Solvent recovery unit (solvent distillation)

01

Check boiling point and auto-ignition limits

Uni-ram's manual for its URS500 and URS600 recyclers states that the dirty solvent's boiling point must be below 200 °C and its auto-ignition temperature above 260 °C for safe operation, that the unit must not be installed where the auto-ignition temperature of the solvent or atmosphere is below 250 °C, and that nitrocellulose, which self-ignites at 135–166 °C, must never be recycled. The units are certified by ETL to UL 2208 and CSA C22.2 No. 30 and No. 88 for Class 1 Division 1 and Division 2, Group D locations. [1]

The manual advises estimating the operating set point as the pure solvent's boiling point from its safety data sheet plus 45 °C, and choosing the lowest of six set points (90, 115, 140, 165, 190 and 200 °C, factory set at 200 °C) that leaves about 500 ml in the tank; the mixture's boiling point rises as it gets dirtier. It heats the solvent directly by electricity with no heat-transfer oil, cuts power if tank, condenser or fan motor temperatures exceed a preset level or boiling starts late, and relieves tank pressure above 0.5–1.0 psi. It defines the area within 16 in behind and 10 ft at each side and front as Class 1 Division 2, Group D at most. [1]

Editorial calculation: a solvent whose pure boiling point is 100 °C would need about 100 + 45 = 145 °C, above the 140 °C step, so the 165 °C set point; the 200 °C maximum then covers pure solvents up to about 155 °C by the same rule. The boiling point is an assumed example. [1]

Give the supplier the solvent names and safety data sheets (boiling point, flash point, auto-ignition temperature), contaminants (paint, resin, oil, pigment), daily volume, hazardous-area classification of the installation site, cooling available (air or water), compressed air if a pneumatic vacuum is used, power supply, and how residues will be removed and disposed of.

02

Size the batch, the vacuum and the cycle time

Tieser's Distatic units, as listed by a distributor, boil solvent in a stainless steel vessel heated by a jacket of heat-transfer oil, with air- or water-cooled condensers and working capacities of 12, 25, 60 and 120 L. The DV 25 Ax model takes 25–30 L in a 40 L boiler, distils in about 3–4 hours, needs 3–7 hours to cool depending on operating temperature, draws about 2.04 kW at 230 V, and covers solvents of 50–200 °C (T2) or 50–180 °C (T3) with EEx od IIB T2 marking. [2]

All Tieser systems can take a vacuum unit, described as suited to solvents with very high boiling points or where boiling point and auto-ignition temperature are close; the pneumatic version needs dry, oil-free air at 6 bar or more and at least 450 L/min while building vacuum, and holds –0.5 to –0.7 bar. [2] OFRU's Compact vacuum distiller draws from a 200 L drum and reaches about 10–25 L/h depending on solvent and contamination, needing electrical control, cooling water and compressed air. [3] Uni-ram's units take 5 US gal (20 L), with a 1.5 gal (6 L) minimum. [1]

Editorial calculation: a 25–30 L batch that distils in 3–4 h and cools in 3–7 h takes about 6–11 h per cycle, roughly 2.3–5 L/h averaged over the cycle, so a single DV 25 unit handles about one batch per shift; a 200 L drum per day would need a continuous-feed unit like OFRU's at 10–25 L/h, taking about 8–20 h. [2] [3]

03

Consider a recycler built into the parts washer

Safety-Kleen's SystemOne "S" series combines a solvent parts-washer sink with on-site distillation, so the solvent is recycled in place rather than in a separate still. Its specification lists four sink sizes for maintenance, transmission, aircraft and heavy-equipment work, push-button on/off and recycle controls with LED diagnostics, and recycling either on demand or on a programmable 7-day/24-hour schedule. [4]

Editorial calculation: 115 V × 11.9 A is about 1.37 kW, below the 2.04 kW of the Tieser DV 25 Ax above. A 15 gal (about 57 L) distillation tank over a 4-hour recycle averages about 3.75 gal/h (about 14 L/h), and the 18 gal annual top-off is about 60% of one 30 gal pure-solvent reservoir. [4] [2]

An integrated washer recycles the solvent of its own sink; a separate batch still such as the Uni-ram or Tieser units above takes dirty solvent carried to it from wherever it is used. Ask either type of supplier for the boiling-point and auto-ignition limits of the solvent it accepts, the hazardous-area rating and the residue handling. [4] [1]

04

Low-boiling and explosion-proof recovery machines with vacuum add-ons

The listing reviewed offers solvent recovery machines for specific solvents, explosion-proof versions, vacuum pressure-reducing devices, recovery bags and heat-transfer oil; ask for the certification, temperature range and capacity of the model offered.

05

What boils, condenses, relieves and collects inside a solvent still

06

Your solvents and daily volume, translated into rate, temperature and enclosure figures

Each published value here belongs to one example unit from Uni-ram, Tieser or OFRU; ask for the same row on the model you are quoted.

07

Send the solvent, volume and site data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Solvents: [names; SDS; boiling point; auto-ignition temperature]
Contaminants: [paint; resin; oil; solids]
Volume: [litres per day; drum or batch]
Unit: [batch size; heating; vacuum]
Certification: [UL 2208; ATEX or Class/Division]
Site: [hazardous area; cooling; compressed air]
Residue: [liner bags; disposal]
Power: [voltage; plug]

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