STEAM PLANT AND METHOD OF OPERATING THE SAME
The invention relates to a steam plant, a method of operating the same, and a method
of upgrading an existing steam plant.
5
In an lndustrlal and heatlng process utlllslng steam, steam Is generated In a boller and
is transferred through pipework at high temperature and pressure to various industrial
processes where the energy in the steam is utilised.
10 It is important to control the quality of the raw water fed to the boiler in order to prevent
undesirable effects from occurring within the steam plant. These undesirable effects
include corrosion of the metal components of the plant, such as pipework and valves,
and the reduction of heat transfer rates which can lead to overheating and the loss of
mechanical strength of components.
15
Water is referred to as being either "hard or "soft"'. Hard water contains scale-forming
impurities while soft water contains little or none. Hardness is caused by the presence
of the mineral salts of calcium and magnesium and it is these minerals that encourage
the formation of scale. If hard water is supplied to the boiler then scaling of the heat
20 transfer surfaces will occur and this will reduce the heat transfer and efficiency of the
boiler. Further, if the water supplied to the boiler contains dissolved gases, particularly
oxygen, the corrosion of the boiler surfaces, pipework and other surfaces is likely to
occur. If the pH value of the water Is too low, the acldlc solutlon wlll attack metal
surfaces, and if the pH value is too high and the water is alkaline, other problems such
25 as foaming may occur.
It is also desirable to prevent boiler water from being carried over from the boiler to the
steam system as this can result in the contamination of control valves and heat transfer
surfaces, and the restriction of steam trap orifices. Carryover is typically caused by
either "priming" or "foaming". Priming is the ejection of boiler water into the steam takeoff
and is generally due to either operating the boiler with too high a water level,
operating the boiler below its design pressure, or excessive steam demand. Foaming
is the formation of foam in the space between the water surface and the steam take-off
and is primarily due to a high-level of impurities in the boiler wator.
As the boiler generates steam, any impurities which are in the boiler water and which
do not boil off with the steam will concentrate in the boiler water. As the amount of total
dissolved solids (TDS) become more and more concentrated, the steam bubbles tend
to become more stable, failing to burst as they reach the water surface of the boiler.
5 Eventually, a substantial part of the steam space in the boiler becomes filled with
bubbles and foam Is carrled over Into the maln part of the steam plant. It Is therefore
desirable to carefully control the amount of total dissolved solids (TDS) in the boiler
water. The TDS value of the boiler water is monitored using a sensor and water known
as blowdown water is discharged from the boiler to a blowdown vessel in order to
10 maintain the TDS value within acceptable limits. Conventional boilers may be operated
with the TDS in the range of 2000-3500 ppm. The blowdown water is mixed with
colder water in the blowdown vessel and is then discharged to a drain.
Table 1 below shows the technical and commonly used names of some typical
15 impurities in water, their chemical symbols, and their effects.
Name
Calcium carbonate
i Calcium bicarbonate
Calcium sulphate
Symbol
CaCOa
Common name
Chalk, limestone
/ Calcium chloride
I I I
I I I 1 Magnesium sulphate I MgS04 I Magnesite / Corrosion
EIfect
Sofi scale
Ca(HCO3)2
CaS0,
1 CaCll
I 1 1
1 Corrosion
Magnesium carbonate 1 MgC03
I I I
Sodium carbonate / Na2C03 / Washing soda or soda 1 Alkalinity
Gypsum, plaster of paris
1 Soft scale
I 1 Magnesium bicarbonate
Sodium chloride
/ Sodium bicarbonate
I I I I NaHC03 I Baking scda / Priming, foaming
Soft scale + C02
Hard scale
j Sodium hydroxide j NaOH 1 Caustic soda / Alkalinity, embrittlement 1
Mg(HCO&
NaCl
Table I
Epsom salts
Common salt
Sodium sulphate
Silicon dioxide
20 It is known to treat raw water by removing various impurities before providing it to the
boiler as feedwater so as to minimise the undesirable effects described above. For
example, if the water is too hard then soale forms in the boiler, and if the TDS value is
Scale, corrosion
Electrolysis
Na2S02
Si02
Glauber salts
Silica
Alkalinity
Hard scale
too high then the blowdown rate of the boiler must be increased in order to prevent the
TDS value in the boiler from becoming too high and leading to carryover.
The water treatment system of a steam plant typically comprises a filter unit, a softener
unit and a reverse osmosis unit and raw water is passed through these units
sequentially.
The filter unit is typically a carbon filter and acts to remove suspended solids from the
raw water. The filter must be periodically flushed in order to clean the filter and flush
away debris that has built up in the filter.
The softener unit acts to reduce the hardness of the filtered water and typically
comprises two softener vessels and a brine tank. Each softener vessel is provided with
a resin to which sodium ions are bonded. As the filtered water is passed over the
resin, the sodium ions bonded to the resin are displaced and exchanged for the
calcium and magnesium ions in water, thus reducing the hardness of the water. After a
period of time, all of the sodium ions will have been displaced from the resin and
replaced with calcium and magnesium ions. Therefore, the softener vessel is
regenerated by flushing the resin with a strong solution of sodium chloride from the
brine tank. This causes the calcium and magnesium ions bonded to the resin to be
replaced with sodium ions. The softener vessel is then flushed with water so as to
remove the un-bonded calcium and magnesium ions from the softener vessel.
Typically, whllst one softener vessel Is belng used, the other Is belng regenerated so
that water can be softened without interruption.
The reverse osmosis unit acts to reduce the TDS value of the softened water. The
reverse osmosis unit comprises a semi-permeable membrane provided between two
chambers. The softened water having a high TDS value is supplied to one of the
chambers and pressure is applied. The applied pressure causes pure water, having a
low TDS and known as permeate, to pass through the semi-permeable membrane to
the other chamber. Concentrate containing a high concentration of impuriiies, and
consequently having a high TDS value, is retained on the pressurized side of the semipermeable
membrane. The permeate is supplied to the boiler as feedwater via a
feedtank, and the concentrate is discharged to a drain. The softened water supplied to
the reverse osmosis unit may have a TDS value of 220 ppm and the permeate used as
feedwater may have a TDS value of 23 ppm.
As should be appreciated from the above, a steam plant requires substantial volumes
of water in order to operate. Specifically, raw water that is ultimately used to generate
steam, cold water that can be mixed with the hot blowdown water, water for the brine
5 tank of the softener unit, and flushing water for both the filter and the softener unit.
Water Is flnanclally an expenslve resource and contrlbutes to a large proportion of the
running costs of a steam plant. Further, a large proportion of this water is ultimately
discharged to a drain and water authorities typically levy a charge for this. Water is a
finite resource and demand on water supplies is increasing.
10
Therefore, from both a financial and an environmental point of view it is desirable to
reduce the water consumption of a steam plant.
According to an aspect of the invention there is provided a steam plant, comprising: a
15 processing unit arranged to treat raw water; a boiler arranged to generate steam; a
blowdown vessel in fluid communication with the boiler so as to receive hot blowdown
water from the boiler; and a reverse osmosis unit in fluid communication with the
processing unit though an inflow water line, the boiler through a permeate line, and the
processing unit andlor the blowdown vessel through a concentrate line; wherein in use,
20 the reverse osmosis unit receives treated inflow water from the processing unit and
generates permeate which is provided to the boiler through the permeate line and
concentrate which is provided to the processing unit andlor the blowdown vessel
s
through the concentrate Ilne. In other aspects of the Inventlon, the concentrate may be
provided to the boiler, via a feedtank (otherwise known as a hotwell), and/or the RO
25 inlet of the reverse osmosis unit instead of, or in addition to, the processing unit and/or
the blowdown vessel.
By using concentrate from the reverse osmosis unit in the processing unit andlor the
blowdown vessel, the water consumption of the steam plant may be reduced, thereby
30 reducing the operating costs of the steam plant and reducing the environmental impact
of the steam plant.
The processing unit may comprise a softener unit including at least one softener vessel
and a brine tank. The concentrate may be provided to the brine tank and may be
35 subsequently used to regenerate the at least one softener vessel. By using the
concentrate to fill the brine tank, the use of raw water typically used to fill the brine tank
may be reduced. The concentrate may be provided to at least one softener vessel so
as to flush the softener vessel. By using the concentrate to flush the softener vessel,
the use of raw water typically used to flush the softener vessel may be reduced.
5 The processing unit may comprise a filter, such as a carbon filter. The concentrate
may be provlded to the fllter so as to flush the fllter. By uslng the concentrate to flush
the filter, the use of raw water typically used to flush the filter may be reduced. The
concentrate may be provided to the blowdown vessel where it is mixed with hot
blowdown water so as to cool the blowdown water. By using the concentrate to cool
10 the hot blowdown water, the use of raw water typically used to cool hot blowdown
water may be reduced.
The steam plant may further comprise a concentrate tank arranged to receive and
temporarily store concentrate from the reverse osmosis unit.
15
According to another aspect of the invention there is provided a method of operating a
steam plant, comprising: providing raw water to a processing unit which generates
treated inflow water; providing the treated inflow water to sl reverse osmosis unit which
generates permeate and concentrate; providing the permeate to a boiler; and providing
20 the concentrate to the processing unit and/or a blowdown vessel.
The processing unit may comprise a softener unit including at least one soffener vessel
and a brlne tank. The concentrate may be provlded to the brlne tank; and the method
may further comprise: regenerating the at least one softener vessel using concentrate
25 from the brine tank. The method may further comprise flushing the at least one
softener vessel with the concentrate.
The processing unit may comprise a filter. The method may further comprise flushing
the filter with the concentrate.
30
The method may further comprise providing the concentrate to the blowdown vessel
and mixing with hot blowdown water so as to cool the blowdown water
The method may further comprise temporarily storing the concentrate in a concentrate
35 storage tank, and subsequently providing the concentrate to the processing unit andlor
blowdown vessel.
According to another aspect of the invention there is provided a method of modifying
an existing steam plant comprising a processing unit arranged to treat raw water; a
boiler arranged to generate steam; a blowdown vessel in fluid communication with the
5 boiler so as to receive hot blowdown water from the boiler; and a reverse osmosis unit
In fluld communlcatlon with the processlng unlt though an Inflow water llne and the
boiler through a permeate line and having a concentrate output, the method
comprising: fluidically connecting the concentrate output of the reverse osmosis unit
with the processing unit and/or the blowdown vessel through a concentrate line, such
10 that during use of the steam plant, concentrate can be provided to the processing unit
and/or the blowdown vessel through the concentrate line.
The invention may comprise any combination of the features andlor limitations referred
to herein, except combinations of such features as are mutually exclusive.
15
Embodiments of the present invention will now be described, by way of example, with
reference to the accompanying Figure 1 which schematically shows part of a steam
plant.
20 Figure I schematically shows part of a steam plant 10 comprising a processing unit
12, a reverse osmosis unit 14, a feedtank (hotwell) 18, a boiler 18, and a blowdown
vessel 20. In use, the processing unit 12 and reverse osmosis 14 treat raw water
whlch Is supplled to the boller 18 vla the feedtank 16 to generate steam. The steam
generated by the boiler 18 is transferred through pipework at high temperature and
25 pressure to various industrial processes where the energy in the steam is utilised (not
shown). At periodic intervals, blowdown water is discharged from the boiler 18 to the
blowdown vessel 20 where it is cooled and discharged. Although not shown in the
schematic of Figure I , various pumps, valves and sensors may be provided to control
the flow of water and steam around the system.
30
The processing unit 12 has an inlet 22 for receiving raw water, and an outlet 24 for
discharging treated water. The processing unit 12 comprises a filter 26, in the form of a
carbon filter, and a softener unit 28 that are fluidically connected in series. The filter 26
is arranged to remove suspended solids from the raw water and the softener unit 28 is
35 arranged to reduce the hardness of the water. The filter 26 is also provided with a
flushing water line 36 and a drain line 38. The softener unit 28 includes first and
second softener vessels 30, 32, each containing a resin to which sodium ions are
bonded, and a brine tank 34 for regenerating the softener vessels 30, 32. The softener
unit 28 is also provided with control valves that allow filtered water to flow through one
softener vessel 30, 32 whilst the other softener vessel 30, 32 is being regenerated.
5 This allows the softener unit 28 to be continuously used. The softener unit 28 is also
provlded wlth a brlne tank flll llne 40, a flushlng water llne 42, and draln llnes 44.
Although it has been described that there is a filter 26 and a softener unit, in other
embodiments only one may be present. Further, additional water treatment devices or
10 units may be incorporated into the processing unit 12 as necessary.
The outlet 24 of the processing unit 12 is fluidically connected to the RO inlet 46 of the
reverse osmosis unit 14 with an inflow water line 48. This allows raw water treated by
the processing unit 12 to be supplied to the reverse osmosis unit 14. The reverse
15 osmosis unit 14 is arranged to reduce the total dissolved solids (TDS) value of treated
inflow water provided from the processing unit 12. As schematically shown in Figure 1,
the reverse osmosis unit 14 comprises an inflow chamber 50 and a permeate chamber
52 separated by a semi-permeable membrane 54. The RO inlet 46 opens into the
inflow chamber 50 which is further provided with a concentrate outlet 56 from which
20 concentrate, having a high TDS value, can be discharged. The permeate chamber 52
is provided with a permeate outlet 58 from which permeate, having a low TDS value,
can be discharged, In use, the inflow chamber 50 is maintained under pressure and
Inflow water Is provlded to thls chamber through the RO Inlet 46. Pure water, known as
permeate and low in impuriiies, passes through the membrane 54 where it can be
25 discharged from the permeate outlet 58, whilst concentrate, high in impurities, can be
drawn from the concentrate outlet 56.
The permeate outlet 58 of the reverse osmosis unit 14 is connected to a permeate line
60 which is configured to supply the permeate generated by the reverse osmosis unit
30 14 to the feedtank 16. In turn, the feedtank 16 is fluidically connected to the boiler 18
by a feedwater supply line 62 so that feedwater in the feedtank '16 can be supplied to
the boiler 18. The boiler 62 is configured to generate steam from the feedwater and is
provided with a steam supply line 64 for delivering and transferring the steam to
various processes (not shown) within the steam plant.
The boiler 18 is also provided with a blowdown outlet 66 towards the bottom of the
boiler to which a blowdown line 68 is attached. The blowdown line 68 connects the
boiler 18 to the blowdown vessel 20 such that hot blowdown water can be discharged
from the boiler 18 to the blowdown vessel 20. The blowdown vessel 20 is further
5 provided with a drain line 70 which allows cooled blowdown water to be discharged to a
draln.
In addition to the components described above, the steam plant 10 is further provided
with a concentrate storage tank 72 that is fluidically connected to the concentrate outlet
10 56 of the reverse osmosis unit 14 by a concentrate line 74. This allows concentrate
generated by the reverse osmosis unit 14 to be fed to and stored by the concentrate
tank. The concentrate storage tank 72 is connected to various other components of
the steam plant 10 with various concentrate lines. Specifically, in this embodiment the
concentrate storage tank 72 is connected to the blowdown vessel 20 with a line 76, the
15 flushing line 36 of the filter 26 with a line 78, the brine tank fill line 40 of the brine tank
34 with a line 80 and the flushing line 42 of the softener unit 28 with a line 82. This
allows concentrate from the reverse osmosis unit 14, temporarily stored in the
concentrate storage tank 72, to be supplied to these various components.
20 In use, raw water is provided to the inlet 22 of the processing vessel 12 and is passed
through the carbon filter 28 to remove any suspended particulate in the water. The
filtered water is then passed through the softener unit 28 to reduce the hardness of the
water. The sottener unlt 28 comprlses two softener vessels 30, 32 and the flltered
water is passed through one of these vessels 30, 32 whilst the other vessel is being
25 regenerated (as will be explained below). As the filtered water is passed over the resin
in the softener vessel 30, 32, the magnesium or calcium ions in the water displace and
replace the sodium ions bonded to the resin. This therefore reduces the hardness of
the water by replacing the magnesium and calcium ions with sodium ions. The filtered
and softened water is then fed to the RO inlet 46 of the reverse osmosis unit 14 as
30 treated inflow water through the inflow water line 48. The treated inflow water enters
the inflow chamber 50 of the reverse osmosis unit 14 and is subjected to a high
pressure. Permeate that is low in impurities, and which consequently has a low TDS
value, passes through the membrane 54 to the permeate chamber 52, whilst
concentrate high in impurities, and which consequently has a high TDS value, is
35 retained in the inflow chamber 50. The concentrate is drawn through the concentrate
outlet 56 of the reverse osmosis unit 14 at a known rate and is fed to the concentrate
storage tank 72 through the concentrate line 74. The permeate, which is relatively soft
and which has a relatively low TDS value, is fed to the feedtank 16 through the
permeate line 60. Various chemicals are supplied to the feedwater in the feedtank 16.
Boiler feedwater is fed to the boiler 18 through the feedwater supply line 82 where it is
5 heated to generate steam. The steam is transferred to various industrial processes in
the steam plant 10 through the steam supply llne 64.
The impurities in the boiler water within the boiler 18 concentrate as they do not boil off
and the TDS value of the boiler water therefore increases. As previously discussed, if
10 the TDS value is too high then foam forms within the boiler which may be carried over
into the remainder of the steam system. Therefore, at periodic intervals, blowdown
water having a high TDS value is discharged from the boiler 18 through the blowdown
outlet 66 to the blowdown vessel 20 via the blowdown water line 68. The temperature
of the blowdown water is too high for it to be immediately discharged to a drain.
15 Therefore, the hot blowdown water supplied to the blowdown vessel 20 is mixed with
cooler water within the blowdown vessel 20 before it is discharged through the drain
70. In this embodiment, the concentrate generated by the reverse osmosis unit 14 and
stored in the storage tank 72 is supplied to the blowdown vessel 20 through the line 76.
The concentrate is at approximately ambient temperature and therefore can be used to
20 cool the hot blowdown water. If there is insufficient concentrate available to sufficiently
cool the hot blowdown water, then water from another source, such as raw water, can
be used in addition. Since the concentrate is only being used to cool hot blowdown
water, It does not matter that It Is hlgh In Impurltles.
25 The use of concentrate, that would ordinarily be directly discharged to a drain due to its
high level of impurities, to cool hot blowdown water eliminates, or at least reduces, the
amount of raw water that is required in the blowdown vessel. There is therefore a
financial saving as the cost of raw water to coal the hot blowdown water is eliminated
(or at least reduced), and the cost of disposing of the concentrate is also eliminated (or
30 at least reduced).
After a period of time, the filter 26 will become blocked with the suspended solids which
it has removed from the raw water. It is therefore necessary to periodically flush the
filter 26 with flushing water. In this embodiment, concentrate generated by the reverse
35 osmosis unit 14 and stored in the storage tank 72 is supplied to the filter flushing line
36 and is used to flush the filter 26 so as to remove any debris. The concentrate used
to flush the filter 26 is then discharged through the drain 38. If there is insufficient
concentrate available to flush the filter 26, then water from another source, such as raw
water, can be used in addition. Since the concentrate is only being used to flush the
filter, it does not matter that it is high in impurities.
5
The use of concentrate, that would ordlnarlly be dlrectly dlscharged to a draln due to Its
high level of impurities, to flush the filter 26 eliminates, or at least reduces, the amount
of raw water that is required for flushing . There is therefore a financial saving as the
cost of raw water to flush the filter 26 is eliminated (or at least reduced), and the cost of
10 disposing of the concentrate is also eliminated (or at least reduced).
After a period of time, all of the sodium ions bonded to the resin of the softener vessel
30, 32 being used will have been replaced with calcium and magnesium ions, and
therefore the softener vessel 30, 32 must be regenerated. In order to do this, a series
15 of valves are actuated so that the filtered water is directed to the other softener vessel
30, 32 to ensure continuous operation of the softener unit 28. The softener vessel 30,
32 is regenerated by filling the vessel 30, 32 with a strong solution of sodium chloride
supplied from the brine tank 34. This causes the sodium and magnesium ions bonded
to the resin to be displaced and replaced with sodium ions. In this embodiment, the
20 concentrate generated by the reverse osmosis unit 14 and stored in the storage tank
72 is supplied to the brine tank 34 through the line 80 where it is mixed with solid
sodium chloride so as to form a strong brine solution. If there is insufficient concentrate
avallable to generate sufflclent brlne, then water from another source, such as raw
water, can be used in addition. Since the concentrate is only being used to form brine
25 solution, it does not matter that it is high in impurities. Once the regeneration of the
resin has taken place, the softener vessel 30,32 is flushed so as to remove the
magnesium and calcium ions from the vessel 30, 32. In this embodiment, concentrate
generated by the reverse osmosis unit 14 and stored in the storage tank 72 is supplied
to the softener unit flushing line 42 and is used to flush the softener vessel 30,32. The
30 concentrate used to flush the softener vessel 30, 32 is then discharged through the
drain 44. If there is insufficient concentrate available to flush the softener vessel 30,
32, then water from another source, such as raw water, can be used in addition. Since
the concentrate is only being used to flush the softener unit 28, it does not matter that it
is high in impurities.
The use of concentrate, that would ordinarily be directly discharged to a drain due to its
high level of impurities, to fill the brine tank 34 and flush the softener vessel 30, 32
eliminates, or at least reduces, the amount of raw water that is required. There is
therefore a financial saving as the cost of raw water to fill the brine tank 34 and flush
5 the softener vessel 30, 32 is eliminated (or at least reduced), and the cost of disposing
of the concentrate Is also ellmlnated (or at least reduced).
As can be seen from the above, using the concentrate from the reverse osmosis unit
14 in other areas of the steam plant where water quality is not as important results in
10 bath financial and environmental benefits. Although it has been described that the
concentrate is used for flushing the filter, filling the brine tank, flushing the softener
vessel and cooling blowdown water, it should be appreciated that a particular steam
plant may not implement all of these uses. For example, in a particular steam plant the
concentrate may only be used for cooling blowdown water, or may only be used to
15 flush the filter. Also, depending on the particular requirements, it is not essential that a
concentrate storage tank is provided if the concentrate can be used "on-the-fly".
As shown in Figure I in dotted lines, instead of providing concentrate to the blowdown
vessel 20 and/or the processing unit 12, concentrate may be supplied to the feedtank
20 (hotwell) 16 and/or the RO inlet 46 of the reverse osmosis unit 14. However, due to the
quality of the concentrate, in particular the high TDS value, any such supply must be
carefully controlled.
Some of the components of the steam plant 10 described above with reference to
25 Figure 1 may already be present in an existing steam plant 10; although configured
entirely differently. Therefore, it may be possible to upgrade or modify an existing
steam plant 10 to use concentrate from a reverse osmosis unit 14 in other parts of the
plant 10, thereby making the steam plant 10 more efficient and environmentally
friendly.
30
Where it has been described that a particular component is in fluid communication with
another component by a particular line, it should be appreciated that this rnay be
directly, or indirectly, and other components may be disposed in the fluid path between
the two. For example, in the above described embodiment the reverse osmosis unit 14
35 is in fluid communication with the boiler 18 through the permeate line 60. However, a
feedtank 16 is disposed in the fluid path between the two, and a further fluid line
62from the feedtank 16 to the boiler 18 is provided.

13
CLAIMS:
1. A steam plant, comprising:
a processing unit arranged to treat raw water;
5 a boiler arranged to generate steam;
a blowdown vessel In fluid communication with the boiler so as to receive hot
biowdown water from the boiler; and
a reverse osmosis unit In fluid communication with the processing unit though an
inflow water line, the boiler through a permeate line, and the processing unit and/or the
10 blowdown vessel through a concentrate line;
wherein in use, the reverse osmosis unit receives treated inflow water from the
processing unit and generates permeate which is provided to the boiler through the
permeate line and concentrate which is provided to the processing unit and/or the
blowdown vessel through a concentrate line.
15
2. A steam plant according to claim 1, wherein the processing unit comprises a
softener unit including at least one softener vessel and a brine tank.
3. A steam plant according to claim 2, wherein In use the concentrate is provided to
20 the brine tank and is subsequently used to regenerate the at least one softener vessel.
4. A steam plant according to claim 2 or 3, wherein in use the concentrate is
provided to at least one softener vessel so as to flush the softener vessel.
25 5. A steam plant according to any preceding claim, wherein the processing unit
comprises a filter.
6. A steam plant according to claim 5, wherein in use the concentrate is provided to
the filter so as to flush the filter.
30
7. A steam plant according to any preceding claim, wherein in use the concentrate
is provided to the blowdown vessel where it Is mixed with hot blowdown water so as to
cool the blowdown water.
14
8. A steam plant according to any preceding claim, further comprising a concentrate
tank arranged to receive and temporarily store concentrate from the reverse osmosis
unit.
5 9. A method of operating a steam plant, comprising:
providing raw water to a processing unit which generates treated Inflow water;
providing the treated inflow water to a reverse osmosis unit which generates
permeate and concentrate;
providing the permeate to a boiler; and
10 providing the concentrate to the processing unit and/or a blowdown vessel.
10. A method according to claim 9, wherein the processing unit comprises a softener
unit Including at least one softener vessel and a brine tank.
15 11. A method according to claim 10, wherein the concentrate is provided to the brine
tanl<; and wherein the method further comprises:
regenerating the at least one softener vessel using concentrate from the brine
tanl<.
20 12. A method according to claim 10 or 11, further comprising flushing the at least one
softener vessel with the concentrate.
13. A method according to any of claims 9-12, wherein the processing unit comprises
a filter.
25
14. A method according to claim 13, further comprising flushing the filter with the
concentrate.
15. A method according to any of claims 9-14, further comprising providing the
30 concentrate to the blowdown vessel and mixing with hot blowdown water so as to cool
the blowdown water.
16. A method according to any preceding claim, further comprising temporarily
storing the concentrate in a concentrate storage tanl<, and subsequently providing the
35 concentrate to the processing unit and/or blowdown vessel.
15
17. A method of modifying an existing steam plant comprising a processing unit
arranged to treat raw water; a boiler arranged to generate steam; a blowdown vessel in
fluid communication with the boiler so as to receive blowdown water from the boiler;
and a reverse osmosis unit in fluid communication with the processing unit though an
5 inflow water line and the boiler through a permeate line and having a concentrate
output, the method comprising:
fluidically connecting the concentrate output of the reverse osmosis unit with the
processing unit and/or the blowdown vessel through a concentrate line, such that
during use of the steam plant, concentrate can be provided to the processing unit
10 and/or the blowdown vessel through the concentrate line.