FAQ- Frequently Asked Questions

What is the purpose of vacuum on a distillation system?

There are many reasons to have a vacuum unit on a distillation unit. These include the following:

• Drop the boiling point of the solvent.
• Reduce the energy needed to distill the solvent.
• Make the distillation process more manageable.
• Prevent nitrocellulose reactions.
• Prevent deterioration of the solid content.
• Prevent deterioration of solvents.
• Improve certain solvent separation techniques.

When would I use atmospheric distillation?

When the boiling point of the solvent is very low and there would be issues of having to have very cold water to condense the vapors.
When there is a tendency to have foaming. Vacuum will make this situation worse.
When the boiling point of the solvent is 250 °F or below.
When there is no nitrocellulose present.


What is nitrocellulose?

Nitrocellulose is a highly flammable compound that is used in many products including printing inks, and finishes such as paints and varnishes. Special precautions need to be taken to be sure the nitrocellulose is not allowed to dry.


I only have a little nitrocellulose. Why do I need a nitrocellulose safety package?

Even a small amount of nitrocellulose can cause a reaction and create a safety hazard. A solvent distillation system must be designed to prevent reactions, and if they do occur, quench the reaction to prevent personal injury and damage to the equipment.


What are some of the factors that affect the distillation rate?

Different solvents require different quantities of heat for distillation. If they are blended with other solvents, the interaction of the solvents may affect the rate.
The amount of contaminant in the solvent will affect the heat transfer rate.
Your heat source will be a factor. Steam has the ability to transfer heat faster than hot oil.
Any water in the solvent will slow down the distillation process.
Whether distillation occurs under vacuum or atmospheric pressure.


What type of maintenance needs to be performed on a still?

A distillation unit will work for many years with a minimum of maintenance.
The heat transfer oil should be checked annually and changed as required.
On scraped units, a visual inspection of the blade condition should be done annually.
Gaskets should be visually checked on a routine basis and replaced if necessary.
Vacuum pump strainers should be cleaned.


What type of permits will I need for this equipment?

Appropriate local permits, including construction and necessary air permits. Emissions from a distillation unit are very small and may not need a permit.
You do not need an EPA permit to recycle the solvents that your own firm produces at that facility.


Why should I have a unit with internal scraper blades?

If your dirty solvent has high solids content, the scraped unit will prevent the solids from building on the side of the unit and reducing the heat transfer. It will also make it easier to dump the still bottoms.


Isn’t distillation dangerous?

Distillation in a properly designed unit for the solvent you wish to recover is a very safe process. Units are designed to meet all the applicable standards for the application and have many sensors and safety devices built in to prevent problems.
Make sure all your equipment is designed to be installed and operated in a Class 1 Division 1 area.
PRI has thousands of units working in the field with an outstanding safety record.


I do not have a classified area in which to put a unit. What alternatives can you offer?

There are many options in this situation. Units can be designed for outdoor installation or they can be built as self contained Class 1, Division 1 or 2 enclosures.


When would I want to use a microwave distillation unit?

These specialty units allow you to remove all the solvent content from the waste stream leaving only a solid material to be disposed of. This solid may be land filled in many applications or reused in your process.
If your solvent is very expensive, recovering 100% of it may have an economic advantage over standard distillation alone.


Why should I have a sample of my solvent tested?

The contaminant in a solvent may significantly affect the distillation characteristics. Testing a sample in a lab situation will determine the distillation characteristics, what percent recovery can be expected, develop the operational setpoints of the unit, determine whether there are any problems with the still bottoms and be sure there is clean distillate recovered with no carry over.


Can I separate solvents through distillation?

Partial or complete separation can be achieved depending on the particular solvents being used. If high purity levels of distillate are required, enrichment towers (fractionation columns) can be used to achieve the desired results.


Can I separate water from solvents?

Water can be separated dependent upon azeotrope binding and binary distillation characteristics. Resin adsorption can be used to further separate the water resulting in high degrees of solvent purity. Membrane technology from Sulzer can also be used to separate solvents.


Who is Sulzer Chemtech?

Sulzer Chemtech is our partner in the United States for pervaporation and vapor permeation technology.


How much labor should I allocate per day to run a distillation system?

Distillation can be a manual operation or fully automated. A small system can be timer controlled and work to and from drums. This type of system may involve an hour a day of labor. Larger systems can be fully automated and not require any labor on a routine basis.


I want to run a distillation system for only 8 hours per day. Is this feasible?

As with any piece of equipment, the smaller the unit and the more hours it operates, the more cost effective it will be. A unit that only runs 8 hours per day may need to be greatly oversized and very expensive compared to a unit that would be allowed to operate up to 24 hours per day. PRI designs units to run unattended, 24 hours per day for some applications.


What do I do with the sludge leftover from the distillation process?

Most sludge will be a liquid hazardous waste and need to be disposed of through a licensed hazardous waste service. This type of service is readily available in all areas. The least expensive waste to dispose of will be one that is pumpable and not solid.


Why can’t I cook the sludge into a solid and then dispose of it in my trash?

Regardless of how dry that sludge appears, the EPA has declared that if there were listed solvents in the distillation process, then the sludge is assumed to contained those solvents and must be disposed of as a solid hazardous waste.


Is it safe to allow distillation equipment to run un-attended?

There are multiple levels of sensors and safety equipment built into a system. If any operating parameter falls out of its normal range, the equipment will safely shut down and indicate an alarm situation.


How to I troubleshoot alarm situations?

Systems that have text and graphic operator interface screens also have “Help” screens available for each specific alarm condition. These screens give the most common causes of a particular alarm that can be checked by an operator or maintenance man. An alarm history is also maintained to allow supervisors to see a history of alarms.


How do I keep operators from changing the operating parameters?

There are several levels of security available on systems. Operators may have no, or limited authority to make changes. Supervisors will have access to make changes to the operating parameters.


I can’t find the problem with my unit. Now what?

Give our customer service department a call and describe the problem. They may be able to walk you through a troubleshooting process or may refer you to a field service technician for more advice. Our customer service folks have more than 25 years experience between them and have actually worked in the field.


Phone calls have not been able to fix the problem. Now what?

PRI has a staff of full time Field Service Technicians. You may want to have one of them visit your site to troubleshoot and repair your unit.


Why do you ask so many questions? I just want a quote on a still.

There are many factors that need to be taken into account to be sure that we understand what you want to accomplish, how it fits into your facility and manner of operation. A distillation unit should last 15 years or more so you need to be sure all factors are taken into account up front.


How do your units compare to a wiped film (thin film) evaporator?

Wiped film (thin film or WFE) evaporators are designed to run in an application where is there is a continuous input from a manufacturing process and the composition of the input does not change significantly. PRI’s units are designed to handle variable waste streams with little or no input from an operator. Because PRI’s systems do not use high speed rotating parts and do not require tight tolerances, little maintenance is required compared to a wiped firm unit.


What do the distillation rates found in catalogs mean?

Distillation rates found in catalogs are a means of comparison between units from the same manufacturer. Because there is no standard way of rating units there is no way to compare units from different manufacturers unless they have provided information specific to your solvent(s), its level of contamination, nature of the solids, type of heat source and many other factors.


Why can’t you just quote me a 50 gallon per hour still?

Distillation rates on equipment can’t easily be condensed to a single number. Distillation rates early in a cycle are low because the unit is heating up. There will be a few hours of peak output and then the rate will drop off as the solids build up in the unit.
Instead of talking about gallons/hour we need to talk about the quantity of solvent that will be processed over a given period of time. Usually this will be in gallons per day (8, 12, 24 hours?) or in gallons per week (5, 6, or 7 days?). This will take into account the changes in the output of a unit over that time period and make sure that we meet the demands of your application.


Why do I need field service start-up?

A field service technician will commission the unit, determine operational profiles and parameters and train the personnel on the system’s operation and preventative maintenance procedures. Training ensures the understanding of the system which enhances safety, efficiency and service life.


How much can I reduce my waste solvent?

Normally, recovery will be around 85 – 95% of the available solvent. This is
dependent on the make-up of the dirty solvent, the nature of the contamination and the distillation unit.


Why don’t you offer turnkey installations?

We are an equipment manufacturer. There are companies who specialize in equipment installations and have crews who do this as a living and we just couldn’t compete with local labor that is familiar with local codes and requirements.


Do I have to order parts from you?

No. Most of our parts are readily available from a multitude of sources.


What is the delivery time on equipment?

It all depends on the activity in our engineering department and shop status. Some equipment is easier to build than others and some designs are more standard than others.


Can I get a list of references?

We have extensive lists in many of the industries that we have worked in and we can provide that upon your request.