A method for continuously purifying neutralized wastewater generated in an ethyl maltol production process, a system thereof, and applications thereof

Abstract

The application provides a method and system for continuously purifying neutralized wastewater generated in an ethyl maltol production process and application thereof, and belongs to the technical field of chemical production. The method comprises the following steps: (1) pretreatment: flash evaporation of the neutralized wastewater, adjustment of pH value by liquid alkali, and obtaining pretreated neutralized wastewater; (2) mixing and extraction: pumping the pretreated neutralized wastewater and dichloromethane into a mixer for extraction; (3) post-treatment: after extraction, the heavy phase enters a heavy phase collection tank, distillation is performed, dichloromethane is distilled out for recycling, the remaining residue containing ethyl maltol enters a sublimation kettle to sublimate ethyl maltol semi-finished products, and the light phase is sent to a wastewater treatment system for wastewater treatment after secondary flash evaporation in a flash evaporation kettle. The method can improve the ethyl maltol yield, reduce the content of organic matter in the wastewater, reduce the wastewater treatment cost, and achieve the effects of cost reduction, energy saving and efficiency improvement.

Description

Technical Field

[0001] This invention belongs to the field of chemical production technology, specifically relating to a method, system, and application for continuous purification of neutralized wastewater generated during the production of ethyl maltol. Background Technology

[0002] Ethyl maltol, as a flavor modifier and aroma enhancer, has experienced rapid development both domestically and internationally due to its significant aroma-enhancing effect, recognized safety, and wide applicability. It is widely used in industries such as tobacco, food, beverages, fruit wine, and cosmetics. The production of ethyl maltol generates wastewater with high concentrations of organic pollutants, including a certain amount of ethyl maltol. Chinese utility model patent CN204039161U discloses a decolorization adsorption tower for ethyl maltol wastewater. This decolorization adsorption tower includes: a cylindrical body, upper and lower end caps respectively installed at both ends of the cylindrical body, an upper filter screen installed between the cylindrical body and the upper end cap, a lower filter screen installed between the cylindrical body and the lower end cap, a first filter plate at each end of the cylindrical body, and two filter heads and two pairs of sight glasses installed on the cylindrical body. The cylindrical body comprises an upper cylindrical body, a middle cylindrical body, and a lower cylindrical body connected in sequence, with adsorption resin layers installed inside the middle and lower cylindrical bodies. This decolorization adsorption tower can prevent filter screen clogging and is easy to transport and install, but the adsorption resin used and specific operating conditions are not disclosed, and the specific operation is complex and not easy to industrialize; Chinese invention patent CN112028165B discloses a method for recovering ethyl maltol from ethyl maltol production wastewater, including the following steps: 1) Adsorption step: Adjust the pH of the production wastewater to 1.5-2.5 and pump it to a polypropylene adsorption tower system for continuous adsorption operation; 2) Desorption step: Transport the methanol regenerated liquid into the adsorption-saturated polypropylene adsorption tower for desorption. 3) Distillation and concentration of regenerated liquid: The regenerated liquid is distilled and concentrated to recover methanol, and a concentrated liquid is obtained; 4) Gasification and recovery: The concentrated liquid is pumped into a titanium sublimation kettle, and the pressure and temperature are adjusted. The gas from the second gasification enters the receiving kettle A, is captured and recovered by the ethanol aqueous solution, centrifuged, and the precipitate is collected to obtain ethyl maltol. However, methanol has a high boiling point, and the water content in the methanol aqueous solution must reach more than 44% in order to extract the impurities in the methanol. The extracted methanol has a high water content, which causes a large consumption of raw material methanol, increases production costs, and fails to achieve the purpose of energy saving and efficiency improvement.

[0003] The neutralization mother liquor generated during the production of ethyl maltol is extracted and then fed into a neutralization wastewater tank. After flash evaporation, it is directly sent to wastewater treatment. Daily sampling and analysis of the neutralized wastewater after flash evaporation show that the wastewater is acidic, which can easily corrode wastewater treatment equipment. Moreover, the chemical oxygen demand (COD) is as high as 100,000 mg / L, and a certain amount of ethyl maltol dissolves in the neutralization wastewater and is not fully recovered, resulting in waste. At the same time, the high COD makes wastewater treatment difficult and increases wastewater treatment costs. Currently, the neutralization mother liquor is extracted using chloroform, but this method has the disadvantage of not being able to fully precipitate the maltol from the mother liquor, resulting in a high maltol content in the wastewater and losses. In addition, the extracted material has a large amount of residual chloroform, which affects product quality.

[0004] Therefore, there is an urgent need to provide a method for the continuous purification of neutralized wastewater generated during the production of ethyl maltol, which can improve the recovery efficiency of ethyl maltol from wastewater, reduce the chemical oxygen demand (COD) of wastewater, and save energy and increase efficiency. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method, system, and application for the continuous purification of neutralized wastewater generated during the production of ethyl maltol. By further purifying the neutralized wastewater using the method of this invention, ethyl maltol is recovered, increasing the yield and profit of ethyl maltol. Simultaneously, the COD of the wastewater is significantly reduced, simplifying wastewater treatment and promoting cost reduction and efficiency improvement. Furthermore, by replacing the traditional chloroform extractant with dichloromethane, the lower boiling point of dichloromethane (39.8°C) results in less residue in the recovered material, ensuring product quality and achieving energy savings and efficiency improvements.

[0006] One objective of this invention is to provide a method for continuously purifying neutralized wastewater generated during the production of ethyl maltol, the method comprising the following steps:

[0007] (1) Pretreatment: After flash evaporation, the neutralized wastewater is fed into the neutralized wastewater collection vessel. The liquid level and temperature are adjusted, and the pH value is adjusted with liquid alkali to obtain pretreated neutralized wastewater.

[0008] (2) Mixing and extraction: The pretreated and neutralized wastewater and dichloromethane are pumped into a mixer for extraction;

[0009] (3) Post-processing: After extraction, the heavy phase enters the heavy phase collection tank, the liquid level is adjusted, and the dichloromethane contained in the heavy phase is distilled out and recycled through a distillation kettle. The remaining residue contains ethyl maltol, which enters the sublimation kettle to sublimate into ethyl maltol semi-finished product. The light phase is flashed twice in a flash kettle to obtain the treated neutralized wastewater, which is then sent to the wastewater treatment system for wastewater treatment.

[0010] Preferably, the liquid level in step (1) is such that the neutralized wastewater accounts for 40%-80% of the total volume of the neutralized wastewater collection vessel.

[0011] Preferably, the temperature in step (1) is 25-35℃.

[0012] Preferably, the pH value in step (1) is 5-7.

[0013] Preferably, the flow ratio of pretreated neutralized wastewater to dichloromethane in step (2) is 5-10:0.5-1.

[0014] Preferably, in step (3), the heavy phase enters the heavy phase collection tank, and when the liquid level reaches 70-80%, it is placed into the distillation kettle, and the kettle temperature is controlled at 45-55℃. The gas phase is condensed by the condenser and then enters the dichloromethane recovery tank for recycling. The residue is sent to the sublimation kettle to sublimate the ethyl maltol semi-finished product.

[0015] Preferably, in step (3), the light phase is flashed in the flash evaporator and then sent to the wastewater treatment system, and the temperature of the flash evaporator is 50-60℃.

[0016] A second aspect of the present invention is to provide a system suitable for the above-described method, the system comprising the following equipment: a liquid alkali tank, a neutralized wastewater collection vessel, a mixer, a heavy phase collection tank, a distillation vessel, a sublimation vessel, a flash evaporation vessel, a dichloromethane feed tank, a circulating pump, and PTFE piping; wherein the liquid alkali tank is connected to the neutralized wastewater collection vessel, the neutralized wastewater collection vessel is connected to the mixer, the dichloromethane tank is connected to the mixer, the lower inlet of the mixer is connected to the heavy phase collection tank, the heavy phase collection tank is connected to the distillation vessel, the distillation vessel is connected to the sublimation vessel, and the upper inlet of the mixer is connected to the flash evaporation vessel.

[0017] A third aspect of the invention relates to the application of the above-described method or a system adapted to the above-described method in the continuous purification of neutralized wastewater generated during the production of ethyl maltol.

[0018] Preferably, the content of ethyl maltol in the wastewater is reduced from about 3.5% to below 0.3%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) After further purification of the neutralized wastewater by the method of the present invention, the content of ethyl maltol in the wastewater is reduced from about 3.5% to less than 0.3%. Currently, about 80 cubic meters of wastewater after neutralization flash evaporation are generated every day. After purification of the wastewater generated at this daily output, about 200 kg of ethyl maltol can be recovered every day, about 200*30=6 tons per month, which increases profits; (2) After treating the neutralized wastewater by the method of the present invention, the COD content is significantly reduced from 100,000 mg / L in the traditional process to about 20,000 mg / L, which reduces the difficulty of wastewater treatment and promotes cost reduction and efficiency improvement in wastewater treatment; (3) In the method of the present invention, after replacing the extractant from the traditional chloroform to dichloromethane, since the boiling point of dichloromethane is low (39.8℃), there is less residue in the recovered material, which ensures product quality and achieves energy saving and efficiency improvement at the same time. Attached Figure Description

[0020] Figure 1 Flowchart of the method for continuous purification of neutralized wastewater generated during the production of ethyl maltol in Example 1 of this invention. Detailed Implementation

[0021] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0022] Example 1

[0023] A method for continuously purifying neutralized wastewater generated during the production of ethyl maltol, the method comprising the following steps:

[0024] (1) Pretreatment: After flash evaporation, the neutralized wastewater enters the neutralized wastewater collection vessel. The liquid level is adjusted to 60%, the temperature is 30℃, and the pH value is adjusted to 6 by liquid alkali.

[0025] (2) Mixing and extraction: Neutralized wastewater and dichloromethane are pumped into a mixer with a flow ratio of neutralized wastewater to dichloromethane of 10 for extraction.

[0026] (3) Post-processing: After extraction, the heavy phase enters the heavy phase collection tank. When the liquid level reaches 75%, it is distilled in a distillation kettle. The temperature of the distillation kettle is controlled at 50°C to distill out the dichloromethane contained in the heavy phase for recycling. The remaining residue contains ethyl maltol, which enters the sublimation kettle to sublimate the ethyl maltol semi-finished product. The light phase is flash-distilled twice in a flash kettle at 55°C and then sent to the sewage treatment system for sewage treatment.

[0027] Example 2

[0028] A method for continuously purifying neutralized wastewater generated during the production of ethyl maltol, the method comprising the following steps:

[0029] (1) Pretreatment: After flash evaporation, the neutralized wastewater enters the neutralized wastewater collection vessel, and the liquid level is adjusted to 40% and the temperature is 25℃. The pH value of the liquid alkali is adjusted to 5.

[0030] (2) Mixing and extraction: Neutralized wastewater and dichloromethane are pumped into a mixer with a flow ratio of neutralized wastewater to dichloromethane of 5 for extraction.

[0031] (3) Post-processing: After extraction, the heavy phase enters the heavy phase collection tank. When the liquid level reaches 70%, it is distilled in a distillation kettle. The temperature of the distillation kettle is controlled at 45°C to distill out the dichloromethane contained in the heavy phase for recycling. The remaining residue contains ethyl maltol and enters the sublimation kettle to sublimate the ethyl maltol semi-finished product. The light phase is flashed twice in a flash kettle at 50°C and then sent to the sewage treatment system for sewage treatment.

[0032] Example 3

[0033] A method for continuously purifying neutralized wastewater generated during the production of ethyl maltol, the method comprising the following steps:

[0034] (1) Pretreatment: After flash evaporation, the neutralized wastewater enters the neutralized wastewater collection vessel, and the liquid level is adjusted to 80% and the temperature is 35℃. The pH value is adjusted to 7 by liquid alkali.

[0035] (2) Mixing and extraction: Neutralized wastewater and dichloromethane are pumped into a mixer with a flow ratio of neutralized wastewater to dichloromethane of 20 for extraction.

[0036] (3) Post-processing: After extraction, the heavy phase enters the heavy phase collection tank. When the liquid level reaches 80%, it is distilled in a distillation kettle. The temperature of the distillation kettle is controlled at 55℃ to distill out the dichloromethane contained in the heavy phase for recycling. The remaining residue contains ethyl maltol and enters the sublimation kettle to sublimate the ethyl maltol semi-finished product. The light phase is flashed twice in a flash kettle at 60℃ and then sent to the sewage treatment system for sewage treatment.

[0037] Comparative Example 1

[0038] The difference from Example 1 is that dichloromethane in Example 1 is replaced with chloroform, and the temperature of the distillation vessel in step (3) is 65°C. The temperature of the flash evaporator is 75°C. The rest is the same as in Example 1.

[0039] Comparative Example 2

[0040] The difference from Example 1 is that step (1) does not adjust the pH value. The rest is the same as in Example 1.

[0041] Test example:

[0042] The percentage content and COD value of ethyl maltol before and after wastewater treatment in Examples 1-3 and Comparative Example 1 were determined, and the recovery rate of ethyl maltol and the COD removal rate were calculated. Wastewater COD was determined according to the standard "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ828-2017); ethyl maltol was determined according to the standard "National Food Safety Standard for Food Additives - Ethyl Maltol" (GB1886.208-2016). The recovery rate of ethyl maltol and the COD removal rate were calculated using the following formula:

[0043]

[0044] Meanwhile, the purity of the recovered ethyl maltol was determined by gas chromatography using an Agilent 7820A chromatograph.

[0045] The results are shown in Tables 1 and 2.

[0046] Table 1. Results of Ethyl Maltol Determination Before and After Wastewater Treatment in Examples 1-3 and Comparative Example 1

[0047]

[0048] Table 2. COD measurement results before and after wastewater treatment in Examples 1-3 and Comparative Example 1.

[0049]

[0050] As can be seen from the above data, compared with Comparative Examples 1-2, Examples 1-3 of the present invention have improved in terms of the purity of the recovered ethyl maltol, as well as the recovery rate of ethyl maltol and the COD removal rate. At the same time, since chloroform in Comparative Example 1 has a high boiling point and a large amount remains in ethyl maltol, it affects product quality while failing to achieve energy saving and efficiency improvement. In contrast, the dichloromethane of the present invention has a low boiling point (39.8°C), and there is less residue in the recovered material, which ensures product quality and achieves the purpose of energy saving and efficiency improvement.

[0051] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for continuously purifying neutralized wastewater generated during the production of ethyl maltol, characterized in that, The method includes the following steps: (1) Pretreatment: After flash evaporation, the neutralized wastewater enters the neutralized wastewater collection vessel. The liquid level and temperature are adjusted, and the pH value is adjusted with liquid alkali to obtain pretreated neutralized wastewater. (2) Mixing and extraction: The pretreated and neutralized wastewater and dichloromethane are pumped into a mixer for extraction; (3) Post-processing: After extraction, the heavy phase enters the heavy phase collection tank, the liquid level is adjusted, and it is distilled in a distillation kettle to distill out the dichloromethane contained in the heavy phase for recycling. The remaining residue contains ethyl maltol, which is sublimated in a sublimation kettle to produce ethyl maltol semi-finished product; the light phase is flash-distilled twice in a flash evaporator and then sent to the wastewater treatment system for wastewater treatment; among which, The pH value in step (1) is 5-7; in step (3), the temperature of the distillation vessel is 45-55℃ and the temperature of the flash evaporator is 50-60℃.

2. The method according to claim 1, characterized in that, In step (1), the liquid level is such that the neutralized wastewater accounts for 40%-80% of the total volume of the neutralized wastewater collection vessel.

3. The method according to claim 1, characterized in that, The temperature in step (1) is 25-35℃.

4. The method according to claim 1, characterized in that, The flow ratio of pretreated neutralized wastewater to dichloromethane in step (2) is 5-10:0.5-1.

5. The method according to claim 1, characterized in that, In step (3), the heavy phase enters the heavy phase collection tank. When the liquid level reaches 70-80%, it is placed in the distillation kettle. The gas phase is condensed by the condenser and then enters the dichloromethane recovery tank for recycling. The residue is sent to the sublimation kettle to sublimate the ethyl maltol semi-finished product.

6. A system applicable to the method of any one of claims 1-5, characterized in that, The system includes the following equipment: liquid alkali tank, neutralized wastewater collection vessel, mixer, heavy phase collection tank, distillation vessel, sublimation vessel, flash evaporator, dichloromethane feed tank, circulating pump, and PTFE piping; wherein the liquid alkali tank is connected to the neutralized wastewater collection vessel, the neutralized wastewater collection vessel is connected to the mixer, the dichloromethane tank is connected to the mixer, the lower end of the mixer is connected to the heavy phase collection tank, the heavy phase collection tank is connected to the distillation vessel, the distillation vessel is connected to the sublimation vessel, and the upper end of the mixer is connected to the flash evaporator.

7. The application of the method according to any one of claims 1-5 or the system according to claim 6 in the continuous purification of neutralized wastewater generated during the production of ethyl maltol.

8. The application according to claim 7, characterized in that, The content of ethyl maltol in the wastewater decreased from about 3.5% before treatment to less than 0.3% after treatment.

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