automatically-fed digester system
Temperature and mixing can be effectively manipulated in lab-scale reactors. However, the manual feeding regime prevalent for “semi-continuous” lab-scale digesters detracts significantly from full-scale operation. Most full-scale AD plants feed on an hourly or two-hourly basis, and the performance and microbiology will reflect that. Feeding less regularly has been found to contribute to instability (transient increase in CO2 content of biogas and VFA increase in the liquid). On the other hand, at full-scale, each feeding “batch” takes several minutes to be pumped into a digester adding to up to 6 hours of feed pumping each day. The result is that the process is not shock-loaded by large bursts of feed and biogas production is more stable than when feed is delivered less regularly.
The automatically fed digesters developed by Anaero Technology enable research with real feedstock that closely reflect the operational conditions of real AD plant, enabling advanced and representative research.
Lobster CSTR model
Auto-fed digester with 6 reactors. This is the standard Lobster model. Six 2-litre digesters on two beams, offering two volumetric feeding rates, i.e. each beam automatically feeding three digesters.
* it includes GASFLOWMETER and PLC controller
Auto-fed digester with 4 reactors. Four 2 or 5-litre digesters on four beams, offering four volumetric feeding rates, i.e. each beam automatically feeding each single digester.
The 'i' version is similar to the standard Lobster model, but its digesters are fed independently.
Auto-fed digester with 6 reactors. Six 5-litre digesters on two beams, offering two volumetric feeding rates, i.e. each beam automatically feeding three digesters.
The 'max' version is similar to the standard Lobster model, but with a larger digester volume of 5L.
Auto-fed digester with 4 reactors. Four 5-litre digesters on four beams, offering four volumetric feeding rates, i.e. each beam automatically feeding each single digester.
The 'max-i' version is a combination of the Lobster's models, with digesters of 5L volumes and independent feeding.
* all CSTR systems includes GASFLOWMETER and PLC controller
Anaero Technology’s lab-scale anaerobic digestion research bioreactors are capable of automatically feeding heterogeneous feedstock, as used in full-scale AD operation. This system provides high quality replication of full-scale AD processes, from feed storage, to digestate capture in a gas-tight set (feeder, digester, digestatetank, gas flow meter) that allows efficient mass balances.
All CSTR sets counts with a Gasflowmeter, where the gas generation is measured using a liquid displacement gas flow meter.
The gas flow meter is a single Perspex block with 15- 0.2l cells and Perspex tumbling buckets of around 7ml gas volume. A spare cell (cell 16) is used for automatic monitoring of temperature. A barometer in the Arduino logger continuously monitors atmospheric pressure for STP correction. The liquid in all cells is interconnected to keep them at exactly the same head, for equal head pressure in all reactors (liquid specifications: Table 2). Each cell has a tumbling bucket with active volume of around 7ml (easily calibrated by user- See section 3.1). The smaller measuring volume allows for better recording of the kinetics of the test, especially after the initial phase of high gas production. However, the smaller the measurement volume, the larger the potential error from uncounted gas bubbles. To minimise potential error during gas measurement a minimum counting volume of 5ml has been designed and attention has been paid to the size of gas bubbles entering the measuring vessel. The diameter of the nozzle orifice where gas enters the measurement cell is machined to 1.5mm, reducing the size of gas bubbles and minimising the potential impact of uncounted odd bubbles by-passing the tumbling bucket.
Other CSTR models
Touchscreen PLC controller is required for each CSTR system installation. The PLC includes bespoke control and monitoring software for the mixing, feeding, temperature, gas flow, and other monitoring applications of a test. It also converts data to Excel format via connection to a computer, using a monitoring software for the conversion of data to excel format. The commissioning of the equipment integrates monitoring into the IT system. Each controller is capable of operating up to 8 sets of reactors (total 16 reactors).
Each controller is capable of operating up to 8 sets of reactors (total 16 reactors). The PLC controller in this proposal would allow for later expansion to up to 8 pair of digesters. The PLC includes bespoke control and monitoring software for conversion of data to excel format via connection to a computer. The commissioning of the equipment integrates monitoring to the IT system.
Auto-fed digester with 10 reactors. Ten 1-litre digesters on two beams, offering two volumetric feeding rates, i.e. each beam automatically feeding five digesters.
The Caterpillar model enables a wide number of experiments running at the same time, due to the larger number of reactor tanks.
Auto-fed digester with 2, 4 or 6 reactors with volumes 2, 4 or 5-litres operating independently by single beam or offering optional multiple volumetric feeding rates, i.e. each beam automatically feeding each digester or more than one digester.
The Black Swan model allows for the incorporation of second stage reactors of 2, 4, 6, 8 or 12 L.
Auto-fed digester with 2 reactors. Two 10 or 20-litre digesters on one beam, offering one volumetric feeding rate, i.e. the beam automatically feeding two digesters.
The Ray-i version is similar to the Ray model, but its digesters are feeding independently, using 2 beams.
More information about Anaero AUTO-fed systems
Comparison between the gas flow graph of an Anaero auto-fed digester and a manual-fed digester
Gas flow (ml/h) for 5-litre digesters fed manually once a day (red), and hourly (blue) at the same organic loading rate (3.5kg VS/m 3 .d), feeding food waste at 17%VS.