Evaluation of steam and water chemistry for increased flexibility in a combined cycle power plant

Abstract

Steam and water chemistry is fundamental for most power generation on indus
trial scale. This includes the dosing of chemicals, the monitoring of both water
and steam, as well as understanding the underlying causes to diagnose eventual
problems. Öresundsverket, which was designed for seasonal operation, now has to
perform multiple starts per year and in meeting these demands there is a possi
bility to increase their flexibility to the grid, through optimized chemistry control.
This report aims to first observe the transients of contamination, during start up,
in the boiler by manual sampling. Secondly, to evaluate the impact this has on
critical systems in the process, such as the turbine and the boiler itself. Lastly,
this report aims to suggest possible remedies to adverse the unwanted outcomes,
with the main focus on increasing their flexibility in regards to variable operation,
evaluate damage mechanisms, and reduce boiler blow-down. To this end, the boiler
was sampled, python models were produced, and a condensate polishing plant eval
uated. To observe what contaminants enter and leave the boiler, multiple samples
were procured during a cold start and later analyzed for silica, iron, copper, sodium,
and ammonia, in addition to these the plant’s installed monitoring was used as well.
To see the impact of impurities on critical system, two models were produced. One
model aimed to evaluate the turbine when faced with temperature transients. The
other model was produced to simulate the dynamics of the contamination during
start-up, and see the efficacy of a precoat regarding start-up time. From the results
the main contaminations were found to be located to the high, and intermediate
pressures. For the high pressure system the main contamination was attributed to
the silica and sodium in the steam. For the intermediate pressure system the high
est concentrations were found to be the iron and sodium in the boiler water. The
system models were able to produce the expected results. For the turbine model
large transients, which are uncommon, are required to cause harm. For the drum
model the time that could be saved came to 13% of a cold start, which provided an
IRR of 9%. From the system models there is a lack of sufficient validation to draw
conclusions from. Finally, it’s clear that there are numerous benefits in installing
a condensate polishing plant. For one there is potential economic gain, there is a
sustainability aspect in saving in on fresh water from the use of make-up water, by
reducing boiler blow-down. By ensuring correct chemistry for starts and shutdowns
corrosion can be minimized in the boiler and turbine.

Popular Abstract

Is the water we drink really pure? Not really, if you
consider the purity required for adequate operation on an
industrial steam and water cycle. Due to high
temperatures and pressures these plant require multiple
support units to ensure high purity water for economic,
and reliable operation.
Öresundsverket in Malmö wants to evaluate their water
purity with the purpose to achieve more flexibility to the
grid. In doing this, it was found that a condensate
polishing plant could be useful.
Water is a chemical compound composed
by oxygen and hydrogen (H2O), whose
unique characteristics has laid the foundation for all
life. An other honorary ability is its capacity to solve
other compounds, this is a reason as to why water
very seldom only water, but rather as water with a
mixture of gases, salinity and particle matter. Wa
ter with some amount of impurities is preferred for
drinking, but can be detrimental for an industrial
boiler and turbine. It’s like making coffee with too
hard water, if not maintained it most surely will clog.
Öresundsverket, a combined cycle power
plant operating on natural gas, was built for
seasonal production at full power. However, due to
the cost of operating on gas and the demand of elec
tricity being unpredictably variable, even on a day
cycle, the plant now sees a need to increase their
flexibility. This is done by addressing one of their
bottlenecks for fast starts, namely the waiting for
steam chemistry during start-ups. This relates to
the process of removing water from the boilers and
replacing it with demineralized water until the steam
has good enough chemistry.
It was found that there are things a plant can
to to save in on start-up time, these are pre
sented here without any particular order. The first,
would be to use a condensate polishing plant, with
the purpose to remove impurities from the conden
sate stream before even entering the boiler, with the
drawback of being a substantial investment. The
second thing is to optimize the monitoring in such a
way that only the most crucial information is used
to operate the plant.
There are also many issues with operating the plant
with poor chemistry. These is much that can go
wrong when preparing for starts or stops, which
stresses the importance of proper layups. If not op
erated correctly environments promoting corrosion
can be created and the damages can become very
expensive. From a lack of understanding the un
derlying mechanisms of how these types of damages
occur, the risk of improper layups are much higher.
There are many plants that are in a simi
lar position to Öresundsverket, which is why
increasing the flexibility in regards to electricity gen
eration is a topic of interest for other industries. Es
pecially in a time where secure and reliable energy
is needed. This being said, there is no universal way
to ensure good chemistry which is applicable for all
plants, rather they require a case-by-case approach.
To reach this conclusion, many samples were
taken and many hours were laid on programming.
To understand what was present in the boiler a mul
titude of samples were collected and later analyzed
at a lab. This provides a basis to understand what is
potentially harmful to the boiler. By using the data
for simulations it’s possible model how a new com
ponent changes the dynamics of the system. This
gives the user ample insight to whether or not such
a component is worth installing or not. This was
conducted and this new component, i.e. the CPP,
showed great promise for increasing flexibility at an
economical gain, and sustainable perspective.

• author: Bruxe, Astor
• supervisor: Ola Wallberg; Axel Carlsson
• organization: Chemical Engineering (M.Sc.Eng.)
• course: KETM05 20261
• year: 2026
• type: H3 - Professional qualifications (4 Years - )
• subject: Science General
• keywords: Steam chemistry, Water chemistry, HRSG, CCPP, 3PRH, Chemical engineering
• language: English
• id: 9229740
• date added to LUP: 2026-06-01 14:42:28
• date last changed: 2026-06-01 14:42:28