Mats Lavenius

The Development and Performance of the Compact SCR-Trap System: A 4-Way Diesel Emission Control System

The tightening of Heavy Duty Diesel (HDD) emissions legislation throughout the world is leading to the development of emission control devices to enable HDD engines to meet the new standards. NOx and Particulate Matter (PM) are the key pollutants which these emission control systems need to address. Diesel Particulate Filters (DPFs) are already in use in significant numbers to control PM emissions from HDD vehicles, and Selective Catalytic Reduction (SCR) is a very promising technology to control NOx emissions. This paper describes the development and performance of the Compact SCR-Trap system - a pollution control device comprising a DPF-based system (the Continuously Regenerating Trap system) upstream of an SCR system. The system has been designed to be as easy to package as possible, by minimising the total volume of the system and by incorporating the SCR catalysts on annular substrates placed around the outside of the DPF-based system. This novel design gives rise to an easy-to-package emission control device capable of providing very high conversions of all four major pollutants, NOx, PM, CO and HC. The design details are discussed, and the performance of the system over both steady state and transient cycles is presented. NOx conversions of up to 92% have been demonstrated, and the systems emissions of all four pollutants are well inside the Euro V, and probably also the US 2007 limits (subject to verification of PM).

Combined SCR and DPF Technology for Heavy Duty Diesel Retrofit

The retrofitting of diesel engines with oxidation catalyst and particulate filter technology for the reduction of particulate matter (PM), hydrocarbons (HC) and carbon monoxide (CO) emissions has become an established practice. The design and performance of such systems have been commercially proven to the point that the application of these technologies is a cost effective means for states to effectively meet pollution reduction goals. One of the reasons that these technologies are so widely applied is because they can be sized and fitted based on easily measurable vehicle parameters and published engine emission information. These devices generally work passively with basic temperature and back pressure monitoring devices being used to alert the operator to upset conditions. The application of an effective NOx reduction technology in similar retrofit installation, is more complicated. There are no passive NOx reduction technologies that can be retrofit onto HDD vehicles. Because of the long useful life of existing HDD vehicles, a retrofit SCR technology that could provide 80% NOx reduction will be very beneficial. Previously, a retrofit CRDPF plus SCR technology was demonstrated for NOx reductions of 80% [1]. However, this system was primarily designed for development and demonstration purposes and there is a need for a truly commercialized retrofit product. In order to be widely acceptable, a retrofit SCR technology needs to be flexible in its control and installation, allowing it to fit on to a large cross section of vehicles. It must also be durable and cost effective. This paper will discuss the development of a commercially available four-way (NOx, PM, CO and HC) emission reduction product for retrofit on HDD vehicles. The system combines the Johnson Matthey CRT ® filter with a urea SCR system and is known commercially as SCRT® system. This paper will discuss the development of such a system through integration of the injection system hardware, control algorithm and catalysts. The SCRT® system utilizes a urea injection system that is deployed on the vehicle as components giving the product more flexibility and lower cost. The urea injection components are: urea pump, air regulator, dosing unit and nozzle. The system utilizes a control system that allows the application engineer to customize it to the engine and catalyst size. It can also use either an engine map or NOx sensor for urea injection control. Transient and steady state test cell data demonstrating > 80% NOx reduction with this system are presented. In addition, chassis dyno emissions results and field data from Europe are reported, demonstrating successful on-road performance of the system.

Development and validation of a one-dimensional computational model of the continuously regenerating diesel particulate filter (CR-DPF) system

Diesel emissions legislation continues to tighten around the world, and Particulate Matter (PM) emissions are currently the focus of much attention. Diesel PM can be controlled using Diesel Particulate Filters (DPFs), which can effectively reduce the level of carbon (soot) emissions to ambient background levels. In the Heavy Duty Diesel (HDD) area, the Continuously Regenerating Trap (CRT®) [1] has been widely applied in the retrofit market. This system will henceforth be referred to as the Continuously Regenerating DPF (CR-DPF). There are currently over 100,000 of these systems in use in retrofit applications worldwide. This system comprises a specially formulated Diesel Oxidation Catalyst (DOC) upstream of a DPF; the NO 2 generated by the DOC is used to combust the carbon collected in the DPF at low temperatures. A model describing the performance of the CR-DPF has been developed. This model comprises two basic components: i) a 1-D DOC model based on laboratory microreactor data, and ii) a 1-D DPF model. The DOC model includes Langmuir-Hinshelwood expressions to describe the kinetics of the NO, CO and HC oxidation reactions. This model has been validated using engine data measured over both low and high temperature driving cycles. The DPF model has been validated using engine bench pressure drop data measured over the ESC (European Stationary Cycle). These 2 models have been combined to create a full model of the CR-DPF system, which has been validated over a wide range of conditions. Very good agreement between the experimental data and the model has been achieved.