Handling chemical waste

Author : Rob Vesty, customer services manager for Pyroban’s Safe Handling Division

30 November 2010

Chemical waste from chemical, pharmaceutical and other manufacturing industries can either be destroyed or recycled by specialist waste management companies. In both cases, waste in the form of gases, solids (powders, pastes, pills, resins) or liquids (solvent, slurries, highly toxic) may arrive at a specialist waste management plant in palletised drums, IBCs or in bulk liquid tankers, containing a mix of different solvents or chemicals.

On arrival at a site, all deliveries are typically sampled by scientists and then batched or blended into compatible types for processing. In some cases, finite destruction of waste is often necessary in high temperature incineration processes. Alternatively, companies are able to recover and recycle material, such as flammable solvents, for resale as high quality recovered solvent or for other uses. Even the drums can be recycled.

Explosion proof materials handling equipment

Chemical waste management businesses rely on the continuous movement of flammable material and materials handling equipment feeds the process from delivery and storage through to the processing areas.

Curtain sided trailers may arrive at a site containing drums (up to 80) or IBCs, most of which contain flammable materials. 2.5-3 tonne fork lifts may be used to unload the trailers and position the drums and IBCs in the zone 2 storage areas. A further fleet of 2.5-3 tonne trucks may then feed the process areas in batches where containers are vented and then conveyed into the process.

Correct area classification is critical so that the materials handling equipment can be supplied according to the ATEX 94/9/EC directive and EPS 1996 regulations.

It is important that businesses are aware of which Ex system options are available at the time of issuing specifications to the various forklift suppliers. It has been found that the most common need in the waste management sector is to protect materials handling equipment for operation within Zone 2 classified areas.

Materials handling in Zone 2
The typical solution offered by Pyroban in waste management sites will be System 6000 gas protection which will often be used to protect diesel powered 2.5-3t forklift trucks including those with turbo charged engines and increasingly complex electronic truck management and control systems.

System 6000 was introduced to the market in November 2010 and supersedes Pyroban’s award winning system 5000 with new software and new hardware. It combines gas detection and automatic shutdown with various explosion protection methods such as restricted breathing enclosures, stainless steel cladding of forks, surface temperature limitation to ensure the engine, motors, brakes, electrics and other components remain below the auto-ignition temperatures of flammable materials, typically 135°C in the waste management industry. On diesel equipment, Pyroban also fits an inlet valve to prevent engine overspeed and any flame reaching the atmosphere if the engine were to ingest a gas or vapour.

When a mixture of flammable gas or vapour in air is detected, System 6000 gives an audible and visual warning at 10% Lower Explosive Limit (LEL - propane in air) and at 25% LEL it shuts down the protected equipment, automatically eliminating the risk of an explosion.
One important new element of System 6000 is that there is now a choice between infrared or pellistor gas sensing technology to continuously monitor the direct environment around the protected equipment and to automatically shut down the equipment before the atmosphere becomes explosive. The choice of gas sensing head is dictated by the application, risk and the science applied so waste management sites should seek advice as to which technology suits their particular operation.

System 6000 is ATEX 94/9/EC compliant and based on the harmonised European standard for industrial trucks to be used in potentially explosive atmospheres EN1755:2000+A1:2009. System 6000’s gas detection system is offered with IECEx certification to IEC 60079 standards and can be integrated with the latest technologies seen in engine and battery electric truck design particularly VNA, pallet, picking, reach and counterbalance truck designs. It was also developed to work with other types of mobile equipment such as cranes, tow tractors, sweepers and access platforms.

The gas detection system auto-calibrates and self-tests the gas head at start up to ensure it is working correctly, an essential safety requirement when complying with EN 1755:2000+A1:2009. This auto-calibration function obviates the need for periodic and costly site visits by engineers having to recalibrate the gas detection system as required by other systems on the market. It also removes the risk that the gas detection system could be operating out of calibration for significant periods of operation.

As an alternative in zone 2, Pyroban can also provide passive solutions, similar to the zone 1 solutions seen below.

Materials handling in Zone 1
Diesel powered equipment is sometimes required to operate in zone 1 areas in waste management sites requiring the Euromech 2G modification. This is a more conventional conversion which includes explosion proof Ex’d’ enclosures for arcing and sparking components, surface temperature limitation to ensure the engine, motors, brakes, electrics and other components remain below the auto-ignition temperatures (T Class) of flammable materials. The Pyroban system includes an inlet shutdown valve for automatic and manual shutdown and a water cooled exhaust gas cooler to limit surface and exhaust temperatures, stainless steel cladding of forks, frame leakage monitoring, Ex’e’ motors, Ex’i’ intrinsically safe circuitry, Ex’m’ encapsulation and an Ex’e’ battery.

Electric trucks made explosion proof would have similar passive protection although Pyroban reports that the use of electric trucks is less common in waste management facilities. If powders are handled, Pyroban can also provide a suitable passive solution in combination with explosion protection for equipment working within zone 1 or zone 2 areas.

Reliability and lifetime safety
Regardless of the type of protection, materials handling equipment is often required around the clock in intense and demanding waste operations, particularly if an incinerator needs to be fed continuously on a waste management site. Pyroban conversions maintain the performance characteristics of the original vehicle and can be matched to suit the intensity of the operation from the very beginning.

Finally it is essential to keep explosion proof forklifts and similar equipment explosion proof from the point of delivery to site to the point of eventual replacement. Following planned maintenance schedules and using engineers who are certified and experienced on the Pyroban system is essential. Pyroban also recommends EX-ASA annual safety audits in accordance with EN 60079:17:2007. The audit is carried out by a Pyroban inspector and examines the safety system in detail with thorough inspection of all safety critical components.