CN111909000A - System and method for supplementing nitrogen oxides in coal-to-ethylene glycol - Google Patents
System and method for supplementing nitrogen oxides in coal-to-ethylene glycol Download PDFInfo
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Abstract
The invention relates to a coal-based ethylene glycol nitrogen oxide supplementing system and a method thereof, wherein the system comprises a compressor, an esterification pre-reactor, an oxidation esterification tower and a nitric acid reduction tower which are sequentially connected along a reactant feeding direction, a gas mixer is arranged between the esterification pre-reactor and the oxidation esterification tower, the gas mixer is connected with a nitrogen oxide pre-processor, the gas mixer comprises a main pipe and a nitrogen oxide pipe arranged inside the main pipe, the main pipe is arranged in a connecting pipeline, the nitrogen oxide pipe is provided with a plurality of nitrogen oxide outlet holes on the pipe wall positioned in the main pipe, the nitrogen oxide pre-processor comprises a pre-heater and a buffer tank which are sequentially connected, and the outlet of the buffer tank is connected with the inlet of the nitrogen oxide pipe. The invention makes nitrogen oxide NOxThe supplement of the nitrogen oxide is stable and uniform, the conversion rate of the nitrogen oxide and the selectivity of a target product are improved, the consumption of the nitrogen oxide is reduced, and the driving and running cost is reduced.
Description
Technical Field
The invention relates to a nitrogen supply system for chemical production, in particular to a system and a method for supplementing nitrogen oxides in ethylene glycol preparation from coal.
Background
Ethylene glycol is an important chemical raw material and strategic material, is used for manufacturing polyester (which can be further used for producing terylene, beverage bottles and films), explosive and glyoxal, and can be used as an antifreezing agent, a plasticizer, hydraulic fluid, a solvent and the like. The coal-made glycol is used for producing glycol by replacing petroleum ethylene with coal. Experts point out that the technical route conforms to the resource characteristics of oil shortage, gas shortage and relatively rich coal resources in China. At present, the domestic route for preparing ethylene glycol from coal is mainly an oxalate method, and the flow diagram of the method is shown in figure 1.
Because the side reaction of the esterification system can cause nitrogen loss, nitrogen oxide needs to be continuously supplemented in the running process of the system to maintain nitrogen balance; in addition, during the start-up phase, a nitrogen balance needs to be established for the system, and fresh nitrogen oxides also need to be supplemented. The supplement mode of the nitrogen oxides and the supplement point are very important for the start and stable operation of the whole system.
Because the esterification reaction is easy to occur, the required retention time is only about 1 second, when the nitrogen oxide is supplemented into the system, the nitrogen oxide is easy to quickly perform the esterification reaction with methanol and NO in the circulating gas, a large amount of heat is released, and further the decomposition of MN is promoted, so that the safety problem is caused; and when the nitrogen oxide is locally excessive, the selectivity of nitric acid, methyl nitrate and the like is high, so that nitrogen loss is caused, wherein the existence of the methyl nitrate increases the potential safety hazard. Therefore, the research on a stable and efficient nitrogen oxide supplementing method has important significance on the project of preparing the ethylene glycol from the coal.
At present, the nitrogen supplement method of the system on the industrial system of the coal-to-ethylene glycol project is mainly N2O4The addition method and the nitric acid addition method, and in addition, the ammonia oxidation method and the sodium nitrite and acid reaction method are adopted.
The nitric acid method has the disadvantages that the nitric acid concentration is high in the start-up stage, a plurality of byproducts are easily generated, the utilization rate of nitrogen elements is influenced, a large amount of byproducts are brought in, and part of the byproducts bring safety problems, such as methyl nitrate.
Nitrogen oxides with N2O4Directly adding or adding after decomposing, and concretely carrying out the following reaction processes:
in the driving stage, N is supplemented2O4The reactions that occur are:
N2O4＝＝2NO2(reversible) (1)
CH3OH+N2O4＝＝CH3ONO+HNO3 (2-1)
CH3OH+2NO2＝＝CH3ONO+HNO3 (2-2)
N2O4+H2O＝＝HNO2+HNO3 (3-1)
2NO2+H2O＝＝HNO2+HNO3 (3-2)
Wherein methyl nitrite CH3ONO is a target product; HNO2Can react with methanol to generate MN:
HNO2+CH4O＝CH3ONO+H2O (4)
when the system is stably operated, the MN reacts in the carbonylation reactor:
2CH3ONO+2CO＝(CH3OCO)2+2NO (5)
generated (CH)3OCO)2(DMO) for subsequent hydrogenation, returning NO to the esterification system for continuous recycling, and supplementing O2Esterification reaction:
4NO+O2+4CH4O＝4CH3ONO+2H2O (6)
and nitric acid reduction reaction:
2NO+HNO3+3CH4O＝3CH3ONO+2H2O (7)
but HNO3Can not be completely converted and is partially discharged into waste water.
Although the above (5) and (6) enable the establishment of nitrogen circulation, nitrogen loss occurs due to the formation of by-products such as nitric acid, methyl nitrate and the like by side reactions:
4NO+3O2+2H2O＝4HNO3 (8)
HNO3+CH4O＝CH3ONO2+H2O (9)
therefore, even during steady state operation, a continuous nitrogen oxide make-up is still required to maintain the nitrogen balance in the system. N is a radical of2O4The disadvantage of the complementary method is that N2O4Easily gasified to be gaseous or decomposed to be gas NO2The phenomenon of gas-liquid coexistence is caused, and the gasification process brings about pressure fluctuation, so that the supplement amount is not easy to control stably. When N is present2O4When the supplement is unstable and the local concentration is too high, the reaction (3-1) and the following reaction (10) are easy to occur to increase the nitrogen loss rate:
3NO2+H2O＝2HNO3+NO (10)
when the nitrogen oxide to be supplied is generated by the ammonia oxidation method in the case of the ammonia oxidation method, the nitrogen oxide to be supplied is mainly nitrogen monoxide, so that oxygen is supplied at this time, and the above reaction (6) mainly occurs. Meanwhile, side reactions such as (9) may occur, resulting in nitrogen loss, and a continuous nitrogen oxide supply is also required to maintain nitrogen balance during the steady operation of the system.
When the nitrogen oxide to be added is generated by the ammoxidation method in the case of the reaction between sodium nitrite and acid, the nitrogen oxide to be added is mainly a mixture of nitrogen monoxide and nitrogen dioxide and has a molar ratio of approximately 1:1, so that the following reaction (11) mainly occurs without adding oxygen. At the same time, side reactions (10) occur, which cause nitrogen losses, and nitrogen oxides need to be continuously supplemented during the steady operation of the system to maintain nitrogen balance.
NO+NO2+2CH4O＝2CH3ONO+H2O (11)
Patent CN202791348U discloses a simple structure, accurate confession nitrogen equipment of feed, specifically be nitrogen oxide feeding equipment in coal system ethylene glycol production, this equipment includes liquid nitrogen tetroxide basin, nitrogen tetroxide basin upper end intercommunication nitrogen gas input tube, nitrogen tetroxide input tube and blow-down pipe, lower extreme intercommunication conveyer pipe front end, conveyer pipe rear end intercommunication rectifying column pre-heater, the conveyer pipe has set gradually liquid nitrogen control valve and orifice plate flowmeter from the front to the back, be provided with the nitrogen tetroxide measuring pump on the conveyer pipe between liquid nitrogen control valve and orifice plate flowmeter, conveyer pipe suit between orifice plate flowmeter and the rectifying column pre-heater is in the partial pipeline of steam cycle conveyer pipe. The utility model is only suitable for the supplement of dinitrogen tetroxide, and can not satisfy the supplement of other substances containing nitrogen elements into the reaction system.
Disclosure of Invention
The invention aims to provide a system and a method for supplementing nitrogen oxides in coal-based ethylene glycol, aiming at solving the problem that the nitrogen oxides cannot be efficiently and stably supplemented in the process of preparing ethylene glycol from coal, so that the nitrogen oxides can be stably supplemented in the flow rate and can be quickly and uniformly mixed with circulating gas when entering a system, thereby improving the conversion rate of the nitrogen oxides and the selectivity of a target product, saving the consumption of the nitrogen oxides, maintaining the nitrogen balance of the system, reducing the driving and running cost, reducing byproducts and improving the safety.
The purpose of the invention is realized by the following technical scheme:
the utility model provides a coal system ethylene glycol nitrogen oxide complementary system, this system is including the compressor, esterification pre-reactor, oxidation esterification tower and the nitric acid reduction tower that connect in order, and this system still includes the gas mixer, before locating the oxidation esterification tower, the gas mixer is connected with nitrogen oxide preprocessor, the gas mixer is responsible for and locates the inside nitrogen oxide pipe of being responsible for including being responsible for, nitrogen oxide preprocessor is gone into coal system ethylene glycol reaction system including the preheater and the buffer tank that connect gradually, through gas mixer and nitrogen oxide preprocessor with nitrogen oxide replenishment. The gas mixer can quickly and uniformly mix the supplemented nitrogen oxide and the esterification recycle gas or the esterification pre-reaction gas, reduce local temperature runaway and byproduct generation, and improve the system safety. The nitrogen oxide preprocessor can keep the nitrogen oxide in a single gas phase, avoid unstable flow caused by gas-liquid two phases in the feeding process, and the purpose of the buffer tank is to prevent larger pressure fluctuation caused by phase change. Further preferably, the nitrogen oxide outlet pipe is provided centrally in the main pipe and in parallel with the main pipe.
Further, the nitrogen oxide pipe comprises a nitrogen oxide inlet pipe, a nitrogen oxide outlet pipe and a nitrogen oxide outlet hole, wherein the nitrogen oxide inlet pipe and the nitrogen oxide outlet pipe are fixedly connected, and the nitrogen oxide outlet hole is formed in the nitrogen oxide outlet pipe.
Further, the nitrogen oxide outlet holes are uniformly or approximately uniformly distributed small holes, and are circular, square or oval in shape, and are further preferably circular.
Further, the ratio of the inner diameter of the nitrogen oxide outlet pipe to the inner diameter of the main pipe is 0.001 to 0.500: 1. more preferably, the ratio of the inner diameters is 0.02 to 0.10: 1.
furthermore, the nitrogen oxide preprocessor also comprises a flow controller which is connected with the buffer tank and can accurately control the flow of nitrogen oxide of the supplementing system through the flow controller.
A nitrogen oxide supplementing method of a coal-based ethylene glycol nitrogen oxide supplementing system is characterized in that a gas nitrogen oxide raw material enters through a preheater of a nitrogen oxide preprocessor, is preheated by the preheater, enters a buffer tank, then enters a nitrogen oxide pipe, enters a main pipe through a nitrogen oxide outlet of the nitrogen oxide pipe, is mixed with esterification recycle gas or pre-reaction gas, and then enters an oxidation esterification tower for reaction; liquid nitrogen oxide raw materials are added through the nitric acid reduction tower.
A method for supplementing the nitrogen oxides generated by preparing ethylene glycol from coal includes preparing NOxDirect utilization of N2O4Decomposition and utilization, direct utilization of nitric acid, N2O4Mixing with nitric acid, ammonia oxidation or reaction between sodium nitrite and acid.
Further, the nitrogen oxide is NOxWhen is in contact with the nitrogen atomxThe feeding point of (A) is arranged before the oxidation esterification tower. Further preferably, the NO isxThe feeding point of (A) is arranged after the esterification pre-reactor and before the oxidation esterification tower.
Further, when the nitrogen oxide is nitric acid, the supplementing point of the nitric acid is arranged in front of the nitric acid reduction tower. Further preferably, the supplementing point of the nitric acid is arranged on the oxidation esterification tower and the nitric acid reduction towerIn the meantime. N is a radical of2O4When the mixed nitric acid is added into the system, N is used in the start-up stage2O4Make-up, with nitric acid make-up or N in the steady-state operating phase2O4Compared with the method of supplementing nitric acid at the same time, the method can avoid the condition that the safety of the system is influenced by generating a large amount of byproducts such as methyl nitrate and the like due to the fact that the amount of the nitric acid is excessively large in the driving stage; and all with N2O4Compared with the supplement, N capable of avoiding supplement in the stable operation stage2O4Too little results in difficulty in accurately controlling the amount of supplementation.
Furthermore, when the method is adopted, esterification recycle gas or pre-reaction gas flows through the main pipe, the pretreated nitrogen oxide flows through the nitrogen oxide pipe, and the nitrogen oxide enters the main pipe through the nitrogen oxide outlet hole to be rapidly and uniformly mixed with the esterification recycle gas or the pre-reaction gas.
Further, when the method is adopted, the preheating temperature of the preheater is 20-150 ℃, preferably 21-100 ℃, and further preferably 50-90 ℃; the preheating aims at gasifying or decomposing nitrogen oxides, keeping a single gas phase and maintaining the stable feeding amount, thereby reducing the selectivity of byproducts; the buffer tank controls the residence time of the nitrogen oxide in the buffer tank to be 1-3600 s, preferably 60-1800 ssMore preferably 300 to 1500s。
Dinitrogen tetroxide, melting point-11.2 ℃; the boiling point was 21.2 ℃. It is readily decomposed into a gas whose nitrogen dioxide is reddish brown. Dinitrogen tetroxide and nitrogen dioxide interconvert according to the following equation:
N2O4＝＝2NO2(reversible)
When the temperature rises, the reaction proceeds in the direction of generating nitrogen dioxide; the finished dinitrogen tetroxide product is in fact an equilibrium mixture with nitrogen dioxide.
Nitric acid is a strong oxidizing, corrosive acid capable of esterification with methanol:
HNO3+CH3OH＝＝CH3NO3+H2O
the generated methyl nitrate is unstable and can be used for preparing liquid explosive, and the brisance of the methyl nitrate is equivalent to that of nitroglycerin.
The system of the invention can realize the supplement method of various nitrogen oxides by adding a gas mixer and a nitrogen oxide preprocessor, including NOxDirect utilization, direct utilization of nitric acid, N2O4The nitrogen is supplemented by mixing with nitric acid, supplementing by an ammonia oxidation method or supplementing by reacting sodium nitrite with acid, and the nitrogen element can be supplemented better by flexibly changing the connecting positions of a gas mixer and a nitrogen oxide preprocessor, so that the conversion rate of nitrogen oxide and the selectivity of a target product can be improved without influencing the safety of a system, and the method is particularly suitable for the project of preparing ethylene glycol from coal by an oxalate method.
Drawings
FIG. 1 is a schematic flow diagram of a coal-to-ethylene glycol route;
FIG. 2 is a schematic diagram of a coal-to-ethylene glycol nitrogen oxide make-up system;
FIG. 3 is a schematic diagram of the gas mixer;
FIG. 4 is a schematic diagram of a oxynitride tube;
FIG. 5 is a schematic flow diagram of a NOx pretreater.
In the figure: 1-esterification recycle gas; 2-oxygen; 3-a nitrogen oxide feedstock; 4-nitric acid; 5-methanol; 6-pretreating esterification recycle gas or pre-reaction gas; 7-pretreated nitrogen oxides; 8-oxidizing the condensed gas at the top of the esterification tower; 1A-a compressor; 2A-esterification pre-reactor; 3A-gas mixer; 4A-nitrogen oxide preprocessor; 5A-an oxidative esterification tower; 6A-nitric acid reduction tower; 7A-main tube; 8A-oxynitride tube; an 8A-1-nitrogen oxide inlet pipe; an 8A-2-nitrogen oxide outlet pipe; an 8A-3-NOx outlet orifice; 9A-a preheater; 10A-a buffer tank; 11A-flow controller.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Example 1
As shown in fig. 2-5, a system for supplementing nitrogen oxides to coal-based ethylene glycol comprises a compressor 1A, an esterification pre-reactor 2A, an oxidation esterification tower 5A and a nitric acid reduction tower 6A which are connected in sequence, the system further comprises a gas mixer 3A arranged before the oxidation esterification tower 5A, the gas mixer 3A is connected with a nitrogen oxide pre-processor 4A, the gas mixer 3A comprises a main pipe 7A and a nitrogen oxide pipe 8A arranged inside the main pipe 7A, the nitrogen oxide pre-processor 4A comprises a pre-heater 9A and a buffer tank 10A which are connected in sequence, and nitrogen oxides are supplemented into a reaction system of coal-based ethylene glycol through the gas mixer 3A and the nitrogen oxide pre-processor 4A.
The nitrogen oxide pipe 8A comprises a nitrogen oxide inlet pipe 8A-1, a nitrogen oxide outlet pipe 8A-2 and a nitrogen oxide outlet hole 8A-3, the nitrogen oxide inlet pipe 8A-1 and the nitrogen oxide outlet pipe 8A-2 are fixedly connected, and the nitrogen oxide outlet hole 8A-3 is formed in the nitrogen oxide outlet pipe 8A-2.
The nitrogen oxide outlet openings 8A-3 are uniformly or nearly uniformly distributed small holes in the shape of a circle, square or oval.
The ratio of the inner diameter of the nitrogen oxide outlet pipe 8A-2 to the inner diameter of the main pipe 7A is 0.001 to 0.500: 1.
the nitrogen oxide pre-processor 4A further comprises a flow controller 11A connected to the buffer tank 10A.
A method for supplementing nitrogen oxides in ethylene glycol prepared from coal, wherein N is2O4Supplement, i.e. using N2O4Directly supplements or supplements nitrogen oxide after decomposition, esterification recycle gas 1 and oxygen 2 form pretreated esterification recycle gas or pre-reaction gas 6 in an esterification pre-reactor 2A through a compressor 1A, the pretreated esterification recycle gas or pre-reaction gas enters a main pipe 7A of a gas mixer 3A, nitrogen oxide raw material 3 enters a nitrogen oxide pre-processor 4A to obtain pretreated nitrogen oxide 7, the pretreated nitrogen oxide 7 enters a nitrogen oxide pipe 8A of the gas mixer 3A, the nitrogen oxide enters the main pipe 7A through a nitrogen oxide outlet hole 8A-3 to be uniformly mixed with the pretreated esterification recycle gas or pre-reaction gas 6, and then enters an oxidation esterification tower 5A, methanol 5 is injected into the middle part of the oxidation esterification tower 5A, condensed gas 8 at the top of the oxidation esterification tower is discharged from the top of the oxidation esterification tower 5A, and a crude product obtained at the tower kettle of the oxidation esterification tower 5A enters a nitric acid reduction tower 6A. The replenishing method adopts the system for preparing the glycol and the nitrogen oxide from the coal. The nitrogen oxide was supplemented on a 10t/a coal-to-ethylene glycol carbonylation-esterification model apparatus. Device flow is as followsFIG. 2 shows a circulating gas flow of 3NM3The composition in stable operation stage is as follows: about 10% of NO, about 16% of CO and about 10% of MN, and further about 7% of gas phase methanol and the balance of nitrogen.
The compressor outlet pressure is around 4 bar.
In the driving and stable operation stage, N is used2O4However, as a nitrogen oxide raw material supply system, the supply amount is controlled by a pump. The nitrogen balance of the system is kept by adjusting the supplement amount, namely the total flow of the Nitric Oxide (NO) and the Methyl Nitrite (MN) in the circulating gas is kept constant.
The composition of the circulating gas is analyzed by on-line infrared spectroscopy, and the circulating gas comprises NO, CO and CO2、N2Contents of O and MN.
The nitric acid selectivity is monitored by the content of liquid nitric acid in the tower kettle of the oxidative esterification tower 5A.
The by-products and the amount thereof are monitored by the chromatographic and MS analysis of the condensed gas 8 at the top of the oxidation esterification tower 5A and the liquid at the bottom of the tower.
And measuring the temperature of the nitrogen oxide feeding port by a thermocouple to monitor the temperature condition of the feeding point.
In the starting stage, the liquid in the tower kettle of the nitric acid reduction tower 6A circulates to the tower top, the nitric acid in the liquid reacts with NO which is gradually increased along with the starting to generate methyl nitrite, and the liquid in the tower kettle of the nitric acid reduction tower is discharged to the methanol recovery tower after the nitrogen balance is established and the supplement amount of nitrogen oxides is reduced. Therefore, the MN selectivity and the nitrogen loss rate in the start-up period were calculated as the comparison target from the start of the charging to the time of stable operation of the system. The results are shown in table 1:
TABLE 1N2O4Make-up, using pretreatment and gas distributors
Example 2
A method for supplementing nitrogen oxides in ethylene glycol prepared from coal, wherein N is2O4Mixing the esterification recycle gas 1 with oxygen 2 in an esterification pre-reactor 2A through a compressor 1A to form pretreated esterification recycle gas or pre-reaction gas 6, feeding the pretreated esterification recycle gas or pre-reaction gas 6 into a main pipe 7A of a gas mixer 3A, feeding a nitrogen oxide raw material 3 into a nitrogen oxide pre-processor 4A to obtain pretreated nitrogen oxide 7, feeding the pretreated nitrogen oxide 7 into a nitrogen oxide pipe 8A of the gas mixer 3A, feeding the nitrogen oxide into the main pipe 7A through a nitrogen oxide outlet hole 8A-3 to be uniformly mixed with the pretreated esterification recycle gas or pre-reaction gas 6, and then feeding the mixture into an oxidation esterification tower 5A, injecting methanol 5 into the middle part of an oxidation esterification tower 5A, discharging condensed gas 8 at the top of the oxidation esterification tower from the top of the oxidation esterification tower 5A, feeding a crude product obtained at the tower kettle of the oxidation esterification tower 5A into a nitric acid reduction tower 6A, and supplementing nitric acid 4 between the nitric acid reduction tower 6A and the oxidation esterification tower 5A. The replenishing method adopts the system for preparing the glycol and the nitrogen oxide from the coal. The device flow is shown in fig. 2. The other conditions were the same as in example 1. The results are shown in table 2:
TABLE 2N2O4Mixing with nitric acid, pre-treating and gas distributor
Note: the maximum temperature of the feed point at the steady operation stage of the table above is the temperature of the feed point of the liquid nitric acid.
Example 3
A method for supplementing nitrogen oxides in coal-based ethylene glycol comprises the steps of supplementing nitrogen oxides by a sodium nitrite method, enabling esterification recycle gas 1 and oxygen 2 to form pretreated esterification recycle gas or pre-reaction gas 6 in an esterification pre-reactor 2A through a compressor 1A, enabling the pretreated esterification recycle gas or the pre-reaction gas 6 to enter a main pipe 7A of a gas mixer 3A, enabling a nitrogen oxide raw material 3 to enter a nitrogen oxide pre-processor 4A to obtain pretreated nitrogen oxides 7, enabling the pretreated nitrogen oxides 7 to enter a nitrogen oxide pipe 8A of the gas mixer 3A, enabling the nitrogen oxides to enter the main pipe 7A through nitrogen oxide outlet holes 8A-3 to be uniformly mixed with the pretreated esterification recycle gas or the pre-reaction gas 6, enabling the nitrogen oxides to enter an oxidation esterification, methanol 5 is injected into the middle part of the oxidation esterification tower 5A, condensed gas 8 at the top of the oxidation esterification tower is discharged from the top of the oxidation esterification tower 5A, and a crude product obtained at the tower kettle of the oxidation esterification tower 5A enters a nitric acid reduction tower 6A. The replenishing method adopts the system for preparing the glycol and the nitrogen oxide from the coal. The device flow is shown in fig. 2. The other conditions were the same as in example 1. The results are shown in Table 3:
TABLE 3 reaction supplementation of sodium nitrite and acid, with pretreatment and gas distributor
Example 4
A method for supplementing nitrogen oxides in coal-based ethylene glycol comprises supplementing nitrogen oxides by an ammonia oxidation method, feeding pretreated esterification recycle gas or pre-reaction gas 6 formed by esterification recycle gas 1 in an esterification pre-reactor 2A through a compressor 1A into a main pipe 7A of a gas mixer 3A, feeding nitrogen oxide raw material 3 into a nitrogen oxide pre-processor 4A to obtain pretreated nitrogen oxides 7, feeding the pretreated nitrogen oxides 7 into a nitrogen oxide pipe 8A of the gas mixer 3A, feeding the nitrogen oxides into the main pipe 7A through nitrogen oxide outlet holes 8A-3 to be uniformly mixed with the pretreated esterification recycle gas or the pre-reaction gas 6, feeding the mixture into an oxidation esterification tower 5A, methanol 5 is injected into the middle part of the oxidation esterification tower 5A, condensed gas 8 at the top of the oxidation esterification tower is discharged from the top of the oxidation esterification tower 5A, and a crude product obtained at the tower kettle of the oxidation esterification tower 5A enters a nitric acid reduction tower 6A. The replenishing method adopts the system for preparing the glycol and the nitrogen oxide from the coal. The device flow is similar to that of figure 2 but adjusted accordingly. The other conditions were the same as in example 1. The results are shown in Table 4:
TABLE 4 ammoxidation supplementation with pretreatment and gas distributor
Comparative example 1
A method for supplementing nitrogen oxides in ethylene glycol prepared from coal, wherein N is2O4Supplement, i.e. using N2O4Directly or after decomposition, with nitrogen oxides, butThe gas mixer 3A and the nitrogen oxide preprocessor 4A in the system for preparing glycol and nitrogen oxide from coal are used after being removed, namely, the straight pipe is adopted for feeding, and the nitrogen oxide is not preprocessed, namely, the nitrogen oxide directly enters the main circulating gas pipe through the straight pipe and the tee joint. The other conditions were the same as in example 1. The results are shown in Table 5:
TABLE 5N2O4Direct or decomposed supplement, straight pipe without preprocessor and distributor
Comparative example 2
A method for supplementing nitrogen oxides in ethylene glycol prepared from coal, wherein N is2O4The nitric acid and nitric acid are mixed to supplement nitric oxide, but the gas mixer 3A and the nitric oxide preprocessor 4A in the system for preparing glycol and nitric oxide from coal are used after being removed, namely, a straight pipe is adopted for feeding, and the nitric oxide is not preprocessed, namely, the nitric oxide directly enters a circulating gas main pipe through the straight pipe and a tee joint. The other conditions were the same as in example 2. The results are shown in Table 6:
TABLE 6N2O4Mixed with nitric acid for supplement, straight pipe without preprocessor and distributor
Note: the maximum temperature of the feed point at the steady operation stage of the table above is the temperature of the feed point of the liquid nitric acid.
Comparative example 3
A method for supplementing nitrogen oxides in coal-to-ethylene glycol is used for supplementing nitrogen oxides in a sodium nitrite method, but a gas mixer 3A and a nitrogen oxide preprocessor 4A in a system for preparing the nitrogen oxides in the coal-to-ethylene glycol are removed and then used, namely, straight pipe feeding is adopted, the nitrogen oxides are not preprocessed, and the nitrogen oxides directly enter a circulating gas main pipe through a straight pipe and a tee joint. The other conditions were the same as in example 3. The results are shown in Table 7:
TABLE 7 reaction supplement of sodium nitrite and nitric acid, straight tube without preprocessor and distributor
Comparative example 4
A method for supplementing nitrogen oxides in coal-based ethylene glycol is used for supplementing nitrogen oxides in an ammoxidation method, but a gas mixer 3A and a nitrogen oxide preprocessor 4A in a system for preparing the nitrogen oxides in the coal-based ethylene glycol are used after being removed, namely, the nitrogen oxides are fed by a straight pipe and are not preprocessed, namely, the nitrogen oxides directly enter a main circulating gas pipe through the straight pipe and a tee joint. The other conditions were the same as in example 4. The results are shown in Table 8:
TABLE 8 Ammonia Oxidation supplement, straight tubes without preconditioner and distributor
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A coal-based ethylene glycol nitrogen oxide supplementing system comprises a compressor (1A), an esterification pre-reactor (2A), an oxidation esterification tower (5A) and a nitric acid reduction tower (6A) which are sequentially connected along the feeding direction of reactants,
a gas mixer (3A) is arranged between the esterification pre-reactor (2A) and the oxidation esterification tower (5A), the gas mixer (3A) is connected with a nitrogen oxide pre-processor (4A),
wherein the gas mixer (3A) comprises a main pipe (7A) and a nitrogen oxide pipe (8A) arranged in the main pipe (7A), the main pipe (7A) is arranged in a connecting pipeline, the nitrogen oxide pipe (8A) is provided with a plurality of nitrogen oxide outlet holes (8A-3) on the pipe wall in the main pipe (7A),
the nitrogen oxide pre-processor (4A) comprises a pre-heater (9A) and a buffer tank (10A) which are connected in sequence, and an outlet of the buffer tank (10A) is connected with an inlet of the nitrogen oxide pipe (8A).
2. The system for supplementing nitrogen oxides into ethylene glycol prepared from coal as claimed in claim 1, wherein the nitrogen oxide pipe (8A) comprises a nitrogen oxide inlet pipe (8A-1), a nitrogen oxide outlet pipe (8A-2) and a nitrogen oxide outlet hole (8A-3), the nitrogen oxide inlet pipe (8A-1) is connected with the outlet of the buffer tank (10A), the nitrogen oxide inlet pipe (8A-1) is positioned in the main pipe (7A) and is arranged in parallel with the main pipe (7A) in the axial direction, and the nitrogen oxide outlet hole (8A-3) is opened on the pipe wall of the nitrogen oxide outlet pipe (8A-2).
3. The system for supplementing nitrogen oxides with coal-based glycol as claimed in claim 2, wherein the nitrogen oxide outlet holes (8A-3) are uniformly or approximately uniformly distributed small holes with a circular, square or oval shape.
4. The system for supplementing nitrogen oxides into coal-based ethylene glycol according to claim 2, wherein the ratio of the inner diameter of the nitrogen oxide outlet pipe (8A-2) to the inner diameter of the main pipe (7A) is 0.001-0.500: 1.
5. the system for supplementing nitrogen oxides into coal-based ethylene glycol according to claim 1, wherein the nitrogen oxide pre-processor (4A) is provided with a flow controller (11A) on an outlet pipeline of the buffer tank (10A).
6. The method for supplementing nitrogen oxides in a system for supplementing nitrogen oxides in coal-based ethylene glycol according to any one of claims 1 to 5,
the method comprises the following steps that a gas nitrogen oxide raw material enters a pre-heater (9A) of a nitrogen oxide pre-processor (4A), enters a buffer tank (10A) after being pre-heated by the pre-heater (9A), then enters a nitrogen oxide pipe (8A), enters a main pipe (7A) through a nitrogen oxide outlet hole (8A-3) of the nitrogen oxide pipe (8A), is mixed with esterification recycle gas or pre-reaction gas, and then enters an oxidation esterification tower for reaction;
liquid nitrogen oxide raw materials are added through the nitric acid reduction tower (6A).
7. The method as claimed in claim 6, wherein the gaseous nitrogen oxide raw material is NO or NO2、N2O4、N2O3One or more of them.
8. The system of claim 6, wherein the liquid nitrogen oxide feed is nitric acid.
9. The method as claimed in claim 6, wherein N is N2O4When the mixed nitric acid is added into the system, N is used in the start-up stage2O4Make-up, with nitric acid make-up or N in the steady-state operating phase2O4And nitric acid is simultaneously added.
10. The system for supplementing the nitrogen oxides in the ethylene glycol prepared from coal as claimed in claim 6, wherein the preheating temperature of the preheater (9A) is 20-150 ℃, and the retention time of the nitrogen oxides in the buffer tank (10A) is controlled to be 1-3600 s by the buffer tank (10A) in the method.
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