By Eliot Lobo,
In the 12 years since Mr. Bernhard Kahlert founded PURItech, this German supplier of self-regenerating diesel particulate filters (DPFs) has carved out a niche for itself as a retrofit specialist with a variety of application-optimised exhaust aftertreatment systems for commercial vehicles and off-highway machines.
Its DPFs not only eliminate 99.9 per cent of ultrafine particles (<100 nanometres) “by count”, but also – unlike every other competing product – reduce the raw emissions of nitrogen dioxide (NO2), the highly toxic fraction of the pollutant oxides of nitrogen (NOx), by up to 80 per cent. Crucially, they work unaffected by diesel sulphur levels of up to 2,000 parts per million, making them the ideal “plug and play” retrofit anywhere in the world.
“The PURImax system, our most advanced DPF to date, delivers a very high NO2 reduction rate under all driving conditions – particularly at low load and in stop-and-go operation, but even at idle, when a diesel engine’s NO2 emissions are highest,” Kahlert tells this correspondent.
A PURImax system tested by TÜV over the European Transient Cycle cut NOx overall by 30 per cent and NO2 in particular by 75 per cent. “At lower exhaust gas temperatures typical of urban driving cycles, the NO2 reduction works even better than at high speed and load,” he says. “There, we’ve measured up to 97 per cent reduction.”
Indeed, at the low driving speeds characteristic of light- and medium duty trucks and city buses, the exhaust gas entering the aftertreatment device rarely exceeds 250°C. At these temperatures PURImax, which relies on the principle of “non-selective reduction” with HC and CO acting as reductants, actually outperforms SCR (selective catalytic reduction) systems of the Euro VI generation in both NO (nitric oxide) and NO2 reduction.
By contrast, he says, the SCR systems fitted on buses as original equipment have been measured to reduce NOx by only “10-20 per cent” in test cycles such as the Braunschweig City Driving Cycle or the Millbrook London Transport Bus cycle that simulate a real-world city bus duty cycle.
The problem is the platinum
PURItech’s secret is a patent-pending platinum-free washcoat formulation that is able to “highly reduce” NO2 even at 160°C, the temperature at which the platinum-loaded diesel oxidation catalysts (DOCs) within the SCR systems and continuously regenerating traps used as original equipment by most vehicle manufacturers “light off”, i.e., start oxidising NO into NO2. Till around 280°C, the minimum temperature for injection of the aqueous urea solution (AdBlue), SCR systems are actually increasing the engine-out NO2 manifold, Kahlert points out – by three times or more at the tailpipe.
Nitrogen dioxide makes up only 5 per cent of engine-out NOx, but exhibits serious respiratory health impacts and contributes directly to the formation of smog. Being heavier than air it tends to concentrate at ground level, where inhalation exposure is known to cause severe inflammation and impairment of the airway. Nitric oxide, on the other hand, is relatively harmless to human health in open spaces, and has no direct effect on the environment.
Strictly regulating NOx emissions has had no effect on reducing ambient concentrations of these pollutant species in much of urban Europe, Kahlert says, citing a 2012 report by the International Council on Clean Transportation. That’s because the real-world emissions from diesel engines, which power a growing majority of road vehicles on the Continent, are far higher in city traffic (where the effects of diesel exhaust are actually of highest concern) than in the “hot”, high-load test cycles stipulated by European legislation for the homologation of those engines.
Real-world emissions performance is something PURItech knows a thing – or three – about. As Daimler’s exclusive retrofit partner Europe-wide since February 2009, it has fitted approximately 8,000 Euro II and – III Mercedes-Benz trucks and buses with its DPFs, allowing them unlimited free access to all European low emission zones and (in Germany) classifying them in the Euro IV motorway toll category.
All PURItech DPFs are electronically monitored and the company keeps comprehensive records of the performance of each system from the workshop service logs. “When one of our filters comes in, we know how many kilometres it has run. We store all the data for the life of the filter and after each cleaning,” Kahlert says. Clogged filters are put through its unique PURIclean process, which guarantees 100 per cent ash-removal efficiency from a cleaning cycle of less than an hour, well within the duration of a standard maintenance event.
As part of the Daimler retrofit business PURItech also runs a filter exchange programme under which it retains ownership of the ceramic monolith and simply swaps it for a cleaned one in the workshop, making for an even swifter turnaround. As-new performance is guaranteed, he promises: “A filter cleaned with PURIclean exhibits equivalent backpressure to a new filter, and will perform as effectively over the same service interval.”
Crucially, Kahlert says, the system suffers no deterioration in performance even after long-term use – PURImax successfully passed the VERT endurance test (a Swiss evaluation method now administered by the Vienna-headquartered VERT Association), acknowledged by experts in the field to be the most rigorous in the business.
“After 2,000 hours of monitored operation on a coach that operates in Switzerland, our filter was re-tested on the engine dynamometer at the University of Biel. We achieved as good results as with the fresh system,” Kahlert says. “Only then were we granted the VERT label.”
Preparing to make the leap
Kahlert says there’s been a sharp increase in NO2 emissions across Europe over the past decade from vehicles that were retrofitted with (platinum-coated) DPFs because of earlier concerns about particulate emissions. However, the definitive 1 January 2015 deadline to bring annual average NO2 concentrations in the European-Commission-designated urban air quality monitoring zones across Europe down to the 40 µg/m3 limit set five years earlier will finally address a problem he believes has been overlooked for far too long.
More importantly for him personally, it’s already bringing PURItech the recognition he’s convinced it was long overdue. In recent months there’s been growing interest in the PURInator “NO2 slip converter” that, placed behind conventional DPF and SCR systems, will reduce the NO2 emission below the engine-out level, he reveals.
It will also open up opportunities to supply Euro-VI-spec SCR systems “with no NO2 increase” based on the same proprietary catalyst as its DPFs, even as he and his team work on enhancing the NOx-reduction efficiency of their “non-SCR” technology, positioning PURItech – as Kahlert hopes – for a play in the big league as an OE supplier.
Here, he believes, his company holds a significant advantage. “We are strong in Europe in retrofit and optional first fit supply because of our rich long-term application experience. Our knowledge is broader than any of the existing Tier-1s, which were never required to deal with circumstances a typical retrofit supplier has to.”
There’s one problem, though – with production of only 5,000 DPF systems per year, “65 per cent of those for on-highway trucks and buses”, the company is simply too small to be a competitive first-fit supplier. That threshold, he says, is a minimum annual capacity of 50,000 units. “So far we’ve not been in a position to deliver these quantities, or the requested pricing.”
But that’s going to change, over this year and the next. The company is gearing up to make the leap to global scale with a new joint venture in India, another one in the works in China, and an incipient “cooperation” with Volvo Trucks. The 2013 target is to become a first-fit supplier to the off-road OEMs, many of whom already offer PURItech devices as an option. “The quantities here are much lower and the price pressure isn’t as high as it is in the on-road market,” Kahlert explains. On-highway will be the next step, in 2014.
In India, PURItech is investing close to €3 million initially in a 26:74 joint venture that will build a “highly automated plant fitting typical Tier 1 requirements” by mid-2014. Rochi Engineers, its partner in PURItech Rochi Emission Control Pvt. Ltd., is a Pune-based vendor for exhaust mufflers to earthmover multinationals Caterpillar, JCB, Hyundai Heavy, and Case, and the generator-set OEM partners of Cummins.
Annual production at the new facility, which will be PURItech’s first outside its home base of Waldshut-Tiengen in the southern Black Forest, will start at 100,000 units – DPFs, SCR system components, DOCs, and PURIclean devices – and be scaled to 400,000 systems per year in subsequent years with a joint investment of €14 million.
For Rochi Engineers, the joint venture represents an entry into both, the business of emissionised exhaust products and, indeed, the automotive market. PURItech, for its part, gets to scale up at a cost that’s at least 30 per cent lower than it would be able to in Europe, Kahlert reckons. Then there’s the fact that the company’s systems don’t contain platinum, the most expensive part of any aftertreatment system, which means they “will be cheaper in mass production using the same filter monolith and canning technology”.
Moreover, the joint venture is intended to be completely self-sufficient, building on PURItech’s technology basis to develop components by itself. The effect of all three factors is that PURItech will, at long last, have compelling – and comprehensive – OE value propositions for prospective on-highway customers, not just in its existing European markets but also new ones in “North America, Russia, and the Near and Far East”, that will all be supplied components and systems from India.
The Indian market will take a while yet to develop because most truck OEMs have already plumped for (standard) SCR at Euro IV, “making the same mistake they made in Europe”, Kahlert shrugs. But he is nevertheless optimistic of PURItech’s chances in the aftermarket: “We’ve been informed that 1,000 city buses in New Delhi are going to be retrofitted with SCR systems. We see market potential if additional retrofit projects are initiated.”