JPS6231247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to improve combustion in fuel combustion, the present invention eliminates the combustion limitations of the so-called two-stage combustion method, and employs two-stage combustion, which is extremely effective in suppressing nitrogen oxides and soot. The present invention relates to a gasification combustion device equipped with a reduction chamber made of refractory materials that makes it possible to achieve this.

Nitrogen oxide NOx is generated by (1) oxidation of nitrogen in the air (Thermal NOx) and (2) oxidation of nitrogen in fuel by combustion (Fuel NOx).
Two factors are generally known for NOx),
Recent research shows that (3) ammonia (NH ₃ ) generated during the primary combustion in a reducing atmosphere, such as in the case of two-stage combustion;
The causes of oxidation of intermediate products such as cyanide (CN) ₂ during secondary combustion (Combastion NOx) have been clarified.

As an effective method for reducing NOx from such a generation mechanism, a two-stage combustion method is used, for example, in large power generation boilers.

However, in this type of two-stage combustion method, one
The smaller the amount of secondary air, the greater the effect of suppressing nitrogen oxides, but the oxygen concentration in the primary combustion area decreases, the combustion temperature in that area decreases, and the mixing of fuel and air deteriorates, resulting in worsening of combustion. Since there are constraints from the combustion perspective, such as an increase in unburned matter and a significant increase in soot and dust, it was necessary to loosen the nitrogen oxide suppression effect to some extent.

In addition, in the conventional two-stage combustion method, due to the aforementioned combustion constraints, it is not possible to place the secondary air injection position sufficiently far from the primary combustion flame. However, even if the secondary air injection position can be moved sufficiently far from the primary combustion flame, Even if the reducing atmosphere is sufficient and has a sufficient fuel NOx suppression effect, the Combastiom described above
Because there is no consideration for NOx, nitrogen oxides generated in the secondary combustion zone are not sufficiently suppressed, resulting in extremely low levels of nitrogen oxides.
This was insufficient for NOx conversion.

For this reason, measures have been taken to prevent deterioration of combustion, such as enlarging the combustion chamber and installing dust collectors to prevent soot and dust, but conventional combustors are simply equipped with second-stage air holes. It has only been partially remodeled.

As described above, in the conventional two-stage combustion method, due to the social demand for emergency measures to suppress nitrogen oxides, a certain degree of deterioration in combustion and a decrease in efficiency cannot be avoided. However, while the importance of saving energy consumption cannot be overstated, improving thermal efficiency has also become an even more important issue.

According to the present invention, there is provided a gasification combustion apparatus equipped with a reduction chamber made of refractory materials that improves the drawbacks of the conventional two-stage combustion method and performs the most ideal two-stage combustion. This method significantly reduces nitrogen oxides, suppresses soot and dust, does not deteriorate combustion efficiency compared to normal combustion methods, and also enables high-load combustion.

In other words, fuel and primary air below the stoichiometric air amount, or primary air and inert gas (including combustion gas).
Good catalytic mixing of fuel and air is achieved by performing the primary combustion using a mixed gas in the pre-combustion chamber of a known high-load combustor covered with a refractory material that can raise the combustion temperature sufficiently even in a normal burner or in the absence of air. In addition, the combustion temperature is raised by radiant heat radiation from the inner wall of the pre-combustion chamber made of refractory material, and unburned fuel due to lack of air is gasified. Since there are no constraints on the combustion surface in the secondary combustion zone, the amount of nitrogen oxides produced is reduced by lowering the oxygen concentration in order to further reduce the amount of primary air using the conventional method.

In addition, according to this invention, Thermal NOx, Fuel NOx, ammonia (NH ₃ ), cyanide (CN) 2, etc. generated in the primary combustion area are reduced by a reduction chamber made of refractory material installed behind the primary combustion _area . The reduction of intermediate products into nitrogen molecules _N2 makes it possible to suppress nitrogen oxides in the secondary combustion zone.

In addition, for complete combustion of the fuel in the secondary combustion zone, a mixing mechanism is provided near the secondary air port of the reduction chamber of the gasification combustion device in which the reduction chamber made of the refractory material of the present invention is interposed. This will result in more complete combustion and significantly reduce soot and dust.

The present invention will be explained below with reference to examples shown in the accompanying drawings.

In FIG. 1, primary air below the theoretical air amount or a mixture of primary air and inert gas (including combustion gas) flows into the wind box B from the duct 4, passes through the swirl vane 8, and the primary air port 5. It is supplied to a pre-combustion chamber 7 formed of refractory material A with a concave curved surface. On the other hand, fuel is sprayed from the burner 1 into the pre-combustion chamber 7, mixed with the primary air, etc., and combusted.The flame is stabilized by the flame stabilizer 2 attached to the burner 1, and becomes a primary combustion flame 8. . Unburnt fuel produced due to lack of air during the primary combustion inside the pre-combustion chamber 7 is transferred to a part of the combustion gas produced by the primary combustion along the concave curved surface of the inner wall of the pre-combustion chamber in the fuel injection direction. The inverted combustion gas flow 8' flowing in the opposite direction as shown by the arrow is drawn into the primary air port 5 to promote the mixing of gas and fuel and preheat, and the radiant heat radiation of the refractory material A forming the pre-combustion chamber 7 Gasify.

The combustion gas 10 containing the gasified fuel in the pre-combustion chamber 7 is passed through a gas outlet 7' narrowed by constricting the rear circumferential wall of the pre-combustion chamber to a reduction chamber C made of a refractory material 9, where nitrogen oxides are reduced. A mixing mechanism such as an orifice, ie, a structure 11 having a mixing function, is provided at the outlet 9' of the reduction chamber, and a structure 11 is provided at the downstream peripheral wall of the reduction chamber C.
The secondary air supplied through the secondary air port 6 or the mixed gas of the secondary air and the inert gas (including combustion gas) is promoted to complete combustion in the main combustion chamber D.

Further, as the mixing mechanism, various types other than the orifice type can be considered. That is, orifice barrier plates 11, 12 and 11,1 shown in barrier plates 14, 2 and 3 shown in FIG.
Examples such as the secondary air swirl blowing method shown in 3, 4, and 5 are the most practical and effective, but other suitable mixing means may also be used.

When practicing the present invention, firebricks may be used as the refractory material.

As is clear from the above description, according to the present invention, a reduction chamber made of refractory material is provided between the pre-combustion chamber and the main combustion chamber, and two
Since the secondary air port is provided, this reduction chamber promotes the reduction of nitrogen oxides in the primary combustion zone, and complete combustion occurs in the main combustion chamber downstream of it, suppressing the generation of nitrogen oxides. Oxides and dust can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing a specific example of the mixing mechanism. 1 is a burner, 2 is a flame stabilizer, 3 is a swirl vane, 4 is a primary air duct, 5 is a primary air port, 6 is a secondary air port, 7 is a pre-combustion chamber, 8 is a primary combustion flame, 8 ' is the inverted combustion gas, 9 is the refractory material, 9' is the reduction chamber outlet, 10
is gasified unburnt material, 11, 12, 13, 14, 1
6 is the mixing mechanism, A is the refractory material, B is the wind box, C is the reduction chamber, and D is the main combustion chamber.

Claims (1)

[Claims] 1. In a two-stage fuel combustion device, combustion is performed in an atmosphere of primary air or a mixed gas of primary air and inert gas (including combustion gas) below the stoichiometric air amount, and 1.
A reduction chamber made of refractory material is provided between the upstream pre-combustion chamber and the main combustion chamber where the rear peripheral wall for subsequent combustion is narrowed, and a secondary air port is provided on the downstream peripheral wall of the reduction chamber. A gasification combustion device with a reduction chamber made of refractory materials.