The 5 most essential aspects of the design of any anaerobic digestion plant can be listed as:
1. A High Degree of FlexibilityBiogas plants are complex even without consideration of the fact that the feed materials are waste products. They vary not only seasonally, but according to market forces and what the waste producer is doing in their business at any time. Not only that, as any biogas plant operator will tell you, it is necessary to feed the digester with the right mix of "woody" and "green" at all times.
If you perfer to view this on the YouTube website click here for this Xergi Biogas Top Design Success Factors video.
So, all biogas plant designs need to come with a huge dose of flexibility across just about any parameter that you consider. This is essential, when it comes to providing a plant which will be sufficiently adaptable to the clients needs throughout the lifetime of the biogas plant.
2. Dosing Equipment With The Ability To Handle All Types Of Feed MaterialsNo biogas plant can work well for long unless the operator is able to set the relative feed materials (substrate) proportions and overall input flows to what is needed for the good of the biomass in the digesters at any time, and for the equipment to reliably deliver that dose.
In most processes the input (raw material) is known (because it is bought-in to a specification). Waste deliveries to an AD Plant are the complete opposite. Nothing is the same for two days running when it is waste that is the raw material and is collected from the public and businesses.
This is a challenge for dosing equipment designers, and not all of them are up to scratch on the ability of their pre-treatment of waste arriving at the biogas plant to sort, mix, and break the material down into a transportable/ pump-able quantity of biogas plant feed accurately, and daily over long periods in-between maintenance dates.
3. Adopting an Ideal Process TemperatureThermophilic AD Plants provide optimum gas yields within the shortest period of time (average particle residence time in the reactor), so it is important for the economic benefit of the biogas project that the best rates of reaction are achieved, and by experience a company like Xergi is well versed in balancing demanding cost factors for choice the best process operating temperature.
4. High Efficiency MixingMixing demands are hard to meet in the fermentation process, as the mixture has a comparatively high viscosity, and fibrous materials can cause reduced equipment availability.
Within the biogas industry there are many ways to achieve biogas reactor mixing, some solutions are generic and have been around for many years. But, many of the best now, which are now avialable are compartaively cheap to run and provide the closest approximation to perfect mixing, are proprietory.
Xergi for example has its own in-house mixing technology to ensure that the mixing function is reliably available to provide something like the features of a fully-mixed reactor (fermenter).