CN117654399A - Deep nitric acid reaction and methanol recovery system and method - Google Patents

Abstract

The invention relates to the technical field of coal chemical industry and discloses a deep nitric acid reaction and methanol recovery system which comprises a concentration separation section, a pre-reaction section, a deep reaction section, a side extraction cooler, a side extraction pump, a tower kettle pump, a tower top condenser, a tower top separation tank and a tower top reflux pump. The method comprises the steps of concentrating raw material liquid in a concentration and separation section, concentrating nitric acid, carrying out countercurrent contact reaction on the concentrated nitric acid liquid and raw material gas in a pre-reaction section and a deep reaction section, merging gas phase after reaction through a gas outlet at the upper part of the deep reaction section and an exhaust outlet at the top of the pre-reaction section, delivering the reacted liquid to a downstream system, delivering the reacted liquid to a tower kettle pump through a liquid outlet at the bottom of the deep reaction section, and delivering the pump to the downstream system. The non-catalytic nitric acid recovery technology has high nitric acid recovery rate, can realize the separation of methanol, methyl formate, methylal, water and the like, and has great significance for safe operation, cost reduction, synergy and environmental protection of a device for preparing ethylene glycol from synthesis gas.

Description

A deep nitric acid reaction and methanol recovery system and method

Technical field

The invention belongs to the technical field of coal chemical industry, and specifically relates to a deep nitric acid reaction and methanol recovery system and method.

Background technique

Ethylene glycol is an important bulk organic chemical raw material, mainly used in polyester, antifreeze, surfactant, transparent injection, automobile antifreeze and other fields. There are two main methods of producing ethylene glycol: petroleum route and coal chemical route. The petroleum route uses ethylene as raw material to prepare ethylene glycol through oxidation and hydration reactions. The coal chemical industry route is to produce ethylene glycol from synthesis gas. First, dimethyl oxalate is prepared through a coupling reaction, and dimethyl oxalate is hydrogenated to produce ethylene glycol. Due to my country's energy structure characteristics of "rich coal, poor oil and little gas", the development of coal chemical tools is of great strategic significance. After nearly ten years of development, coal-to-ethylene glycol technology has become increasingly mature, but material and energy consumption are expected to be further reduced.

In the coal-to-ethylene glycol route, dimethyl oxalate is prepared through a two-step reaction of esterification and coupling. The main reaction is:

4NO+O ₂ +4CH ₃ OH=4CH ₃ ONO+2H ₂ O

2CH ₃ ONO+2CO=CH ₃ OOCCOOCH ₃ +2NO

One of the side effects is:

2NO+O ₂ +CH ₃ OH=CH ₃ ONO+HNO ₃

The content of the by-product nitric acid in the liquid phase of the esterification reaction tower is generally 2~5%, and the remaining components are mainly methanol, water, dimethyl carbonate, methyl formate, methylal, etc. Initially, the esterification reaction tower still liquid is recovered from useful components, neutralized by adding alkali liquid, and then discharged into the sewage treatment system. However, this treatment method consumes a large amount of alkali liquid and suffers serious loss of nitrogen in the system, which increases production costs and places a great burden on sewage treatment. After technological development, nitric acid recovery technology was adopted, and a small amount of nitric acid was added to the system to maintain the nitrogen balance of the system and reduce salt emissions after neutralization. That is, the nitric oxide in the system circulating gas is used to react with nitric acid and methanol to produce methyl nitrite and return to the system to reduce the loss of nitrogen. The reaction equation is:

2NO+HNO ₃ +3CH ₃ OH=3CH ₃ ONO+2H ₂ O

At present, nitric acid recovery technology mainly adopts two methods: catalytic recovery and non-catalytic recovery. Patent CN109433200A discloses a low-loading precious metal catalyst for dilute nitric acid reduction, its preparation and application. The nitric acid conversion rate reaches more than 90%, and the nitrite ester selectivity reaches 100%. This patent requires the use of precious metal catalysts. The cost of the catalyst is high and subsequent recycling and processing is troublesome. Patent CN110856818A discloses a catalyst for the reduction and conversion of dilute nitric acid and its preparation method and 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 not higher than 0.1%, and the nitric acid conversion rate is >95%. , this patent still requires the use of a catalyst, which generally has a short service life and needs to be replaced regularly, which increases production costs.

The existing non-catalytic nitric acid recovery reaction system uses ordinary kettle reactors (see Figure 1). In order to extend the reaction residence time, the reactor volume must be large and multiple reactors must be connected in series. The gas phase separation space is limited, which is not conducive to the discharge of reaction products. , which is not conducive to the positive direction of the reaction; it also requires the use of a stirrer for stirring, serious back-mixing, and easy generation of static electricity, posing safety hazards. In addition, its conversion rate is low, and a large amount of liquid phase circulation is required to achieve a conversion rate of 60~70%, resulting in a large loss of nitrogen, increased consumption of alkali for neutralization, and increasing the burden of sewage treatment.

In addition, excess methanol during the reaction and methyl formate, methylal, etc. generated by side reactions require a special distillation system to be separated and recovered.

Therefore, a non-catalytic nitric acid recovery technology was developed, which has a high nitric acid recovery rate and can simultaneously achieve the separation of methanol, methyl formate, methylal, water, etc., which is important for the safe operation of the synthesis gas to ethylene glycol unit, cost reduction and increase It is of great significance to efficiency and environmental protection.

Contents of the invention

The purpose of the present invention is to solve one of the above problems and provide a deep nitric acid reaction and methanol recovery system and method.

The object of the present invention is achieved through the following technical solutions: a deep nitric acid reaction and methanol recovery system, including a tower body, which includes a concentration separation section, a pre-reaction section and a multi-stage deep reaction section from top to bottom; The concentration separation section and the pre-reaction section are separated by a partition plate two, and both sides of the partition plate two are connected with a connecting pipe two; the pre-reaction section and the depth reaction section are separated by a partition plate one, and the two sides of the partition plate one are connected Connected with a connecting pipe; a liquid feed distributor is provided in the concentration and separation section to connect the external nitric acid-containing raw material liquid, a secondary built-in heater is provided below the liquid feed distributor, and a filler is provided above the secondary built-in heater ; The top of the tower of the concentration and separation section is provided with a gas phase outlet, and the middle and upper part of the concentration and separation section is provided with a side collection collector to connect the methanol side collection port; the tops of the pre-reaction section and the depth reaction section are equipped with exhaust ports, so The middle and lower parts of the pre-reaction section and the deep reaction section are respectively connected to external feed gas, and a drainage outlet is provided at the bottom of the deep reaction section.

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 tower, and between the side collection collector and the top of the tower Set with filler;

Preferably, primary fillers and secondary fillers are accumulated between the liquid feed distributor and the secondary built-in heater, and third-stage fillers and fourth-stage fillers are accumulated between the liquid feed distributor and the top of the tower, so There are five levels of packing and six levels of packing accumulated between the side collection collector and the top of the tower.

In a preferred example, a secondary gas distributor and a primary gas distributor are respectively provided in the middle and lower parts of the pre-reaction section and the deep reaction section to connect 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 communication pipe one;

Preferably, the two exhaust ports are connected to the downstream system after being merged through pipelines.

In a preferred example, the primary gas distributor and the secondary gas distributor are straight tube baffle type, porous straight tube type, double tangential circulation type, single tangential circulation type, tangential horn type, One of the double row blade distributors;

Preferably, the primary liquid distributor and the secondary liquid distributor are selected from the group consisting of nozzle type, disk type, tube type, trough type, and trough plate type distributors.

In a preferred example, a first-level built-in heater is provided in the deep reaction section;

Preferably, the first-level built-in heater is arranged between the first-level gas distributor and the second-level liquid distributor.

In a preferred example, a condenser is provided in 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;

Or the gas phase outlet at the top of the tower is externally connected to the tower top condenser, the material outlet of the tower top condenser is connected to the tower top separation tank, the gas phase outlet of the tower top separation tank is connected to the downstream system, the liquid phase outlet is connected to the tower top recovery pump, and the tower top recovery pump outputs The feed port is connected all the way to the concentration and separation section, and all the way to the tank area;

Preferably, a demister is provided in the separation tank at the top of the tower;

More preferably, the demister is selected from the group consisting of wire mesh, swirl plate type and baffle type demister.

In a preferred example, the drainage outlet at the bottom of the deep reaction section is connected to a column still pump, and the column pump is connected to a reflux line leading to the pre-reaction section or the deep reaction section;

Preferably, the discharge port of the tower top recovery pump is connected all the way to the upper part of the concentration and separation section, and is connected to the reflux liquid distributor above the packing in the concentration and separation section;

Preferably, the reflux liquid distributor is one of nozzle type, disk type, tube type, trough type, and trough disk type distributor.

In a preferred example, the methanol side extraction port is externally connected to a side extraction cooler, the outlet of the side extraction cooler is connected to a side extraction pump, and the outlet of the side extraction pump is connected to the tank area and the liquid feed distributor;

Preferably, the liquid feed distributor is selected from the group consisting of nozzle type, disk type, tube type, trough type, and trough disk type distributor.

A method for deep nitric acid reaction and methanol recovery, operating in the above system, includes the following steps:

Introduce the nitric acid-containing raw material liquid into the concentration and separation section through the liquid feed distributor, turn on the secondary built-in heater, and extract gas and light components at the gas phase outlet at the top of the tower. At the same time, methanol is extracted from the upper side outlet of the concentration and separation section;

After the liquid level at the bottom of the concentration and separation section (26) reaches a certain value, open the electric valve of the second connecting pipe, and the secondary gas distributor in the pre-reaction section flows into the raw material gas;

After the pre-reaction section reacts for a period of time, open the first and first-level built-in heaters of the connecting pipe, and the first-level gas distributor in the deep reaction section introduces the raw material gas;

After the reaction, the gas at the top of the deep reaction section and the top of the pre-reaction section merge and go to the downstream system, and the reaction liquid is sent to the downstream system through the liquid outlet at the bottom of the tower.

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

Preferably, the heating temperature of the secondary built-in heater is 40~200°C;

When the liquid level at the bottom of the concentration and separation section reaches 3 to 6 meters, open the second electric valve of the connecting pipe. The temperature of the pre-reaction section is 20 to 200°C, the pressure is 0.01 to 2.0 MPaG, the liquid-to-gas ratio is 0.1 to 50 (molar ratio), and the residence time 0.1~50h;

When the liquid level at the bottom of the pre-reaction section reaches 2 to 5 meters, turn on the built-in heaters of the first and first levels of the connecting pipe. The temperature of the deep reaction section is 20 to 200°C, the pressure is 0.01 to 2.0 MPaG, and the liquid-to-gas ratio is 0.1 to 100 (mol Ratio), residence time 0.1~100h;

The reflux ratio at the top of the tower is 0.1~100.

The beneficial effects of the present invention are as follows:

1. Separate the reboiled raw material liquid through packing. The number and height of the packing can be determined according to the difficulty of separating the materials. The packing is used to increase the liquid flow space in the tower, increase the gas-liquid contact area, and extend the gas-liquid two-phase The residence time in the tower increases the mass transfer area between the two-phase materials and improves the mass transfer efficiency of the tower;

The separated light components are discharged from the top of the tower, and methanol is taken out from the side outlet, thereby increasing the concentration of nitric acid entering the pre-reaction section, promoting the progress of the reaction, and improving the nitric acid conversion rate;

The pre-reaction section and the deep reaction section are connected in liquid phase in series, and the raw gas entering the two sections is connected in parallel, which can always ensure the high concentration of NO in the raw gas participating in the reaction, and further improve the conversion rate of nitric acid in the deep reaction.

2. The raw material gas adopts the circulating gas in the ethylene glycol device. The composition (V%): 5~15% NO, CO10~20%, N ₂ 30~45%, CO ₂ 5~10%, MN (methyl nitrite ) 5~10%. This gas is the circulating gas in the ethylene glycol unit and can be directly used internally without additional addition, saving materials and energy.

3. The system of the present invention adopts a one-tower concentration and separation + pre-reaction + deep reaction system. The raw material liquid containing nitric acid and methanol enters the concentration and separation section. After concentration and separation, the light components and methanol can be directly separated and recovered, and methanol can be recovered. The concentration is 100%, and the nitric acid is concentrated at the same time. The nitric acid concentration is at least doubled. The concentrated nitric acid is more conducive to improving the conversion rate of the nitric acid reduction reaction.

4. The concentrated nitric acid liquid enters the pre-reaction section, the reacted liquid enters the deep reaction section for further reaction, and the mixed gas containing nitric oxide enters the pre-reaction section and the deep reaction section respectively. According to the study of the reaction kinetics of this reaction, high High concentrations of nitric oxide are beneficial to the reduction reaction of low concentrations of nitric acid. At the same time, both sections of the reactor are equipped with gas phase separation spaces. The gas phase product of the reaction, methyl nitrite, can be well separated from the product, further promoting the reaction to move to the side of the product, thereby achieving a deep reaction of nitric acid.

5. The pre-reaction section and the deep reaction section can adjust the temperature, liquid-gas ratio, and residence time respectively, and adjust various parameters according to the degree of reaction, further improving the nitric acid conversion rate.

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 sections or deep reaction sections can be increased, or the reflux of the tower tank pump can be increased to return to the pre-reaction section or deep reaction section, which can further improve the nitric acid conversion. efficiency; if a built-in tower top condenser is used, the tower top reflux pump and tower top separation tank can be omitted, and gravity reflux is used, saving investment and pump energy consumption.

7. Compared with the currently widely used reactors with catalysts, the present invention does not require a catalyst, and the nitric acid conversion rate is as high as more than 99%. At the same time, it realizes the separation and recovery of light components and methanol, saving catalyst costs and alkali liquid. The consumption can save about 30% of operating costs.

8. Compared with the traditional stirred tank reactor, the present invention does not require a stirrer, avoiding the safety hazards brought by the stirring device, and the nitric acid conversion rate is increased by about 30%, saving the consumption of nitric acid and alkali liquid, and reducing the subsequent cost. The separation and recovery of light components, methanol, etc. consumes energy and investment while reducing the burden of sewage treatment, which can save about 40% of operating costs.

Description of drawings

Figure 1 shows a common non-catalytic nitric acid recovery reaction system;

Figure 2 shows the non-catalytic deep nitric acid reaction and methanol recovery system of the present invention.

In the figure, 100 - tower body; 1 - primary gas distributor; 2 - primary built-in heater; 3 - secondary liquid distributor; 4 - connecting pipe one; 5 - partition one; 6 - secondary gas distribution 7-First-level liquid distributor; 8-Connecting tube two; 9-Partition plate two; 10-Second-level built-in heater; 11-First-level filler; 12-Second-level filler; 13-Liquid feed distributor; 14-three-stage packing; 15-fourth-stage packing; 16-side collection collector; 17-five-stage packing; 18-sixth-stage packing; 19-reflux liquid distributor; 20-top condenser; 21-top separation Tank; 22-Tower top recovery pump; 23-Side extraction pump; 24-Side extraction cooler; 25-Tower kettle pump; 26-Concentration and separation section; 27-Pre-reaction section; 28-Depth reaction section; 29-Defoaming device.

Detailed ways

The present invention will be further described below with reference to specific embodiments and drawings, but the present invention is not limited thereto.

Example 1

A deep nitric acid reaction and methanol recovery system has a tower structure and includes a concentration and separation section 26, a pre-reaction section 27, and a deep reaction section 28. The interior of the concentration and separation section 26 is provided with a second-level built-in heater 10, a first-level filler 11, a second-level filler 12, a liquid feed distributor 13, a third-level filler 14, a fourth-level filler 15, and side mining in sequence from bottom to top. Collector 16, five-stage packing 17, six-stage packing 18, and reflux liquid distributor 19; the interior of the pre-reaction section 27 is provided with a secondary gas distributor 6 and a primary liquid distributor 7 in sequence from bottom to top; The interior of the deep reaction section 28 is provided with a first-level gas distributor 1, a first-level built-in heater 2, and a second-level liquid distributor 3 in order from bottom to top. The concentration separation section 26 and the pre-reaction section 27 are separated by a partition plate 29, and the liquid enters the upper part of the pre-reaction section 27 from the bottom of the concentration separation section 26 through the communication pipe 28; the pre-reaction section 27 and the deep reaction section 28 are separated by a partition plate Separated by -5, the liquid enters the upper part of the deep reaction section 28 from the bottom of the pre-reaction section 27 through the communication pipe -4.

The top of the concentration and separation section 26 is provided with a gas phase outlet. The outlet gas phase is condensed by the tower top condenser 20 and then enters the tower top separation tank 21. The separated gas phase goes to the downstream system, the liquid phase enters the tower top recovery pump 22, and part of the reflux returns to the concentration and separation section. In the upper part, part of the liquid phase is extracted to the tank area.

The middle and upper part of the concentration and separation section 26 is provided with a side extraction port. The side extraction liquid phase is cooled by the side extraction cooler 24 and then enters the side extraction pump 23. The pump outlet goes to the tank area.

An exhaust port is provided at the top of the pre-reaction section 27 and the deep reaction section 28, and the two exhaust ports are connected to the downstream system through pipelines. A drain outlet is provided at the bottom of the deep reaction section 28, and a tower kettle pump 25 is provided at the drain outlet, which is connected to the downstream system via a pipeline.

The primary gas distributor 1 and the secondary gas distributor 6 are selected from the straight tube baffle type, porous straight tube type, double tangential circulation type, single tangential circulation type, tangential horn type, and double row blade type distributor. A sort of. The primary liquid distributor 7, the secondary liquid distributor 3, the liquid feed distributor 13, and the reflux liquid distributor 19 are selected from the group consisting of nozzle type, disk type, tube type, trough type, and trough disk type distributors. The first-level built-in heater 2 and the second-level built-in heater 10 select one of the tube type, plate type, fin type, bellows type, and spiral groove tube heat exchanger. The demister 29 selects one of wire mesh, swirl plate type and baffle type demister 29.

The working principle of the deep nitric acid reaction and methanol recovery system is: the nitric acid-containing raw material liquid is evenly distributed into the concentration and separation section 26 through the liquid feed distributor 13. The lower part is the stripping section, and the concentration of nitric acid becomes higher as it goes downwards. The upward part of the distributor is the distillation section, and the concentration of light components becomes higher as it goes upward. The secondary built-in heater 10 provided at the bottom of the concentration separation section 26 provides reboiling heat for the section, and the tower top condenser 20 provided at the top provides a cold source for the section top reflux. The light components extracted from the top of the tower are mainly methyl formate, methylal, etc., and methanol is extracted from the side of the tower. The nitric acid content after concentration and separation is about 12%, and enters the pre-reaction section 27 from the bottom of the concentration and separation section 26 through the connecting pipe 8 . It is evenly distributed into the pre-reaction section 27 through the primary liquid distributor 7. The raw material gas containing nitric oxide enters the pre-reaction section 27 through the secondary gas distributor 6. Nitric oxide, nitric acid and methanol are in the pre-reaction section 27. The gas and liquid phases are in counter-current contact and the reaction is thoroughly mixed. The entire system can be controlled by DCS and controlled based on parameters such as liquid level, pressure, flow, temperature, etc. combined with process needs.

The liquid at the bottom of the pre-reaction section 27 is evenly distributed into the deep reaction section 28 through the connecting pipe 14 to the secondary liquid distributor 3. The raw material gas containing nitric oxide enters the deep reaction section 28 through the primary gas distributor 1. The gas-liquid The phases are fully counter-currently contacted and mixed in the deep reaction section of the reactor, and the first-level built-in heater 2 provides the required heat for the reaction. After the reaction, the gas phase passes through the upper gas outlet of the deep reaction section and merges with the top exhaust outlet of the pre-reaction section 27 before going to the downstream system. The reaction liquid passes through the bottom discharge outlet of the reactor to the tower kettle pump 25 and is sent to the downstream system.

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 sections 27 or deep reaction sections 28 can be increased, or the outlet of the tower reactor pump 25 can be increased to return reflux to the pre-reaction section 27 or deep reaction section 28. It can further improve the nitric acid conversion rate. Of course, in order to save investment and pump energy consumption, the external condenser can be changed to a built-in type and installed in the top of the tower. The gas phase outlet of the condenser is connected to the gas phase outlet on the top of the tower, so that gravity reflux can be used, eliminating the need for a tower. Top reflux pump and tower top separation tank.

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 raw material liquid (the tower still liquid of the esterification reaction) is introduced into the concentration and separation section 26 through the liquid feed distributor 13, and the secondary built-in heater 10 is turned on. The raw material liquid is separated into gas and liquid under the action of the packing, and the gas phase at the top of the tower is Gas and light components are produced at the outlet, and methanol is produced at the upper side of the concentration and separation section 26; the gas and light components produced at the top of the tower are condensed and then separated into gas and liquid, and part of the liquid is returned to the concentration and separation section 26;

After the liquid level at the bottom of the concentration and separation section (26) reaches 3 to 6 meters, open the electric valve of the connecting pipe 29, and the secondary gas distributor 6 in the pre-reaction section 27 flows into the NO-containing raw material gas;

After the liquid level at the bottom of the pre-reaction section 27 reaches 2 to 5 meters, the connecting pipe 1 4 and the first-level built-in heater 2 are opened, and the first-level gas distributor 1 in the deep reaction section 28 is introduced into the raw gas containing NO;

During the reaction process, the heating temperature of the secondary built-in heater 10 is controlled to be 40~200°C; the temperature of the pre-reaction section 27 is 20~200°C, the pressure is 0.01~2.0MPaG, and the liquid-gas ratio is 0.1~50 (molar ratio) , 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-gas ratio is 0.1~100 (molar ratio), the residence time is 0.1~100h; the top reflux ratio is 0.1~ 100.

The NO-containing raw material gas is selected from the circulating gas in the ethylene glycol device, and its composition (V%) is: 5~15% NO, CO10~20%, N ₂ 30~45%, CO ₂ 5~10%, MN (sub- Methyl nitrate) 5~10%.

With the continuous supply of raw material liquid and raw material gas and maintaining the liquid levels of the pre-reaction section 27 and the deep reaction section 28, the above three stages are in a continuous state.

Finally, in addition to the recovered methanol, the gas in the upper part of the deep reaction section 28 and the gas in the top 27 of the pre-reaction section merge and go to the downstream system, and the reaction liquid is sent to the downstream system through the bottom discharge outlet and the tower kettle pump 25.

Example 3

This example gives a specific processing situation of the raw material liquid composition in the above system:

The raw material liquid is a 20t/h raw material liquid containing nitric acid, methanol, etc., and its specific composition is as follows:

Component name Methanol water Nitric acid Methyl formate Methyl Dimethyl carbonate Mass fractionw% 60 28 5 4.8 1.2 1

The above-mentioned raw material liquid enters the concentration separation section 26 through the liquid feed distributor 13. The gas-liquid phase in the section is balanced, the light components flow to the upper part of the tower, and the concentration becomes higher and higher, and the heavy components flow to the lower part of the tower, and the concentration becomes higher and higher. After the gas phase at the top of the tower is condensed to 10~40°C by the tower top condenser 20, it is then sent to the top separation tank 21 for separation. The separated gas phase enters the downstream system, and the separated liquid phase is partially refluxed and partially extracted. The reflux ratio is 0.1 ~50, the produced liquid flow rate is 1.9t/h, and the components are as follows:

Component name Methanol Methyl formate Methyl Dimethyl carbonate Mass fractionw% 26.3 50.5 12.6 10.5

A side collection collector 16 is provided in the middle and upper part of the concentration and separation section 26. Methanol is collected from the side collection collector 16 and is cooled to 40°C and then pumped to the tank area. The side collection methanol content is 100% and the production volume is 10t/ h.

The bottom of the concentration and separation section 26 is the nitric acid-containing concentrated liquid after separation of light components and methanol. The flow rate is 8.1t/h, and the specific components are as follows:

Component name Methanol water Nitric acid Mass fractionw% 18.8 68.9 12.3

The concentrated nitric acid liquid enters the pre-reaction section 27 through the connecting pipe 28, and the raw material gas enters the pre-reaction section 27 of the system through the secondary gas distributor 6. The concentrated nitric acid liquid is evenly distributed from the primary liquid distributor 7 to the pre-reaction section 27. The concentrated liquid flows from the upper part to the lower part, and the raw material gas flows from the lower part to the upper part. The gas and liquid phases contact each other in countercurrent in the pre-reaction section 27, and mixing and reaction occur. The reaction temperature of the pre-reaction section 27 is 20~200°C, the pressure is 0.01~2.0MPaG, the liquid-gas ratio is 0.1~50 (molar ratio), the residence time is 0.1~50h, and the nitric acid content in the outlet reaction liquid is 0.1%. The reacted gas is sent to the downstream system from 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 through the connecting pipe 14 to the secondary liquid distributor 3. The raw material gas enters the deep reaction section 28 through the primary gas distributor 1, and the gas-liquid phase reacts in the deep reaction section 28. Full countercurrent contact and mixing reaction are carried out in section 28, and the first-level built-in heater 2 provides the required heat for the reaction. The raw material gas is the circulating gas in the ethylene glycol device. The composition (V%) is: 5~15% NO, CO10~20%, N ₂ 30~45%, CO ₂ 5~10%, MN (methyl nitrite) 5~10%. The reaction temperature of the deep reaction section 28 is 20~200℃, the pressure is 0.01~2.0MPaG, the liquid-gas ratio is 0.1~100 (molar ratio), the residence time is 0.1~100h, the nitric acid content in the outlet reaction liquid is 0.04%; the gas phase after the reaction After the upper gas outlet of the deep reaction section 28 merges with the exhaust outlet at the top of the pre-reaction section 27, it goes to the downstream system. The reaction liquid passes through the bottom drain outlet of the deep reaction section 28 to the tower kettle pump 25, and the pump outlet is sent to the downstream system.

Example 4

Figure 2 is a schematic structural diagram of a deep nitric acid reaction and methanol recovery system of the present invention, including a concentration separation section 26, a pre-reaction section 27, a deep reaction section 28, a side production cooler 24, a side production pump 23, and a tower kettle. Pump 25, tower top condenser 20, tower top separation tank 21, tower top reflux pump 22.

The 20t/h raw material liquid is passed into the concentration and separation section 26. The nitric acid content in the raw material liquid is 5%, and the methanol content is 60%. 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 8t/h, the condensation temperature of the tower top condenser 20 is 20°C, the tower top reflux ratio is 5, the tower top liquid phase flow rate is 1.9t/h, and the side extraction methanol flow rate is 10t/h. At the same time, the raw material gas is passed into the system pre-reaction section 27 and the deep reaction section 28. The raw material gas is selected as the circulating gas in the ethylene glycol device, and the nitric oxide content in the raw gas is 10%. The raw material liquid realizes separation and recovery of light components and methanol in the concentration and separation section 26. At the same time, the nitric acid is concentrated, and the nitric acid concentration is 12.3w%. The concentrated nitric acid liquid enters the pre-reaction section 27 at a flow rate of 8.1t/h. The gas-liquid two-phase contact reaction occurs in the pre-reaction section 27 in a counter-current manner. The reaction temperature of the pre-reaction section 27 is 75°C, the pressure is 0.5MPaG, and the liquid-gas ratio is 11 (molar ratio), the residence time is 0.5h, and the nitric acid content in the outlet reaction solution is 0.1%. After the liquid reacts in the pre-reaction section 27, it flows into the deep reaction section 28 by gravity, and further reacts with the incoming raw material gas in the deep reaction section 28. The reaction temperature in the deep reaction section 28 is 90°C, the pressure is 0.55MPaG, and the feed amount of the raw material gas is It is 15000Nm ³ /h, the steam flow rate of the first-level 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 about 99.72%.

Example 5

Figure 2 is a schematic structural diagram of a deep nitric acid reaction and methanol recovery system of the present invention, including a concentration separation section 26, a pre-reaction section 27, a deep reaction section 28, a side production cooler 24, a side production pump 23, and a tower kettle. Pump 25, tower top condenser 20, tower top separation tank 21, tower top reflux pump 22.

The 20t/h raw material liquid is passed into the concentration and separation section 26. The nitric acid content in the raw material liquid is 2%, and the methanol content is 60%. 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 8t/h, the condensation temperature of the tower top condenser 20 is 20°C, the tower top reflux ratio is 5, the tower top liquid phase flow rate is 1.9t/h, and the side extraction methanol flow rate is 10t/h. At the same time, the raw material gas is passed into the system pre-reaction section 27 and the deep reaction section 28. The raw material gas is selected as the circulating gas in the ethylene glycol device, and the nitric oxide content in the raw gas is 10%. The raw material liquid realizes separation and recovery of light components and methanol in the concentration and separation section 26. At the same time, the nitric acid is concentrated, and the nitric acid concentration is 4.92w%. The concentrated nitric acid liquid enters the pre-reaction section 27 at a flow rate of 8.1t/h, and the gas-liquid two-phase contact reaction is counter-current in the reactor. The reaction temperature of the pre-reaction section 27 is 75°C, the pressure is 0.5MPaG, and the liquid-gas ratio is 11 (mol ratio), the residence time is 0.5h, and the nitric acid content in the outlet reaction solution is 0.1%. After the liquid reacts in the pre-reaction section 27, it flows into the deep reaction section 28 by gravity, and further reacts with the incoming raw material gas in the deep reaction section 28. The reaction temperature of the deep reaction section 28 is 90°C, the pressure is 0.55MPaG, and the raw material gas feed amount is 15000Nm. ³ /h, 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 about 99.4%.

Example 6

Figure 2 is a schematic structural diagram of a deep nitric acid reaction and methanol recovery system of the present invention, including a concentration separation section 26, a pre-reaction section 27, a deep reaction section 28, a side production cooler 24, a side production pump 23, and a tower kettle. Pump 25, tower top condenser 20, tower top separation tank 21, tower top reflux pump 22.

Pass the 20t/h raw material liquid into the concentration and separation section 26. The nitric acid content in the raw material liquid is 3%, and the methanol content is 60%. 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 8t/h, the condensation temperature of the tower top condenser 20 is 20°C, the tower top reflux ratio is 5, the tower top liquid phase flow rate is 1.9t/h, and the side extraction methanol flow rate is 10t/h. At the same time, the raw material gas is passed into the system pre-reaction section 27 and the deep reaction section 28. The raw material gas is selected as the circulating gas in the ethylene glycol device, and the nitric oxide content in the raw gas is 10%. The raw material liquid realizes separation and recovery of light components and methanol in the concentration and separation section 26. At the same time, the nitric acid is concentrated, and the nitric acid concentration is 7.38w%. The flow rate of the nitric acid concentrate is 8.1t/h and enters the pre-reaction section 27. The gas-liquid two-phase contact reaction is counter-current in the system. The reaction temperature of the pre-reaction section 27 is 75°C, the pressure is 0.5MPaG, and the liquid-gas ratio is 11 (molar ratio) , the residence time is 0.5h, and the nitric acid content in the outlet reaction solution is 0.1%. After the liquid reacts in the pre-reaction section 27, it flows into the deep reaction section 28 by gravity, and further reacts with the incoming raw material gas in the deep reaction section 28. The reaction temperature of the deep reaction section 28 is 90°C, the pressure is 0.55MPaG, and the raw material gas feed amount is 15000Nm. ³ /h, the steam flow rate of the first-level 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 about 99.5%.

Comparative example 1

As shown in the prior art system shown in Figure 1, 20t/h raw material liquid is passed into the stirred tank reactor. The nitric acid content in the raw material liquid is 5% and the methanol content is 60%. At the same time, the raw material gas is passed into the parallel stirred tank reactor. In the device, the raw material gas is the circulating gas in the ethylene glycol device. The nitric oxide content in the raw gas is 10%. The nitric acid reduction reaction occurs under the stirring action of the stirrer. The reaction temperature is 80°C, the pressure is 0.45MPaG, and the raw gas feed amount 20000Nm ³ /h, the circulation pump flow rate is 600m³/h, the nitric acid content in the reaction liquid at the outlet of the reactor is 1.75%, and the nitric acid conversion rate is about 65%.

Comparative example 2

As shown in the prior art system shown in Figure 1, 20t/h raw material liquid is passed into the stirred tank reactor. The nitric acid content in the raw material liquid is 2% and the methanol content is 60%. At the same time, the raw material gas is passed into the parallel stirred tank reactor. In the device, the raw material gas is the circulating gas in the ethylene glycol device. The nitric oxide content in the raw gas is 10%. The nitric acid reduction reaction occurs under the stirring action of the stirrer. The reaction temperature is 80°C, the pressure is 0.45MPaG, and the raw gas feed amount 20000Nm ³ /h, the circulation pump flow rate is 600m³/h, the nitric acid content in the reaction liquid at the outlet of the reactor is 0.8%, and the nitric acid conversion rate is about 60%.

Comparative example 3

As shown in the prior art system shown in Figure 1, 20t/h raw material liquid is passed into the stirred tank reactor. The nitric acid content in the raw material liquid is 3% and the methanol content is 60%. At the same time, the raw material gas is passed into the parallel stirred tank reactor. In the device, the raw material gas is the circulating gas in the ethylene glycol device. The nitric oxide content in the raw gas is 10%. The nitric acid reduction reaction occurs under the stirring action of the stirrer. The reaction temperature is 80°C, the pressure is 0.45MPaG, and the raw gas feed amount 20000Nm ³ /h, the circulation pump flow rate is 600m³/h, the nitric acid content in the reaction liquid at the outlet of the reactor is 1.14%, and the nitric acid conversion rate is about 62%.

It should be noted that according to actual needs, the number of stages in the pre-reaction section 27 or the deep reaction section 28 can be increased, and the reflux pipeline of the tower tank pump 25 can be added to the pre-reaction section 27 or the deep reaction section 28 to further improve the nitric acid conversion rate. The number and parameters of the packing layers in the concentration and separation section 26 can be arranged and adjusted as needed.

As an alternative, the tower top condenser 20 can also be a built-in condenser, and the pipeline can be adjusted accordingly.

The above description is intended to be illustrative rather than restrictive, and those of ordinary skill in the art may make changes, modifications, substitutions and variations to the above-described embodiments within the scope of the present disclosure. Furthermore, the above examples (or one or more versions thereof) may be used in combination with each other, and it is contemplated that these embodiments may be combined with each other in various combinations or permutations.

Claims (10)

1. The non-catalytic nitric acid reaction and methanol recovery system is characterized by comprising a tower body (100), wherein the tower body comprises a concentration separation section (26), a pre-reaction section (27) and a deep reaction section (28) from top to bottom;

the concentration separation section (26) is separated from the pre-reaction section (27) by a second partition board (9), and two sides of the second partition board (9) are communicated by a second communicating pipe (8);

the pre-reaction section (27) and the deep reaction section (28) are separated by a first partition board (5), and two sides of the first partition board (5) are communicated by a first communicating pipe (4);

a liquid feeding distributor (13) is arranged in the concentration and separation section (26) so as to be connected with external nitric acid-containing raw material liquid, a secondary built-in heater (10) is arranged below the liquid feeding distributor (13), and a filler is arranged above the secondary built-in heater (10); the top of the concentration separation section (26) is provided with a gas phase outlet, and the middle upper part of the concentration separation section (26) is provided with a side-extraction collector (16) for connecting a methanol side-extraction port;

the top of the pre-reaction section (27) and the top of the deep reaction section (28) are respectively provided with an exhaust port, the middle lower parts of the pre-reaction section (27) and the deep reaction section (28) are respectively connected with external raw material gas, and the bottom of the deep reaction section (28) is provided with a liquid discharge outlet.

2. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, wherein a packing is arranged between the liquid feed distributor (13) and the secondary built-in heater (10) and between the liquid feed distributor (13) and the tower top, and a packing is arranged between the side recovery collector (16) and the tower top;

preferably, a primary filler (11) and a secondary filler (12) are accumulated between the liquid feed distributor (13) and the secondary built-in heater (10), a tertiary filler (14) and a quaternary filler (15) are accumulated between the liquid feed distributor (13) and the tower top, and a five-stage filler (17) and a six-stage filler (18) are accumulated between the side collecting collector (16) and the tower top.

3. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, wherein the middle lower part of the pre-reaction section (27) and the middle lower part of the deep reaction section (28) are respectively provided with a secondary gas distributor (6) and a primary gas distributor (1) for connecting with external raw material gas;

preferably, a first-stage liquid distributor (7) is arranged at the upper part of the pre-reaction section (27), and a feed inlet of the first-stage liquid distributor (7) is connected with a discharge outlet of a second communicating pipe (8);

preferably, the upper part of the deep reaction section (28) is provided with a secondary liquid distributor (3), and a feed inlet of the secondary liquid distributor (3) is connected with a discharge outlet of the first communicating pipe (4);

preferably, the two exhaust ports are joined by a line and connected to a downstream system.

4. The non-catalytic nitric acid reaction and methanol recovery system according to claim 3, wherein the primary gas distributor (1) and the secondary gas distributor (6) are selected from one of straight pipe baffle plates, porous straight pipes, double tangential circulation, single tangential circulation, tangential horn type and double-row vane type distributors;

preferably, the primary liquid distributor (7) and the secondary liquid distributor (3) are one of a nozzle type, a disk type, a pipe type, a groove type and a groove disk type distributor.

5. A non-catalytic nitric acid reaction and methanol recovery system according to claim 3, wherein a primary built-in heater (2) is arranged in the deep reaction section (28);

preferably, the primary built-in heater (2) is arranged between the primary gas distributor (1) and the secondary liquid distributor (3).

6. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1 or 2, wherein a condenser is arranged in the tower top, and a gas phase outlet of the condenser is communicated with a gas phase outlet of the tower top;

or the gas phase outlet of the tower top is externally connected with a tower top condenser (20), the material outlet of the tower top condenser (20) is connected with a tower top separating tank (21), the gas phase outlet of the tower top separating tank (21) is connected with a downstream system, the liquid phase outlet is connected with a tower top recovery pump (22), one path of the discharge port of the tower top recovery pump (22) is connected with a concentration and separation section (26), and the other path of the discharge port of the tower top recovery pump is connected with a tank area;

preferably, a foam remover (29) is arranged in the tower top separation tank (21);

more preferably, the demister (29) is one of a wire mesh type, a cyclone plate type and a baffle plate type demister.

7. The non-catalytic nitric acid reaction and methanol recovery system according to claim 6, wherein a liquid outlet at the bottom of the deep reaction section (28) is connected with a tower kettle pump (25), and the tower kettle pump (25) is connected with a reflux pipeline and is communicated with the pre-reaction section or the deep reaction section;

preferably, one path of the discharge port of the tower top recovery pump (22) is connected to the upper part of the concentration and separation section (26) and is connected with a reflux liquid distributor (19) above the packing in the concentration and separation section (26);

preferably, the reflux liquid distributor (19) is one of a nozzle type, a disk type, a pipe type, a groove type and a groove disk type distributor.

8. The non-catalytic nitric acid reaction and methanol recovery system according to claim 1, wherein the methanol side extraction port is externally connected with a side extraction cooler (24), a discharge port of the side extraction cooler (24) is connected with a side extraction pump (23), and an outlet of the side extraction pump (23) is connected with a tank area and a liquid feed distributor (13);

preferably, the liquid feeding distributor (13) is one of a nozzle type, a disk type, a tubular type, a groove type and a groove disk type distributor.

9. A process for deep nitric acid reaction and methanol recovery, wherein the process is operated in a system as claimed in any one of claims 1 to 8 above:

introducing nitric acid-containing raw material liquid into a concentration and separation section (26) through a liquid feed distributor (13), starting a secondary built-in heater (10), extracting gas and light components at a gas phase outlet at the top of the tower, and extracting methanol at an upper side extraction port in the concentration and separation section (26);

after the liquid level at the bottom of the concentration and separation section (26) reaches a certain value, opening an electric valve of a communicating pipe II (8), and introducing feed gas into a secondary gas distributor (6) in the pre-reaction section (27);

after the pre-reaction section (27) reacts for a period of time, a first communicating pipe (4) and a first-stage built-in heater (2) are opened, and a first-stage gas distributor (1) in the deep reaction section (28) is filled with feed gas;

after the reaction is finished, the gas at the upper part of the deep reaction section (28) and the gas at the top of the pre-reaction section (27) are converged and sent to a downstream system, and the reaction liquid is sent to the downstream system through a liquid outlet at the bottom of the tower.

10. The method for deep nitric acid reaction and methanol recovery according to claim 9, further comprising the step of separating the overhead gas and the light components by gas-liquid separation, and returning part of the liquid to the concentration separation section (26);

preferably, the heating temperature of the secondary built-in heater (10) is 40-200 ℃;

opening a second (8) electric valve of a communicating pipe when the liquid level at the bottom of the concentration and separation section (26) reaches 3-6 m, wherein the temperature of the pre-reaction section (27) is 20-200 ℃, the pressure is 0.01-2.0 MPaG, the liquid-gas ratio is 0.1-50 (molar ratio), and the residence time is 0.1-50 h;

when the liquid level at the bottom of the pre-reaction section (27) reaches 2-5 m, a first communicating pipe (4) and a first-stage built-in heater (2) are started, the temperature of the deep reaction section (28) is 20-200 ℃, the pressure is 0.01-2.0 MPaG, the liquid-gas ratio is 0.1-100 (molar ratio), and the residence time is 0.1-100 h;

the reflux ratio of the tower top is 0.1-100.