PD-22
The Intelligent Engine - One Solution to NOx Reduction
Peter Sunn PEDERSEN *
ABSTRACT
The paper outlines the present situation as well as the likely future NOx emission regulation scenario for marine vessels with a view to indicating where contributions to compliance can be expected by the Intelligent Engine concept. The paper goes on to describe emission reduction methods used to ensure compliance with the IMO NOx Regulation for two-stroke marine diesel engines and methods available for ensuring compliance with stricter emission regulations, and it discusses the future role of the IE concept. The main methods used are combustion system modification for the IMO Regulation, the use of water emulsified fuel to comply with somewhat stricter rules and SCR exhaust gas after-treatment for very strict limitations. All of these methods have been proven in service.
Key Words: Emissions, NOx, Regulations, Intelligent Engine, Injection System, Computer Control
1. INTRODUCTION
The title of this paper indicates that the Intelligent Engine concept (IE concept) is one method (out of several) to ensure environmentally friendly marine engines. The superior flexibility of the IE concept [1] is certainly a valuable tool when optimising an engine for low emissions - but even so, it takes more to create miracles! The actual development status of the IE concept is described in another paper at this conference [2].
For obvious commercial reasons, the basic combustion process in the engine cylinder has to be optimised with a view to obtaining the lowest possible fuel oil consumption compatible with the current emission legislation. If uniform limits were to apply to all vessels worldwide, a conventional engine with a normal camshaft would be able to be optimised for those boundary conditions nearly as well as a computer controlled IE concept engine. However, it is not unlikely that what can be agreed upon, as a general set of limits (i.e. the IMO Regulation in its present and future forms), may not be considered satisfactory locally or regionally for certain areas.
In fact, a 'local' regulation was introduced in Sweden a couple of years ago, with stricter demands than the IMO Regulation to NOx emissions and fuel sulphur content. At present, such 'local' regulations can only (like the Swedish ones) apply monetary penalties to impose emission limitations on international traffic on the oceans. Vessels complying with the relevant IMO regulations have the right to operate freely and cannot be denied access to harbours because they do not comply with such a 'local' regulation. Harbour fees, however, can be differentiated in relation to for instance NOx emissions and fuel sulphur content as in Sweden.
Conditions making it feasible to reduce emissions substantially for a limited period of time would favour the application of an IE concept. The establishment of coastal areas (near large cities) with a demand for low NOx emissions, forcing non-complying vessels to take a detour with associated waste of time and fuel to do so, is one such scenario. Another scenario would be the establishment of ' Special low-NOx areas', widening IMO's present concept of 'Special Areas' where only low-sulphur fuels (max. 1.5% sulphur) are allowed to be used. The Swedish harbour fee system is different since vessels desiring to benefit from lower harbour fees will have to comply with the given NOx emission values and fuel sulphur content all the time, not only when in Swedish waters.
To illustrate the likely contribution of the IE concept to emission reduction, the paper will outline the methods used by MAN B&W Diesel for conventional marine diesel engines and indicate where the IE concept could give advantages over conventional engines. The discussion will be divided into three main topics. The first is concerned with the means to ensure compliance with the present IMO NOx Regulation, which are relatively simple combustion system modifications. Secondly, for future, stricter regulations by IMO and for applications where lower limits apply (such as stationary plants), the use of water emulsified fuel is an effective and well-proven solution, Thirdly, very strict regulations are complied with by the use of SCR exhaust gas after-treatment.
2. PRIMARY METHODS FOR NOx EMISSION REDUCTION
Primary methods are defined as 'engine internal measures', some of which involve direct combustion modifications in terms of modifications to the fuel injection system while others influence NOx formation during combustion in other ways. The IE concept is interesting for some of these applications.
* MAN B&W Diesel A/S, Research & Development,
Teglholmsgade 41, DK-2450 Copenhagen SV, DENMARK.
FAX: +45 33 85 10 30, E-mail: psp@manbw.dk
