Technical help: Has anyone worked on an “epoxy resin wastewater treatment project”?

Go and take a look at this site: http://bbs.hcbbs.com/thread-381548-1-1.html; you should find what you’re looking for there.

This post was last edited by hesonchang214 on 2011-4-20 15:20: Multi-effect evaporation crystallization salt process!

This post was last edited by hesonchang214 on 2011-4-20 at 15:24. I. Introduction Epoxy resin is produced by the reaction of bisphenol A and epichlorohydrin in the presence of sodium hydroxide; the by-products are NaCl and H2O. Crude epoxy resin needs to be refined in order to become commercial epoxy resin. Currently, the purification processes used both domestically and internationally rely on solvent extraction, which involves adding a solvent to a mixture of crude epoxy resin, NaCl, H2O, and excess NaOH. Since NaCl, H2O, and NaOH are insoluble in the solvent, they are separated from the resin solution by taking advantage of their density differences. To ensure that the residual Cl- ion content in the resin is low enough, four washes with water are generally required. As the number of washes increases, the Cl- ion content in the resin decreases, and accordingly, the COD level in the wastewater also decreases. The wastewater discharged after the first and second washes has a COD value of 7,000–15,000 ppm, making it completely unsuitable for biochemical treatment. The wastewater discharged after the third and fourth washes generally has a COD value of less than 6,000 ppm, allowing it to be treated via biochemical methods directly. This article discusses the treatment of high-concentration epoxy resin wastewater. 　　II. New closed-loop recycling process for treating high-concentration epoxy resin wastewater The components of high-concentration epoxy resin wastewater are quite complex, and can be mainly divided into three categories: 1) Organic substances: These are the macromolecular intermediates formed through the polycondensation reaction of bisphenol A and epichlorohydrin in the production of epoxy resin; they also contain small amounts of unreacted raw materials such as bisphenol A and the organic solvent toluene. The composition is complex, and this type of substance is commonly referred to as aged resin. 　　2) Inorganic ions: such as Na-, Cl-, OH-, etc. 　　3) Water: Tap water introduced during resin washing. 　　For such wastewater with complex components, there is currently no mature treatment technology that is readily accepted by enterprises in China. To this end, Wuxi Petrochemical Plant collaborated with the School of Biological Engineering at Wuxi Light Industry University to develop a new closed-loop recycling process for treating high-concentration epoxy resin wastewater on a laboratory scale. The process flow is as follows: The wastewater from the first and second washing steps (high-concentration wastewater) is mixed together and sent to a wastewater treatment tank, where a flocculant is added to cause the organic substances (hereafter referred to as oil) to separate from the water; the oil then floats on top of the water layer. Oil removal is carried out using the floating overflow method. The aqueous solution after oil removal is concentrated, and the concentrated solution is crystallized in a crystallization tank (the main component of the crystals is NaCl, with a small amount of NaOH as well; these are referred to as alkali salts). The alkali salt crystals are separated from the mother liquor, which is then recycled to the wastewater treatment tank, thus forming a closed circulation system for the material flow. 　　Since the logistics entities form a closed loop, the physical properties of each unit operation undergo significant changes at the beginning of the cycle as the number of cycles increases, showing substantial differences from those of the original wastewater. Control the process conditions of each unit operation so that the cycle reaches an equilibrium state after 5 to 6 batches, meaning that the properties at each operating point no longer change and remain within a certain range. Operation proceeds in cycles at equilibrium. 　　III. Materials entering and leaving the closed-loop cycle The materials that enter the cycle are the first and second batches of high-concentration wastewater generated during the washing of resin. Those that leave the cycle include: 1) Oil, namely aged resin – intermediate products, by-products from the resin polycondensation process, resin with an excessively high molecular weight as a result of overreaction, as well as a small amount of resin that has not fully dissolved, along with toluene, etc. This substance still has high viscosity and can be used as an adhesive, a additive in paints, or as a raw material for producing lower-grade resins; research and development on its use are currently underway. 　　2) Alkali salts, mainly NaCl with a small amount of NaOH, can be used as raw materials in the chlor-alkali industry or directly as dyeing auxiliaries, offering broad market prospects. 　　3) Evaporate the condensate water; its pH is approximately 6.5, which is near neutral. The Cl- level is less than 80 ppm, and the COD level is less than 500 ppm. This water can be used as water for the first and second washes of the resin. 　　IV. Experimental Data High-concentration wastewater discharged during the first and second resin washing sessions was collected and analyzed after mixing; the results showed a dry matter concentration of 10.2%, a specific gravity of 1.06, and 2.4% NaOH. 　　Following a closed-loop process, using the aforementioned wastewater as raw material, 6 batches were processed in continuous cycles without interruption. The results are as follows: Note that during the processing of the 6th batch, a small amount of mother liquor ended up in the evaporated and condensed water; nevertheless, the Cl- concentration was only 81.7 ppm, which is below the specified limit of 250 ppm for tap water. Therefore, it meets the requirements as water for the first and second washing steps. Cycle Batch 1 2 3 4 5 6
Mixed wastewater volume, ml: 1000 1082 1110 1100 1130 1111
Concentration, %: 10.2 12.8 14.0 14.3 15.2 15.0

Evaporation and condensation water volume, ml: 880 915 928 905 937 930
COD, ppm: 0 42.7 0 0 42.7 81.7
pH: 5.5 5.5 5.5 5.5 6.0 7.0
Cl-, ppm: 0.73 2.03 0.51 0 17.1 63.1

Aqueous solution from alkali salt crystallization volume, ml: 82 110 100 130 111 127
Specific gravity: 1.23 1.24 1.32 1.27 1.28 1.30
NaOH%, %: 20.4 29.4 38.4 36.4 41.6 42.0
Concentration, %: 44 48.4 55 54 58 58.5
COD, ppm: 161000 182000 209000 196000 278000 205000

Dry weight of alkali salt crystals: 67.1 86.3 97.8 92.1 101.1 101.5
NaOH%, %: 3.04 5.56 7.20 7.28 6.12 7.52
Moisture content, %: 9.4 9.6 14.4 13.4 7.3 6.7

As can be seen from the table above, by the fifth batch the system has essentially reached equilibrium. Therefore, the new closed-loop recycling process using epoxy resin to treat high-concentration wastewater not only helps to address the environmental problems caused by such wastewater but also transforms waste into a valuable resource, reducing the costs associated with wastewater treatment and increasing revenue from by-products. It represents an advanced technology for comprehensive wastewater treatment. 　　V. Design of the treatment facility for 10,000 tons of high-concentration epoxy resin wastewater Based on the experimental results, Wuxi Petrochemical Complex and the Food College of Wuxi Light Industry University carried out a joint design. The estimated investment was 3 million RMB. The main equipment selected includes: Serial Number Equipment Name Quantity 1 Reagent dissolution tank 1 2 Mixing and adjustment tank 1 3 Oil separation tank 1 4 Three-effect evaporation system 1 5 Crystallization tank 2 6 Resin storage tank 1 7 Vacuum pump 1 8 Centrifuge 2 9 Mother liquor storage tank 1 10 Condensate water storage tank 1 11 Liquid alkali storage tank 1 12 Pumps 10

VI. Trial operation of the wastewater treatment facility At the beginning of November 1998, the treatment facility for 10,000 tons of high-concentration epoxy resin wastewater was installed and put into trial operation. By mid-December, after adjusting various process parameters, it had reached normal operating conditions. To this end, during the trial operation and normal operation phases, we monitored the materials that left the closed-loop cycle. The temperature of the evaporated condensate water was 70–80°C, the pH was 6.0–7.0, the Cl- concentration was 80–175 ppm, the NaOH concentration was 27–32%, the NaCl content was 3–5.7%, the specific gravity was 1.32–1.38. Among the alkaline salts, the NaCl content was 92–94%, the NaOH content was 2.5–3.7%, and the moisture content was 4.0–5.3%. 　　This process is relatively easy to operate, with a logical flow; all materials that leave the circulation loop are utilized effectively. The evaporated condensate water is used as water for the first and second washes, NaOH serves as a raw material for the resin polycondensation reaction, and the alkaline salts are sold as auxiliaries in dyeing and printing processes, resulting in low operating costs. After four months of trial operation and operation, the design requirements were met. 　　VII. Conclusion The closed-loop recycling system for treating epoxy resin wastewater is a completely new process featuring low operating costs, ease of operation, and no risk of secondary pollution. It helped Wuxi Petrochemical Plant pass the inspections for compliant wastewater discharge in the Taihu Lake basin in 1998, and it is suitable for the epoxy resin production industry across the country, holding great potential for widespread adoption.

Our company has several successful cases in dealing with highly difficult wastewater; if you are interested, please get in touch with me

This post was last edited by yzhang2010 on 2011-12-13 at 14:06. There are **guideline technical specifications** for the treatment of epoxy resin wastewater. For this type of wastewater with high salt content and high organic matter levels, the first step is to separate the streams: the high-salt wastewater is subjected to evaporation and crystallization to recover the salt. The resulting condensed water, along with the low-salt wastewater, is then sent to a biochemical treatment system. Conducting biochemical treatment without separating the streams or removing salts is not feasible in practice

What kind of flocculant is being added? What is the flocculant? It seemed that at the epoxy resin industry conference a few days ago, it was said that this approach wouldn’t work.

This post was last edited by ray1513 on 2012-4-15 at 10:25. Epoxy resin wastewater contains both salts and organic substances; due to the high salt content, it hinders the normal biochemical treatment of this wastewater, so desalination is necessary first. Epoxy resin wastewater can be divided into high-salt wastewater and wastewater with a lower salt content. High-salt wastewater can be treated using evaporation crystallization, while the low-salt organic wastewater and the condensate water resulting from the evaporation of high-salt wastewater are fed into a biochemical system to remove organic substances, before being discharged in compliance with regulations.

Is this topic still under discussion? It’s possible to first concentrate it and extract the difficult-to-treat organic substances from it, then carry out deep oxidation to reduce the TOC to below 10, so that it can be used directly in ion-exchange membrane caustic production