JPH07243611A - Method and apparatus for burning finely ground coal - Google Patents

Abstract

PURPOSE:To reduce NOx and non-burned fractions produced following the lowering of oxygen partial pressure by forming an oil flame by an oil burner in a coal flame, and burning the oil burner with excess fuel to brine the interior of the coal flame into a high temperature reducing atmosphere. CONSTITUTION:In the case where the amount of supply coal to a burner to be ignited is too little compared with the amount of supply air when a finely- grounded coal burner is ignited anew upon starting a boiler furnace, burning is achieved by an oil burner 28, and excess air existent in the vicinity of a finely-grounded coal burner flame is consumed to eliminate the state of excess air into a high temperature reducing atmosphere, whereby the amount of production of NOx is reduced and the burning is promoted for reduction of non-burned fractions. A coal fine grinder is started and the finely-grounded coal burner is ignited. Finely-grounded coal is carried and supplied with air of a necessary amount or more to the finely-grounded burner to burn an oil fuel in response to the excess air fraction. Hereby, oxygen partial pressure is lowered so that production of NOx is reduced by making use of promotion of initial burning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulverized coal combustion device,
Especially when starting a boiler furnace, etc., a low NO that is suitable for reducing the production of nitrogen oxides (NOx) in the combustion exhaust gas.
TECHNICAL FIELD The present invention relates to an x combustion method and an apparatus for implementing the same.

[0002]

2. Description of the Related Art In the operation of a conventional boiler furnace, the N in the combustion exhaust gas is temporarily or continuously changed due to changes in operating conditions and changes in fuel properties due to changes in boiler load.
The Ox value may exceed the regulation value. For this reason, it is extremely difficult to maintain the NOx value in the combustion exhaust gas below the regulation value even if low NOx combustion is performed using the two-stage combustion method or an ultra-low NOx combustion burner. In particular, when starting up the boiler furnace, NOx is easily generated because the combustion of the pulverized coal burner causes excess air, and the problem that the NOx value in the exhaust gas exceeds the regulation value often occurs. As a conventional technique, for example, as a pulverized coal burning burner that mixes combustion exhaust gas with the pulverized coal jet of the pulverized coal burner to reduce the oxygen partial pressure in the pulverized coal combustion region to suppress the generation of NOx, for example, actual development Sho-56- No. 52111 is cited.

[0003]

As described above, in the conventional pulverized coal combustion apparatus, the NOx value contained in the exhaust gas varies depending on the operating conditions due to the fluctuation of the load of the boiler furnace or the like, or the change of the fuel property or the like. Often exceeds the regulation value, and when starting up the boiler furnace, NOx is easily generated because the combustion of the pulverized coal burner causes excess air, and there is a problem that the NOx value in the exhaust gas exceeds the regulation value. It was

The object of the present invention is to solve the above problems in the prior art, and is effective even when there are changes in the combustion conditions of pulverized coal, the properties of fuel, etc., and when the boiler furnace is started. An object of the present invention is to provide a low NOx combustion method for pulverized coal, which can eliminate an excessive air state to reduce NOx and reduce unburned content by promoting combustion, and an apparatus for implementing the method.

[0005]

In order to achieve the above object of the present invention, in the low NOx combustion method for pulverized coal of the present invention, the amount of combustion air supplied to the pulverized coal burners (plurality) is adjusted. A control means is provided for dividing the fuel amount into coal which is the main fuel and oil which is the auxiliary fuel and charging the same to perform coaxial combustion. That is, inside the coal flame, an oil flame is formed by an oil burner equipped in almost the center of the pulverized coal burner, and the oil burner is controlled in excess of fuel to control the oil flame to form an oil flame in the center of the coal flame. In order to reduce the NOx by strengthening the high temperature reduction region by, the combustion is promoted to reduce the unburned component. The low NOx combustion method of the present invention includes a pulverized coal burner that uses pulverized coal as a main fuel and an oil burner that uses oil as an auxiliary fuel, and forms an oil flame by the oil burner inside the coal flame of the pulverized coal burner. Using a pulverized coal combustor having a structure to make the oil burner fuel overcombustion control, the inside of the coal flame is made into a high-temperature reducing atmosphere, and suppression of the generation of nitrogen oxides due to a decrease in oxygen partial pressure and A low NOx combustion method for pulverized coal that reduces unburned components by promoting combustion. When the pulverized coal burner is started or when the pulverized coal burner is operated at a low load, the amount of primary combustion air in the pulverized coal supplied to the pulverized coal burner is excessive. It will be done at the time. A low-NOx combustion apparatus for pulverized coal of the present invention includes a pulverized coal burner having a pulverized coal supply pipe for supplying pulverized coal conveyed from a pulverized coal machine (mill) together with primary combustion air to a furnace for combustion. The pulverized coal burner has a structure for coaxially controlling combustion of the pulverized coal and the oil by disposing an oil burner provided in the same air register as an auxiliary fuel in the center of the pulverized coal burner. A means for forming an oil flame inside the coal flame is provided by dividing the amount of fuel corresponding to the amount of combustion air supplied to each of the pulverized coal, which is the main fuel, and the oil, which is the auxiliary fuel, and controlling the supply. It is a thing. Then, a control means for burning the oil according to the excess amount of the primary combustion air of the pulverized coal flow supplied to the pulverized coal burner is provided. With such a structure, NOx can be reduced by reducing the oxygen partial pressure in the pulverized coal combustion region, and unburned components can be effectively reduced by promoting combustion by the oil burner.

[0006]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 2 is a schematic diagram showing an air and exhaust gas control system in a pulverized coal burning boiler furnace for carrying out the low NOx combustion method of the present invention. Here, a method of controlling the boiler furnace 1 during normal load operation will be described. In the figure, the combustion air is heated from the forced draft fan (FDF) 2 by exchanging heat with the exhaust gas in the air heater 5, and distributed and supplied to each pulverized coal burner (not shown) and each after-air port (not shown). It That is, the wind box inlet dampers 11 and 12
After the flow rate is controlled by, the gas flows into the burner wind boxes 7 and 8 and is supplied to each burner. Also,
The fuel coal is pulverized by the pulverized coal pulverizers (mills) 21 and 22, and is fed from the primary air fan (PAF) 15 to the air heater 5
Is adjusted to a predetermined temperature through the primary air whose flow rate is controlled by the primary air inlet dampers 19 and 20 of the mill, and is conveyed to the burners by air flow. Further, two-stage combustion is performed by the air supplied from the after-air ports (AAP) 9 and 10 to reduce NOx and unburned components in the exhaust gas. And the exhaust gas recirculation fan (GR
F) 4 is provided with an exhaust gas recirculation damper 23 to the hopper for controlling the temperature of steam supplied from the furnace outlet and for reducing NOx. Note that the exhaust gas discharged from the furnace 1 is attracted by the induction fan (IDF) 3, is balanced with the combustion air, and is discharged from the chimney 6. In the above configuration, in the embodiment of the present invention, when the pulverized coal burner is newly ignited, such as at the time of starting the boiler furnace, when the coal supply amount for the ignited burner is too small with respect to the air supply amount, Oil burner 28 shown in FIG.
Burns and consumes excess air in the vicinity of the pulverized coal burner flame to eliminate excess air and create a high-temperature reducing atmosphere to reduce the amount of NOx produced and promote combustion to promote unburned combustion. This is a low NOx combustion method that aims to reduce the energy consumption. Then, as shown in FIG. 2, when the mill 21 or the mill 22 is activated and the pulverized coal burner is ignited, the pulverized coal may be conveyed and supplied to the pulverized coal burner by more than necessary primary air. In this case, the excess air is consumed by burning the oil fuel according to the excess air content, and the oxygen partial pressure is reduced by this, so that the production of NOx is reduced, and at the same time, the unburned content due to the promotion of the initial combustion is reduced. Can be reduced.

[0007]

EFFECTS OF THE INVENTION According to the low NOx combustion method for pulverized coal of the present invention, the pulverized coal flame is turned into a high-temperature reducing flame by charging oil fuel in accordance with the excess air amount corresponding to the combustion air supply amount. Since it can be controlled freely, when starting the boiler furnace,
Or NO due to changes in combustion conditions due to changes in load
Even when x increases, the amount of NOx generated can be effectively reduced, and the unburned content can be reduced by promoting combustion. Further, when the method of the present invention is carried out, it is possible to carry out the operation only by installing or modifying the control device without requiring a large modification of the combustion equipment, which is extremely economical.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a pulverized coal burner exemplified in an example of the present invention.

FIG. 2 is a schematic diagram showing a control system for combustion air and exhaust gas of the boiler furnace illustrated in the embodiment of the present invention.

[Explanation of symbols]

1 ... Boiler furnace 2 ... FDF (pushing blower) 3 ... IDF (induction draft fan) 4 ... GRF (exhaust gas recirculation fan) 5 ... Air heater 6 ... Chimney 7, 8 ... Burner wind box 9, 10 ... After air port (AAP) ) Windbox 11, 12, 13, 14 ... Windbox inlet damper 15 ... Primary air fan (PAF) 16 ... PAF outlet damper 17 ... Cold air damper 18 ... Hot air damper 19, 20 ... Mill primary air inlet damper 21, 22 ... Mill (coal pulverizer) 23 ... Exhaust gas recirculation damper to hopper 24, 25 ... Oil pipe 26 ... Coal flame 27 ... Oil flame 28 ... Oil burner 29 ... Air register 30 ... Furnace water wall

Claims (5)

[Claims] 1. A fine powder having a structure in which a pulverized coal burner using pulverized coal as a main fuel and an oil burner using oil as an auxiliary fuel are provided, and an oil flame is formed by the oil burner inside the coal flame of the pulverized coal burner. By using a charcoal combustor to control the fuel burner of the oil burner in excess of fuel, a high-temperature reducing atmosphere is created inside the coal flame, and the generation of nitrogen oxides due to the decrease in oxygen partial pressure is suppressed and combustion is promoted. A low-NOx combustion method for pulverized coal, characterized by reducing unburned components. 2. The low N of pulverized coal according to claim 1, wherein the fuel excess combustion control of the oil burner is at the time of excessive supply of combustion air at the startup of the pulverized coal burner.
Ox combustion method. 3. A low NOx combustion method for pulverized coal according to claim 1, characterized in that the timing for controlling the fuel excess combustion of the oil burner is during the excessive supply of combustion air during the low load operation of the pulverized coal burner. . 4. A pulverized coal burner having a pulverized coal supply pipe for supplying pulverized coal conveyed from a pulverized coal machine together with air for primary combustion to a furnace for combustion, and a pulverized coal burner at a substantially central portion,
An oil burner that uses oil as an auxiliary fuel installed in the same air register is provided, and the structure is such that the pulverized coal and oil are coaxially burned, and the amount of combustion air supplied to the pulverized coal burner is set. A low NOx combustion device for pulverized coal, characterized in that means for controlling the supply of the pulverized coal as a main fuel and oil as an auxiliary fuel are separately provided. 5. A low pulverized coal low-valued coal product according to claim 4, wherein an oil combustion control means is provided in an amount corresponding to an excess of primary combustion air of the pulverized coal flow supplied to the pulverized coal burner. NO
x Combustion device.