Best Practices

How to Manage Feed Material for On-Site Solvent Recycling

Effectively managing your solvent waste streams is an easy way to increase the efficiency and cost savings of your on-site solvent recycling operation.

The CleanPlanet Team
February 17, 2021

What is Feed Material ?

The solvent waste material that an on-site solvent recycler processes is commonly called feed material. This material is the solvent waste stream generated from a cleaning process, for example, flushing paint lines or printing presses. The cleaning solvent waste stream is ideal for recycling on-site in a solvent distillation unit. Effectively managing this waste stream will maximize the yield or % of solvent recovered and the efficiency of the distillation process.

Managing Your Solvent Waste Streams

There are three essential points to keep in mind when it comes to managing your cleaning solvent waste stream:

Keep excess solids from contaminating your solvent cleaning waste stream.
Make sure you have a homogenous feed stream going into the distillation unit.
If high solids are present, use a settling module.

In most operations this cleaning solvent waste stream has less than 10% solids. Often the cleaning solvent stream at a facility is comingled with excess solid waste from cleaning vats, vessels, containers, trays along with bad or excess solid material like ink or paint. This process of comingling the waste has its roots in the way the hazardous waste industry manages waste. Most waste vendors train their customers to comingle the solid waste with the cleaning waste stream to reduce the cost of disposing of solid waste material. In addition, this approach is often used to reduce the number of waste profiles a facility needs to manage. This approach of comingling solid waste with the cleaning solvent waste stream will have a financial impact on your recycling process.

How Excess Solvents Affect Your Savings

Here is the financial impact broken down of a solvent waste stream with a high percentage of solids that recently implemented a solvent distillation unit.

Before Managing Excess Solids

3,432 gallons a month of feed material (3 drums (52g each) a day x 22 days). Using a CleanPlanet AlwaysClean 150 we were able to achieve a yield of 70% or 2,402g.

Monthly Processed Feed Gallons:

3,432g

Monthly Recovered Clean Solvent Gallons:

2,402g $2.75 gallon $6,605

Make-up solvent needed (2,750 gallons):

348g $6.50 gallon $2,262

Still bottom Material Generated:

1,030 g

Still Bottom Drums:

21 (1,030/50g) $175 per drum $3,675

Total Cost:

$12,542

After Managing Excess Solvents

Removing the excess solids ( 343 gallons for the month) resulted in 7 drums not being processed through the distillation unit. This resulted in a yield of 86%.

Monthly Processed Feed Gallons:

3,089g

Monthly Recovered Clean Solvent Gallons:

2,657g $2.75 gallon $7,307

Make-up solvent needed (2,750 gallons):

93g $6.50 gallon $605

Still bottom Material Generated:

858 g

Still Bottom Drums:

9 (432/50g) $175 per drum $1,575

Solid Waste Drums:

7 $250 per drum $1,750

Total Cost:

$11,237

Monthly Difference:

$1,305

Annual Impact:

$15,660

In addition to the financial impact, excessive solids will have an impact on the processing rates as well. The more solids, the slower the unit will process.

Alternatives for Managing Solids

If it is not possible to reduce the percentage of solids below 20% in the spent solvent cleaning stream, it is recommended that the use of a setting module to pre-treat the feed material. The settling module acts to do what the name implies, settle the solids in the lower part of the module and enable mostly waste solvent to be fed into the solvent distillation unit. The settling module will need to be drained on a regular basis; the frequency will depend on the percentage of solids in the solvent waste stream.

A homogenous blend of solvents and contaminants will enable the unit to produce a consistent amount of solvent. The best way to achieve this is mix or agitate the feed prior to transferring the material into the solvent distillation unit. The use of a tote, 350 gallons to 550 gallons as a vessel to feed the solvent recovery unit with a mixer or agitation is one of the best ways to process a spent solvent cleaning waste stream.

This is one of the many benefits of recycling spent solvents on-site. The solids content of the solvent cleaning waste stream is exposed to the solvent distillation unit operator. If excess ink or paint is wasted in the solvent cleaning process, the solvent recovery process will make that waste visible. The costs of ink and paint is usually much higher than solvent and reducing the waste of this material will produce significant savings.

Below is an illustration of an on-site solvent recovery process. The spent solvent settling module would be used with waste streams that contain a higher percentage of solids. The spent solvent holding tote contains a mixer to facilitate a well-mixed homogenous feed stream, which is transferred into the distillation unit.:

Manage Your Waste Stream. Manage Your Costs.

By properly managing your cleaning solvent waste streams you can ensure that the feed material going into your solvent recycler is free of excess solvents. This means increased recycling efficiency and more importantly, increased savings.

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