Tuesday, May 12, 2009

Pyrolysis-Green technology

Pyrolysis is an emerging technology and its green credentials when the feed is biomass are top notch. Everyone who has lit a wood or coal fire and watched it burn has seen pyrolysis. Pyrolysis is usually the first chemical reaction that occurs in the burning of many solid organic fuels, like wood, cloth, and paper, and also of some kinds of plastic.In a wood fire, the visible flames are not due to combustion of the wood itself, but rather of the gases released by its pyrolysis; whereas the flame-less burning of embers is the combustion of the solid residue (charcoal) left behind by it. Although the basic concepts of the process have been validated, the performance data for an emerging technology have not been evaluated according to methods approved by EPA and adhering to EPA quality assurance/quality control standards.Waste is converted to a fuel by heating the waste which burns just as coal or wood does under the right controlled conditions. Whereas incineration fully converts the input waste into energy and ash, these processes limit the conversion so that combustion does not take place directly.

Waste Plastic under pressure and catalytic cracking produces fuel and can be used as a fuel source. Under certain temperature conditions the plastic macromolecular chains are broken down into small molecular chains (simple hydrocarbon compounds) and those small molecular compounds contain C4 to C20, this compound is a component of petrol, coal oil, and diesel.Anhydrous pyrolysis can also be used to produce liquid fuel similar to diesel from solid biomass.Fast pyrolysis occurs in a time of a few seconds or less. Therefore, not only chemical reaction kinetics but also heat and mass transfer processes, as well as phase transition phenomena, play important roles. Fast pyrolysis is a process in which organic materials are rapidly heated to 450 - 600 degrees C in absence of air. Under these conditions, organic vapors, permanent gases and charcoal are produced.

Friday, May 1, 2009

Optical Microscopes

Optical microscopes use visible light and a system of lenses to magnify small samples that are usually un-seen to the bare eye. The optical microscope is the first, oldest and simples type of microscope (as opposed to the much more advanced electronic microscope). The first optical microscopes were created in the 18th century. Due to it's compact sizes, simplicity and relatively low price, the optical microscope is very popular, and can be found in use in many areas of biology. Optical microscopes mostly magnify objects for up to 1500 times. The first optical microscopes were structured in a way that is called "the simple microscope". This structure utilizes only one pair of lenses to create a magnified image of the sample. Today, the simple structure is in use only in the magnifying glass, hand lens and the loupe.

The more advances optical microscopes, and the ones that are popular today, are what's called "compound optical microscopes". These microscopes use a system of many lenses, in order to "compound" and multiply the magnification, and therefore maximize it. The two main lens systems in an optical microscope are the objective lens (near the examined object), and the eyepiece lens (up near the eye of the scientist). Modern optical microscopes use multiple lenses both in the objective part as well as the eyepiece part. The old optical microscopes also used a mirror to provide illumination below the object. The modern optical microscopes use a strong lamp to provide constant and strong illumination.

The main uses of compound optical microscopes include:

The examining small pieces of material, or even a smear or a squash preparation. This is due to the fact that the optical microscope uses light to pass beneath the object and enter the lenses. That's why the item is better be half-transparent. In other uses the optical microscope may be used to examine metal samples, in order to study the metal's structure.
At low power, microscopes can be used to examine small living animals and plants. At high power, they can be used to examine bacteria. It is important to note that the vast advancement in medicinal fields and biology in general, is owed to a large extent, to the invention of the optical microscopes. For example, the way the blood flows in our body was not fully understood until the microscope made in possible to examine small blood vessels behavior.