Emitec pushes SCR tech for clean air

Confronted with the imminent introduction of the BS4 emission standard in 13 cities in April 2010, almost all commercial vehicle manufacturers in India are developing new engine platforms that can be optimised for cleaner combustion using the benefit of high-pressure fuel injection systems such as common-rail in conjunction with higher turbocharger boost, and by recirculating exhaust gas into the charge air to lower the combustion temperatures and hence the formation of nitrogen oxides.

However, as from the example of MAN Nutzfahrzeuge, this approach needs an aftertreatment device to meet the particulate limits. The German truckmaker, which launched the first engines with exhaust gas recirculation in 1999 following the introduction of Euro 3, began to fit Emitec’s PM-Metalit continuously regenerating partial-flow filters to its Euro 4 vehicles since the end of 2004.

On the other hand, Volvo and Mercedes-Benz chose Selective Catalytic Reduction (SCR) in the aftertreatment, which allowed them to reduce the level of complexity on the engine required for particulate reduction. What they did was optimise the injection strategy for minimum fuel consumption — advancing injection timing and running the engine hotter, thus reducing particulate formation to within BS4 limits but raising the raw emissions of nitrogen oxides, which were then reduced to below the permissible emission limits by the SCR system.

Although there is still a lot of confusion in the Indian market concerning which technology to adopt to reduce NOx – EGR within the engine or SCR in the aftertreatment, – Emitec believes it has the right solution to support whichever emissions reduction path the truck OEMs should choose to take. Its metal foil catalyst substrate technology offers crucial efficiency, packaging, and durability advantages compared to traditional extruded ceramic substrates, which translate into lower lifecycle costs although they are more expensive to install.

The disadvantages of current SCR systems are their relatively large space requirement and their cost. The vehicle has to accommodate a complete ‘chemical plant’ consisting of oxidation catalyst, urea mixer, SCR catalyst, and ammonia trap.

In addition, they also need a urea (AdBlue) tank, a dosing unit, an injection unit, as well as sensors and a control unit. Using the advantages of the turbulent structures of its metal substrates, Emitec’s engineers were able to combine most functions inside a single casing.

Complete SCR system

At the recent IAA commercial vehicle show in Hanover, Emitec showed off its first complete SCR system for trucks consisting of a storage tank, a dosing system with a pump, an injector, a control unit, and sensors. The system operates independently from the engine management system and is able to calculate the exact amount of urea for any given operating condition and inject it into the exhaust gas. Its extremely compact design makes it easier to integrate in, or retrofit to, commercial vehicles than conventional systems.

Whereas earlier installations using discrete Emitec components often came with Bosch’s Denoxtronic AdBlue-metering and injection devices, Emitec is now able to offer a complete solution in-house, with control unit, dosing module, and sensors from Continental, one of its parent companies (the other is GKN).

Based on the engine operating parameters and raw engine-out emissions, Emitec is able to optimise the configurations of the oxidation and hydrolysis catalysis stages using its LS and PE turbulence-generating foil structures so that its SCR reactor achieves the same, or an even marginally higher, level of NOx-reduction efficiency (80-percent-plus) at only 60 percent of the volume of a fully extruded ceramic catalyst.

“This is the first time in Emitec history that we are offering a complete solution ourselves,” Emitec Emission Control Technologies MD Chris Dias told this correspondent recently. “OEMs earlier had to work with five different component manufacturers to build a solution, whereas we will now engineer, build, supply, and integrate a total solution.”

Traditionally used for decades in an industrial environment, SCR for vehicles is only a few years old even in Europe, Dias pointed out, and there are still very few suppliers able to provide a fully integrated system. More often than not, each individual supplier’s output becomes another’s input and the OEM has to put the entire system together itself. This is changing now, and even Indian OEMs are looking at buying the entire system from one supplier, which was why Ashok Leyland bought Albonair earlier this year.

According to Dias all the critical components of the system are designed by Emitec itself. “The entire design and application knowhow we have in-house. Only the tank, piping, and connectors will be bought in,” he says.

The company is gearing up to offer the solution in India as well. The system will be designed centrally at Emitec’s headquarters in Lohmar, Germany, where it will also be built. Manufacture in India might only become a viable proposition closer to 2015, when the whole country moves to a unified emission norm, presumably BS5. Dias estimates a development cycle of six months after initial inputs from the OEM, but is guarded about revealing possible customer interest: “Tata, Ashok Leyland, and Eicher are still formulating their strategies, evaluating the available options for cost and benefit.”

Apart from MAN, he points out that Emitec also supplies EGR catalysts and diesel oxidations catalysts to Cummins in the US, and is “into their SCR systems also”.