Frequently Asked Questions:

We receive many general questions about used oil re-refining, base lube oils and specific questions to our Used Lube Oil Re-refining process. If you have specific questions, we would love to hear from you. Please contact us via web, email or phone. Some of the frequently asked questions and their answers are listed below


Q: What is the Thermopac Used Oil Re-refining process?

A: For complete description of our process, please follow the link . The Thermopac used oil re-refining process starts with pre-treating steps to first remove fine solids, which can consist of particulates of dust, metals, carbon and inorganic oxidation products. Then it passes through Stage 1 – Dehydation and De-gas, which removes water and light hydrocarbon components from the feed. The light hydrocarbons can range from naphtha to gasoline to kerosene to diesel. Then, a gasoil fraction is removed. The light oil and gasoil can be used as fuel in the plant or sold as by-products. If they are both to be used as heat source for internal requirements, they can be removed in one step and eliminate a step in the process. After the removal of water and light hydrocarbons, the feed is subjected to Stage 2 – TWFE with High Vacuum Molecular Distillation, where specially designed short path wiped film evaporator is used to separate the lube oil fractions. Depending upon customer end-product requirements, one to three TWFE units may be used in series, producing base lube grades from light (SN 150) to medium (SN 300) to heavy (SN 400/500). Stage 2 is one of the most critical steps in our process. The TWFE units operate under carefully controlled vacuum so that the distillation occurs well below the temperature that would cause the lube oil to crack and degrade. The dissolved impurities in the lube feed end up in the solid residue at the bottom of the TWFE units. The solid residue also contains residual solids and asphaltenes, and can be sold as a by-product for blending with asphalt. The distilled lube oil fractions produced in the TWFE are then subjected to the finishing step in Stage 3. The Stage 3 details vary, based upon the customer requirements. If the desired end product is API Group I base oils, then an Activated Clay Finishing process is used. The resulting product is light yellow in appearance. If API Group II base oils is the desired end-product, then the distilled lube fractions are subjected to hydrogenation (hydrotreating). Hydrotreating removes sulfur, nitrogen and chlorine from the base lube oil feed, as well as saturates olefins and unsaturated aromatics. The resulting product is water-white and meets API Group II Base Lube Oil specifications. Stages 4 and 5 process the gaseous emissions and water removed in Stage 1 and are for the necessary pollution control purpose. Stage 6 involves packaging and/or bulk dispatch of the refined base oil product.


Q: What competing technologies are used for Used Oil Re-refining?

A: A number of competing technology processes are offered in the marketplace. The simplest forms of re-refining involve filtration or centrifuge and removal of water. The resulting product is of low quality and has limited uses. Generally, the product from this type of process is used as fuel. The next level of process being offered involves simple vacuum distillation after water removal. The product produced by this process can be used as a marine fuel but the yield is generally low and a lot of the incoming feedstock ends up as a low value asphalt blending component. It will not meet API motor oil specifications.
There are also processes that extract the lube oil from the waste oil with solvent extraction. The product produced in this process is better than the simpler processes and the yield of lube oil is better but the best that can be achieved is Group I motor oil. On the other extreme, there are processes that employ only hydrogenation which is both capital and O&M cost-intensive.


Parameter Propane Solvent Extraction Hydrogenation TWFE with Molecular Distillation
Capital Investment Very High Very High Medium
Cost of Production High High Low
Process Hazards High High Low
Type of Operation Automatic Automatic Automatic
Type of Process Continuous Continuous Continuous
Finishing Requirement 3-5 % Clay or Hydro finishing Nil 3-5 % Clay or Hydro finishing
Lube Oil Yield 65-68% 65-67% 75-77%

In our process, we use WTFE, a proprietary design thin film evaporation to maximize the yield of lube oil and Activated Clay Finishing or Hydrotreating to produce a product equal in quality to base oil from virgin crude oil.


Q: What are the advantages of Thermopac process over the others?

A: There are competitors in the marketplace who also employ combination of thin film evaporators and clay finishing/hydrotreating, but they are either custom-build only or will supply only design package. Thermopac can be your one-stop, end-to-end partner. Our capabilities range from engineering services to implementing turn-key contracts. There are many advantages of our approach over our competttors:


  1. We use a factory-built pre-packaged modular skid-mounted standard approach, which greatly assures a consistent and high quality product and at a lower capital cost. At the same time, we provide the customers the flexibility to define their requirements and work with us to deliver customer-specific solutions.
  2. Robust construction enhances the life of the plant
  3. Skid-mounted design enables complete assembly and pre-testing of the plant at our factory prior to despatch, which also reduces the site set-up time and cost
  4. Modular construction approach enables ease of capacity enhancement by adding different modules of skids in future
  5. The TWFE equipment is optimally designed for handling the used lube oil feed, enabling the process to maximize the recovery of the useful base lube oils.
  6. Entire setup is automated, with PLC and SCADA System, which reduces the plant personnel requirements, thereby reducing the operations cost.

Q: What is Group I / Group II Base Lube Oil?

A: API Group II motor oil must contain less than 300 parts per million of sulfur and have at least 90% saturated hydrocarbons. Hydrotreating is the only means to achieve the low sulfur and high degree of saturated hydrocarbon content.


Q: What feedstock(s) can I use?


Used lube oil feed may include

-              Motor Oil
-              Cutting fluids
-              Hydraulic oils
-              Turbine oil                          
-              Transformer oil
-              Machine oils
-              Air compressor oils
-              Slide-way lubes
-              Gear oils
The most common feedstock is used motor oil. The feedstock should not have high chlorine content such as parts washing or transformer oils with polychlorinated biphenyls (PCB's). These materials are hazardous and must be disposed of according to State and Federal regulations.
Thermopac process can handle used oil feed of mixed hydrocarbons containing:
~ 5 % water
~ 5 - 15% light ends (gasoline, aromatics)
~ 5 - 15% diesel, kerosene
~ 10 - 80% long-chain hydrocarbons (base lube oils)
~ 5 – 30% residual solids and asphaltenes.


Q: What is base oil end-product yield and by-products from your process??

A: The end-product yield depends upon the used oil feed characteristics and consistency. Based on a typical used motor oil feed containing about 5% water, the typical output can be


  • 77% (aggregate) Base Oils ( SN 150, SN 300 & SN 400/500)
  • 4% Diesel, Naphtha & Light Oil
  • 14% of residue (Asphalt) (Asphalt Viscosity @ 30°C, min > 1000cst)
  • 4% water
  • 1% process losses
  • Fuel Oil consumption, max 5% of Used Lube Oil (0.05 lb per lb of Used Lube Oil)

Q: What plant sizes are offered?

A: Standard processing capacities offered by Thermopac range from 200 gallons/hour (1.5 MM gallons per year) to 2,500 gallons per hour (20 MM gallons per year). The standard design approach offers major cost advantages to our customers since the design and components are all standardized and well-known. If, however, the customer desires to have other processing capacities, we will be happy to work with you


Q: How much does it cost to build a plant?

The total cost depends upon a number of factors, such as the plant capacity, desired product (Gr I or Gr II base oils), the availability of existing infrastructure, etc. If an existing waste oil collector decides to build a re-refinery then his costs will be much lower since he will have a lot of the off-sites such as tanks already in place. Costs are very site specific.


Q: What services does Thermopac offer?

A: Thermopac can deliver Engineering Services in addition to Turn-key Re-refining plants, Product Lube Blending and Oil De-Hydration equipment. For details of the services, please go to the Services tab of our website. You can engage our services for:


  • Feasibility Studies specific to your requirements
  • Data analysis and Technical evaluation of solution alternatives
  • Cost Estimations
  • Detailed Process Engineering
  • Complete Design Package
  • Operational troubleshooting
  • Revamping your existing plant

Q: How long does it take to build a plant?

A: After securing the necessary regulatory approvals and funding for the project, the plant could be operational in less than 10 months after award of contract to IES-Thermopac. Provided that 100% of funding is in place and advance payment is made by the client along with the purchase order, and client approvals are received on expedited basis, the plant can be commissioned in 8 months.


Q: What plants have you delivered?

A: We have delivered six turn-key re-refining plants over the past 5 years and many more under construction.


Q: What are the operating costs for one of your plants?

A: Variable operating costs (excluding capital and feedstock cost) are


  • Electricity
  • Makeup cooling water
  • For API Group I product, Activated Clay replacement
  • For API Group II product, hydrogen costs, if hydrogen is procured in tanks and not generated onsite
  • Fuel costs (IF light hydrocarbons and gasoil generated in Stage I cannot be used in the plant due to environmental regulations)

Q: How many people does it take to operate one of your plants?

Thermopac Used Oil Re-refining plants are highly automated due to its PLC SCADA-based computerized operation and process control. It takes about 3-4 full-time operations staff per shift for operations and maintenance.


Q: What are the most important considerations in having a successful re-refining plant?

The most important factor is to have a reliable supply of used oil and a guaranteed market for the re-refined products. A consistent quality of the used oil would result in smoother operations which helps minimize process spikes and lower the operational costs.


Q: How much does used oil feed cost and what is the value of your products?

A: The US Energy Information Administration (www.eia.doe.gov) maintains an active database of the prices of various oil grades, including the virgin Group I and Group II base lube oils, which may be used as a reference.
With respect to the used lube oil prices, there are tremendous variations. In the USA, a collector is generally able to secure oil at less than $0.50 / gallon, or sometimes lower. Some used oil generators may actually pay the oil collector to have the oil removed. Re-refining faces competition for the used lube oil feedstock from businesses who utilize the used oil as fuel, although that is not the best use of the used lube oil from an overall environmental or energy utilization perspective. The best disposition for used motor oil is re-refining back to its original condition.


Q: How many planned shutdowns are required?

A: If the feed quality variations are within the acceptable range of design process parameters, the plant typically operates without interruption


Q: What are the by-products of your process?

A: There are no major by-product wastes from the oil because the major contaminants exit with the asphalt flux. This material has been determined to be non-hazardous by the U.S. EPA. The heavy metals included in the additives do not leach from the asphalt. Typically, a small quantity of solids (foreign matter in the oil such as rags, debris, dust, metal particulates, etc.) filtered from the oil in pre-treating step are collected during the annual maintenance, are placed in drums and sent to a hazardous waste processing facility. The quantity is dependent on the type of Used oil feed, but generally small


Q: What are the plant emissions and what pollution control measures are used?

A: Pollution control equipment for gaseous emissions and Water Treatment for the waste water generated in the process as part of feed oil dehydration step are standard offering. However depending upon local requirements customer has to add thermal oxidizer and water treatment.