Marine SCR Systems

NOx reduction for a
cleaner shipping

H+H Engineering & Services meets every
challenge and delivers flexible NOx reduction
solutions for your application.

H+H SCR Technology for lower NOx emissions
H+H SCR Technology for lower NOx emissions

NOx Reduction by SCR Catalyst on Ships

NOx reduction for a cleaner shipping

H+H Engineering & Services meets every challenge and delivers flexible NOx reduction solutions for your application. 
For perfect final results, we focus on excellent planning. For us, customer satisfaction begins with consultation and
with detailed planning that takes your requirements into account from the very beginning. This is how we create innovations
and solutions that are perfectly customized to your needs and guarantee reliability for our customers.

Perfect planning from the very beginning

This is ensured by competent employees who support you throughout the entire project phase and
combine extensive know-how with the best advice.

H+H SCR Marine Systems will be different approach for new building and retrofit systems.
Thanks to almost 30 years of experience in this highly specialized field of business,
gained from more than 300 ships in service we can provide the perfectly engineered solution for a perfectly
engineered ship – this all with competitive price level.

The high performance SCR Systems by H+H are for new build and retrofit vessels for operation on
GO, MDO and HFO being designed to meet Tier III NOx, U.S. EPA Tier 4 Final and Stage V limits.

Why H+H makes the difference and should be your first choice for marine SCR solutions

» Compatible for all engines from 200 kW to 60 MW
» All components made in Germany – quality out of one hand!
» Fully extruded catalyst designed by H+H with best mechanical stability
» Urea mixer and 2-phase nozzle for fine atomization and even distribution of urea
» In-house competence of PLC Programming based on Siemens
» High spare parts availability
» Worldwide service locations and representations

» Contact us

Overview of the H+H SCR exhaust gas cleaning system for marine propulsion systems with individual components

Flexibility in design 

Design is made in house

Our engineers are trained to design the catalyst housing tailor-made to adapt the SCR
system to your specific space requirements.

Very good mechanical stability

Catalyst design by H+H

Specific know-how and well experienced.
Easy transport, handling and installation.

» Catalyst service


Staff is trained by catalyst manufacturer

No catalogue solution
The in-house catalyst design allows us to adapt backpressure to the special project
needs. Vertical or horizontal reactor design for easy installation and highest flexibility
inside the ships hull.


Fit equipment in ship

No ship built around equipment
H+H Marine SCR system offers the possibility to combine the catalyst housing or
the urea injection unit with a silencer to optimize space. The special designed
mixing and urea injection unit allow very short distance from nozzle to catalyst.
 – Bulletproof due to In-House CFD analysis –


Small solution for Bypass

One ship – one engine
H+H Marine SCR comes with an integrated bypass solution.
This is class demand on single propulsion projects.


Adapting is our expertise

Enabling retrofits and newbuilds
H+H Marine SCR has no other than technical and chemical operation limits, thus we are
able to deliver systems that are in compliance with IMO Tier III, EPA Tier 4 and Stage V
emission limits – also on existing ships!

An SCR catalyst housing with flexible dimensions

Flexible Design for every installation situation on
your vessel!

Emission laws

Ship engines produce harmful nitrogen oxides during combustion. These emissions from maritime shipping have serious consequences for human health. For this reason, strict national and international legal requirements must be observed. The NOx limits are being reduced step by step by the IMO. These limits apply in the so-called ECA (Emission Control Area) zones. There are already plans to expand the zones. In Norwegian waters, a tax on NOx emissions is due. The NOx Fund (www.nho.no) raises a tax and finances the installation and operation of measures to reduce emissions.

The Environmental Ship Index 

» Learn more

Global IMO Tier III NOx Regulations

» Learn more

Differentiated Port and Fairway Dues

» Learn more

NOx Tax and NOx Fund

» Learn more

Global references speak for themselves

Our References

  • Marine SCR Systems


    AKOFS Seafarer  

    Engine Producer:

    Type: 6L32 / 8L32
    Power: 2880 / 3840 kW
    Fuel: MGO

  • Marine SCR Systems


    Hovden Viking  

    Engine Producer:

    Rolls Royce
    Type: C25:336LP
    Power: 1900 kW
    Fuel: MGO

  • Marine SCR Systems

    Fish Farming


    Engine Producer:

    Type: 3512C
    Power: 1350 kW
    Fuel: MGO

  • Marine SCR Systems

    Wind Supply Vessel

    Edda Passat  

    Engine Producer:

    Type: 16V4000M63
    Power: 2000 kW
    Fuel: MGO

  • Marine SCR Systems


    Silja Symphony  

    Engine Producer:

    Type: 8R32E
    Power: 3200 kW
    Fuel: MGO

Baatbygg AS

Kjell Inge Sjåstad – Managing director – Båtbygg AS

We have realized challenging SCR projects with H+H and could successfully finish all of them. Their special expertise in flexible catalyst design and small SCR systems was a big advantage on projects like Johan Hjort retrofit. 

Solstad Offshore ASA

Gunnar Berge – Technical Superintendent – Solstad Offshore ASA

Meanwhile I am working with SCR systems by H+H for more than ten year. H+H was always able to ensure quick support whether in questions during new building phase, or afterwards when troubleshooting, service or spare parts were needed. People at H+H  have always been my first point of contact in all questions about SCR systems.