阅读说明：本技术 一种辐射管低氮燃烧及烟气余热回收系统 (Radiant tube low-nitrogen combustion and flue gas waste heat recovery system ) 是由 宋中华 李�浩 王昌亮 丁翠娇 闫乃忠 杨超 胡金伟 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种辐射管低氮燃烧及烟气余热回收系统,包括辐射管、烧嘴、燃气管道、常温空气管道、盘管、进水管道、水蒸汽管道和排水管道；所述辐射管的一端安装烧嘴,所述燃气管道、常温空气管道和水蒸汽管道分别与烧嘴内部连通；所述辐射管的另一端为烟气出口端,烟气出口端连通有排烟管道,排烟管道内安装盘管；所述进水管道与盘管的进水口连通,盘管的蒸汽出口与水蒸汽管道连通。本发明的有益效果为：本发明在排烟管道内设计盘管,将辐射管排出烟气的高温余热将水加热成水蒸汽,再与助燃空气混合后进入辐射管中与燃气混合燃烧,降低了燃烧区氧浓度及高温峰值,不需要在辐射管烧嘴上安装布置专门的复杂烟气卷吸回流装置,所需空间小。(The invention discloses a radiant tube low-nitrogen combustion and flue gas waste heat recovery system which comprises a radiant tube, a burner, a gas pipeline, a normal-temperature air pipeline, a coil pipe, a water inlet pipeline, a water vapor pipeline and a drainage pipeline, wherein the burner is arranged on the radiant tube; a burner is arranged at one end of the radiant tube, and the gas pipeline, the normal-temperature air pipeline and the water vapor pipeline are respectively communicated with the inside of the burner; the other end of the radiant tube is a smoke outlet end which is communicated with a smoke exhaust pipeline, and a coil is arranged in the smoke exhaust pipeline; the water inlet pipeline is communicated with the water inlet of the coil pipe, and the steam outlet of the coil pipe is communicated with the steam pipeline. The invention has the beneficial effects that: according to the invention, the coil pipe is designed in the smoke exhaust pipeline, the high-temperature waste heat of the smoke exhausted by the radiant tube heats water into steam, and the steam is mixed with combustion-supporting air and then enters the radiant tube to be mixed and combusted with gas, so that the oxygen concentration and the high-temperature peak value in a combustion area are reduced, a special complex smoke entrainment reflux device is not required to be arranged on a burner of the radiant tube, and the required space is small.)

1. A radiant tube low-nitrogen combustion and flue gas waste heat recovery system is characterized by comprising a radiant tube, a burner, a gas pipeline, a normal-temperature air pipeline, a coil, a water inlet pipeline, a water vapor pipeline and a drainage pipeline; a burner is arranged at one end of the radiant tube, and the gas pipeline, the normal-temperature air pipeline and the water vapor pipeline are respectively communicated with the inside of the burner; the other end of the radiant tube is a smoke outlet end which is communicated with a smoke exhaust pipeline, and a coil is arranged in the smoke exhaust pipeline; the water inlet pipeline is communicated with the water inlet of the coil pipe, and the steam outlet of the coil pipe is communicated with the steam pipeline; steam in the steam pipeline and combustion air in the normal-temperature air pipeline enter the burner to be mixed with fuel gas for combustion, high-temperature flue gas generated by combustion exchanges heat with water in the water inlet pipeline through the coil pipe, and the high-temperature flue gas enters the nozzle after being heated by the water to generate steam.

2. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system of claim 1, wherein the coil is of a spiral structure and vertically arranged in the smoke exhaust duct from top to bottom; the water inlet of the coil pipe is positioned at the lower end and is communicated with the water inlet pipeline; the steam outlet of the coil is positioned at the upper end and is communicated with the water steam pipeline; water enters from the lower end of the coil pipe, steam is generated above the coil pipe and then flows out, the water flow direction is from bottom to top, water enters from the lower part, and steam exits from the upper part.

3. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system of claim 2, wherein fins are arranged on the outer wall of the coil.

4. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system of claim 2, wherein the coil is a hollow steel or copper tube.

5. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system as claimed in claim 1, wherein an air-smoke heat exchanger is installed at the outlet end of the radiant tube, an air flow channel is arranged inside the air-smoke heat exchanger, the inlet of the air flow channel is communicated with a normal-temperature air pipeline, and the outlet of the air flow channel is communicated with a heating air pipeline; a gap between the outer wall of the air-smoke heat exchanger and the inner wall of the radiant tube is a smoke flow channel; the water vapor pipeline is communicated with the heating air pipeline; air in the air flow channel exchanges heat with flue gas and then enters the air heating pipeline, and the air and the flue gas are mixed with steam in the water steam pipeline and then enter the nozzle to be mixed and combusted with fuel gas.

6. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system of claim 5, wherein the air-smoke heat exchanger is installed at the connection of the smoke exhaust duct and the radiant tube.

7. The radiant tube low-nitrogen combustion and flue gas waste heat recovery system as claimed in claim 1, wherein the radiant tube is a U-shaped tube.

Technical Field

The invention relates to the field of metallurgical energy, in particular to a radiant tube low-nitrogen combustion and flue gas waste heat recovery system.

Background

Currently, the traditional low-nitrogen oxide combustion technology widely used in the steel industry mainly comprises a staged combustion process and a flue gas circulation process. The flue gas circulation process is characterized in that flue gas containing nitrogen, water vapor and carbon dioxide generated by combustion is mixed into combustion air through a device, and the flue gas is used for reducing the oxygen concentration and local high temperature in a combustion area, so that the generation amount of nitrogen oxides is reduced. In this process, it is very important how efficiently the flue gas is introduced into the combustion air to dilute the oxygen content of the air. However, the radiant tube used for the cold rolling annealing furnace has a small tube diameter, and has the following problems:

(1) because the radiant tube has smaller structure size and the combustion device has complex structure, when the flue gas reflux low-nitrogen oxide combustion technology is adopted, a special flue gas entrainment device is needed; however, the space of the head of the radiant tube is small, especially the space of the U-shaped radiant tube is short, and the spaces of the heat exchanger and the burner side are narrow, so that the smoke reflux device is complex and difficult to arrange, the smoke circulation volume cannot be ensured, and the effect of reducing NOx is poor.

(2) The high-concentration nitrogen contained in the flue gas increases the N concentration of a combustion reaction area, inhibits the effect of reducing nitrogen oxides, increases the volume of gas in the radiant tube, accelerates the flow rate, and causes incomplete combustion when the gas is discharged out of the radiant tube without being completely reacted.

(3) The radiant tube has small combustion space in the tube, high combustion intensity in the tube and high exhaust gas temperature, but the currently used air-flue gas heat exchanger has limited waste heat recovery capability in a limited space, so that the finally exhausted flue gas temperature is overhigh and usually reaches 500-600 ℃, and the finally exhausted flue gas temperature has to be reduced by cold air and then is exhausted into the atmosphere through a flue gas exhaust fan, so that the exhaust gas heat loss is large, and the heat efficiency is low.

Disclosure of Invention

The invention aims to provide a radiant tube low-nitrogen combustion and flue gas waste heat recovery system aiming at the defects of the prior art, solves the problems of local high temperature and high nitrogen oxide emission concentration in the conventional radiant tube, and can recover the heat of high-temperature flue gas exhausted by the radiant tube.

The technical scheme adopted by the invention is as follows: a radiant tube low-nitrogen combustion and flue gas waste heat recovery system comprises a radiant tube, a burner, a gas pipeline, a normal-temperature air pipeline, a coil, a water inlet pipeline, a water vapor pipeline and a drainage pipeline; a burner is arranged at one end of the radiant tube, and the gas pipeline, the normal-temperature air pipeline and the water vapor pipeline are respectively communicated with the inside of the burner; the other end of the radiant tube is a smoke outlet end which is communicated with a smoke exhaust pipeline, and a coil is arranged in the smoke exhaust pipeline; the water inlet pipeline is communicated with the water inlet of the coil pipe, and the steam outlet of the coil pipe is communicated with the steam pipeline; steam in the steam pipeline and combustion air in the normal-temperature air pipeline enter the burner to be mixed with fuel gas for combustion, high-temperature flue gas generated by combustion exchanges heat with water in the water inlet pipeline through the coil pipe, and the high-temperature flue gas enters the nozzle after being heated by the water to generate steam.

According to the scheme, the coil pipe is of a spiral structure and is vertically arranged in the smoke exhaust pipeline from top to bottom; the water inlet of the coil pipe is positioned at the lower end and is communicated with the water inlet pipeline; the steam outlet of the coil is positioned at the upper end and is communicated with the water steam pipeline; water enters from the lower end of the coil pipe, steam is generated above the coil pipe and then flows out, the water flow direction is from bottom to top, water enters from the lower part, and steam exits from the upper part.

According to the scheme, fins are arranged on the outer wall of the coil pipe.

According to the scheme, the coil pipe is a hollow steel pipe or a hollow copper pipe.

According to the scheme, an air-smoke heat exchanger is installed at the outlet end of a radiant tube, an air flow channel is arranged inside the air-smoke heat exchanger, the inlet of the air flow channel is communicated with a normal-temperature air pipeline, and the outlet of the air flow channel is communicated with a heating air pipeline; a gap between the outer wall of the air-smoke heat exchanger and the inner wall of the radiant tube is a smoke flow channel; the water vapor pipeline is communicated with the heating air pipeline; air in the air flow channel exchanges heat with flue gas and then enters the air heating pipeline, and the air and the flue gas are mixed with steam in the water steam pipeline and then enter the nozzle to be mixed and combusted with fuel gas.

According to the scheme, the air-smoke heat exchanger is arranged at the joint of the smoke exhaust pipeline and the radiation pipe.

According to the scheme, the radiant tube is a U-shaped tube.

The invention has the beneficial effects that:

(1) according to the invention, the coil pipe is designed in the smoke exhaust pipeline, the high-temperature waste heat of the smoke exhausted by the radiant tube heats water into steam, and the steam is mixed with combustion-supporting air and then enters the radiant tube to be mixed with fuel gas for combustion, so that the oxygen concentration and the high-temperature peak value in a combustion area are reduced, a special complex smoke entrainment reflux device is not required to be arranged on a burner of the radiant tube, and the required space is small.

(2) The water entering the coil pipe exchanges heat with the high-temperature flue gas discharged by the radiant tube, the temperature of the high-temperature flue gas discharged by the radiant tube can be reduced to be below 300 ℃ (the temperature is measured in actual production), a cold air suction cooling device is not needed, the heat carried by the water vapor and the combustion-supporting air are mixed and then enter the radiant tube again, the flue gas waste heat recovery rate is high, and the heat efficiency is high.

(3) In the invention, the flue gas-water heat exchanger has small size and occupies smaller space than the traditional gas-gas heat exchanger because the phase change heat of water vaporization is larger.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

FIG. 2 is a gas flow diagram in this example.

Fig. 3 is a schematic structural view of the coil pipe in this embodiment.

Wherein: 1-a normal temperature air pipeline; 2-air line valves; 3-a water inlet pipeline; 4-water inlet pipeline valve; 5-a smoke exhaust pipeline; 6-a coil pipe; 7-a water vapor pipeline; 8-steam line valve; 9-heating the air duct; 10-a burner; 11-a gas pipeline; 12-gas pipeline valves; 13-a radiant tube; 14-air-smoke heat exchanger; 15-pipe network valve.

Detailed Description

For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

The system for low-nitrogen combustion of the radiant tube and recovery of the waste heat of the flue gas as shown in fig. 1 comprises a radiant tube 13, a burner 10, a gas pipeline 11, a normal-temperature air pipeline 1, a coil 6, a water inlet pipeline 3 and a water vapor pipeline 7; a burner 10 is installed at one end of the radiant tube 13, and the gas pipeline 11, the normal-temperature air pipeline 1 and the water vapor pipeline 7 are respectively communicated with the interior of the burner 10; the other end of the radiant tube 13 is a smoke outlet end which is communicated with a smoke exhaust pipeline 5, and a coil 6 is arranged in the smoke exhaust pipeline 5; the water inlet pipeline 3 is communicated with a water inlet of the coil pipe 6, and a steam outlet of the coil pipe 6 is communicated with the steam pipeline 7. In the invention, steam in the steam pipeline 7 and combustion-supporting air in the normal-temperature air pipeline 1 enter the burner 10 to be mixed and combusted with fuel gas, high-temperature flue gas generated by combustion exchanges heat with water in the water inlet pipeline 3 through the coil pipe 6, and the water is heated to generate steam which enters the nozzle.

Preferably, as shown in fig. 3, the coil pipe 6 is of a spiral structure and is vertically arranged in the smoke exhaust duct 5 from top to bottom; the water inlet of the coil pipe 6 is positioned at the lower end and is communicated with the water inlet pipeline 3; a steam outlet of the coil 6 is positioned at the upper end and is communicated with a water vapor pipeline 7; water enters from the lower end of the coil pipe 6, steam is generated above the coil pipe and then flows out, the water flow direction is from bottom to top, water enters from the lower part, and steam exits from the upper part.

Preferably, the coil 6 is a hollow steel pipe or copper pipe; the outer wall of the coil pipe 6 is provided with fins, so that the turbulence of smoke is enhanced, and the heat exchange efficiency is improved.

Preferably, an air-smoke heat exchanger 14 is installed at the outlet end of the radiant tube 13, an air flow channel is arranged inside the air-smoke heat exchanger 14, the inlet of the air flow channel is communicated with the normal-temperature air pipeline 1, and the outlet of the air flow channel is communicated with the heating air pipeline 9; a gap between the outer wall of the air-smoke heat exchanger 14 and the inner wall of the radiant tube 13 is a smoke flow channel; the water vapor pipeline 7 is communicated with a heating air pipeline 9; the air in the air flow channel exchanges heat with the flue gas and then enters the heating air pipeline 9, and then enters the nozzle after being mixed with the steam in the water vapor pipeline 7, and is mixed and combusted with the fuel gas.

In the invention, the water vapor is converged into the heating air pipeline 9 through the water vapor pipeline 7, and the normal temperature air enters the air-smoke heat exchanger 14 through the normal temperature air pipeline 1 to exchange heat with the high temperature smoke, so that the air preheating is maximized, and more smoke waste heat can be recovered.

Preferably, the air-fume heat exchanger 14 is installed at the junction of the fume exhaust duct 5 and the radiant tube 13.

Preferably, the radiant tube 13 is a U-shaped tube.

In the invention, a steam pipeline valve 8 is also arranged on the steam pipeline 7, the pressure and the flow of steam entering a heating air pipeline 9 are controlled by the steam pipeline valve, the steam pressure is controlled at 10-15 kPa, the steam flow is determined according to the combustion requirement of a burner 10, the steam flow accounts for 0-50% of the combustion air flow, and O in the air mixed with the steam₂The content is 14-21%.

In this embodiment, an air pipeline valve 2 is configured on the normal temperature air pipeline 1 to control the on-off of air; a gas pipeline valve 12 is arranged on the gas pipeline 11 to control the on-off of gas; a water inlet valve is arranged on the water inlet pipeline 3 to control the on-off of water inlet; the steam channel is communicated with a steam pipe network, and an official network valve is arranged on a communication pipeline of the steam channel and the steam pipe network.

In operation of the system of the present invention, the flow directions of the fluids are as shown in FIG. 2; the whole system is operated by the following three processes:

1. ambient air with the oxygen content of 21 percent enters an air-smoke heat exchanger 14 arranged at the tail part of a radiant tube 13 through a normal-temperature air pipeline 1 and an air pipeline valve 2, and enters a heating air pipeline 9 after heat exchange of smoke in a smoke flow channel;

2. water enters a coil pipe 6 arranged in a smoke exhaust pipe 5 through a water inlet pipe 3 and a water inlet pipe valve 4 and exchanges heat with high-temperature smoke outside the coil pipe 6, the water is heated in the coil pipe 6 to generate water vapor, the water vapor with lower density rises through a water vapor pipe 7, a part of the water vapor enters a heating air pipe 9 through a water vapor pipe valve 8 and is mixed with preheated air in the heating air pipe 9, and then enters a burner 10 arranged in a radiant tube 13 to be mixed with fuel gas for combustion; the other part of the steam enters the steam pipe network through the pipe network valve 15 for other processes;

3. high-temperature flue gas generated by combustion heats the radiant tube 13 and then enters the flue gas flow channel, exchanges heat with air and then exchanges heat with water in the coil 6, and then is discharged.

It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto, and although the present invention has been described in detail with reference to the embodiments, it will be apparent to those skilled in the art that modifications can be made to the technical solutions described in the above-mentioned embodiments, or equivalent substitutions of some technical features, but any modifications, equivalents, improvements and the like within the spirit and principle of the present invention shall be included in the protection scope of the present invention.