Nett Technologies have developed a retrofit, three-way catalyst system for LPG-powered forklift trucks, available from Norman G Clark . The emission control kit includes a three-way catalytic muffler, an oxygen sensor, and a digital air to fuel ratio controller. The system removes carbon monoxide, nitrogen oxides, and hydrocarbons from LPG exhaust gases. The three-way catalyst systems are intended for forklifts operating in confined areas, where it can improve the air quality and help to meet the occupational safety and health standards.
Three-way catalyst in conjunction with an air to fuel ratio controller is an effective method of cleaning spark-ignition engine exhaust gases available. This technology has been used on automobiles since the introduction of electronic fuel injection. Now, with the availability of digital air to fuel ratio controllers designed for LPG fuel systems, the three-way catalyst technology, with its unsurpassed exhaust gas purification, can be applied on forklift trucks.
The Nett emission control kit includes a platinum-rhodium, three-way catalyst built into a muffler. The catalytic muffler is a direct-fit replacement of the original muffler to reduce the installation cost to minimum. To ensure high efficiency of the catalyst, a digital air to fuel ratio controller, supplied as part of the kit, is installed on the truck. The controller receives a feedback signal from a zirconia oxygen sensor (‘lambda’ sensor) placed at the inlet to the muffler.
Stoichiometric air to fuel ratio is realised by a solenoid valve which biases pressure on the fuel converter membrane using vacuum and, thus, controls the amount of fuel supplied to the mixer. In addition to the emission benefits, the application of the system improves the overall fuel economy of the truck.
Propane exhaust gases contain substantial quantities of carbon monoxide (CO) which is a problem in all confined space applications. CO is toxic and poses a health hazard to the workers. Another important pollutant found in LPG exhaust gases is nitrogen oxides (NOx). NOx levels produced by LPG engines are usually higher than those in gasoline exhaust gases. NOx is toxic and detrimental to some industrial products.
Nett three-way catalytic mufflers are new and effective means of controlling these emissions. Oxidation catalyst systems, traditionally used on LPG forklifts, are not effective in controlling NOx. Lean-biased fuel controllers, sometimes used as a means of CO control, increase NOx emissions and their benefit is frequently questionable.