Sludge Applications

1) Keeping sludge at the correct temperature in Mesophilic Digesters

2) New Developments-Thermal hydrolysis process to reduce moisture content in sludge

Reference List UK

Severn Trent 2008 4 Projects (incl skid)

Nomenca Acid Phase Digester Derby

Black and Veatch Ashford STW

MJ Gleeson Bury Hill STW, Wessex Water

AC Chester Stoke on Trent

North Midland Construction Derby Acid Phase Digester

Earthtec Lundwood, Barnsley

Birse (x2) Gravesend WwT; Southern Water

Meica (x2) Welsh Water; Bolton WwT

Majex (x2) Yorkshire Water; Northwest Water

Thames Water Reading

Severn Trent Water

• Problem– Existing Heat Exchangers (spiral and smooth

tube) blocking up (raggy sludge catching on studs which separate channels)

– Weekly cleaning required, resulting in justification for replacement units

• Challenge– To fit replacement Tube in Tube units into the

existing space, and utilising existing pumps

Claymills STW Pilot

• First visit to measure up space available• Design exchanger to fit duty of 450kW• Footprint of 3558L x 847W x 2070H mm• Check that existing hot water and sludge pumps

could achieve the duty• Water had to be in split flow in order to minimise

the pressure drop through the HEX• Work very closely with the installation company

and Severn Trent

Original Unit (1 of 3)

2 of the units

No 1 HRS exchanger

3 x HRS Exchangers

New Technologies

• Thermal Hydrolysis of bio-degradable material– High temperature and pressure applied– Breaks cell walls

• Unicus Scraped Surface Heat Exchanger is ideal for this application

SECOND GENERATION BIOFUELSBiomass Processing

In general three types of hydrolysis can be identified for biomass processing:

Enzymatic: enzymes are used to break open the biomass structure. => Disadvantage: high enzyme cost.

Dilute acid: using acids the lignin barrier can be broken and cellulose chains are broken up in pieces.

=> Disadvantage: strong acids require use of expensive materials. Acidic effluents can cause problems

Thermal: applying high temperatures and pressures the same effect is obtained: lignin is broken up and cellulose chains are cut. By introducing steam explosion, the effect is enhanced.

Thermal processes are the most promising. Traditionally batch heating + batch steam explosion are applied. High investment costs are involved however and batch operation has disadvantages compared to continuous operation.

HRS CONTINUOUS THERMAL HYDROLYSIS PROCESS

HRS presents a continuous processfor thermal hydrolysis:

CelluloseHemi cellulose

Lignin

Traditional problem of thermal hydrolysis:

Thermal hydrolysis means heating biomass to 160-180 ºC under pressure. However, biomass at elevated temperatures is a fouling substance. Heat exchangers that foul loose performance. That is why batch heating processes have been developed.But high temperatures and high pressures mean expensive pressure tanks. The high investment cost and discontinuous operation are disadvantages.

How has HRS overcome these disadvantages?

Applying its patented scraped surface heat exchanger: The Unicus.

Key points of the HRS Process:

HRS has developed patented technology for fouling free heat transfer:THE UNICUS SCRAPED SURFACE HEATEXCHANGER.

This heat exchanger has been successfully applied in many food and industrial applications.

The Unicus makes it possible to continually heat biomass without fouling

By exchanging energy between hydrolyzed biomass and cold incoming biomass valuable energy is recovered.

SCRAPED SURFACE HEAT EXCHANGERS MAKE THERMAL HYDROLISIS POSSIBLE IN A CONTINUOUS AND ENERGY EFFICIENT PROCESS.

The HRS Process (patent pending):Option 1: without steam explosion.

The HRS Process (patent pending):Option 2: with steam explosion.

Advantages of the HRS Process:

1.The process is continuous, an easier way of production.2.The use of scraped surface heat exchangers ensures a fouling free operation.3.Energy is exchanged between hot and cold biomass, energy recovery reduces the cost for biomass hydrolysis.4.The process can be applied to many different feed stocks.5.Applications in biogas and bioethanol.6.The technology can be inserted in existing plants for enhancing yields.7.Depending on the feedstock, yields can be increased (more bio fuel) and fermentation times can be reduced (smaller digesters).

Case study:Town of Pirmasens, Germany:

Municipal waste water plant (60.000 inhabitants).Anaerobic digesters produce biogas for electricity generation.HRS supplied heat exchangers for thermal hydrolysis.Running since March 2008.Biomass conversion to biogas has increased from 40% to 70% due to thermal hydrolysis.Increased biogas production has decreased digester dimensions.The town of Pirmasens hopes to save 100.000 € per year on energy costs.More conversion means less waste sludge. Money is being saved.