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Shell and Tube Heat Exchangers in Anaerobic Digestion Plants

Sludge Specification

No two sewage treatment plants are alike since the sludge is an organic product. The thermal properties of these products, specifically the viscosity, can change significantly. Other thermal properties such as density, specific heat and thermal conductivity are also taken into account in the design of the heat exchanger for the particular plant. Once the sludge specification had been defined this was compared to Sacome’s in-house database where records of comparable dry solids equivalents are kept for this work. In this particular case there was no need for rheological testing (study of liquid flow characteristics) but such tests are routinely carried out in the labs at Sacome’s head office especially where process guarantees are required for a particular heat exchanger.
Sewage treatment plant

The Options

There are a number of different geometries of heat exchangers available today including Plate Heat Exchangers and Tubular Heat Exchangers. Plate Heat Exchangers are generally not suitable for sewage sludge which is why spiral and tubular types are in widespread use in the WWTP’s. Thicker, more viscous sludges with higher solids and fibers contents can block the channels requiring frequent cleaning and inevitable shutdowns. Sacome’s Shell and Tube Heat Exchangers have a very much larger process channel, avoiding the risk of blocking.
Waste water treatment plant


Due to the high levels of solids in the sludge Sacome’s model TF20 were selected as the ideal solution because:

• Mono-tubular design. The TF20 model consists of 2 concentric tubes in which the water used as heating medium flows through the annular space, while the sewage sludge flows through the inner tube. Unlike the traditional multi-tube, composed of a tube bundle with smaller inner tubes, there is only one process channel.

• Modular design. As it is a modular design, it is easy to dismantle the units for cleaning or to add more modules to handle additional capacity.

• Process duty. The heat exchanger can process a wide range of capacities and can be configured with several lines in parallel so there is no need to stop production for cleaning.

• Corrugation. The inner tubes are hard corrugated in order to increase the turbulence of the product. This reduces the risk of fouling and increases.

• Materials of Construction. Due to the presence of phosphate and ammonium precipitated (struvite) 316L stainless steel was recommended. This is more resistant to corrosion than 304L.

• Insulation. In this particular case the heat exchangers were insulated with 40 mm of mineral wool clad in aluminum to reduce the heat losses to the environment.

Installation And Start-Up

Sacome took the design brief and working closely with the technical experts and engineers in the distilleries refined the product and achieved the desired result. It is hardly surprising that Sacome is the first choice for distillers in the UK.

Do You Have Any Questions?

We are keen to help and we will be pleased to discuss any issues you may have
Tel: 0141 882 3351
Centri-Force Engineering Limited
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