Advanced Diesel NOx Reduction

ADNOX for Marine Diesel Engines

SCR with Diesel oil as Reductant
– Patent applied

Reduction of NOx by use of a Multi functioning Catalyst and Diesel Oil – More than 80% NOx Reduction – with Increased Plant Efficiency

Injected Oil is converted to Heat – More than 90% Heat can be recovered – To be used for electricity or water production

ADNOX offers a new type of SCR system for NOx reduction in the exhaust from diesel engines. The ADNOX system uses diesel oil as reductant and the NOx reduction completely fulfills the IMO TIER III requirements. The oil injected is converted to heat, that can be recovered and used for production of steam, and used for the production of electricity. The cost of oil corresponds to the cost of urea for an urea-based SCR system. The ADNOX SCR system can be used on all diesel engines, ranging from 2-Stroke to 4-Stroke and marine to power plant applications.

The system is patented, and an Approval in Principles has been achieved from DNV-GL.

ADNOX System for Reduction of NOx from marine diesel engines.

The ADNOX System is made for reduction of NOx in the exhaust from marine diesel engines. A Sys- tem made to fulfill IMO TIER III conditions or any specific customer requirements. For IMO conditions see Attachment.
The ADNOX System is a catalytic system (SCR) using Marine Diesel Oil or Marine Gas Oil for convert- ing NOx to N2 and H2O; The ADNOX system is available for 4-Stroke as well as 2-Stroke diesel engines of different sizes.
The injected oil is cracked, takes part in the NOx conversion and is converted to heat. More than 95% of the lower heating value of the injected diesel oil can be recovered.
Patent is applied for the ADNOX System. An “Approval in Principles” is achieved from DNV-GL, ensur- ing the ADNOX system can be used without compromising safety.

Using the ADNOX System, the temperature after the Reactor is increased around 55 °C compared to reactor inlet temperature. I.e. the temperature at turbocharger turbine inlet after mixing with the bypassed air is increased. The surplus energy is bypassed using valve V3.
The introduction of the ADNOX System into the 2-Stroke diesel engine requires an Environmental Control System to control valve positions., supplied as part of the Control Unit.

1. ADNOX System Compared to urea-SCR

The until now most commonly used NOx reduction System is the Urea-SCR System. In the following, we will compare the ADNOX System to the urea-SCR as frequently used:

The main differences between the ADNOX- and the Urea-SCR system are:

  • The ADNOX System does not need an extra tank for reactant (”Urea tank”)

  • The ADNOX reactor including catalyst has a 40% lower weight than a reactor with extruded catalysts – corresponding to 1300 kg for an 2,500 kW diesel engine;

  • The ADNOX system does not need a long evaporation and mixing pipe, especially important for 2-Stroke diesel engines;

  • The ADNOX System does not have the potential problem of precipitation of urea on the pipe wall, blocking the catalysts when dropping of; Either Ammonium sulfate or ammonium bisul- fate can damage the catalyst system;

  • The ADNOX System produces heat. Therefore no increase in specific oil consumption is re- quired on 2-stroke engines;

  • The ADNOX System converts the injected oil to heat. In a standard ADNOX System up to 85% of the Lower heating Value can be recovered in an exhaust gas boiler, and used for produc- tion of steam, water or electricity; With an Oxidation catalyst installed up to 100% of the heating value of the injected diesel oil can be recovered – increasing the total plant efficiency

2. The ADNOX-NOx Reduction Process

The System starts injection of diesel oil, at an exhaust temperature of 350 °C . After a period of oper- ation, the ADNOX System can operate, at an exhaust inlet temperature of 320 °C, due to the heat formed.
In the exhaust, the oil evaporates and is evenly distributed in the exhaust, when reaching the first catalyst layer.

The ADNOX catalyst is a multi-functioning catalyst, having following main functions,

  • Cracking;
  • NO oxidation;
  • Heterogeneous NOx conversion and
  • Homogeneous NOx conversion

3.0 The ADNOX – System

The standard scope of supply includes;

  • SCR Reactor and Instruments;
  • SCR Catalysts;
  • Soot Blowing System;
  • Pump and Dozing Unit;
  • Injection Unit;
  • Control and Safety System;

As options:

  • NOx analyzer and sensor;
  • Air compressor station;
  • Silenser;
  • Heat recovery Boiler;

Other necessary items:

  • Expansion bellows;
  • Piping and cables between units;
  • Insulation;

A simplified arrangement drawing is shown on Fig. 2

3.1 SCR Reactor

One reactor per diesel engine up to 20 MW engines for 4-Stroke diesel engines, hereafter two reac- tor units per engine. Reactors have a circular cross section with inlet and outlet cones, all in black steel. The size for a 2.5 MW 4-stroke diesel engine is shown in Attachment 2.
The Reactor have two to three service openings through which the steel-boxed catalysts are inserted and removed. The steel cassettes are placed on steel structures.

Temperatures are measured at reactor inlet, at reactor outlet and between the two first service openings. Additionally, a temperature switch is installed at reactor outlet, causing a shut down if the reactor outlet temperature is above 520°C.

Pressure is measured at reactor inlet and reactor outlet. If the pressure difference exceeds the pres- sure difference limit, the interval between soot blowing is decreased and an alarm sounds.

For 4-stroke diesel engines, the Reactor can be integrated with a Silenser and a spark arrestor. Here- by, the total building length is reduced and the total pressure difference is reduced.

SCR Catalysts

The catalyst powder is coated on corrugated ceramic blocks of 150mm x 150 mm in cross section area. The blocks are boxed in steel frames, collected in four parts per layer, easy to install and re- move.
The base material of the catalyst powder is Cu-ZSM5 with metals added. The expected lifetime is up to 20,000 diesel engine operating hours. If a NOx analyzing system is included, and a service agree- ment is entered, ADNOX A/S – via the Internet – will monitor the activity, and supply and exchange catalyst blocks as required.

Soot Blowing System

The soot blowing system includes a pressure vessel and rapid opening solenoid valves keeping up- stream surfaces clean. The soot blowing system is operating, whenever the diesel engine is operating. The blowing takes place with fixed intervals set by the control unit.
The air is supplied from the on-board service air system. The air supply has to be in operation when- ever the engine is running.

3.2 Oil Pump and Dozing Unit

The Oil Pump and Dozing Unit is located near the diesel oil tank. It pumps oil from the tank to the Oil Injection Unit located upstream the Reactor and injected via air controlled nozzles. The oil pressure is fixed. The air pressure controls the oil amount injected and the Control Unit regulates the air pres- sure as function of Diesel Engine Load.

The main components are an electric motor driven oil pump upstream of which a filter is installed. From the pump, surplus oil flows back to the diesel oil tank via a return pipe. A flowmeter measures the injected oil and a pressure gauge measures the oil pressure. Hereafter, the oil line is split into two lines, each with a solenoid valve, supplying oil to the injection unit.

In addition to the oil line, an air-line is included in the Pump and Dozing Unit. After an air pressure gauge, the air-line is split into two lines. On each air- line, control valves controlling the air-pressure of the injection nozzles.
A removable steel cover encloses the Pump and Dozing Unit. If an oil leak happens, the oil is flowing to the oil leak detector, which gives an alarm. The leaked oil ends up in the waste oil tank.

The Pump and dozing unit can be placed as a stand-alone unit or supported by a tank wall

3.3 Oil Injection Unit

Oil is injected into the exhaust through a number of air-controlled nozzles. The Control Unit controls the injected oil amount as function of the diesel engine load by regulating the air pressure to the nozzles.
Each oil nozzle is placed at the end of a lance. Each lance is enclosed in a protection pipe. The lance is flanged to the protection pipe, and the flange is enclosed in a steel box. Leaked oil – should any occur – is piped to the Pump and Dozing Unit, as part of the oil leak detection system.

When oil injection is stopped, dump valves are opened and service air is removing remaining oil in the nozzle and lance to the waste oil tank. After the removing of oil, the dump valves are closed and a small amount of service air flows through the nozzles until the engine stops.

3.4 Control Unit

The Control Unit controls the ADNOX System. When in RUN Mode the System starts automatically when the Diesel engine starts – and stops when the engine stops.

In addition to the PLC based system, a hardwired safety system is included, ensuring the system is safely closed, in case of a power loss or a PLC failure.

The injection of oil is controlled as a function of the diesel engine load. The Control Unit also controls the soot-blowing system.
The PLC system is controlled from a touch screen. The PLC is enclosed in a cabinet, where all cables are entered. The Cabinet is placed close to the Reactor.

4.0 Operation Conditions

Pressure loss

Under normal conditions, the pressure loss over the ADNOX Reactor is max 12 mbar at 100% diesel engine load.

Exhaust temperatures

The maximum temperature from the diesel engine is expected to be 450°C. The oil injection starts at a temperature of 350 °C. After a running in period the ADNOX System can operate, at an exhaust temperature down to 320°C.

Diesel oil consumption

We assume diesel engine operates in accordance with IMO TIER II conditions (See Attachment Figs. A1.1 and A1.2). By including the ADNOX System, the IMO TIER III can be obtained. At 75% engine load, said reduction requires an oil amount of 15 L oil/MWh (around 7% of the oil used by the diesel engine).

Air quality, pressurized Air

The service air supplied for the ADNOX system must be dry and clean. According to the specifications in ISO 8573, purity class 3 with respect to particles, purity class 2 with respect to oil and purity class 5 with respect to water.

5.0 ADNOX for 2-Stroke diesel engines

On 2-Stroke diesel engines, the ADNOX reactor has to be installed between exhaust gas receiver and turbocharger turbine inlet, to reach a temperature closer to the required operating temperature for the ADNOX System (See Fig. 3). Due to the location, the ADNOX system is an integrated part of the diesel engine. The extra installed heat capacity means the ADNOX Reactor shall be bypassed, during start and stop of the diesel engine.

Furthermore, due to the low exhaust temperature, at lower engine loads air from the air receiver has to be bypassed to the turbocharger turbine inlet (Valve CBW on Fig. 3). Due to the reduced air amount, the exhaust temperature is increased up to the level required by the ADNOX System.

Using the ADNOX System, the temperature after the Reactor is increased around 55 °C compared to reactor inlet temperature. I.e. the temperature at turbocharger turbine inlet after mixing with the bypassed air is increased. The surplus energy is bypassed using valve V3.
The introduction of the ADNOX System into the 2-Stroke diesel engine requires an Environmental Control System to control valve positions., supplied as part of the Control Unit.

5.1 ADNOX- HP Reactor

ADNOX High Pressure reactors are designed for a pressure of 5 barg and a max. operating tempera- ture of 575 °C.
At engine sizes >25MW, two reactors are required.

6.0 Heat Recovery

The oil injected after the cracking – as part of the NOx conversion – is converted to heat. Due to the cracking to shorter hydrocarbon connections, the lower heating value (LHV) of the short HC connec- tions is up to 8% higher than the lower heating value of the MGO injected.
On a 4-stroke diesel engine, with a Particulate – oxidation-catalyst installed downstream the SCR catalysts more than 95 % of the lower heating value of the MGO injected, can be recovered and con- verted to steam and/or electricity.

On a 2-Stroke diesel engine a surplus energy is created upstream the turbocharger –turbine. The surplus energy is bypassed (Valve V3) and either used in a power turbine or for production of extra steam at a higher quality, which can be used for extra power production.

For both engine types, the surplus heat can be used for increasing the Power Output. With and oxi- dation catalyst and a particulate filter installed more than 95% of the LHV value of the diesel oil in- jected can be recovered.

Attachment 1

International Maritime Organisation (IMO) – NOx rules

MO is an agency under UN. IMO was established to improve safety at sea. The increased concern about air pollution at sea resulted in introduction of emission limits.
IMO Rules are included in: ”International Convention on the Prevention of Pollution from Ships”, the first set of regulations of emissions from ships and other marine installations, known as

”MARPOL 73/78”. The purpose is to reduce pollution at sea.
The present convention is a combination of the convention from 1973 and a protocol from 1978, coming into force in 1983. MARPOL include 6 annexes. Annex 6, concerns air pollution.
MARPOL 73/78, Annex VI came into force in 2005. Regulation 13, concerning NOx emissions from diesel engines >130 kW constructed after 1th of January 2000, includes three “TIERS”, levels of con- trol. TIER II concerns emissions from diesel engines build after January 1st 2011.


TIER III rules applies to ECA areas (”Emission Control Areas”). At present (Feb. 2018) the following ECA areas exists:

  • ”North American Emission Control Area” and
  • ”U.S. Caribbean Sea Emission Control Area”;

Ships built after January 1st 2016 shall meet the requirements included in the “NOx Technical Code 2008”. Included in the code are required exhaust measurements of: CO, CO2, HC, NOx and O2.

The values shall be adjusted to: 25 °C and a humidity of 10.71 g/kg;

Max allowed NOx emissions are given in (g/kWh) as function of the engines RPM as seen on Fig. A1.1 and Fig. A1.2.

For each engine is required: ”an Engine International Air Pollution Prevention Certificate (EIAPP Cer- tifiate)”. The EIAPP certificate documents that the engine with a given NOX reduction technology fulfill the IMO requirements.

Attachment 2

Size of ADNOX Reactor for 2.5 MW – 4 Stroke Diesel Engine