JPH04283309A - Method for incinerating waste liquid containing nitrogen compound - Google Patents

Abstract

PURPOSE:To suppress generation of NOx and enable releasing exhaust gas directly to the atmosphere by a method wherein waste liquid containing an organic nitrogen compound is fed by spraying it into a cylindrical, upright incinerator from the top and burned by a burner provided halfway up the furnace. CONSTITUTION:Waste liquid evolves vapor under heat. When there is much vapor, the furnace 1 can not be charged smoothly through a spray inlet 2; therefore, the vapor is separated from the liquid and fed into the furnace 1 through a gas inlet pipe 8. A burner 6 having a lower air inlet 6a and a fuel inlet 6b is provided to the furnace 1 at an intermediate height close to or at the boundary between the upper part 3 and the lower part 4 of the furnace and a flame is ejected in the direction tangent to the inner wall of the furnace 1. The liquid or gas fed in through the spray inlet 2 or through the gas inlet 8 undergoes vaporization or decomposition at the upper part 3 heated at a high temperature by the burner 6. The gasified product of the waste liquid is mixed with flames of combustion in the lower part 4 and burnt. The waste gas produced by the incineration is what results from gasification of the waste liquid and incineration of the gas; therefore a decrease in the NOx content below a specified concentration can be achieved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for incinerating waste liquid containing organic nitrogen compounds while suppressing the amount of nitrogen oxides generated.

0002

[Prior Art] Conventionally, organic waste liquid was incinerated to remove harmless carbon dioxide.
It is discharged as O2, H2O, etc. to prevent pollution, but when waste liquid containing nitrogen compounds is incinerated, nitrogen oxides (N) are released.
Ox (NO, NO2, NO3) is generated, and the NOx concentration in the exhaust gas is 250 to 45, which is the specified concentration for fixed sources.
In order to exceed 0 ppm, a denitration device is installed after the incinerator to reduce the NOx content, and the NOx content is released into the atmosphere below the concentration stipulated in the Pollution Control Law.

0003

[Problems to be Solved by the Invention] However, since denitrification equipment reduces NOx in a large amount of gas by passing it through a catalyst, the equipment cost is high, and the activity of the catalyst decreases over time when used. Therefore, regular replacement is required, which increases operating costs, and the product cost of the plant where this is installed.
There was an inconvenience that it was expensive.

[0004] As a result of intensive study to solve the above problem, the present inventors found that N in the compound reacts with oxygen and NOx
In this case, depending on the state of the nitrogen-containing compound to be incinerated, (a) if NOx is produced by the reaction of N in the solid or liquid nitrogen-containing compound with O2, (b)
N by the reaction of N in gaseous nitrogen compounds with O2
When generating Ox, there are two ways. It is known that the rate at which N in the compound is converted to NOx is much smaller in (b) than in (a), and we believe that this can be used. Ta.

The present invention has been made based on the above idea, and uses only the incinerator to reduce NOx in the incinerator exhaust gas.
The purpose is to provide an incineration method that can reduce the concentration.

In the method of incinerating waste liquid containing nitrogen compounds according to the present invention, organic nitrogen compounds are sprayed and supplied from the top of a vertical cylindrical incinerator, and fuel is supplied to a burner installed in the middle of the incinerator in the height direction. and incinerate by introducing air.

Alternatively, the waste liquid is preheated, the generated steam is introduced into the upper part of the vertical cylindrical incinerator, and the concentrated liquid is sprayed and supplied from the top of the incinerator, and the incinerator is installed in the middle part of the incinerator in the height direction. The solution to the problem was to introduce fuel and air into the burner and burn the introduced gas and concentrate.

[0008]

[Operation] Since the method of the present invention has the above-mentioned structure, the upper part is also heated by combustion in the lower part of the incinerator, and the sprayed liquid is gasified by decomposition or vaporization, and this is ignited by the combustion flame in the lower part. It is mixed with and incinerated. Since the gasified nitrogen compounds are incinerated in this way, the amount of NOx generated in the exhaust gas is suppressed.

[0009]

[Example] Fig. 1 shows an example of a vertical incinerator (hereinafter referred to as a furnace) 1 used in the incineration method of the present invention. The situation is as follows. The upper end of this furnace 1 is formed into a cone shape, and an inlet 2 for spraying waste liquid is provided at the top. An upper air inlet 5 is provided around this inlet to introduce a small amount of air as necessary to burn part of the sprayed liquid and raise the temperature of the upper part 3 of the furnace. Near the boundary between the upper part 3 and lower part 4 of the furnace 1 above the middle in the height direction of the furnace 1, there is a lower air inlet 6a and a fuel inlet 6b.
A burner 6 having a burner 6 is provided to emit a flame tangentially to the inner wall of the furnace 1. Further, at the lower end of the furnace 1, an outlet port 7 for the burned exhaust gas is provided. Furthermore, if steam is generated by heating (preheating) waste liquid,
A gas introduction pipe 8 is provided in the upper part of the furnace 1 to separate the generated steam and inject it tangentially to the inner surface of the furnace.

[0010] In order to incinerate waste liquid using the furnace 1, the waste liquid is first heated. At this time, if steam is generated and its amount is large, it cannot be introduced smoothly if it is introduced from the spray inlet 2, so the steam and liquid are separated and the steam is introduced from the gas introduction pipe 8. . Naturally, even if the waste liquid is preheated, the gas introduction pipe 8 is not necessary if no steam is generated or the amount of steam is extremely small.

[0011] The upper part 3 of the furnace 1 is maintained at a temperature of 850°C or higher mainly by radiation, since the lower part 4 is at 1000°C or higher due to combustion in the lower part 4 of the furnace 1. The liquid introduced from the spray inlets 2 and 8 is decomposed or evaporated in the upper part 3 kept at a high temperature, and most of it is gasified. This gasified waste liquid is mixed with the combustion flame in the lower part 4 and is incinerated. In the exhaust gas generated by this incineration, the waste liquid is gasified and then incinerated, so the amount of NOx generated is small, and the NOx content in the exhaust gas can be reduced to below the specified concentration without using a denitrification device. .

In the above method, the upper part 3 of the furnace 1 is heated to 850°C.
Maintaining the concentration above this level is important for gasifying the sprayed waste liquid, and if the concentration in the lower part 4 is maintained at 1000°C or higher, the condition of 850°C or higher in the upper part 3 is maintained. However, if the temperature in the upper part 3 is about to drop below 850 degrees Celsius, if a small amount of air is introduced through the upper air inlet 5, a part of the sprayed liquid will burn and the temperature in the upper part 3 can be raised. can.

The amount of air introduced from the upper and lower air inlet ports 5 and 6a used in the above furnace is about 1.3 times the theoretical amount of air required for combustion of waste liquid and fuel.
The amount of air introduced from the upper air inlet 5 as needed is:
It is desirable that the amount of air be 30% or less of the theoretical air amount required for combustion of waste liquid. That is, combustion in the upper part 3 of the furnace is minimized.

FIG. 2 shows an example of a system for implementing the method of the present invention, and the same parts as in FIG. 1 are given the same reference numerals to simplify the explanation. In the figure, reference numeral 11 denotes a concentrator, and the steam generated in the condenser is introduced from the gas introduction pipe 8 of the furnace 1. Further, the concentrated liquid is sent to the spray inlet 2 by the pump 12 and is supplied to the furnace 1 as a spray. High-temperature gas discharged from the exhaust gas outlet 7 of the furnace 1 generates water vapor and its temperature is lowered by the waste heat boiler 13, and is discharged into the atmosphere from the exhaust stack 15 via the exhaust fan 14. The steam generated in the waste heat boiler 13 is used as a heat source for the condenser 11 and is discharged outside the system as a drain.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Example 1 Using the furnace shown in FIG. 1, a liquid containing an organic nitrogen compound was heated at 80%
It was preheated to ℃ and supplied from the spray inlet. In addition, heavy oil was used as fuel from burner 6, and air in an amount 1.3 times the theoretical air amount was introduced for incineration. As a result, the lower part 4 of the furnace was maintained at 1000°C and the upper part 3 at 850°C, and the gas discharged from the exhaust gas outlet 7 was 2600 m3/hr at 1000°C, and the NOx concentration in the gas was 75 ppm (however, O2 1
2% conversion).

Comparative Example 1 The procedure was the same as in Example 1 except that a normal incinerator was used. The temperature inside the furnace was maintained at 1000-1100℃, and the waste liquid was incinerated, but the NOx concentration in the discharged gas was 750-1100℃.
It was 00 ppm.

[0018]

Effects of the Invention As explained above, when nitrogen compounds are incinerated by the method of the present invention, they are gasified in the upper part of the furnace and mixed with the flame of the burner and combusted.
The production of NOx in the exhaust gas is suppressed and NOx in the exhaust gas is below the specified concentration, which previously required the installation of a denitrification device. The profits are extremely large.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an incinerator used in the present invention.

FIG. 2 is a diagram showing an example of a waste liquid incineration system using the incinerator of FIG. 1.

[Explanation of symbols]

1 Incinerator (furnace) 2 Spray inlet 3 Upper part of the furnace 4 Lower part of the furnace 5 Upper air inlet 6 Burner 6a　Lower air inlet 6b Fuel inlet 7 Exhaust gas outlet 8 Gas introduction pipe 11 Concentrator 12 Pump 13 Waste heat boiler 14　Exhaust fan 15 Exhaust stack

Claims (5)

[Claims] Claim 1: A waste liquid containing organic nitrogen compounds is sprayed and supplied from the top of a vertical cylindrical incinerator, and fuel and air are introduced into a burner installed in the middle of the incinerator in the height direction to perform combustion. A method for incinerating waste liquid containing nitrogen compounds. 2. The method of incinerating a waste liquid containing a nitrogen compound according to claim 1, wherein the waste liquid containing an organic nitrogen compound is preheated and then supplied to an incinerator. [Claim 3] The waste liquid containing organic nitrogen compounds is preheated, the generated steam is introduced into the upper part of the vertical cylindrical incinerator, and the concentrated liquid is sprayed and supplied from the top of the incinerator. A method for incinerating waste liquid containing nitrogen compounds, characterized by introducing fuel and air into a burner installed in the middle part in the height direction and burning the waste liquid. 4. The method of incinerating a waste liquid containing nitrogen compounds according to claim 1 or 3, wherein air is introduced and a part of the waste liquid is combusted when the waste liquid is sprayed and supplied from the top of the incinerator. 5. The waste liquid containing nitrogen compounds according to claim 1, 2, 3 or 4, wherein the lower part of the incinerator in the height direction is kept at 1000°C or higher, and the upper part is kept at 850°C or higher. Incineration method.