Multi Inlet scrubber units, STI-TN-20170919-1

After some project experiences, Sox scrubber system from STI has been found to be effective in terms of installation space, weight, and power consumption. Our experience is to have one scrubber unit per each exhaust gas pipe; so called as “In-Line system with Single inlet”. This has been found to be useful when the installation takes place on existing ships as scrubber units can replace silencer units so that the amount of installation work and funnel casing modification work can be minimum.


The situation becomes a little different when comes to new building projects. Having a ‘large’ scrubber unit to accommodate exhaust gas flows from various diesel combustion units have some advantage over installing as many scrubber units as the number of diesel combustion units. Of course, there are some different considerations are to be made, like by-pass lines, isolation dampers, etc. This type of scrubbers are called as “In-Line system with Multi inlet”.


STI has modified its own scrubber design from “In-Line system with Single inlet” to “In-Line system with Multi inlet”. As a result, this is made as a new line of scrubber design together with the existing designs. As the scrubber units from STI are of “In-Line type” design, we call the new design as “Multi inlet system”.


Multi Inlet scrubber units are found to have some advantages of reducing the ‘overall volume’ of scrubber units installed onboard as the design is made by taking the operation modes into account. It, as a result, reduces overall installation weight as well as cost.


System sizing for multi inlet scrubber units are not very straight forward as there are many issues to be checked in advance. For example,

  1. Number of diesel combustion units to be connected to the scrubber unit.
  2. Operation modes (ex. Sea going, Port, Maneuvering, Cargo cooling, etc.) for the scrubber sizing and utility sizing
  3. Considerations for the bypass lines by regulatory requirements? and/or maintenance point of view. (For the case of the scrubber system design from STI, bypass pipes are not necessary as it can be switches between “dry operation” and “(wet) operation” without making any changes.)


STI is pleased to include some design cases to help customers to have some ideas about scrubber unit size, weight, and utilities as below.


In-line, Multi Inlet Scrubber Project Cases (19 September 2017), STI reserves the copyright.



This is a 3D rendering image of an In-line Multi Inlet Scrubber unit for Case 1.


Multi Inlet Scrubber – Case1

Please feel free to contact STI for additional information to deal with the condensates from scrubber system.?


19 September, STI

Technical Note; Corrosion resistance of Stainless steel 316L as a scrubber material, STI-TN-20170818-2

This is a STI Technical note on the Corrosion resistance of 316L Stainless steel as a scrubber material,?STI TN Corrosion resistance of SUS316L 18Aug2017

In this technical note, we have shown the corrosion rate of SUS316L material in the presence of sulfuric acid as per the weight concentration in %. Expected annual corrosion of the scrubber body, when SUS316L is used, is ~0.03mpy, corresponding to?0.000762mm/year of corrosion speed.


The corrosion speed depends on the weight concentration of sulfuric acid during scrubber operation. STI has shown that it is in the range of ~10-4% of weight concentration of sulfuric acid, which is well below the concentration ranges where other types of stainless steel material like duplex, super duplex, etc.


As a summary, SUS316L is good enough to make marine SOx scrubber units considering the weight concentration of sulfuric acid (being very low) and the operation temperature of <100degC.?

No more debate! IMO sets the Global Sulfur cap of 0.5% from 2020 (24 Nov. 2016)

After more than 10 years of discussions, International Maritime Organization (IMO) finally set the global sulfur cap of 0.5% to be in place from 2020, during its?Marine Environment Protection Committee (MEPC), meeting for its 70th session in London during 27~28 Oct. 2016. (See the press release from IMO here.)

“Regulations for the Prevention of Air Pollution from Ships”, MARPOL Annex VI?adopted on 19 May 2005, which has been updated at later meetings. Regulation 14 of this guideline is about controlling SOx emission from marine diesel engines from 1)?All ships of 400 gross tonnage, 2)?Fixed or floating platforms (drilling rigs) and 3) Floating craft and submersibles.

The regulation 14 suggests the fuel is to be of ‘clean fuel’ with?low sulfur contents. As an alternative to using ‘clean fuel’, MEPC allows exhaust gas cleaning systems like ‘scrubbers’ to clean the emissions before the exhaust gas is release to atmosphere.

SOx scrubber systems from STI is a result of more than 10 years of development, onboard tests, and actual installations onboard ships. STI’s SOx scrubber system has?following features,

  • in-line system that can replace existing silencers,
  • dry/wet run without any provisions to switch the modes,
  • waste water treatment to comply with discharge water requirements,
  • compact design with low water consumption,
  • continuous emission monitoring system (Scheme B) as standard but Scheme A configuration is available
  • all-in-one control and monitoring system with independent emergency shutdown system
  • various configurations of open/close/hybrid operation as per requirements.

SOx scrubber system from STI is custom made for each project. STI is ready to provide technical and commercial proposals.

For any inquiries about the SOx Scrubber system inquiries, please contact STI at



Project financing for SOx scrubber projects (11Aug2016)

Project decision about SOx scrubber installation to any shipping companies is not easy at all. Ship owners/operators should consider all aspects of technical, operational, and financial issues.


Among these, technical issues may be the easiest one as SOx scrubber manufacturers provide detailed project proposals including various technical issues. Project review from operational point of view have to do with fleet planning, voyage schedule, fuel price, and related operating costs. Ship owners may find the financial issue as the most difficult one because SOx scrubber projects requires big investment in the beginning. ROI of the SOx scrubber projects with STI is considerably short, but upfront investment is still a big burden to the client.


We learned that Korea Export and Import Bank ( offers “Export Facilitation Loan“, and SOx scrubber projects may?fit into the category. For those Ship owners/operators who are interested in the SOx scrubber project financing, STI can check?the possibilities and eligibilities about the project opportunities.


Any inquiries about the SOx Scrubber system inquiries, please contact STI at


10 August 2016


Join forces; SOx scrubber and Ballast Water Treatment System? (5Aug2016)

Combining SOx scrubber system andBallast water treatment system (BWTS) will benefit both systems.


SOx scrubber system uses seawater and discharges wastewater with decreased pH level. It is because MEPC puts pH criteria in the washwater, Section in MEPC 184(59).


For Ballast water treatment system (BWTS), low pH in the incoming seawater will help the system performance within the electrolysis.


Having some amount of washwater, of course PAH and turbidity should be controlled, stored onboard and mix with the ballast water to lower the pH value would be a way to improve the performance of BWTS.


Being able to have some storage capacity of washwater from SOx scrubber units can give a room to deal with sulfates in solid form, especially when operating in closed loop mode.


This is a preliminary idea to improve system performance and operability of SOx scrubber system and BWTS by combining them.


STI is looking for ways in this way.


Please feel free to contact STI for any questions about this issue.


Aug. 2016



ROI estimation for SOx scrubber projects (10Jul2016)

As SOx scrubber installation and operation are costly projects requiring heavy investment, knowing what to spend and what to save. For this purpose, STI provides ROI (Return of Investment) estimation for the SOx scrubber installation project?for clients. There are some parameters to be given from the client. Following is the list,

  • Bunker price (especially the difference between LSF and HSF matters)
  • Annual fuel consumption (to be divided by the time spent within and outside of SECA)


Once above parameters are given, ?estimation for the scrubber sizing and related project cost can be made. From the sizing and system configuration, estimation of operating cost including consumables and additional power consumption can be made. For the general maintenance cost for the scrubber system, STI usually sets as 5% of the initial equipment cost, but this is purely superficial number that can clients can adjusted?based on the experience or company guidelines.


STI has generated lots of ROI estimations for various clients, and usual ROI is 1~2 years from installation. For some big ships, the ROI is less and ships with small engines has longer ROI period.


Please feel free to contact STI to get initial project estimation for SOx scrubber installation and operation on your fleet.


10 July 2016, STI

Bunker price vs. ROI estimation for SOx scrubbers (30Jun2016)

Bunker price between high sulfur fuel and low sulfur fuel has been always significant.

  • Price difference was USD150 in Jan 2016, and is USD200 at the end of June 2016.
  • The ratio (=(LS-HS)/HS) was?100% when the price level the lowest in Jan 2016, and is 80% at the end of June 2016.


Whether the bunker price is low or high, price difference between HSF and LSF always exists. Installation of scrubber systems has been always an option for ship owners operating in SECA. The only difference is the Return of Investment (ROI) period that is set by the “Fuel Price Difference” and “Equipment/Installation/Maintenance Cost”.


SOx scrubber system from STI has always been a practical option for shipowners to stick to burning HSF in SECA while complying with the MEPC requirements, which has been due to the competitive equipment cost?and lower installation cost.


STI welcomes any inquiries for ROI estimation for ships operating fully or partially in SECA. STI can generate ROI estimation for specific ships when we are given with some information from shipping companies like,


  • Engine power (kW)
  • Time spent in SECA per year (hour)
  • Voyage time per year (hour)


Please feel free to contact STI for above inquiries as well as inquiries for scrubber systems in general.


30 June 2016. STI

EIB invests to lower emissions from ships (30Jun2016)

EIB investerer i mindre udledning fra skibe

EIB investerer i mindre udledning fra skibe

Mandag 20. juni 2016 kl: 15:22


Bestyrelsen for den europæiske investeringsbank, EIB, har godkendt en samlet investering p? 7,4 milliarder euro, hvoraf de tre milliarder skal investeres i udvikling af renere transport og energi. Der er tale om 17 forskellige projekter, blandt andet udvikling af nye vindmøller i Tyskland.

Nok s? interessant er det dog, at der skal investeres en milliard euro i initiativer, der er med til at reducere den skadelige udledning fra den europæiske skibsfart. Der er b?de tale om investeringer i nye energieffektive teknologier samt finansiering af retrofitting af eksisterende skibe samt finansiering af udviklingen af nye miljøvenlige skibe.

Alle projekter skal dog først godkendt af EIB’s bestyrelse før, at der kan indg?s nogle endelige l?nekontrakter.

Kilde: EIB