Lead traps

AUTOMOTIVE LEAD TRAPS POTENTIAL UNDER CANADIAN CONDITIONS... 

The information presented in this paper is directed to those individuals concerned with the fuel consumption benefits associated with the use of leaded gasoline and the reduction of lead emissions to the atmosphere through the use of automotive lead traps. 

Increased use of leaded gasoline in Canada may generate pressures to control automotive exhaust lead emissions, although there is no established health-based lead-in-air standard to serve as the basis for such control. If reduction of automotive lead emissions into the atmosphere should be required, controls should be placed on the amount of lead emitted from the tailpipe, similar to the manner by which gaseous emissions are controlled. Such action is more energy efficient than reducing the amount of lead used in gasoline. One effective way to control tailpipe lead emissions is the use of automotive exhaust lead trap that replaces the standard muffler (2). 

This report describes the two-year road test program, supported by laboratory analysis, conducted by the Canadian Combustion Research Laboratory of Energy, Mines and Resources Canada to evaluate the effectiveness of automotive exhaust lead traps. The exhaust traps were designed and built by the Du Pont Company. 

Du Pont and other major lead antiknock manufacturers have been developing automotive exhaust lead traps since the middle 1960s (3). Other road tests have shown these traps to be effective under benign climate conditions, but none have considered the wide range found in Canada. 

The test fleet consisted of eight identically-equipped 1974 four-door Chevrolet Biscaynes operated by the Department of National Defence, Canada. These cars were equipped with 5.74 litre V-8 engines having air pumps to supply secondary air to the exhaust manifolds to reduce gaseous emissions. Four vehicles were equipped with new standard muffler and exhaust pipe systems and were used as control cars. The standard mufflers and exhaust pipes of the second group of four cars were replaced with lead trap systems. 

Figure 1. Lead trap system and standard exhaust system.

Figure 3. Cutaway view of lead trap showing location of alumina pellets upstream of cyclone separators. The alumina pellets promote agglomeration and the dual parallel cyclones separate and retain the exhaust particulate matter in collection chambers.

TABLE 2. Effectiveness of lead traps in urban and highway operation. 

For the lead trap cars, lead emissions were only one-third those of the standard cars over the urban cycle and one-twelfth those of the standard cars over the highway cycle. This test demonstrates that purging of previously collected exhaust particulate matter does not take place with properly designed traps when switching from sustained mild driving conditions to more severe conditions of continuous operation at highway speeds. 

Automotive exhaust lead traps can reolace standard mufflers and portions of the exhaust system and can reduce automotive lead emissions by 80%. 

Automotive exhaust lead traps are equally effective over the wide range of temperatures encountered during the extremes of winter and summer driving conditions in Canada. 

Purging of previously collected lead salts occurs with standard exhaust systems, but does not occur with well-designed lead traps, such as the type tested in this program. 

The use of lead traps will not affect fuel consumption, vehicle drivability and exhaust muffling. Automotive exhaust lead traps are relatively... 

If the use of leaded gasoline is increased in Canada to obtain improved refinery efficiency and lower automotive fuel consumption, automotive lead traps offer a viable means to control lead emissions into the environment, if such control is considered necessary. 

Casella et al., "Evaluation of Lead Trap Performance in Exhaust Engine Control", Accordo di Ricerca (FEEMAS),... 

Despite present predictions for the number of diesel-powered cars in Europe to increase markedly, discussions on the engineering approach to the control of automobiel emissions have centered on the gasoline motor. Cylinder wall temperature, air-fuel ratios, exhaust gas catalysts, and lead traps were presented and discussed as remedies. Blended fuel, for instance gasohol or synthetic fuels, were not considered because they are used on a local basis or during transient, difficult conditions. The contribution of lubricating oil in PAH emissions exists but was not considered an important issue, and was not discussed in the meeting. 

A demonstration of the effectiveness of the du Pont trap appears in Fig. 5.9, in which the emissions from cars fitted with a standard exhaust and with the lead trap are compared. High efficiency of particle trapping is achieved, especially for the larger particle sizes (Table 5.10). Work at the Warren Spring Laboratory, England, showed that the lead emitted with standard exhausts and lead traps was respectively 70.0 and 37.5% of the lead input to the engine over a prolonged road test [15]. 

The cost of the lead trap is relatively modest, and re-cycHng of the collected lead is an economic possibility. No country has yet made fitting of the lead trap compulsory. 

Fig. 5.9 Lead emissions from a car with a standard exhaust and a du Pont exhaust lead trap [14]. 

The design of a lead trap press is illustrated in Fig. 5. Contrary to lead pipe presses, they are in horizontal design. They are provided with... 

Time-tried lead trap presses work at 300 tons pressure capacity and a lead charge of 30 kg with the container diameter being 82 mm, the stroke 2 x 250 mm and the pump capacity being about 22 H.P. 

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