A wood gas vehicle needs the same three cleaning stages as a stationary gasifier, a compact cyclone, a cooler that brings the gas from about 300 °C below 40 °C, and a replaceable fabric or sawdust filter, but they must fit on a chassis and survive vibration. The carrier’s service intervals of 100-200 km for the cyclone pot and 200-500 km for the filter are 6-15 times shorter than the stationary schedule, so check the filter’s suction rather than trusting either number.
Part of Wood Gas Vehicles
Gas cleaning for mobile use is the compact cyclone, cooler and filter on a vehicle that remove dust, tar and water from producer gas before the engine.
The Same Train, Smaller
The cleaning logic is the one in Gas Cleaning & Filtering: cyclone for dust while the gas is hot and dry, a cooler to condense tar and water, a filter after cooling, and a drain at every low point. On a vehicle each stage has to be smaller, mounted where it can be reached, and fitted with flexible joints.
| Stage | Carrier’s vehicle version | Detail |
|---|---|---|
| Cyclone | 15-20 cm steel cylinder, tangential inlet, mounted vertically; empty the pot every 100-200 km | Compact Cyclone Separator |
| Cooler | Finned radiator or heater core in the airflow path, with a condensation trap; gas from about 300 °C to below 40 °C | Radiator Setup |
| Filter | Canister of cotton cloth or dry sawdust, replaceable, changed every 200-500 km | Fabric Filter Housing |
Service Intervals That Do Not Agree
The stationary parent cleans or replaces the fabric filter every 50 hours. At a mean 60 km/h, 50 hours is 3,000 km. The vehicle carrier changes the filter every 200-500 km, which is 3.3-8.3 hours of driving.
- 3,000 ÷ 500 = 6 and 3,000 ÷ 200 = 15, so the schedules differ by a factor of 6-15.
- A smaller filter, more load swings and colder running could justify shorter intervals on a vehicle, but I cannot source a figure for either.
Use the suction at the engine as the real signal: a steady rise in the vacuum needed to draw gas, or a falling power at a given speed, means the filter is loading. Carry spare cloth either way; the carrier’s history lists tar fires in the filter as a common breakdown.
What You Need
- Space behind a shield for three stages, with the pot, filter and drains reachable from outside the vehicle.
- Flexible joints between the isolated unit and the rigid chassis.
- Spare filter material and a catch can for condensate.
- A way to bypass the engine during start-up, so the first gas goes to the flare (Startup Sequence (20-30 Minutes)).
Common Mistakes
- Sizing the stages by the empty space on the chassis. They are sized by gas flow.
- Placing drains where they can’t be reached. Condensate then floods the line.
- A filter that cannot be opened cold and outdoors. It gets opened hot or in a shed.
Safety
Every service point on the gas line is a carbon monoxide source
Producer gas is about 18-22% carbon monoxide by volume. Empty the cyclone pot, change the filter and drain the cooler only outdoors, with the unit cold and the engine off, standing upwind. Never do it in a garage or shed, and never open a housing while gas is present or while the system is hot, since tar-loaded media can ignite. See Carbon Monoxide Risks.
What’s Next
- Learn next: Compact Cyclone Separator — the first stage
- Combine with: Tar Removal (Cyclone & Cooling) — the stationary design arithmetic