Tempering-preventing multi-nozzle burner and waste gas treatment methodTechnical Field
The invention relates to the field of petrochemical waste gas purification, in particular to an anti-backfire multi-nozzle burner and a waste gas treatment method.
Background
Burners are a key part of gas/exhaust gas combustion devices, and are commonly found in various combustion related industrial equipment such as direct-fired boilers, regenerative combustion devices, garbage incinerators, and exhaust gas turbines. The burner with good performance can reasonably organize the mixing of fuel and oxidant (such as air), realize safe and stable combustion, and ensure sufficient combustion efficiency and pollutant emission standard. For some special petrochemical devices, the requirements of flexible adjustment of flame length, combustion initiation temperature, heating temperature and heat load are also met. The mixing mode of the gas fuel and the air can be classified into three types, that is, diffusion combustion, partial premixed combustion, and complete premixed combustion. The air supply mode can be divided into an injection type burner, a blast type burner, a natural induced draft type burner and the like. The fuel gas heat value can be classified into a low heat value burner and a high heat value burner. The sites formed by mixing the fuel gas with air may be divided into an external mixing burner and an internal mixing burner. The flue gas outlet speed can be divided into a low-speed burner and a high-speed burner. The nozzle flow rate of the low-speed burner is lower than 50m/s, and the nozzle flow rate of the high-speed burner is higher than 50m/s, generally 200-300m/s.
The fully premixed burner mixes the fuel gas and the air in advance, and enters the combustion chamber, so that the fuel gas and the air are uniformly mixed, the combustion is performed better, the combustion is more stable, the generated incomplete combustion is less, and the combustion uses lower pressure, so that the combustion supporting of a low-pressure fan is not needed or required. When the flow rate of the fully premixed burner is low, the condition of tempering is easy to occur, so that the requirements on the heat value and the density of the fuel gas are strict before design, the adjustment is smaller, the fully premixed burner is used as an anti-tempering device, the heat load of a single burner is smaller, the noise is larger, and particularly, the operation under high pressure and high load is more obvious.
Part of the premixed burner is mixed with part of air (the primary air accounts for 20% -80%) before burning, part of the mixed combustion-air mixture is directly burnt after exiting the burner, and the rest of the fuel gas is burnt through diffusion mixing with surrounding air. The partially premixed burner is generally designed into a single nozzle form (such as a straight pipe), and when the combustion load is large, the problem of flame-out or flameout easily occurs. The nozzle head may also be designed in the form of a multi-fire hole, but requires a higher pressure.
The diffusion combustion method is to separate air and fuel before combustion, supply air during combustion, and mix the fuel and air at the contact surface and burn. The supply mode of air can be divided into the modes of spontaneous combustion induced air and forced air blowing. Natural induced draft type is used for civil use, the jet speed of the jet nozzle is low, and the investment is small. The forced air-blasting type combustion mode is mainly applied to industrial application, the combustor comprises a complex cyclone structure, forced air blasting is needed, the design and manufacturing cost is high, and the combustion effect is stable.
The specific range of the burner is the waste gas treatment in petrochemical enterprises, the components in the waste gas contain part of air with the ratio of 0-98%, the combustible components in the waste gas are less, the part of waste gas is in a non-spontaneous combustion, combustible and explosive section, and the combustion mode is a diffusion combustion mode, a partial premixed combustion mode and a full premixed combustion mode. When deflagration occurs, tempering is easy to occur, so that a stable and safe combustion mode is needed, and accidents are reduced.
Waste gas from petrochemical enterprises. The waste gas of petrochemical enterprises has complex components, the air accounts for 0-98%, the other components account for 0.5-10%, the components are complex, and hydrogen, methane and ethane to diesel components can exist, and the explosion range of each component is different. Because of the complex components of the waste gas, the existing combustion modes have the problems of imperfect combustion technology or combustion applicability. It is desirable to find a suitable burner that can be safely used also in the explosive range. Therefore, the design of the novel burner has the advantages of adjustable load, relatively low manufacturing cost, flexible and convenient operation, meeting environmental protection indexes and adapting to wide proportion, and has important significance for developing industrial environmental protection equipment.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides an anti-backfire multi-burner which ensures that the temperature of flame is not transmitted to the exhaust gas quantity, backfire does not occur, and an exhaust gas pipeline is not ignited. The invention also provides a method for treating waste gas by using the tempering-preventing multi-nozzle burner.
The tempering-preventing multi-burner comprises a burner main body, wherein the burner main body comprises a heat exchange cavity, a first pipeline for introducing waste gas, a second pipeline for introducing fuel gas and a third pipeline for introducing combustion-supporting air are arranged at the bottom of the burner main body, a plurality of waste gas branch pipes are connected to the first pipeline, the waste gas branch pipes extend upwards to the top of the burner main body, waste gas burner nozzles are arranged at waste gas outlets of the waste gas branch pipes, a plurality of fuel gas branch pipes are connected to the second pipeline, the fuel gas branch pipes extend upwards to the top of the burner main body, burner nozzles are arranged at fuel gas outlets of the fuel gas branch pipes, and combustion-supporting air outlets for delivering combustion-supporting air are arranged at the top of the burner main body.
As a preferable structure of the present invention, the fuel gas branch pipes are spaced apart between the exhaust gas branch pipes.
As a preferred structure of the present invention, the first pipe is coiled into an exhaust gas pipe bundle at the bottom of the burner body, the exhaust gas pipe bundle being in communication with each of the exhaust gas branch pipes.
As a preferable structure of the present invention, the second pipe is coiled into a fuel gas pipe bundle at the bottom of the burner body, the fuel gas pipe bundle being in communication with each of the fuel gas branch pipes.
As a preferable structure of the present invention, the third pipe has a cylindrical structure.
As a preferred structure of the present invention, the fuel gas tube bundle is disposed above the exhaust gas tube bundle.
As a preferred structure of the present invention, the burner nozzle includes a porous nozzle and an auto-ignition device.
As a preferable structure of the present invention, the exhaust gas burner includes a venturi tube and a flame retardant device provided at a tip end of the exhaust gas burner.
The invention discloses a method for treating waste gas by using the tempering-preventing multi-nozzle burner, which comprises the following steps:
when the device is started, firstly, combustion-supporting air enters a burner main body, and equipment is purged for 5-10 minutes;
(S2) after the purging is finished, igniting the igniter, enabling a fuel gas pipeline to enter the combustor and input fuel gas, and igniting the fuel gas;
And (S3) after the fuel gas is ignited, adjusting the heating speed of the furnace, when the temperature in the furnace is raised to more than 650 ℃, throwing the waste gas, and enabling the waste gas to enter the burner ejection port from the waste gas channel, wherein the waste gas is ignited at a high temperature.
The burner has the beneficial effects that (1) through the arrangement of the main body structure of the burner, the waste gas exchanges heat with the combustion air, the cold combustion air cools the waste gas, the waste gas end is provided with a plurality of Venturi tube bundles, the heat exchange area is increased, the temperature of the waste gas is reduced more thoroughly than that of the conventional fuel gas, the temperature of the waste gas is lower than the ignition point, and the burner has the functions of fire resistance and flame retardance. (2) The burner of the invention ensures the safety of the combustion of the waste gas, ensures that the temperature of flame is not transferred to the waste gas quantity, does not generate tempering and does not ignite a waste gas pipeline through the low-temperature control of the flow rate of the waste gas and the low-temperature control of the waste gas and the increase of the fire resistance performance.
Drawings
FIG. 1 is a schematic view of an anti-backfire multi-burner according to the present invention;
FIG. 2 is a schematic diagram of the exhaust burner distribution of the present invention;
FIG. 3 is a schematic diagram of the burner nozzle distribution of the fuel gas of the present invention;
Fig. 4 is a schematic view of the exhaust burner and venturi structure in the burner nozzle of the present invention.
Detailed Description
Example 1 As shown in figure 1, the medium of the burner is fuel gas, waste gas and air, and the burner is a combination of three mediums for combustion and combustion supporting. The burner includes combustor main part 1, and combustor main part 1 includes heat transfer chamber 100, and the bottom of combustor main part 1 is provided with the first pipeline 2 that lets in waste gas and is used for the second pipeline 3 that the fuel gas lets in and is used for the third pipeline 4 that the combustion-supporting wind lets in, and in this embodiment, third pipeline 4 is cylindrical structure, and combustor main part 1 top is provided with the combustion-supporting wind gas outlet 401 that is used for the combustion-supporting wind to send out. The pipeline of the invention is made of various materials, wherein the materials of fuel gas and waste gas are stainless steel and ultrahigh temperature resistant materials, and the materials of the combustion-supporting air path are stainless steel or carbon steel. The furnace body of the burner main body is made of carbon steel, and the branch pipeline is made of stainless steel.
The first pipeline 2 is connected with a plurality of exhaust branch pipes 201, the exhaust branch pipes 201 extend upwards to the top of the combustor main body 1, the top of each exhaust branch pipe 201 is an exhaust outlet 202, an exhaust outlet 202 of each exhaust branch pipe 201 is provided with an exhaust burner 203 combustor nozzle, the first pipeline 2 is coiled into an exhaust pipe bundle 204 at the bottom of the combustor main body 1, the exhaust pipe bundles 204 are communicated with each exhaust branch pipe 201, and an inlet of the first pipeline 2 is an exhaust inlet 205. As shown in fig. 4, the exhaust burner 203 includes a venturi 5 and a flame retardant device 206 provided at the tip of the exhaust burner 203, and an exhaust gas passage 207 is provided between the venturi 5 and the flame retardant device 206.
The second pipeline 3 of the invention is connected with a plurality of fuel gas branch pipes 301, the fuel gas branch pipes 301 extend upwards to the top of the burner main body 1, a porous nozzle 305 is arranged at the fuel gas outlet 302 of the fuel gas branch pipes 301, the porous nozzle 305 is arranged at the top end of the burner nozzle 303, the porous nozzle 305 is in an umbrella-shaped structure, and a plurality of combustion holes for gas spraying are arranged around the umbrella-shaped structure. The second pipe 3 is coiled into a fuel gas pipe bundle 304 at the bottom of the burner body 1, and communicates with each of the fuel gas branch pipes 301 through the fuel gas pipe bundle 304. The gas end of the fuel gas manifold 301 includes, in addition to the porous nozzle 305, a conventional auto-ignition device (not shown) positioned at the gas outlet section of the fuel gas manifold 301, an ignition device positioned beside the porous nozzle, and the burner nozzle 203 having a porous nozzle with auto-ignition function, the fuel gas entering the fuel gas flow channel 306 through the venturi structure 5 positioned on the fuel gas manifold 301 and then entering the porous nozzle 305 to be auto-ignited.
As a preferable structure of the present embodiment, the fuel gas branch pipes 301 are spaced apart from the exhaust gas branch pipes 201, and the third duct 4 for feeding combustion air (air) of the present invention is a straight cylindrical structure. According to the invention, through the arrangement of the pipelines of the fuel gas, the fuel gas and the waste gas, the heat exchange between the air end and the waste gas and between the air end and the fuel gas is realized, and the three paths of heat are balanced. Because the flow velocity of the exhaust gas is greater than the flashback combustion speed of the flame, the burner has a flashback prevention function. The waste gas exchanges heat with the combustion air, the cold combustion air cools the waste gas, the heat exchange area is increased, the waste gas temperature is reduced more thoroughly than the conventional fuel gas, the waste gas temperature is lower than the ignition point, and the burner has the functions of fire resistance and flame retardance.
As a preferable structure of the invention, the combustion disk of the waste gas is positioned above the Venturi tube bundle, the combustion disk is formed by winding a plurality of metal plates, the gap between the metal plates is very small, the flow velocity of the waste gas in the combustion disk is also very high, the channel area between the metal plates is very large, the heat transfer is enhanced, the flame temperature is reduced below the ignition point, the flame is prevented from spreading to the fuel gas, and the effects of fire resistance and tempering prevention are achieved. The burning disk of the waste gas has a certain thickness, the two sides of the channel between the metal plates are called channel walls, and the thicker the burning disk is. The combustion and explosion are not direct reactions among molecules, but are excited by external energy, molecular bonds are broken to generate activated molecules, the activated molecules are split into free radicals with short service life and very activity, the free radicals collide with other molecules to generate new products, and the new free radicals are generated to react with other molecules. When the burnt combustible gas passes through the narrow long passage of the fire-retarding element, the probability of collision of free radicals with the passage walls increases and the free radicals participating in the reaction decrease. When the channel of the flame arrester is narrow to a certain extent, collision of free radicals and the channel wall is dominant, and the reaction cannot be continued due to the rapid reduction of the number of the free radicals, namely the combustion reaction cannot be continuously propagated through the combustion disc, so that the flame arrester has a flame-retardant effect.
In the burner of the present invention, the exhaust gas section burns at a high speed, the normal flow rate is greater than 50 m/s, and the minimum flow rate is 15 m/s. The flow rate of the waste gas outlet end of the first pipeline 2 entering the venturi throat pipe is more than 15m/s, the venturi tube bundle has an automatic control adjusting function, the number of waste gas branch pipes 201 for introducing waste gas is adjusted under the condition of 5-110% of flow rate, and the flow rate in the venturi throat pipe for introducing waste gas is ensured to meet the flow rate requirement of more than 15 m/s.
When the device is started, combustion-supporting air enters the device, and the device is purged for 5-10 minutes. After purging, the igniter ignites, the fuel gas pipeline enters the burner and is thrown into the fuel gas, the fuel gas is ignited, if the fuel gas cannot be ignited, the fuel gas is closed, the equipment is restarted, after the fuel gas is ignited, the heating speed of the furnace is regulated, when the temperature in the furnace is raised to be more than 650 ℃, waste gas is thrown into, the waste gas enters the top end outlet of the burner from the waste gas channel, the waste gas is ignited at a high temperature, and the whole combustion hearth has flame with a higher length due to a higher flow speed of the waste gas. Because the combustion-supporting air speed is slower, and the speed difference is formed between the combustion-supporting air speed and the flow speed of the waste gas and the fuel gas, the gas flow state of the hearth can form turbulence, and the ignition degree and the combustion efficiency are increased.
The invention has the effects that the whole temperature of the combustion chamber is controlled to 760-820 ℃, the total non-methane hydrocarbon is controlled to be no more than 20mg/m3, the NOx content is controlled to be no more than 50mg/m3 under the condition that the combustion time is more than or equal to 2S, and the content indexes are calculated according to the 3% oxygen content in GB31570 and GB31571 standards.
After combustion, the removal rate of the non-methane total hydrocarbon is over 99 percent, and the requirements of national standards GB31570 and GB31571 are met.
The system of the invention adopts the components of fuel gas, waste gas and combustion-supporting air, flow state layout, flow rate design and hardware, and adopts the Venturi devices arranged at the outlet ends of the fuel gas and the waste gas to symmetrically distribute the whole structure, as shown in figures 2 and 3, the tube bundle ratio of the fuel gas to the waste gas is 1:6-20, the waste gas enters the combustion chamber through the fire retardant device, the temperature of flame is ensured not to be transmitted to the waste gas amount, no backfire occurs, and the waste gas pipeline is not ignited
The foregoing describes one embodiment of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.