System and method for optimizing nitric acid reduction process in dimethyl oxalate synthesis device

Abstract

The invention discloses a system and a method for optimizing a nitric acid reduction process in a dimethyl oxalate synthesis device, which are characterized in that through process and pipeline improvement, part of byproduct steam which is generated by a steam drum and is originally conveyed to an air cooler for condensation treatment is conveyed to a second-chamber tower kettle, a third-chamber tower kettle and a fourth-chamber tower kettle of a nitric acid reduction tower through a byproduct steam recycling pipeline; the heating device is used for heating the second-chamber tower kettle, the third-chamber tower kettle and the fourth-chamber tower kettle so as to recycle the byproduct steam. The low-grade byproduct steam heat energy without air cooling is used for replacing the original 0.5 MPaG steam used for heating the second-chamber tower kettle, the third-chamber tower kettle and the fourth-chamber tower kettle of the nitric acid reduction tower, and meanwhile, part of steam pocket air coolers which are running in the dimethyl oxalate synthesis device can be shut down, so that the heat can be recovered, the power consumption can be reduced, and the heat energy utilization efficiency can be improved.

Description

Technical Field

[0001] The embodiment of the present invention relates to the technical field of nitric acid reduction process optimization in a dimethyl oxalate synthesis device, and specifically to a nitric acid reduction process optimization system and method in a dimethyl oxalate synthesis device. Background Art

[0002] There are 9 sets of dimethyl oxalate (DMO) synthesis units, and the overall reaction is: 2CO+2MN→DMO+2NO. Each set of DMO synthesis unit includes 2 DMO reactors (reactor A and reactor B), 2 steam drums (steam drum A and steam drum B), and 2 nitric acid reduction towers (nitric acid reduction tower A and nitric acid reduction tower B). The nitric acid reduction tower is a vertical structure, with one, two, three, and four chambers from top to bottom. The material flows in from chamber one, passes through chambers two, three, and four in turn, and finally flows out from the fourth chamber tower kettle. Its function is to produce MN, one of the reaction raw materials. The function of the steam drum is to remove the heat generated by the DMO reactor. The steam in chamber one can come from the by-product steam generated by steam drum B, and the steam in chambers two, three, and four comes from independent 0.5MPaG steam. At the same time, part of the by-product steam generated by steam drums A and B needs to be sent to the steam drum air cooler for condensation treatment. Low-grade by-product steam needs to be condensed using an air cooler, which has technical disadvantages such as high power consumption, high maintenance costs, cumbersome operation, and low thermal energy utilization, and fails to achieve effective recovery and utilization of the thermal energy of this by-product steam. Summary of the invention

[0003] To this end, the present invention provides a nitric acid reduction process optimization system and method in a dimethyl oxalate synthesis device, so as to solve the technical problems that the existing dimethyl oxalate synthesis device fails to realize the effective recovery and utilization of the by-product steam heat energy, has the problems of large power consumption of air cooler operation, high maintenance cost, cumbersome operation, low heat energy utilization rate, etc.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] According to a first aspect of the present invention, the present invention provides a nitric acid reduction process optimization system in a dimethyl oxalate synthesis device, the system comprising a nitric acid reduction tower, a steam drum, and a by-product steam recovery pipeline;

[0006] The steam drum is used to remove the heat generated by the dimethyl oxalate synthesis reactor; the nitric acid reduction tower includes a first chamber, a second chamber, a third chamber and a fourth chamber tower kettle arranged in sequence from top to bottom, and the material flows in from the first chamber tower kettle, passes through the second, third and fourth chamber tower kettles in sequence, and finally flows out from the fourth chamber tower kettle;

[0007] The steam reserved port of the first-chamber kettle of the nitric acid reduction tower is connected to the by-product steam outlet of the steam drum through a steam pipeline, so as to use a part of the by-product steam generated by the steam drum to heat the first-chamber kettle of the nitric acid reduction tower; the steam reserved ports of the second-chamber, third-chamber and fourth-chamber kettles of the nitric acid reduction tower are all connected to the by-product steam outlet of the steam drum through a by-product steam recovery pipeline, so as to use another part of the by-product steam generated by the steam drum to heat the second-chamber, third-chamber and fourth-chamber kettles to achieve the recovery and utilization of the by-product steam.

[0008] Further, the system includes nitric acid reduction tower A and nitric acid reduction tower B, steam drum A and steam drum B;

[0009] The byproduct steam outlet of the drum A is connected to the drum preheater through a first steam pipeline, and the byproduct steam outlet of the drum A is connected to the first air cooler through a second steam pipeline;

[0010] The byproduct steam outlet of the drum B is connected to the steam reserved port of the one-chamber tower kettle of the nitric acid reduction tower A and B through the third steam pipeline, and the byproduct steam outlet of the drum B is connected to the second air cooler through the fourth steam pipeline;

[0011] One end of the by-product steam recovery pipeline is connected to the second steam pipeline or the fourth steam pipeline, and the other end is connected to the steam reserved port of the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B. When part of the by-product steam generated by steam drum A or B that is originally to be transported to the air cooler is transported to the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B through the by-product steam recovery pipeline, the first air cooler or the second air cooler is shut down accordingly.

[0012] Furthermore, the steam reserved ports of the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B are all connected to the heating steam pipeline for heating steam supply. When part of the by-product steam generated by the steam drum A or B that is originally to be transported to the air cooler is transported to the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, the heating steam pipeline is shut down.

[0013] Furthermore, the heating steam pipeline is a 0.5MPaG steam pipeline.

[0014] Furthermore, the steam condensate outlet of each chamber of the nitric acid reduction towers A and B is connected to the steam condensate buffer tank through a pipeline.

[0015] According to a second aspect of the present invention, the present invention provides a method for optimizing a nitric acid reduction process in a dimethyl oxalate synthesis device, characterized in that the method comprises:

[0016] A part of the by-product steam generated by the steam drum is used to heat the first chamber kettle of the nitric acid reduction tower, and another part of the by-product steam generated by the steam drum is transported to the second chamber, third chamber and fourth chamber kettles of the nitric acid reduction tower through a by-product steam recovery pipeline to heat the second chamber, third chamber and fourth chamber kettles to realize the recovery of the by-product steam, wherein the steam drum is used to remove the heat generated by the dimethyl oxalate synthesis reactor, and the nitric acid reduction tower comprises the first chamber, the second chamber, the third chamber and the fourth chamber kettles which are arranged in sequence from top to bottom, and the material flows in from the first chamber kettle, passes through the second, third and fourth chamber kettles in sequence, and finally flows out from the fourth chamber kettle.

[0017] Furthermore, the method specifically comprises:

[0018] If the nitric acid reduction tower includes nitric acid reduction towers A and B, and the steam drum includes steam drums A and B, a portion of the by-product steam generated by steam drum B is used to heat the first-chamber kettle of nitric acid reduction towers A and B, and another portion of the by-product steam generated by steam drum A or B is transported to the second-chamber, third-chamber and fourth-chamber kettles of nitric acid reduction towers A and B through a by-product steam recovery pipeline for heating the second-chamber, third-chamber and fourth-chamber kettles.

[0019] Furthermore, the method specifically comprises:

[0020] Part of the by-product steam generated by the steam drum A or B, which is originally to be transported to the first air cooler or the second air cooler for condensation treatment, is transported to the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, and the first air cooler connected to the steam drum A or the second air cooler connected to the steam drum B is shut down accordingly.

[0021] Furthermore, the method specifically comprises:

[0022] Part of the by-product steam generated by the steam drum A or B, which was originally to be transported to the first air cooler or the second air cooler for condensation treatment, is transported to the second, third and fourth chamber kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, and the heating steam pipeline originally used for supplying heating steam to the second, third and fourth chamber kettles of the nitric acid reduction towers A and B is shut down.

[0023] Furthermore, the method specifically comprises:

[0024] The steam condensate from each chamber of the nitric acid reduction tower is transported to the steam condensate buffer tank through pipelines for storage.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention proposes a nitric acid reduction process optimization system and method in a dimethyl oxalate synthesis device. Through process and pipeline improvements, part of the by-product steam generated by the drum that is originally to be transported to an air cooler for condensation treatment is then transported to the second chamber, third chamber and fourth chamber tower kettles of the nitric acid reduction tower through a by-product steam recovery pipeline, so as to heat the second chamber, third chamber and fourth chamber tower kettles to achieve the recycling of the by-product steam. By using the heat energy of the low-grade by-product steam that has been air-cooled to replace the original 0.5MPaG steam used to heat the second chamber, third chamber and fourth chamber tower kettles of the nitric acid reduction tower, and at the same time allowing part of the drum air coolers that are in operation in the dimethyl oxalate synthesis device to be shut down, it is possible to recover heat, reduce power consumption, and improve thermal energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 A schematic structural diagram of a nitric acid reduction process optimization system in a dimethyl oxalate synthesis device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0030] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0031] Example 1

[0032] In Example 1 of the present invention, a nitric acid reduction process optimization system in a dimethyl oxalate synthesis device is proposed, and the system includes a nitric acid reduction tower, a steam drum, and a by-product steam recovery pipeline.

[0033] The steam drum is used to remove the heat generated by the dimethyl oxalate synthesis reactor; the nitric acid reduction tower comprises a first-chamber, a second-chamber, a third-chamber and a fourth-chamber tower kettle which are arranged in sequence from top to bottom, and the material flows in from the first-chamber tower kettle, passes through the second, third and fourth-chamber tower kettles in sequence, and finally flows out from the fourth-chamber tower kettle; wherein the steam reserved port of the first-chamber tower kettle of the nitric acid reduction tower is connected to the by-product steam outlet of the steam drum through a steam pipeline, so as to use part of the by-product steam generated by the steam drum to heat the first-chamber tower kettle of the nitric acid reduction tower; the steam reserved ports of the second-chamber, third-chamber and fourth-chamber tower kettles of the nitric acid reduction tower are all connected to the by-product steam outlet of the steam drum through a by-product steam recovery pipeline, so as to use part of the by-product steam generated by the steam drum to heat the second-chamber, third-chamber and fourth-chamber tower kettles to achieve the recycling of the by-product steam.

[0034] The existing dimethyl oxalate (DMO) synthesis unit has a total of 9 DMO synthesis units, and the overall reaction is: 2CO+2MN→DMO+2NO. Each DMO synthesis unit includes 2 DMO reactors (reactor A and reactor B), 2 steam drums (steam drum A and steam drum B), and 2 nitric acid reduction towers (nitric acid reduction tower A and nitric acid reduction tower B). Part of the by-product steam generated by steam drum A is used to heat the steam drum preheater, and the other part is sent to the steam drum air cooler for condensation treatment; part of the by-product steam generated by steam drum B is used to heat the nitric acid reduction tower A and the nitric acid reduction tower B, and the other part is also sent to the steam drum air cooler for condensation treatment. Specifically:

[0035] 1. The first chamber is heated by the by-product steam produced by the dimethyl oxalate (DMO) synthesis drum B, consuming 0.7 tons of steam per hour and maintaining the operating temperature at 54.85°C;

[0036] 2. The 0.5MPaG steam used in the second chamber is 0.6t / h, the maximum is 0.65t / h, the operating temperature is 71℃, and the maximum design flow rate is 0.8t / h;

[0037] 3. The 0.5MPaG steam used in the three-chamber operation is 0.6t / h, the maximum is 0.75t / h, the operating temperature is 78℃ and the maximum design flow rate is 1.7 / h;

[0038] 4. The 0.5MPaG steam used in the four-chamber operation is 0.5t / h, with a maximum value of 0.65t / h. The operating temperature is 85℃ and the maximum design flow rate is 0.75 / h.

[0039] The operating conditions of rooms 2, 3 and 4 use a total of 1.7t / h of 0.5MPaG steam, with a maximum of 2.05t / h. All steam condensate will be sent to the steam condensate tank, and then pressurized by a pump and sent to the 0.5MPaG steam condensate pipeline network for reuse.

[0040] The hot water feed rate of the dimethyl oxalate synthesis drum B is designed to be about 13 tons per hour. The by-product steam produced by drum B has a pressure of 60kPaG and a temperature of 115°C. Part of this by-product steam is used to heat one chamber of the nitric acid reduction tower, while the other part is sent to the drum air cooler for condensation.

[0041] The nitric acid reduction process optimization system of this embodiment is as follows: Figure 1 As shown, the specific composition is as follows:

[0042] The byproduct steam outlet of drum A is connected to the drum preheater through a first steam pipeline, and the byproduct steam outlet of drum A is connected to the first air cooler through a second steam pipeline;

[0043] The by-product steam outlet of drum B is connected to the steam reserved port of the one-chamber tower kettle of nitric acid reduction tower A and B through the third steam pipeline, and the by-product steam outlet of drum B is connected to the second air cooler through the fourth steam pipeline;

[0044] One end of the by-product steam recovery pipeline is connected to the second steam pipeline or the fourth steam pipeline, and the other end is connected to the steam reserved port of the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B. When part of the by-product steam generated by steam drum A or B that is originally to be transported to the air cooler is transported to the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B through the by-product steam recovery pipeline, the corresponding first air cooler or second air cooler is shut down.

[0045] In this embodiment, the steam reserved ports of the second, third and fourth chambers of the nitric acid reduction towers A and B are all connected to the heating steam pipeline for heating steam supply, and when part of the by-product steam generated by the steam drum A or B that is originally to be transported to the air cooler is transported to the second, third and fourth chambers of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, the heating steam pipeline is shut down. In this embodiment, the heating steam pipeline is a 0.5MPaG steam pipeline.

[0046] In this embodiment, the steam condensate outlet of each chamber of the nitric acid reduction towers A and B is connected to the steam condensate buffer tank through a pipeline.

[0047] The nitric acid reduction tower has coil heating, and the heat exchange area is fixed. The use of 60Kpa(G) steam requires an increase in steam consumption. Through heat calculation, the use of 60Kpa(G) steam to replace 0.5MPaG steam requires 4% more steam consumption. The maximum flow of the above-mentioned 234 chambers meets the design maximum flow.

[0048] The nitric acid reduction steam cut-off valve and regulating valve have a large resistance drop and are both equipped with SIS interlock protection. The present invention utilizes the heat energy of low-grade by-product steam that has been air-cooled to replace 0.5MPaG steam, thereby saving 0.5MPaG steam energy while shutting down the drum air cooler and recovering 60KPaG low-grade steam heat energy from the dimethyl oxalate synthesis unit.

[0049] Test example: A chemical glycol plant produces 1.8 million tons of glycol per year. With this scheme, the byproduct steam of the synthesis drum B of a single set of dimethyl oxalate unit can replace the second, third and fourth chambers of the nitric acid reduction tower. The byproduct steam of the drum can be recycled to the air cooler steam, which can save 0.5MPaG steam income: steam income 1.7×8000×81=1.1 million yuan / year, the rated power of the air cooler is 37KW, and the comprehensive electricity saving cost is calculated according to the system 20% load, which can save electricity: electricity income 37×8000×20%×0.61=36,000 yuan / year In summary, the total income of this technical transformation is 1.136 million yuan / year. The remaining 17 nitric acid reduction towers can implement this technical transformation. Charging standard: 1. Steam 0.5MPaG (G): 81 yuan / ton; 2. Electricity price: 0.61 yuan / kWh.

[0050] The present invention improves the process and pipelines, and then transports part of the by-product steam generated by the steam drum, which is originally to be transported to the air cooler for condensation treatment, to the second, third and fourth chambers of the nitric acid reduction tower through the by-product steam recovery pipeline for heating the second, third and fourth chambers of the tower to achieve the recycling of the by-product steam. By using the heat energy of the air-cooled low-grade by-product steam to replace the original 0.5MPaG steam used to heat the second, third and fourth chambers of the nitric acid reduction tower, part of the steam drum air coolers in operation in the dimethyl oxalate synthesis unit can be shut down, and the 60KPaG low-grade by-product steam heat energy of the dimethyl oxalate synthesis unit can be recycled. The specific innovations are as follows:

[0051] 1. The heat of condensate is recovered by material heat exchange, and the condensate temperature can be lowered and all the heat can be recovered, which is better than the ORC and condensate refrigeration technology on the market; this solution has low investment cost and high return on investment;

[0052] 2. After the implementation of this technology, the number of air coolers in operation can be reduced, which not only realizes heat recovery but also reduces power consumption;

[0053] 3. After the implementation of this technology, low-grade steam can be used nearby, reducing heat loss and resistance loss during low-grade transportation. This is a pioneering technology in the ethylene glycol industry.

[0054] Example 2

[0055] Based on a nitric acid reduction process optimization system in a dimethyl oxalate synthesis device provided in Example 1, Example 2 of the present invention provides a process optimization method for a nitric acid reduction process optimization system in a dimethyl oxalate synthesis device, the method comprising: heating a first-chamber kettle of a nitric acid reduction tower with part of the by-product steam generated by a steam drum, and transporting part of the by-product steam generated by the steam drum to the second-chamber, third-chamber and fourth-chamber kettles of the nitric acid reduction tower through a by-product steam recovery pipeline for heating the second-chamber, third-chamber and fourth-chamber kettles to achieve recycling of the by-product steam.

[0056] In this embodiment, the method specifically includes: the first-chamber kettles of nitric acid reduction towers A and B are heated by using part of the by-product steam generated by drum B, and part of the by-product steam generated by drum A or B is then transported to the second-chamber, third-chamber and fourth-chamber kettles of nitric acid reduction towers A and B through a by-product steam recovery pipeline for heating the second-chamber, third-chamber and fourth-chamber kettles.

[0057] In this embodiment, the method specifically includes: when part of the by-product steam generated by the steam drum A or B that is originally to be transported to the first air cooler or the second air cooler for condensation treatment is transported to the second chamber, third chamber and fourth chamber tower bottoms of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, the first air cooler connected to the steam drum A or the second air cooler connected to the steam drum B is shut down accordingly.

[0058] In this embodiment, the method specifically includes: transporting part of the by-product steam generated by the steam drum A or B that was originally to be transported to the first air cooler or the second air cooler for condensation treatment to the second chamber, third chamber and fourth chamber tower kettles of the nitric acid reduction towers A and B through a recycling pipeline, and shutting down the original heating steam pipeline used for supplying heating steam to the second chamber, third chamber and fourth chamber tower kettles of the nitric acid reduction towers A and B.

[0059] In this embodiment, the method specifically includes: transporting the steam condensate in each chamber of the nitric acid reduction tower to a steam condensate buffer tank through a pipeline for storage.

[0060] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A nitric acid reduction process optimization system in a dimethyl oxalate synthesis unit, It is characterized in that The system comprises a nitric acid reduction tower, a steam drum and a by-product steam recovery pipeline; The steam drum is used to remove the heat generated by the dimethyl oxalate synthesis reactor; the nitric acid reduction tower includes a first chamber, a second chamber, a third chamber and a fourth chamber tower kettle arranged in sequence from top to bottom, and the material flows in from the first chamber tower kettle, passes through the second, third and fourth chamber tower kettles in sequence, and finally flows out from the fourth chamber tower kettle; The steam reserved port of the first-chamber kettle of the nitric acid reduction tower is connected to the by-product steam outlet of the steam drum through a steam pipeline, so as to use a part of the by-product steam generated by the steam drum to heat the first-chamber kettle of the nitric acid reduction tower; the steam reserved ports of the second-chamber, third-chamber and fourth-chamber kettles of the nitric acid reduction tower are all connected to the by-product steam outlet of the steam drum through a by-product steam recovery pipeline, so as to use another part of the by-product steam generated by the steam drum to heat the second-chamber, third-chamber and fourth-chamber kettles to achieve the recovery and utilization of the by-product steam.

2. The nitric acid reduction process optimization system in a dimethyl oxalate synthesis device according to claim 1, It is characterized in that The system comprises nitric acid reduction tower A and nitric acid reduction tower B, steam drum A and steam drum B; The byproduct steam outlet of the drum A is connected to the drum preheater through a first steam pipeline, and the byproduct steam outlet of the drum A is connected to the first air cooler through a second steam pipeline; The byproduct steam outlet of the drum B is connected to the steam reserved port of the one-chamber tower kettle of the nitric acid reduction tower A and B through the third steam pipeline, and the byproduct steam outlet of the drum B is connected to the second air cooler through the fourth steam pipeline; One end of the by-product steam recovery pipeline is connected to the second steam pipeline or the fourth steam pipeline, and the other end is connected to the steam reserved port of the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B. When part of the by-product steam generated by steam drum A or B that is originally to be transported to the air cooler is transported to the second chamber, third chamber and fourth chamber tower kettle of nitric acid reduction tower A and B through the by-product steam recovery pipeline, the first air cooler or the second air cooler is shut down accordingly.

3. The nitric acid reduction process optimization system in a dimethyl oxalate synthesis device according to claim 2, It is characterized in that The steam reserved ports of the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B are all connected to the heating steam pipeline for heating steam supply. When part of the by-product steam generated by the steam drum A or B that was originally to be transported to the air cooler is transported to the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, the heating steam pipeline is shut down.

4. The nitric acid reduction process optimization system in a dimethyl oxalate synthesis device according to claim 3, It is characterized in that The heating steam pipeline is a 0.5MPaG steam pipeline.

5. The nitric acid reduction process optimization system in a dimethyl oxalate synthesis device according to claim 2, It is characterized in that The steam condensate outlet of each chamber of the nitric acid reduction towers A and B is connected to the steam condensate buffer tank through a pipeline.

6. A method for optimizing the nitric acid reduction process in a dimethyl oxalate synthesis device, It is characterized in that The method comprises: A part of the by-product steam generated by the steam drum is used to heat the first chamber kettle of the nitric acid reduction tower, and another part of the by-product steam generated by the steam drum is transported to the second chamber, third chamber and fourth chamber kettles of the nitric acid reduction tower through a by-product steam recovery pipeline to heat the second chamber, third chamber and fourth chamber kettles to realize the recovery of the by-product steam, wherein the steam drum is used to remove the heat generated by the dimethyl oxalate synthesis reactor, and the nitric acid reduction tower comprises the first chamber, the second chamber, the third chamber and the fourth chamber kettles which are arranged in sequence from top to bottom, and the material flows in from the first chamber kettle, passes through the second, third and fourth chamber kettles in sequence, and finally flows out from the fourth chamber kettle.

7. The method for optimizing the nitric acid reduction process in a dimethyl oxalate synthesis device according to claim 6, It is characterized in that The method specifically comprises: If the nitric acid reduction tower includes nitric acid reduction towers A and B, and the steam drum includes steam drums A and B, a portion of the by-product steam generated by steam drum B is used to heat the first-chamber kettle of nitric acid reduction towers A and B, and another portion of the by-product steam generated by steam drum A or B is transported to the second-chamber, third-chamber and fourth-chamber kettles of nitric acid reduction towers A and B through a by-product steam recovery pipeline for heating the second-chamber, third-chamber and fourth-chamber kettles.

8. The method for optimizing the nitric acid reduction process in a dimethyl oxalate synthesis device according to claim 7, It is characterized in that The method specifically comprises: Part of the by-product steam generated by the steam drum A or B, which is originally to be transported to the first air cooler or the second air cooler for condensation treatment, is transported to the second, third and fourth chamber tower kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, and the first air cooler connected to the steam drum A or the second air cooler connected to the steam drum B is shut down accordingly.

9. The method for optimizing the nitric acid reduction process in a dimethyl oxalate synthesis device according to claim 7, It is characterized in that The method specifically comprises: Part of the by-product steam generated by the steam drum A or B, which was originally to be transported to the first air cooler or the second air cooler for condensation treatment, is transported to the second, third and fourth chamber kettles of the nitric acid reduction towers A and B through the by-product steam recovery pipeline, and the heating steam pipeline originally used for supplying heating steam to the second, third and fourth chamber kettles of the nitric acid reduction towers A and B is shut down.

10. The method for optimizing the nitric acid reduction process in a dimethyl oxalate synthesis device according to claim 7, It is characterized in that The method specifically comprises: The steam condensate from each chamber of the nitric acid reduction tower is transported to the steam condensate buffer tank through pipelines for storage.

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