Appendix D Overview of the Sea Water Scrubber System - Holland ...

Appendix D
Overview of the Sea Water Scrubber System
The Krystallon sea water scrubber was constructed of very high quality alloy (patents are pending on this
material) and is designed to last the life of the vessel. The scrubber design incorporates numerous other
internal patented technologies to ensure very high mass transfer and scrubbing efficiency. After
scrubbing, the wash water is sent to a multicyclone. This treated wash water is then mixed with
additional seawater to adjust the pH prior to overboard discharge. The main components of the
shipboard system include:
• Water intake through a sea chest.
• Sea water scrubber (called “exhaust gas scrubber” below)
• Multicyclone
• Pumps, Valves, Instruments, and Associated Piping
• Water discharge port
Figure 1 illustrates the basic components of the sea water scrubber system. These elements are
described in more detail below. Appendix C includes the sea water scrubber operations and
maintenance manual.
Figure 1 ‐ Basic Sea Water Scrubbing System Components (Drawing is not to scale)
Sea chest for water
intake
Sea level
Wash water discharge
Reaction water

Water Intake through the Sea Chest
Water is taken aboard a vessel through a device called a sea chest. A sea chest is a rectangular steel
enclosure attached to the inside of a louvered or perforated section of the ship’s hull below the water
line. Water enters the sea chest, and when the valve is open, water passes into the pipe and through
the strainer into the ship, where it is delivered for its intended use. The strainer is cleaned periodically
to remove accumulated solid material (sea weed, twigs, etc). When the valve is closed, sea water does
not enter the ship.
The Sea Water Scrubber
Exhaust gas passes through the scrubber where it is mixed with raw seawater. There are no chemicals
added anywhere in this system. Several stages of seawater and gas mixing occur to ensure high levels of
scrubbing efficiency. The scrubbing cools the gas and entrains droplets of seawater. A “demister” was
installed in order to prevent these droplets of seawater from being carried out of the stack. As the
scrubber was not operated in port pending demonstration of the wash water technology, the demister
was subject to frequent dry operation which resulted in clogging. This clogging problem precluded use
of the demister during much of this demonstration project. To minimize generation of a vapor plume,
the wash water supply in the final scrubbing stage was switched off and it was then used as the
demister.
After scrubbing, the cooled exhaust gas is re‐heated using a hot air injection manifold to change the
relative humidity of the gas from 100% to less than 80%. This prevents a visible plume at the funnel
outlet.
Wash water (the effluent from the scrubber) flows out of the base of the scrubber unit to the
multicyclone below deck in the engine room.
The Multicyclone ‐ Wash Water Treatment Plant
After leaving the scrubber, the wash water passes through a high performance multicyclone, which
separates the particles from the wash water. The pH of the treated wash water is then raised to a near
neutral value by mixing with an essentially equal volume of “reaction water,” (see Figure 1 above)
delivered by a separate reaction water supply line before being discharged overboard to the sea.
This particulate removed by the multicyclone is collected in a chamber in the base of the unit (see Figure
2), from where it is batch ejected to a storage tank (see Figure 3).
Figure 2 ‐ The Multicyclone

Figure 3 – The Sludge Storage Tank
Note: The dimension of the storage tank is approximately 4 feet by 2.5 feet by 3 feet. It holds
approximately 0.65 cubic meters of sludge.

Reaction Water
Reaction water is added to the system after the wash water is treated through the multicyclone. The
function of the reaction water is to neutralize the pH of the wash water prior to discharge overboard.
Reaction water is added to the wash water in nearly equal proportions i.e. approximately 400 tons of
water is pumped up through the scrubber (the wash water) and approximately 500 tons of reaction
water is added after the multicyclone.
Using reaction water to neutralize the pH improves energy efficiency of the system. The pH of the
discharge would be the same whether 900 tons of water per hour were pumped up through the
scrubber or whether 400 tons were pumped up 10 decks and another 500 tons are pumped horizontally.
This system is more than twice as energy efficient than a system which pumps all 900 tons up 10 decks.
Pumps, Valves, and Piping
There are two pumps included in this system. The wash water supply pump is a standard seawater
pump designed to supply sufficient seawater to maintain design efficiency of the scrubber at normal
operating loads of the engine as specified by the engine manufacturer. The reaction water supply pump
is a standard seawater pump designed to supply sufficient seawater to achieve maximum pH in the
discharge.
The system is designed to be self‐regulating. All of the valves are fitted to isolate the system only during
maintenance activities and/or extended shut down. There is no manual operation of the valves during
normal conditions. The valves are designed to cope with the chemical, temperature, and physical
conditions of the wash water and/or engine exhaust.
Piping is manufactured from GRE (glass reinforced epoxy), a very inert material which is easy to handle
and install and has low flow resistance thus saving on wash water pumping energy. GRE piping is
designed to outlast the life of the ship.
Instrumentation and Control
The system operates automatically with the minimal interaction by ship staff; there is simply an “ON”
button and an “OFF” button. The monitoring system is contained in the Human Machine interface (HMI)
and is used to monitor the operation of the scrubber system. After the initial start up, there is little or no
adjustment required. Pressure drop, temperatures and levels are set by the thermodynamics and
hydraulics of the system, and are not controlled. There is a hard wired safety circuit which protects the
engine at all times. The batch ejection from the multicyclone is carried out once per day.
Signals from the various instruments are fed back to the HMI, to give live indication of the operation of
the scrubber. The main indicators include:
• FI100 ‐ wash water flow to the scrubber
• PI103 ‐ wash water supply pressure to the scrubber
• DPI300 ‐ scrubber pressure drop
• LI301 ‐ level in the scrubber

• DPT500 ‐ pressure drop across WT500(water treatment plant)
• Monitoring Manifolds (pH, PAH, turbidity)
• TI301 ‐ temperature at scrubber stack outlet
These data are recorded on a secure recording system. The normal operating parameters for the
system are summarized in Table 2.
Table 1 ‐ Normal Operating Parameters
Measured Value Units Minimum Normal Maximum
Alarm Set
Point
Exhaust Pressures mm H2O
System Back Pressure 0 250 350 300
Exhaust Temperatures
o
C
System Inlet 300 330‐385 400 420
Scrubber Outlet 40 50 60 420
Water Flow Rate Tons/hr 350 390 390
Water Pressures bar
Wash Water Supply 6.2 7.0 8.0 5.5
Reaction Water Supply 1.5 2.0 2.5 1.5
Water Treatment Plant bar
Differential Pressure 2.0 2.5 2.7 2.8
Sulfur Dioxide 1 ppm
Before Scrubber 2 200 770 800 820
After scrubber

Scrubber Exhaust
• ES301 ‐ high emissions leaving the scrubber (CO2/SO2 ratio value set at 65)
Wash Water Discharge
• Low pH in return to sea while in port (pH value set to be 6.5 within 4m of the ships side)
• High PAH in return to sea (set at 50 ppb maximum)
The safety circuit checks the main process parameters of the scrubber system and will shut the system
down in the event of an unacceptable reading. The main operating parameters that are checked are as
follows:
• LS300 ‐ high water level in the scrubber
• DPS300 ‐ high pressure drop across the scrubber
• Operation of the wash water supply pump
• Operation of the reaction water supply pump
• TS302 ‐ high temperature of the scrubber shell
In the event of a malfunction, a signal from the safety circuit initiates a shut down of the wash water
supply pump and also sends an alarm to the HMI. The scrubber will be in a run dry mode, ready for
restarting.