CN101338356B - A heat treatment furnace using a porous media burner - Google Patents

Abstract

A heat treatment furnace using a porous medium burner belongs to the technical field of heat treatment furnaces, and the furnace includes a furnace body and a burner. The burner is made of porous ceramic foam, and the burner is arranged on the top of the furnace or on the side wall. The masonry around the burner outlet section is designed in the shape of a gradually expanding bell mouth. The intersection of the extension surfaces of the two adjacent burner outlet sections or the burner The intersection line between the extension surface of the outlet section and the furnace wall is located above the workpiece to be heated. The heat loss of the furnace wall is small in this arrangement, and the radiation heat transfer share is large. The ceramic material of the burner is cordierite, yttria-based zirconia, calcium oxide-based zirconia, silicon nitride, aluminum oxide, or ceramic particles bonded by a binder. A burner is composed of one or more identical combustion units. The porous media burner of the present invention has the advantages of small volume, low manufacturing cost, low installation difficulty, large adjustment ratio, high combustion intensity and low pollutant emission. The heat treatment furnace has high combustion efficiency, less heat loss and high heating quality.

Description

A heat treatment furnace using a porous media burner

technical field

The invention belongs to the technical field of heat treatment furnaces, and relates to an industrial heat treatment furnace, in particular to a heat treatment furnace using a porous medium burner.

Background technique

The heat treatment furnace is the basic equipment in the heat treatment workshop of metallurgical factories and machinery manufacturing plants. It is the last process in the process of metallurgy and machining. So far, heat treatment furnaces generally use traditional burners, and the combustion method is mainly diffusion combustion or premixed combustion. The combustion process is completed in the free space of the furnace, and the combustion heat analysis is mainly transmitted to the workpiece by the flame or high-temperature flue gas through radiation and convection; the heat directly transmitted to the workpiece by flame radiation only accounts for a few percent, and most of the radiated heat reaches the furnace wall first. , part of it reaches the workpiece through reflection and secondary emission, and part of it is inevitably absorbed by the furnace wall and lost through conduction, resulting in energy loss.

Regardless of whether diffusion combustion or premixed combustion is adopted, the temperature gradient of the flame front is large, and the temperature distribution near it is very uneven. The existence of a local high-temperature zone will increase the cracking of _N2 in the combustion-supporting air to produce NOx; it is difficult to achieve complete combustion, and the thermal efficiency Low; while the combustion products contain CO, CO ₂ , NOx and other pollutants, causing the gas to be discharged into the atmosphere and causing environmental pollution.

The adjustment ratio of traditional burners is small, and most of them can only reach about 3. For the same gas fuel, the combustion intensity can be increased by increasing the gas flow, or the gas flow can be reduced to keep the workpiece warm, but if the gas flow changes too much, the burner cannot work; for different types of gas fuel For example, when the type of fuel changes, the calorific value also changes accordingly, and the gas flow required for combustion also changes. will not work properly. For example, in the past, it was difficult to use natural gas for burners that used blast furnace gas.

In addition, the traditional burner has a large volume and a relatively complicated structure, and the cost of manufacturing, installation and modification is relatively high.

Contents of the invention

In order to overcome the shortcomings of traditional heat treatment furnaces, the present invention provides a heat treatment furnace using a porous medium burner, which improves thermal efficiency, reduces production costs, improves the quality and output of workpieces, and reduces pollutant emissions. The combustion is uniform, and the internal temperature difference of the workpiece is small during the heat treatment process.

The technical scheme adopted in the present invention is:

The furnace includes a hearth body and burners. The main body of the furnace is composed of a furnace roof, a furnace side wall, a furnace bottom, a furnace door and a flue gas outlet. The burner is made of porous ceramic foam and is arranged on the top or side wall of the furnace. The masonry around the burner outlet section is designed as a gradually expanding bell mouth shape. The intersection line of the extension surface of the mouth section of two adjacent burners or the burner outlet The intersection line of the section extension surface and the furnace wall is located above the workpiece to be heated.

The ceramic material of the burner can be cordierite, yttria-based zirconia, silicon nitride, aluminum oxide, or ceramic particles bonded with a binder. The burner is composed of one or more identical combustion units, and each combustion unit includes an upstream small-pore ceramic foam premixing zone and a downstream large-pore ceramic foam combustion zone, or gradually transitions from small pores to large pores The graded gradient structure, the small-pore ceramic foam premixing area is connected with the pre-mixed gas input pipeline with valves, the small-pore ceramic foam is required to withstand high temperatures above 1200°C, and the large-pore ceramic foam is required to withstand high temperatures above 1500°C. The pore diameter of the small-pore ceramic foam premixing zone is 50-60PPI, and the porosity ε73-85%; the pore diameter of the large-pore ceramic foam combustion zone is 10-20PPI, and the porosity ε73-85%. The cross-sectional shape of the burner outlet can be circular, rectangular or other shapes. The calorific value of the gaseous fuel used for combustion ranges from 800 to 9000kcal/m ³ , which can be blast furnace gas, coke oven gas, high-coke mixed gas, natural gas or liquefied gas. The heat treatment furnace can be a variety of heat treatment furnaces such as batch or continuous.

The main material of the burner of the heat treatment furnace is porous ceramic foam, which has the characteristics of high temperature resistance, oxidation resistance, thermal shock resistance, and corrosion resistance; and the burner based on this porous ceramic foam material has high combustion efficiency and fast combustion speed. , low pollutant emission, large adjustment ratio, small volume and other advantages; this type of burner can burn gaseous fuels with a calorific value ranging from 800 to 9000kcal/m ³ (3344 to 37620kJ/m ³ ) or more, such as blast furnace gas, Coke oven gas, high coke mixed gas, natural gas, liquefied petroleum gas, etc.

The main body of the porous media burner is divided into two sections: the upstream small-pore ceramic foam premixing zone and the downstream large-pore ceramic foam combustion zone. It mainly relies on the principle of super-adiabatic combustion to increase the combustion temperature and rate. Compared with the traditional free space combustion, the combustion in the porous medium is relatively complete, most of the CO is converted into CO ₂ , the formation rate of NOx is reduced, and the nitrogen content of the unburned hydrocarbons after burning by the porous medium burner is lower than 30ppm , the carbon monoxide content is less than 10ppm. Nearly 20% of combustion heat is output by radiation from the burner outlet section (generally a plane), and nearly 80% is output by combustion product enthalpy. Most of the energy output by radiation can directly reach the surface of the workpiece; at the same time, because the combustion is basically completed in the macroporous medium, the combustion products at the cross-section outlet reach the highest temperature (close to the "heating temperature"), and the temperature difference between the flue gas and the workpiece is the largest at this time. Thereby enhancing convective heat transfer. It can be seen that the use of porous media burners can improve efficiency and enhance heat transfer.

The refractory masonry around the burner outlet section is designed into a gradually expanding bell shape, and the intersection line of the extension surfaces of the two adjacent burner outlet sections or the intersection line between the extension surface of the burner outlet section and the furnace wall is located above the workpiece to be heated . In this way, most of the radiation at the exit section of the burner can directly reach the surface of the workpiece (there is a small amount of attenuation caused by the existence of combustion products between the exit section and the surface of the workpiece), instead of being reflected and re-emitted by the furnace wall, avoiding radiation The appearance of dead zone and heat loss in the furnace wall.

According to different on-site process requirements and output requirements, the burner section can be designed as a circle, square, rectangle or other shapes, and several combustion units can also be combined into a larger burner; the arrangement can be horizontal, Place it vertically or at a certain angle to the axis; place it on the top of the furnace or on the side wall of the furnace according to production needs.

The porous media burner can replace a variety of traditional burners represented by flat flame burners, so the porous media burner as one of the contents of the present invention is not limited to the use of heat treatment furnaces, it can also be applied to other flame furnaces such as Various heating furnaces, soaking furnaces, etc.

The heat treatment furnace using the porous media burner can replace the existing intermittent and continuous heat treatment furnaces that use gaseous fuels (blast furnace gas, coke oven gas, high-coke mixed gas, natural gas, liquefied petroleum gas, etc.). So as to achieve the effect of saving energy and reducing pollutant emissions.

The relevant geometric parameters of the heat treatment furnace adopting the porous media burner in the present invention are as follows:

Heat treatment furnace h ₁ 140~300mm; h ₂ 500~800mm;

Burner h ₃ 20～50mm; h ₄ 25～60mm; a(Φ)100～240mm;

The pore size of the small-pore ceramic foam premixing zone is 50-60PPI; the porosity ε73-85%;

The pore diameter of the macroporous ceramic foam combustion zone is 10-20PPI; the porosity ε73-85%.

The relevant process parameters of the porous media burner are as follows:

Combustion gas: blast furnace gas, coke oven gas, high coke mixed gas, natural gas, liquefied petroleum gas;

Air flow: 10～300m ³ /h (natural gas as an example);

Gas flow: 1.0～20m ³ /h (natural gas as an example);

Combustion effect: unburned hydrocarbons, nitrogen content less than 30ppm, carbon monoxide less than 10ppm.

The beneficial effect of the present invention is: compared with the traditional burner, the adjustment ratio of the porous media burner is larger (more than 5 times), and it can also work when the gas flow rate changes in a large range or the gas type changes, so as to adapt to more Strict on-site process requirements. For a porous media burner composed of several combustion units, each unit is connected to a premixed gas input pipeline with a valve, and the supply can be adjusted through the valve according to the process requirements. The porous media burner is small in size, low in manufacturing cost and low in installation difficulty, and its compact structure allows it to be conveniently arranged at any position on the top or side wall of the furnace.

Description of drawings

Fig. 1 is the structural representation of the heat treatment furnace that adopts porous media burner;

Fig. 2 is a schematic diagram of the longitudinal arrangement of the burner with a rectangular outlet section along the furnace length direction;

Fig. 3 is a schematic diagram of the horizontal layout of the burner with a rectangular outlet section along the furnace length direction;

Fig. 4 is a schematic diagram of a porous media burner composed of 3 combustion units;

Fig. 5 is a schematic diagram of the structure of a two-stage porous media combustion unit.

In Fig. 1-5, 1 porous media burner, 2 furnace roof, 3 heat treatment furnace furnace, 4 flue gas outlet, 5 furnace door, 6 premix gas input pipe, 7 valve, 8 small hole ceramic foam premix zone, 9 Large cell ceramic foam combustion zone.

a- side length of rectangular burner (diameter of circular burner), h ₁ - thickness of furnace top, h ₂ - height of furnace, h ₃ - height of small-pore ceramic foam premixing zone, h ₄ - large-pore ceramic foam combustion zone high.

Detailed ways

Taking a porous media burner with a rectangular outlet section as an example, the specific implementation of a heat treatment furnace using a porous ceramic foam burner is described. As shown in Figure 1, the hearth 3 of the heat treatment furnace is a rectangular parallelepiped structure, the front of the hearth 3 is equipped with a furnace door 5, and 2 is the furnace roof, and the porous medium burner 1 is arranged on the furnace roof 2, in order to make the porous ceramic foam under high temperature burn Burner 1 takes advantage of its large radiation output. The refractory masonry with the outlet section of the burner facing down is designed as a trumpet shape that gradually widens from top to bottom. The intersection of the extension surfaces of the outlet sections of two adjacent burners or the The intersection line between the extension surface of the outlet section and the furnace wall is located above the workpiece to be heated. The flue gas outlet 4 is arranged on both side walls of the furnace 3, and the bottom of the flue gas outlet 4 is flush with the bottom of the furnace. Figures 2 and 3 show two arrangements of porous media burners 1 with rectangular outlet cross-sections. As shown in the figure, six rectangular burners 1 of 200×600 mm are divided into two rows, with three burners in each row, along the length direction of the furnace 3 Place it vertically or horizontally. FIG. 4 shows a schematic diagram of the porous media burner 1 . The porous media burner 1 is composed of three combustion units with a square section. The upstream of the combustion unit is a small-pore ceramic foam premixing zone 8, and the downstream is a large-pore ceramic foam combustion zone 9, and the small-pore ceramic foam premixing zone 8 is connected to a premixed gas input pipeline 6. When the burner is working, the premixed gas enters the small-pore ceramic foam premixing zone 8 through the pipeline 6 for preheating, and then burns in the large-pore ceramic foam combustion zone 9 . Each pipeline 6 is equipped with a valve 7. During the working process, the flow in the input pipeline 6 can be increased or decreased by adjusting the valve 7, so as to control the heat load of each combustion unit. In the case of a small heating capacity, it can even be Closing a certain valve 7 does not affect the work of other combustion units, so as to achieve the effect of further adjusting the heat load.

Geometric dimensions can be taken from the following table:

Group value (mm) parameter 1 2 3 4 5 h₁ 150 180 210 240 270 h₂ 500 600 650 700 800 h₃ 20 25 30 35 50 h₄ 25 30 40 45 60 a 100 140 180 220 240 Φ 100 140 180 220 240 The average pore diameter of the ceramic material in the combustion zone of macroporous ceramic foam mm 3 2.8 5 4.5 4 Porosity of ceramic material in the combustion zone of macroporous ceramic foam % 73 75 80 82 85 Macroporous ceramic foam combustion zone material Yttria Stabilized Zirconia Calcia stabilized zirconia Yttria Stabilized Zirconia Calcia stabilized zirconia Yttria Stabilized Zirconia The average pore diameter of the ceramic material in the small-pore ceramic foam premixing zone mm 0.3 0.28 0.5 0.4 0.45 Porosity of ceramic material in small-pore ceramic foam premixing zone% 73 75 80 82 85 Small Pore Ceramic Foam Premixing Zone Material silicon carbide cordierite Alumina Binder bonded ceramic particles silicon nitride

Application of the device of the present invention, specific examples are as follows:

The steel billet is selected as the workpiece to be heated and placed horizontally on the hearth roller, and the premixed gas is fed into each combustion unit through the pipeline 6, and the high-temperature flue gas generated by combustion heats the steel billet through convective heat exchange and radiation heat exchange. At the same time, the high-temperature porous The outlet section 1 of the media burner heats the billet by radiation.

heating conditions

Equivalent ratio 0.75

Burner position Furnace roof (placed horizontally along the furnace length)

Burner outlet section heat load 1704.3kW/m ²

Burner size 200mm×600mm (6 pieces)

Macroporous ceramic foam combustion zone material Calcia stabilized zirconia

Small Cell Ceramic Foam Premixing Zone Material Aluminum Oxide

Billet Thickness 110mm

The height of the billet from the bottom of the furnace is 50mm

Flue gas outlet size 220mm×185mm (12 pieces)

Heating effect: The steel billet with an initial temperature of 300K can reach a maximum surface temperature of 1420K after about 85 minutes. The heating speed is fast, the cross-section temperature difference is small, and the temperature distribution is uniform.

Claims (5)

1. heat treatment furnace that adopts porous media combustor, comprise burner hearth main body and burner, wherein the burner hearth main body comprises furnace roof, furnace sidewall, furnace bottom, fire door and exhanst gas outlet, it is characterized in that burner adopts the porous ceramics foam, burner arrangement is on roof of the furnace or side wall, masonry is designed to the hydraucone shape of flaring around the burner outlet cross section, the intersection of the intersection of the extended surface in adjacent two burner outlet cross sections or burner outlet cross section extended surface and furnace wall is positioned at and is heated the workpiece top, described burner is to be combined by one or more identical fuel elements, each fuel element comprises pre-confounding of upstream aperture ceramic foam and macropore ceramic foam combustion zone, downstream, or carry out the transition to the classification grading structure of macropore gradually by aperture, the aperture ceramic foam requires anti-high temperature more than 1200 ℃, the macropore ceramic foam requires anti-high temperature more than 1500 ℃, the pre-confounding of aperture ceramic foam aperture 50～60PPI, porosity ε 73～85%, described macropore ceramic foam combustion zone aperture 10～20PPI, porosity ε 73～85%.

2. according to the described a kind of heat treatment furnace that adopts porous media combustor of claim 1, the material of pottery that it is characterized in that described burner is with trichroite, yttria-base zirconium white, silicon nitride, aluminum oxide, or with binding agent agglutinating ceramic particle.

3. according to claim 1 or 2 described a kind of heat treatment furnaces that adopt porous media combustor, it is characterized in that described burner outlet cross-sectional shape is circle or rectangle.

4. according to the described a kind of heat treatment furnace that adopts porous media combustor of claim 1, it is characterized in that the geseous fuel calorific value variation range of described burner combustion is 800～9000kcal/m ³, geseous fuel is blast furnace gas, coke-oven gas, high coke mixed gas, Sweet natural gas or liquefied gas.

5. the described a kind of application of adopting the heat treatment furnace of porous media combustor of claim 1 is characterized in that heat treatment furnace is intermittent type or continuous heat-treating drier.

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