What happens when a biomass boiler system is not treated with protection when it is installed? Thankfully most responsible installers do treat the new installations but don't get mixed up about another product that claims to make biomass boiler systems more efficient...the 'other' product is corrosive to the system!

1. Biomass Boiler System Case Study:
Poultry Farm
Lincolnshire, UK.
Heating system: 70 m3 - Operating temperature - 95c.
THE PROBLEM:
The system is a Weiss Multicraft 995kW biomass boiler which provides heating to 8 poultry sheds.
The system had operated for 18 months with no treatment(s) dosed into the system. The major
problems were corrosion and fouling, with corrosion deposits impacting of the performance of
the system.
An operational issue in achieving the correct temperatures in the poultry sheds was the first
indication that there was a major problem, within the system.
The overhead heaters in the poultry sheds were inspected and found to be virtually blocked with
black deposits. On Lab analysis the black deposits found in the shed heaters, were shown to be
predominately 85% iron oxide.
These black deposits were restricting the water flow and reducing heat transfer, which was the
reason why the correct temperatures could not be achieved in the poultry sheds.
The water contained in the system was sampled at various sections, and the Lab analysis showed
that the soluble and suspended iron oxide levels in the system water were very high, particularly
in the samples taken from the boiler circuit.
The black deposits were the result of corrosion of both the boiler circuit and the system
pipework. This was due to the system not having corrosion protection dosed on installation, and
then being operated for 18 months.
Black iron oxide
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2. THE SOLUTION:
There is a three phase approach to the problem;
1. Clean the system to remove the blockages and restore the heat transfer.
2. Apply a passivation treatment to arrest the corrosion of the system.
3. Dose the system with a corrosion inhibitor - Build Cert Approved - to maintain corrosion
to acceptable low levels.
Phase 1 - Clean the system;
A. Each individual overhead heater was physically cleaned to remove the vast majority of
the black deposit, and then each was flushed individually using a small flushing rig. The
heaters were flushed using Xelex DHS 3800, dosed at 1% in the recirculating water.
B. After A the whole system was flushed and cleaned using Xelex DHS 3800, dosed at 1% to
the system volume ( 1litre per 200 litres per water).
C. Complete inspection of overhead heaters after the whole system flush and clean.
* Xelex DHS 3800 is premier system cleaner for flushing systems. It penetrates and
removes iron oxide and calcium based deposits from system pipework and heat
exchangers.
Phase 2 - Passivation dosing;
A. The system was treated with Xelex DHS Passivator dosed at 0.5% of total system volume
(1 litre per 200 litres system water).
*Xelex DHS Passivator has been formulated as a treatment to inhibit metal corrosion in
boiler systems by promoting a protective film within the system.
Phase 3 - Corrosion Inhibitor Dosing;
A. The whole system was dosed with XELEX XPO Inhibitor (Build Cert Approved) at 0.5% of
the total system volume (1 litre per 200 litres system water).
* Xelex XPO has been formulated as a multipurpose treatment to inhibit metal corrosion
and scale in all types of water and is Build Cert Approved.
The Result of the three phase cleaning and dosing was;
A. The system was re-established with the correct water flow rates.
B. Heat transfer was restored.
C. Temperature controls were restored.
D. Correct ‘poultry shed’ temperatures were achieved.
E. The whole system now benefited from additional protection against corrosion with the
dosing of the Xelex XPO Build Cert Approved Inhibitor.
F. The total soluble iron oxide and soluble copper levels were dramatically decreased after
flushing and cleaning with the Xelex DHS 3800, Xelex DHS Passivator and Xelex XPO
products.
A clean biomass boiler system = a reduced maintenance regime and sustained RHI revenue.
A dirty biomass boiler system = reduced efficiency, increased maintenance costs, reduced
RHI revenue, and in the event of break down - TOTAL loss of RHI revenue!
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3. REDUCTION FIGURES:
The total iron, (inc solube), and soluble copper levels were dramatically decreased after
using the Xelex DHS Passivator, Xelex DHS 3800 and Xelex XPO (Buid Cert Approved)
products, compared to the pre-treatment levels:
Analytical
Parameter
Units Before treatment After treatment
Total Iron mg/l 125.0 4.5
Soluble Iron mg/l 14.5 2.3
Soluble Copper mg/l 1.2 0.2
Instantaneous corrosion rates for mild steel measured with a corrater probe also showed a
dramatic reduction in corrosion rates from 0.218 mm/y with no treatment, down to 0.012
mm/y, with treatment.
CONCLUSION:
Biomass boilers are popular with the farming community because of their environmentally
friendly aspects and the availability of sustainable fuel.
The systems can be filled with a variety of water qualities, and many use mains water
supplies. In some cases the boiler manufacturer recommends the use of softened or
demineralised water to charge the systems - this recommendation is clearly ambiguous,
because where you have metal and water in contact - without protective measures - there
will be corrosion.
The quality of water used to charge any system can also vary from area to area in the UK.
These range from softened or naturally soft water through to hard water. Now couple this
with UK regional water variations and the ambiguous instructions from the boiler
manufacturers, and the biomass boiler systems will not run efficiently, scale-up and/or
corrode, unless the systems are treated with protection, at the installation stage.
This case study highlights the problems that can occur by operating a hot water boiler such
as a biomass boiler, WITHOUT using any treatment within the system!
After 18 months of operation with no treatment dosed into the system the overhead
heaters (used to control the temperature in the poultry sheds) were virtually blocked with
corrosion debris (black iron oxide). This severely restricted the water flow and
subsequently reduced heat transfer. The black iron oxide was produced as a result of
corrosion within both the boiler and the system pipework. The majority of the corrosion
took place in the boiler, and if this was allowed to go unabated, it would seriously reduced
the life expectancy of the boiler.

4. To effectively treat and protect a biomass boiler, and the associated system, it needs to be
dosed with a multipurpose corrosion inhibitor - Xelex XPO (Build Cert Approved) - on
installation and charging of the system. Once the biomass boiler system is operational,
water samples should be taken on a quarterly basis, and an analysis of the of liquid carried
out. The level of inhibitor, where installed, should be checked at regular intervals, and
topped up where necessary.
Iron and copper levels should also be measured to monitor that corrosion is under control.
If any biomass boiler system has not been treated, then this case study demonstrates that
it is possible to recover the situation, and protect a very expensive asset!
There is an associated Q & A document to accompany this case study. It is available upon
request by emailing phil@valeec.com.
The XP2 product is an A1 Build Cert Approved Inhibitor which also has energy saving
properties - it protects and saves all in one. The dosing of the XP2 product on installation
will protect the system and produce fuel savings of up 15% PA. How much fuel costs PA
could you save on buying tonnes of chip or pellet for your biomass boiler installation?
For further information on the XELEX Product range and the solutions that it can provide
for your biomass boiler systems, please email:
Philip. S.Lawrence
phil@valeec.com
VALE ENERGY LTD
UNIT 33 Llys Edmonds Prys Street,
Asaph Business Park,
St Asaph,
LL17 0JA.
www.valeenergy.co.uk
www.valeec.com
phil@valeec.com
Vale Energy Ltd is the authorised and exclusive UK distributor for the Xelex Global product range to
the renewables and farming sectors.