A combined treatment process for the purification and waste heat recovery of flue gas from two heating furnaces

Abstract

The present invention relates to a combined treatment process for purifying and recovering waste heat of flue gas from two heating furnaces, and the device includes a flue gas purification device, a flue gas induced draft fan, a ground chimney, a combustion air fan, a flue gas remote control valve 1, a flue gas remote control valve 2, a flue gas regulating valve 1, a flue gas regulating valve 2, a pressure gauge 1, a pressure gauge 2, a flue gas bypass pipe 1 and a flue gas bypass pipe 2. The beneficial effects are: the process recovers and purifies the waste heat of the flue gas from the two heating furnaces at the same time, the project investment is low, the land occupation is small, the operating cost is low, and it is of great significance to energy conservation and emission reduction. At the same time, the process integrates flue gas desulfurization, denitrification and dust removal, and the flue gas post-treatment purification measures are complete, meeting the environmental protection emission requirements, and the applicable heating furnace fuel gas has a wide range of types and strong adaptability, and it is easy to implement the upgrading and transformation of newly built or already put into production benzene hydrogenation or other similar chemical equipment.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas treatment, and in particular to a purification and waste heat recovery process for jointly treating flue gas from two heating furnaces. Background Art

[0002] The crude benzene refining (benzene hydrogenation) process uses coking crude benzene as raw material to produce important chemical products such as pure benzene, toluene, and xylene through hydrogenation and distillation. The main reactor heater is required to heat the circulating gas during the hydrogenation process, and the heat source is required to provide a heat source for the bottom of the distillation tower during the distillation process. In many benzene hydrogenation production enterprises, due to the limitations of on-site conditions, there is no heat source medium such as high- and medium-pressure steam in the public and auxiliary conditions. Therefore, in addition to the main reactor heater, a thermal oil heater is also required, that is, thermal oil is used as the heat medium to provide the required heat for distillation.

[0003] The main reactor heater and the thermal oil heater play a very important role in the benzene hydrogenation unit. As the major energy consumers of the production enterprise, their thermal efficiency directly affects the economic benefits of the enterprise, and whether the flue gas emissions meet the environmental protection requirements directly affects the development and survival of the enterprise.

[0004] Benzene hydrogenation production enterprises generally use coke oven gas, blast furnace gas or natural gas as the fuel gas for the heating furnace, and the flue gas after combustion is discharged into the atmosphere. In comparison, the heat load of the thermal oil heating furnace in the benzene hydrogenation unit is nearly 10 times that of the main reactor heating furnace, so its energy consumption and flue gas emissions dominate the benzene hydrogenation unit. In addition, as an organic heat carrier furnace, the thermal oil furnace has rigid regulations and requirements on its thermal efficiency in the national standards.

[0005] In recent years, with the increasingly stringent environmental protection and energy conservation and emission reduction requirements of the state, local governments and enterprises, the existing benzene hydrogenation units are faced with the problem of having to be transformed and upgraded, that is, the existing heating furnaces need to be equipped with supporting facilities for flue gas purification and waste heat recovery, while new benzene hydrogenation units must also consider complete flue gas treatment measures. Summary of the invention

[0006] In order to overcome the defects of the prior art, the technical problem solved by the present invention is to provide a combined purification and waste heat recovery process for the flue gas of two heating furnaces, and the waste heat of the flue gas of the two heating furnaces is recovered and purified at the same time. The project has low investment, small land area, low operating cost, and is of great significance to energy conservation and emission reduction. At the same time, the process integrates flue gas desulfurization, denitrification and dust removal, and the flue gas post-treatment purification measures are complete, meeting the environmental protection emission requirements, and the applicable heating furnace fuel gas has a wide range of types and strong adaptability, and it is easy to implement the upgrading and transformation of newly built or already put into production benzene hydrogenation or other similar chemical equipment.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A process for purifying and recovering waste heat of flue gas from two heating furnaces for joint treatment, wherein the device comprises a flue gas purification device, a flue gas induced draft fan, a ground chimney, a combustion air fan, a flue gas remote control valve 1, a flue gas remote control valve 2, a flue gas regulating valve 1, a flue gas regulating valve 2, a pressure gauge 1, a pressure gauge 2, a flue gas bypass pipe 1 and a flue gas bypass pipe 2, wherein the flue gas purification device comprises a denitration reactor, an air preheater, a desulfurization absorption tower and a bag filter, wherein the denitration reactor, the air preheater, the desulfurization absorption tower and the bag filter are sequentially connected through a flue gas pipe;

[0009] The inlet of the flue gas induced draft fan is connected to the outlet of the flue gas purification device, and the outlet is connected to the ground chimney;

[0010] The inlet of the combustion-supporting air blower is connected to the atmosphere, and the outlet is connected to the air inlet of the air preheater, and the air outlet of the air preheater is connected to the bottom of the thermal oil heating furnace;

[0011] The flue gas remote control valve 1 is arranged on the chimney at the upper part of the thermal oil heating furnace, and a pressure gauge 1 and a flue gas bypass pipe 1 are arranged on the chimney of the thermal oil heating furnace immediately below the flue gas remote control valve, and the other end of the flue gas bypass pipe 1 is connected to the inlet of the flue gas purification device, and a flue gas regulating valve 1 is arranged on the flue gas bypass pipe 1, and the flue gas regulating valve 1 is interlocked with the pressure gauge 1 for control;

[0012] The second flue gas remote control valve is arranged on the chimney at the upper part of the main reactor heating furnace. A second pressure gauge and a second flue gas bypass pipe are arranged on the chimney of the main reactor heating furnace just below the second flue gas remote control valve. The other end of the second flue gas bypass pipe is connected to the first flue gas bypass pipe in front of the flue gas purification device. The second flue gas bypass pipe is provided with a second flue gas regulating valve, and the second flue gas regulating valve is interlocked with the second pressure gauge for control.

[0013] The motor of the flue gas induced draft fan is a variable frequency motor.

[0014] A process for purifying and recovering waste heat from flue gas from two heating furnaces, comprising the following process steps and methods:

[0015] 1) During normal production, the flue gas remote control valve of the upper chimney of the thermal oil heating furnace is closed, and the flue gas generated by the thermal oil heating furnace is led out from the flue gas bypass pipe and enters the denitration reactor in the flue gas purification device. The flue gas denitration adopts the selective catalytic reduction (SCR) process, using NH3 in ammonia water as the reducing agent to reduce NO in the flue gas under the action of the catalyst. X Reduced to harmless N2 and water; A flue gas regulating valve is provided on the flue gas bypass pipe of the thermal oil heating furnace, and is automatically adjusted with the chimney pressure gauge on its upper part to maintain the chimney pressure of the thermal oil heating furnace stable;

[0016] 2) During normal production, the flue gas remote control valve 2 of the upper chimney of the main reactor heating furnace is closed, and the flue gas generated by the main reactor heating furnace is led out through the flue gas bypass pipe 2, and after merging with the flue gas bypass pipe 1 of the thermal oil heating furnace, they enter the denitration reactor in the flue gas purification device together; the flue gas bypass pipe 2 of the main reactor heating furnace is provided with a flue gas regulating valve 2, and it realizes automatic adjustment with the chimney pressure gauge 2 on its upper part to maintain the chimney pressure of the main reactor heating furnace stable;

[0017] 3) The high-temperature flue gas after denitration flows out of the denitration reactor and enters the air preheater to exchange heat with the air sent from the combustion air fan. The heated air flows out of the air preheater and enters the thermal oil heating furnace from the bottom;

[0018] 4) The cooled flue gas flows out of the air preheater and enters the desulfurization absorption tower. The flue gas desulfurization adopts a semi-dry process, using slaked lime Ca(OH)2 as an absorbent to remove harmful gases such as SO2 and SO3 in the flue gas. The desulfurized flue gas enters the bag filter and is filtered to remove dust particles in the flue gas;

[0019] 5) The dust-removed flue gas flows out of the bag filter and enters the flue gas induced draft fan, which draws the flue gas to the chimney on the ground and discharges it into the atmosphere. The flue gas induced draft fan uses a variable frequency motor for variable frequency speed regulation to adapt to the changes in the flue gas volume caused by the changes in production load of the thermal oil heating furnace and the main reactor heating furnace;

[0020] 6) During the start-up and commissioning period, when the flue gas purification device or the flue gas induced draft fan is in an accident state, open the flue gas remote control valve 1 or the flue gas remote control valve 2 on the upper chimney of the thermal oil heating furnace or the main reactor heating furnace, and close the flue gas regulating valve 1 or the flue gas regulating valve 2 on the flue gas bypass pipe 1 or the flue gas bypass pipe 2. In a short period of time, the flue gas will be discharged into the atmosphere through the chimney on the top of the thermal oil heating furnace or the main reactor heating furnace. At this time, the bottom of the thermal oil heating furnace can naturally draw in air to introduce combustion-supporting air.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The waste heat of the flue gas from the two heating furnaces is recovered and purified at the same time, which saves investment, occupies less space and has low operating costs;

[0023] 2) The hot flue gas from the main reactor heating furnace is used together with the high-temperature flue gas produced by the thermal oil heating furnace to preheat the combustion air of the thermal oil heating furnace, which not only simplifies the process flow, but also further increases the temperature of the combustion air of the thermal oil heating furnace, saves the amount of fuel gas, and further increases the thermal efficiency of the thermal oil heating furnace as an organic heat carrier furnace, ensuring that the thermal efficiency of the thermal oil heating furnace far exceeds the national standard requirements for the thermal efficiency of organic heat carrier furnaces;

[0024] 3) The present invention not only effectively recovers and utilizes the waste heat of high-temperature flue gas, but also integrates flue gas desulfurization, denitrification and dust removal, meeting the increasingly stringent national and local environmental protection emission requirements;

[0025] 4) Before the flue gas of the heating furnace is discharged into the atmosphere, since complete post-treatment and purification measures are taken for the flue gas, the heating furnace can use a wide range of fuel gases and has stronger adaptability;

[0026] 5) The device is flexible in production, simple in operation, and reasonably configured. It is easy to implement for new construction or upgrading of existing benzene hydrogenation or other similar chemical plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process principle of the present invention.

[0028] In the figure: 1- thermal oil heating furnace 2- main reactor heating furnace 3- flue gas induced draft fan 4- ground chimney 5- combustion air fan 6- denitration reactor 7- air preheater 8- desulfurization absorption tower 9- bag filter 10- flue gas remote control valve 1 11- flue gas remote control valve 2 12- flue gas regulating valve 1 13- flue gas regulating valve 2 14- pressure gauge 1 15- pressure gauge 2 16- flue gas bypass pipe 1 17- flue gas bypass pipe 2 DETAILED DESCRIPTION

[0029] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0030] See Figure 1 As shown, the present invention relates to a combined treatment process for purifying and recovering waste heat of flue gas from two heating furnaces, wherein the device comprises a flue gas purification device, a flue gas induced draft fan 3, a ground chimney 4, a combustion air fan 5, a flue gas remote control valve 10, a flue gas remote control valve 2 11, a flue gas regulating valve 12, a flue gas regulating valve 2 13, a pressure gauge 14, a pressure gauge 2 15, a flue gas bypass pipe 16 and a flue gas bypass pipe 2 17, wherein the flue gas purification device comprises a denitration reactor 6, an air preheater 7, a desulfurization absorption tower 8 and a bag filter 9, wherein the denitration reactor 6, the air preheater 7, the desulfurization absorption tower 8 and the bag filter 9 are sequentially connected through a flue gas pipeline to realize desulfurization, denitration and dust removal purification of the flue gas, so as to meet the increasingly stringent national and local environmental protection emission requirements;

[0031] The inlet of the flue gas induced draft fan 3 is connected to the outlet of the flue gas purification device, and the outlet is connected to the ground chimney 4;

[0032] The inlet of the combustion air blower 5 is connected to the atmosphere, and the outlet is connected to the air inlet of the air preheater 7. The air outlet of the air preheater 7 is connected to the bottom of the thermal oil heating furnace 1, and the air heated after heat exchange with the high-temperature flue gas is sent into the thermal oil heating furnace 1;

[0033] The flue gas remote control valve 10 is arranged on the chimney at the upper part of the thermal oil heating furnace 1, and a pressure gauge 14 and a flue gas bypass pipe 16 are arranged on the chimney of the thermal oil heating furnace 1 immediately below the flue gas remote control valve 10. The other end of the flue gas bypass pipe 16 is connected to the inlet of the flue gas purification device, and a flue gas regulating valve 12 is arranged on the flue gas bypass pipe 16. The flue gas regulating valve 12 is interlocked with the pressure gauge 14 to realize automatic adjustment of the flue gas pressure.

[0034] The flue gas remote control valve 2 11 is arranged on the chimney at the upper part of the main reactor heating furnace 2, and a pressure gauge 2 15 and a flue gas bypass pipe 2 17 are arranged on the chimney of the main reactor heating furnace 2 immediately below the flue gas remote control valve 2 11. The other end of the flue gas bypass pipe 2 17 is connected to the flue gas bypass pipe 1 16 in front of the flue gas purification device, and the flue gas bypass pipe 2 17 is provided with a flue gas regulating valve 2 13. The flue gas regulating valve 2 13 and the pressure gauge 2 15 are interlocked and controlled to realize automatic adjustment of the flue gas pressure; the flue gas of the main reactor heating furnace 2 and the flue gas of the thermal oil heating furnace 1 are collected and enter the flue gas purification device at the same time, and the combustion air of the thermal oil heating furnace 1 is preheated by the air preheater 7, which not only simplifies the process flow, but also further improves the temperature of the combustion air of the thermal oil heating furnace 1, saves the amount of fuel gas, and further improves the thermal efficiency of the thermal oil heating furnace 1 as an organic heat carrier furnace, ensuring that the thermal efficiency of the thermal oil heating furnace 1 far exceeds the national standard requirements for the thermal efficiency of organic heat carrier furnaces.

[0035] The motor of the flue gas induced draft fan 3 is a variable frequency motor, which can perform variable frequency speed regulation to control the amount of flue gas.

[0036] A process for purifying and recovering waste heat from flue gas from two heating furnaces, comprising the following process steps and methods:

[0037] 1) During normal production, the flue gas remote control valve 10 of the upper chimney of the thermal oil heating furnace 1 is closed, and the flue gas generated by the thermal oil heating furnace 1 is led out through the flue gas bypass pipe 16 and enters the denitration reactor 6 in the flue gas purification device. The flue gas denitration adopts the selective catalytic reduction (SCR) process, using NH3 in ammonia water as the reducing agent to reduce NO in the flue gas under the action of the catalyst. X Reducing to harmless N2 and water; a flue gas regulating valve 12 is provided on the flue gas bypass pipe 16 of the thermal oil heating furnace 1, and is automatically adjusted with the chimney pressure gauge 14 on its upper part to maintain the chimney pressure of the thermal oil heating furnace 1 stable;

[0038] 2) During normal production, the flue gas remote control valve 2 11 of the upper chimney of the main reactor heating furnace 2 is closed, and the flue gas generated by the main reactor heating furnace 2 is led out through the flue gas bypass pipe 2 17, and after merging with the flue gas bypass pipe 1 16 of the thermal oil heating furnace 1, they enter the denitration reactor 6 in the flue gas purification device; the flue gas bypass pipe 2 17 of the main reactor heating furnace 2 is provided with a flue gas regulating valve 2 13, and it realizes automatic adjustment with the upper chimney pressure gauge 2 15 to maintain the chimney pressure of the main reactor heating furnace 2 stable;

[0039] 3) The high-temperature flue gas after denitration flows out of the denitration reactor 6 and enters the air preheater 7 to exchange heat with the air sent from the combustion air blower 5. The heated air flows out of the air preheater 7 and enters the thermal oil heating furnace 1 from the bottom;

[0040] 4) The flue gas after cooling flows out from the air preheater 7 and enters the desulfurization absorption tower 8. The flue gas desulfurization adopts a semi-dry process, using slaked lime Ca(OH)2 as an absorbent to remove harmful gases such as SO2 and SO3 in the flue gas. The flue gas after desulfurization enters the bag filter 9, and the dust particles in the flue gas are removed by filtration;

[0041] 5) The dust-removed flue gas flows out of the bag filter 9 and enters the flue gas induced draft fan 3, and is pumped by the flue gas induced draft fan 3 to the ground chimney 4 for high-altitude discharge into the atmosphere. The flue gas induced draft fan 3 uses a variable frequency motor for variable frequency speed regulation to adapt to the changes in the flue gas volume caused by the changes in the production load of the thermal oil heating furnace 1 and the main reactor heating furnace 2;

[0042] 6) During the start-up and commissioning period, when the flue gas purification device or the flue gas induced draft fan 3 is in an accident state, open the flue gas remote control valve 10 or the flue gas remote control valve 2 11 of the upper chimney of the thermal oil heating furnace 1 or the main reactor heating furnace 2, and close the flue gas regulating valve 12 or the flue gas regulating valve 2 13 on the flue gas bypass pipe 16 or the flue gas bypass pipe 2 17. In a short period of time, the flue gas will be discharged into the atmosphere through the top chimney of the thermal oil heating furnace 1 or the main reactor heating furnace 2. At this time, the bottom of the thermal oil heating furnace 1 can naturally draw in air to introduce combustion-supporting air.

[0043] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for purifying and recovering waste heat of flue gas from two heating furnaces, comprising a flue gas purification device, a flue gas induced draft fan, a ground chimney, a combustion air fan, a flue gas remote control valve 1, a flue gas remote control valve 2, a flue gas regulating valve 1, a flue gas regulating valve 2, a pressure gauge 1, a pressure gauge 2, a flue gas bypass pipe 1 and a flue gas bypass pipe 2, characterized in that: The flue gas purification device is composed of a denitration reactor, an air preheater, a desulfurization absorption tower, and a bag dust collector, wherein the denitration reactor, the air preheater, the desulfurization absorption tower, and the bag dust collector are connected in sequence through a flue gas pipeline; The inlet of the flue gas induced draft fan is connected to the outlet of the flue gas purification device, and the outlet is connected to the ground chimney; The inlet of the combustion-supporting air blower is connected to the atmosphere, and the outlet is connected to the air inlet of the air preheater, and the air outlet of the air preheater is connected to the bottom of the thermal oil heating furnace; The flue gas remote control valve 1 is arranged on the chimney at the upper part of the thermal oil heating furnace, and a pressure gauge 1 and a flue gas bypass pipe 1 are arranged on the chimney of the thermal oil heating furnace immediately below the flue gas remote control valve, and the other end of the flue gas bypass pipe 1 is connected to the inlet of the flue gas purification device, and a flue gas regulating valve 1 is arranged on the flue gas bypass pipe 1, and the flue gas regulating valve 1 is interlocked with the pressure gauge 1 for control; The second flue gas remote control valve is arranged on the chimney at the upper part of the main reactor heating furnace. A second pressure gauge and a second flue gas bypass pipe are arranged on the chimney of the main reactor heating furnace just below the second flue gas remote control valve. The other end of the second flue gas bypass pipe is connected to the first flue gas bypass pipe in front of the flue gas purification device. The second flue gas bypass pipe is provided with a second flue gas regulating valve, and the second flue gas regulating valve is interlocked with the second pressure gauge for control.

2. The device for purifying and recovering waste heat for jointly treating the flue gas of two heating furnaces according to claim 1 is characterized in that: The motor of the flue gas induced draft fan is a variable frequency motor.

3. A process for realizing the device for purifying and recovering waste heat from flue gas of two heating furnaces as claimed in claim 1, characterized in that: The process steps and methods include: 1) During normal production, the flue gas remote control valve of the upper chimney of the thermal oil heating furnace is closed, and the flue gas generated by the thermal oil heating furnace is led out from the flue gas bypass pipe and enters the denitration reactor in the flue gas purification device. The flue gas denitration adopts the selective catalytic reduction (SCR) process, using NH3 in ammonia water as the reducing agent to reduce NO in the flue gas under the action of the catalyst. X Reduced to harmless N2 and water; A flue gas regulating valve is provided on the flue gas bypass pipe of the thermal oil heating furnace, and is automatically adjusted with the chimney pressure gauge on its upper part to maintain the chimney pressure of the thermal oil heating furnace stable; 2) During normal production, the flue gas remote control valve 2 of the upper chimney of the main reactor heating furnace is closed, and the flue gas generated by the main reactor heating furnace is led out through the flue gas bypass pipe 2, and after merging with the flue gas bypass pipe 1 of the thermal oil heating furnace, they enter the denitration reactor in the flue gas purification device together; the flue gas bypass pipe 2 of the main reactor heating furnace is provided with a flue gas regulating valve 2, and it realizes automatic adjustment with the chimney pressure gauge 2 on its upper part to maintain the chimney pressure of the main reactor heating furnace stable; 3) The high-temperature flue gas after denitration flows out of the denitration reactor and enters the air preheater to exchange heat with the air sent from the combustion air fan. The heated air flows out of the air preheater and enters the thermal oil heating furnace from the bottom; 4) The cooled flue gas flows out of the air preheater and enters the desulfurization absorption tower. The flue gas desulfurization adopts a semi-dry process, using slaked lime Ca(OH)2 as an absorbent to remove harmful gases such as SO2 and SO3 in the flue gas. The desulfurized flue gas enters the bag filter and is filtered to remove dust particles in the flue gas; 5) The dust-removed flue gas flows out of the bag filter and enters the flue gas induced draft fan, which draws the flue gas to the ground chimney and discharges it into the atmosphere at high altitude; 6) During the start-up and commissioning period, when the flue gas purification device or the flue gas induced draft fan is in an accident state, open the flue gas remote control valve 1 or the flue gas remote control valve 2, and close the flue gas regulating valve 1 or the flue gas regulating valve 2 on the flue gas bypass pipe 1 or the flue gas bypass pipe 2. In a short period of time, the flue gas will be discharged into the atmosphere from the chimney on the top of the thermal oil heating furnace or the main reactor heating furnace. At this time, the bottom of the thermal oil heating furnace can naturally draw in air to introduce combustion air.

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