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Thermal
Hydrolysis
Thermal
Hydrolysis Technology Explained
anaerobic-digestion.com
So you want to know; “What
is the thermal hydrolysis process?” – and to understand
basic thermal hydrolysis technology.
Thermal Hydrolysis is
a chemical process in which the organic molecules (in the substrate/ feed
material) are split into two parts by the addition of a molecule of water.
The process forces the water
molecules between the chemical bonds holding together large tissue molecules
such as fats, DNA and proteins.
As the name
suggests thermal hydrolysis uses heat and high pressure to break
the cellular tissues down to their original smaller molecular components.
This also
dramatically reduces viscosity, destroys all infectious agents,
and above all it hugely increases biodegradability
during fermentation.
Using thermal hydrolysis as a
feedstock pre-treatment stage before anaerobic digestion increases the
biological degradation of organic volatile solids and biogas production
considerably.
It
makes the sludge readily available for digestion by dissolving and decomposing
the sludge solids. It also makes the separation of solid and liquid phase after
digestion easier.
Up to twice the reactor throughput can be achieved compared with
an AD plant without it.
Thermal bio-solids hydrolysis is a proven
technology and is recognized as being one of the most effective ways to enhance
biogas production and solids destruction in anaerobic digestion systems.
Benefits of Thermal Hydrolysis
The benefits of hydrolysis as a carried out
prior to anaerobic digestion, can be listed as
1.
Disintegration
of cell structure of organic materials creates smaller molecules which dissolve
2.
The naturally
occurring cell polymers which result provide a form of protein, which is easily
digestible during anaerobic digestion
3.
The
lower viscosity (more free flowing) sludge allows for easier pumping and
digester tank mixing with up to double the normal digester dry solids loading
4.
The
fermentation organisms are less stressed, which leads to more stable plant
operations.
5.
The
availability of so much more of the organic matter to the methanogenic
organisms increases substrate (sludge, bio-waste etc) biodegradability and
therefore yields more biogas
6.
Separation
of liquid and solid portions of the digestate occurs more readily, with
dewatering achievable up to 40% total dry solids
7.
The
high pressure and temperature of hydrolysis produces a pathogen-free fertilizer, by holding the material at 165° C
for 20 minutes
8.
Hydrolysation
conditions meet and exceed all known national and international standards and
requirements for sterilisation, including EU Animal By Products Regulation (ABPR, 1774/2002/EC) category II & III
materials.
Potential for Thermal Hydrolysis as a
Part of AD Systems
There is a huge potential for the introduction
of thermal hydrolysis of municipal waste solids.
Incorporating thermal hydrolysis in new AD
Plants, and retrofitting it to existing plants.
For example, it represents an opportunity for
Wastewater Treatment Works operators to increase the rate of solid hydrolysis,
increase the extent of volatile solids reduction, and boost biogas production.
At the same time, the more complete reaction
achieved brings benefits to the digestate as a fertilizer.
There is an increase in nitrogen (N) and
phosphorus (P) solubilization enhancing availability of these essential
components of any fertilizer.
Companies Offering Thermal Hydrolysis Process
Equipment
Cambi has long been well-known for their
Thermal Hydrolysis Sludge Pre-treatment Technology for enhanced Anaerobic
Digestion of municipal and industrial sludges.
Cambi has been installing thermal
hydrolysis as a pre-treatment to anaerobic digestion, around the world since
1995.
However, there now seems to be a trickle-down
effect for thermal hydrolysis as a pre-treatment to anaerobic digestion, to be
used for smaller biogas plants, and a greater range of feed materials/
substrates.
Exelys is another company actively promoting
this technology, which has a thermal hydrolysis technology that they describe
as representing the next generation of bio-solids thermal hydrolysis.
But these example companies are far from being
alone in having spotted a business opportunity in thermal hydrolysis within AD
Plant Systems.
Many companies not previously active in the AD
and Biogas scene, are now also marketing their own thermal hydrolysis equipment
from their previous experience of this technology from parallel applications in
other closely related business sectors.
New Low Temperature Thermal Hydrolysis
Biosolids Technology
Lystek’s proven, low temperature, Thermal
Hydrolysis Process is now available and is said to be a cost effective,
easy-to-operate, biosolids and organics management.
Implementing a Lystek THP solution will
transform your traditional Wastewater Treatment Plant (WWTP) into a true
Wastewater Resource Recovery Center (WRRC) by harnessing and maximizing the
value in these amazing resources.
Lystek’s Thermal Hydrolysis Process
The low heat, low-cost Lystek Thermal
Hydrolysis system can be installed as an on-site, (pre or post) anaerobic digestion (AD) solution. It does not
interfere with other WWTP processes.
The unique, patented process literally
disintegrates microbial cell walls and hydrolyses complex macromolecules into
simpler compounds.
This makes the residual volatile solids in
digested biosolids more amenable to further biodegradation when introduced into
AD and biological nutrient removal (BNR) systems. via Lystek
What is Thermal Hydrolysis? It's The Missing
Ingredient for Better Biosolids
Thermal hydrolysis [as installed by United
Utilitiesis at Davyhulme WWTW] is a two-stage process combining pressure
cooking followed by a rapid decompression.
This combined action sterilizes the sludge and
makes it more biodegradable which improves digestion performance.
Sterilization destroys pathogens in the sludge
resulting in it exceeding the most stringent requirements for land application.
In addition, thermal treatment adjusts the
rheology to such an extent that loading rates to municipal sewage sludge anaerobic digesters can
be doubled, and also dewaterability of the sludge is significantly improved.
The first full-scale application of this
process for sewage sludge was for the city of Hias in Norway provided by Cambi.
Since then, there have been over 30 additional installations globally.
Thermal hydrolysis was central to the
implementation of UK water company United Utilities' sludge strategy, which was
announced in 2009.
The strategy was based on providing maximum
flexibility by enabling a combination of biosolids recycling to land or burning
for energy recovery or both depending on fluctuating current and future drivers
and legislation. via The Missing Ingredient
Our Answer to “What is Thermal Hydrolysis?” –
A Conclusion
So, let's now round-off our article on, “What
is “Thermal Hydrolysis?”
Thermal hydrolysis as a pre-treatment to
anaerobic digestion is at the time of writing, very much in the news with the
announcement that the UK Water Utility company, United utilities will soon
start to use the world's largest thermal hydrolysis plant as a pre-treatment
stage to their anaerobic digestion plant, at a major UK Wastewater Treatment
(Sewage) Works. You can read more information about
that here.
We hope that you like our “What
is Thermal Hydrolysis” video below. We looked to see whether anyone had created
one to explain the answer to “What is Thermal Hydrolysis?” No-one has, so
we made the video… You can watch it below:
Associates,
Anaerobic Digestion Community Website offers consultancy services and
promotes and develops anaerobic digestion and biogas production.
The
production of biogas is now very much a proven technology, and AD Technology is
bringing big benefits to the rapidly rising number of people that are
investing in it. But, we are still finding that a large number of its
potential beneficiaries are not aware of the true potential of
the anaerobic digestion process.
Our
mission is to spread the word about the benefits of anaerobic digestion
and biogas production.
This
“Anaerobic Digestion Community Website” is maintained as an independent web
site by EurIng Steve Last Bsc CEng MICE MCIWM CEnv.
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