A deep nitric acid reaction and methanol recovery system and method

Abstract

The present application relates to coal chemical technology field, disclose a kind of depth nitric acid reaction and methanol recovery system, including concentration separation section, pre-reaction section, depth reaction section, side cooling cooler, side pump, tower kettle pump, overhead condenser, overhead separation tank, overhead reflux pump.Deep nitric acid reaction and methanol recovery method are also disclosed, separation and recovery of light component, methanol are realized in concentration separation section in raw material liquid, while nitric acid is concentrated, nitric acid concentrate and raw material gas are contacted in pre-reaction section, depth reaction section countercurrent reaction, after reaction gas phase is merged after going downstream system through the gas outlet in the upper portion of depth reaction section and the top exhaust outlet of pre-reaction section, reaction liquid is discharged through the bottom liquid outlet of depth reaction section to tower kettle pump, and pump outlet sends downstream system.The non-catalytic nitric acid recovery technology, high nitric acid recovery rate, while methanol, methyl formate, methylal, water and other separation can be realized, for synthesis gas to ethylene glycol device safe operation, reduce cost and increase efficiency and environmental protection, it is of great significance.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical technology, specifically relating to a deep nitric acid reaction and methanol recovery system and method. Background Technology

[0002] Ethylene glycol is an important bulk organic chemical raw material, mainly used in polyesters, antifreeze, surfactants, transparent injections, and automotive antifreeze. There are two main methods for producing ethylene glycol: the petroleum route and the coal chemical route. The petroleum route uses ethylene as a raw material, producing ethylene glycol through oxidation and hydration reactions. The coal chemical route produces ethylene glycol from syngas, first by coupling reaction to prepare dimethyl oxalate, and then by hydrogenating dimethyl oxalate to produce ethylene glycol. After nearly ten years of development, coal-to-ethylene glycol technology has become increasingly mature, but material and energy consumption is expected to be further reduced.

[0003] In the coal-to-ethylene glycol route, dimethyl oxalate is prepared via a two-step reaction involving esterification and coupling. The main reaction is as follows: 4NO + O₂ + 4CH₃OH = 4CH₃ONO + 2H₂O 2CH3ONO + 2CO = CH3OOCCOOCH3 + 2NO One of the side reactions is: 2NO + O2 + CH3OH = CH3ONO + HNO3 The byproduct nitric acid typically constitutes 2-5% of the liquid phase in the bottom phase of the esterification reaction tower. The remaining components are mainly methanol, water, dimethyl carbonate, methyl formate, and methyl acetal. Initially, the bottom liquid of the esterification reaction tower was treated by recovering useful components, neutralizing with alkali, and then discharged into the wastewater treatment system. However, this method consumed a large amount of alkali and resulted in significant nitrogen loss, increasing production costs and placing a heavy burden on wastewater treatment. Later, with technological advancements, nitric acid recovery technology was adopted, simultaneously adding a small amount of nitric acid to the system to maintain nitrogen balance and reduce salt emissions after neutralization. Specifically, nitric oxide from the system's circulating gas reacts with nitric acid and methanol to produce methyl nitrite, which is then returned to the system, reducing nitrogen loss. The reaction equation is as follows: 2NO + HNO3 + 3CH3OH = 3CH3ONO + 2H2O Currently, nitric acid recovery technology mainly employs two methods: catalytic recovery and non-catalytic recovery. Patent CN109433200A discloses a low-loading precious metal catalyst for the reduction of dilute nitric acid, its preparation, and its application, achieving a nitric acid conversion rate of over 90% and a nitrite ester selectivity of 100%. This patent requires a precious metal catalyst, which is costly and involves complex subsequent recovery and processing. Patent CN110856818A discloses a catalyst for the reduction and conversion of dilute nitric acid, its preparation method, and its application. When the concentration of dilute nitric acid in the solution is 1-10%, the concentration of nitric acid in the solution after conversion is no higher than 0.1%, and the nitric acid conversion rate is >95%. This patent still requires a catalyst, which generally has a short lifespan and needs to be replaced periodically, increasing production costs.

[0004] Existing non-catalytic nitric acid recovery reaction systems use conventional batch reactors (see...). Figure 1 To prolong the reaction residence time, the reactor volume needs to be large and multiple reactors need to be connected in series. This results in limited space for gas-phase separation, hindering the discharge of reaction products and impeding the forward reaction. Furthermore, a stirrer is required, leading to severe backmixing and the generation of static electricity, posing safety hazards. Additionally, the conversion rate is low, requiring extensive liquid-phase circulation to achieve 60-70% conversion, resulting in significant nitrogen loss, increased consumption of alkali for neutralization, and a heavier burden on wastewater treatment.

[0005] In addition, excess methanol and byproducts such as methyl formate and methyl acetal generated during the reaction need to be separated and recovered using a dedicated distillation system.

[0006] Therefore, the development of a non-catalytic nitric acid recovery technology with high nitric acid recovery rate, while also achieving the separation of methanol, methyl formate, methyl acetal, water, etc., is of great significance for the safe operation, cost reduction and efficiency improvement, and environmental protection of syngas to ethylene glycol plants. Summary of the Invention

[0007] The purpose of this invention is to solve one of the above-mentioned problems by providing a deep nitric acid reaction and methanol recovery system and method.

[0008] The objective of this invention is achieved through the following technical solution: a deep nitric acid reaction and methanol recovery system, comprising a tower body, which from top to bottom includes a concentration and separation section, a pre-reaction section, and multiple deep reaction sections; the concentration and separation section and the pre-reaction section are separated by a second partition, and the two sides of the second partition are connected by a second connecting pipe; the pre-reaction section and the deep reaction section are separated by a first partition, and the two sides of the first partition are connected by a first connecting pipe; a liquid feed distributor is provided in the concentration and separation section to connect to an external nitric acid-containing raw material liquid, a secondary built-in heater is provided below the liquid feed distributor, and packing is provided above the secondary built-in heater; a gas phase outlet is provided at the top of the concentration and separation section, and a side sampling collector is provided in the upper middle part of the concentration and separation section to connect to a methanol side sampling port; exhaust ports are provided at the top of the pre-reaction section and the deep reaction section, and the lower middle parts of the pre-reaction section and the deep reaction section are respectively connected to external raw material gas, and a liquid discharge outlet is provided at the bottom of the deep reaction section.

[0009] In a preferred example, packing is provided between the liquid feed distributor and the secondary built-in heater, and between the liquid feed distributor and the top of the column; packing is also provided between the side collector and the top of the column. Preferably, primary and secondary packing are accumulated between the liquid feed distributor and the secondary built-in heater, tertiary and quaternary packing are accumulated between the liquid feed distributor and the top of the tower, and quinary and sixth-stage packing are accumulated between the side collector and the top of the tower.

[0010] In a preferred example, the lower parts of the pre-reaction section and the deep reaction section are respectively equipped with a secondary gas distributor and a primary gas distributor to connect to external raw material gas; Preferably, a primary liquid distributor is provided at the upper part of the pre-reaction section, and the inlet of the primary liquid distributor is connected to the outlet of the connecting pipe 2. Preferably, a secondary liquid distributor is provided at the upper part of the deep reaction section, and the inlet of the secondary liquid distributor is connected to the outlet of the connecting pipe. Preferably, the two exhaust ports are connected to the downstream system after being joined by a pipeline.

[0011] In a preferred example, the primary gas distributor and the secondary gas distributor are selected from one of the following: straight pipe baffle type, multi-hole straight pipe type, double tangential circulation type, single tangential circulation type, tangential horn type, and double-row blade type distributors. Preferably, the primary liquid distributor and the secondary liquid distributor are selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributors.

[0012] In a preferred example, a primary built-in heater is provided within the deep reaction section; Preferably, the primary built-in heater is located between the primary gas distributor and the secondary liquid distributor.

[0013] In a preferred example, a condenser is provided at the top of the column, and the gas phase outlet of the condenser is connected to the gas phase outlet at the top of the column. Alternatively, the gas phase outlet at the top of the tower can be connected to an external top condenser, the material outlet of the top condenser can be connected to a top separator, the gas phase outlet of the top separator can be connected to a downstream system, the liquid phase outlet can be connected to a top recovery pump, and the outlet of the top recovery pump can be connected to the concentration and separation section and the tank area. Preferably, the top separator is equipped with a demister; More preferably, the demister is selected from one of the following: wire mesh demister, swirl plate demister, and baffle plate demister.

[0014] In a preferred example, the bottom drain outlet of the deep reaction section is connected to a bottom pump, and the bottom pump is connected to a reflux line leading to the pre-reaction section or the deep reaction section. Preferably, the outlet of the top recovery pump is connected to the upper part of the concentration and separation section and to the reflux liquid distributor above the packing in the concentration and separation section. Preferably, the reflux liquid distributor is selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributor.

[0015] In a preferred example, the methanol side inlet is connected to a side inlet cooler, the outlet of the side inlet cooler is connected to a side inlet pump, and the outlet of the side inlet pump is connected to the tank area and the liquid feed distributor. Preferably, the liquid feed distributor is selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributor.

[0016] A method for deep nitric acid reaction and methanol recovery, operating in the above system, includes the following steps: The nitric acid-containing feed liquid is introduced into the concentration and separation section through a liquid feed distributor. The secondary built-in heater is turned on, and the gas and light components are collected at the gas phase outlet at the top of the tower. At the same time, methanol is collected from the upper side outlet in the concentration and separation section. After the liquid level at the bottom of the concentration and separation section (26) reaches a certain value, the electric valve of the connecting pipe 2 is opened, and the raw material gas is introduced into the secondary gas distributor in the pre-reaction section. After the pre-reaction section has reacted for a period of time, the connecting pipe and the first-stage built-in heater are turned on, and the raw material gas is introduced into the first-stage gas distributor in the deep reaction section. After the reaction is complete, the gas in the upper part of the deep reaction section and the gas at the top of the pre-reaction section merge and go to the downstream system, while the reaction liquid is sent to the downstream system through the bottom drain outlet.

[0017] The method for deep nitric acid reaction and methanol recovery also includes the step of separating the gas and light components extracted from the top of the tower through gas-liquid separation, and returning part of the liquid to the concentration and separation section.

[0018] Preferably, the heating temperature of the secondary built-in heater is 40~200℃; When the liquid level at the bottom of the concentration and separation section reaches 3-6 meters, open the electric valve of the connecting pipe. The temperature of the pre-reaction section is 20-200℃, the pressure is 0.01-2.0MPaG, the liquid-to-gas ratio is 0.1-50 (molar ratio), and the residence time is 0.1-50h. When the liquid level at the bottom of the pre-reaction section reaches 2-5 meters, turn on the connecting pipe and the first-stage built-in heater. The temperature of the deep reaction section is 20-200℃, the pressure is 0.01-2.0MPaG, the liquid-to-gas ratio is 0.1-100 (molar ratio), and the residence time is 0.1-100h. The reflux ratio at the top of the tower is 0.1~100.

[0019] The beneficial effects of this invention are as follows: 1. The reboiled feed liquid is separated by packing. The quantity and height of the packing can be determined according to the difficulty of separating the materials. The packing increases the liquid flow space in the tower, increases the gas-liquid contact area, and prolongs the residence time of the gas and liquid phases in the tower, thereby increasing the mass transfer area between the two phases and improving the mass transfer efficiency of the tower. The separated light components are discharged from the top of the tower, and methanol is collected from the side outlet, thereby increasing the concentration of nitric acid entering the pre-reaction section, promoting the reaction and improving the nitric acid conversion rate. The pre-reaction section and the deep reaction section are connected in series in the liquid phase, while the feed gas entering the two sections is connected in parallel. This ensures a high concentration of NO participating in the reaction in the feed gas at all times, and further improves the conversion rate of nitric acid in the deep reaction.

[0020] 2. The raw material gas is the internal circulating gas of the ethylene glycol unit, with the following composition (V%): 5~15% NO, 10~20% CO, 30~45% N2, 5~10% CO2, and 5~10% MN (methyl nitrite). This gas is the internal circulating gas of the ethylene glycol unit and can be used directly internally without the need for additional addition, thus saving material and energy.

[0021] 3. The system of this invention adopts a tower-type concentration separation + pre-reaction + deep reaction system. The raw material liquid containing nitric acid and methanol enters the concentration separation section. After concentration separation, the light components and methanol can be directly separated and recovered. The concentration of recovered methanol is 100%. At the same time, the concentration of nitric acid is concentrated, and the concentration of nitric acid is increased by at least two times. The concentrated nitric acid is more conducive to improving the conversion rate of nitric acid reduction reaction.

[0022] 4. The concentrated nitric acid solution enters the pre-reaction section, and the reacted liquid enters the deep reaction section for further reaction. A mixed gas containing nitric oxide enters both the pre-reaction and deep reaction sections. Based on the reaction kinetics, high concentrations of nitric oxide favor the reduction of low concentrations of nitric acid. Simultaneously, both sections of the reactor are equipped with gas-phase separation spaces, allowing the gaseous product methyl nitrite to be effectively separated from the product, further promoting the reaction towards the product side and thus achieving a deep reaction of nitric acid.

[0023] 5. The pre-reaction section and the deep reaction section can each adjust the temperature, liquid-gas ratio and residence time. Adjusting each parameter according to the degree of reaction further improves the nitric acid conversion rate.

[0024] 6. When the feed nitric acid content is high or the outlet nitric acid content is required to be further reduced, the number of pre-reaction or deep reaction sections can be increased, or the bottom pump can be increased to return to the pre-reaction or deep reaction section, which can further improve the nitric acid conversion rate. If a built-in top condenser is used, the top reflux pump and top separator can be eliminated, and gravity reflux can be used, saving investment and pump energy consumption.

[0025] 7. Compared with the widely used catalyst-equipped reactors, this invention does not require a catalyst and achieves a nitric acid conversion rate of over 99%. It also achieves the separation and recovery of light components and methanol, saving on catalyst costs and alkali consumption, and reducing operating costs by approximately 30%.

[0026] 8. Compared with traditional stirred tank reactors, this invention does not require a stirrer, thus avoiding the safety hazards introduced by the stirring device. Moreover, the nitric acid conversion rate is increased by about 30%, saving the consumption of nitric acid and alkali solution, reducing the energy consumption and investment of subsequent separation and recovery of light components, methanol, etc., and reducing the burden of wastewater treatment. It can save about 40% of operating costs. Attached Figure Description

[0027] Figure 1 This is a standard non-catalytic nitric acid recovery reaction system; Figure 2 The present invention relates to a non-catalytic deep nitric acid reaction and methanol recovery system.

[0028] In the diagram, 100-tower body; 1-first-stage gas distributor; 2-first-stage built-in heater; 3-second-stage liquid distributor; 4-connecting pipe one; 5-baffle one; 6-second-stage gas distributor; 7-first-stage liquid distributor; 8-connecting pipe two; 9-baffle two; 10-second-stage built-in heater; 11-first-stage packing; 12-second-stage packing; 13-liquid feed distributor; 14-third-stage packing; 15-fourth-stage packing; 16-side sampling collector; 17-fifth-stage packing; 18-sixth-stage packing; 19-reflux liquid distributor; 20-tower top condenser; 21-tower top separator; 22-tower top recovery pump; 23-side sampling pump; 24-side sampling cooler; 25-tower bottom pump; 26-concentration and separation section; 27-pre-reaction section; 28-deep reaction section; 29-demister. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but this does not limit the present invention.

[0030] Example 1 A deep nitric acid reaction and methanol recovery system, in the form of a tower, includes a concentration and separation section 26, a pre-reaction section 27, and a deep reaction section 28. The concentration and separation section 26, from bottom to top, is equipped with a secondary built-in heater 10, a primary packing 11, a secondary packing 12, a liquid feed distributor 13, a tertiary packing 14, a quaternary packing 15, a side-collector 16, a quinary packing 17, a sixth-stage packing 18, and a reflux liquid distributor 19. The pre-reaction section 27, from bottom to top, is equipped with a secondary gas distributor 6 and a primary liquid distributor 7. The deep reaction section 28, from bottom to top, is equipped with a primary gas distributor 1, a primary built-in heater 2, and a secondary liquid distributor 3. The concentration and separation section 26 and the pre-reaction section 27 are separated by a partition 29. The liquid enters the upper part of the pre-reaction section 27 from the bottom of the concentration and separation section 26 through the connecting pipe 28. The pre-reaction section 27 and the deep reaction section 28 are separated by a partition 15. The liquid enters the upper part of the deep reaction section 28 from the bottom of the pre-reaction section 27 through the connecting pipe 14.

[0031] The concentration and separation section 26 is equipped with a gas phase outlet at the top. The outlet gas phase is condensed by the top condenser 20 and then enters the top separator 21. The separated gas phase goes to the downstream system, and the liquid phase enters the top recovery pump 22. Part of the liquid phase is returned to the upper part of the concentration and separation section, and part of the liquid phase is collected to the tank area.

[0032] The upper part of the concentration and separation section 26 is equipped with a side sampling port. The side sampling liquid phase is cooled by the side sampling cooler 24 and then enters the side sampling pump 23. The pump outlet goes to the tank area.

[0033] The pre-reaction section 27 and the deep reaction section 28 are equipped with exhaust ports at the top, and the two exhaust ports are connected to the downstream system through pipelines. The deep reaction section 28 is equipped with a drain outlet at the bottom, and a tower bottom pump 25 is installed at the drain outlet, which is connected to the downstream system through pipelines.

[0034] The primary gas distributor 1 and the secondary gas distributor 6 are selected from one of the following types: straight pipe baffle type, multi-hole straight pipe type, double tangential circulation type, single tangential circulation type, tangential horn type, and double-row blade type distributor. The primary liquid distributor 7, the secondary liquid distributor 3, the liquid feed distributor 13, and the reflux liquid distributor 19 are selected from one of the following types: nozzle type, disc type, tube type, trough type, and trough-disc type distributor. The primary built-in heater 2 and the secondary built-in heater 10 are selected from one of the following types: shell and tube type, plate type, finned type, corrugated tube type, and spiral grooved tube type heat exchanger. The demister 29 is selected from one of the following types: wire mesh type, swirl plate type, and baffle plate type demister 29.

[0035] The working principle of the deep nitric acid reaction and methanol recovery system is as follows: Nitric acid-containing feed liquid is evenly distributed into the concentration and separation section 26 via a liquid feed distributor 13. The lower part is the stripping section, where the nitric acid concentration increases towards the bottom; the upper part is the rectification section, where the concentration of light components increases towards the top. A secondary built-in heater 10 at the bottom of the concentration and separation section 26 provides reboiling heat, and a top condenser 20 at the top provides a cold source for the top reflux. The light components collected at the top of the column are mainly methyl formate and methyl acetal, while methanol is collected from the side of the column. The nitric acid content after concentration and separation is approximately 12%, and it enters the pre-reaction section 27 from the bottom of the concentration and separation section 26 via a connecting pipe 2 8. It is evenly distributed into the pre-reaction section 27 via a primary liquid distributor 7. Nitric oxide-containing feed gas enters the pre-reaction section 27 via a secondary gas distributor 6. Nitric oxide, nitric acid, and methanol undergo countercurrent gas-liquid contact in the pre-reaction section 27, resulting in thorough mixing and reaction. The entire system can be controlled by DCS, based on parameters such as liquid level, pressure, flow rate, and temperature, combined with process requirements.

[0036] The liquid at the bottom of the pre-reaction section 27 is evenly distributed into the deep reaction section 28 via the connecting pipe and the primary and secondary liquid distributors 3. The feed gas containing nitric oxide enters the deep reaction section 28 via the primary gas distributor 1. The gas and liquid phases undergo sufficient countercurrent contact and mixing reaction within the deep reaction section of the reactor. The primary built-in heater 2 provides the necessary heat for the reaction. After the reaction, the gas phase merges with the exhaust outlet at the top of the pre-reaction section 27 via the upper gas outlet of the deep reaction section and then goes to the downstream system. The reaction liquid is discharged to the downstream system via the bottom drain outlet of the reactor and the bottom pump 25.

[0037] When the feed nitric acid content is high or a further reduction in the outlet nitric acid content is required, the number of pre-reaction section 27 or deep reaction section 28 can be increased, or the outlet of the bottom pump 25 can be refluxed back to the pre-reaction section 27 or deep reaction section 28, which can further improve the nitric acid conversion rate. Of course, to save investment and pump energy consumption, the external condenser can be replaced with an internal one, installed inside the top of the column, and the condenser gas phase outlet can be connected to the top gas phase outlet of the column, so that gravity reflux can be used, eliminating the need for the top reflux pump and the top separator.

[0038] Example 2 A method for deep nitric acid reaction and methanol recovery, operating in the above system, includes the following steps: First, the nitric acid-containing feed liquid (the bottom liquid of the esterification reaction tower) is introduced into the concentration and separation section 26 through the liquid feed distributor 13. The secondary built-in heater 10 is turned on, and the feed liquid undergoes gas-liquid separation under the action of the packing. Gas and light components are collected at the gas phase outlet at the top of the tower, while methanol is collected at the upper side outlet in the concentration and separation section 26. The gas and light components collected at the top of the tower are condensed and then separated into gas and liquid again, with some liquid returned to the concentration and separation section 26. After the liquid level at the bottom of the concentration and separation section (26) reaches 3-6 meters, open the electric valve of the connecting pipe 28 and introduce NO-containing raw material gas into the secondary gas distributor 6 in the pre-reaction section 27. After the liquid level at the bottom of the pre-reaction section 27 reaches 2-5 meters, open the connecting pipe 4 and the first-stage built-in heater 2, and introduce NO-containing raw material gas into the first-stage gas distributor 1 in the deep reaction section 28. During the reaction, the heating temperature of the secondary built-in heater 10 is controlled at 40~200℃; the temperature of the pre-reaction section 27 is 20~200℃, the pressure is 0.01~2.0MPaG, the liquid-to-gas ratio is 0.1~50 (molar ratio), and the residence time is 0.1~50h; the temperature of the deep reaction section 28 is 20~200℃, the pressure is 0.01~2.0MPaG, the liquid-to-gas ratio is 0.1~100 (molar ratio), and the residence time is 0.1~100h; the reflux ratio at the top of the column is 0.1~100.

[0039] The NO-containing feed gas is selected from the circulating gas in the ethylene glycol unit, and its composition (V%) is: 5~15% NO, 10~20% CO, 30~45% N2, 5~10% CO2, and 5~10% MN (methyl nitrite).

[0040] With a continuous supply of raw material liquid and raw material gas, and with the liquid levels in the pre-reaction section 27 and the deep reaction section 28 maintained, the above three stages proceed continuously.

[0041] Finally, in addition to the recovered methanol, the gas from the top of the deep reaction section 28 and the gas from the top of the pre-reaction section 27 are combined and sent to the downstream system, while the reaction liquid is sent to the downstream system via the bottom drain outlet and the bottom pump 25.

[0042] Example 3 This embodiment illustrates the processing of a specific raw material liquid composition in the above system: The feed liquid is a 20t / h feed liquid containing nitric acid, methanol, etc., with the following specific composition:

[0043] The above-mentioned raw material liquid enters the concentration and separation section 26 via the liquid feed distributor 13. Within this section, the gas and liquid phases are in equilibrium. The lighter components flow upwards towards the top of the column, increasing in concentration, while the heavier components flow downwards towards the bottom, also increasing in concentration. The gas phase at the top of the column is condensed to 10-40°C by the top condenser 20 and then sent to the top separator 21 for further separation. The separated gas phase enters the downstream system, while the separated liquid phase is partially refluxed and partially collected, with a reflux ratio of 0.1-50. The collected liquid phase flow rate is 1.9 t / h, and its composition is as follows:

[0044] A side-collector 16 is installed in the upper part of the concentration and separation section 26. Methanol collected from the side-collector 16 is cooled to 40°C and then pumped to the tank area. The side-collected methanol content is 100%, and the output rate is 10t / h.

[0045] The bottom of the concentration and separation section 26 contains a concentrated nitric acid solution after the separation of light components and methanol, with a flow rate of 8.1 t / h. The specific components are as follows:

[0046] Nitric acid concentrate enters the pre-reaction section 27 via connecting pipe 2 (8), while the feed gas enters the pre-reaction section 27 via secondary gas distributor 6. The nitric acid concentrate is evenly distributed into the pre-reaction section 27 from the primary liquid distributor 7. The nitric acid concentrate flows from top to bottom, while the feed gas flows from bottom to top. The gas and liquid phases come into countercurrent contact within the pre-reaction section 27, resulting in mixing and reaction. The reaction temperature in the pre-reaction section 27 is 20–200°C, the pressure is 0.01–2.0 MPaG, the liquid-to-gas ratio is 0.1–50 (molar ratio), the residence time is 0.1–50 h, and the nitric acid content in the outlet reaction liquid is 0.1%. After the reaction, the gas is sent to the downstream system through the exhaust port at the top of the pre-reaction section 27. The liquid at the bottom of the pre-reaction section 27 is evenly distributed into the deep reaction section 28 of the system via the connecting pipe and the first- to second-stage liquid distributor 3. The feed gas enters the deep reaction section 28 via the first-stage gas distributor 1. The gas and liquid phases undergo sufficient countercurrent contact and mixing reaction within the deep reaction section 28. The first-stage built-in heater 2 provides the required heat for the reaction. The feed gas is the circulating gas from the ethylene glycol unit, with the following composition (V%): 5~15% NO, 10~20% CO, 30~45% N2, 5~10% CO2, and 5~10% MN (methyl nitrite). The reaction temperature in the deep reaction section 28 is 20~200℃, the pressure is 0.01~2.0MPaG, the liquid-to-gas ratio is 0.1~100 (molar ratio), the residence time is 0.1~100h, and the nitric acid content in the outlet reaction liquid is 0.04%. After the reaction, the gas phase merges with the exhaust outlet at the top of the pre-reaction section 27 after passing through the upper gas outlet of the deep reaction section 28 and then goes to the downstream system. The reaction liquid goes to the bottom drain outlet of the deep reaction section 28 and then to the bottom pump 25, and the pump outlet is sent to the downstream system.

[0047] Example 4 like Figure 2 The diagram shows a structural schematic of a deep nitric acid reaction and methanol recovery system according to the present invention, including a concentration and separation section 26, a pre-reaction section 27, a deep reaction section 28, a side-entry cooler 24, a side-entry pump 23, a bottom pump 25, a top condenser 20, a top separation tank 21, and a top recovery pump 22.

[0048] A 20 t / h feed liquid is introduced into the concentration and separation section 26. The feed liquid contains 5% nitric acid and 60% methanol. The bottom temperature of the concentration and separation section 26 is 80°C, and the top temperature is 65°C. The steam flow rate of the secondary built-in heater 10 is 8 t / h, the condenser temperature of the top condenser 20 is 20°C, the top reflux ratio is 5, the top liquid phase flow rate is 1.9 t / h, and the side methanol flow rate is 10 t / h. Simultaneously, feed gas is introduced into the system's pre-reaction section 27 and deep reaction section 28. The feed gas is the circulating gas from the ethylene glycol unit, and its nitric oxide content is 10%. In the concentration and separation section 26, the light components and methanol are separated and recovered. At the same time, the nitric acid is concentrated to a concentration of 12.3 wt%. Nitric acid concentrate enters the pre-reaction section 27 at a flow rate of 8.1 t / h. The gas and liquid phases react countercurrently in the pre-reaction section 27. The reaction temperature in the pre-reaction section 27 is 75℃, the pressure is 0.5 MPaG, the liquid-to-gas ratio is 11 (molar ratio), the residence time is 0.5 h, and the nitric acid content in the outlet reaction liquid is 0.1%. After reacting in the pre-reaction section 27, the liquid flows into the deep reaction section 28 by gravity, where it further reacts with the incoming feed gas. The reaction temperature in the deep reaction section 28 is 90℃, the pressure is 0.55 MPaG, and the feed gas rate is 15000 Nm³. 3 The steam flow rate of the first-stage built-in heater 1 is 5t / h, the nitric acid content at the reactor outlet is 0.04%, and the nitric acid conversion rate is approximately 99.72%.

[0049] Example 5 like Figure 2 The diagram shows a structural schematic of a deep nitric acid reaction and methanol recovery system according to the present invention, including a concentration and separation section 26, a pre-reaction section 27, a deep reaction section 28, a side-entry cooler 24, a side-entry pump 23, a bottom pump 25, a top condenser 20, a top separation tank 21, and a top recovery pump 22.

[0050] A 20 t / h feed liquid is introduced into the concentration and separation section 26. The feed liquid contains 2% nitric acid and 60% methanol. The bottom temperature of the concentration and separation section 26 is 80°C, and the top temperature is 65°C. The steam flow rate of the secondary built-in heater 10 is 8 t / h, the condensation temperature of the top condenser 20 is 20°C, the top reflux ratio is 5, the top liquid phase flow rate is 1.9 t / h, and the side methanol flow rate is 10 t / h. Simultaneously, feed gas is introduced into the system's pre-reaction section 27 and deep reaction section 28. The feed gas is the circulating gas from the ethylene glycol unit, and its nitric oxide content is 10%. In the concentration and separation section 26, the light components and methanol are separated and recovered. At the same time, the nitric acid is concentrated to a concentration of 4.92 wt%. Nitric acid concentrate enters the pre-reaction section 27 at a flow rate of 8.1 t / h. The gas and liquid phases react countercurrently within the reactor. The reaction temperature in pre-reaction section 27 is 75℃, the pressure is 0.5 MPaG, the liquid-to-gas ratio is 1:1 (molar ratio), the residence time is 0.5 h, and the nitric acid content in the outlet reaction liquid is 0.1%. After reacting in pre-reaction section 27, the liquid flows by gravity into the deep reaction section 28, where it further reacts with the incoming feed gas. The reaction temperature in deep reaction section 28 is 90℃, the pressure is 0.55 MPaG, and the feed gas rate is 15000 Nm³. 3 The steam flow rate of the first-stage built-in heater 1 is 5t / h, the nitric acid content at the reactor outlet is 0.03%, and the nitric acid conversion rate is approximately 99.4%.

[0051] Example 6 like Figure 2 The diagram shows a structural schematic of a deep nitric acid reaction and methanol recovery system according to the present invention, including a concentration and separation section 26, a pre-reaction section 27, a deep reaction section 28, a side-entry cooler 24, a side-entry pump 23, a bottom pump 25, a top condenser 20, a top separation tank 21, and a top recovery pump 22.

[0052] A 20 t / h feed liquid is introduced into the concentration and separation section 26. The feed liquid contains 3% nitric acid and 60% methanol. The bottom temperature of the concentration and separation section 26 is 80℃, and the top temperature is 65℃. The steam flow rate of the secondary built-in heater 10 is 8 t / h, the condenser temperature of the top condenser 20 is 20℃, the top reflux ratio is 5, the top liquid phase flow rate is 1.9 t / h, and the side methanol flow rate is 10 t / h. Simultaneously, feed gas is introduced into the system's pre-reaction section 27 and deep reaction section 28. The feed gas is the circulating gas from the ethylene glycol unit, and its nitric oxide content is 10%. In the concentration and separation section 26, the light components and methanol are separated and recovered. At the same time, the nitric acid is concentrated to a concentration of 7.38 wt%. Nitric acid concentrate enters pre-reaction section 27 at a flow rate of 8.1 t / h. The gas and liquid phases react countercurrently within the system. The reaction temperature in pre-reaction section 27 is 75℃, the pressure is 0.5 MPaG, the liquid-to-gas ratio is 11 (molar ratio), the residence time is 0.5 h, and the nitric acid content in the outlet reaction liquid is 0.1%. After reacting in pre-reaction section 27, the liquid flows into deep reaction section 28 by gravity, where it further reacts with the incoming feed gas. The reaction temperature in deep reaction section 28 is 90℃, the pressure is 0.55 MPaG, and the feed gas rate is 15000 Nm³. 3 The steam flow rate of the first-stage built-in heater 1 is 5t / h, the nitric acid content at the reactor outlet is 0.04%, and the nitric acid conversion rate is approximately 99.5%.

[0053] Comparative Example 1 like Figure 1 The existing system shown introduces a 20 t / h feed liquid into a stirred tank reactor. The feed liquid contains 5% nitric acid and 60% methanol. Simultaneously, feed gas is introduced into the parallel stirred tank reactors. The feed gas is recycled gas from the ethylene glycol unit and contains 10% nitric oxide. Under the stirring action of the agitator, a nitric acid reduction reaction occurs at a temperature of 80°C and a pressure of 0.45 MPaG. The feed gas feed rate is 20,000 Nm³. 3 / h, circulating pump flow rate 600m³ / h, nitric acid content in the reaction liquid at the reactor outlet is 1.75%, and nitric acid conversion rate is about 65%.

[0054] Comparative Example 2 like Figure 1 The existing system shown introduces a 20 t / h feed liquid into a stirred tank reactor. The feed liquid contains 2% nitric acid and 60% methanol. Simultaneously, feed gas is introduced into the parallel stirred tank reactors. The feed gas is recycled gas from the ethylene glycol unit and contains 10% nitric oxide. Under the stirring action of the agitator, a nitric acid reduction reaction occurs at a temperature of 80°C and a pressure of 0.45 MPaG. The feed gas feed rate is 20,000 Nm³. 3 / h, circulating pump flow rate 600m³ / h, nitric acid content in the reaction liquid at the reactor outlet is 0.8%, and nitric acid conversion rate is about 60%.

[0055] Comparative Example 3 like Figure 1 The existing system shown introduces a 20 t / h feed liquid into a stirred tank reactor. The feed liquid contains 3% nitric acid and 60% methanol. Simultaneously, feed gas is introduced into the parallel stirred tank reactors. The feed gas is recycled gas from the ethylene glycol unit and contains 10% nitric oxide. Under the stirring action of the agitator, a nitric acid reduction reaction occurs at a temperature of 80°C and a pressure of 0.45 MPaG. The feed gas feed rate is 20,000 Nm³. 3 / h, circulating pump flow rate 600m³ / h, nitric acid content in the reaction liquid at the reactor outlet 1.14%, nitric acid conversion rate approximately 62%.

[0056] It should be noted that, depending on actual needs, the number of pre-reaction section 27 or deep reaction section 28 can be increased, and a reflux line can be added to the bottom pump 25 to the pre-reaction section 27 or deep reaction section 28 to further improve the nitric acid conversion rate. The quantity and parameters of the packing layer in the concentration and separation section 26 can be adjusted as needed.

[0057] As an alternative, the top condenser 20 can also be a built-in condenser, with corresponding adjustments to the piping.

[0058] The above description is intended to be illustrative and not restrictive. Those skilled in the art can make variations, modifications, substitutions, and alterations to the above embodiments within the scope of this disclosure. Moreover, the above examples (or one or more of them) can be used in combination with each other, and these embodiments can be combined with each other in various combinations or arrangements.

Claims

1. A non-catalytic nitric acid reaction and methanol recovery system, characterized in that, It includes a tower body (100), which from top to bottom includes a concentration and separation section (26), a pre-reaction section (27) and a deep reaction section (28). The concentration and separation section (26) and the pre-reaction section (27) are separated by a partition plate two (9), and the two sides of the partition plate two (9) are connected by a connecting pipe two (8); The pre-reaction section (27) and the deep reaction section (28) are separated by a partition (5), and the two sides of the partition (5) are connected by a connecting pipe (4); The concentration and separation section (26) is equipped with a liquid feed distributor (13) to connect to an external nitric acid-containing raw material liquid. A secondary built-in heater (10) is installed below the liquid feed distributor (13), and packing is installed above the secondary built-in heater (10). The concentration and separation section (26) has a gas phase outlet at the top, and a side collection collector (16) is installed in the upper part of the concentration and separation section (26) to connect to a methanol side collection port. The pre-reaction section (27) and the deep reaction section (28) are both provided with exhaust ports at the top. The lower part of the pre-reaction section (27) and the deep reaction section (28) are respectively connected to external raw material gas. The deep reaction section (28) is provided with a liquid discharge outlet at the bottom. Packing material is provided between the liquid feed distributor (13) and the secondary built-in heater (10) and between the liquid feed distributor (13) and the top of the tower. Packing material is also provided between the side collector (16) and the top of the tower. The liquid feed distributor (13) and the secondary built-in heater (10) are filled with primary packing (11) and secondary packing (12), the liquid feed distributor (13) and the top of the tower are filled with tertiary packing (14) and quaternary packing (15), and the side collector (16) and the top of the tower are filled with quinary packing (17) and sixth packing (18). A condenser is installed inside the top of the tower, and the gas phase outlet of the condenser is connected to the gas phase outlet at the top of the tower. Alternatively, the gas phase outlet at the top of the tower is connected to the top condenser (20), the material outlet of the top condenser (20) is connected to the top separator (21), the gas phase outlet of the top separator (21) is connected to the downstream system, the liquid phase outlet is connected to the top recovery pump (22), and the outlet of the top recovery pump (22) is connected to the concentration and separation section (26) and the tank area. The top separator (21) is equipped with a demister (29). The bottom drain outlet of the deep reaction section (28) is connected to the bottom pump (25), and the bottom pump (25) is connected to the reflux pipeline leading to the pre-reaction section or the deep reaction section; The outlet of the top recovery pump (22) is connected to the upper part of the concentration and separation section (26) and to the reflux liquid distributor (19) above the packing in the concentration and separation section (26); the methanol side intake port is connected to the side intake cooler (24), the outlet of the side intake cooler (24) is connected to the side intake pump (23), and the outlet of the side intake pump (23) is connected to the tank area and the liquid feed distributor (13).

2. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, characterized in that, The lower parts of the pre-reaction section (27) and the deep reaction section (28) are respectively equipped with a secondary gas distributor (6) and a primary gas distributor (1) to connect to external raw material gas; The pre-reaction section (27) is equipped with a primary liquid distributor (7) at the top, and the inlet of the primary liquid distributor (7) is connected to the outlet of the connecting pipe (8). The upper part of the deep reaction section (28) is provided with a secondary liquid distributor (3) and the inlet of the secondary liquid distributor (3) is connected to the outlet of the connecting pipe (4); The two exhaust ports are connected to the downstream system after they merge through pipelines.

3. The non-catalytic nitric acid reaction and methanol recovery system according to claim 2, characterized in that, The primary gas distributor (1) and the secondary gas distributor (6) are selected from one of the following: straight pipe baffle type, multi-hole straight pipe type, double tangential circulation type, single tangential circulation type, tangential horn type, and double-row blade type distributors; The primary liquid distributor (7) and the secondary liquid distributor (3) are selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributor.

4. The non-catalytic nitric acid reaction and methanol recovery system according to claim 2, characterized in that, The deep reaction section (28) is equipped with a first-stage built-in heater (2); The primary built-in heater (2) is located between the primary gas distributor (1) and the secondary liquid distributor (3).

5. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, characterized in that, The demister (29) is selected from one of the following: wire mesh, swirl plate, and baffle plate demisters.

6. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, characterized in that, The reflux liquid distributor (19) is selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributor.

7. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, characterized in that, The liquid feed distributor (13) is selected from one of the following: nozzle type, disc type, pipe type, trough type, and trough-disc type distributor.

8. A method for deep nitric acid reaction and methanol recovery, characterized in that, The method is operated in the system described in claim 4 above: Nitric acid-containing feed liquid is introduced into concentration and separation section (26) through liquid feed distributor (13), and secondary built-in heater (10) is turned on. Gas and light components are collected at the gas phase outlet at the top of the tower, and methanol is collected at the upper side outlet in concentration and separation section (26). After the liquid level at the bottom of the concentration and separation section (26) reaches a certain value, the electric valve of the connecting pipe (8) is opened, and the raw material gas is introduced into the secondary gas distributor (6) in the pre-reaction section (27); After the pre-reaction section (27) has reacted for a period of time, the connecting pipe (4) and the first-stage built-in heater (2) are turned on, and the raw material gas is introduced into the first-stage gas distributor (1) in the deep reaction section (28); After the reaction is completed, the gas in the upper part of the deep reaction section (28) and the gas at the top of the pre-reaction section (27) are combined and sent to the downstream system, while the reaction liquid is sent to the downstream system through the bottom drain outlet.

9. The method for deep nitric acid reaction and methanol recovery according to claim 8, characterized in that, It also includes the step of separating the gas and light components extracted from the top of the tower through gas-liquid separation, and returning part of the liquid to the concentration and separation section (26); The heating temperature of the secondary built-in heater (10) is 40~200℃; When the liquid level at the bottom of the concentration and separation section (26) reaches 3-6 meters, the electric valve of the connecting pipe (8) is opened. The temperature of the pre-reaction section (27) is 20-200℃, the pressure is 0.01-2.0MPaG, the liquid-to-gas ratio is 0.1-50, the liquid-to-gas ratio is the molar ratio, and the residence time is 0.1-50h. When the liquid level at the bottom of the pre-reaction section (27) reaches 2-5 meters, the connecting pipe (4) and the first-stage built-in heater (2) are turned on. The temperature of the deep reaction section (28) is 20-200℃, the pressure is 0.01-2.0MPaG, the liquid-to-gas ratio is 0.1-100, the liquid-to-gas ratio is the molar ratio, and the residence time is 0.1-100h. The reflux ratio at the top of the tower is 0.1~100.

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