Imbert Gasifier – The constricted hearth, downdraft gasifier in the figure below ( more detail can be found in the FEMA plans) is sometimes called the Imbert. This website is dedicated to the construction of wood gasifiers that can be used to run a gasoline engine with. Woodgas has been around for a long time and it. It can be a stand-alone gasifier, heating water by cooling the gas, to be used to . is often the case in the upper throat of an Imbert or constricting throat gasifier.

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The downdraft gasifier startup and response time is intermediate between the fast crossdraft gasifier and the slow updraft gasifier. This furnace will weigh around lb, with lb of that being refractory ceramic.

Imbert Gasifier

Groeneveld 17 takes the time necessary for complete devolatilization to be equal to or larger than the Fourier time for heating up. This design with all the interrelated heat-feedback features is where I want hasifier begin testing, but many design variations, degree of refinement, much larger and smaller units, vehicle gasifiers, etc.

Fortunately, formulas for determining critical dimensions are given in a number of the older references Gengas ; Schliipfer Design ash-collecting areas to be easily cleaned. This puts the hearth load for the Imbert type gasifier on a comparable basis to the stratified downdraft gasifier. It is relatively inexpensive, uses simple materials of construction, is easy to fabricate, and can be operated by motorists imbbert a minimum of training.

In the annular combustor ring, when in combustion mode, the hot gas is mixed with secondary air, where it burns cleanly due to hot temperature and even mixing of gas and air.

These “simplifications” are “lost” when returning to a full Imbert hearth. Ash contents depend on the char content of the wood and the degree of agitation.

Imbert hourglass hearth variations

Whenever there is bridging gaaifier the fuel, air supports combustion beneath the bridge, creating hot flames and a spent gas with excess oxygen and little if any energy value. Most of the fuel mass is converted to gas within this combustion zone. For instance, maximum power was obtained from mm hearths that had five mm nozzles. Testing of this prototype will indicate whether a lighter, imbbert stainless steel hopper will withstand the internal temperatures.


Although I’m still new to working with gasifiers I do have a few feathers under my hat that gave me some basic but solid knowledge on this topic since I’ve acquired some real world “hands on” experience with the construction and the operation of both the Imbert and the FEMA gasifiers plus I’ve read as much as I could on the topic even if some of the technical language was a bit fuzzy to me including watching every video out there I could find.

The hearth constriction causes all gases to pass through the reaction zone, thus giving maximum mixing and minimum heat loss. No concerns of the fire climbing up through the wood hopper due to the wood hopper being a sealed oxygen free fuel holding vessel. Use of cleaning systems after the gasifier involves difficult waste disposal problems.

During World War II, stringent specifications were maintained on fuel production, which was carried out at a number of licensed factories.

Notice that the maximum efficiency for rice hulls occurs at twice the flow rate that produces the maximum heating value from rice hulls. Being an open top air fed design, the fire from the reaction zone can climb straight up through the fuel and waste it and it can cause the gasifier to run very hot and inefficent.

Additionally ash can start piling up from the reduction zone if the velocity is too low to blow out the ash. A distinction is made between “no throat” “single throat” and “double throat” Imbert type designs see Figure imbfrt. Table shows successful nozzle sizes for wood-fueled Imbert gas producers and the wider variation for nozzles used in successful Gaeifier and SGB gasifiers.

Consequently further production of volatiles will occur in the reduction zone, leading to tar evolution and tar entrainment in the product gas.

Design of downdraught gasifiers

These are called “suction gasifiers”. If gxsifier much char forms during high-load conditions, then the char level rises above the nozzles so that incoming air burns the char to reduce the char level. The gasifier is in many ways self-adjusting. More information is provided in later discussions. The processes in these four zones are examined below and the design basis will be discussed in the following section. The combustor preheats the primary gasification air, which creates a higher quality gas while lowering the temperature of combustion, which reduces deterioration of materials and lowers levels of NOx pollutants.


More pix and updated drawings to come! The diameter of the pyrolysis zone at the air nozzles is typically about twice that at the throat, and Table shows the hearth load on this basis also. Knowledge of maximum hearth lead permits one to calculate the size of hearth needed for various engine or burner sizes. The fuel is not quite as robust because the tar is a wasted “potential” fuel.

The fuel gas can be generated cooler and wetter and sootier for direct combustion it all burns clean at the right temperature and residence time, with the right amount of air mixed evenly.

Venselaar proposes a time-lag between complete heating up and complete devolatilization. If tarry gas is produced from this type of gasifier, common practice is to reduce the hearth constriction area until a low-tar gas is produced.

About one-third of the way up from the bottom, there is a set of radially directed air nozzles that permit air to be drawn into the chips as they move down to be gasified. The stratified-bed gasifiers currently under development at SERI and other facilities and discussed in Section 5. A list of known manufacturers is here. About one-third of the way up from the bottom of the gasifier unit, there is a set of radially directed air nozzles; these inject air into the wood as it gaasifier downward to be gasified.

It is gasifjer that, when operating in this condensing mode, the producer gas can be directed straight to an internal combustion engine without the need for further filtering. If ggasifier cross-sectional area of tasifier nozzles is too small, there will be an lmbert pressure drop in forming the air jets; if the cross-sectional area is too large, the air jets will have too low a velocity and the air will not penetrate the bed. There appears to be no theoretical limit to how much water can be turned into fuel gas, as long as temperature and time are sufficient for the reaction.