A resource recovery system in the ethylene glycol esterification process

Abstract

This invention proposes a resource recovery system for the ethylene glycol esterification process. The outlet of the bottom liquid of the nitric acid reduction reaction tower is connected to the middle inlet of the methanol recovery tower via a pipeline. The outlet of the bottom liquid of the methanol recovery tower is connected to the inlet of the methanol recovery tower bottom pump via a pipeline. The outlet of the methanol recovery tower bottom pump is connected to the middle inlet of the nitric acid reduction reaction tower via a pipeline. The outlet of the bottom liquid of the nitric acid reduction reaction tower is also connected to the inlet of the nitric acid tower reflux pump via a pipeline. The outlet of the nitric acid tower reflux pump is connected to the inlet of the reaction tower preheater via a pipeline. The outlet of the reaction tower preheater is connected to the upper inlet of the nitric acid reduction reaction tower via a pipeline. The advantages are: the reflux from the nitric acid reduction reaction tower reduces the consumption of nitric acid and liquid alkali; the methanol recovery tower recovers the methanol from the bottom liquid and refluxes it back to the primary esterification tower, significantly reducing the fresh methanol supply and achieving efficient methanol reuse, thus reducing the consumption of fresh raw materials.

Description

Technical fields: This utility model relates to the field of ethylene glycol preparation, and more specifically to a resource utilization system in the ethylene glycol esterification process. Background technology: Ethylene glycol, as an important basic chemical raw material, has wide applications in polyester synthesis, coatings, and pharmaceutical intermediates due to its esterification products. However, existing ethylene glycol esterification processes generate byproducts such as water and methanol. Furthermore, unreacted raw materials and intermediates need to be recycled through a rational process system to improve raw material conversion rate and product yield, thereby reducing production costs. The following problems commonly exist in actual production processes: 1. Incomplete recovery of byproducts: If byproducts such as methanol generated during esterification cannot be effectively recovered, it will reduce the purity of the target product and waste resources. 2. High risk of nitric acid treatment: As a reactant, the direct discharge of nitric acid residue will cause serious environmental pollution and pose certain safety hazards. Current processes mostly use simple neutralization to treat nitric acid residue, which is not only costly but also cannot achieve the recycling of nitric acid, which is not in line with the development concept of green chemical industry. Therefore, developing a resource recovery system for the ethylene glycol esterification process that can achieve efficient recovery of by-products and reduce environmental pollution has become an urgent technical problem to be solved. Utility Model Content: The purpose of this invention is to provide a resource recovery system in the ethylene glycol esterification process.

[0004] This utility model is implemented by the following technical solution: A resource recovery system for ethylene glycol esterification process includes a monoester tower, a diester tower, a nitric acid reduction reaction tower, and a methanol recovery tower; The outlet of the esterification circulating gas compressor is divided into three paths, which are respectively connected to the lower inlet of the primary ester tower, the secondary ester tower, and the nitric acid reduction reaction tower via pipelines; The outlet of the primary ester column is connected to the inlet of the first primary ester pump via a pipeline. The outlet of the first primary ester pump is connected to the inlet of the circulating heater via a pipeline. The outlet of the circulating heater is connected to the middle inlet of the primary ester column via a pipeline. The outlet of the circulating heater is also connected to the upper inlet of the diester column via a pipeline. The gas outlet at the top of the diester is connected to the middle inlet of the primary ester tower via a pipeline, the bottom liquid outlet of the diester tower is connected to the inlet of the second bottom liquid pump via a pipeline, and the outlet of the second bottom liquid pump is connected to the top liquid inlet of the diester tower via a pipeline. The outlets of the first and second reactor pumps are both connected to the top inlet of the nitric acid reduction reaction tower via pipelines; the top outlet of the nitric acid reduction reaction tower is connected to the inlet of the ester tower via a pipeline. The bottom liquid outlet of the nitric acid reduction reaction tower is connected to the middle inlet of the methanol recovery tower via a pipeline. The bottom liquid outlet of the methanol recovery tower is connected to the inlet of the methanol recovery tower bottom pump via a pipeline. The outlet of the methanol recovery tower bottom pump is connected to the middle liquid inlet of the nitric acid reduction reaction tower via a pipeline. The bottom liquid outlet of the nitric acid reduction reaction tower is also connected to the inlet of the nitric acid tower reflux pump via a pipeline. The outlet of the nitric acid tower reflux pump is connected to the inlet of the reaction tower preheater via a pipeline. The outlet of the reaction tower preheater is connected to the upper liquid inlet of the nitric acid reduction reaction tower via a pipeline.

[0005] Furthermore, the top outlet of the monoester tower is connected to the inlet of the first condenser via a pipeline, the outlet of the first condenser is connected to the inlet of the first reflux tank via a pipeline, the liquid phase outlet of the first reflux tank is connected to the inlet of the first reflux pump via a pipeline, the outlet of the first reflux pump is connected to the inlet of the cooler via a pipeline, and the outlet of the cooler is connected to the upper liquid inlet of the monoester tower via a pipeline.

[0006] Furthermore, the outlet of the methanol recovery reflux pump is connected to the inlet of the cooler via a pipeline.

[0007] Furthermore, the gas outlet at the top of the methanol recovery tower is connected to the inlet of the methanol recovery condenser via a pipeline, the outlet of the methanol recovery condenser is connected to the inlet of the methanol recovery reflux tank via a pipeline, the outlet of the methanol recovery reflux tank is connected to the inlet of the methanol recovery reflux pump via a pipeline, and the outlet of the methanol recovery reflux pump is connected to the upper liquid inlet of the methanol recovery tower via a pipeline.

[0008] Furthermore, the outlets of the methanol supply pipeline and the 30% nitric acid supply pipeline are both connected to the upper-middle inlet of the diester tower.

[0009] Advantages of this utility model: This invention increases the nitric acid conversion rate from 70% to 75% by reflux in the nitric acid reduction reaction tower, thereby reducing the consumption of nitric acid and liquid alkali. It also recovers methanol from the bottom liquid of the methanol recovery tower and refluxes it back to the primary ester tower, significantly reducing the amount of fresh methanol needed for replenishment and achieving efficient methanol reuse, thus reducing the consumption of fresh raw materials. Furthermore, the recycling of nitric acid and methanol reduces the discharge of alcohol-containing wastewater and nitric acid waste liquid, lowering subsequent environmental treatment costs, aligning with the concept of green chemistry, and significantly improving the economic benefits of enterprises. Attached image description: Figure 1 This is a schematic diagram of the system connection in this embodiment.

[0011] In the diagram: 1. Ester tower; 2. Diester tower; 3. Nitric acid reduction reaction tower; 4. Methanol recovery tower; 5. Esterification circulating gas compressor; 6. First reactor liquid pump; 7. Circulating heater; 8. Second reactor liquid pump; 9. Methanol recovery tower reactor pump; 10. Methanol recovery condenser; 11. Methanol recovery reflux tank; 12. Methanol recovery reflux pump; 13. First condenser; 14. First reflux tank; 15. First reflux pump; 16. Cooler; 17. Nitric acid tower reflux pump; 18. Reaction tower preheater; 19. Methanol supply pipeline; 20. 30% concentration nitric acid supply pipeline. Detailed implementation method: The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0013] Example 1: like Figure 1The illustrated resource recovery system for the ethylene glycol esterification process includes a monoesterification tower 1, a diester tower 2, a nitric acid reduction reaction tower 3, and a methanol recovery tower 4. The outlet of the esterification circulating gas compressor 5 is divided into three branches, which are respectively connected to the lower inlets of the monoesterification tower 1, diester tower 2, and nitric acid reduction reaction tower 3 via pipelines. The bottom liquid outlet of the monoesterification tower 1 is connected to the inlet of the first bottom liquid pump 6 via a pipeline. The outlet of the first bottom liquid pump 6 is connected to the inlet of the circulating heater 7 via a pipeline. The outlet of the circulating heater 7 is connected to the middle liquid inlet of the monoesterification tower 1 via a pipeline. The outlet of the circulating heater 7 is also connected to the upper liquid inlet of the diester tower 2 via a pipeline. The top gas outlet of the diester tower 2 is connected to the middle inlet of the monoesterification tower 1 via a pipeline. The bottom liquid outlet of the diester tower 2 is connected to the inlet of the second bottom liquid pump 8 via a pipeline. The outlet of the second bottom liquid pump 8 is connected to the bottom liquid outlet of the diester tower 2 via a pipeline. The top inlet of the nitric acid reduction reaction tower 3 is connected to the nitric acid reduction reaction tower 3; the outlet of the first bottom liquid pump 6 and the outlet of the second bottom liquid pump 8 are both connected to the top inlet of the nitric acid reduction reaction tower 3 through pipelines; the top gas outlet of the nitric acid reduction reaction tower 3 is connected to the gas inlet of the ester tower 1 through pipelines; the bottom liquid outlet of the nitric acid reduction reaction tower 3 is connected to the middle inlet of the methanol recovery tower 4 through pipelines; the bottom liquid outlet of the methanol recovery tower 4 is connected to the inlet of the bottom pump of the methanol recovery tower 4 through pipelines; the outlet of the bottom pump of the methanol recovery tower 4 is connected to the middle inlet of the nitric acid reduction reaction tower 3 through pipelines; the bottom liquid outlet of the nitric acid reduction reaction tower 3 is also connected to the inlet of the nitric acid tower reflux pump 17 through pipelines; the outlet of the nitric acid tower reflux pump 17 is connected to the inlet of the reaction tower preheater 18 through pipelines; and the outlet of the reaction tower preheater 18 is connected to the upper inlet of the nitric acid reduction reaction tower 3 through pipelines.

[0014] In this embodiment, the top outlet of the ester tower 1 is connected to the inlet of the first condenser 13 via a pipeline, the outlet of the first condenser 13 is connected to the inlet of the first reflux tank 14 via a pipeline, the liquid phase outlet of the first reflux tank 14 is connected to the inlet of the first reflux pump 15 via a pipeline, the outlet of the first reflux pump 15 is connected to the inlet of the cooler 16 via a pipeline, and the outlet of the cooler 16 is connected to the upper liquid inlet of the ester tower 1 via a pipeline.

[0015] The gas outlet at the top of the methanol recovery tower 4 is connected to the inlet of the methanol recovery condenser 10 via a pipeline. The outlet of the methanol recovery condenser 10 is connected to the inlet of the methanol recovery reflux tank 11 via a pipeline. The outlet of the methanol recovery reflux tank 11 is connected to the inlet of the methanol recovery reflux pump 12 via a pipeline. The outlet of the methanol recovery reflux pump 12 is connected to the upper liquid inlet of the methanol recovery tower 4 via a pipeline. The outlet of the methanol recovery reflux pump 12 is also connected to the inlet of the cooler 16 via a pipeline.

[0016] The outlets of methanol supply line 19 and 30% nitric acid supply line 20 are both connected to the upper-middle inlet of diester tower 2.

[0017] Job Description: The circulating gas (400-450 kPa, 70.0-90.0 °C) from the esterification circulating gas compressor 5 enters the lower part of the primary esterification tower 1, where it comes into countercurrent contact with the methanol solution sprayed down from the upper part and undergoes an esterification reaction to produce methyl nitrite (MN) and water, while also producing a certain amount of nitric acid as a byproduct. The gas after the reaction enters the first condenser 13 connected in series from the top of the primary esterification tower 1 and is cooled to 20-45 °C. Both the gas and liquid phases then enter the first reflux tank 14. The gas phase containing methyl nitrite escapes from the top of the tank and enters the carbonylation unit, while the liquid is cooled to about 5 °C by the first reflux pump 15 and the cooler 16 and refluxes back to the upper part of the primary esterification tower 1. The bottom liquid of the primary esterification tower 1 is a methanol-water solution containing a small amount of nitric acid. After being pressurized by the first bottom liquid pump 6, it is heated to 118±2℃ by the circulating heater 7. Part of it is sent to the middle section of the primary esterification tower 1 for recycling, and the other part is introduced into the side stream of the diester tower 2 through a pipeline to improve the utilization rate of nitric acid. After being pressurized by the first bottom liquid pump 6, a portion is also sent to the nitric acid reduction reaction tower 3. At the same time, the alcohol-containing wastewater discharged from the bottom of the diester tower 2 is pressurized by the second bottom liquid pump 8. Part of it, together with nitric acid from the 30% concentration nitric acid supply pipeline 20 and fresh methanol from the methanol supply pipeline 19, is added from the top of the first or second packing layer of the diester tower 2. The other part is sent to the nitric acid reduction reaction tower 3. NO in the gas phase and methanol and nitric acid in the liquid phase react countercurrently to generate methyl nitrite. Methyl nitrite enters the middle section of the primary esterification tower 1 with the gas phase. While the diester tower 2 is being put into operation, the replenishment of nitrogen oxides is gradually reduced.

[0018] Alcohol-containing wastewater discharged from the bottom of the monoesterification tower 1 and diester tower 2 enters from the top of the nitric acid reduction reaction tower 3 and flows downward. Part of the circulating gas from the esterification circulating gas compressor 5 enters the bottom of the nitric acid reduction reaction tower 3 and flows upward. The gas and liquid phases react countercurrently on the catalyst surface in the nitric acid reduction reaction tower 3. Nitric acid and methanol in the liquid phase react with nitric oxide in the gas phase to produce methyl nitrite, which is sent back to the monoesterification tower 1 with the gas phase at the top of the tower. The liquid at the bottom of the nitric acid reduction reaction tower 3 is pressurized into the methanol recovery tower 4 by the tower pressure. The methanol-water solution in the methanol recovery tower 4 is heated to 110±2℃ by the reboiler. The methanol vapor coming out of the top of the methanol recovery tower 4 is condensed by the methanol recovery condenser 10 and enters the methanol recovery reflux tank 11. It is pressurized by the methanol recovery reflux pump 12. Part of it is refluxed, and the other part is sent to the cooler 16 for cooling through the regulating valve and then refluxed back to the top of the monoesterification tower 1.

[0019] In this embodiment, the liquid phase from the bottom of the nitric acid reduction reaction tower 3 is refluxed through the nitric acid tower reflux pump 17 and fed into the tower together with the liquid phase from the top of the nitric acid reduction tower for circulation reaction. This achieves the recycling of nitric acid from the bottom of the tower, which can improve mass and heat transfer and increase the nitric acid conversion rate.

[0020] Before the improvement, the nitric acid reduction reaction tower 3 had a conversion rate of 70% and consumed 16 tons of nitric acid per day. After the improvement, the conversion rate of the nitric acid reduction tower reached 75%, consuming 15 tons of nitric acid per day, saving 1 ton of nitric acid per day and 0.5 tons of liquid alkali needed to neutralize the nitric acid. The daily benefit is approximately: 1t * 1200 yuan / t + 0.5t * 1300 yuan / t = 1850 yuan; The daily electricity cost of the newly added nitric acid tower reflux pump 17 is 7.5KW * 0.45 yuan / kw * 24h = 81 yuan; Daily net income: 1850-81=1769 yuan, annual income (calculated based on 300 days of operation): 530,000 yuan.

[0021] Meanwhile, in this embodiment, methanol participates in the esterification reaction as a raw material. The unreacted methanol will enter the nitric acid reduction reaction tower 3 with the bottom liquid of the tower, and finally be recovered by the methanol recovery tower 4 and reused in the primary ester tower 1, which reduces the amount of fresh methanol to be supplied, thereby generating economic benefits.

[0022] After the improvement, the daily methanol recovery volume is approximately 9 tons, and the market price of methanol is 2600 yuan / ton. Daily savings in fresh methanol costs: 9 tons / day × 2600 yuan / ton = 23400 yuan / day.

[0023] The total power of the newly added methanol recovery condenser 10, reflux pump, reboiler, etc. is 15kW, and the electricity cost is approximately 15kW × 0.45 yuan / kW•h × 24h = 162 yuan / day.

[0024] The net profit generated from methanol recycling is approximately 23,400 - 162 = 23,238 yuan per day.

[0025] Annual revenue (based on 300 days of operation): approximately 6.97 million yuan.

[0026] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A resource recovery system for the esterification process of ethylene glycol, characterized in that, This includes a monoester tower, a diester tower, a nitric acid reduction reaction tower, and a methanol recovery tower; The outlet of the esterification circulating gas compressor is divided into three paths, which are respectively connected to the lower inlet of the primary ester tower, the secondary ester tower, and the nitric acid reduction reaction tower via pipelines; The outlet of the primary ester column is connected to the inlet of the first primary ester pump via a pipeline. The outlet of the first primary ester pump is connected to the inlet of the circulating heater via a pipeline. The outlet of the circulating heater is connected to the middle inlet of the primary ester column via a pipeline. The outlet of the circulating heater is also connected to the upper inlet of the diester column via a pipeline. The gas outlet at the top of the diester is connected to the middle inlet of the primary ester tower via a pipeline, the bottom liquid outlet of the diester tower is connected to the inlet of the second bottom liquid pump via a pipeline, and the outlet of the second bottom liquid pump is connected to the top liquid inlet of the diester tower via a pipeline. The outlets of the first and second reactor pumps are both connected to the top inlet of the nitric acid reduction reaction tower via pipelines; the top outlet of the nitric acid reduction reaction tower is connected to the inlet of the ester tower via a pipeline. The bottom liquid outlet of the nitric acid reduction reaction tower is connected to the middle inlet of the methanol recovery tower via a pipeline. The bottom liquid outlet of the methanol recovery tower is connected to the inlet of the methanol recovery tower bottom pump via a pipeline. The outlet of the methanol recovery tower bottom pump is connected to the middle liquid inlet of the nitric acid reduction reaction tower via a pipeline. The bottom liquid outlet of the nitric acid reduction reaction tower is also connected to the inlet of the nitric acid tower reflux pump via a pipeline. The outlet of the nitric acid tower reflux pump is connected to the inlet of the reaction tower preheater via a pipeline. The outlet of the reaction tower preheater is connected to the upper liquid inlet of the nitric acid reduction reaction tower via a pipeline.

2. The resource recovery system for the ethylene glycol esterification process according to claim 1, characterized in that, The top outlet of the ester tower is connected to the inlet of the first condenser via a pipeline. The outlet of the first condenser is connected to the inlet of the first reflux tank via a pipeline. The liquid phase outlet of the first reflux tank is connected to the inlet of the first reflux pump via a pipeline. The outlet of the first reflux pump is connected to the inlet of the cooler via a pipeline. The outlet of the cooler is connected to the upper liquid inlet of the ester tower via a pipeline.

3. The resource recovery system for the ethylene glycol esterification process according to claim 2, characterized in that, The outlet of the methanol recovery reflux pump is connected to the inlet of the cooler via a pipeline.

4. The resource recovery system for the ethylene glycol esterification process according to claim 1, characterized in that, The gas outlet at the top of the methanol recovery tower is connected to the inlet of the methanol recovery condenser via a pipeline. The outlet of the methanol recovery condenser is connected to the inlet of the methanol recovery reflux tank via a pipeline. The outlet of the methanol recovery reflux tank is connected to the inlet of the methanol recovery reflux pump via a pipeline. The outlet of the methanol recovery reflux pump is connected to the upper liquid inlet of the methanol recovery tower via a pipeline.

5. The resource recovery system for the ethylene glycol esterification process according to claim 1, characterized in that, The outlets of the methanol supply pipeline and the 30% nitric acid supply pipeline are both connected to the upper-middle inlet of the diester tower.

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