Technology
Semi-Continuous Used-Oil Re-Refining Plants
Batch flexibility. Continuous WFE performance.
Overview
Balaji Consultants designs and supplies semi-continuous used-oil re-refining plants that combine the operational flexibility of batch feed preparation with the higher throughput and process stability of continuously operating Wiped Film Evaporators (WFEs). In the Balaji semi-continuous configuration, dehydration and degassing are carried out in batch vessels. Once the feed has been properly conditioned, the dehydrated and degassed oil is transferred to a buffer tank, which provides a steady and controlled feed to the downstream continuous section. From the buffer tank, the oil is pumped through a preheater and then fed continuously to one or more WFEs.
This arrangement combines the ability to handle variable used-oil feedstocks in controlled batches with the process efficiency, short residence time and continuous characteristics of WFE technology. Semi-continuous re-refining is particularly attractive where the operator requires higher throughput than a conventional batch distillation system can conveniently provide, but still values the flexibility of batch dehydration and feed conditioning.
The technology is also well suited for revamping and upgrading existing batch re-refining plants, where the existing dehydration equipment can often be retained while WFE technology is added downstream to improve recovery, throughput and overall process continuity.
How It Works
1
Batch Feed Preparation, Dehydration & Degassing
A measured quantity of used lubricating oil is charged into the dehydration and degassing vessel. Depending on the feed quality, preliminary settling or coarse filtration may be carried out before charging to remove gross solids, sludge and free water. The oil is heated under controlled vacuum conditions to remove free and dissolved water, entrained gases, low-boiling hydrocarbons and other volatile contaminants; the vapours are condensed and collected separately. Effective dehydration and degassing are essential because water and volatile contaminants can destabilise the deep-vacuum conditions required in the WFE section. Once the required feed condition has been achieved, the treated oil is transferred to a buffer tank.
2
Buffer Storage & Continuous Feed Control
The dehydrated and degassed oil is collected in an intermediate buffer tank, which performs an important process function by separating the batch front-end operation from the continuously operating WFE section. While one dehydration batch is being processed, previously conditioned oil can continue feeding the WFE section, allowing it to operate at a substantially steady flow rate despite the batch nature of the upstream dehydration stage. The buffer system, while providing stable feed rate, improved operating continuity, reduced process fluctuations and flexibility to handle variable feed batches.
3
Feed Preheating
Oil from the buffer tank is pumped continuously through a feed preheater before entering the WFE section. The preheater raises the feed to the required process temperature, reduces the thermal duty inside the WFE and helps maintain stable evaporation conditions. Depending on the plant configuration, heat may be supplied through thermic fluid, steam, heat recovery from process streams or a combination of available heating systems. Proper feed preheating improves WFE throughput and reduces unnecessary thermal loading on the evaporation surface.
4
Continuous Wiped Film Evaporation
The preheated oil is continuously fed into the Wiped Film Evaporator, where a rotating wiper system distributes the oil as a thin film over the heated evaporation surface. The combination of thin-film heating, forced vacuum, continuous surface renewal and short residence time allows valuable base-oil fractions to be recovered at significantly lower bulk temperatures than would be required under atmospheric conditions, minimising thermal cracking, product discolouration, coke formation and degradation of the base-oil molecules. The heavier non-volatile material progressively concentrates and exits from the WFE residue outlet continuously.
5
Base Oil Recovery & Product Collection
The WFE configuration is selected according to the required product slate. Where a single combined base-oil fraction is required, one WFE separates the recoverable distillate from the heavy residue. Where base-oil fractions are required, one or more WFEs may be used — the first recovering the lighter lube-oil fraction, subsequent WFEs operating at different temperature and vacuum conditions to recover progressively heavier fractions. The vapours generated in each WFE are condensed and collected in dedicated product receivers or intermediate storage tanks, and the recovered distillates are monitored for viscosity, colour, flash point and density.
6
Residue Recovery & Handling
The non-volatile fraction leaving the final WFE — containing heavy degraded hydrocarbons, carbonaceous material, additive-derived contaminants, metals, ash, asphaltic components and other high-boiling non-distillable material — is continuously discharged to the designated residue storage or downstream handling system. Continuous residue discharge avoids the repeated vessel-emptying cycle associated with conventional batch distillation and contributes significantly to improved plant throughput.
7
Base Oil Finishing
The recovered base-oil distillates are subsequently processed through the appropriate finishing technology depending on the desired product specification. Available finishing options include regenerative clay polishing, conventional clay treatment, solvent extraction or other product-specific finishing systems. The finishing section can itself operate continuously or semi-continuously depending on the selected technology and plant capacity.
Key Equipment
Batch dehydration and degassing vessel with heating system
Dehydration condenser, water and light-hydrocarbon receivers
Dehydrated-oil buffer tank
Continuous feed pump and feed preheater
One or more Wiped Film Evaporators (WFEs)
Deep-vacuum system
Distillate condensers, product receivers and intermediate base-oil storage tanks
Residue receiver and storage
Base-oil finishing system (regenerative clay polishing, clay treatment or solvent extraction)
Thermic-fluid heating system and cooling-water system
Instrumentation and PLC/SCADA controls
Process Configurations
A
Batch Dehydration + Single WFE
A batch dehydration and degassing vessel feeds conditioned oil to a buffer tank; from the buffer tank the oil is continuously preheated and processed through a single WFE to recover one combined base-oil fraction. Suitable where one principal base-oil cut is required, simpler operation is preferred and the feedstock does not require multiple lube-oil cuts.
B
Batch Dehydration + Multiple WFEs
Dehydrated and degassed oil is transferred to the buffer tank and then continuously processed through two or more WFEs, each operating at a different temperature and vacuum condition to recover progressively heavier base-oil fractions. Suitable where multiple base-oil cuts are required, higher overall recovery is targeted and product segregation by viscosity range is commercially valuable.
C
Existing Batch Plant + WFE Retrofit
An existing batch re-refining facility is upgraded by retaining the existing dehydration and degassing section and adding buffer storage, feed preheating, WFE systems, vacuum equipment, condensation systems and product and residue handling. Allows the plant to move from conventional batch distillation toward a semi-continuous WFE-based process without replacing the complete facility — particularly attractive for brownfield modernisation and capacity expansion.
Selection Considerations
- Retains batch flexibility for variable used-oil feedstocks while adding continuous WFE separation
- Higher throughput and shorter thermal residence time than conventional batch distillation
- Lower risk of thermal degradation and improved base-oil recovery
- Continuous residue discharge and stable downstream operating conditions
- Easy integration into existing batch re-refining plants — ideal for phased plant modernisation
- Configurable for one or multiple base-oil cuts depending on market requirements
- Reduces dependence on large batch distillation vessels
Frequently Asked Questions
The semi-continuous configuration combines batch dehydration and degassing with continuous Wiped Film Evaporation. A buffer tank separates the batch front-end from the continuously operating WFE section, allowing the evaporation system to maintain a substantially steady feed rate while the upstream dehydration process handles variable batches.
Yes. Existing batch facilities can often be upgraded by retaining the existing dehydration and degassing equipment and adding a buffer tank, continuous feed system, preheater, WFE equipment, vacuum system, condensers and suitable product and residue handling systems. This can provide a practical route for brownfield modernisation and capacity expansion.
Yes. Multiple WFEs can be configured in series with different temperature and vacuum operating conditions to progressively recover lighter and heavier base-oil fractions. The exact configuration depends on feedstock properties, required product grades, target recovery and commercial requirements.
See It in Operation
Commissioned projects where this technology is part of the installed plant.
24 KLPD Semi-Continuous WFE Revamp — BangladeshRelated Technologies
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