Type: Process Essays
Sample donated: Mable Fuller
Last updated: September 11, 2019
JanBaptista Van Helmont, a Belgian chemist and physician, 1609, discovered thatgas could be produced from heating wood or coal and from this idea, severalothers contributed in developing and refining the gasification process: ThomasShirley, 1669, performs various experiments with carbonated hydrogen.
RobertGardner, 1788, became the first to obtain a patent dealing with gasification.John Barber, 1791, received the first patent in which “producer gas”was used to drive an internal combustion engine. Biomass gasification was firstconceived in 1798, when Philippe Lebon led efforts to gasify wood. The historyshows that gasification has grown from a simple conversion process used formaking “town gas” for industrial lighting to an advanced,multi-product, carbon-based fuel technology of today and tomorrow. Gasificationwas first used commercially in the 1800s for industrial and residential heatingand lighting.
As the use and distribution infrastructures for electricity andnatural gas evolved, town gas use declined and gasification development paused.However, history has shown that the technology is revisited when access tonatural gas, oil and petroleum products are limited through scarcity or highprices. Today, gasification technology development is enjoying a renaissance asa means for producing electrical energy, synthetic natural gas, liquid fuels orchemical products from coal, biomass, or other carbon containing materialsunder increasingly stringent environmental constraints. The gasificationprocess takes place in a device called a gasifier or gas producer, which canrange in size, shape, and design, depending on application or design year. Thelack (or limit) of oxygen and slow burn rate causes the fuel in gasifier torelease flammable gases like methane, carbon monoxide, and hydrogen.Nonflammable gases such as carbon dioxide and nitrogen are also released. Thesyngas is then treated according to use.
In short, gasification is defined as aprocess of conversion of any solid or liquid carbon-based material (feedstock) intogaseous fuel through its partial oxidation with air, oxygen, water vapor ortheir mixture or as the thermo-chemical process limited to a partial combustionand pyrolysis. Gasificationis considered most suitable option of biomass energy conversion because of itssimplicity and economy viable to produce thermal energy or decentralizedelectricity. The downdraft gasifiers are typically small-scale up to 5MWcapacity which facilitates their feasibility in remote areas such as villagesand islands. Modeling of this type of gasifier is about the design, predictingoperation behavior such as emissions during normal conditions, startup,shutdown, change of fuel, change of loading, and to improve performance. Downdraftwood Gasifier requires wood chips, biomass briquettes or wood likeagro-residues (such as stems, stalks).
Biomass gasification process usuallyinvolves drying where moisture content is reduced up to 5% at 100-2000C,pyrolysis where thermal decomposition of biomass occurs in the absenceof oxygen or air and volatile matter is released as a consequence of thethermal break down of biomass. Here the mixture of gases carbon monoxide,hydrogen, carbon dioxide and hydrocarbon gases from the biomass is released andbiomass is reduced to solid charcoal. The hydrocarbon gases condense at a lowtemperature to generate liquid tars. Oxidation where solid carbonizedbiomass is combined with oxygen in the air to form CO2 which lead to excessiveamount of heat release that is utilized for drying, pyrolysis and gasificationreactions. The oxidation of carbon and hydrogen also took place. Reduction duringwhich several endothermic reactions occur at 800-1000C such as Water–gasreaction, boudouard reaction, shift reaction, methane reaction. CHAP2. RESEARCH PURPOSE AND SIGNIFICANCE Inthis research the modeling and optimization of a downdraft gasifier will beconducted through mathematical model and simulation to save time and cost whichsupport preparation and optimization of experiments undertaken in real systems.
The simulations have to show comprehensive physical and chemical mechanismsinside gasifier.to do so the combined transport and kinetic model will beresearched for efficiency improvement and optimization. Thisresearch will have great impact because it will help to deal with the climatechange which is a very problem that today’s world is facing. It will also myimpact my country energy because actually in my country we still have a problemof energy where 45% of the population doesn’t have electricity or any otherenergy from the grid. So the implementation of projects in this area will havea big influence on my country energy generation as well I will acquire skillsto be involved in consultancy projects.
Biomassgasifier is useful in different systems: driving of farm machinery liketractors, harvesters; small scale electricity generation systems; irrigationsystems; direct heat systems (grain drying, green house heating and running ofabsorption refrigeration and cooling systems, running of Stirling engines);worked with other renewable energy systems like solar for thermal applications;production of chemicals like Methanol and Formic acid; run a fuel cell plant.