CN111203096B - A urea hydrolysis gas capture and energy-saving reheating device - Google Patents
A urea hydrolysis gas capture and energy-saving reheating device Download PDFInfo
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- CN111203096B CN111203096B CN202010124586.8A CN202010124586A CN111203096B CN 111203096 B CN111203096 B CN 111203096B CN 202010124586 A CN202010124586 A CN 202010124586A CN 111203096 B CN111203096 B CN 111203096B
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- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 104
- 239000004202 carbamide Substances 0.000 title claims abstract description 104
- 238000003303 reheating Methods 0.000 title claims abstract description 79
- 238000006460 hydrolysis reaction Methods 0.000 title claims abstract description 58
- 230000007062 hydrolysis Effects 0.000 title claims abstract description 51
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 80
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 40
- 229920006395 saturated elastomer Polymers 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000003466 welding Methods 0.000 claims description 3
- 230000003301 hydrolyzing effect Effects 0.000 claims 1
- 238000005260 corrosion Methods 0.000 abstract description 6
- 230000007797 corrosion Effects 0.000 abstract description 6
- 239000007789 gas Substances 0.000 description 125
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 16
- 238000000034 method Methods 0.000 description 11
- 239000012071 phase Substances 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 239000003546 flue gas Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010992 reflux Methods 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/005—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by heat treatment
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/08—Preparation of ammonia from nitrogenous organic substances
- C01C1/086—Preparation of ammonia from nitrogenous organic substances from urea
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
- F28D7/10—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged one within the other, e.g. concentrically
- F28D7/103—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged one within the other, e.g. concentrically consisting of more than two coaxial conduits or modules of more than two coaxial conduits
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
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- Environmental & Geological Engineering (AREA)
- Thermal Sciences (AREA)
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- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
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Abstract
本发明公开了一种尿素水解气体捕集及节能再热装置，包括：气体捕集单元布置在尿素水解器的上部气相空间内并伸出尿素水解器与供氨管道或再热单元相连；再热单元包括壳体和设置在壳体内的蒸汽盘管，壳体设置在供氨管道中或者通过产品气入口与气体捕集单元相连且通过产品气出口与供氨管道相连，蒸汽盘管的蒸汽入口与蒸汽源相连且蒸汽出口与尿素水解器的蒸汽入口相连；减温减压单元设置在蒸汽盘管的蒸汽出口与尿素水解器的蒸汽入口之间的管路上。本发明能快速收集尿素水解器内的产品气体并充分利用过热蒸汽的热量对产品气体进行再加热并提高产品气体的温度，避免产品气体在输送过程中出现温度过低导致管道系统堵塞和腐蚀等问题，提高可靠性和经济性。
The present invention discloses a urea hydrolysis gas capture and energy-saving reheating device, comprising: a gas capture unit arranged in the upper gas phase space of a urea hydrolyzer and extending out of the urea hydrolyzer to be connected to an ammonia supply pipeline or a reheating unit; the reheating unit comprises a shell and a steam coil arranged in the shell, the shell is arranged in the ammonia supply pipeline or connected to the gas capture unit through a product gas inlet and connected to the ammonia supply pipeline through a product gas outlet, the steam inlet of the steam coil is connected to a steam source and the steam outlet is connected to the steam inlet of the urea hydrolyzer; a temperature reduction and pressure reduction unit is arranged on the pipeline between the steam outlet of the steam coil and the steam inlet of the urea hydrolyzer. The present invention can quickly collect the product gas in the urea hydrolyzer and make full use of the heat of the superheated steam to reheat the product gas and increase the temperature of the product gas, so as to avoid problems such as blockage and corrosion of the pipeline system caused by too low temperature of the product gas during transportation, thereby improving reliability and economy.
Description
Technical Field
The invention relates to the technical field of environmental protection, in particular to a urea hydrolysis gas trapping and energy-saving reheating device.
Background
The urea hydrolysis ammonia production technology has the characteristics of low energy consumption, simple process system and easy implementation, and is widely applied to flue gas denitration engineering of power plants. The urea hydrolysis principle is that a heat source is utilized to heat urea solution with certain mass concentration to more than 140 ℃, and under the temperature condition, urea undergoes hydrolysis reaction to generate gaseous NH 3 and CO 2, so as to provide a reducing agent (NH 3) for a flue gas denitration system. The urea hydrolysis reaction generally takes place in a closed shell-and-tube pressure vessel (urea hydrolysis reactor), the urea solution running on the shell side, the steam running on the tube side being heated, and heat being transferred through the tube wall. The product gas generated by the urea hydrolysis reaction is conveyed to a denitration system through a pipeline. The heating steam source generally adopts medium-low pressure auxiliary steam which is easily obtained by a power plant, and in order to fully utilize the latent heat energy of the steam and improve the heat transfer efficiency, the auxiliary steam is generally required to be firstly reduced in temperature and pressure to be saturated steam and then enter the hydrolysis reactor.
The conventional urea hydrolysis ammonia production system of a power plant is usually connected with auxiliary steam of 0.8-1.2 MPa and 300 ℃, is subjected to temperature and pressure reduction to saturated steam of 0.7-0.8 MPa and 170-180 ℃ and then is introduced into a hydrolysis reactor to heat urea solution to 140-160 ℃ so as to reach the optimal temperature range required by urea hydrolysis. Under certain temperature and pressure conditions, urea undergoes hydrolysis reaction to generate ammonia-containing product gas with the pressure of 0.4-0.6 MPa and the temperature of 140-160 ℃, the product gas is gathered in a gas phase space at the upper part of the hydrolyzer, and is conveyed to an SCR denitration ammonia spraying system through a factory pipeline by an interface at the top of the hydrolyzer. The temperature and pressure reduction of auxiliary steam is generally carried out by adopting a simpler and economical booster pump to spray water for cooling.
The conventional technology has the main problems that on one hand, auxiliary steam at the temperature of about 300 ℃ is cooled to saturated steam at the temperature of 170-180 ℃ through water spraying and then is reused, a large amount of heat energy is wasted, on the other hand, the temperature of 140-160 ℃ urea hydrolysis product gas is reduced due to heat loss in the process of conveying the urea hydrolysis product gas to an SCR denitration region through a plant pipeline, when the temperature is too low (lower than 140 ℃), water steam is easy to reflux in the pipeline, NH 3 and CO 2 are polymerized again to generate corrosive polymers, serious blockage and corrosion are caused on a pipeline system, and normal ammonia supply of the system and normal operation of an SCR denitration device are influenced.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the urea hydrolysis gas trapping and energy-saving reheating device which can fully utilize the heat of the superheated steam to further improve the temperature of the urea hydrolysis product gas so as to reduce the blockage and corrosion risks of an ammonia supply conveying pipeline system, save energy consumption and improve the operation reliability of the system.
The invention provides a urea hydrolysis gas trapping and energy-saving reheating device which comprises a gas trapping unit, a reheating unit and a temperature and pressure reducing unit, wherein the gas trapping unit is arranged in an upper gas phase space of a urea hydrolyzer and extends out of the urea hydrolyzer to be connected with an ammonia supply pipeline or the reheating unit, the reheating unit comprises a shell and a steam coil pipe arranged in the shell, the shell is arranged in the ammonia supply pipeline or connected with the gas trapping unit through a product gas inlet and connected with the ammonia supply pipeline through a product gas outlet, a steam inlet of the steam coil pipe is connected with a steam source, a steam outlet of the steam coil pipe is connected with a steam inlet of the urea hydrolyzer, and the temperature and pressure reducing unit is arranged on a pipeline between the steam outlet of the steam coil pipe and the steam inlet of the urea hydrolyzer.
According to one embodiment of the inventive urea-hydrolyzing gas capturing and energy saving reheat device, the gas capturing unit is a T-shaped pipe assembly and comprises a longer collecting pipe arranged axially along the urea-hydrolyzing device and a shorter exhaust pipe arranged radially along the urea-hydrolyzing device.
According to one embodiment of the urea hydrolysis gas trapping and energy-saving reheating device, a plurality of groups of gas collecting holes are arranged on the lower surface of the collecting pipe at intervals, each group of gas collecting holes are uniformly distributed along the radial direction of the collecting pipe, two ends of the collecting pipe are plugged by end covers, and the exhaust pipe extends out of a urea hydrolyzer shell and is connected with an ammonia supply pipeline or a reheating unit.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, a flow equalizing plate is arranged at a product gas inlet of a shell in the reheating unit, is an orifice plate uniformly provided with a plurality of small holes and is arranged on the whole cross section of the shell of the reheating unit.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, when the shell of the reheating unit is connected with the gas capturing unit through the product gas inlet and connected with the ammonia supply pipeline through the product gas outlet, the shell of the reheating unit is connected with the shell of the urea hydrolyzer through a flange or through welding, the central line of the shell of the reheating unit is opposite to the central line of the exhaust pipe, and the diameter of the shell of the reheating unit is larger than that of the exhaust pipe.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, when the shell of the reheating unit is arranged in the ammonia supply pipeline, two ends of the shell of the reheating unit are connected with the ammonia supply pipeline through the cone section or the end socket opening.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, the steam coil is a serpentine coil, a spiral coil, a U-shaped coil or a tubular coil, and the ammonia supply pipeline is connected with the SCR denitration system.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, the steam source is auxiliary heating steam of a power plant at 0.8-1.2 MPa and at-300 ℃, and the steam passing through the reheating unit and the temperature and pressure reducing unit is saturated steam at 0.7-0.8 MPa and at 170-180 ℃.
According to one embodiment of the urea hydrolysis gas capturing and energy-saving reheating device, the temperature of the product gas output by the gas capturing unit is 140-160 ℃, and the temperature of the product gas after passing through the reheating unit is 180-200 ℃.
Compared with the prior art, the urea hydrolysis product gas trapping and energy-saving reheating device can rapidly collect product gas in the urea hydrolyzer and fully utilize the heat of superheated steam to reheat the product gas so as to further improve the temperature of the product gas, avoid the problems of blockage and corrosion of a pipeline system caused by low temperature of the product gas in the process of being conveyed to an SCR denitration zone, reduce the steam heat loss and the water consumption of a steam temperature and pressure reducing device, and improve the reliability and economical efficiency of system operation.
Drawings
Fig. 1 shows a schematic diagram of the urea hydrolysis product gas capturing and energy saving reheat device according to an exemplary embodiment of the present invention.
Fig. 2 shows a schematic side view of the structure of the collection pipe of the gas capturing unit in the urea hydrolysis product gas capturing and energy saving reheating device according to an exemplary embodiment of the present invention.
Fig. 3 shows a schematic structural view of a flow equalizing plate of a reheat unit in a urea hydrolysis product gas trapping and energy saving reheat device according to an exemplary embodiment of the present invention.
Reference numerals illustrate:
the device comprises a 1-gas capturing unit, a 11-collecting pipe, a 12-end cover, a 13-exhaust pipe, a 2-reheating unit, a 21-shell, a 22-flow equalizing plate, a 23-steam coil pipe, a 24-steam inlet, a 25-steam outlet, a 26-product gas outlet and a 3-temperature and pressure reducing unit.
Detailed Description
All of the features disclosed in this specification, or all of the steps in a method or process disclosed, may be combined in any combination, except for mutually exclusive features and/or steps.
Any feature disclosed in this specification may be replaced by alternative features serving the same or equivalent purpose, unless expressly stated otherwise. That is, each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise.
Hereinafter, the urea hydrolysis product gas capturing and energy saving reheating device of the present invention will be described in detail.
Fig. 1 shows a schematic diagram of the urea hydrolysis product gas capturing and energy saving reheat device according to an exemplary embodiment of the present invention.
As shown in fig. 1, the urea hydrolysis product gas capturing and energy-saving reheating device according to an exemplary embodiment of the present invention includes a gas capturing unit 1, a reheating unit 2, and a temperature and pressure reducing unit 3. The gas trapping unit 1 is arranged in the urea hydrolyzer to collect product gas rapidly, the reheating unit 2 heats the product gas by utilizing heat of superheated steam and further increases the temperature of the product gas, and the temperature and pressure reducing unit 3 is used for further reducing the temperature and pressure of the steam after full heat exchange to obtain saturated steam meeting requirements and further heating urea solution.
According to an exemplary embodiment of the invention, the gas capturing unit 1 of the invention is arranged in the upper gas phase space of the urea hydrolyser and extends out of the urea hydrolyser in connection with an ammonia supply pipe or reheat unit 2.
Preferably, the gas capturing unit 1 is a T-shaped pipe assembly and comprises a longer collecting pipe 11 arranged axially along the urea hydrolyzer and a shorter exhaust pipe 13 arranged radially along the urea hydrolyzer.
Fig. 2 shows a schematic side view of the structure of the collection pipe of the gas capturing unit in the urea hydrolysis product gas capturing and energy saving reheating device according to an exemplary embodiment of the present invention. As shown in fig. 2, a plurality of groups of gas collecting holes are arranged on the lower surface of the collecting pipe 11 at intervals, each group of gas collecting holes are uniformly distributed along the radial direction of the collecting pipe 11, and two ends of the collecting pipe are blocked by end covers 12, so that the product gas of urea hydrolysis can be rapidly collected and discharged. The exhaust pipe 13 extends out of the urea hydrolyzer shell and is connected with the ammonia supply pipeline or the reheating unit 2.
Therefore, the product gas generated in the ammonia production process of the urea hydrolyzer continuously escapes from the liquid phase to the gas phase space at the upper part of the urea hydrolyzer, is quickly trapped by the gas collecting holes on the collecting pipe 11 in the gas trapping unit 1, and is discharged into the reheating unit 2 through the exhaust pipe 13.
Compared with the design that the conventional urea hydrolysis product gas is directly discharged to a factory conveying pipeline through an outlet at the top of the urea hydrolyzer, the structural design of the invention can rapidly and uniformly collect and discharge the hydrolysis product gas gathered at the top of the urea hydrolyzer, thereby reducing the adverse effect of the product gas gathering on the urea hydrolysis reaction to the greatest extent and improving the urea hydrolysis efficiency.
The reheating unit 2 of the invention directly introduces auxiliary steam to reheat urea hydrolysis product gas, and specifically comprises a shell 21 and a steam coil 23 arranged in the shell 21, wherein the shell 21 is arranged in an ammonia supply pipeline or connected with the gas capturing unit 1 through a product gas inlet and connected with the ammonia supply pipeline through a product gas outlet 26. That is, the reheating unit 2 may be directly connected to the urea hydrolyzer, or may be separately installed on the ammonia supply pipe away from the urea hydrolyzer body. When installed on top of the urea hydrolyzer, it is desirable to install it vertically, and when installed on the ammonia supply pipe of the product gas outlet, it is desirable to install it horizontally. The steam inlet 24 of the steam coil 23 is connected to a steam source and the steam outlet 25 is connected to a steam inlet of the urea hydrolyzer, whereby the product gas entering the housing 21 of the reheat unit 2 is able to exchange heat sufficiently with the superheated steam flowing in the steam coil 23 to raise the temperature.
Fig. 3 shows a schematic structural view of a flow equalizing plate of a reheat unit in a urea hydrolysis product gas trapping and energy saving reheat device according to an exemplary embodiment of the present invention. As shown in fig. 3, preferably, a flow equalizing plate 22 is provided at the product gas inlet of the casing 21 in the reheating unit 1, and the flow equalizing plate 22 is an orifice plate uniformly provided with a plurality of small holes and is disposed over the entire cross section of the casing 21 of the reheating unit.
When entering the reheating unit 2, the product gas is blocked by the flow equalizing plate 22, the flow velocity is rapidly reduced and spread, and the product gas uniformly enters the shell 21 of the reheating unit through dense small holes on the flow equalizing plate 22. The urea hydrolysis product gas is rectified by the flow equalizing plate and then uniformly heated by the high-temperature steam in the coil pipe to increase the temperature, and when the product gas actually flows through the steam coil pipe 23 in the shell 21, the product gas is heated by the high-temperature steam in the steam coil pipe and the temperature is further increased, and then is discharged to an ammonia supply pipeline through the product gas outlet 26 and is sent to the SCR denitration system.
The diameter and the height of the reheating unit 2 are determined through calculation according to the required heat exchange amount, the steam coil 23 can be in various forms such as a serpentine coil, a spiral coil, a U-shaped coil or a tubular coil, and the heat exchange area is determined to meet the design temperature requirement of the product gas.
When the shell 21 of the reheating unit 2 is connected with the gas capturing unit 1 through the product gas inlet and is connected with the ammonia supply pipeline through the product gas outlet 26, the shell 21 of the reheating unit 2 and the shell of the urea hydrolyzer are connected through flange connection or welding, the center line of the shell 21 of the reheating unit 2 is opposite to the center line of the exhaust pipe 13, and the diameter of the shell 21 of the reheating unit 2 is larger than the diameter of the exhaust pipe 13. When the shell 21 of the reheating unit 2 is arranged in the ammonia supply pipeline, two ends of the shell 21 of the reheating unit 2 are connected with the ammonia supply pipeline through cone sections or seal head openings. Wherein, supply ammonia pipeline and SCR denitration system to carry out the flue gas denitration with product gas delivery.
Compared with the design that the conventional urea hydrolysis product gas is directly discharged to a factory conveying pipeline through an outlet at the top of the hydrolyzer, the structure of the invention fully utilizes the heat of the superheated steam to further improve the temperature of the product gas, can avoid the steam reflux and the generation of polymers in the conveying process of the product gas, reduces the risk of blockage and corrosion of a pipeline system, and improves the stability and reliability of ammonia supply of the system.
The invention also comprises a temperature and pressure reducing unit 3 arranged on the line between the steam outlet 25 of the steam coil 23 and the steam inlet of the urea hydrolyzer. The high-temperature steam in the steam coil 23 is directly connected with auxiliary heating steam (0.8-1.2 MPa, 300 ℃) of a power plant, enters the steam coil 23 through a steam inlet 24 of the steam coil 23, fully exchanges heat with product gas outside the pipe, and is discharged from a steam outlet 25. The exhausted steam still has a certain degree of superheat, and the pressure and temperature of the exhausted steam are further reduced to saturated steam by the temperature and pressure reducing unit 3, and then the saturated steam enters the urea hydrolyzer to heat the urea solution.
The steam source used in the invention is auxiliary heating steam of a power plant at 0.8-1.2 MPa and at the temperature of about 300 ℃, and the steam passing through the reheating unit 2 and the temperature and pressure reducing unit 3 is saturated steam at 0.7-0.8 MPa and at 170-180 ℃. The temperature of the product gas output by the gas trapping unit 1 is 140-160 ℃, and the temperature of the product gas after passing through the reheating unit 2 is 180-200 ℃.
Compared with the conventional technology that auxiliary steam is directly led to spray water, reduce temperature and pressure and then is sent into a urea hydrolyzer to heat urea solution, the technology of the invention fully utilizes the heat of the auxiliary steam to improve the temperature of hydrolysis product gas and then reduces the temperature and pressure, thereby reducing the heat loss of the steam and saving energy consumption. Meanwhile, the steam temperature entering the temperature and pressure reducing device is reduced, so that the water consumption of the water spraying pump is correspondingly reduced, and water resources are saved.
The invention is further illustrated below with reference to examples.
Examples:
After 40-60%wt. urea solution (40-50 ℃) is heated to 140-160 ℃ by saturated steam in a urea hydrolyzer, urea and water undergo hydrolysis reaction to generate mixed gas (hydrolysis product gas) of NH 3、CO2 and water vapor at 140-160 ℃, the product gas continuously escapes from the solution to a gas phase area at the upper part of the urea hydrolyzer, and is rapidly and uniformly trapped by a gas collecting hole of a collecting pipe 11 on a gas trapping unit 1 and then discharged to a reheating unit 2 at the top of the urea hydrolyzer from an exhaust pipe 13.
When entering the reheating unit 2, the product gas is blocked by the flow equalizing plate 22, and the flow speed is rapidly reduced and is diffused to uniformly enter the shell 21 of the reheating unit 2 through dense small holes on the flow equalizing plate 22. In the process of flowing through the reheating unit 2, the product gas is heated by a steam coil 23 arranged in the shell 21, is discharged to an ammonia supply pipeline in a factory from a product gas outlet 26 after the temperature is increased to 180-200 ℃, and is finally conveyed to the SCR denitration system. The high-temperature steam in the steam coil 23 in the reheating unit 2 is directly connected with auxiliary steam of 0.8-1.2 MPa and 300 ℃ of the power plant, enters the steam coil 23 from the steam inlet 24, is discharged from the steam outlet 25 after heat exchange and temperature reduction, and enters the urea hydrolyzer to heat urea solution after the pressure and temperature are further reduced to saturated steam by the temperature and pressure reduction unit 3.
The gas collecting holes uniformly and densely distributed on the gas collecting unit 1 can rapidly and uniformly collect product gas collected in a gas phase region in the urea hydrolyzer, reduce internal pressure fluctuation caused by centralized exhaust, facilitate the product gas to continuously escape from the solution, promote urea hydrolysis reaction and improve urea hydrolysis efficiency.
The diameter of the shell 21 of the reheating unit 2 is larger than that of the exhaust pipe 13, and the flow equalizing plate 22 arranged in the reheating unit has a speed reducing and flow equalizing effect on the product gas exhausted by the exhaust pipe 13, so that the product gas is uniformly heated by steam in the steam coil 3 when passing through the reheating unit 2 at a lower flow rate, and an ideal reheating effect is achieved.
The steam coil 3 may take various forms, such as a serpentine coil, a spiral coil, a U-shaped coil, a tubular steam pipe, etc., and the height and diameter of the coil are reasonably determined according to the heat exchange area calculated by heat transfer, thereby determining the diameter of the shell 21 in the reheat unit. The diameter of the casing 21 is preferably 2 to 4 times the diameter of the exhaust pipe 21, and the height is preferably 1 to 2 m.
The reheat unit 2 fully utilizes the heat of auxiliary superheated steam to further improve the temperature of the product gas, so that the problems of steam reflux, polymer corrosion and blockage in the process of conveying the product gas can be avoided, the steam heat energy loss is saved, and the water consumption of the temperature-reducing water pump is reduced.
In summary, the beneficial effects of the invention mainly include the following aspects:
1) The gas trapping unit arranged in the gas phase zone at the upper part of the urea hydrolyzer can rapidly and uniformly collect and discharge hydrolysis product gas accumulated at the upper part of the hydrolyzer, reduce internal pressure fluctuation caused by exhaust, promote hydrolysis gas to escape from liquid and improve urea hydrolysis efficiency;
2) The temperature of the urea hydrolysis product gas collected by the gas capturing unit is further increased after being heated by the introduced auxiliary steam, the temperature of the product gas can be ensured to be always maintained above the dew point temperature in the process of being conveyed to the SCR denitration zone, the water vapor in the product gas can be effectively prevented from being condensed back and ammonia and carbon dioxide polymers are effectively prevented from being generated, the pipeline system is prevented from being blocked and corroded, and the running reliability of the system is improved;
3) The auxiliary steam before temperature reduction and pressure reduction is utilized to further heat the urea hydrolysis product gas to improve the temperature, so that the heat loss caused by the steam in the temperature reduction and pressure reduction process is reduced, and the energy is saved. Compared with the technology of improving the gas temperature of the hydrolysis product by electric heating, the technology has obvious energy-saving effect.
4) The auxiliary steam after heat transfer with the urea product gas is subjected to temperature reduction and pressure reduction to saturated steam after the temperature is reduced, so that the energy can be fully utilized, the water consumption of the water spraying pump is reduced, and the water resource is saved.
5) The invention has simple structure and low cost, and is easy to implement and apply in practical engineering projects.
The invention is not limited to the specific embodiments described above. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification, as well as to any novel one, or any novel combination, of the steps of the method or process disclosed.
Claims (4)
1. The utility model provides a urea hydrolysis gas entrapment and energy-conserving reheat device which characterized in that includes:
the gas trapping unit is arranged in the upper gas phase space of the urea hydrolyzer and extends out of the urea hydrolyzer to be connected with the ammonia supply pipeline or the reheating unit;
The reheating unit comprises a shell and a steam coil pipe arranged in the shell, wherein the shell is arranged in the ammonia supply pipeline or is connected with the gas trapping unit through a product gas inlet and is connected with the ammonia supply pipeline through a product gas outlet, the steam inlet of the steam coil pipe is connected with a steam source, and the steam outlet of the steam coil pipe is connected with the steam inlet of the urea hydrolyzer;
The temperature and pressure reducing unit is arranged on a pipeline between a steam outlet of the steam coil pipe and a steam inlet of the urea hydrolyzer;
the gas capture unit is a T-shaped pipe assembly and comprises a longer collection pipe arranged along the axial direction of the urea hydrolyzer and a shorter exhaust pipe arranged along the radial direction of the urea hydrolyzer;
a plurality of groups of gas collecting holes are arranged on the lower surface of the collecting pipe at intervals, each group of gas collecting holes are uniformly distributed along the radial direction of the collecting pipe, and two ends of the collecting pipe are blocked by end covers; the exhaust pipe extends out of the urea hydrolyzer shell and is connected with an ammonia supply pipeline or a reheating unit;
A flow equalizing plate is arranged at a product gas inlet of the shell in the reheating unit, is an orifice plate uniformly provided with a plurality of small orifices and is arranged on the whole cross section of the shell of the reheating unit;
when the shell of the reheating unit is connected with the gas capturing unit through the product gas inlet and is connected with the ammonia supply pipeline through the product gas outlet, the shell of the reheating unit is connected with the shell of the urea hydrolyzer through a flange or through welding, the central line of the shell of the reheating unit is opposite to the central line of the exhaust pipe, and the diameter of the shell of the reheating unit is larger than that of the exhaust pipe;
When the shell of the reheating unit is arranged in the ammonia supply pipeline, two ends of the shell of the reheating unit are connected with the ammonia supply pipeline through the cone section or the end socket open holes.
2. The urea hydrolyzing gas capturing and energy-saving reheating device according to claim 1, wherein the steam coil is a serpentine coil, a spiral coil, a U-shaped coil or a tube coil, and the ammonia supply pipeline is connected with the SCR denitration system.
3. The urea hydrolysis gas capturing and energy-saving reheating device according to claim 1, wherein the steam source is auxiliary heating steam of a power plant at 0.8-1.2 MPa and at-300 ℃, and the steam passing through the reheating unit and the temperature and pressure reducing unit is saturated steam at 0.7-0.8 MPa and at 170-180 ℃.
4. The urea hydrolysis gas capturing and energy-saving reheating device according to claim 1, wherein the temperature of the product gas output by the gas capturing unit is 140-160 ℃, and the temperature of the product gas after passing through the reheating unit is 180-200 ℃.
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| EP2502881A1 (en) * | 2011-03-24 | 2012-09-26 | Urea Casale S.A. | Process and plant for ammonia-urea production |
| US9586831B2 (en) * | 2014-06-09 | 2017-03-07 | Wahlco, Inc. | Urea to ammonia process |
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