Denitration flue gas waste heat utilization device with self-cleaning function on ammonium salt deposition heat exchange surface

Abstract

The utility model provides a denitration flue gas waste heat utilization device with a self-cleaning function on an ammonium salt deposition heat exchange surface, which comprises a plurality of flue gas heat collector modules which are adjacently arranged in parallel and are used for cooling flue gas, each flue gas heat collector module mainly comprises a heat exchange pipe, the heat exchange pipe in each module is provided with an independent valve, and the heat exchange pipe in each module is provided with an independent valve. The flow of a heat exchange medium in the heat exchange tube is controlled; the flue gas heat collector modules are arranged in a flue where denitration flue gas flows, and all the modules are sequentially arranged in parallel in a stacked mode in the windward side direction of the flue. According to the flue gas heat removal module, the inlet and outlet of the heat exchange medium in the heat exchange tube are controlled through the valve, and when the heat exchange medium stops flowing, ammonium salt on the outer surface of the heat exchange tube is melted through high temperature of flue gas, so that the self-cleaning purpose is achieved. Each module is independently arranged, and when the heat exchange medium flow of any module is independently closed, the influence on the overall outlet temperature of the flue gas is very small; the valve can be opened and closed through automatic control, operation is simple and easy, the labor intensity is relieved, and the service life is prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of denitrification flue gas waste heat utilization, and particularly relates to a denitrification flue gas waste heat utilization device with a self-cleaning function for an ammonium salt deposition heat exchange surface. Background Art

[0002] According to environmental protection requirements, industrial flue gas in most industries must be denitrated to remove nitrogen oxides. The most commonly used process with the highest denitrification efficiency is medium-temperature denitrification, which is to allow flue gas at a temperature of 350-380°C to enter the denitrification device. Medium-temperature denitrification is generally an ammonia method, that is, ammonia gas, ammonia water, or urea and other ammonia-containing substances are sprayed into the flue gas. Through the action of the catalyst, the ammonia substances and the nitrogen oxides in the flue gas react chemically. However, most industrial flue gases also contain SO 2 、SO 3 However, the amount of ammonia in the denitrification process cannot be absolutely accurate, and there are factors such as ammonia escape, which causes excess ammonia and SO in the flue gas after denitrification. 2 、SO 3 A chemical reaction occurs to produce ammonium sulfate (NH 4)2 SO 4 and ammonium bisulfate NH 4 HSO 4 , commonly known as ammonium salt.

[0003] Ammonium bisulfate, with a melting point of 147°C and a boiling point of 350°C, is a colorless crystal soluble in water. It is acidic and can react with alkali to produce ammonia gas. When heated, ammonium bisulfate will decompose to produce ammonium sulfate and ammonia gas.

[0004] Ammonium sulfate, melting point 230-280℃, has a certain solubility in water and is acidic.

[0005] When a heat exchanger is used to utilize waste heat from the flue gas after denitrification, the heat exchange surface is easily adhered to by a mixture of ammonium bisulfate, ammonium sulfate, and dust in the flue gas, which wraps and covers the heat exchange surface, affecting the heat exchange efficiency. In severe cases, it will block the flue gas channel and cause the process equipment to stop operating.

[0006] At present, the common method for treating ammonium salt deposition on the heat exchange surface is to use high-pressure water washing, and hot water is more effective than cold water. However, due to the acidity of ammonium salts, there are still acidic water stains on the surface of the heat exchange tube after washing, which will corrode the metal on the heat exchange surface. Therefore, the presence of ammonium salts brings certain troubles to the use of heat exchange equipment and seriously shortens the service life of heat exchange equipment. Utility Model Content

[0007] Purpose of the utility model: In order to solve the defects of the prior art, the utility model provides a denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface.

[0008] Technical solution: To achieve the above purpose, the utility model adopts the following technical solution:

[0009] A denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface, the waste heat utilization device comprises a plurality of adjacent flue gas heat exchanger modules arranged in parallel, the flue gas heat exchanger modules are mainly composed of heat exchange tubes, and the heat exchange tubes in each module are provided with independent valves to control the flow of heat exchange medium in the heat exchange tubes; the flue gas heat exchanger modules are arranged in a flue where the denitrification flue gas flows, and the modules are arranged in parallel and stacked in sequence in the windward direction of the flue.

[0010] The windward surface refers to the windward section perpendicular to the direction of smoke flow in the flue; the windward surface direction refers to the direction formed by connecting any two points on the windward surface, all of which belong to the windward surface direction; the modules are sequentially connected and stacked in parallel in the windward surface direction of the flue, that is, the windward surfaces of the modules are stacked and spliced ​​together to form the overall windward surface.

[0011] As a specific implementation scheme, the modules are stacked in sequence in the windward direction of the flue to form a group of module groups, and the module groups are arranged in one group or several groups are arranged adjacent to each other in the flue.

[0012] As a specific embodiment, the module groups are arranged in one group, two groups, three groups or four groups in the flue.

[0013] As a specific implementation scheme, the heat exchange tubes in each flue gas heat exchanger module are provided with a heat exchange medium inlet and a heat exchange medium outlet, both of which are connected to an external heat user device; the flow direction of the heat exchange medium is opposite to the flow direction of the denitrification flue gas, forming a countercurrent.

[0014] As a specific implementation scheme, the heat exchange tubes in each flue gas heat exchanger module are connected in parallel and connected to the external heat user device through a header pipe.

[0015] Furthermore, the external heat user device includes an evaporator, an air heater, an economizer or other heat-using devices.

[0016] As a specific implementation scheme, the heat exchange tubes are arranged in a sequential arrangement or a staggered arrangement.

[0017] As a specific implementation, the surface of the heat exchange tube may be a plain tube or may be provided with fins.

[0018] As a specific implementation scheme, the heat exchange medium is selected from heat transfer oil; preferably, the heat exchange medium is selected from T66.

[0019] As a specific implementation scheme, the waste heat utilization device is arranged in the waste heat boiler system of the denitrification process, and is arranged in the flue through which the flue gas after denitrification flows.

[0020] Beneficial effects: Compared with the prior art, the flue gas heat extraction module of the utility model adopts heat exchange tubes, which are small in size, occupy a small area, are light in weight, and are more economical. The inlet and outlet of the heat exchange medium in the heat exchange tubes are controlled by valves. When the heat exchange medium stops flowing, the ammonium salt on the outer surface of the heat exchange tubes is melted by the high temperature of the flue gas to achieve the purpose of self-cleaning. Each module is set separately. When the flow of the heat exchange medium of any module is closed separately, the overall outlet temperature of the flue gas is slightly affected. The valve can be switched on and off through automatic control, which is simple and easy to operate. It does not require manual high-pressure water flushing at the equipment site, which reduces labor intensity and extends the service life of the flue gas waste heat utilization device. The connection method of the heat transfer oil main pipe and the header of each module can be a single row in and out, double row in and out, three rows in and out, four rows in and out, etc., and the design is flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The structure of the waste heat utilization device of the utility model and the arrangement diagram in the flue (two groups of module groups are arranged side by side in the horizontal flue, and one group of module groups includes three superimposed flue gas heat collector modules);

[0022] Figure 2 The structure of the waste heat utilization device of the utility model and its arrangement in the flue (two groups of module groups are arranged side by side in the vertical flue, one group of module groups includes 5 stacked flue gas heat exchanger modules, and each module is provided with a double row of U-shaped heat exchange tubes);

[0023] Figure 3 The structure of the waste heat utilization device of the utility model and the arrangement diagram in the flue (two groups of module groups are arranged side by side in the vertical flue, one group of module groups includes 5 stacked flue gas heat exchanger modules, and a single row of U-shaped heat exchange tubes is arranged in each module);

[0024] Figure 4 This is an application status diagram of the waste heat utilization device of the utility model in a waste heat boiler system. DETAILED DESCRIPTION

[0025] The utility model device is further described below in conjunction with the accompanying drawings.

[0026] In the description of the present utility model, it should be understood that if the terms "upper", "lower", "left", "right", "top", "bottom", "inside", "outside", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. They are only for the convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent.

[0027] Example 1

[0028] A denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface, such as Figure 1 , Figure 2 and Figure 3 As shown, it includes several flue gas heat exchanger modules 1 arranged adjacently in parallel. The flue gas heat exchanger module 1 is mainly composed of a heat exchange tube 11. The heat exchange tube in each module is provided with an independent valve to control the flow of the heat exchange medium in the heat exchange tube; the flue gas heat exchanger module 1 is arranged in the flue where the denitrification flue gas flows, and each module is arranged in parallel and stacked in sequence in the windward direction of the flue to form a group of modules. The module group is arranged in one group or several groups are arranged adjacently in the flue. For example, one group, two groups, three groups or four groups are arranged. The flue can be a horizontal flue or a vertical flue.

[0029] The windward surface refers to the windward section perpendicular to the direction of smoke flow in the flue; the windward surface direction refers to the direction formed by connecting any two points on the windward surface, all of which belong to the windward surface direction; the modules are sequentially connected and stacked in parallel in the windward surface direction of the flue, that is, the windward surfaces of the modules are stacked and spliced ​​together to form the overall windward surface.

[0030] The arrangement of the heat exchange tubes 11 is in a straight row or a cross row, and the surface of the heat exchange tubes 11 can be a plain tube or can also be provided with fins. The heat exchange tubes 11 in each flue gas heat exchanger module 1 are provided with a heat exchange medium inlet 1101 and a heat exchange medium outlet 1102, both of which are connected to an external heat user device; the flow direction of the heat exchange medium is opposite to the flow direction of the denitrification flue gas, and the heat exchange medium is selected from a heat medium heat transfer oil; preferably, it is selected from T66, which is a high-quality heat transfer oil with good thermal stability and low vapor pressure, an operating temperature of 345°C, an autoignition point of 374°C, a normal boiling point of 359°C, and an optimal use temperature range of 0-345°C. The heat exchange tubes 11 in each flue gas heat exchanger module 1 are in parallel and connected to an external heat user device through a header. The connection method between the heat exchange tubes 11 of each module and the header can be a single row in and out, a double row in and out, a triple row in and out, a quadruple row in and out, and other methods. External heat user devices include evaporators, air heaters, economizers or other heat-using devices.

[0031] The working principle of the waste heat utilization device of the utility model is as follows:

[0032] Heat transfer oil (such as T66) is used as a circulating medium to cool the flue gas after denitrification. Direct heat exchange is changed to indirect heat exchange. The original heat exchangers for cooling the flue gas, such as evaporators, air heaters, economizers, etc., are now replaced by flue gas heat exchangers 1. Driven by a circulating pump, the low-temperature heat transfer oil enters the flue gas heat exchanger 1. In the heat exchanger, the flue gas flows through the heat exchange tubes to release heat and cool down before entering the next link. The heat transfer oil flows through the heat exchange tubes to absorb heat and heat up to become high-temperature heat transfer oil. The high-temperature heat transfer oil enters the external heat user (evaporator, air heater, economizer, etc.) to release heat and cool down to become low-temperature heat transfer oil. It enters the flue gas heat exchanger 1 again under the drive of the circulating pump. This cycle achieves the purpose of cooling the flue gas.

[0033] Valves are provided on the heat transfer oil inlet and outlet main pipes of each module. When there are more ammonium salts deposited on the surface of the heat exchange tube 11, the ammonium salt self-cleaning is performed on each module once through the automatic control program in a certain order. Specifically: for the heat exchange surface module that requires self-cleaning, close the valves on the heat transfer oil inlet and outlet pipes. Since T66 has good thermal stability, the 350°C flue gas after denitration outside the heat exchange tube 11 flows through the heat exchange surface, and the heat transfer oil in the tube will not cause problems such as deterioration. After closing the heat transfer oil inlet and outlet valves, the heat transfer oil does not flow, and the flue gas hardly cools down. The ammonium salt deposited on the outer surface of the heat exchange tube 11 can be melted into liquid in a 350°C environment, dripped down, and collected by the collector, which plays a role in cleaning the outer surface of the heat exchange tube 11.

[0034] Due to the modularization, the heat transfer oil in each local module stops flowing, causing the flue gas to almost stop cooling down. The normal operation of the remaining modules has little impact on the overall flue gas outlet temperature.

[0035] When applying specific Figure 4As shown, the above-mentioned waste heat utilization device is arranged in the waste heat boiler system of the denitrification process, and is arranged in the flue through which the flue gas flows after denitrification. For the waste heat boiler system in which the industrial flue gas is cooled from about 1000°C to 180-200°C and the medium-temperature (350-380°C) denitrification process is adopted in the middle, the original cooling process is still adopted for cooling the flue gas before denitrification. For cooling the flue gas after denitrification, a flue gas heat exchanger 1 is arranged at the position of the original evaporator and economizer. In the flue gas heat exchanger 1, the flue gas heats the heat transfer oil. For example, the flue gas is cooled from ~350°C to 200°C, and the heat transfer oil can be heated from 150°C to 280°C. The 280℃ high-temperature heat transfer oil can enter the heat exchange tubes arranged in the boiler drum, so that the boiler drum can be used as the steam-water separation of the evaporator before it is out of stock, and can be used to cool down the high-temperature heat transfer oil and produce steam on the other hand. The cooled ~255℃ heat transfer oil enters the heat transfer oil-feed water heat exchanger (equivalent to the heat transfer oil economizer) for cooling, and the cooled 150℃ low-temperature heat transfer oil is driven by the circulation pump to enter the flue gas heat collector.

[0036] Although the utility model has been described in detail above with general descriptions and specific implementation schemes, it is obvious to those skilled in the art that some modifications or improvements can be made to the utility model. Therefore, these modifications or improvements made without departing from the spirit of the utility model are within the scope of protection claimed by the utility model.

Claims

1. A denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface, characterized in that: The waste heat utilization device comprises a plurality of adjacent flue gas heat exchanger modules (1) arranged in parallel, wherein the flue gas heat exchanger modules (1) are mainly composed of heat exchange tubes (11), and the heat exchange tubes in each module are provided with independent valves to control the flow of heat exchange medium in the heat exchange tubes; the flue gas heat exchanger modules (1) are arranged in a flue where denitrification flue gas flows, and each module is arranged in parallel and stacked in sequence in the windward direction of the flue.

2. The denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The modules are sequentially arranged in parallel and stacked in the windward direction of the flue to form a group of module groups. The module groups are arranged in one group or several groups are arranged adjacent to each other in the flue.

3. The denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 2, characterized in that: The module groups are arranged in one group, two groups, three groups or four groups in the flue.

4. The denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The heat exchange tube (11) in each flue gas heat exchanger module (1) is provided with a heat exchange medium inlet (1101) and a heat exchange medium outlet (1102), both of which are connected to an external heat user device; the flow direction of the heat exchange medium is opposite to the flow direction of the denitrification flue gas, forming a countercurrent.

5. The denitrification flue gas waste heat utilization device with self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The heat exchange tubes (11) in each flue gas heat exchanger module (1) are connected in parallel and connected to an external heat user device via a header pipe.

6. The denitrification flue gas waste heat utilization device with self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 4 or 5, characterized in that: The external heat user device includes an evaporator, an air heater or an economizer.

7. The denitrification flue gas waste heat utilization device with self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The heat exchange tubes (11) are arranged in a sequential arrangement or a staggered arrangement.

8. The denitrification flue gas waste heat utilization device with a self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The surface of the heat exchange tube (11) may be a plain tube or may be provided with fins.

9. The denitrification flue gas waste heat utilization device with self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The heat exchange medium is selected from heat transfer oil.

10. The denitrification flue gas waste heat utilization device with self-cleaning function for the ammonium salt deposition heat exchange surface according to claim 1, characterized in that: The waste heat utilization device is arranged in the waste heat boiler system of the denitration process, and is arranged in the flue through which the flue gas after denitration flows.

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