What occurs to your recycled used oil?
Pre-treatment or Dewatering
Filtering & Demineralisation
Propane De-asphalting
Distillation
What happens to your recycled used oil?
Used oil, or ‘sump oil’ as it is generally called, shouldn’t be thrown away. Though it will get soiled, used oil may be cleaned of contaminants so it may be recycled repeatedly. There are many uses for recycled used oil.
These include:
– Industrial burner oil, where the used oil is dewatered, filtered and demineralised to be used in industrial burners;
– Mould oil to assist launch merchandise from their moulds (e.g. pressed steel products, concrete);
– Hydraulic oil;
– Bitumen based mostly merchandise;
– An additive in manufactured products; or
– Re-refined base oil to be used as a lubricant, hydraulic or transformer oil.
After getting taken your used oil to your native collection facility, used oil collectors take the used oil and undertake some pre-treatment and recycling of the used oil or promote it to a specialised used oil recycler.
Pre-therapy or Dewatering
Pre-therapy of used oil entails removing any water inside the oil, referred to as dewatering. A method of doing that is by putting it in giant settling tanks, which separates the oil and water.
Further recycling steps include:
Filtering & demineralisation of the oil, to take away any solids, inorganic material and certain additives current within the oil, producing a cleaner burner gas or feed oil for additional refining;
Propane de-asphalting to remove the heavier bituminous fractions, producing re-refined base oil; and
Distillation to provide re-refined base oil appropriate for use as a lubricant, hydraulic or transformer oil. This course of could be very similar to the method undergone by virgin oil.
Water is present in used oil as free water or bound water, for instance in emulsions. The time period dewatering is often taken to imply the removal of free water. Where water has been emulsified with oil, the emulsion must be “broken” with a demulsifier before the water could be separated from the oil.
Dewatering is an easy process counting on the separation of aqueous and oil phases over time below the affect of gravity. The used oil is allowed to stand in a tank (uncooked waste oil) and free water drops to the bottom the place it can be drained, treated (waste water treatment) and discharged appropriately to sewer or stormwater relying on quality and native laws.
Heating and stirring the used oil in a tank (A) and driving off the water by means of evaporation can pace up the dewatering process.
The “dried” or dehydrated oil is then appropriate for further processing or to be used as a burner gas.
Filtering & Demineralisation
The aim of filtering and demineralisation is to take away inorganic materials and certain additives from used oil to supply a cleaner burner gas or feed for re-refining.
Used oil feedstock is transferred to a response tank (A) and blended with a small quantity of sulphuric acid and heated to about 60oC. A chemical surface-lively reagent, referred to as a surfactant, is added to the reactor (A) and after stirring the mixture is allowed to face. This allows the mixture to separate into two “phases” – i.e. oil and water-based mostly or aqueous. The reagent causes the contaminants to accumulate in the aqueous phase, which settles to the underside of the tank (A) and is drained off as slurry. This phase comprises acid, used oil contaminants, including metals and among the oil additives. The water is dried off, leaving a solid waste that must be disposed of. It may be additional diluted or “reduce” with a lighter petroleum product (called cutter stock) to produce a range of intermediate to light gas oils depending on the gas viscosity requirements of the burner.
Propane De-asphalting
The Propane De-asphalting (PDA) course of is a crucial pre-remedy step within the re-refining process producing de-asphalted lube-oil, which turns into a feedstock for the next step in a re-refining facility. The opposite output (which is also an enter) is propane, which is recovered from both streams and re-used within the process.
The PDA course of relies on the better solubility of the paraffinic and naphthenic (ie primarily the bottom oil) parts versus the contaminated waste materials in a stream of propane.
The separation of the lubricating oil fraction from used oil is a continuous course of and is performed at ambient temperature when processing used oil.
The used oil is pumped into the middle of the extraction column (A). Liquid propane is charged to the underside of the column (A). The oil being heavier than propane, flows down the column (A); the propane rises in a counter-circulation thus mixing the enter streams inside the column (A). The rising propane dissolves the extra soluble lube oil elements, which are carried out the highest of the column (A) with the propane, and the propane insoluble materials is removed from the underside of the column (A).
Propane is vaporised from each streams [ie.
The de-asphalted lube-oil part is feed for the following processing stage. The residuum (waste) component is blended with bottoms from the vacuum distillation tower to provide an asphaltic material.
Distillation (or Fractionation) is the physical separation of parts of lubricating oil by boiling range. Relying on the kind of distillation, the boiling ranges can produce gases and gasolines on the decrease boiling points with heavy lubricating oils being distilled at greater boiling factors. Distillation is the core course of for a facility able to producing re-refined base-oils to virgin base-oil quality.
There are 2 forms of distillation, atmospheric and vacuum.
Atmospheric Distillation
Atmospheric distillation is usually (but not at all times) thought-about a pre-remedy step for vacuum distillation and does not require de-watered feedstock. Atmospheric distillation is carried out at normal atmospheric stress and with temperatures as much as 300°C.
Previous to the atmospheric distillation course of, the feedstock can have undergone PDA remedy, but this isn’t an absolute pre-requisite.
Atmospheric distillation is a comparatively simple course of separating lower boiling point liquids at ambient pressure. Used oil is heated (A) and charged to a distillation tower (B). Lower boiling point hydrocarbons present in the used oil (eg gases, petrol and solvents) and water are collected at the top of the tower (B). Some of these hydrocarbons will be condensed and collected for use as a gas in the refining process.
This course of is simply appropriate for temperatures up to 300oC, as temperatures above this can result in “thermal cracking” of the larger molecule (larger boiling point) hydrocarbons, ie. the actual lube oil molecules we are aiming to get well.
After atmospheric distillation the oil often undergoes vacuum distillation. Notice that used oil could be despatched straight from a “drying” course of to a vacuum distillation unit without necessarily undergoing atmospheric distillation. However, it is generally accepted that water and decrease boiling level hydrocarbon elements be removed previous to vacuum distillation.
Vacuum Distillation
Vacuum distillation is considered the important thing process in used oil re-refining. If atmospheric distillation is utilised, the oil from the atmospheric distillation column is the feedstock for the vacuum distillation column. In vacuum distillation the feedstock will be separated into products of related boiling range to higher management the physical properties of the lube base inventory “distillate cuts” that will likely be produced from the vacuum tower merchandise.
The main properties which are controlled by vacuum distillation are viscosity, flash level and carbon residue. The viscosity of the lube-oil base-inventory is set by the viscosity of the distillate by way of its relative viscosity separation, eg. light, medium and heavy oil.
The used oil feedstock (normally from the atmospheric distillation unit) is heated in a furnace (A) and flows as a mixture of liquid and vapour to the heated vacuum distillation column (B) where the vapour portion begins to rise and the liquid falls. Steam may be added to assist vaporisation.
A vacuum is maintained in the column (2-10 mm Hg) by a vacuum system connected to the top of the tower (B). Petroleum Refinery By decreasing the pressure, supplies normally boiling at up to about 540oC at atmospheric stress, will be vaporised without thermal cracking.
As the new vapours rise by the column (B), they cool and a few condense to a liquid and circulation back down the column. Similarly, a number of the downward flowing liquids are re-vaporised by contacting the rising hot vapours. Special devices in the column permit this upward move of vapours and downwards stream of liquids to happen repeatedly.
At varied points in the column (B), special trays, called draw trays, are put in which permit the removal of the liquid from the column. If three cuts or “fractions” of oil are required to provide mild, medium and heavy base stocks, then three draw trays are positioned appropriately. This can be reduced to 2 draw trays if, for instance, only 2 cuts or fractions are required.
A few of the material does not boil even under this vacuum. This remains in the vacuum tower and is run out because the vacuum tower bottoms (VTBs). This material comprises the heaviest molecules, including some lube oil additives and carryover contaminants not removed in the PDA course of. (Note: not all re-refining plants have PDA models).
