Efficiency Gains using Andrews Chillers to cool down Digesters - - PowerPoint PPT Presentation

Dean Clayton Andrews Sykes Hire Ltd

Efficiency Gains using Andrews Chillers to cool down Digesters during Maintenance periods.

The Role of Digesters in Waste Water Treatment.

• Simply put, digesters are large vats of
• rganic matter. Anaerobic bacteria in a

digester break down the sewage sludge, producing methane gas in the process.

• The methane gas is an important source of

energy and is often used to produce heat and power within the works.

• Combined Heat and Power (CHP) plants use

the gas to produce energy.

Cooling required for Digester maintenance

• The optimum operating temperature for

mesophilic digesters is 32-37° C.

• During times when Digesters have to be

shut down for maintenance, it is necessary to reduce the temperature to below 20°C, so that gas production ceases and it is then safer to work with the sludge from inside the tank.

Planning for Digester Maintenance

• The Dilemma:
• Do you wait for the digester to cool down,

without any further input, or do you spend money hiring Andrews Chillers to speed up the cooling.

• Especially with Insulated Digesters, it can

take several weeks to cool the digester down to below 20 Degrees C.

Option1: Non Intervention.

Wait for digester to cool without intervention. Disadvantage of this option:

• Can take several weeks, for ambient air temp to

cool down the Digester.

• Supply of gas to CHP plant is much reduced,

additional energy would have to be sourced.

• Digester out of action, interrupting flow through

the works.

Option 2. Active Intervention.

• Andrews Chiller Rental.
• Benefits of this option:
• Digester is back on line more quickly.
• Gas production for CHP plant back on-stream

faster and producing energy.

• The cost of Chillers can be less than the

value of the lost gas production during the period of down time.

Chillers Rental decision can be made on economic grounds

Calculations have shown that there are economic benefits for cooling digesters rapidly down to below 20°C, when there is a need to take a digester off line, for maintenance. The significant cost of lost gas production for the CHP plant can be greatly reduced by temporary hiring Andrews Chillers.

Andrews Chiller Unit Biffa Waste Wanlip STW

Chiller Hire For Digesters

Chiller Hire for Digesters

• Chiller Installation is simple to carry out.
• Temporary hoses from the Chiller unit are

coupled to the In Situ heat exchanger.

• Coolant fluid from the Chiller is circulated

through the heat exchanger to cool the digester sludge.

• Temperature quickly drops from 37°C to

20ºC.

Riverside STW Chiller Rental

Chiller Hire for Digesters

• Conclusion:
• Chiller Hire has the following benefits.
• Digester down time is minimised.
• Gas production is resumed quickly.
• Cost of Chiller Hire can be less than cost of

lost energy production.

Chiller Hire for Digesters

Thank You. Please visit our stand if you have any questions.