In many locations, hope has however not been abandoned that this `impossibility' could be overcomed. So, at Outokumpu copper mill at Vuoksenniska, a large, stationary, gasifier was built, working with overpressure (figure 1), where the fuel container was connected to a spray condenser, which efficiently sucked out the steam and dried the fuel in that manner. Completely wet wood were used, but the condenser had to be supplied with an adjustable valve, so that some permanent gases could be released, otherwise its condensing capacity would become insufficient and the quality of the gas too low.
A few years ago, in the laboratory at the Institute of Technology in Helsinki, I also performed attempts to remove steam from a vehicle gasifier fuel container, using an ejector (figure 2). Exhaust gases from the motor were used as powering media. A significant improvement of gas quality could be observed during these tests. Unfortunately, some combustible gases were lost, which was avoided with the device suggested by dr. Lutz (figure 3).
The practical experiences with the new design were however baffling: the car not only operated satisfactory with regular air-dry fuel, but also with fresh wood the motor ran reliably and with acceptable power.
The difference between a regular container with cooling mantle, and a monorator is shown in figure 5. In a regular gasifier, the fuel container is tall and lean, surrounded by warm gas, and only equipped with an in comparison small cooling surface at the top. The bottom of the container is also heated to its full extent. In the monorator however, the fuel tank is low, made either circular, oval, or rectangular, with a bottom surface that is cooled to most of it extent, or at least has a cooled surface that is significantly larger than the cross section area of the gasifier itself. While the fuel container in the standard gasifier is heated both from the hearth as well as from the hot gases that are lead around the lower parts of the container, only parts of the fuel in the monorator receives heat, and only from the furnace, while the main portion of the fuel is protected from heating due to the shape of the fuel container and the special form of the cooled bottom, and is cooled by the proportionally large cooling surfaces in contact with the surrounding air.
Through a calibrated Poncelet-nozzle 1, air is sucked into a vessel 2, from which it goes on to the gasifier 3. With the mercury barometer 4 the vacuum of the vessel 2 is measured, so that one can, at any time, determine the amount of air sucked in per time unit, and from that calculate the load of the gasifier. In the separation vessel 5, condense water is collected and removed. The gas is sucked out from the gasifier at 7 with an ejector 8 operating on compressed air, and blown out to the outside air, but apart from that and through a side pipe, using a pressured water operating ejector 9, a small amount of gas is led via a gas meter 10, and a small gasholder 11, to a Bunsen burner 12, where it combusts and deliver its heat to a Junker calorimeter 13.
In figure 7 a number of curves has been drawn, which show how the calorific value has varied when fuel of varying moisture has been used in monorator versus a standard gasifier. For the variations in load, only a single graph has been drawn, since the load was set practically identical for all tests. Furthermore, it should be noted that the gas can be considered fully satisfying if its calorific value reaches 1150 kcal/m≥.
top: oven dried wood (8.6 % moisture),
middle: air dry wood (19.5 % moisture),
below: damp wood (about 47 % moisture)
-- -- -- -- standard gasifier,
To examine the impact of the cooling of the monorator container, a number of tests were carried out with the gasifier indoors and without efficient cooling. In figure 8 we compare the results from such a test with the results from the one with a gasifier operating with a cooled fuel container. The difference is conspicuous: in spite of the fact that significantly more moist wood was used in the cooled monorator, the produced gas is much better. Not until the end of the test when the wood supply had gotten time to dry, the heat value rises for the uncooled gasifier also. During the tests it was also observed that the ejected gas became slightly foggy when cooling was slow, and that the separated amount of distillate was much smaller than usual.
To examine the cooling effect of the main fuel supply's contact surface a furrow was attached to the base of the cooling mantle and equipped with an extra separation vessel (figure 9). From this we could see that only a third of the distillate was collected from the furrow near the mantle, while two thirds were collected by the regular separator, which suggests that only 30 % is condensed directly by the outer cooling mantle, while the majority is condensed within the fuel itself. In the end it is of course the cooling mantle which lead away the heat, while the reserve fuel works as an accumulator of the cold.
To further confirm that that the results achieved with the monorator depended not upon the furnace but rather upon the design of the fuel container, a number of tests were carried out with a standard gasifier, equipped with a monorator container above the regular fuel container, and also with a cut off container and monorator on top of that. The results are shown in figure 10. Severely moist wood was used in all tests. From the results we can see that a standard gasifier operates better with damp fuel, if it is equipped with a monorator container, but that the heated container still impairs the result, albeit to lesser extent the more this heated container is shortened.
- standard gasifier without condenser
- standard gasifier with monorator container
- standard gasifier with shortened container and monorator
- pure monorator design
This document was translated from LATEX by HEVEA.