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Waste Solvent Recovery

INTRODUCTION


Any industry using solvents has the potential of recovering waste solvent in-house, resulting in increased profitability by reducing solvent purchases and eliminating or minimising waste disposal costs. Quantities as low as 50 litres a week have the potential for cost effective recovery employing in-house equipment.


As a direct result of these benefits, solvent recovery operations, predominantly involving distillation, have become increasingly common in a wide range of occupancies such as printers, GRP moulders, electronics manufacture and, in the engineering and motor trades, for the recovery of cleaning solvents and other solvent based materials. In response to increased demand, a considerable range of modular solvent recovery equipment is manufactured for batch or continuous, automatically filled operation of capacities upwards of 10 litres, supplied off the shelf, or designed to bespoke requirements. Equipment certified to ATEX Ex standards for Zone 1 hazardous area application is readily available, and recovery units will commonly employ electric heating via a diathermic oil. Steam heating may also be employed.


As well as being installed as a cost saving measure, for some businesses, solvent recovery plant will also play an essential key role in environmental management. 


Modular solvent recovery distillation equipment – load capacities between 60 –120 litres


Larger modular solvent recovery distillation equipment - load capacities up to 2200 litres


RISK ASSESSMENT AND CONTROL


In response to the increased presence of solvent recovery processes, the RISCAuthority has published RC52 – Recommendations for fire safety for waste solvent recovery plants, posted in ATLAS. This document addresses the hazards of large- and small-scale modular units of the distillation and carbon absorption types, but specifically excludes high volume distillation processes common to the petro-chemical industry.


The recommendations of this document are broadly addressed under the following headings:


  • Compliance with fire safety legislation

  • Business continuity

  • Fire safety management

  • VICES (Ventilation, Ignition, Containment, Exchange & Separation)

  • Operation

  • Fire protection

 

Key measures of RC52 include:


  1. The need to ensure that solvent recovery plants are a prominent feature of both fire and DSEAR risk assessments, to include addressing the implications of idle time, maintenance, routine servicing and cleaning.

  2. Identification and mitigation of ignition hazards associated with hot work and static electricity and ensuring that the equipment is ATEX Ex certified.

  3. Plant to be operated and maintained in strict accordance with the manufacturer’s instructions by suitably trained persons, and staff instructed on appropriate emergency procedures, including those for dealing with the safe recovery of solvent spillages. Minor leaks should not be tolerated and are to be effectively dealt with immediately they occur.

  4. The need for fire-rated separation of solvent recovery equipment based on a risk assessment. Distillation plant with a capacity greater than 20 litres and carbon absorber processes should be located in a detached building 10m from all other buildings and plant. Where this is not possible, the plant should be located in a designated fire compartment of at least 60min fire resistance.

  5. Distillation systems:


  • Tanks of waste and recovered solvents, together with the distillation vessel should be equipped with high and low liquid level monitors, linked to alarms and automatic safe shutdown.

  • Stills should incorporate high temperature sensors and cooling water flow/pressure alarms, linked to automatic isolation of the heat supply.

  1. Carbon absorption systems:

  • The effective monitoring of flammable vapours entering the absorber bed. The concentration of vapours should not exceed 25% of the lower flammable limit of the most volatile solvent present, or 50% where continuous gas detectors are in operation linked to automatic plant shutdown.

  • Suitable precautions taken to prevent auto-heating during extended shutdown periods.

  • The provisions of fixed water spay nozzles inside the absorbers over the carbon bed to wet down the bed in the event of overheating or fire. 

7.     The installation of automatic fixed fire suppression systems, especially in circumstances where the plant is in unattended operation.

                                                          

SURVEY EXPECTATIONS


Consultants should be alert to the presence of solvent recovery processes. Where encountered in the field, these should be assessed on the basis of the guidance contained in RC52, details entered in the survey report and risk improvements raised, as appropriate.


Appended to RC52 is a recommended checklist which Consultants may wish to follow.

 

ADDITIONAL INFORMATION


Websites providing information on solvent recovery equipment include:


Maratek  – https://www.maratek.com/solvent-recycling-recovery 

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