RU2027104C1 - Method and device for low-temperature burning of gas - Google Patents

Abstract

FIELD: burning of combustible gas. SUBSTANCE: exhaust gas mixed with air is fed to burning zone and coefficient of excessive air is maintained within α = 2 to 2.5; pressure of air before its supply to burning zone is maintained within P^air= (2...3)·P $\genfrac{}{}{0ex}{}{\text{air}}{\text{cer}}$ _t., where P^air is pressure of air before burning zone and P $\genfrac{}{}{0ex}{}{\text{air}}{\text{cer}}$ _t. is specified pressure of air before this zone. EFFECT: enhanced efficiency. 3 cl, 4 dwg

Description

 The invention relates to low-temperature combustion of combustible gas in the furnaces of fuel-burning plants equipped with HMG-type blast burners, and can be used in the process of drying, heating, or thermooxidizing neutralization of foul-smelling and toxic impurities of industrial waste gases.

A known method of burning gas in furnaces equipped with serial widespread blast burners of the GMG type, operating with an excess air coefficient α close to unity (α = 1.15-1.3). The temperature of the combustion products during gas combustion with such excess air will be 1200-1300 ^о С. The specified method of gas combustion is carried out at certain air pressures in front of the burner, established by passport data. Figure 1 shows the change in the certified values of the air pressure depending on the thermal power during the combustion of combustible gas in a burner of the type HMG (for example, HMG-4) with the recommended coefficient of excess air α = 1.15-1.3.

When using HMG burner in furnaces of drying ovens, thermooxidative neutralization plants and other combustion devices intended to produce a low temperature coolant (900 ° ^C) combustion gas in the burner and combusted with low excess air (α to 1,15-1,3) and the required coolant temperature is achieved by diluting the products of combustion with atmospheric air or waste gases. This is done by feeding them outside the combustion zone at the outlet of the furnace through separate channels. The disadvantage of this method of burning gas in furnace devices to obtain a low-temperature carrier is the unreasonably high temperature in the combustion zone due to the burning of gas with small excess air.

 Closest to the proposed technical essence and the achieved effect is a method that is widely used to obtain a low-temperature coolant in drying plants. A device for implementing this method comprises a chamber furnace, a blow burner operating with a low excess of air α = 1.15 and a device for diluting combustion products.

The disadvantages of this method are:
reduction of the overhaul period for laying the furnace, since the development of high temperatures in it contributes to the destruction of the masonry;
an increase in the yield of toxic nitrogen oxides, the formation of which is largely determined by the temperature in the combustion zone; so, when combustible gas is burned with α = 1.15-1.3, the specific emission of nitrogen oxides reaches 0.55-0.6 kg / Gcal, which is comparable with the furnaces of boiler units;
the complexity and material consumption of the design, due to the fact that the furnace must be equipped with a device for diluting the combustion products with atmospheric air or waste gases, which leads to the complexity of this device and a decrease in its reliability.

 The aim of the invention is to increase the overhaul period of operation of the furnace, reducing its material consumption and reducing the yield of toxic nitrogen oxides.

 According to the proposed method, all the air (or waste gas) necessary to obtain a coolant of the required temperature (low-temperature coolant) is fed into the combustion zone through the air path of a GMG type blower burner operating with a high coefficient of excess air α = 2-2.5. At the same time, there is no need to supply additional air to dilute the combustion products.

 To implement the proposed method of gas combustion, the air pressure in front of the burner must be maintained within limits that differ from the passport data. Figure 2 shows a graph of the change in air pressure as a function of thermal power during low-temperature combustion of combustible gas in a burner with a coefficient of excess air α = 2-2.5 (I). The graph was obtained during experimental studies of the operation of the burner with α = 2.5 (II). It follows from it that the value of air pressure in the claimed method is 2-3 times greater compared to the passport.

The supply of excess air or waste gas to the combustion zone through the burner allows you to achieve the following advantages:
- reduce the temperature in the reaction zone and reduce the temperature effect on the walls of the combustion chamber, due to which the overhaul period of its operation increases by 4-5 times;
- reduce heat loss to the environment by lowering the temperature on the inner surface of the furnace enclosure;
- reduce the emission of nitrogen oxides by 1.5-2 times by reducing the combustion temperature and the residence time of gases in high-temperature zones of the furnace.

 In FIG. 3 shows a device for implementing the method of low-temperature gas combustion. The device is intended for thermo-oxidative neutralization of waste gases generated during the thermal processing of non-food meat waste in order to obtain meat and bone meal.

 Figure 4 shows the device, front view.

The device contains a blast burner type GMG 1, embrasure 2, a cylindrical furnace 3, the dimensions of which are made in compliance with the ratio
D _m / d = 2.0-2.5, where D _m is the diameter of the furnace;
d is the diameter of the embrasure of the blast burner.

 The device operates as follows.

Fuel (combustible gas) and waste gas containing foul smelling and toxic substances with an oxygen concentration of about 20% are fed into the cylindrical furnace 3 through the burner 1 and the embrasure 2. The waste gas is fed into the burner instead of the blast air in the amount necessary to obtain a temperature in the fire chamber sufficient for the complete thermal neutralization of all odorous and toxic gases. This temperature is about 850 ^C. For such temperature oxidation equivalence ratio α (waste gas) is to be α = 2,5.

 Due to the fact that an increased amount of waste gas (oxidizer) is supplied to the burner, compared to the passport data, it is intensively twisted on the twisting blades of the blast burner 1. This helps to improve the mixture formation of combustible gas and oxidizer, a more uniform distribution of local oxygen concentrations over the cross section torch, increasing the efficiency of the process of thermo-oxidative neutralization and improving the quality of combustion of combustible gas. The table shows the results of experimental studies characterizing the dependence of the efficiency of neutralization and the quality of gas burning on the coefficient of excess oxidizer when supplying waste gases to the burner. From the table it follows that with an increase in α from 1.15 to 2.5, the efficiency of neutralization increases and the quality of gas combustion improves (the chemical underburning of fuel decreases).

The waste gas supplied to the air path of the burner in excess of α = 1.0, without participating in the fuel combustion process, enters the peripheral recirculation zones. They arise at the root of the torch when the swirling gas stream exits from the embrasure 2 into the furnace 3. The efficiency of the neutralization process and the quality of fuel burnout depend on the size of the recirculation zones, and they, in turn, are determined by the ratio of the diameter of the furnace and the diameter of the embrasure. According to the research conducted by the authors, the optimal ratio of diameters lies in the range of D _m / d = 2.0-2.5. With this aspect ratio, the furnace will not actually have hydraulic resistance (the coefficient of local resistance of the furnace is close to 0), and the stability of the combustion process will be the greatest. A decrease or increase in this ratio leads to a deterioration in the quality of burnout, a chemical burnout appears, and the content of carbon monoxide in the combustion products increases.

 The stabilization of the combustion process during the operation of a blast burner with increased excess of oxidizing agent is carried out by axial recirculation of incandescent products of combustion to the root of the torch. This recirculation occurs due to the high swirl of the gas stream at the exit from the embrasure. In this case, the refractory tunnel, in contrast to the organization of the combustion process with α close to unity, does not have a stabilizing effect.

Flue gas temperature at the outlet of the furnace is about 850 ^{° C,} the concentration of chemical substances and neutralizes unburnt fuel products are zero.

 Thus, the device allows you to effectively burn toxic and foul-smelling components of waste gases, to ensure complete combustion of fuel (natural gas) and to obtain a low-temperature coolant, which is later used in the process for drying process raw materials.

Claims (3)

 METHOD FOR LOW-TEMPERATURE GAS BURNING AND DEVICE FOR ITS IMPLEMENTATION. 1. A method of low-temperature gas combustion, comprising supplying gas to a combustion zone, followed by diluting the resulting combustion products with atmospheric air, characterized in that, in order to increase operational reliability and reduce toxic combustion products, waste gas mixed with air is supplied to the combustion zone, and support the coefficient of excess air α = 2-2.5 while the air pressure before feeding it into the combustion zone is maintained within
P ⁱⁿ = (2-3) $\genfrac{}{}{0ex}{}{\text{in}}{\text{P}}$
where P ⁱⁿ - air pressure in front of the combustion zone, P $\genfrac{}{}{0ex}{}{\text{d}}{\text{P}}$ - passport air pressure in front of the combustion zone.  2. A device for low-temperature combustion of gas containing a blower, embrasure, cylindrical furnace, characterized in that the ratio of the diameter of the furnace to the diameter of the embrasure is 2.0 - 2.5.

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