Seeking assistance in designing a solvent recovery and separation scheme

I hope everyone here can help me out. My boss is pressing me hard for this, and I’m an amateur with little knowledge in many areas; I really hope you’ll be kind enough to offer your guidance! Thank you!

Check the solvent manual to see if there is an azeotrope phenomenon; distillation isn’t necessary if not

This system is quite complex; it currently consists of 5 components, which belong to alcohols, benzenes, anilines, silicone oils, and halogenated hydrocarbons. There are several azeotropes listed in solvent manuals, and many more azeotropes for which no data are available in those manuals. You asked, “That’s the main material to be recycled,” and it’s you who decides that. The main criteria for determination include things such as high cost, a high content of certain components that makes it worth recycling, and the possibility of recycling and reusing it after simple processing. The main materials to be recovered need to be identified before the plan can be finalized. Another issue is the daily amount. For example, if the volume is large, there are more options to consider, such as distillation, extraction, absorption, membrane treatment, etc. If your volume is very small, say just one barrel per day, then some methods that require large investments are not practical. Also, there is the pH of your materials; aniline may decompose if its pH is not properly controlled at high temperatures.

Thank you very much to the female moderator for her detailed and in-depth analysis. I also have many doubts regarding this issue – specifically, what exactly is being separated, how much traffic there is, etc. No one in the group has provided me with any information on these matters, and since I’m an outsider in this field, I’m quite confused by it. That’s why I turned to all of you experts for advice! Their previous approach was to create a process simulation to analyze the energy consumption issues among different design options; other aspects were not addressed, and only an estimate of flow rate was made! Below, I’m pasting this design plan; please help take a look! Separation problem of the mixture recovered from lysosomes: The types and amounts of substances are as follows. Design a separation process that requires minimal energy consumption. Dichloromethane: 45% 40; Methanol: 4% 64; Hexamethyldisiloxane: 25% 101; Toluene: 20% 111; N,N-Diamine: 4% 193; The remainder are unknown impurities. Dichloromethane: English: Dichloromethane; structural formula CH2Cl2, molecular weight 84.93. A colorless, transparent, fluid liquid with an irritating odor similar to that of ether. Relative density (20 °C/4 °C): 1.3266; freezing point: -95.14 °C; boiling point: 40 °C; viscosity (20 °C): 0.43 mPa•s; refractive index: 1.4244; solubility parameter δ = 9.78. It is miscible with organic solvents such as ethanol, ether, benzene, propylene, and N,N-dimethylformamide. Slightly soluble in water. Not easily flammable. Toxic; irritating to skin and mucous membranes; releases toxic chloride gases when heated. The maximum allowable concentration in the air is 740 mg/m3 (or 0.05%). Used as a fast-drying solvent with strong dissolving power, capable of dissolving polycarbonate and similar materials. Store in a cool, well-ventilated warehouse, taking care to prevent moisture. Methanol: English name – methyl alcohol; Standard code in China: 32058; CAS number: 67-56-1; Molecular formula: CH4O; CH3OH; Molecular weight: 32.04. It is a colorless, clear liquid with an irritating odor. Its vapor pressure is 13.33 kPa at 21.2°C; the flash point is 11°C; the melting point is -97.8°C; and the boiling point is 64.8°C. It is soluble in water and can mix with most organic solvents such as alcohols and ethers. Density: relative density (water = 1) is 0.79; relative density (air = 1) is 1.11. Stability: stable. Hazard symbol: 7 (flammable liquid). Main uses: primarily used in the production of formaldehyde, fragrances, dyes, pharmaceuticals, antifreeze, etc.

Hexamethyldisiloxane: English name – HMDSO; Molecular formula: C6H18OSi2; Molecular weight: 162.38; CAS number: 107-46-0. Properties: density is 0.764. Melting point -59°C. Boiling point 101°C. Refractive index 1.3765-1.3785. Flash point -1°C. Water-soluble, insoluble. Toluene: English: Toluene; molecular weight 92.13. A colorless and transparent liquid with an irritating odor; relative density (20 °C/4 °C) is 0.866. Freezing point: -95°C, boiling point: 110.8°C, flash point (open): 7.2°C, ignition point: 552°C, refractive index: 1.4961, viscosity (20°C): 0.5866 mPa•s, surface tension (20°C): 28.53×10⁻³ N/m, solubility parameter δ = 8.9. It is miscible with ethanol, ether, benzene, propylene, carbon disulfide, and solvent gasoline. Insoluble in water. There is a risk of generating and accumulating static electricity. Flammable; its vapors form explosive mixtures with air, with an explosion limit of 1.27%–7.0% (vol). Toxic. It is highly irritating to the skin and mucous membranes, and its effect on the nervous system is stronger than that of benzene. Prolonged exposure may lead to bladder cancer. However, toluene can be oxidized to benzoic acid, which forms hippuric acid when combined with glycine; this compound can be excreted in urine, so it is not toxic to the blood. The maximum allowable concentration in the air is 100 mg/m3 (or 0.02%). N,N-Dimethylaniline: English name: N,N-dimethylaniline; National standard code: 61078; CAS number: 121-69-7; Molecular formula: C8H11N; C6H5N(CH3)2; Molecular weight: 121.18. Properties: Oil-like liquid; Vapor pressure: 0.13 kPa at 29.5°C; Flash point: 62.8°C; Melting point: 2.5°C; Boiling point: 193.1°C; Solubility: Insoluble in water, soluble in ethanol, ether, and chloroform; Density: Relative density (water=1): 0.96; Relative density (air=1): 4.17; Stability: Stable; Hazard symbol: 15 (Harmful, keep away from food); Main uses: Used as an intermediate in dyes, as a solvent, as a stabilizer, and as an analytical reagent. Property: Formerly known as dimethylaniline. A light **oily liquid. It has a special smell. Density 0.9563. Melting point 2.5°C. Boiling point 193°C. Insoluble in water, soluble in ethanol, ether, chloroform, benzene, and acid solutions. It can volatilize along with steam. Used in the production of vanillin, azo dyes, and triphenylmethane dyes, etc. It is formed by the reaction of aniline with methanol under high temperature and pressure in the presence of sulfuric acid. Separation sequence selection: A: Dichloromethane B: Methanol C: Hexamethyldisiloxane D: Toluene E: N,N-Di**amine
Plan 1: B1 BOTTOM_TEMP 125.698483°C REB_DUTY 0.44272696 MMkcal/hr B2 BOTTOM_TEMP 71.1496251°C REB_DUTY 1.60820062 MMkcal/hr B3 BOTTOM_TEMP 136.801543°C REB_DUTY 2.81243999 MMkcal/hr B4 BOTTOM_TEMP 202.178926°C REB_DUTY 0.10665356 MMkcal/hr
Plan 2: B1 BOTTOM_TEMP 101.66923°C REB_DUTY 0.46961441 MMkcal/hr B2 BOTTOM_TEMP 121.999428°C REB_DUTY 0.21223581 MMkcal/hr B3 BOTTOM_TEMP 136.80154°C REB_DUTY 2.81676495 MMkcal/hr B4 BOTTOM_TEMP 200.477616°C REB_DUTY 0.10642845 MMkcal/hr
Analysis: Based on a total feed rate of 5000 kg/hr, the energy consumption for B3/B4 is similar; the main differences in energy consumption occur between B1/B2. When Scheme 1 is adopted, the heating of B2 can be provided by the vapor at the top of tower B3 as a heat source. From this comparison, Plan 1 saves 0.23 MMkcal/hr of steam compared to Plan B. This post was last edited by yiqingjie on 2008-8-4 09:21]

Schemes 1 and 2 are distillation schemes for the separation of five components. Scheme 2 involves several columns connected in series to separate each component sequentially, while Scheme 1 first uses B1 to divide the five materials into two streams: 1) A: dichloromethane and B: methanol； 2) For C: Hexamethyldisiloxane D: Toluene E: N,N-Di**amine ； They were separated at one time each, and then the energy consumption of the two separation methods was compared! I’m curious to hear everyone’s opinions; I hope you’ll share your insights! Could you also send me some information on solvent recovery?»

The original poster hasn’t clarified many of the most important details. Specifically, it’s not clear what exactly needs to be separated; in other words, which substance you want to obtain from the mixture. This is the most crucial point – otherwise, no matter how many solutions are devised, they will be meaningless

The original poster hasn’t clarified many of the most important details. Specifically, it’s not clear what exactly needs to be separated; in other words, which substance you want to obtain from the mixture. This is the most crucial point – otherwise, no matter how many solutions are devised, they will be meaningless

This is indeed very difficult to do. It is estimated that a professional tower designer will need to be hired to design it.

There are too many components. We need to know what needs to be recycled? It’s impossible to recycle everything and get qualified products from it. Having a specific target makes it easier to answer. In solvent recovery in pharmaceutical factories, it is essential to have a clear goal first – what exactly is to be recovered.

It is possible to recycle everything, but 4 distillation towers are required to handle the 5 components.