4 Ways to Size Your Solvent Recovery Unit

First and foremost, if you are going to begin on-site chemical recycling, you must understand the processing capacity needed. This will, in turn, reveal the size of the unit that your plant requires. There are 4 criteria that must be evaluated to determine the capacity of the solvent recovery unit you need to process a solvent waste stream.

To begin, ask yourself: What is the average daily volume of solvent waste that is generated? This should be double checked against solvent waste currently processed and or shipped offsite for recycling or solvent disposal. Although this seems to be obvious, it isn’t always crystal clear, as we have experienced while helping our clients understand their solvent recycling needs. To do this, determine how much solvent waste is generated daily, weekly, monthly and or quarterly. Then check your numbers by reviewing your actual waste manifest, to ensure your data is correct. Another check is to review the amount of solvent purchased for cleaning.

For example, let’s say you believe the average daily volume of solvent waste generated to be 100 gallons. The next step would be to review the manifest, to determine the total amount of waste solvent shipped on a monthly or quarterly basis. Let’s say the answer is 60 drums every month. To check the math, we’ll multiply 60 drums by 52 gallons per drum to get 3,120 total gallons every month. Then, to convert that value to a daily measure, simply divide 3,120 gallons by 22 business days. The answer is 142 gallons of waste generated every day. This is a red flag, as the 142 gallons a day is a much different number than the original 100 gallons. We encourage you to check the waste manifests to verify actual waste shipments.  

After determining your current cleaning solvent needs, you should determine your future needs as well. You should discuss future solvent recycling needs with your production department in order to forecast future needs. A solvent distillation unit should last at least 5 years, but typically lasts in the range of 10 years. This means you should be looking at your usage needs over the next decade.

The next step would be to determine the time put into operating the solvent distillation unit. Some facilities elect to not run their solvent recycling unit overnight or throughout the weekend. However, with the modern technology our units provide, it can be very possible to run the machine 24 hours a day, 7 days a week. It is important to recognize that the machines will need maintenance and repairs. It’s simply not realistic to assume that the machine will be up and running at all times. Mechanical issues will occur from time to time. A good rule of thumb for facilities that purchase distillation equipment is to assume 85% uptime. However, some facilities will have a higher uptime than others. This is because uptime is almost completely dependent on personnel, which include the operator of the machine, maintenance department, and manager of the process. A once stellar on-site recycling program can change overnight when an operator or other key personnel change. Another important point to note is that uptime will not remain constant. When a facility first implements a solvent distillation unit, there is a lot of focus on the process, resulting in a much better uptime.  Unfortunately, when the excitement wears off and reality of the daily grind sets in, the solvent recycling unit will likely not have the same high level of focus and attention. We note this as a cautionary tale to ensure facilities are accurately estimating their uptime. The big takeaway here is that your solvent distillation unit must have excess capacity to account for inevitable downtime.

It would be great if the only requirement for finding the perfect solvent recycler was how much waste it processes in a day. But this is not the case. There are two other factors that must be considered: the boiling point of the solvent(s) that will be recovered by the solvent distillation equipment and the percentage of contaminate in the solvent cleaning waste stream. The higher the boiling point and percentage of contaminate in the solvent, the longer it will take for the machine to process the waste. Both factors, independently, impact the size of the unit needed for the facility. A higher boiling point solvent means that more energy is required to undergo the distillation process. This leads to an increase in time for the unit to reach the correct temperature, thus extending the recovery cycle. While a higher contamination means that machines will have to drain more often to ensure that material doesn’t become too viscous to process. More drain cycles equate to more time.