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m a k e t h e d i f f e r e n c e
Technologies | Marketing | Licensing
ENVI-Marine™ Emission Control
Systems
Contentsi. Pacific Green Marine Technologies
1. The Technology
2. ENVI-Marine™ System Technical Overview
3. ENVI-Marine™ Scrubbing System
4. Components
7. Exhaust Gas Flow
8. System Operating Modes
9. ENVI-Marine™ Competitive Advantages
13. Conclusion
14. Contact Information
Pacific Green Marine Technologies
In 2009 Pacific Green Group acquired the worldwide marketing rights for the EnviroTechnologies Inc. (ENVI) innovative emission control system.
ENVI has designed and has filed international patent applications for wet scrubbing systems whose unique approach makes them highly effective in the removal of particulate matter, acid gases and selected heavy metals from the combustion flue gases of coal, biomass, waste to energy and diesel processes.
The attributes that make the ENVI systems unique include special multiple turbulent scrubbing heads working in series with the capacity to continuously process 100% of the flue gas, a high efficiency horizontal head design, small and flexible footprint, on-demand reagent addition and low capital and operating costs.
With it’s patented technology Pacific Green Marine is able to offer a wide range of emission control systems for ships of all classes anywhere in the World.Our technologies represent the state of the art for marine exhaust gas scrubbing devices.Our business is focused on a cleaner future and our goal is to mitigate emissions from the most pollutant sources on the planet.
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The TechnologyThe Pacific Green Marine research and development program has adapted its new and innovative approach to turbulent wet scrubbing for marine applications that is highly efficient, smaller, cost effective to build and operate and capable of removing a broader range of pollutants in a single pass.
ENVI-Marine™ System Technical OverviewThe ENVI-Marine™ system has definite advantages over conventional water spray exhaust gas cleaners. The patented TurboHead™ foaming bed creates an intense turbulent zone to give superior gas-to-reagent contact in than competitive approaches. This efficiency advantage allows for a more compact and cost effective solution.
Functions by:
• Using the natural alkalinity of seawater to absorb SO2 emissions produced by marine engines
• Post treatment discharge of neutralized sulphur into sea
• Using caustic soda (NaOH) as a supplemental reagent when transiting areas with low seawater alkalinity
Flexible layout due to:
• Patented horizontal head
• Potential for component separation
• Able to configure footprint to fit space available
• Compact footprint due to efficiency
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ENVI-Marine™ Scrubbing SystemThe ENVI-Marine™ seawater scrubber takes an alternative approach to seawater scrubbing by using ENVI’s unique patented TurboHead™ to provide highly interactive contact between the seawater and the exhaust gas in a turbulent zone containing a high amount of surface area for gas/liquid absorption.
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The high energy liquid/gas interaction assures both the residence time and complete interaction required to achieve high efficiency removal of sulphur from the exhaust gas. In addition, the highly turbulent interaction transfers particulate matter from the gas to the scrubber fluid. Marine fuel oil typically has a 0.1% to 0.15% ash content after complete combustion, and incomplete combustion adds carbon and hydrocarbon particulate and oils to that value. A high percentage of these pollutants are captured by the seawater scrubber resulting in a much cleaner exhaust plume.
The pressure required to push the exhaust gas through the scrubbing system is typically not large (e.g. 10-12” w.c.) and marine engines are capable of operating at this back pressure with ease.
ComponentsThe ENVI-Marine™ scrubbing system is comprised of the following components:
Gas Conditioning Chamber (GCC)This chamber uses water spray to quench the exhaust gas to approximately 55ºC.
Scrubber BodyThe scrubber body contains ENVI-Marine’s™ patented TurboHead™. Demisters dry the gas prior to exit to atmosphere so there is less visible plume. The footprint of the scrubber body is variable depending on the configuration of space available. In general, the scrubber is
Figure 2. ENVI-Marine™ General Arrangement
ENVI-Marine™ Placement
*Please note that this layout is specific to a class of vessels and other classes of ship will have alternative layouts depending on space and equipment
POOP DECK
A DECK
B DECK
C DECK
DECK
GRATING
FUNNEL TOP
DIVERTERDAMPER
EXISTING STACK
SCRUBBER
RECIRCTANK
GC HXPBM HX
DAF TANK
DCMODULE
ALKALI STORAGE
TANK
HCCLUSTER
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normally positioned at deck level corresponding to the base of the external stack enclosure.
Because the scrubber heads are horizontal, the scrubber can be configured into any shape. The marine scrubber vessels are made from stainless steel selected for corrosion. To make the best use of available space, the scrubber vessel bodies are rectangular in shape. The footprint required is approximately 1m2 for each MW of main propulsion engine and 1.5m2 for each MW of electrical generation.
Surge TankThe surge tank is a partitioned tank with one side taking the water from the scrubber and the other side taking the solids rich underflow from the first hydrocyclone process.
Recirculation TankThe recirculation tank serves as a reservoir for the raw water supply to the GCC and Scrubber water distribution array. The recirculation tank will take water directly from the sea in open mode or from the surge tank in the case of closed mode. In hybrid mode the water is supplied from both sources.
Heat Exchangers (2)The heat exchangers for the GCC and scrubber fluid distribution are used in hybrid and closed modes only. Raw seawater is used to cool the recirculated scrubber and GCC fluid to maintain a scrubber operating temperature in the range of 55ºC +/- 5º. Seawater used in the cooling process is discharged directly to the sea.
HydrocyclonesBanks of hydrocyclones are used for oil and solids separation. Each system draws from a section of the partitioned Surge tank. The oil is separated from the section containing the scrubber effluent. The solids are separated from the section containing the solids rick underflow from the oil separation hydrocyclones.
Sludge TankThe sludge tank holds the solids rich underflow from the solids hydrocyclone process line.
Dissolved Air Floatation separator (DAF)The DAF unit processes oily water from the first hydrocyclone line and sludge from the Sludge tank. The unit uses the dissolved air floatation technique to separate oil and solids from the water to be discharged.
Oily Waste TankThe oily waste tank holds the residue from the DAF system for removal at a land based facility.
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Effluent Holding TankWhen at sea the effluent from both the DAF and solids hydrocyclone lines is discharged to the sea. When in port or when regulations restrict discharge the tank is used to hold effluent water for later discharge at sea.
Caustic Soda TankCaustic soda is stored on deck in a 20-foot ISO tank configured as a 20-foot bulkhead container. The tank acts as a reservoir for a caustic soda surge tank located in the water processing area below decks.
Continuous Emissions Monitoring System (CEMS)The system includes a Continuous Emissions Monitoring System (CEMS) to monitor and record sulphur emissions on a continuous basis. Access to this information is required by regulatory authorities.
Effluent MonitorA system to monitor the turbidity and temperature of the effluent is installed in the discharge line.
Process Control SystemThe ENVI-Marine™ emission control system is operated through a distributed process control system linked to the ship’s process control and navigation system. Ship engineers use a computer interface to enable scrubber process components to operate automatically. The process control system then operates the system by turning pumps on and off, opening, closing and adjusting valves, and turning subsystems such as the OWS system, disk centrifuge system and the NaOH delivery system. For the most part, once the system is enabled and operational, very little operator intervention is required. SO2 emissions and removal efficiency is monitored and recorded by the CEMS, and effluent quality is monitored and recorded by the water monitoring system. Alarms are configured for exceedances of exhaust gas SO2 concentration and water quality criteria as well as various process parameters.
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Exhaust Gas FlowIn all cases the engine exhaust is ducted to the GCC for cooling by spray quench to a target of 55ºC. The GCC is a downflow device leading to a plenum below the scrubber head. The cooled gas rises through the horizontal scrubbing head where it enters a turbulent zone above the head. The heads are sprayed with seawater from nozzles above to continuously replace the water that overflows through down-tubes into the scrubber sump below. This maintains the alkalinity of the scrubber water as the SO2 is absorbed and neutralized. After exiting the turbulent zone the gas rises and demisters remove any excess moisture prior to the gas exiting the scrubber.
System Operating ModesThe ENVI-Marine™ system is designed to operate in three modes, Open, Closed and Hybrid depending on the sea’s alkalinity and the effluent emission regulations of the waters
Figure 3. ENVI-Marine™ Process Flow
ENVI-Marine™ Process Diagram
ENGINEEXHAUST
CLOSEDMODE
HX
HX
BYPASSDAMPER
SEAWATER
DAFTANK RAW
RECIRCCLEANRECIRC
SLUDGE TANK
OPEN /HYBRID
MODE EFFLUENT HOLDING TANK
EFFLUENT MONITORS
CMS
OWSDC
HYDROCYCLONESNaOHSYSTEM
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in which the ship is located. Refer to figure 3 for components described in the operating mode descriptions.
Open Mode Operation This is considered the standard operating mode for most open-sea operations. In open operating mode, raw seawater is pumped through the scrubber system, absorbing the SO2 and neutralizing it with the seawater’s natural alkalinity. The volume of seawater pumped through the system is greater in open mode than in closed mode to provide enough alkalinity to neutralize the amount of SO2 being removed. The seawater leaving the scrubber undergoes treatment that includes dissolved air flotation of oils and light particulate (soot) and hydrocyclone treatment for removal of heavy particulate (ash). The oily, sooty froth from the dissolved air floatation system is concentrated in the oil water separator (OWS). Clean water from the OWS is returned to the recirculation tank while the concentrated sludge is sent to the sludge tank for later disposal at a shore-side facility. Similarly, the heavy particulate stream from the hydrocyclone underflow is sent to the disc centrifuge for concentration of the heavier solids. The clean water from the disc centrifuge is sent to the recirculation tank and the concentrated solids are sent to the sludge tank. The overflow from the recirculation tank is monitored for pH, turbidity and phenanthrene prior to being combined with reaction seawater from the heat exchangers to further moderate the pH prior to being discharged.
Hybrid Mode OperationHybrid mode is essentially the same as open mode except that in areas where seawater does not contain enough alkalinity to neutralize the SO2 captured, NaOH is added to the seawater to increase the alkalinity so that the pH of the effluent does not exceed the effluent criteria.
Closed Mode OperationClosed mode operation is required in areas where regulations prohibit the discharge of effluents. In closed operating mode, seawater is recirculated through the scrubber with no discharge to the sea. The water is treated using the same processes of dissolved air flotation and hydrocyclone treatment before being recirculated back to the scrubber. Losses of water to stack humidity are made up with fresh water.
Because the scrubber water is recirculated in closed mode, the system is designed to remove heat transferred from the hot exhaust gas and neutralize acids formed by the absorption of SO2. Cold seawater is provided to the heat exchangers to cool down the scrubber water with no intermixing. The acids are neutralized by the addition of NaOH at various points throughout the system.
In addition to the normal generation of sludges from the OWS and disk centrifuge systems, which are directed to the ship’s sludge tank in all modes of operation, the build-up of dissolved solids due to recirculation requires that some water be bled from the system and stored. Tanks designated for this purpose are large enough to hold the volume of bleed required.
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Once the scrubber returns to open mode operation, the effluent tank(s) can be emptied by transferring their contents to the DAF tank for a second round of treatment, followed by discharge along with the open mode effluent.
MaterialsWith regard to corrosion in the scrubber, we have selected the materials of construction very carefully to ensure a long service life for the scrubber. Common stainless steels such as 304L and 316L will not stand up to the service conditions as they are susceptible to pitting corrosion from chlorides at elevated temperatures.
We have consulted with industry experts and specialty steel suppliers to evaluate the options for material selection, and considered a variety of specialty steels including duplex 2205, austenitics 904L and 317LXN, super-austenitic 6-moly AL-6XN and nickel-based C-276 alloys such as Hastelloy. These specialty steels are higher in chromium and molybdenum, or nickel, to increase their pitting and crevice corrosion resistance.
The figure below illustrates the pitting resistance equivalence number (PREN) of various types of specialty steels. The PREN is a predictive measurement of corrosion resistance that the industry uses for design and material selection. In general, the higher the PREN value, the more corrosion-resistant the material. Typically, materials with a PREN above 32 are consider corrosion resistant for seawater as long as the temperature is not too high.
The graphed lines in the figure show that higher temperatures require a higher PREN. Therefore, for the quench zone where the exhaust gas is initially contacted with seawater, we have selected AL-6XN (6% molybdenum super austenitic stainless steel) due to the higher temperature it will experience. For the main scrubber body, which will be subject to temperatures below 40C, we have selected duplex 2205 for its great performance against corrosion.
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ENVI-Marine™ Competitive Advantages
High EfficiencyThe system utilizes ENVI’s patented TurboHead™ to generate a turbulent interaction zone for complete interaction between the sulphur dioxide and scrubbing fluid.
SimplicityThe ENVI-Marine™ scrubber has no internal moving parts. All internal components are fabricated from stainless steel or fiberglass for long service life and are easily accessible.
Efficient Use of SpaceThe ENVI-Marine™ uses 100% of its cross section for scrubbing thus minimizing the footprint required. In addition, the ENVI-Marine™ system is fabricated from stainless steel in a rectangular configuration to make the greatest use of the space available. The scrubber system is equipped with inspection ports and access hatches for visual inspection of scrubber internal areas, and easy access for maintenance. This reduces the time spent diagnosing potential problems and fixing them.
Low Capital CostThe simplicity and smaller size of the ENVI-Marine system results in lower capital costs for the equipment.
Multiple Operating ModesThe scrubber is capable of running on a once through open mode, closed mode and a cost optimizing hybrid mode. It is also capable of running with caustic addition in the open mode in sea areas with lower alkalinity.
Effective Particulate RemovalThe turbulent interaction zone created by ENVI-Marine’s patented TurboHead will effectively remove a significant portion of the total particulate matter and carried in the exhaust gas. This will reduce the visible plume and the associated health risks from particulate.
Computer Control and OptimizationThe system is controlled by a programmable logic controller (PLC) with a graphic interface at the operations station or control room. The system normally operates in automatic mode, but manual control, data logging and trend screens are also be available. Depending on the ship’s communication capabilities, the system can also be monitored and controlled remotely. This allows the operating company and/or Pacific Green staff to troubleshoot any problems from land-based offices.
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The PLC has the capability of determining the most cost-effective operating conditions as established for individual ships and configure the scrubber to operate within those parameters in a hybrid mode.
Fabrication and Installation CapacityThrough its partnership with POWERCHINA SPEM, Pacific Green Marine has the largest fabrication and installation capacity in the world.
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Head area vs fuel consumption - comparison graph
Scrubber water flows - comparison graph
Head Area vs Fuel Consumption
1 MW AUX
9.3 MW PANAMAX
11 MW AFRAMAX
14 MW SUEZMAX
18 MW VLCC
Fuel Consumption - t/d
12
14
16
18
10
8
6
4
2
0100 20 30 40 50 60 70 80
Hea
d A
rea
- m2
Scrubber Water Flows (Pump Power)
1 MW AUX
Wartsila OpenENVI Open
ENVI HybridENVI Closed
9.3 MW PANAMAX
11 MW AFRAMAX
14 MW SUEZMAX
18 MW VLCC
Fuel Consumption - t/d
100
0
200
400
600
800
1000
20 30 40 50 60 70 80
Scru
bber
Wat
er -
m3 /
h
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Closed mode effluent and sludge - comparison graph
Fuel Consumption - t/d
Closed Mode - Effluent & Sludge Produced180
150
120
90
60
301 MW AUX
9.3 MW PANAMAX
11 MW AFRAMAX Effluent
Sludge
14 MW SUEZMAX
18 MW VLCC12
10
8
6
4
2
0 010 20 30 40 50 60 70 80
Slud
ge C
olle
cted
- t/
d
Trea
ted
Efflue
nt -
m3 /
d
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ConclusionFor fleets around the world few retro-fit systems are available on such a large scale and none are more efficient than the ENVI-Marine™ system.
With 2020 IMO regulations rapidly increasing the demand for scrubbers to previously unseen volumes, Pacific Green Marine has entered a joint venture agreement with PowerChina SPEM, a subsidiary of China state owned enterprise PowerChina to ensure Pacific Green Marine has unrivalled manufacturing and fabrication capabilities.
With numerous international manufacturing bases around the World, including Chinese ports Guangzhou, Longshan and Dalian Bay our available facilities rate amongst the World’s largest and have many years experience in specialized marine fabrication.
The Pacific Green Marine system makes perfect financial sense by being able to utilize cheaper HFO, offering an obvious advantage that lends itself to funding packages to effectively allow the technology to pay for itself in a short period of time.
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Contact InformationPacific Green Marine
Part of the Pacific Green Technologies Inc. Group
