventional technology, and to provide a fluidized bed combustion system that suppresses the amount of _NOx generated even when the boiler load decreases, and prevents a decrease in combustion efficiency due to a decrease in fluidized bed temperature. Our goal is to provide the following.

In order to achieve the above object, the present invention provides a fluidized bed in which coal sent into a furnace is combusted by primary air, and a secondary air blower in which unburned coal is combusted in an empty column above the fluidized bed. In a fluidized bed combustion apparatus equipped with holes, the amount of primary air is increased in response to a decrease in the temperature of the fluidized bed at low loads, and the increase in nitrogen oxides due to the increase in primary air leads to the reduction of _NOx due to the decrease in temperature of the fluidized bed. If the efficiency is exceeded, the blowing position and blowing rate of the secondary air blowing hole in the empty column _are
The present invention is characterized by the provision of a control mechanism that adjusts the oxygen partial pressure to an appropriate level for reduction.

In this design, if the amount of coal feed is reduced to reduce the boiler load, the temperature of the fluidized bed will drop, so the primary air amount is controlled to increase in conjunction with the temperature of the fluidized bed, and the air ratio in the bed is controlled. By increasing the oxygen partial pressure, the combustion efficiency within the bed is increased and the temperature within the fluidized bed is increased. On the other hand, as the temperature inside the fluidized bed increases, _{the NOx} concentration in the exhaust gas tends _to increase. The mixing ratio of secondary air above the fluidized bed and its injection position are controlled. The secondary air blowing position refers to the position above the fluidized bed where the secondary air is blown and mixed, and is controlled by selecting the position of the secondary air blowing hole or adjusting the blowing angle. Specifically, by increasing the amount of primary air,
_{When the NO ​} control with a difference in

This invention will be explained in more detail below using examples.

FIG. 1 is a system diagram showing an embodiment of the fluidized bed boiler of the present invention. In this fluidized bed boiler,
Coal A fed into the furnace 1 from the coal feed pipe 5 is first combusted in the fluidized bed 2 by the primary air B, then unburned coal moves above the fluidized bed 2 together with the combustion gas and is combusted by the secondary air C. The point that the exhaust gas D is discharged is the same as the conventional fluidized bed boiler described above, but in the fluidized bed boiler of this invention, a bed temperature detection end 11 is provided in the fluidized bed 2, and this detection end is connected to the primary air amount regulating valve 9 via a layer temperature signal transmitter 12 and a valve controller 13. Further, a _NOx detection end 14 is provided in the flue through which the exhaust gas D is discharged, and is connected to each secondary air blowing position adjusting valve 10 via a _NOx signal transmitter 15 and a valve controller 16. In such a fluidized bed boiler, in order to reduce the boiler load, the amount of coal fed is reduced and the
Even if the temperature of the fluidized bed 2 decreases, the primary air amount adjustment valve 9 is opened due to the cooperation between the bed temperature detection end 11, the bed temperature signal transmitter 12, and the valve controller 13, and the air ratio in the bed remains high. This increases coal combustion efficiency and maintains an appropriate bed temperature. Also, due to this kind of control, when the _NOx concentration in the exhaust gas becomes high,
Due to the cooperation between _the NO _X detection end 14, the _NO Then, the opening degree of each secondary air blowing position adjusting valve 10 is adjusted and air is blown into the secondary air blowing position adjusting valve 10. When the intralayer air ratio is increased in this way,
Even if the amount of _NOx generated increases, it can be suppressed in the empty column by changing the position and amount of secondary air blowing.

FIG. 2 is an apparatus system diagram showing another embodiment of the present invention. In this embodiment, there is one secondary air blowing hole 4, and the blowing angle is variable. To adjust the secondary air blowing position, _NO
4, the _NOx signal transmitter 15, and the secondary air blowing angle controller 17, the angle of the secondary air blowing hole 4 is adjusted. In this embodiment as well, the secondary air blowing position and its blowing amount can be adjusted as appropriate for reducing _NOx , and the apparatus is also simplified.

As described above, according to the present invention, even when the boiler is operated with a reduced coal feed amount, the coal combustion efficiency can be maintained at a high level by maintaining the temperature of the fluidized bed appropriately, and the _NOx concentration in the exhaust gas can be increased. can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is an equipment system diagram showing one embodiment of the fluidized bed boiler of the present invention, and FIG. 2 is an equipment system diagram showing another embodiment of the invention. 1...Furnace, 2...Fluidized bed, 3...Boiler water wall, 4...Secondary air blowing hole, 5...Coal feed pipe, 6...
...Wind box, 7...Intralayer heat exchanger tube, 8...Drum, 9...
...Primary air amount adjustment valve, 10...Secondary air blowing position adjustment valve, 11...Bed temperature detection end, 12...Bed temperature signal transmitter, 13...Valve controller, 14...NO _X detection end, 15... NO _X signal transmitter, 16... Valve controller, 17... Secondary air blowing angle controller, A... Coal, B... Primary air, C... Secondary air, D... Exhaust gas.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A fluidized bed that uses primary air to combust the coal fed into the furnace, and a secondary air blowing hole that combusts unburned coal in the empty column above the fluidized bed. In a fluidized bed combustion equipment _with A fluidized bed combustion device characterized by being provided with a control mechanism that adjusts the blowing position and blowing ratio of the secondary air blowing hole in the empty column so that the partial pressure of oxygen is appropriate for reducing _NOx when . (2) Scope of Utility Model Registration Claim Paragraph 1 states that the temperature signal detected at the temperature detection end in the fluidized bed is sent to the valve controller via the bed temperature signal transmitter so that the bed temperature becomes a predetermined value. A control mechanism that adjusts the primary air flow rate adjustment valve, and a control mechanism that detects the _NO ) or a control mechanism for adjusting the angle.