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.

£26250

* 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.

Gasflowmeter

PLC controller

Caterpillar

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.  

£32025

Black Swan

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.

Ray/Ray-i

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.

£32550

from £18375

Lobster-i 

Lobster-max

Lobster-max-i

£27300

£29400

£30450

More information about Anaero AUTO-fed systems

Main features of CSTR

• More representative degradation kinetics and microbiology studies. Feeding once a day is reflected on biogas kinetics, and influences the microbiology.

• By minimising time spent feeding you can do more analysis. Auto feed all year round 24/7.

• Eliminate “feed compensations” to achieve target OLRs at the expense of representability.

• If a plant feeds 20 times a day your lab digester feeds 20 times a day. As close to real life as you can get in the lab!

• Reliable mass balances. From feeder to digestate bottles, all vessels are gas-tight. Online access to real-time gas flow monitoring.

Feed with the frequency your research really needs

• Modules available from 1 to 20 digesters per autofeeder.

• Homogenisation during feeding avoids settling or flotation of feed (air-actuated feeder agitator, or impeller blender).

• Air-tight feeder top-up using filler syringe. *1 hour work per week to fill up 18 digester feeders for automatic operation!

• System protection, such as sheer pins and automatic beam stoppers, protect from feeder overruns or valves left shut.

• Removable spill tray. Modules fixed or on castors.

A wide range of feeders to upgrade your digesters

• Vessels from 0.6 to 20 litres provide uninterrupted feeding even for long bank holidays.

• Retrofit automatic feeders for a wide range of digester sizes.

• Suitable for pure liquids and liquid-solid blends.

• Coil cooling hose around feeders to minimise decay potential.

Stainless steel variable speed mixers and gas-tight access ports add to your experimental options

• 24V/12V DC mixer motor with variable speed control.

• Stainless steel impeller mixers for low and high DS conditions.

• Calibrate reactor temperatures, measure pH, take live samples, or dose nutrients through gas-tight access ports in the digester and digestate vessels.

• 2” port for reactor filling or contingency, should it be required.

• Stainless steel digesters 2 litre to 20 litre (5 litre standard size).

• 120V AC heater jackets (other voltages available by request) for water-free temperature control (ambient to 85°C).

Real time gas flow monitoring saves you time and improves evaluation of process kinetics

• Gas flow measured using liquid displacement.

• Separate tumbling bucket (buckets 7 to 40ml as required) for each reactor for individual gas flow
monitoring.

• Flow meter compatible with HCl or Na(OH) solutions.

• Continuous logging of temperature and pressure for STP conversion.

• Our bespoke calibration syringe assures meter consistency.

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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.

BIOGAS PRODUCTION CURVE

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