JPS59197712A - Nox controller for incinerator - Google Patents

Abstract

PURPOSE:To suppress the value of NOX contained in a waste gas to a defined value range in the entire region of a combustion load by controlling the bias ratio between respective burners responsive to the combustion state. CONSTITUTION:An adjusting operator 8 is set to store beforehand an NOX exhaustion defined value 9, and compares a flow quantity signal 17 from a fuel meter 15 and an NOX signal 6 from an NOX meter 4 with the NOX exhaustion defined value 9. The adjusting operator 8 further determines the bias ratio between respective burners so that the NOX value within the waste gas assumes a value which is less than the NOX exhaustion defined value 9, so as to set the opening degrees of bias ratio control valves 16a, 16b and 16c to the bias ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a NOx control device for a combustion furnace equipped with a plurality of burners.

It is important to suppress nitrogen oxides (NOx) in the waste gas from combustion furnaces used in boilers and the like as much as possible as a pollution control measure. By the way, some combustion furnaces are equipped with a plurality of burners, and the number of combustion burners is changed according to the combustion load. Conventionally, in combustion furnaces equipped with a plurality of burners, there is a method for suppressing the NOx. ,
By changing the distribution ratio, that is, the bias ratio, of the fuel supplied to each burner, a burner with a fuel-rich flame and a burner with an air-rich flame are formed, thereby suppressing the generation of NOx to below a regulation value. It is known that this NOx suppression effect changes by changing the bias ratio, but in conventional combustion furnaces, the bias ratio is fixed at the time of initial combustion adjustment of the burner. Alternatively, changes in NOx due to changes in the nitrogen (N) content in the fuel cannot be adequately addressed, leading to excessive combustion with high residual oxygen concentrations and the emission of NOx at concentrations higher than the regulation value, making it difficult to prevent pollution. There were still problems in terms of energy conservation and energy conservation measures.

The present invention solves the above-mentioned problems by using a NOx control device having the structure described in the claims.The present invention is an attempt to solve the above-mentioned problems by controlling the bias ratio between each burner according to the combustion state, thereby controlling the NOx value in the exhaust gas under the combustion load. The purpose of the present invention is to provide a combustion furnace NOx control device that can suppress NOx within the regulation value in the entire range.

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 and FIG. 2 show an example in which the present invention is applied to a combustion furnace equipped with three burners.
, 2b, 2c, the combustion furnace 1
NOx in the waste gas! A NOx meter 4 for measuring the degree of NOx and a total of 5 for measuring the degree of 02C are installed.
The NOx signal 6 and the 02 signal 7 are input to the adjustment calculator 8.

On the other hand, a fuel supply system 11 and an air supply system 12 are attached to the burner box 10 of the combustion furnace 1. The fuel supply system 11 includes an injection pump 13 and a main fuel control valve 14 . A fuel flow meter 15 is provided, and the downstream path of the flow meter 15 is branched into three, with a bias ratio control valve 1
6 a.

Burner 2a, 2b, 2c through joint venture of 16b, 16c
connected to. Then, the flow rate signal 17 of the fuel flow meter 15 is inputted to the adjustment calculator 8.
From there, bias ratio control signals 18, 19, and 20 are input to the negative ratio control valves 16a, 16b, and 16c.

The adjustment calculator 8 has the NOx emission regulation value 9 stored in advance, and receives the flow rate signal 17 from the fuel flow meter 15 and the NOx emission regulation value 9.
Compare the NOx signal 6 from the xit 4 and the NOx emission regulation value 9, and determine the bias ratio between each burner such that the NOx value in the waste gas is equal to or less than the NOx emission regulation value 9,
Bias ratio control valve 16a, 1.6b
, 16c is set to the bias ratio. Note that the neutral number 21 in Figure 1 is a chimney.

The present invention has the above configuration, in which the opening degree of the main fuel control valve 14 is adjusted according to the combustion load of the combustion furnace 1, fuel such as heavy oil is supplied from the fuel supply system 11, and the air supply system 12 is supplied with fuel such as heavy oil. Air is supplied from the combustion chamber to carry out combustion.

At this time, the fuel flow meter 15 detects the fuel flow rate flowing through the fuel supply system 11 and sends this to the adjustment calculator 8 as a flow rate signal 1.7. Still, the NOx meter 4 and the 02 meter 5 detect the NOx value and the 02 value in the waste gas flowing through the waste gas path 3, and send the values as the NOx signal 6 and the 02 signal 7 to the adjustment calculator 8.

The adjustment calculator 8, as illustrated in FIG.
One burner usage range, two burner usage range, and three burner usage range are preset according to the dog Jh of combustion load).
For example, if the fuel flow rate is in the one-burner usage range, only one burner 2b is used for combustion, and if the two-burner usage range is four fuel flows, two burners 2b and 2c are used for combustion. , burners 2a, 2b, 2 in the case of a three-burner usage area.
It is set to burn using all of c. Then, in each usage area, while comparing the NOx value detected by the NOx meter 4 and the NOx emission regulation value 9, it is determined that the NOx value in the waste gas exceeds the NOx emission regulation value 9 as described below. The bias ratio between each burner is determined so as not to exceed the bias ratio, and the opening degree of each burner is set to the bias ratio.

As an example, a method of determining the bias ratio in the case of a fuel flow rate in a three-burner usage range will be described.

The adjustment calculator 8 receives the flow rate signal 1γ from the fuel flow meter 15 and determines that the fuel flow rate is in the three burner usage range. and,
The adjustment calculator 8 is first located on the 15th floor, the bias ratio control valve 16a.

Bias ratio control signal 1 controls the opening degrees of 16b and 16c.
8, 19. Set to a pre-given reference bias ratio in the three burner usage range through 20. If the current reference bias ratio is 40 = 30:30, the bias ratio control valve 16b is set to 3 (J%HK), the bias ratio control valve 16c is set to 30% opening, and each burner 2a is opened at this bias ratio. , 2b, 2c and burns the fuel.Next, in the second stage, the opening degree of the burner 2b is fixed at the 30% opening degree, and in this state, NOx
While comparing the NOx value detected in Total 4 with the NOx emission regulation value 9, the NOx value in the waste gas is determined to be the NOx emission regulation value 9.
The bias ratios of the other burners 2a and 2c are adjusted as follows. As a result of this adjustment, burner 2a: burner 2C-
Suppose we obtain a bias ratio of 45:20. Next, in the third stage, the bias ratio of the burner 2c is fixed at the 20% opening degree obtained in the second stage, and in this state, NOx
The bias ratios of the other burners 2a and 2b are adjusted so that the NOx value in the waste gas becomes less than or equal to the NOx emission regulation value 9 while comparing the NOx value detected in step 4 with the association NOx emission regulation value 9. As a result of this adjustment, burner 2a: burner 2
Assume that a bias ratio of b=55:25 is obtained.

The adjustment calculator 8 executes the calculations up to the third stage, and uses the bias ratio obtained in the third stage, that is, the value of burner 2a:burner 2b:burner 2C=55:25:20, as the fuel flow rate at that time. (combustion load) is determined as a bias ratio between each burner that outputs NOx once below a predetermined NOx emission standard value of 9. The adjustment calculator 8 also controls a bias ratio control valve 16a that regulates the amount of slag -1 in the burner 2a.
a 55% opening signal for the burner 2b, a 25φ opening signal for the bias ratio control valve 16b that regulates the fuel amount of the burner 2b, and a 20% opening signal for the bias ratio control valve 16c that regulates the fuel amount of the burner 2c. Opening signals are sent to each burner, the bias ratio of each burner 2a, 2b, and 2c is set to the above-mentioned best ratio, and combustion is performed.

The adjustment calculator 8 executes the above-mentioned control operation every time the combustion state of the combustion furnace 1 changes, thereby automatically controlling the NOx concentration in the waste gas of the combustion furnace 1 to always be below the regulation value. It is something to do.

In addition, in the case of the fuel flow rate in the two-burner usage range d, only burners 2b and 2c are used as described above. Therefore, since the bias ratio of the two burners 2b and 2c is determined by the calculation operations up to the second stage, the calculation operations in the third stage are unnecessary. -! In addition, if the fuel flow rate is in the single burner usage range, only burner 2b is used, so in this case, burner 2b can be set to 100 degrees of opening, and there is no need to determine the bias ratio. . Fuel flow rate (combustion load) and NOx by control based on the present invention described above
The relationship between concentration and 02C degree is illustrated in FIG. In the figure,
The solid line shows the case of the present invention, and the dotted line shows the case of the conventional fixed bias ratio type. As is clear from the diagram, according to the present invention, the NoXS degree in the exhaust gas can be suppressed to below the regulation value in the entire fuel flow range, but
When using the conventional fixed bias ratio type, the bias ratio is fixedly set during initial combustion, which makes it impossible to accurately follow changes in combustion conditions, and NOx exceeding the regulation value is emitted. Furthermore, according to the present invention, since the bias ratio is controlled according to changes in the combustion state, combustion is improved, and as shown in FIG. will also become smaller.

In the above embodiment, the Oza degree in the waste gas is measured by the 02 total 5 and inputted to the adjustment calculator 8.
The reason for measuring this 02et degree is that in pollution-related matters, the NOx value based on 02 conversion is adopted as a regulation target. For example, in the case of boilers, etc., the NOx value when converting the 02 concentration in waste gas to 4 factors is subject to regulation.
The 4% equivalent NOx value is calculated by the following formula.

That is, the adjustment calculator 8 outputs the NOx signal 6 and the 02 signal 7.
The converted NOx value is immediately calculated from the above formula. Naturally, the adjustment calculator 8 can also be constituted by a microcomputer. In addition, in the case of a combustion furnace that does not adopt the NOx value based on 02 conversion, the above 02 total 5
can be considered unnecessary. In the above embodiment, the case where independent bias ratio control valves 16a, 16b, and 16C were provided was shown, but the burner 2a.

When an electromagnetic on-off valve is attached to each of 21) and 2c, the electromagnetic on-off valve can be used as a bias ratio control valve, and the above-mentioned bias ratio control valves 16a and 16b.

There is no need to specially provide 16c.

The present invention has the configuration and operation as explained below, and it is possible to automatically control the bias ratio between each burner according to the combustion state, and to control changes in the combustion of the combustion furnace and nitrogen (nitrogen) in the fuel. This has the remarkable effect of keeping the NOx concentration in the exhaust gas within the regulated value at all times against changes in N) and maintaining a good air balance within the combustion furnace, greatly contributing to pollution prevention and energy conservation. be.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of one embodiment of the present invention, Fig. 2 is a schematic enlarged view of the same burner section, and Fig. 3 is a diagram showing the exhaust NO in relation to the fuel flow rate.
It is a graph showing the relationship between x concentration and discharge 02 e degree. 1: Combustion furnace, 2a, 2b, 2c: Burner, 3: Waste gas path, 4: NOx meter, 5: 02 meter, 6: NOx signal, 7: 02 signal, 8: Adjustment calculator, 9: NOx emission standard Value, 11: Fuel supply system, 12: Air supply system, 14
: Main fuel control valve, 15: Fuel flow meter, 16a, 16b,
16c: Bias ratio 'j7 troll valve, 17: Flow rate signal, 18, 19, 20: High ass ratio control signal.

Claims (1)

[Claims] In a combustion furnace equipped with multiple burners, there is a fuel flow meter that measures the fuel flow rate supplied to the combustion furnace, and a fuel flow meter that measures the NO in the waste gas.
A NOx meter that measures x value, NOx emission regulation value stored in advance in the device, the measured fuel flow rate, and NOx
an adjustment calculator that compares the values with the values, determines a bias ratio between each burner so that the NOx value in the waste gas is equal to or less than the NOx emission regulation value, and sets the fuel flow rate ratio of each burner to the bias ratio; A NOx control device for a combustion furnace, characterized in that it is provided with: