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MDO or MGO upgrade

The switch-over to lighter fuel types like Marine Diesel Oil (MDO) or Marine Gas Oil (MGO) requires monitoring and some modifications to the burner and fuel systems.

Download Aalborg Solutions No. 12 for more information:  


MDO or MGO upgrade



1. Is this principle applicable to Aalborg Industries boilers?

When operating on a lighter distillate fuel than originally intended, the complete boiler/burner should be carefully examined by authorized personnel as this is not just a matter of complying with legislation but also a serious matter of safety.

In order to give the boiler the optimum combustion in the safest way, Aalborg Industries has made an upgrading kit which will ensure highest possible operation safety and meet the revised technical specifications.

2. If yes (i.e. MGO burning with air atomizing is possible), please advise how much, if any, the boiler performance is affected for all boiler loads.

It is of course possible to operate the burner with air atomizing, but the recommended atomizing medium is steam as it ensures a more homogenous atomizing (due to the expansion of the steam) and air fuel mixture. Further, air atomizing requires a fairly high amount of compressed air and for a KBSA/D burner (type 1900) this typically amounts to 169 kg/hr per burner at 6 bar(g).

It should also be noted that atomizing by air could have an effect on the excess ratio, thus the air/fuel ratio needs to be adjusted during IGS operation.

3. In case of air atomizing, it is our understanding that the burner lance will remain unchanged, while only the automation system has to be updated and the FO burning pumps (able to handle low viscosity distillates) installed in addition. Please confirm.

If compressed air is utilized for atomizing, the existing burner lance can be utilized, but this is only a minor part of our upgrading proposal.

4. Referring to “Aalborg Solutions No. 12” we understand that only one additional FO burning pump - able to handle low viscosity distillates - is recommended to be installed. Please confirm.

For upgrading of existing systems we recommend installing one additional pump unit incl. 100 % standby capacity, this is to ensure that the redundancy of the boiler plant remains intact.

5. Considering that in your proposal for retrofit package, you already recommend the additional installation of FO burning pump (able to handle low viscosity distillates), please explain why you also recommend the installation of a chiller. Is there any other equipment that needs to be protected? If yes, please describe in detail. Do you believe that the flow meter of the boiler can be affected by the low viscosity gas oils ( i.e. 1.5 cSt)? If no, it is our understanding that either (a) addition of FO burning pump, or (b) fitting of chiller can be considered as alternatives. Please confirm.

Based on our specification, the “retrofit” fuel oil pumps need to be able to pump MGO down to a viscosity of 1.1 cSt at 60 °C. On some occasions it may be required to install an additional cooler in the re-circulation line in order to minimize the temperature increase produced by the oil pump especially under continuous low boiler load conditions.

6. Capacity requirements for air atomization: in such case, we intend to install onboard a pair of air compressors. For sizing correctly subject compressors, we understand that the “max. atomizing air consumption”, as per your manuals (normally found in Technical Data in the Burner Section, edit.), will be used. Otherwise, please advise. We intend to use 7 kg/hr compressors. Please confirm.

You should be able to find this in the instruction manual, but if in doubt, please feel free to contact us. But considering that the installation and operation costs for this solution will be much more costly than a replacement of the lance and taking into consideration that atomizing steam is considered the best atomizing medium, it should be reconsidered going in this direction.

7. Is there any restriction as to the flow of air to the burner? Is any fluctuation anticipated to affect the pattern of the flame and the performance of the boiler and how can we avoid such abnormality? Do you have any recommendations on the need and sizing of air receivers?

Concerning the sizing of an air receiver we do not have any recommendations, but the air flow should be constant, or else the flame will fluctuate. For all boiler/burner plants (KBSA/D) delivered after year 2000, the atomizing medium flow is controlled by means of a control valve.

8. What is the recirculation effect, or in other words what might be the gas oil recirculation temperature effect, given that this is directly influencing the fuel pump lubricity due to lower viscosity? Furthermore, please advise the ratio of re-circulated fuel as well as the temperature of the return fuel.

The temperature increase of re-circulated fuel varies with the FO flow to the burner (the FO pump will pump a constant amount which is either going to the burner or in the recirculation line), and the temperature increase in the tank will vary dependant on the boiler load condition, with the largest temperature increase during low load conditions due to high oil recirculation amount.

9. Is there any recommendation with regard to minimum gas oil inlet temperature to the burner?

In general, we do not have a minimum inlet temperature, but normally only specify a maximum viscosity of 15 to 20 cSt at 50 °C.

10. How many flame scanners do we need in this particular modification (air atomizing)? Presumably, 2 for main burner and 1 for ignition burner. Please confirm.

Based on our upgrading suggestion, we recommend two for the main burner and one for the ignition burner.

11. Please explain in detail all the necessary modifications that are to be performed on the Boiler Local Control Panel and control system software.
- Does the Air/Fuel ratio curve need to be modified for MGO operation and if so, how will the switching between HFO/MGO burning modes be done in the software?
- How is purging affected compared to HFO operation and do we have to make new permanent purging setting in the so-called “MGO mode”?

For our steam atomizing burner systems, the software needs to be upgraded to the a new version with enhanced safety features, which among other things include a flame scanner solution on the ignition burner, post-purge sequence during normal stop procedure and modified stopping procedures when the boiler is stopped due to safety aspects.
The air/fuel curve needs to be re-adjusted in order to achieve the optimal combustion on the new fuel.

12. Chiller:
(a) Referring to your proposal for retrofit package, with regard to installing a chiller on the fuel inlet side, please advise the Temp In, Temp Out and flow rate values used for sizing of the chiller.
(b) In case we introduce the idea of a “chiller” fitted in the common outlet line from the gas oil service tank and the outlet temperature of the gas oil is i.e. 5 °C, what is your opinion as regards the whole operation and the recirculation effect on the inlet temperature of the gas oil to the burner? Will it remain at levels below 40 degrees, ensuring that viscosity at the worst will be 1.5 cst?

A chiller located in the re-circulation line shall match the heating of the oil, and if it is designed to absorb the energy used by the FO pump, then the size will be sufficient. The cooling water flow rate will depend on the actual (design) cooling water system/temperature layout (both fresh water and sea water coolers are available).
A chiller located at the common outlet of the tank must be designed depending on the amount of fuel in the tank (considering what will be the lowest amount available), expected max. tank temperature, other systems contributing to the heating up of the tank and the actual (design) cooling water system/temperature layout. Further it is of utmost importance to be observant of the pressure loss over the chiller in order to avoid any cavitations at the oil pumps.

If you have further questions or need more information, please contact our Global After Sales service by e-mail gafs@aalborg-industries.com or phone +45 99 30 45 00.


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