– Follow four steps for a successful AD factory design


Author: Steven Cotterill, 3D CAD Designer for Anaergia UK

October 13, 2021

From developing a small-scale on-farm digester to a large biomethane facility, embarking on a new anaerobic digestion project can be a daunting prospect. A thorough design phase to determine the most successful layout for a site can reduce risk, ensuring your plant remains profitable for years to come. Here are the four cornerstones of Anaergia’s design to put your AD project on the path to success.

1. Follow the process

In a well-designed AD installation, the process dictates the positioning. As the site footprint allows, design your plant layout to follow the flow of material. This will allow the raw material to be pumped or transported the shortest distance possible, reducing the likelihood of downtime due to blockages and reducing wear and tear on feed equipment, process pumps, macerators and conveyors.

This design principle can be applied throughout the site. A compact layout is more cost effective, as a smaller footprint means less land, less concrete, and less labor will be needed to build the plant. However, be sure to allow enough space in your design for landscaping, planting, and shielding, which are often required by planners.

2. Allow easy access to equipment

Maintenance is vital to the proper functioning of the AD, so make sure that forklifts, small vehicles, or hoists can easily access key equipment such as tanks, pumps, and mixers. This will give service engineers the ability to remove, repair and, if necessary, replace parts and equipment quickly, reducing downtime.

Make sure high level equipment is easily accessible via steps or access ladders with sufficient platform to work, or that there is room for an aerial work platform or scissor lift . If the factory has a flexible membrane roof, you will also need to allow access to cranes, as the membrane life is shorter than the subsidized life of UK AD factories and it will need to be replaced.

Finally, consider DSEAR (Hazardous Substances and Explosive Atmospheres Regulations). Avoid installing equipment that will require regular maintenance in a DSEAR area, in order to reduce the time that operators will spend in this high-risk area.

3. Protect your people

The health and safety of operators and site visitors is paramount and, as noted above, full consideration of DSEAR and HAZOP (Hazard and Operability Study) should be followed. The potential for an explosive atmosphere increases near the pressure relief valves, as this is a final safety measure of the release of biogas if the torch does not ignite when the excess biogas is not consumed . Therefore, in addition to installing key process equipment away from ATEX zoned areas, try to avoid placing electrical equipment or instruments in the biogas discharge area. If this is not possible, ensure that the equipment or instrumentation is properly ATEX classified.

Establish clear routes for personnel throughout the facility. Inside the reception building, set up designated walkways for operators, as well as barriers and / or handrails to protect people from overturning vehicles and bucket loaders. Arrange process pumps and associated piping away from walkways to avoid tripping hazards and consider placing piping and electrical cables above head height on support frames to keep floors clear of access .

Take into account the maximum number of people who can be on site at any one time and ensure that adequate facilities are available. In the unlikely event that operators come into contact with large amounts of digestate or raw material, it is important to ensure that the site has good washing facilities and toilets in clean and dirty areas. Showers, changing rooms, laundry rooms and a mess hall of sufficient size for operators and contractors are also essential.

4. Take care of the transport

When designing your AD installation, consider the movement of vehicles inside and outside the site, as well as within the site boundaries. A traffic management plan is a good starting point and depending on the number of vehicles expected at the site, a traffic light system may also be required.

Position the weighbridge as close to the operations office as possible to allow effective communication between drivers and site personnel. If the weighbridge needs to be located further away, make sure there is a working automated ticketing system.

Make sure there is enough space to turn and back for vehicles delivering raw material or collecting digestate. If delivery vehicles tip over in a receiving building, the building must be high enough to accommodate the bulk trailer at full tipping height.

Plan enough parking spaces to accommodate all staff and contractors and locate parking lots as close as possible to reception. This will ensure that new staff arriving on site can easily and safely make their way to reception before registering and being inducted.

Finally, make sure that the size of the breakwater is adequate (110% of the largest vessel or 25% of the total tank volume, whichever is greater) and that vehicles can easily access it, either via a ramp or flood valve.

To conclude, a complete site design paired with strong 2D and 3D concept illustrations can help developers visualize their proposed DA plant and correct any potential layout issues before construction begins, saving money. time and money. For expert advice on AD design and layout, contact [email protected]

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Leon E. Hill