PLANT SYNOPSIS
The main purpose of DM+UF plant is to supply
de-mineralized water to various systems with the priority to provide for steam
water system for producing steam to run the turbine. The water from the plant will
also be used as jacket water of diesel generators, air compressors and
chillers.
The process employed for DM+UF plant is the simple
ion-exchange method with cat ion bed, anion bed and mixed bed.
The capacity of the Plant is 48m3 per stream for outlet and
inlet is 56m3 per stream.
The Plant employs several chemical and physical processes
to de-mineralized water namely.
1. Dual
Media Filter (DMF) - This process is also called Pressurized
Sand Filter as larger suspended impurities and organic matter are removed in
this process.
2. Activated Charcoal Filter (ACF) – This
process strictly removes chlorine from inlet water as presence of chlorine may
chemically damage the cation resin present in the bed.
3. Strongly
Acidic Cation Bed (SAC) – The main purpose of strongly acidic
cation bed is removal of cation from inlet water.
4. De-Gasser Tank – This particular tank is used for
removal of carbon dioxide as carbon dioxide presence may cause unnecessary load
to the anion bed.
5. Strongly
Basic Anion Bed (SBA) – The purpose of this particular process is as the name suggests is to
remove positively charged anions.
6. Mixed
Bed (MB) – The SAC
and SBA removes the cation and anion from the water but some amount of cation
and anion resins are still distributed within the bed. The mixed bed is mainly
polishing unit to refine the final outlet through SBA.
7. Ultra
Filtration (UF) – This process of Ultra Filtration is a
physical interaction only where no chemical reaction takes place to remove
colloidal silica or non-reactive silica. UF modules are woven fiber filter
which removes the non-reactive silica.
NB:
There are two vessels for DMF, ACF, SBA and MB and three vessels for UF at the
Plant Side.
SYSTEM CONFIGURATION
The
DM+UF Plant Panel have redundant PLCs, meaning that if one PLC goes to stop mode
or shuts down due to any event or situation then the other PLC will take over
ensuring the field input and output are unaffected from the one PLC shutdown. Similarly, even
Ethernet Switches and Power Supply in the Panel are also redundant. The
Ethernet switch used here also have probation of transfer of data from Fiber
Optic Cable. The Ports 7 and 8 are for FO port whereas ports 1, 2, 3,4,5,6, are
Ethernet Ports.
CYCLES IN THE PLANT
The DM+UF Plant can be divided into three sections each
independent of each other. The following flowchart illustrates the section and
their respective cycle.
SECTION
1: This particular
section comprises of DMF, ACF and SAC each having two vessels from which either
of the vessel can be selected for service or backwash cycle.DMF has three
cycles namely Service Cycle, Backwash Cycle and Trip Cycle. There are further
sub-cycles in Service and Backwash Cycle as defined by necessity of process
requirements, each cycle results in operation of valves and pumps at the field.
Similarly ACF and SAC have cycles of Service and Backwash with their further
sub-cycles in each of the respective cycles.
SECTION
2: This section deals
with SBA and MB having two vessels for each for the process with either of the
vessels can be selected for Service or Regeneration Cycle. SBA has three cycles
namely Service, Regeneration and Trip Cycle whereas; MB has only Service and
Regeneration Cycle with each of the cycles having further sub-cycles except the
trip cycle. The cycles results in valve and pump operations at the field.
SECTION
3: This section of UF
has three vessels of which any two can be selected for Service cycle. The UF
section has Chemical Cleaning Cycle and Backwash Cycle apart from service
cycle. These cycles like the other two section also results in valve and pump
operation at the field.
AUTOMATION SEQUENCE AT THE PLANT
The DM+UF is semi automated plant, the following
flowchart illustrates the automation sequence of the plant.
NB:
Section A, Section B and Section C cycle sequence is independent of each other.
DMF, ACF and SAC have two vessels each and each vessel
has Auto and Manual mode. Service cycles require selection of any of the two
vessels and their respective Auto mode of DMF, ACF and SAC. If there is any
kind of fault or interlock issue at the plant then the whole cycle will trip in
Section A. The other vessel of DMF, ACF and SAC can be taken in Manual Mode or
Auto Mode for Backwash Cycle.
SBA and MB also have two vessels each and each vessel has
Auto and Manual mode. Similar to DMF, ACF and SAC Service Cycle, even SBA and
MB Service Cycle requires selection of any of the two vessels and their
respective Auto Mode. The other vessel for SBA and MB can be taken in Manual
Mode or Auto Mode for Regeneration Cycle. If there any kind of field Fault or
interlock issue at SBA or MB then the cycle will trip in Section B when it is
at Auto Mode. The Trip at SBA and MB will not affect other cycles at Section A
or Section C.
UF have three vessels each having Auto and Manual mode.
The Service Cycle at UF requires selection of two vessels and their respective
Auto Mode. The other vessel can be taken in Manual Mode or Auto Mode for
Chemical Cleaning or Auto Mode for Backwash. Fault or Interlock issue at UF
section will only trip UF cycle and will not affect any other Cycles at the
plant.
The Pumps have Auto and Manual Mode; the corresponding
pump must be selected in Auto Mode in the required Cycles to run the cycle. It
can also be operated without cycle operations when taken in Manual Mode. The
Blowers, Valves, Pumps and Analog Inputs from the field has BYPASS probation
included in the system, thus any of them are at fault then it can be bypassed
from the cycles at Start Up or During Cycle without any intervention to
the Actual Cycle Operation.