In Anaerobic Digestion the process design is critical to how the plant operates. Incorrect design can lead to the flow of material being improperly treated or the digester can start to inhibit biogas production. This is why every step of the process is essential to get right by the system designer.
Commonly a plant will be designed in two main parts. These are the biogas production part and the energy generation element. Within these two main categories come different sub sections that make the process tick. For example, pre- and post-treatment and the digester itself.
Process Design Considerations
There are many different things to take into consideration when design an Anaerobic Digestion plant.
Site Location – Considering where the site is located is the first step. The process designer needs to ensure that there is sufficient access and egress. This is dependent on the type of license the site holds and whether it is a central location with resources being brought in often during the day. Potentially creating traffic and other hazards. This would obviously need permission from the local council.
Normal Weather Conditions – Weather conditions can have an effect on how the system gets designed. It can also affect the materials used. An AD plant that sits in direct sunlight all day will be different to that which faces cold weather, rain and winds constantly.
Layout – Site layout is probably the most important aspect of design. From deciding the layout of process equipment and instrumentation to assessing the flow of medium throughout the process. If the site layout is incorrect or not as good as it could be then the end user will either find the process difficult to manage or their outputs from the process will be significantly reduced.
Capacity – The need for identifying capacity is essential in process design. There is no point designing and building a plant and holding tanks that can handle 10 tonnes, yet the feedstock being delivered to site is well in excess of that. A plant must be designed per population or the amount of feedstock coming in. In addition to this, the same is also true for post-treatment. It would be inefficient if there wasn’t the capacity to handle the digestate after it has been in the digester. This also applies to energy generation too.
Access & Lifting – Having the required access around process equipment for maintenance purposes is essential. If a plant is designed with insufficient space and no lifting davits or even enough space to set up a portable lifting frame then any maintenance will become extremely difficult.
