CN217829533U - System for reducing nitrogen oxides in tail gas - Google Patents
System for reducing nitrogen oxides in tail gas Download PDFInfo
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- CN217829533U CN217829533U CN202221503581.7U CN202221503581U CN217829533U CN 217829533 U CN217829533 U CN 217829533U CN 202221503581 U CN202221503581 U CN 202221503581U CN 217829533 U CN217829533 U CN 217829533U
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Abstract
The utility model discloses a system for reduce nitrogen oxide in tail gas, include: the device comprises a sodium sulfite mother liquor heater, wherein one end of the sodium sulfite mother liquor heater is communicated with sodium sulfite mother liquor to be treated, and the other end of the sodium sulfite mother liquor heater is connected with the middle part of a conversion washing cooling tower; the conversion washing cooling tower is sequentially connected with a conversion separator and a converted gas isothermal oxidation tower through pipelines, NOx gas coming out of the top of the converted gas isothermal oxidation tower is respectively sent to a plurality of alkali absorption tower groups through converted gas regulating valves, and is absorbed through sodium carbonate solution in the alkali absorption tower groups. The utility model discloses through a series of devices to and the setting of pipeline, the nitrogen oxide that will come from the conversion process, through isothermal oxidation, accurate distribution make in the alkali absorption export tail gas NOx reduce by a wide margin, reduce the gas ammonia quantity for follow-up environmental protection facility tail gas processing apparatus, thereby reduce the consumption of product gas ammonia by a wide margin.
Description
Technical Field
The utility model discloses the technique relates to NOx's apparatus for producing, concretely relates to system for reduce nitrogen oxide in tail gas.
Background
NOx is one of important air pollution sources, the emission of NOx can cause acid rain and acid mist, the ozone layer can be damaged, serious harm is brought to self-heating environment, human production and life, the emission standard of the air pollutants is enhanced along with the state, most NOx in the nitrate industry is matched with a tail gas treatment device after most NOx is absorbed by alkali, and the NOx is changed into N through a catalyst and ammonia gas 2 And is discharged to the atmosphere.
However, in the above-mentioned conventional nitrate production process, there are problems as follows:
(1) After NOx is absorbed by alkali in a multi-tower series connection mode, the content of NOx is gradually reduced, the NO oxidation rate is slowed, the content of NOx gas in tail gas entering a tail gas treatment device through alkali absorption is too high, and the production fluctuation is easy to cause excessive discharge.
(2) Because the NO content in the tail gas of the alkali absorption tower is low in oxidation rate and slow in oxidation rate, the original design of nitrate or the modification of enterprises increases the oxidation space of the rear tower, so that the NO oxidation rate is improved, and the content of NOx in the tail gas of the alkali absorption tower is reduced.
(3) Although industry experts and enterprise technicians continuously explore and propose technologies of increasing oxygen content in tail gas by adding air to an alkali absorption rear tower to promote NO oxidation and distributing NOx gas from an ammonia oxidation outlet to the alkali absorption rear tower by cooling oxidation and the like in the nitrate production process for decades, the problems of tail gas of the alkali absorption rear tower are not fundamentally solvedSlow oxidation rate of medium NO, NO 2 The content is low.
(4) Because the content of NOx entering the tail gas treatment device through alkali absorption is high, excessive NH3 is usually added into the tail gas treatment device in order to treat the standard emission of NOx, and environmental pollution is caused.
(5) The tail gas treatment device is used for discharging NOx up to the standard, the filling amount of a catalyst of the ammonia reduction reactor is increased, the excessive discharge caused by the overhigh content of the NOx entering the tail gas treatment device due to alkali absorption is prevented, and the device investment is increased.
SUMMERY OF THE UTILITY MODEL
The utility model aims to the tail gas treatment process is absorbed to above-mentioned nitre saline alkali, and the various problems that exist in the middle of the actual operation at present improve, provide a system that reduces nitrogen oxide in the tail gas, make full use of tail gas, the air feed, structural design such as management improves the efficiency that reduces nitrogen oxide in the tail gas.
In order to achieve the above purpose, the utility model provides a following technical scheme:
a system for reducing nitrogen oxides in an exhaust gas, comprising:
the device comprises a sodium sulfite mother liquor heater E-707101, wherein one end of the sodium sulfite mother liquor heater E-707101 is communicated with sodium sulfite mother liquor to be treated, and the other end is connected with the middle part of a conversion washing cooling tower C-707108;
the conversion washing cooling tower C-707108 is sequentially connected with a conversion separator and a converted gas isothermal oxidation tower through pipelines, NOx gas coming out of the top of the converted gas isothermal oxidation tower is respectively sent to a plurality of alkali absorption tower groups through converted gas regulating valves, and is absorbed through sodium carbonate solution in the alkali absorption tower groups.
In a preferred embodiment of the present invention, the alkali absorption tower set is further connected with a primary alkali liquid pipeline and a secondary alkali liquid pipeline.
In a preferred embodiment of the present invention, the alkali absorption tower set comprises at least 4 alkali absorption towers connected in series, and the alkali solution in the alkali absorption towers is sodium carbonate solution.
In a preferred embodiment of the utility model, the alkali liquor pipeline is used for pumping the circulating alkali liquor at the bottom of the tower to the tower top through the alkali liquor circulating pump, the circulating alkali liquor is in reverse contact with tail gas, and sodium carbonate tail gas in the circulating alkali liquor reacts to generate sodium nitrite and sodium nitrate.
In a preferred embodiment of the present invention, the reforming scrubber cooling tower C-707108 comprises a mixing zone located at the upper portion of the reforming scrubber cooling tower C-707108 and a reforming zone located at the middle portion of the reforming scrubber cooling tower C-707108, wherein the reforming zone forms a qualified reforming liquid that passes through the bottom, the piping connection neutralizer.
In a preferred embodiment of the present invention, the conversion region includes a bending group formed by a plurality of internal connection pipes, and is located at a position where the dilute nitric acid inlet pipe penetrates through the conversion washing cooling tower C-707108 and is disposed corresponding to an end position of the bending group.
In a preferred embodiment of the utility model, the reformed gas isothermal oxidation tower is connected with the gas supply channel, and the reformed gas generated by the reforming washing cooling tower is extracted from the top of the tower and is fully oxidized by the reformed gas isothermal oxidation tower to enter the alkali absorption tower set.
In a preferred embodiment of the present invention, the whole temperature of the reforming gas isothermal oxidation tower is controlled at 20-40 ℃, and the concentration of nitrogen oxides is controlled>13% oxygen concentration>10％，NO x Oxidized to more than 85 percent in the converted gas isothermal oxidation tower.
Compared with the prior art, the beneficial effects of the utility model are that:
the utility model, through a series of devices and the arrangement of pipelines, can greatly reduce the NOx in the tail gas of the alkali absorption outlet through isothermal oxidation and accurate gas distribution of the nitrogen oxide (high-purity NOx gas containing a small amount of water) from the conversion process, thereby greatly reducing the consumption of gas ammonia for the tail gas treatment device of the subsequent environmental protection facility;
drawings
FIG. 1 is a schematic view of the working structure of the present invention;
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts all belong to the protection scope of the present invention.
In order to clarify the utility model discloses an embodiment, to coming from conversion process sodium nitrite mother liquor and dilute nitric acid solution reaction generation high-purity conversion gas, absorb process high-purity conversion gas to alkali and carry out high-efficient oxidation, accurate distribution, through NOx process in the alkali absorption quick absorption tail gas, strict control alkali absorbs NOx concentration in the export tail gas.
Referring to fig. 1, a system for reducing nitrogen oxides in exhaust gas includes: the device comprises a sodium sulfite mother liquor heater E-707101, wherein one end of the sodium sulfite mother liquor heater E-707101 is communicated with sodium sulfite mother liquor to be treated, and the other end is connected with the middle part of a conversion washing cooling tower C-707108; the conversion washing cooling tower C-707108 is sequentially connected with a conversion separator and a converted gas isothermal oxidation tower through pipelines, NOx gas coming out of the top of the converted gas isothermal oxidation tower is respectively sent to a plurality of alkali absorption tower groups through converted gas regulating valves, and is absorbed through sodium carbonate solution in the alkali absorption tower groups.
The utility model, through a series of devices and the arrangement of pipelines, can greatly reduce the NOx in the tail gas of the alkali absorption outlet through isothermal oxidation and accurate gas distribution of the nitrogen oxide (high-purity NOx gas containing a small amount of water) from the conversion process, thereby greatly reducing the consumption of gas ammonia for the tail gas treatment device of the subsequent environmental protection facility;
specifically, the alkali absorption tower group is also connected with a primary alkali liquor pipeline and a secondary alkali liquor pipeline; the alkali absorption tower group comprises at least 4 groups of alkali absorption towers which are mutually connected in series, and alkali liquor in the alkali absorption towers is sodium carbonate solution.
Furthermore, the alkali liquor pipeline pumps the circulating alkali liquor at the bottom of the tower to the top of the tower through an alkali liquor circulating pump, the circulating alkali liquor is in reverse contact with the tail gas, and the sodium carbonate tail gas in the circulating alkali liquor reacts to generate sodium nitrite and sodium nitrate.
The conversion washing cooling tower C-707108 comprises a mixing area and a conversion area, wherein the mixing area is positioned at the upper part of the conversion washing cooling tower C-707108, the conversion area is positioned at the middle part of the conversion washing cooling tower C-707108, and qualified conversion liquid formed in the conversion area is connected with a neutralizer through a bottom and a pipeline; the conversion region comprises a bending group formed by a plurality of internal connecting pipes, and a dilute nitric acid inlet pipe which is positioned on the conversion washing cooling tower C-707108 and is penetrated through the conversion washing cooling tower, and is arranged corresponding to the end part of the bending group.
By adopting the preparation method of the device, the heated sodium sulfite mother liquor enters a conversion washing cooling tower for washing; reacting the washed sodium sulfite mother liquor with nitric acid at the lower part of a conversion washing cooling tower to generate conversion gas; the converted gas enters the bottom of the isothermal oxidation tower of the converted gas from the top of the conversion washing cooling tower to be mixed with secondary air after being washed by sodium sulfite mother liquor, cooled by cooling water and physically separated, so that NO is generated x Further oxidizing the gas; NO x The gas is discharged from the top of the converted gas isothermal oxidation tower, enters a plurality of alkali absorption tower groups through a converted gas regulating valve, enters an alkali absorption process, and finally enters a tail gas treatment process after NOx tail gas is absorbed by alkali.
Specifically, the flow of the system for reducing nitrogen oxides in the exhaust gas is as follows:
heating sodium sulfite mother liquor from evaporation process to 105 deg.C with low pressure steam by sodium sulfite mother liquor heater E-707101, feeding into the middle part of conversion washing cooling tower C-707108, absorbing conversion tail gas from the lower part of conversion washing cooling tower, and introducing nitric acid and part of NO 2 Absorption, namely pre-converting a part of sodium sulfite;
dilute nitric acid pumped from the outside dilute nitric acid enters the middle part of the conversion tower, is mixed with the sodium sulfite mother liquor and then enters the conversion section; finishing the conversion process, wherein the converted liquid flows to the bottom of the tower and is sent to a neutralizer after being qualified;
the upper part of the conversion washing cooling tower is provided with a cooling separation section, the temperature of the converted gas is reduced to be less than 80 ℃ through cooling, the corrosion of the converted gas to equipment is reduced, the converted gas is discharged from the tower top after cooling separation and enters a converted gas isothermal oxidation tower C-707109 of an alkali absorption process.
The converted gas from the top of the conversion washing cooling tower enters the bottom of the converted gas isothermal oxidation tower C-707109 to be mixed with secondary air, so that the NOx gas is further oxidized.
Due to oxidation of NO to NO by atmospheric pressure 2 The process is difficult, and the literature shows that the reaction must be carried out under the condition of low temperature to increase the reaction speed by increasing the concentration of nitrogen oxide and oxygen, so that the whole tower temperature of the isothermal oxidation tower of the converted gas is controlled to be 20-40 ℃, the concentration of nitrogen oxide is controlled to be 20-40 DEG C>13% oxygen concentration>10％，NO x Oxidized to more than 85 percent in the conversion gas isothermal oxidation tower.
The NOx gas flows out from the top of the reforming gas isothermal oxidation tower and passes through a reforming gas regulating valve according to NO and NO set by a NOx analyzer at the inlet of the 5#, 6#, 7# alkali towers 2 The gas is accurately distributed in proportion, the mixed gas of the converted gas and the alkali absorption tail gas enters 5#, 6#, 7# alkali absorption towers to be absorbed by sodium carbonate solution, and NO in the gas components after the mixed gas is distributed into the converted gas 2 Occupies NOx (NO + NO) 2 ) 30% of gas, and finally, alkali absorption tail gas enters a tail gas treatment process after being serially absorbed by 5#, 6#, and 7# alkali towers.
Continuously feeding primary alkali liquor from outside a battery compartment into 5#, 6#, 7# alkali absorption towers according to the alkalinity of circulating alkali liquor in the alkali towers, absorbing the 5#, 6#, 7# alkali, pumping the circulating alkali liquor at the bottom of the towers to the top of the towers through alkali liquor circulating pumps P-707107, P-707109AB, reversely contacting the circulating alkali liquor with tail gas at the operating temperature of 60 ℃, the pressure of 40KPa and the retention time of gas in the towers of about 26s, and continuously feeding sodium carbonate in the circulating alkali liquor and NO + NO in the tail gas 2 (N 2 O 3 ) Sodium nitrite and sodium nitrate are generated through reaction, lean solution (circulating alkali solution) pipelines are arranged at the outlet of an alkali solution circulating pump of P-707107, P-707107 and P-707109AB and are provided with an alkali tower liquid level regulating valve, and the lean solution is continuously extracted according to the liquid level of the alkali tower and is sent to an alkali dissolving post.
Example 1
Comprises 76.8 percent of water, 0.3 percent of sodium carbonate, 6.6 percent of sodium nitrate and 16.3 percent of sodium nitrite, the sodium sulfite mother liquor with the temperature of 76.5 ℃, is heated to 105 ℃ by steam of a sodium sulfite mother liquor heater E-707101 with the flow rate of 921.6kg/hr, and enters the middle part of a conversion washing cooling tower C-707108. And water with the molar content of 79.1 percent and nitric acid with the molar content of 20.9 percent enter the middle part of a conversion washing cooling tower C-707108 at the flow rate of 434.1kg/hr, the conversion reaction is carried out at the pressure of 180KPa and the temperature of 95 ℃, conversion gas generated by the conversion reaction is discharged from the top of the tower after being washed, cooled and separated by sodium sulfite mother liquor and enters an alkali absorption process to be used as raw material gas for accurately distributing gas in alkali absorption.
The converted gas is cooled and separated by a converted gas cooler E-707102 and a conversion separator F-707102 and comprises 3.5% of water, 94.3% of NO and 2.2% of CO in molar content 2 Working condition air quantity is 50.7Nm 3 H, enters the bottom C-707109 of the isothermal oxidation tower of the reformed gas at the pressure of 180KPa and the temperature of 39.9 ℃ and contains 20.2 percent of O by mol content with secondary air 2 76.4% of N 2 And 3.4% of water. The NOx gases are further oxidized at a pressure of 180KPa and a temperature of 40 ℃. The gas composition at the top outlet of the reforming gas isothermal oxidation tower contains 14.3 mol percent of O 2 71.1% of N 2 3.6% of water, 1.6% of NO, 9.1% of NO 2 0.3% of CO 2 NO oxidation degree of 85.1%, and working gas amount of 460.2Nm 3 /h。
The converted gas at the outlet of the converted gas isothermal oxidation tower is analyzed according to a No. 5 alkali absorption tower C-707105 inlet NOx analyzer and contains NO and NO 2 Contains 72.64 mol% of N 2 4% of O 2 0.81% NO, 0.11% NO 2 16.95% of water and 5.49% of CO 2 Regulating NO and NO in 5# alkali absorption tower by converted gas regulating valve 2 The proportion is 23 percent, and the N with the molar content of 72.64 percent is contained after the accurate gas distribution is carried out to the inlet of the No. 5 alkali absorption tower and the tail gas are mixed 2 4% of O 2 0.81% NO, 0.11% NO 2 16.95% of water and 5.49% of CO 2 The obtained product was fed into No. 5 alkali absorption column at a flow rate of 35710.4 kg/hr. After NOx in the tail gas and the circulating alkali liquor are absorbed, N with the molar content of 74.3 percent is discharged from the top of the tower 2 4.1% of O 2 0.3% of NO, 0.03% of NO 2 15.4% of water and 5.9% of CO 2 . The 26.9% primary alkali solution enters the No. 5 alkali absorption tower at the flow rate of 1807.9kg/hr, and the barren solution 2334.1kg/hr is sent to the alkali dissolving process.
The tail gas of 141KPa at the top opening of the No. 5 alkali tower and 64.94 ℃ enters the inlet of the No. 6 alkali absorption tower C-707106, and the converted gas is analyzed to contain NO and NO according to a NO analyzer at the inlet of the No. 6 alkali absorption tower 2 The tail gas of (3). Regulating NO and NO entering 6# alkali absorption tower by converted gas regulating valve 2 The proportion is 23 percent, and the N with the molar content of 74.3 percent is contained after the accurate gas distribution is carried out to the inlet of the No. 6 alkali absorption tower and the tail gas are mixed 2 4.2% of O 2 0.3% of NO, 0.08% of NO 2 15.3 percent of water and 5.8 percent of CO 2 Feeding the tail gas into a No. 6 alkali absorption tower at a flow rate of 35357.8kg/hr, absorbing NOx in the tail gas and circulating alkali liquor, and discharging N with a molar content of 74.9 percent from the tower top 2 4.2% of O 2 0.11% NO, 0.009% NO 2 14.7% of water, 6% of CO 2 .26.9% primary alkali solution was fed to the alkali dissolving process at a flow rate of 748.4kg/hr in No. 6 alkali absorption column and a lean solution of 982 kg/hr.
The tail gas at 139KPa and 63.77 ℃ of the tower top outlet of the No. 6 alkali tower enters the inlet of a No. 7 alkali absorption tower C-707107, the converted gas at the outlet of the converted gas isothermal oxidation tower is analyzed to contain NO and NO according to a NO analyzer at the inlet of the No. 7 alkali absorption tower 2 The tail gas of (2). NO and NO are adjusted to enter a 7# alkali absorption tower through a converted gas regulating valve 2 The proportion is 23 percent, the gas is accurately distributed to the inlet of a 7# alkali absorption tower and is mixed with tail gas, the mixture contains 74.9 percent of N2 and 4.3 percent of O 2 0.11% NO, 0.033% NO 2 14.7% of water, 6% of CO 2 Feeding the tail gas into a No. 7 alkali absorption tower at a flow rate of 35238.1kg/hr, absorbing NOx in the tail gas and circulating alkali liquor, and discharging N with a molar content of 75.3% from the top of the tower 2 4.3% of O 2 0.042% of NO, 0.002% of NO 2 14.3% of water and 6.1% of CO 2 And the NOx content in the tail gas of alkali absorption is 602.7mg/Nm 3 Entering a tail gas treatment process. 26.9% primary alkali solution was fed to the alkali dissolving step at a flow rate of 275.4kg/hr in the No. 7 alkali absorption column and 402.8kg/hr in the lean solution.
Example 2
Comprises 76.79 percent of water, 0.26 percent of sodium carbonate, 6.63 percent of sodium nitrate and 16.32 percent of sodium nitrite, the sodium sulfite mother liquor with the temperature of 76.5 ℃, is heated to 105 ℃ by passing through a sodium sulfite mother liquor heater E-707101 steam at the flow rate of 522.8kg/hr, and enters the middle part of a conversion washing cooling tower C-707108. And water with the molar content of 79.1 percent and nitric acid with the molar content of 20.9 percent enter the middle part of a conversion washing cooling tower C-707108 at the flow rate of 246.2kg/hr, the conversion reaction is carried out at the pressure of 180KPa and the temperature of 95 ℃, converted gas generated by the conversion reaction is discharged from the top of the tower after being washed, cooled and separated by sodium sulfite mother liquor and enters an alkali absorption process to be used as raw material gas for alkali absorption precise gas distribution.
The reformed gas is cooled and separated by a reformed gas cooler E-707102 and a reforming separator F-707102, and comprises 3.09% of water, 94.68% of NO and 2.23% of CO2, and the working gas amount is 28.6Nm 3 H, enters the bottom C-707109 of the isothermal oxidation tower of the reformed gas at the pressure of 180KPa and the temperature of 40 ℃ and contains 20.24 percent of O by mol content with secondary air 2 76.39% of N 2 And 3.37% of water. The NOx gases are further oxidized at a pressure of 180KPa and a temperature of 40 ℃. The gas composition at the top outlet of the reforming gas isothermal oxidation tower contains 12.43 percent of O 2 67.77% of N 2 6.01% of water, 2.43% of NO, 11.05% of NO 2 0.32% CO 2 NO oxidation degree of 82%, working gas amount of 209.7Nm 3 /h。
The converted gas at the outlet of the converted gas isothermal oxidation tower is analyzed according to a No. 5 alkali absorption tower C-707105 inlet NOx analyzer and contains NO and NO 2 Contains 73.36 mol% of N 2 4.04% of O 2 0.82% NO, 0.11% NO 2 16.13% of water and 5.54% of CO 2 Regulating NO and NO entering 5# alkali absorption tower by a converted gas regulating valve 2 The proportion is 17 percent, and the N with the molar content of 73.33 percent is contained after the accurate gas distribution is carried out to the inlet of the No. 5 alkali absorption tower and the tail gas are mixed 2 4.08% of O 2 0.83% of NO, 0.17% of NO 2 16.08 percent of water and 5.51 percent of CO 2 And the obtained product enters a No. 5 alkali absorption tower at the flow rate of 35102.7 kg/hr. NOx in the exhaust gas andafter absorption of the circulating alkali liquor, the product containing 74.61 mol% of N is discharged from the top of the tower 2 4.06% of O 2 0.40% NO, 0.04% NO 2 15.02% of water and 5.88% of CO 2 . The 26.9% primary alkali liquor enters a No. 5 alkali absorption tower at the flow rate of 1433.2kg/hr, and the barren liquor 1843.7kg/hr is sent to the alkali dissolving process.
The tail gas of 141KPa and 64.37 ℃ at the tower top outlet of the No. 5 alkali tower enters the inlet of a No. 6 alkali absorption tower C-707106, and the converted gas is analyzed by a No. 6 alkali absorption tower inlet NOx analyzer to contain NO and NO 2 The tail gas of (3). NO and NO entering the No. 6 alkali absorption tower are regulated by a conversion gas regulating valve 2 The proportion is 17 percent, the accurate gas distribution is carried out to the inlet of the No. 6 alkali absorption tower, and the mixed tail gas contains N with the molar content of 74.58 percent 2 4.09% of O 2 0.41% NO, 0.08% NO 2 14.98% of water, 5.86% of CO 2 The tail gas enters a No. 6 alkali absorption tower at the flow rate of 34799.6kg/hr, NOx in the tail gas and the circulating alkali liquor are absorbed, and N with the molar content of 75.33 percent is discharged from the top of the tower 2 4.08% of O 2 0.19% NO, 0.02% NO 2 14.33% of water, 6.06% of CO 2 .26.9% primary alkali solution is fed to the alkali dissolving process at a flow rate of 775.2kg/hr in the No. 6 alkali absorption tower, and 1016.7kg/hr in the lean solution.
The tail gas at 139KPa and 63.72 ℃ at the top opening of the No. 6 alkali tower enters the inlet of a No. 7 alkali absorption tower C-707107, the converted gas at the outlet of the converted gas isothermal oxidation tower is analyzed to contain NO and NO according to a NO analyzer at the inlet of the No. 7 alkali absorption tower 2 The tail gas of (2). NO and NO are adjusted to enter a 7# alkali absorption tower through a converted gas regulating valve 2 The proportion is 17 percent, and the N with the molar content of 75.28 percent is contained after the accurate gas distribution is carried out to the inlet of the 7# alkali absorption tower and the tail gas are mixed 2 4.14% of O 2 0.20% NO, 0.04% NO 2 14.3% of water, 6.04% of CO 2 The tail gas enters a No. 7 alkali absorption tower at the flow rate of 34656.6kg/hr, NOx in the tail gas and the circulating alkali liquor are absorbed and then N with the molar content of 75.82 percent is discharged from the top of the tower 2 4.15% of O 2 0.101% NO, 0.005% NO 2 13.77% of water and 6.15% of CO 2 NOx content 1455.3mg/Nm in the alkali absorption tail gas 3 Entering a tail gas treatment process. 26.9% primary lye flows at 365.9kg/hrAmount 7# alkali absorption column, and 534.9kg/hr of lean solution were sent to the alkali dissolving step.
Example 3
According to No. 5 alkali absorption tower C-707105 inlet NOx analyzer, analyzed gas containing NO and NO 2 Contains 73.36 mol% of N 2 4.04% of O 2 0.82% NO, 0.11% NO 2 16.13% of water and 5.54% of CO 2 And the obtained product enters a No. 5 alkali absorption tower. After NOx in the tail gas and the circulating alkali liquor are absorbed, N with the molar content of 74.19 percent is discharged from the top of the tower 2 4.01% of O 2 0.54% NO, 0.06% NO 2 15.42% of water and 5.78% of CO 2 . The 26.9% primary alkali solution enters a No. 5 alkali absorption tower at a flow rate of 942.3kg/hr, and the lean solution 1218.7kg/hr is sent to the alkali dissolving process.
The tail gas at 141KPa and 64.42 ℃ at the top opening of the No. 5 alkali tower enters a No. 6 alkali absorption tower C-707106, NOx in the tail gas and circulating alkali liquor are absorbed and then are discharged from the tower top and contain N with the molar content of 74.74 percent 2 3.99% of O 2 0.37% of NO, 0.03% of NO 2 14.94 percent of water and 5.92 percent of CO 2 .26.9% primary alkali solution was fed to the alkali dissolving step at a flow rate of 536.4kg/hr in the No. 6 alkali absorption column and 711kg/hr in the lean solution.
The tail gas at 139KPa of the tower top opening of the No. 6 alkali tower and 63.71 ℃ enters a No. 7 alkali absorption tower C-707107, NOx in the tail gas and circulating alkali liquor are absorbed and then N with the molar content of 75.14 percent is discharged from the tower top 2 4.04% of O 2 0.29% NO, 0.02% NO 2 14.51% of water, 6% of CO 2 The NOx content in the tail gas of alkali absorption is 4166.8mg/Nm 3 And entering a tail gas treatment process. 26.9% primary alkali solution was fed to the alkali dissolving step at a flow rate of 275.9kg/hr in the No. 7 alkali absorption column and 411.7kg/hr in the lean solution.
Comparison table of key process data of implementation case:
as can be seen from the above 3 examples:
the higher the oxidation degree of the gas distribution is, the more favorable the tail gas reduction is, and the higher the NO oxidation rate at the inlet of the alkali tower is, the more favorable the tail gas reduction is. By adding NOx gas with higher oxidation degree, the reaction is continued, and the tail gas at the alkali absorption outlet is greatly reduced.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. A system for reducing nitrogen oxides in an exhaust gas, comprising:
the device comprises a sodium sulfite mother liquor heater, wherein one end of the sodium sulfite mother liquor heater is communicated with sodium sulfite mother liquor to be treated, and the other end of the sodium sulfite mother liquor heater is connected with the middle part of a conversion washing cooling tower;
the conversion washing cooling tower is sequentially connected with a conversion separator and a converted gas isothermal oxidation tower through pipelines, NOx gas coming out of the top of the converted gas isothermal oxidation tower is respectively sent to a plurality of alkali absorption tower groups through converted gas regulating valves, and is absorbed through sodium carbonate solution in the alkali absorption tower groups.
2. The system for reducing nitrogen oxides in exhaust gas according to claim 1, wherein the alkali absorption tower set is further connected with a primary alkali liquor pipeline and a secondary alkali liquor pipeline.
3. The system for reducing nitrogen oxides in exhaust gas according to claim 2, wherein the alkali absorption tower set comprises at least 4 alkali absorption towers connected in series, and alkali liquor in the alkali absorption towers is sodium carbonate solution.
4. The system for reducing nitrogen oxides in tail gas according to claim 2, wherein the alkali liquor pipeline pumps the circulating alkali liquor at the bottom of the tower to the top of the tower through an alkali liquor circulating pump, the circulating alkali liquor is in reverse contact with the tail gas, and the sodium carbonate tail gas in the circulating alkali liquor reacts to generate sodium nitrite and sodium nitrate.
5. The system for reducing nitrogen oxides in exhaust gas according to claim 1, wherein the reforming scrubbing and cooling tower comprises a mixing zone and a reforming zone, the mixing zone is located at the upper part of the reforming scrubbing and cooling tower, the reforming zone is located at the middle part of the reforming scrubbing and cooling tower, and qualified reforming liquid formed in the reforming zone is connected with a neutralizer through a bottom part and a pipeline.
6. The system for reducing nitrogen oxides in exhaust gas according to claim 5, wherein the conversion region comprises a bending group formed by a plurality of internal connecting pipes, and the bending group is positioned at the end part of a dilute nitric acid inlet pipe, penetrates through the conversion washing cooling tower and corresponds to the bending group.
7. The system for reducing nitrogen oxides in tail gas according to claim 1, wherein the reformed gas isothermal oxidation tower is connected with a gas supply channel, and the reformed gas generated by the reforming washing cooling tower is taken from the top of the tower and is fully oxidized by the reformed gas isothermal oxidation tower to enter the alkali absorption tower set.
8. The system for reducing nitrogen oxides in the tail gas according to any one of claims 1 to 7, wherein the whole temperature of the converted gas isothermal oxidation tower is controlled to be 20-40 ℃, the concentration of nitrogen oxides is >13%, the concentration of oxygen is >10%, and NOx is oxidized to be more than 85% in the converted gas isothermal oxidation tower.
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