How is bottom ash collected?
This ash is dark grey in colour, and is about the size of sand. This ash is collected in a water-filled hopper at the bottom of the furnace and removed by high-pressure water jets. It is deposited in a collection pond and stored for disposal or later use after recycling.
What is bottom ash used for?
Bottom ash and ponded ash have been used as structural fill materials for the construction of highway embankments and/or the backfilling of abutments, retaining walls, or trenches. These materials may also be used as pipe bedding in lieu of sand or pea gravel.
What is bottom ash handling system?
The fly ash which is discharged from the bottom ash discharged from the bottom in a boiler furnace (clinker ash) is cooled, it’s picked out and the equipment from which this is conveyed to a storage place is called bottom ash handling system. A submerged scraper conveyor system is used at Europe mainly.
Why is there more concern about bottom ash?
Bottom ash not quite as useful as fly ash, although power plant owners have tried to develop “beneficial use” options, such as structural fill and road-base material. This isn’t a good idea, because the bottom ash remains toxic when recycled.
What is difference between fly ash and bottom ash?
During coal combustion, large amounts of ash are created along with carbon dioxide and other gases. The fine particle ash that rises up with the flue gases is known as fly or flue ash while the heavier ash that does not rise is called bottom ash; collectively these are known as coal ash.
Whats the difference between fly ash and bottom ash?
Fly Ash, a very fine, powdery material composed mostly of silica made from the burning of finely ground coal in a boiler. Bottom Ash, a coarse, angular ash particle that is too large to be carried up into the smoke stacks so it forms in the bottom of the coal furnace.
What is fly ash and bottom ash?
What is used to remove bottom ash from emissions?
Prior to exhausting the flue gas, fly ash is removed by particulate emission control devices, such as electrostatic precipitators or filter fabric baghouses (see Figure 1-1).
Which is better fly ash or bottom ash?
Fly ash produces a strong, durable concrete that is resistant to harsh chemicals. According to the American Coal Ash Association, fly ash offers these environmental advantages: The use of fly ash eliminates the need to mine virgin materials and conserves limited land and material resources.
Can bottom ash be used in concrete?
The appearance and particle size distribution of coal bottom ash is similar to that of river sand. These properties of coal bottom ash make it attractive to be used as fine aggregate in the production of concrete.
Is bottom ash combustible?
Bottom ash is composed of inert, non-combustible materials that are left over after the combustion process: sand, stones, ash from burnt material.
How is ash removed from the boiler?
Most of the ash from a pulverized coal-fired boiler is carried through the boiler and air heater by the flue gas. As much as 50 to 70% of the ash generated by combustion of pulverized coal is removed from the flue gas by a particulate control device, such as a fabric filter or ESP.
What is the difference between fly ash and bottom ash?
What is the specific gravity of bottom ash and river sand?
Meanwhile, the density of bottom ash is lower than the density of natural river sand as a result of the porous structure of bottom ash. Due to the porous structure, the specific gravity of coal bottom ash which is 2.21 is lower than the specific gravity of river sand which is 2.81.
What is the uses of boiler ash?
Beneficial uses include making portland cement, mixing with concrete, and stabilizing soils for road base. Fly Ash – The scrubbers in the flue use a lime slurry to reduce the amount of sulfur dioxide (SO2) escaping to the atmosphere and other toxic materials.
What is the specific gravity of bottom ash?
Specific Gravity: The specific gravity of bottom ash usually ranges from 2.1 to 2.7,(10) but values as low as 1.9 and as high as 3.4 have been recorded(11). Bottom ash with relatively low specific gravity (below 2.2) is often indicative of the presence of porous popcorn particles.
What is the specific gravity of fly ash?
2.1 to 3.0
The specific gravity of fly ash usually ranges from 2.1 to 3.0, while its specific surface area (measured by the Blaine air permeability method)(6) may range from 170 to 1000 m2/kg. The color of fly ash can vary from tan to gray to black, depending on the amount of unburned carbon in the ash.
What are properties of bottom ash?
Based on Table 1, usually bottom ash is classified as a class F as a result of SiO2 + Al2O3 + Fe2O3 that exceeds 70% as described in ASTM C 618. Therefore, due to bottom ash included in class F, it has pozzolanic properties and also has a very low lime (CaO) content which is less than 7%.
What is the density of bottom ash?
The bulk density of the bottom ash is 2.53 g/cm3 is higher than quicklime but closed to silica.
What is bottom ash and fly ash?
How do you get fly ash sample from a boiler?
Fly Ash Sampling Method 1. For boiler testing, the most practical way to draw a representative fly ash sample for tuning is by traversing the boiler exit with a high-volume fly ash probe, as shown in Figure 3. The process requires a sample tip directed into the gas stream with a filter canister to collect the fly ash.
What is the composition of bottom ash?
Bottom ash is the residue that is fused into heavy particles that drop out of the furnace gas stream (air and combustion gases). Table 10.3 presents the chemical composition properties of bottom ash. These particles are formed at the bottom of the furnace. Bottom ash consists of coarser and heavier particles than fly ash ( Torrey, 1978 ).
What is the difference between bottom ash and fly ash?
Bottom ash and fly ash produced from the same coal will have a similar chemical composition, although the bottom ash will likely contain an increased amount of unburnt coal and hence have an increased carbon content as well as a concomitantly higher loss on ignition, or LOI.
What are the uses of bottom ash?
Bottom ash is used as construction and railroad fill material, abrasive blasting grit, granules on asphalt roofing shingles, aggregate for concrete and masonry blocks, substitute for sand for traction on icy roadways, and soil amendment to increase permeability. Anand J. Puppala, Tejo Bheemasetti, in Ground Improvement Case Histories, 2015