A high pressure watertube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace. In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam. High Pressure Water Tube Boiler: The heated water rises into the steam drum. Here, saturated steam is drawn off the top of the drum. In some services, the steam will reenter the furnace through a superheater to become superheated. Superheated steam is defined as steam, heated above the boiling point at a given pressure. Superheated steam is a dry gas and therefore used to drive turbines, since water droplets can damage turbine blades. Cool water at the bottom of the steam drum returns to the feedwater drum via large-bore'downcomer tubes', where it pre-heats the feedwater supply.. To increase economy of the boiler, exhaust gases are used to pre-heat the air blown into the furnace and warm the feedwater supply.
Such watertube boilers in thermal power stations are called steam generating units. The older fire-tube boiler design, in which the water surrounds the heat source and gases from combustion pass through tubes within the water space, is a much weaker structure and is used for pressures above 2.4 MPa. A significant advantage of the watertube boiler is that there is less chance of a catastrophic failure: there is not a large volume of water in the boiler nor are there large mechanical elements subject to failure. A water tube boiler was patented by Blakey of England in 1766 and was made by Dallery of France in 1780. “The ability of watertube boilers to generate superheated steam makes these boilers attractive in applications that require dry, high-pressure, high-energy steam, including steam turbine power generation”. Owing to their superb working properties, the use of watertube boilers is preferred in the following major areas: Variety of process applications in industries Chemical processing divisions Pulp and Paper manufacturing plants Refining unitsBesides, they are employed in power generation plants where large quantities of steam having high pressures i.e. 16 megapascals and high temperatures reaching up to 550 °C are required.
For example, the Ivanpah solar-power station uses two Rentech Type-D watertube boilers. Modern boilers for power generation are entirely water-tube designs, owing to their ability to operate at higher pressures. Where process steam is required for heating or as a chemical component there is still a small niche for fire-tube boilers, their ability to work at higher pressures has led to marine boilers being entirely water-tube. This change began around 1900, traced the adoption of turbines for propulsion rather than reciprocating engines – although watertube boilers were used with reciprocating engines. There has been no significant adoption of water-tube boilers for railway locomotives. A handful of experimental designs were produced, but none of these were successful or led to their widespread use. Most water-tube railway locomotives in Europe, used the Schmidt system. Most were compounds, a few uniflows; the Norfolk and Western Railway's Jawn Henry was an exception, as it used a steam turbine combined with an electric transmission.
LMS 6399 FuryRebuilt after a fatal accidentLNER 10000 "Hush hush"Using a Yarrow boiler, rather than Schmidt. Never successful and re-boilered with a conventional boiler. A more successful adoption was the use of hybrid water-tube / fire-tube systems; as the hottest part of a locomotive boiler is the firebox, it was an effective design to use a water-tube design here and a conventional fire-tube boiler as an economiser in the usual position. One famous example of this was the USA Baldwin 4-10-2 No. 60000, built in 1926. Operating as a compound at a boiler pressure of 2,400 kilopascals it covered over 160,000 kilometres successfully. After a year though, it became clear that any economies were overwhelmed by the extra costs and it was retired to become a stationary plant. A series of twelve experimental locomotives were constructed at the Baltimore and Ohio Railroad's Mt. Clare shops under the supervision of George H. Emerson, but none of them was replicated in any numbers; the only railway use of water-tube boilers in any numbers was the Brotan boiler, invented in Austria in 1902 by Johann Brotan and found in rare examples throughout Europe.
Hungary, was a keen user and had around 1,000 of them. Like the Baldwin, this combined a water-tube firebox with a fire-tube barrel; the original characteristic of the Brotan was a long steam drum running above the main barrel, making it resemble a Flaman boiler in appearance. While the traction engine was built using its locomotive boiler as its frame, other types of steam road vehicles such as lorries and cars have used a wide range of different boiler types. Road transport pioneers Goldsworthy Gurney and Walter Hancock both used water-tube boilers in their steam carriages around 1830. Most undertype wagons used water-tube boilers. Many manufacturers used variants of the vertical cross-tube boiler, including Atkinson, Clayton and Sentinel. Other types include the Clarkson'thimble tube' and the Foden O-type wagon's pistol-shaped boiler. Steam fire-engine makers such as Merryweather used water-tube boilers for their rapid
Bioclogging or biological clogging is clogging of pore space in soil by microbial biomass. The microbial biomass blocks the pathway of water in the pore space, forming a certain thickness of impermeable layer in soil, it reduces the rate of infiltration of water remarkably. Bioclogging is observed under continuous ponded infiltration at various field conditions such as artificial recharge ponds, percolation trench, irrigation channel, sewage treatment system and landfill liner, it affects groundwater flow in aquifer, such as permeable reactive barrier and microbial enhanced oil recovery. In the situation where infiltration of water at appropriate rate is needed, bioclogging can be problematic and countermeasures such as regular drying of the system are taken. In some cases bioclogging can be utilized to make impermeable layer to minimize the rate of infiltration. Bioclogging is observed as the decrease of the infiltration rate. Decrease in the infiltration rate under ponded infiltration was observed in 1940s for studying the infiltration of artificial recharge pond and the water-spreading on agricultural soils.
When soils are continuously submerged, permeability or saturated hydraulic conductivity changes in 3 stages, explained as follows. Permeability decreases for 10 to 20 days due to physical changes of the structure of the soil. Permeability increases due to dissolving the entrapped air in soil into the percolating water. Permeability decreases for 2 to 4 weeks due to disintegration of aggregates and biological clogging of soil pores with microbial cells and their synthesized products, slimes or polysaccharides; the 3 stages are not distinct in every field condition of bioclogging. The change in permeability with time is observed in various field situations. Depending on the field condition, there are various causes for the change in the hydraulic conductivity, summarized as follows. Physical causes: Physical clogging by suspended solids or physical changes of soils such as disintegration of aggregate structure. Dissolving of the entrapped air in soil into the percolating water is physical cause for the increase of the hydraulic conductivity.
Chemical causes: Change in the electrolyte concentration or the sodium adsorption ratio in the aqueous phase, which causes dispersion and swelling of clay particles. Biological causes: Usually bioclogging means the first of the following, while bioclogging in broader sense means all of the following. Bioclogging by microbial cell bodies and their synthesized byproducts such as extracellular polymeric substance, which form biofilm or microcolony aggregation on soil particles are direct biological causes of the decrease in hydraulic conductivity. Entrapment of gas bubbles such as methane produced by methane producing microorganisms clog the soil pore and contributes in decreasing hydraulic conductivity; as gas is microbial byproducts, it can be considered to be bioclogging. Iron bacteria stimulates; this is an indirect biological cause of decrease in hydraulic conductivity. Bioclogging is observed under continuous ponded infiltration in such places as artificial recharge ponds and percolation trench.
Reduction of infiltration rate due to bioclogging at the infiltrating surface reduces the efficiency of such systems. To minimize the bioclogging effects, pretreatment of the water to reduce suspended solids and organic carbon might be necessary. Regular drying of the system and physical removal of the clogging layer can be effective countermeasures. Operated cautiously in this way, bioclogging is still to occur because of microbiological growth at the infiltrating surface. Septic drain fields are susceptible to bioclogging because nutrient rich wastewater flows continuously; the bioclogging material in the septic tank is sometimes called biomat. Pretreatment of water by filtration or reducing the load of the system could delay the failure of the system by bioclogging. Slow sand filter system suffers from bioclogging. Besides the countermeasures mentioned above, cleaning or backwashing sand may be operated to remove biofilm and recover the permeability of sand. Bioclogging in rivers can impact aquifer recharge in dry regions where losing rivers are common.
Bioclogging can have a positive effect in certain cases. For example, in the dairy waste stabilization ponds used for the treatment of dairy farm wastewater, bioclogging seals up the bottom of the pond. Algae and bacteria may be inoculated to promote bioclogging in irrigation channel for seepage control. Bioclogging is beneficial in landfill liner such as compacted clay liners. Clay liners are applied in landfill to minimize the pollution by landfill leachate to the surrounding soil environment. Hydraulic conductivity of clay liners become lower than the original value because of bioclogging caused by microorganism in the leachate and pore spaces in clay. Bioclogging is now being studied to be applied for geotechnical engineering. Bioclogging can be observed. Over months and years of continued operation of water wells, they may show a gradual reduction in performance due to bioclogging or other clogging mechanisms. Biofilm formation is useful in bioremediation of biologically degradable groundwater pollution.
Permeable reactive barrier is formed to contain the groundwater flow by bioclogging and to degrade pollution by microbes. Contaminant flow should be analyzed because preferential fl
Demon Wind is a 1990 American horror film directed by Charles Philip Moore. The film concerns a group of friends who travel to an old farm, soon find they can't leave as a mysterious fog sets in. In 1931, a body is burned on a cross. On a farm, a woman named Regina attempts to barricade a door, from where beyond, demons try to enter, her husband George kills her. Sixty years after the suicide of his father, a young man named Cory, the grandson of Regina and George, his girlfriend Elaine, along with a group of their friends, travel up to the farm, so that Cory can figure out what happened to his grandparents, they are attacked by a band of vicious demons. When the kids try to escape, a mysterious fog brings them back to the farm, protected by a shield that prevents the demons from entering the house. One by one, the kids become possessed by the demons, but manage to fight them off with a pair of daggers they find, the only thing that will kill them, but when the demons' master arrives, the kids realize they will need something stronger to fend off the hellish threat.
Eric Larson as Cory Francine Lapensée as Elaine Rufus Nirris as Harcourt Jack Forcinito as Stacey Stephen Quadros as Chuck Mark David Fritsche as Jack Sherry Leigh as Bonnie Bobby Johnston as Dell Lynn Clark as Terri Richard Gabai - Willy Mia Ruiz as Reena Kym Santelle as Harriet Stella Kastner as Grandmother Regina Axel Toowey as George C. D. J. Koko as Grand Demon Lou Diamond Phillips has an uncredited cameo role as a demon. Demon Wind has received a negative critical reaction. On Rotten Tomatoes, the film has a "rotten" score of 28% and it holds a rating of 4.8/10 at the Internet Movie DatabaseShaun vs. the B-Movies gave a score of 5/10 saying "Personally, I got more unintentional entertainment out of this than I expected so I’ll bump the rating a notch for this train wreck of a film." Demon Wind was released on VHS in the U. S. by Prism Entertainment in conjunction with Paramount Home Video in 1990. The release was known for its 3D lenticular video cover. In August 2017, Vinegar Syndrome announced they would be releasing the film on a special edition Blu-ray in October 2017.
Demon Wind on IMDb