When it comes to pulp processing investors typically consider two options: biogas or pulp drying.
How is a biogas plant more practical than drying? First, it does not consume but instead produces energy. And revenues from energy sales are guaranteed by a long-term Power Purchase Agreement with the Government or Energy company. No marketing expenses.
Second, dried pulp competes with grain as animal feed. If there is an overproduction of grain on the market, then the price of dried beet pulp falls. In the best case scenario, it will be possible to only cover the costs of production.
Biogas plants operating on different types of pulp are structurally different.
Primary pressed pulp can only be fed through a receiving tank by means of a pump. Half-pressed and deep-pressed pulp is fed from the loader by augers or by special pumps bio-mix. Substrate from the reactor is used for dilution in the bio-mix.
The primary-pressed and half-pressed pulp are stored in open storage and are usually heavily contaminated with stones, sticks, and even tires.
So contaminants are allowed to precipitate out in a pre-tank and are periodically removed. Plants themselves have a minimal set of equipment that does not require constant maintenance.
We at NGE Biogas have built biogas plants for 5 sugar mills producing various pulp types and using technologies optimized for each specific situation.
The biggest biogas plant at a sugar mill we did was 7,5 MW biogas at Korsun. The best biogas practice is here. Deep-pressed pulp 400 tonnes daily 25% DM is quite clean and stored in a concrete storage. The applied technology is vertical steel reactors with a central agitator. Substrate is input by a solid feeder with a live floor and pumped by bio-mix. The plant has maximum efficiency. Pulp is fermented as completely as possible. In the case, the biogas plant has the best payback time.
The first two types of pulp are usually stored in open lagoons. Pulp is sour (pH3) and loses some of its organic matter. Sugar beet pulp from open lagoons has a disadvantage - high moisture. When it enters a biogas reactor, water occupies usable reactor volume. The volume is calculated for a hydraulic retention time of 25-28 days. Therefore, construction of large volume reactors for liquid pulp is recommended.
Deep-pressed pulp is stored in reinforced concrete silage storage. In such storage, maize silage is usually stored.
Pulp is input by front loaders, rammed, and covered with a film. For maximum storage, loaders are equipped with an arm extension.