The most basic definition of gasification is that it is any chemical or thermal process used to convert a substance into a gas.
Coal has been gasified since the industrial revolution to produce “town gas.” This was once done at local gas works, and every town had one. Heating coal under controlled conditions with insufficient air to provide complete combustion produces a gaseous fuel known as syngas, which is also known as town gas when cooled, cleaned, and compressed. As we all know, using gas as a fuel for so many jobs is much more controllable and much more preferable than using coal.
Gasification technology is at the forefront of efforts to develop alternatives to conventional furnaces. It is of particular interest because it offers the opportunity to use product fuel gas in integrated gasification combined cycle (IGCC) electricity generation. High hopes are placed on IGCC as a highly efficient, low-emissions technology.
Gasification can also be fueled by materials that would not otherwise be useful fuels, such as biomass or organic waste. In addition, it also solves many concerns about the reduction of air quality. This is because the high-temperature conversion reaction essential to the process also refines corrosive ash elements such as chloride and potassium, allowing clean gas production.
Furthermore, many have reported that by using their technology, the heating (calorific) value of the product gas can be stabilized regardless of changes in raw material type, ash content, or moisture content.
In some types of gasification plants, gasification takes place in the three by-products of the fume and uses them to fuel a second reaction by concentrating the heat on a bed of charcoal. These coals typically reach over 1800 degrees F in the gasifier, which is hot enough to break down water vapor to hydrogen and CO2 to carbon monoxide.
Gasification is extremely environmentally friendly as, if designed correctly, gasification systems produce minimal pollution even when processing dirty feedstocks, such as high sulfur coals. In addition, gasification can effect large volume reductions in solid waste while producing an inert, environmentally friendly, slag-like byproduct.
Jan Becker, CTO of a US energy company that is growing rapidly in its gasification skills, added that; “The gasifier is becoming an important factor in the race to ‘green America,’ as there is increasing awareness that many of the substances the United States throws away can be gasified and then turned into useful products like electricity, ethanol, methanol, and biodiesel”.
The gas produced by the gasifiers (mainly composed of 15-25% carbon monoxide, 10-20% hydrogen and 1-5% methane), is burned in special burners to achieve maximum efficiency. The best high quality gasifier systems can be fed with what would otherwise be only low quality waste oils or tar oils and sludges. Some slurry-fed O2 entrained gasifiers operate between 2400°F and 2700°F.
In these latest high-tech systems, high-pressure steam is produced for internal and local CHP (Combined Heat and Power) use, by cooling the syngas in a radiant syngas cooler and then using (in this case) two coolers. convective syngas from parallel fire tubes.
That’s top of the range in technological development. In the background. The most basic level of the gasifier is really simple. Gasifying wood stoves can be made from designs freely available as templates that can be made almost entirely from scrap parts found in various dumpsters.
Gasifiers that are intended for the processing of biomass and organic waste are also now available, and this has been found feasible at current oil prices, when one considers that the numerical calculations are based on low-quality coal. It has also been shown that the process can be both stable and controllable. New designs can be evaluated in advance by evaluating the numerically derived analysis produced by the RESORT software, to predict the physical and chemical processes in the gasifier. The Euler-Lagrange approach is used for the gas and particulate phase and the Navier-Stokes equations are analyzed using the finite volume method.
