EP3666372A1

EP3666372A1 - Flue gas mixing device and method

Info

Publication number: EP3666372A1
Application number: EP18889689.8A
Authority: EP
Inventors: Tingyu Zhu; Wenqing Xu; Chaoqun LI
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2017-12-12
Filing date: 2018-03-06
Publication date: 2020-06-17
Also published as: CN108014667A; CN108014667B; JP2020528343A; JP7078708B2; EP3666372A4; WO2019114138A1

Abstract

A flue gas mixing device and method include a flue entrance section (11), a throat section (22) and a flue exit section (12) that are sequentially communicated, where a plurality of air inlet holes (221) are circumferentially arranged on a side wall of the throat section (22), an annular cavity (3) is arranged on an outer periphery of the throat section (22) and connected to an annular cold exhaust gas branch pipe (31); a necking section (21), connected between the flue entrance section (11) and the throat section (22); and a flaring section (23), connected between the throat section (22) and the flue exit section (12).

Description

TECHNICAL FIELD

The present disclosure relates to the technical field of gas mixing, for example, a flue gas mixing device and method.

BACKGROUND

The sintering flue gas circulation process refers to a sintering method in which a part of the heat carrier gas discharged from a sintering process is circulated to the trolley to use after the sintering igniter. In the related technology, the sintering flue gas circulation process has proposed that in order to ensure quality of the sintered minerals during the flue gas circulation, it is necessary to ensure that the circulating flue gas contains sufficient oxygen. Therefore, in the process design, exhaust gas generated by an annular cooling machine is usually used to supplement oxygen content in the sintering flue gas.
FIG. 1 is a typical process flow diagram illustrating a flue gas circulation in the related art. The equipment shown in FIG. 1 includes: an annular cooling machine 1', an annular cold circulation fan 11', a flue gas mixer 2', a flue gas sealing cover 31', a sintering machine 32', a dust collector 4', a sintering circulation fan 41', a main sintering fan 42', a desulfurization tower 5 ', a chimney 6' and pipelines that connects the equipment. The working process of the sintering process, the sintering flue gas treatment process, and the flue gas circulation process are as follows. Raw materials are sintered in the sintering machine 32', and the sintered hot ore discharged by the sintering machine 32' is cooled by the annular cooling machine 1' and then generates annular cold exhaust gas. And after being pressurized by the annular cold circulation fan 11', the annular cold exhaust gas enters the flue gas mixer 2' and passes through the flue gas sealing cover 31' located above the sintering machine 32' to enter the sintering machine 32', together with the circulation flue gas taken from the sintering machine 32' and pressurized by the sintering circulation fan 41'. Most of the flue gas (non-circulating flue gas) generated by the sintering machine 32' passes through the dust collector 4' and is sent to the desulfurization tower 5 'and the chimney 6' after being pressurized by the main sintering fan 42', and is finally discharged. And the annular cold circulation fan and the flue gas mixer jointly realize the mixing of the annular cold exhaust gas and the circulating flue gas, and supplement of air is mostly realized by arranging a vent valve on the flue gas sealing cover.
At the same time, because the pressure, temperature, flow rate, composition and the like of the two flue gases to be mixed are different, the flue gas mixing device in the related art has the following problems. For example, because of the limited space of the flue and elbow thereof in a mixing device for a three-way flue, there are problems such as air flow deflection and vortexing, flue abrasion, dust accumulation and poor mixing effect, and even air flow back suction during the mixing of the two air flows, resulting in working conditions and accidents such as stall, instability and increased vibration of the flue gas circulating fan; and a mixing device with a multi-mixing cavity and a mixing device with a reducing mixing barrel may fully mix the flue gas, but neither is suitable for the flue gas with large dust content. Therefore, designing a low-resistance flue gas mixing device that may easily adjust the composition of the flue gas and the temperature of the flue gas, stabilize the flow rate of the flue gas, avoid dust accumulation in the flue and abrasion of the flue, and protect the fan and auxiliary flues and other equipment is of great significance to the stable and efficient operation of the gas circulation process.
At the same time, in the related art, the flue gas circulation process directly supplements air from the sealing cover. Due to the large space of the sealing cover, the gas in the sealing cover will be sucked into a sintering bed to participate in the combustion reaction within a relative short residence time. Therefore, the method has the problem of uneven mixing of oxygen in the circulating flue gas, that is, the oxygen content is higher in an area adjacent to the air inlet, and the oxygen content is lower in an area far from the air inlet (also known as a hypoxic dead zone), and the hypoxic dead zone is extremely detrimental to sintering production. Therefore, it is also the key to improve the stability of the flue gas circulation process to make the oxygen carried by the supplemented air mixed evenly in the circulating flue gas by reasonable technical means.

SUMMARY

The present disclosure provides a flue gas mixing device and method, which may solve the problems of high energy consumption and poor flue gas mixing effect of the flue gas mixing device in the related art.
Provided is a flue gas mixing device, including:

a flue entrance section;
a throat section, where a plurality of air inlet holes are circumferentially arranged on a side wall of the throat section;
an annular cavity, arranged on an outer periphery of the throat section;
an annular cold exhaust gas branch pipe, connected to the annular cavity;
a flue exit section;
a necking section, connected between the flue entrance section and the throat section; and
a flaring section, connected between the throat section and the flue exit section.

In an embodiment, an included angle between an axis of the air inlet holes and an axis of the throat section is in a range from 20° to 90°.
In an embodiment, an included angle between an axis of the annular cold exhaust gas branch pipe and an axis of the throat section is in a range from 15° to 75°.
In an embodiment, a cross-section of the annular cavity has a trapezoidal structure, and a corner of the trapezoidal structure has an arc-shaped transition surface.
In an embodiment, the flue gas mixing device further includes an air branch pipe and a control assembly, where an included angle between an axis of the air branch pipe and an axis of the throat section is in a range from 30° to 90°; and the air branch pipe includes an electric valve, and the electric valve is electrically connected to the control assembly.
In an embodiment, the flue gas mixing device further includes an oxygen content monitor arranged on the flue exit section, where the oxygen content monitor is electrically connected to the control assembly.
In an embodiment, the flue gas mixing device further includes an ash hopper arranged on a bottom of the flue exit section.
In the embodiment, a diameter of the flue exit section is greater than a diameter of the flue entrance section.
Further provided is a flue gas mixing method, including the following steps:

the flue gas is introduced to a flue entrance section;
the annular cold exhaust gas is introduced to an annular cold exhaust gas branch pipe; and
the annular cold exhaust gas is mixed with the flue gas to form a mixed gas, after passing through the annular cavity and the air inlet holes in sequence.

In an embodiment, after the annular cold exhaust gas is mixed with the flue gas, the flue gas mixing method further includes monitoring oxygen content of the mixed gas, and adjusting an amount of intake air entering the annular cavity in real time according to the oxygen content.
The flue gas mixing device and method of the present disclosure solves the problems of high energy consumption and poor flue gas mixing effect of the flue gas mixing device in the related art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow schematic diagram illustrating a sintering flue gas circulation process in the related art;
FIG. 2 is a top view illustrating a flue gas mixing device according to an embodiment;
FIG. 3 is a front view illustrating a flue gas mixing device according to an embodiment;
FIG. 4 is a process flow schematic diagram illustrating a sintering flue gas circulation process according to an embodiment; and
FIG. 5 is a flowchart illustrating a flue gas mixing method according to an embodiment.

In the drawings:

1'-annular cooling machine; 11'-annular cold circulation fan; 2'-flue gas mixer; 31'-flue gas sealing cover; 32'-sintering machine; 4'-dust collector; 41'-sintering circulation fan; 42'-main sintering fan; 5'-desulfurization tower; 6'-chimney;
1-annular cooling machine; 3a-flue gas sealing cover; 3b-sintering machine; 4-dust collector; 41-sintering circulation fan; 42-main sintering fan; 5-desulfurization tower; 6-chimney;
11-flue entrance section; 12-flue exit section; 13-ash hopper; 14-oxygen content monitor;
21-necking section; 22-throat section; 23-flaring section; 221-air inlet hole;
3-annular cavity; 31-annular cold exhaust gas branch pipe; 32-air branch pipe; 33-electric valve; 34-control assembly.

DETAILED DESCRIPTION

As shown in FIG. 2, FIG. 2 is a top view (an air branch pipe is not shown in the figure) illustrating a flue gas mixing device according to an embodiment. A main body of the flue gas mixing device has a venturi tube structure, and is provided with a flue entrance section 11, a necking section 21, a throat section 22, a flaring section 23 and a flue exit section 12 which are sequentially arranged along a flowing direction of flue gas. Air inlet holes 221 are evenly, obliquely and circumferentially arranged on a circumferential side wall of the throat section 22. The throat section 22 extends outwardly along a circumferential direction of the throat section 22 to form an annular cavity 3, which coats an outside of the entire throat section 22. An internal of the annular cavity 3 is formed with a space for accommodating gas. A cross-section of the annular cavity 3 may has a circular structure or a trapezoidal structure. In one example, the cross-section of the annular cavity 3 has a trapezoidal structure. In the case that the cross-section of the annular cavity 3 has the trapezoidal structure, a corner of the trapezoidal structure has an arc-shaped transition surface, so that there is no ash accumulation dead corner in the annular cavity 3, ensuring that the air flow entering the inside of the annular cavity 3 is unobstructed and preventing dust accumulation on an inner wall of the annular cavity 3.
The annular cavity 3 extends outwardly to form an annular cold exhaust gas branch pipe 31, and each of the air inlet holes 221 is in communication with the annular cavity 3 and the annular cold exhaust gas branch pipe 31. The annular cold exhaust gas branch pipe 31 is obliquely arranged on the annular cavity 3. By such design, annular cold exhaust gas may enter the annular cavity 3 from the annular cold exhaust gas branch pipe 31, and then enter a flue gas main channel through the air inlet holes 221 evenly and obliquely distributed on the circumferential side wall of the throat section 22, thereby achieving a relatively uniform air intake throughout the throat section 22, buffering and stabilizing incoming flue gas, and making the annular cavity 3 and the flue gas main channel form a stable pressure difference, and maintaining a flow field of the flue gas main channel even and stable. In one embodiment, by using the annular cavity 3 to be filled with the annular cold exhaust gas, all the air inlet holes 221 of the throat section 22 are fully utilized to perform air intake, and the annular cold exhaust gas is accelerated when passing through the air inlet holes 221, thereby achieving the drainage effect on the incoming flue gas. In addition, the air inlet holes 221 on the throat section 22 are obliquely arranged, so that the annular cold exhaust gas may converge with the incoming flue gas at a predetermined angle, avoiding direct impact of the annular cold exhaust gas on the incoming flue gas, thereby reducing impact on the flow of the incoming flue gas, and reducing collision loss between introduced gas and the incoming flue gas. As shown in FIG. 3, FIG. 3 is a front view (an annular cold exhaust gas branch pipe is not shown in the figure) illustrating a flue gas mixing device according to an embodiment. An air branch pipe 32 is arranged on the annular cavity 3, and an electric valve 33 is installed at a bottom of the air branch pipe 32 to control the air branch pipe 32 to perform air intake. An oxygen content monitor 14 is arranged on a top of the flue exit section 12 to monitor oxygen content in the mixed flue gas in real time, and a probe of the oxygen content monitor 14 extends to a center position of the flue exit section 12 to ensure that the oxygen content of the mixed flue gas may be measured more accurately. The flue gas mixing device is further provided with a control assembly 34. The oxygen content monitor 14 is electrically connected to the control assembly 34, The oxygen content monitor 14 feeds back the detected oxygen content to the control assembly 34, and the control assembly 34 adjusts an opening degree of the electric valve 33 in the air branch pipe 32 to ensure a sufficient supply of oxygen for sintering. In one embodiment, in order to reduce heat loss during the flue gas circulation process, an outside of the main body of the flue gas mixing device performs thermal insulation treatment, and the opening degree of the electric valve 33 of the air branch pipe 32 is adjusted in a timely manner. A diameter of the flue exit section 12 is greater than a diameter of the flue entrance section 11, and an ash hopper 13 is arranged at a bottom of the flue exit section 12, so as to collect part of the dust settled by gravity due to the increase of the pipe diameter and the decrease of the flow velocity after the mixed flue gas passing through the flaring section 23, thereby effectively avoiding the ash accumulation in the flue and abrasion of the flue.
As shown in FIGS. 2 and 3, an included angle between an axis of the air inlet holes 221 and an axis of the throat section 22 is within a range from 20° to 90°. An included angle between an axis of the annular cold exhaust gas branch pipe 31 and the axis of the throat section 22 is within a range from 15° to 75°. And an included angle between an axis of the air branch pipe 32 and the axis of the throat section 22 is within a range from 30° to 90°. By obliquely setting the air intake structure for the introduced gas, the direct impact of the introduced gas on the incoming flue gas may be avoided, and at the same time, drainage effect on the incoming flue gas may be performed, the uniformity and stability of the flow field of the flue gas main channel is maintained, and the collision loss between the introduced gas and the incoming flue gas is reduced. And the annular cold exhaust gas branch pipe 31 is obliquely inserted into the annular cavity 3 at a certain angle, making it easier for the annular cold exhaust gas branch pipe 31 to be in communication with the annular cavity 3.
FIG. 4 is a process flow schematic diagram illustrating a sintering flue gas circulation process according to an embodiment, and as shown in FIGS. 2 to 4, the working principle of the sintering flue gas circulation process is as follows.
Raw materials are sintered in a sintering machine 3b, and the sintered hot ore discharged by the sintering machine 3b is cooled by an annular cooling machine 1 and then generates annular cold exhaust gas. And the annular cold exhaust gas and the circulating flue gas taken from a head and a tail of the sintering machine 3b and pressurized by a sintering circulation fan 41 jointly enter the flue gas mixing device, and enter the sintering machine 3b through a flue gas sealing cover 3a located on a machine head of the sintering machine 3b. Most of the flue gas (non-circulating flue gas) generated by the sintering machine 3b passes through a dust collector 4 and is sent to a desulfurization tower 5 and a chimney 6 after being pressurized by a main sintering fan 42, and is finally discharged.
In the present embodiment, after being pressurized by the sintering circulation fan 41, the circulating flue gas flows through the flue gas mixing device mainly formed of a classic venturi tube structure, and may generate negative pressure at the throat section 22. The annular cold exhaust gas is pushed by an original blower (not shown in the figure) of the annular cooling machine 1 to enter the annular cavity 3 from the annular cold exhaust gas branch pipe 31, and is sucked into the incoming flue gas in the throat section 22 via the air inlet holes 221 under the negative pressure, and the introduced annular cold exhaust gas is fully mixed with the incoming flue gad by using the pressure difference between the two fluids. Compared with the sintering flue gas circulation process in the related art, the present embodiment may effectively realize sufficient mixing of the annular cold exhaust gas and the circulating flue gas without the annular cold circulation fan 11, and may also effectively homogenize composition and temperature of the flue gas in the sintering flue gas circulation process, and stabilize the flow rate of the flue gas. In addition, the air branch pipe 32 obliquely arranged on the throat section 22 may also adjust and replenish air at any time according to the change of the oxygen content in the flue exit section 12 after the mixing.
FIG. 5 is a flowchart illustrating a flue gas mixing method according to an embodiment, and as shown in FIG. 5, the flue gas mixing method includes steps 110 to 130.
In step 110, the flue gas is introduced to the flue entrance section.
In step 120, the annular cold exhaust gas is introduced to the annular cold exhaust gas branch pipe.
In step 130, the annular cold exhaust gas is mixed with the flue gas to form a mixed gas, after passing through the annular cavity and the air inlet holes in sequence.
In one embodiment, the flue gas mixing method further includes monitoring oxygen content of the mixed gas; and adjusting an amount of intake air entering the annular cavity in real time according to the oxygen content.

INDUSTRIAL APPLICABILITY

The flue gas mixing device of the present disclosure solves the problems of high energy consumption and poor flue gas mixing effect of the flue gas mixing device in the related art.

Claims

A flue gas mixing device, comprising:
a flue entrance section (11);

a throat section (22), wherein a plurality of air inlet holes (221) are circumferentially arranged on a side wall of the throat section (22);

an annular cavity (3), arranged on an outer periphery of the throat section (22);

an annular cold exhaust gas branch pipe (31), connected to the annular cavity (3);

a flue exit section (12);

a necking section (21), connected between the flue entrance section (11) and the throat section (22); and

a flaring section (23), connected between the throat section (22) and the flue exit section (12).
The flue gas mixing device of claim 1, wherein an included angle between an axis of the air inlet holes (221) and an axis of the throat section (22) is in a range from 20° to 90°.
The flue gas mixing device of claim 1, wherein an included angle between an axis of the annular cold exhaust gas branch pipe (31) and an axis of the throat section (22) is in a range from 15° to 75°.
The flue gas mixing device of claim 3, wherein a cross-section of the annular cavity (3) has a trapezoidal structure, and a corner of the trapezoidal structure has an arc-shaped transition surface.
The flue gas mixing device of claim 1, further comprising an air branch pipe (32) and a control assembly (34), wherein an included angle between an axis of the air branch pipe (32) and an axis of the throat section (22) is in a range from 30° to 90°; and the air branch pipe (32) comprises an electric valve (33), and the electric valve (33) is electrically connected to the control assembly (34).
The flue gas mixing device of claim 5, further comprising an oxygen content monitor (14) arranged on the flue exit section (12), wherein the oxygen content monitor (14) is electrically connected to the control assembly (34).
The flue gas mixing device of claim 6, further comprising an ash hopper (13) arranged at a bottom of the flue exit section (12).
The flue gas mixing device of any one of claims 1 to 7, wherein a diameter of the flue exit section (12) is greater than a diameter of the flue entrance section (11).
A flue gas mixing method using a flue gas mixing device of any one of claims 1 to 8, comprising:
introducing flue gas to a flue entrance section (11);

introducing annular cold exhaust gas to an annular cold exhaust gas branch pipe (31); and

mixing the annular cold exhaust gas with the flue gas form to a mixed gas, after the annular cold exhaust gas passing through an annular cavity (3) and air inlet holes (211) in sequence.
The flue gas mixing method of claim 9, further comprising: after the mixing the annular cold exhaust gas with the flue gas,
monitoring oxygen content of the mixed gas; and
adjusting an amount of intake air entering the annular cavity (3) in real time according to the oxygen content.