PreMix®: Optimizes solids treatment and increases gas production
Case study: Ronconi Giacomo biogas plant, Italy
Problem
High maintenance costs and disruptions caused by long-fiber solids in the fermenter.
Solution
PreMix reliably comminutes, homogenizes, and conveys solids into the fermenter.
The customer and the problem
An Italian agricultural business with around 130,000 pigs and 2,000 dairy cows operates two biogas plants, each with a capacity of 1 MW. Both plants are fed with the same input materials: slurry, cattle manure, process water from the farm, and a small amount of silage.
The two biogas plants differ fundamentally in their feeding systems. In the first plant, a vertical mixer with a screw conveyor ensures that the solids are fed directly into the fermenter. However, this system led to frequent problems: the fermenter had to be opened almost monthly to remove ropes, fibers, or straw. The workload was high, malfunctions occurred regularly, and the agitators required a lot of energy because long-fiber materials had to be processed. In addition, floating and sinking layers formed, which impaired the gas yield.
The solution
For the second plant, operator Giovanni Ronconi opted for the Vogelsang PreMix. A screw conveyor feeds the solids directly into the PreMix. There, they are shredded in a single step, foreign matter is separated out, and they are mixed with fermentation substrate or slurry to form a homogeneous suspension before being fed into the fermenter.
After more than two years of operation, Ronconi was able to compare the two systems in detail. The system with PreMix impresses with less work, fewer malfunctions, and greater process stability. While the fermenter had to be cleaned regularly with the vertical mixer, this was not necessary at all with PreMix. Maintenance is minimal – so far, only the cutter and screen of the shredder have had to be replaced, while the pump itself has continued to run without any problems. In addition, the liquid feeding system prevents the formation of floating and sinking layers and contributes to a better gas yield. This reduces the amount of input materials without affecting daily production output. Both the PreMix itself and the downstream agitators require significantly less energy, as long-fiber materials no longer need to be processed.
Advantages
- Homogenization of the biomass by mixing it with liquid to form a suspension that is optimal for bacteria
- Shredding of fibrous impurities and separation of heavy materials in a single step
- Simple and fast service directly on site
Benefits for the user
- Significantly lower personnel costs for the maintenance of fermenters and agitators
- Prevention of stratification in the fermenter
- Lower energy consumption of the feeding system and agitators
- Less feedstock required while maintaining the same gas production
