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On a still day in harbour, will the colder exhaust plume sink to ship-deck level and be drawn into the air intakes? |
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The cleaned and cooled gas is potentially hazardous because of lack of O2. What distance from the stack would it be infused with sufficiently O2 to be safe? |
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With the SO2 reacting to the salt in the seawater, how do you propose to deal with the situation when the ship sails in brackish or fresh water? |
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What happens if the seawater-pump for some reason fails, and the silencer is left with no seawater flow, and runs dry? Will the silencer be damaged? |
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If the control fails, and the silencer is filled up with seawater (if this is possible), is back-flow of seawater down the exhaust pipes a possibility? |
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In above case of filled up silencer, will the engine be suffocated in it's own exhaust because of too high backpressure? |
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The silencer will have a peculiar temperature distribution, very hot and dry where the exhaust enters and as cold as the resulting temp where the seawater and the exhaust are mixed, i.e. a span in temp. of about 300 C° in the metal from intake to outlet. How will the metal stand up to this for years? |
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If salinity is continuously monitored and controlled, what happens if the controller fails, are there any safety measures, for instance alarm circuits for salinity? |
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Shipboard controllers are notoriously known for breaking down, because of vibrations. What controller principle do you propose electronic, pneumatic, force-balance or position-balance? |
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Obviously the seawater cannot have it's own bottom-intake, but must be supplied from the ship's normal seawater system. The contaminated seawater could therefore, by some fluke in the system, flow back into the ships seawater system. Does your piping system contain non-return valves? |
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How do you propose to transport and burn this mix of seawater and soot, which will be very hard on a pump? |
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| 1. |
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On a still day in harbour, will the colder exhaust plume sink to ship-deck level and be drawn into the air intakes?
In a properly designed exhaust gas stack system the plume will not sink to ship-deck. Moreover, the plume from our device cannot reach a temperature that is less than ambient. Since the heat flow of all systems onboard ship are relative to the ambient water and air temperatures, it is not possible to produce exhaust which is lower in temperature than ambient conditions. Model results show that a plume, which is saturated in water vapor and only 10C above ambient temperature, will rise to a height that is 60% of the plume rise from an untreated exhaust exiting the stack at 400C. This is due to both the basic physics of plume behavior, and to the considerable energy content of the water vapor in the plume. |
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The cleaned and cooled gas is potentially hazardous because of lack of O2. What distance from the stack would it be infused with sufficiently O2 to be safe?
Standard exhaust gas velocity leaving the stack should be about half of its velocity for a 400C stack with the same mass flow, and the same pipe diameter. The content of oxygen in diesel exhaust is typically between 14-15%, not strictly considered an inert gas. With this as the exit condition, where ambient oxygen concentration is above 20%, the dilution of exhaust to make a plume with 17% O2 (a tolerable indoor air concentration) would be a factor of 2.5. Dilution of this amount would be realized within less than 10m of the stack outlet. It is also worth pointing out that the removal of SO2 and, in particular, soot from the exhaust makes it LESS toxic than an untreated exhaust. |
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With the SO2 reacting to the salt in the seawater, how do you propose to deal with the situation when the ship sails in brackish or fresh water?
Our system, since it only releases a fraction of the recirculated water, maintains a brine solution having higher salt concentration than ambient. This means that sailing in brackish water will not be a major operating concern. Likewise, sailing in estuarine water of slightly lower salinity than deep ocean conditions will not pose a problem. Sailing in freshwater, such as the Great Lakes may require some operational changes regarding the chemistry of the SO2 stripping, such as incorporation of limestone injection. The freshwater scenario will have little impact on soot removal. |
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What happens if the seawater-pump for some reason fails, and the silencer is left with no seawater flow, and runs dry? Will the silencer be damaged?
The unit is designed for a run-dry failure mode, and in itself will not present a problem running at high temperature. In this condition, it will still perform as a silencer, although not as effectively at with water present. |
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If the control fails, and the silencer is filled up with seawater (if this is possible), is back-flow of seawater down the exhaust pipes a possibility?
An independent fail-safe limit switch that will shut down the supply pump if the water level becomes too high guards against this failure mode. In addition, a standpipe is fitted to provide emergency drain should the electronic controls and safety fail. The
physical level of these emergency precautions is well below the height where seawater would reach the lip of the inlet exhaust pipe. |
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In above case of filled up silencer, will the engine be suffocated in it's own exhaust because of too high backpressure?
Gradual plugging of the exhaust is a problem for any component downstream of the engine. This is true for silencer/spark arresters as well as the MES EcoSilencer® System. The fail-safe level control will guard against this problem, and the exhaust backpressure is continuously monitored by the unit's control system. Our experience with similar systems has shown that the unit is very effective at self-cleaning, requiring less maintenance than a hot exhaust. |
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The silencer will have a peculiar temperature distribution, very hot and dry where the exhaust enters and as cold as the resulting temp where the seawater and the exhaust are mixed, i.e. a span in temp. of about 300 C° in the metal from intake to outlet. How will the metal stand up to this for years?
The MES EcoSilencer® is designed as a series of concentric shells. The components that are subject to the highest temperature are at the core of the structure, and the interconnections with the cooler components are done with flexibility in mind, permitting low-stress expansion and contraction between the stages of different temperature. The material specification is a minimum of 20-year service life. All metal in contact with exhaust is high grade corrosion resistance material, for maximum corrosion protection. |
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If salinity is continuously monitored and controlled, what happens if the controller fails, are there any safety measures, for instance alarm circuits for salinity?
The salinity is not a critical parameter, but used as a guide to the required makeup water rate for the controller. Thus, failure of the salinity monitor will not have a big impact on operation, and a fail safe mode of moderate water makeup is suitable, as well as an operator alarm. |
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Shipboard controllers are notoriously known for breaking down, because of vibrations. What controller principle do you propose electronic, pneumatic, force-balance or position-balance?
We have designed a multi-sensor PLC electronic control system. We would discuss alternative systems with individual customers who have other preferences. |
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Obviously the seawater cannot have it's own bottom-intake, but must be supplied from the ship's normal seawater system. The contaminated seawater could therefore, by some fluke in the system, flow back into the ships seawater system. Does your piping system contain non-return valves?
Yes, suitable protection is included to ensure that untreated scrubber water cannot flow into the seawater intake system. |
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How do you propose to transport and burn this mix of seawater and soot, which will be very hard on a pump?
The soot sludge is comparable in its handling characteristics to sewage sludge, and can be handled in the same way, and in fact may be handled in the same shipboard system in some installations where a sewage incinerator is available. |
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