阅读说明：本技术 一种提高链箅机回转窑球团中温脱硝效果的系统及方法 (System and method for improving medium-temperature denitration effect of rotary kiln pellets of chain grate machine ) 是由 吴增福 董娜 郑丹阳 郑绥旭 于 2021-08-04 设计创作，主要内容包括：本发明涉及一种提高链箅机回转窑球团中温脱硝效果的系统及方法,包括主要由鼓风干燥段、抽风干燥段、预热Ⅰ段、预热Ⅱ段和下部风箱组成的链箅机,在预热Ⅰ段和预热Ⅱ段之间设有隔墙,球团中温脱硝效果的系统及方法是将隔墙降低至距离箅床表面270mm,将预热Ⅰ段分为前预热Ⅰ段和后预热Ⅰ段,并将后预热Ⅰ段下部的风箱设计成小风箱B,后预热Ⅰ段内的混合热烟气和预热Ⅱ段内的混合热烟气通过后预热Ⅰ段下部的风箱B、预热Ⅱ段风箱C和热风管道Ⅱ送至除尘器、SCR脱硝装置和回热风机,同时通过控制预热Ⅱ段上罩负压低于预热I段上罩负压来控制预热Ⅱ段向预热I段窜风问题,保证了中温SCR脱硝效果,降低单位球团处理烟气燃耗,降低投资及运行费用。(The invention relates to a system and a method for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine, which comprises the chain grate machine mainly consisting of an air blowing drying section, an air draft drying section, a preheating I section, a preheating II section and a lower air box, wherein a partition wall is arranged between the preheating I section and the preheating II section, the medium-temperature denitration effect of the pellets is realized by lowering the partition wall to a distance of 270mm from the surface of a grate bed, dividing the preheating I section into a front preheating I section and a rear preheating I section, designing an air box at the lower part of the rear preheating I section into a small air box B, sending mixed hot flue gas in the rear preheating I section and mixed hot flue gas in the preheating II section to a dust remover, an SCR denitration device and a regenerative fan through the air box B at the lower part of the rear preheating I section, controlling the negative pressure of an upper cover of the preheating II section to be lower than the negative pressure of an upper cover of the preheating I section to control the blow-over from the preheating II section to the preheating I section, the medium-temperature SCR denitration effect is ensured, the fuel consumption of unit pellet treatment flue gas is reduced, and the investment and the operating cost are reduced.)

1. A system for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine comprises the chain grate machine which mainly comprises an air blowing drying section, an air draft drying section, a preheating section I, a preheating section II and air boxes arranged at the lower parts of the air blowing drying section, the air draft drying section, the preheating section I and the preheating section II, wherein a partition wall is arranged between the preheating section I and the preheating section II, and the system is characterized in that the distance between the partition wall and the surface of a grate bed is 270 mm; the preheating I section is divided into a front preheating I section and a rear preheating I section, an air box at the lower part of the front preheating I section is set into a large air box A, an air box at the lower part of the rear preheating I section is designed into a small air box B, the small air box B is adjacent to an air box C at the preheating II section, and an exhaust pipe of the small air box B and the air box C at the preheating II section is respectively connected with a dust remover, an SCR (selective catalytic reduction) denitration device and a heat regeneration fan through a hot air pipeline I;

the exhaust pipe of the large air box A at the lower part of the front preheating section I is connected with the exhaust fan and the desulfurization system through a hot air pipeline II.

2. The system for improving the medium temperature denitration effect of the grate rotary kiln pellets as claimed in claim 1, wherein the width of the large air box A is 3m, and the width of the small air box B is 2 m.

3. A method for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine comprises the steps of adopting the temperature parameters of the existing pellet sintering process, and is characterized by comprising the following steps:

1) the partition wall arranged between the preheating section I and the preheating section II is lowered to be 50mm away from the charge level, so that air blow-by of the partition wall is reduced;

2) designing a small air box B5 at the lower part of a rear preheating I section of the chain grate machine into a 2m air box, designing a large air box A at a front preheating I section into a 3m air box, collecting mixed hot flue gas in the rear preheating I section and mixed hot flue gas in a preheating II section to a hot air pipeline II through the small air box B at the lower part of the rear preheating I section, the air box C at the preheating II section and an exhaust pipe, and sending the mixed hot flue gas to an exhaust drying section in front of the preheating I section of the chain grate machine through a dust remover, an SCR (Selective catalytic reduction) denitration device and a regenerative fan; the denitration rate of the flue gas can reach 90 percent;

the mixed hot flue gas in the front preheating section I is collected to a hot air pipeline I through a large air box A and an exhaust pipe at the lower part of the preheating section I, and is combined with the waste gas from the exhaust drying section and sent to an exhaust fan and a desulfurization system;

3) control preheats II sections upper shield negative pressures and is less than and preheats I section upper shield negative pressure, can control air exhauster operation negative pressure through the air door of adjustment air exhauster or frequency conversion in the operation for it enters into through the partition wall to preheat I section upper shield waste gas and preheats II sections upper shields to reduce anti-wind phenomenon of scurrying.

4. The method for improving the medium temperature denitration effect of the pellets in the rotary kiln of the chain grate machine as claimed in claim 3, wherein the pressure of the upper cover of the preheating section II is-1050 Pa, and the pressure of the upper cover of the preheating section I is-1000 Pa.

Technical Field

The invention belongs to the technical field of grate-kiln flue gas treatment, and particularly relates to a system and a method for improving medium-temperature denitration effect of grate-kiln pellets.

Background

The pellet ore is used as an important charging material for blast furnace iron making, has the advantages of high strength, good metallurgical performance and the like, and compared with a sintering process, the pellet process has lower energy consumption and pollution load, and the pellet ore is more suitable for the condition of iron ore resources mainly comprising concentrate in China, so the pellet ore is an iron ore agglomeration technology which encourages development. With the development of the steel industry, the yield of the pellet ore in China also tends to increase year by year.

The NOx generation in the pellet production process mainly comes from two forms of fuel type and thermal type, and although the NOx generation amount in the grate-kiln pellet production process can be reduced by reducing the pellet yield, namely reducing the coal gas or coal powder injection amount, reducing the pellet strength requirement, namely reducing the rotary kiln temperature, and adopting measures of raw materials and fuels with lower NOx and the like, the NOx generation amount is difficult to meet the environment-friendly requirement of ultralow emission.

Currently, the preferred NOx removal technology relies primarily on Selective Catalytic Reduction (SCR) technology to remove NOx at the end and in the process. For SNCR denitration techniques, a temperature range of 800 ℃ to 1100 ℃ is generally considered to be suitable. In the production process of the grate-rotary kiln pellets, an SNCR denitration technology is applied, and the flue gas denitration is usually carried out by spraying a reducing agent (ammonia water or urea) into the flue gas at a preheating section (the temperature is 850-1100 ℃). However, due to the fact that the air channeling phenomenon exists between the preheating I section and the I section of the adjacent air box, the content of NOx in the preheating I section of the rear section of the air box is high, and if the NOx is directly discharged, accurate denitration control and standard NOx emission are difficult to achieve. In addition, the partition wall between the preheating section I and the preheating section II of the prior chain grate machine is 1000mm away from the charge level, so that a large amount of flue gas in the preheating section II enters the preheating section I to cause air channeling.

Along with the gradual increase of environmental protection, the flue gas denitration technology also gradually progresses. Generally, the flue gas is treated by treating the tail gas. In this case, desulfurization is required before denitration. The flue gas temperature after desulfurization is reduced by a large extent, and is not suitable for low-temperature SCR denitration, so that the flue gas needs to be heated again, and the energy waste and the equipment investment are increased. In addition, the flue gas entering the tail gas is composed of at least two parts, wherein one part contains nitrogen oxides, and the other part does not contain nitrogen oxides. If a tail denitration process is adopted, the two parts of mixed flue gas need to be treated. The main problems of the treatment mode are as follows: 1) the flue gas treatment amount is large; 2) the primary investment is high; 3) the operation cost is high.

Disclosure of Invention

The invention aims to provide a system and a method for improving the medium-temperature denitration effect of rotary kiln pellets of a chain grate machine, which have good denitration effect and low operation cost.

The invention relates to a system for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine, which comprises the chain grate machine mainly comprising an air blowing drying section, an air draft drying section, a preheating section I, a preheating section II and air boxes arranged at the lower parts of the air blowing drying section, the air draft drying section, the preheating section I and the preheating section II, wherein a partition wall is arranged between the preheating section I and the preheating section II, and the system is characterized in that the distance between the partition wall and the surface of a grate bed is 270 mm; the preheating I section is divided into a front preheating I section and a rear preheating I section, an air box at the lower part of the front preheating I section is set into a large air box A, an air box at the lower part of the rear preheating I section is designed into a small air box B, the small air box B is adjacent to an air box C at the preheating II section, and an exhaust pipe of the small air box B and the air box C at the preheating II section are respectively connected with a dust remover, an SCR (selective catalytic reduction) denitration device and a heat regeneration fan through a hot air pipeline I;

the exhaust pipe of the large air box A at the lower part of the front preheating section I is connected with the exhaust fan and the desulfurization system through a hot air pipeline II.

Preferably, the width of the large wind box A is 3m, and the width of the small wind box B is 2 m.

The invention relates to a method for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine, which comprises the following steps of adopting the temperature parameters of the existing pellet sintering process:

1) the partition wall arranged between the preheating section I and the preheating section II is lowered to be 50mm away from the charge level, so that air blow-by of the partition wall is reduced;

2) designing a small air box B at the lower part of a rear preheating I section of the chain grate machine into a 2m air box, designing a large air box A at the front preheating I section into a 3m air box, collecting mixed hot flue gas in the rear preheating I section and mixed hot flue gas in a preheating II section to a hot air pipeline II through the small air box B at the lower part of the rear preheating I section, the air box C at the preheating II section and an exhaust pipe, and sending the mixed hot flue gas to an exhaust drying section before the preheating I section of the chain grate machine through a dust remover, an SCR (selective catalytic reduction) denitration device and a heat return fan; the denitration rate of the flue gas can reach 90 percent;

the mixed hot flue gas in the front preheating section I is collected to a hot air pipeline I through a large air box A and an exhaust pipe at the lower part of the preheating section I, and is combined with the waste gas from the exhaust drying section and sent to an exhaust fan and a desulfurization system;

3) the negative pressure of the upper cover of the preheating section II is controlled to be lower than that of the upper cover of the preheating section I, so that waste gas of the upper cover of the preheating section I enters the upper cover of the preheating section II through the partition wall, and the phenomenon of reverse air blow-by is reduced.

The negative pressure of the upper cover of the preheating section II is-1050 Pa, and the pressure of the upper cover of the preheating section I is-1000 Pa.

The invention has the advantages that:

1) the air mixing from the preheating section II to the preheating section I can be effectively controlled;

2) the new construction or the modification is easy to realize, and the investment is small;

3) the production operation is easy to realize;

4) the medium-temperature denitration effect is good, the height of the partition wall is reduced, the mixed hot flue gas containing NOx in the post-preheating section I and the mixed hot flue gas in the preheating section II are sent to the dust remover, the SCR denitration device and the regenerative fan together, the flue gas denitration rate can reach over 90 percent, the pollution is reduced, the medium-temperature denitration effect of the pellets and the quality of the pellets are improved, and the difficulty and the cost of subsequent flue gas treatment are greatly reduced.

Drawings

FIG. 1 is a schematic diagram of a system for improving the medium-temperature denitration SCR effect of the rotary kiln pellets of the chain grate machine.

Detailed Description

The following describes embodiments of the present invention with reference to the drawings.

As shown in figure 1, the invention relates to a system for improving the medium temperature denitration effect of pellets in a rotary kiln of a chain grate machine, which comprises the chain grate machine mainly consisting of an air blowing drying section, an air draft drying section, a preheating section I, a preheating section II and air boxes arranged at the lower parts of the air blowing drying section, the air draft drying section, the preheating section I and the preheating section II, wherein a partition wall 3 is arranged between the preheating section I2 and the preheating section II 1, and the system is characterized in that the distance between the partition wall 3 and the surface 12 of a grate bed is 270 mm; the thickness of the charge level is generally 220mm, so that the distance between the partition wall 3 and the charge level can be said to be 50 mm.

The preheating I section is divided into a front preheating I section and a rear preheating I section, an air box at the lower part of the front preheating I section is set to be a large air box A, an air box at the lower part of the rear preheating I section is designed to be a small air box B, the width of the large air box A is 3m, the width of the small air box B is 2m, the small air box B is adjacent to an air box C6 at the preheating II section, and the air box B and an exhaust pipe of an air box C6 at the preheating II section are respectively connected with a dust remover, an SCR denitration device and a heat regeneration fan through a hot air pipeline I10;

the exhaust pipe of a large air box A4 at the lower part of the front preheating section I is connected with an exhaust fan and a desulfurization system through a hot air pipeline II 11.

The invention relates to a method for improving the medium-temperature denitration effect of pellets in a rotary kiln of a chain grate machine, which comprises the following steps of adopting the temperature parameters of the existing pellet sintering process:

1) the partition wall 3 arranged between the preheating I section 2 and the preheating II section 1 is lowered to be 50mm away from the charge level, so that air channeling of the partition wall 3 is reduced;

2) the small air box B5 at the lower part of the rear preheating section I of the chain grate machine is designed into a 2m air box, the large air box A4 at the front preheating section I is designed into A3 m air box, the mixed hot flue gas in the rear preheating section I and the mixed hot flue gas in the preheating section II are converged to a hot air pipeline I10 through the small air box B5 at the lower part of the rear preheating section I, the air box C6 at the preheating section II and an exhaust pipe, and then are sent to an exhaust drying section before the chain grate machine preheating section I through a dust remover 9, an SCR denitration device 8 and a regenerative fan 7; the denitration rate of the flue gas can reach 90 percent, and the difficulty and the cost of subsequent flue gas treatment are greatly reduced;

the mixed hot flue gas in the front preheating section I is collected to a hot air pipeline II 11 through a large air box A4 at the lower part of the preheating section I and an exhaust pipe, and is combined with the waste gas from the exhaust drying section and sent to an exhaust fan and a desulfurization system; not shown in the figures;

3) the negative pressure of the upper cover of the preheating section II 1 is controlled to be lower than the negative pressure of the upper cover of the preheating section I2, the operation of the exhaust fan can be controlled by adjusting an air door or a frequency converter of the exhaust fan, the pressure of the upper cover of the preheating section II is-1050 Pa, the pressure of the upper cover of the preheating section I is-1000 Pa, and the phenomenon of reverse air blow-by is reduced as much as possible.

In the operation process, when the negative pressure of the upper cover of the preheating section II is slightly lower than the negative pressure of the upper cover of the preheating section I for a short time, a small amount of waste gas containing NOx enters the post-preheating section I (about 3%) through the partition wall 3, the air box of the post-preheating section I of the chain grate machine is designed to be a small air box B5, at the moment, the temperature of mixed gas containing NOx in the post-preheating section I can reach 290-300 ℃, a small amount of mixed hot flue gas containing NOx in the post-preheating section I and the mixed hot flue gas in the preheating section II are converged to a hot air pipeline II 10 together, the denitration rate of the flue gas can reach more than 90% after passing through a dust remover and an SCR denitration device, and the flue gas is sent to an air draft drying section of the chain grate machine through a regenerative fan, so that the pollution is reduced, and the medium temperature denitration effect of the pellets and the quality of the pellets are improved.