Large solar collectors on the roof track the sun, collect sunlight, and distribute it through large optical fibers to the bioreactor's growth chamber. The fibers function as distributed light sources to illuminate cyanobacteria (algae).
Each growth chamber consists of a series of illumination sheets containing the optical fibers and moist cloth-like membranes on which the algae grow. By stacking the membranes vertically and better distributing the light, more algae can be produced via photosynthesis in a smaller area.
Photobioreactors use sunlight to sequestor carbon from coal-fired power plans as they produce biomass. The Ohio University reactor will ultimately remove the carbon generated by the production of about 125 MW of electricity in a coal fired plan.
This system is expected to sequester carbon at a cost of $5-8 per ton surpassing the U.S. Department of Energy's goal of $10 per ton. It will also reduce the space required by a factor of 10 or more, when compared to raceway cultivators.
Light delivery and distribution is the principle obstacle to using commercial-scale photobioreactors for algae production. In horizontal cultivator systems, light penetrates the suspension only to 5 cm, leaving most of the algae in darkness. The top layer of algae requires only about 1/10th the intensity of full sunlight to maximize growth, so the remaining sunlight is wasted.
The biomass has a variety of potential uses: hydrogen production, feedstocks, agriculture, pharmaceuticals.
Tuesday, December 23, 2008
UNINTERRUPTIBLE POWER SUPPLIES
Uninterruptible power supplies, or simply "UPS", is sometimes referred to as a battery backup system, which maintains a continuous supply of electric power to a building, or certain electrical devices within a building by supplying power from the UPS system whenever power is not available from the grid or utility company.
Typically, uninterruptible power supplies are located between the source of the normal power supply - such as the electric utility company - and the electric load the UPS system is protecting. When electric power from the grid fails - whether through a lightning strike, failed transformer, or a black-out occurs, the UPS will instantly recognize the loss or interruption of power from the grid, and switch from the grid power to UPS power.
Uninterruptible power supply systems can be designed to protect small or large loads, including systems small enough to protect one or more computers, to critical life support systems that may be found in a home or hospital, to telecommunications equipment where an unexpected power disruption could threaten life or health or serious business disruption or computer data loss.
Small UPS systems can protect loads as small as just one computer to large UPS systems that will power and protect a company's entire data center or a building such as an office building or hospital. These systems can be as large as 3-20 megawatts and typically work in conjunction with a genset or a cogeneration plant.
Typically, uninterruptible power supplies are located between the source of the normal power supply - such as the electric utility company - and the electric load the UPS system is protecting. When electric power from the grid fails - whether through a lightning strike, failed transformer, or a black-out occurs, the UPS will instantly recognize the loss or interruption of power from the grid, and switch from the grid power to UPS power.
Uninterruptible power supply systems can be designed to protect small or large loads, including systems small enough to protect one or more computers, to critical life support systems that may be found in a home or hospital, to telecommunications equipment where an unexpected power disruption could threaten life or health or serious business disruption or computer data loss.
Small UPS systems can protect loads as small as just one computer to large UPS systems that will power and protect a company's entire data center or a building such as an office building or hospital. These systems can be as large as 3-20 megawatts and typically work in conjunction with a genset or a cogeneration plant.
FLUE GAS DESULFURIZATION
Flue gas desulfurization is a chemical process to remove sulfur oxides from the flue gas at coal-burning power plants. Many FGD methods have been developed to varying stages of applicability.
Their goal is to chemically combine the sulfur gases released in coal combustion by reacting them with a sorbent, such as limestone (calcium carbonate, CaCO3), lime (calcium oxide, CaO) or ammonia (NH3). Of the FGD systems in the United States, 90 percent use limestone or lime as the sorbent. As the flue gas comes in contact with the slurry of calcium salts, sulfur dioxide (SO2) reacts with the calcium to form hydrous calcium sulfate (CaSO42H20) or gypsum.
Certain material produced by some power plants in an oxidizing and calcium based process for air emission scrubbing is called FGD (or synthetic) gypsum. FGD gypsum is precipitated gypsum formed through the neutralization of sulfuric acid. While the material may vary in purity, which is defined as the percentage of CaSO4٠2H2O, it is generally over 94% when it is used in wallboard manufacturing. Because this material is very consistent when produced by power plants, wallboard manufacturers will often be located adjacent to the power plant to allow the FGD material to be delivered directly to the wallboard plants. This synergistic relationship not only is economically attractive, but it reduces the need to mine natural gypsum and therefore has a positive environmental impact.
FGD material can be wet or dry. Definitions related to FGD material can be found on this website by clicking on the tab “What are CCPs?” on the Home Page. The PDF file “Glossary of Terms” can be downloaded. As many different terms are used for FGD material, and operational differences between systems may create slightly different types of FGD, this Glossary of Terms is a reliable source of information.
Their goal is to chemically combine the sulfur gases released in coal combustion by reacting them with a sorbent, such as limestone (calcium carbonate, CaCO3), lime (calcium oxide, CaO) or ammonia (NH3). Of the FGD systems in the United States, 90 percent use limestone or lime as the sorbent. As the flue gas comes in contact with the slurry of calcium salts, sulfur dioxide (SO2) reacts with the calcium to form hydrous calcium sulfate (CaSO42H20) or gypsum.
Certain material produced by some power plants in an oxidizing and calcium based process for air emission scrubbing is called FGD (or synthetic) gypsum. FGD gypsum is precipitated gypsum formed through the neutralization of sulfuric acid. While the material may vary in purity, which is defined as the percentage of CaSO4٠2H2O, it is generally over 94% when it is used in wallboard manufacturing. Because this material is very consistent when produced by power plants, wallboard manufacturers will often be located adjacent to the power plant to allow the FGD material to be delivered directly to the wallboard plants. This synergistic relationship not only is economically attractive, but it reduces the need to mine natural gypsum and therefore has a positive environmental impact.
FGD material can be wet or dry. Definitions related to FGD material can be found on this website by clicking on the tab “What are CCPs?” on the Home Page. The PDF file “Glossary of Terms” can be downloaded. As many different terms are used for FGD material, and operational differences between systems may create slightly different types of FGD, this Glossary of Terms is a reliable source of information.
ESTERIFICATION
Esterification is the chemical process of combining an alcohol and an acid which results in the formation of an ester.
• Acid Esterification. Oil feedstocks containing more than 4% free fatty acids go through an acid esterification process to increase the yield of biodiesel. These feedstocks are filtered and preprocessed to remove water and contaminants, and then fed to the acid esterification process. The catalyst, sulfuric acid, is dissolved in methanol and then mixed with the pretreated oil. The mixture is heated and stirred, and the free fatty acids are converted to biodiesel. Once the reaction is complete, it is dewatered and then fed to the transesterification process.
• Transesterification. Oil feedstocks containing less than 4% free fatty acids are filtered and preprocessed to remove water and contaminants and then fed directly to the transesterification process along with any products of the acid esterification process. The catalyst, potassium hydroxide, is dissolved in methanol and then mixed with and the pretreated oil. If an acid esterification process is used, then extra base catalyst must be added to neutralize the acid added in that step. Once the reaction is complete, the major co-products, biodiesel and glycerin, are separated into two layers.
• Methanol recovery. The methanol is typically removed after the biodiesel and glycerin have been separated, to prevent the reaction from reversing itself. The methanol is cleaned and recycled back to the beginning of the process.
• Biodiesel refining. Once separated from the glycerin, the biodiesel goes through a clean-up or purification process to remove excess alcohol, residual catalyst and soaps. This consists of one or more washings with clean water. It is then dried and sent to storage. Sometimes the biodiesel goes through an additional distillation step to produce a colorless, odorless, zero-sulfur biodiesel.
• Glycerin refining. The glycerin by-product contains unreacted catalyst and soaps that are neutralized with an acid. Water and alcohol are removed to produce 50%-80% crude glycerin. The remaining contaminants include unreacted fats and oils. In large biodiesel plants, the glycerin can be further purified, to 99% or higher purity, for sale to the pharmaceutical and cosmetic industries.
• Acid Esterification. Oil feedstocks containing more than 4% free fatty acids go through an acid esterification process to increase the yield of biodiesel. These feedstocks are filtered and preprocessed to remove water and contaminants, and then fed to the acid esterification process. The catalyst, sulfuric acid, is dissolved in methanol and then mixed with the pretreated oil. The mixture is heated and stirred, and the free fatty acids are converted to biodiesel. Once the reaction is complete, it is dewatered and then fed to the transesterification process.
• Transesterification. Oil feedstocks containing less than 4% free fatty acids are filtered and preprocessed to remove water and contaminants and then fed directly to the transesterification process along with any products of the acid esterification process. The catalyst, potassium hydroxide, is dissolved in methanol and then mixed with and the pretreated oil. If an acid esterification process is used, then extra base catalyst must be added to neutralize the acid added in that step. Once the reaction is complete, the major co-products, biodiesel and glycerin, are separated into two layers.
• Methanol recovery. The methanol is typically removed after the biodiesel and glycerin have been separated, to prevent the reaction from reversing itself. The methanol is cleaned and recycled back to the beginning of the process.
• Biodiesel refining. Once separated from the glycerin, the biodiesel goes through a clean-up or purification process to remove excess alcohol, residual catalyst and soaps. This consists of one or more washings with clean water. It is then dried and sent to storage. Sometimes the biodiesel goes through an additional distillation step to produce a colorless, odorless, zero-sulfur biodiesel.
• Glycerin refining. The glycerin by-product contains unreacted catalyst and soaps that are neutralized with an acid. Water and alcohol are removed to produce 50%-80% crude glycerin. The remaining contaminants include unreacted fats and oils. In large biodiesel plants, the glycerin can be further purified, to 99% or higher purity, for sale to the pharmaceutical and cosmetic industries.
BIOMASS GASIFICATION
Biomass fuels such as firewood and agriculture-generated residues and wastes are generally organic. They contain carbon, hydrogen, and oxygen along with some moisture. Under controlled conditions, characterized by low oxygen supply and high temperatures, most biomass materials can be converted into a gaseous fuel known as producer gas, which consists of carbon monoxide, hydrogen, carbon dioxide, methane and nitrogen. This thermo-chemical conversion of solid biomass into gaseous fuel is called biomass gasification.
The producer gas so produced has low a calorific value (1000-1200 Kcal/Nm3), but can be burnt with a high efficiency and a good degree of control without emitting smoke. Each kilogram of air-dry biomass (10% moisture content) yields about 2.5 Nm3 of producer gas. In energy terms, the conversion efficiency of the gasification process is in the range of 60%-70%.
Conversion of solid biomass into combustible gas has all the advantages associated with using gaseous and liquid fuels such as clean combustion, compact burning equipment, high thermal efficiency and a good degree of control. In locations, where biomass is already available at reasonable low prices (e.g. rice mills) or in industries using fuel wood, gasifier systems offer definite economic advantages.
Biomass gasification technology is also environment-friendly, because of the firewood savings and reduction in CO2 emissions.Biomass gasification technology has the potential to replace diesel and other petroleum products in several applications, foreign exchange.
The producer gas so produced has low a calorific value (1000-1200 Kcal/Nm3), but can be burnt with a high efficiency and a good degree of control without emitting smoke. Each kilogram of air-dry biomass (10% moisture content) yields about 2.5 Nm3 of producer gas. In energy terms, the conversion efficiency of the gasification process is in the range of 60%-70%.
Conversion of solid biomass into combustible gas has all the advantages associated with using gaseous and liquid fuels such as clean combustion, compact burning equipment, high thermal efficiency and a good degree of control. In locations, where biomass is already available at reasonable low prices (e.g. rice mills) or in industries using fuel wood, gasifier systems offer definite economic advantages.
Biomass gasification technology is also environment-friendly, because of the firewood savings and reduction in CO2 emissions.Biomass gasification technology has the potential to replace diesel and other petroleum products in several applications, foreign exchange.
PLASMA GASIFICATION
Plasma Gasification is able to get the energy it needs from waste-streams such as municipal solid waste (MSW) and even hazardous and toxic wastes, without the need to bury these wastes in a landfill.
There are two methods used in plasma gasification - the first one is a "plasma arc" and second is called a "plasma torch."
A "plasma arc" plasma gasification plant operates on principles similar to an arc-welding machine, where an electrical arc is struck between two electrodes. The high-energy arc creates a high temperature, highly ionized gas. The plasma arc is enclosed in a chamber. Waste material is fed into the chamber and the intense heat of the plasma breaks down organic molecules (such as oil, solvents, and paint) into their elemental atoms. In a carefully controlled process, these atoms recombine into harmless gases such as carbon dioxide. Solids such as glass and metals are melted to form materials, similar to hardened lava, in which toxic metals are encapsulated. With plasma arc technology there is no burning or incineration and no formation of ash.
"Plasma arc" plasma gasification plant have a very high destruction efficiency. They are very robust; they can treat any waste with minimal or no pretreatment; and they produce a stable waste form. The arc melter uses carbon electrodes to strike an arc in a bath of molten slag. The consumable carbon electrodes are continuously inserted into the chamber, eliminating the need to shut down for electrode replacement or maintenance. The high temperatures produced by the arc convert the organic waste into light organics and primary elements.
Combustible gas is cleaned in the off-gas system and oxidized to CO2 and H2O in ceramic bed oxidizers. The potential for air pollution is low due to the use of electrical heating in the absence of free oxygen. The inorganic portion of the waste is retained in a stable, leach-resistant slag.
In "plasma torch" systems, an arc is struck between a copper electrode and either a bath of molten slag or another electrode of opposite polarity. As with "plasma arc" systems, plasma torch systems have very high destruction efficiency; they are very robust; and they can treat any waste or medium with minimal or no pre-treatment. The inorganic portion of the waste is retained in a stable, leach-resistant slag. The air pollution control system is larger than for the plasma arc system, due to the need to stabilize torch gas.
There are two methods used in plasma gasification - the first one is a "plasma arc" and second is called a "plasma torch."
A "plasma arc" plasma gasification plant operates on principles similar to an arc-welding machine, where an electrical arc is struck between two electrodes. The high-energy arc creates a high temperature, highly ionized gas. The plasma arc is enclosed in a chamber. Waste material is fed into the chamber and the intense heat of the plasma breaks down organic molecules (such as oil, solvents, and paint) into their elemental atoms. In a carefully controlled process, these atoms recombine into harmless gases such as carbon dioxide. Solids such as glass and metals are melted to form materials, similar to hardened lava, in which toxic metals are encapsulated. With plasma arc technology there is no burning or incineration and no formation of ash.
"Plasma arc" plasma gasification plant have a very high destruction efficiency. They are very robust; they can treat any waste with minimal or no pretreatment; and they produce a stable waste form. The arc melter uses carbon electrodes to strike an arc in a bath of molten slag. The consumable carbon electrodes are continuously inserted into the chamber, eliminating the need to shut down for electrode replacement or maintenance. The high temperatures produced by the arc convert the organic waste into light organics and primary elements.
Combustible gas is cleaned in the off-gas system and oxidized to CO2 and H2O in ceramic bed oxidizers. The potential for air pollution is low due to the use of electrical heating in the absence of free oxygen. The inorganic portion of the waste is retained in a stable, leach-resistant slag.
In "plasma torch" systems, an arc is struck between a copper electrode and either a bath of molten slag or another electrode of opposite polarity. As with "plasma arc" systems, plasma torch systems have very high destruction efficiency; they are very robust; and they can treat any waste or medium with minimal or no pre-treatment. The inorganic portion of the waste is retained in a stable, leach-resistant slag. The air pollution control system is larger than for the plasma arc system, due to the need to stabilize torch gas.
ADSORPTION CHILLER
Absorption chillers use heat instead of mechanical energy to provide cooling. A thermal compressor consists of an absorber, a generator, a pump, and a throttling device, and replaces the mechanical vapor compressor.
In the chiller, refrigerant vapor from the evaporator is absorbed by a solution mixture in the absorber. This solution is then pumped to the generator. There the refrigerant re-vaporizes using a waste steam heat source. The refrigerant-depleted solution then returns to the absorber via a throttling device. The two most common refrigerant/ absorbent mixtures used in absorption chillers are water/lithium bromide and ammonia/water.
Compared with mechanical chillers, absorption chillers have a low coefficient of performance (COP = chiller load/heat input). However, absorption chillers can substantially reduce operating costs because they are powered by low-grade waste heat. Vapor compression chillers, by contrast, must be motor- or engine-driven.
Low-pressure, steam-driven absorption chillers are available in capacities ranging from 100 to 1,500 tons. Absorption chillers come in two commercially available designs: single-effect and double-effect. Single-effect machines provide a thermal COP of 0.7 and require about 18 pounds of 15-pound-per-square-inch-gauge (psig) steam per ton-hour of cooling. Double-effect machines are about 40% more efficient, but require a higher grade of thermal input, using about 10 pounds of 100- to 150-psig steam per ton-hour.
A single-effect absorption machine means all condensing heat cools and condenses in the condenser. From there it is released to the cooling water. A double-effect machine adopts a higher heat efficiency of condensation and divides the generator into a high-temperature and a low-temperature generator.
In the chiller, refrigerant vapor from the evaporator is absorbed by a solution mixture in the absorber. This solution is then pumped to the generator. There the refrigerant re-vaporizes using a waste steam heat source. The refrigerant-depleted solution then returns to the absorber via a throttling device. The two most common refrigerant/ absorbent mixtures used in absorption chillers are water/lithium bromide and ammonia/water.
Compared with mechanical chillers, absorption chillers have a low coefficient of performance (COP = chiller load/heat input). However, absorption chillers can substantially reduce operating costs because they are powered by low-grade waste heat. Vapor compression chillers, by contrast, must be motor- or engine-driven.
Low-pressure, steam-driven absorption chillers are available in capacities ranging from 100 to 1,500 tons. Absorption chillers come in two commercially available designs: single-effect and double-effect. Single-effect machines provide a thermal COP of 0.7 and require about 18 pounds of 15-pound-per-square-inch-gauge (psig) steam per ton-hour of cooling. Double-effect machines are about 40% more efficient, but require a higher grade of thermal input, using about 10 pounds of 100- to 150-psig steam per ton-hour.
A single-effect absorption machine means all condensing heat cools and condenses in the condenser. From there it is released to the cooling water. A double-effect machine adopts a higher heat efficiency of condensation and divides the generator into a high-temperature and a low-temperature generator.
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