Plasma Technology

PLASMA TECHNOLOGY BY ASHISH BABBAR UMANG JAIN SUMIT GUPTA

PLASMA THE 4 TH STATE OF MATTER Plasma is by far the most common form of matter. Plasma in the stars and in the tenuous space between them makes up over 99% of the visible universe and perhaps most of that which is not visible. On earth we live upon an island of "ordinary" matter. The different states of matter generally found on earth are solid, liquid, and gas.

Plasma consists of a collection of free-moving electrons and ions - atoms that have lost electrons. Energy is needed to strip electrons from atoms to make plasma. The energy can be of various origins: thermal, electrical, or light (ultraviolet light or intense visible light from a laser). With insufficient sustaining power, plasmas recombine into neutral gas

Plasma temperatures and densities range from relatively cool and tenuous (like aurora) to very hot and dense (like the central core of a star). Ordinary solids, liquids, and gases are both electrically neutral and too cool or dense to be in a plasma state.

BENEFITS OF PLASMA TECHNOLOGY High efficiency lighting Manufacturing of semiconductors for home computers Flat-panel displays surface cleaning spraying of materials chemical analysis Plasma spraying of surface coatings for temperature and wear resistance, treatment of engine exhaust compounds, and ion thrusters for space flight.

PLASMA LIGHTING The most prevalent man-made plasmas on our planet are the plasmas in lamps. There are primarily two types of plasma-based light sources, fluorescent lamps and high-intensity arc lamps. Fluorescent lamps find widespread use in homes, industry and commercial settings.

High intensity arc lamps High-intensity sources are widely used in industrial and commercial settings as well as for outdoor and security lighting near homes and public areas. It is high-intensity arc lamps that give you the spectacular panoramic views of cities as you fly over them at night.

PLASMA ARC LAMPS In high-intensity arc lamps the light we see is generally produced directly by the plasma. Color characteristics are controlled by the chemical elements put into the plasma rather than by a phosphor coating on the wall.

FLUORESCENT LAMPS Inside every fluorescent lamp there lurks a plasma. It is the plasma that converts electrical power to a form that causes the lamp's phosphor coating to produce the light we see. The phosphor is the white coating on the lamp wall. A fluorescent lamp is shown here with part of the phosphor coating removed to reveal the blue plasma glow inside.

PLASMA DISPLAY TECHNOLOGY The plasma generates ultraviolet light which in turn excites the phosphor coating inside the glass envelope. The phosphor emits a single color of visible light. Each pixel consists of three sub-pixels, one each of red, green and blue. By combining these primary colors at varying intensities, all colors can be formed

Plasma displays generally consist of two glass plates, each containing parallel electrodes, sealed to form an envelope filled with a neon and xenon gas mixture. A gas discharge plasma is created by applying an electric field between the electrodes.

The xenon and neon gas in a plasma television is contained in hundreds of thousands of tiny cells positioned between two plates of glass. Long electrodes are also sandwiched between the glass plates, on both sides of the cells. The address electrodes sit behind the cells, along the rear glass plate. The transparent display electrodes , which are surrounded by an insulating dielectric material and covered by a magnesium oxide protective layer , are mounted above the cell, along the front glass plate. Both sets of electrodes extend across the entire screen. The display electrodes are arranged in horizontal rows along the screen and the address electrodes are arranged in vertical columns.

Ionization of the xenon or neon gas To ionize the gas in a particular cell, the plasma display's charges the electrodes that intersect at that cell. It does this thousands of times in a small fraction of a second, charging each cell in turn. When the intersecting electrodes are charged (with a voltage difference between them), an electric current flows through the gas in the cell. the current creates a rapid flow of charged particles, which stimulates the gas atoms to release ultraviolet photons.

The released ultraviolet photons interact with phosphor material coated on the inside wall of the cell. Phosphors are substances that give off light when they are exposed to other light. When an ultraviolet photon hits a phosphor atom in the cell, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. When the electron falls back to its normal level, it releases energy in the form of a visible light photon .

Formation of image in plasma display The phosphors in a plasma display give off colored light when they are excited. Every pixel is made up of three separate subpixel cells, each with different colored phosphors. One subpixel has a red light phosphor, one subpixel has a green light phosphor and one subpixel has a blue light phosphor. These colors blend together to create the overall color of the pixel

By varying the pulses of current flowing through the different cells, the control system can increase or decrease the intensity of each subpixel color to create hundreds of different combinations of red, green and blue. In this way, the control system can produce colors across the entire spectrum.

Advantages of plasma dispaly The main advantage of plasma display technology is that you can produce a very wide screen using extremely thin materials. And because each pixel is lit individually, the image is very bright and looks good from almost every angle. The image quality isn't quite up to the standards of the best cathode ray tube sets, but it certainly meets most people's expectations.

PLASMA CONVERTER a plasma waste converter is a plasma torch applied to garbage. A plasma torch uses a gas and powerful electrodes to create plasma , sometimes called the fourth state of matter. The temperatures generated by a plasma torch can be hotter than the surface of the sun (more than 6,000 degrees Celsius).

Unlike incinerators, which use combustion to break down garbage, there is no burning, or oxidation , in this process. The heat from plasma converters causes pyrolysis , a process in which organic matter breaks down and decomposes. Plasma torches can operate in airtight vessels. Combustion requires oxidization; pyrolysis does not. Plasma waste converters can treat almost any kind of waste, including some traditionally difficult waste materials. It can treat medical waste or chemically-contaminated waste and leave nothing but gases and slag. Because it breaks down these dangerous wastes into their basic elements, they can be disposed of safely. The only waste that a plasma converter can’t break down is heavy radioactive material, such as the rods used in a nuclear reactor . If you put such material in a plasma furnace, it would probably catch on fire or even explode.

PLASMA CONVERTOR PARTS Conveyor system Pre-treatment mechanism Furnace Plasma torch

In order to feed garbage into the converter, almost all plasma facilities have a conveyor system. Garbage is loaded on the conveyor and is pushed into the furnace (or pre-treatment system if the plasma facility uses one) by a plunger.

Pre-treatment mechanism Although a plasma torch can break down waste without any special pre-treatment, most plasma facilities employ some sort of pre-treatment process to make the entire system more efficient. Some designs use grinders or crushers to reduce the size of the individual pieces of garbage before moving in to the furnace. The plasma torch can break down the smaller pieces faster.

Here's where the magic happens. Furnaces have an airlock system to allow garbage to come in while preventing the hot gases in the furnace from escaping into the atmosphere. The furnace houses at least one plasma torch; many furnaces have multiple torches to break down all the matter. These torches are usually placed a little lower than halfway down the furnace. The furnace also features a drainage system to tap off the slag as it accumulates and a vent system to vent out the gases. In order to withstand the intense heat, furnaces are lined with refractory material and often have a water-cooling system as well.

PLASMA TORCH The plasma torches used in these facilities are custom-built. The amount of energy they consume, the lifespan of the electrodes it uses, the gas used for ionization (most torches just use ordinary air), the downtime it takes to replace an offline torch and the size of the plasma field it generates all depend on the specific manufacturer. Plasma torches are water-cooled.

Slag Drainage and Afterburners Molten slag pools at the bottom of the furnace and helps maintain the high temperature inside the gasification chamber. Occasionally slag must be drained from the furnace. Some furnaces have drains positioned at a certain height, others use a tap system. Either way, slag drains away from the furnace and cools in a separate chamber.

Gas ventilation The furnace also has a vent system to allow gasified components to pass into another part of the system

Afterburner Gases can pass through a secondary chamber where natural gas flames combust any remaining organic material in the gases. These extremely hot gases then pass through a Heat Recovery Steam Generator (HRSG) system, where they heat water to form steam. This steam then turns a steam turbine to create electricity .

SYNGAS CLEANING Alternatively, the gases from the furnace enter a chamber where they are cooled and scrubbed, usually by water. The gases pass through a spray of water, which scrubs the gases of pollutants and particulates. A filter system containing a base filter neutralizes acid gases. The acids in the gases and the bases in the filter combine to form inert salts. The cooled and clean gases continue through the system, which in most cases involves a gas turbine connected to an electricity generator .

If the plant uses an afterburner, the remaining gases must be cleaned thoroughly to get rid of any hazardous material. Many designs include a dry scrubber system. In this system, powdered carbon is injected into the gases to strip away mercury , a poisonous element. Gases also pass through a fabric or bag filter to remove any other dangerous particulates, like lead . Once the gases have been cleaned they move to the stack, where they are released into the atmosphere.

PLASMA CONVERTOR BY- PRODUCTS There are three main byproducts that are a result of the plasma gasification process: synthetic gas (syngas), slag and heat. Syngas is a mixture of several gases but mainly comprises hydrogen and carbon monoxide. It can be used as a fuel source, and some plants use it to both provide power for the plant and sell excess electricity to the power grid . Gas generated by a plasma converter depends on what you put into the furnace. If the garbage contains a lot of carbon-based material (in other words, organic waste), then you'll get more gas. Waste with a lot of inorganic material won''t yield as much gas. Because of this, some plasma facilities sort through garbage before feeding it into the system.

Molten slag draining from a plasma furnace

The solid byproduct from the gasification process is called slag . The weight and volume of the original waste material is dramatically reduced. The weight of the slag is about 20 percent of the weight of the original waste The volume of the slag is about 5 percent that of the original waste''s volume The slag can take different forms depending on how you cool it.

Metal nodules can be separated from the sand

Air-cooled slag forms rocks like this

BIBLIOGRAPHY WWW.HOWSTUFFWORKS.COM GOOGLE WWW.PLASMAS.ORG

Plasma Technology

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