Haze caused by particulates can interfere with visibility, react with other pollutants to produce dangerous forms of pollution, interfere with air quality to the point that people have difficulty breathing
Inertial collection - Dust particles strike the fibers placed perpendicular to the gas-flow direction instead of changing direction with the gas stream. Interception - Particles that do not cross the fluid streamlines come in contact with fibers because of the fiber size. Brownian movement - Submicrometre particles are diffused, increasing the probability of contact between the particles and collecting surfaces. Electrostatic forces - The presence of an electrostatic charge on the particles and the filter can increase dust capture.
PRESENTATION TOPIC;Control of particulate emissions using cyclones Presentation by Komal Aroosh M.Sc (4th semester) DEPARTMENT CENTER FOR COAL TECHNOLOGY PUNJAB UNIVERSITY LAHORE
Control of particulate emissions using cyclones QUESTIONS What are the particulate emissions? Why its necessary to control the particulate emissions? What systems are available to control the particulate emissions? History of high efficiency cyclones What is agglomeration spray? Commercial applications of high efficiency cyclones Working principle Advantages disadvantages Can a cyclone reach efficiencies of ESP / Bag filter / Wet scrubber? Selection criteria Outlook
Control of particulate emissions using cyclones What are the particulate emissions? Particulate emissions are emissions characterized by the presence of small particles of solids and liquids. These common byproducts of combustion are a major health and environmental concern in many regions of the world, and steps have been taken to reduce particulate emissions and to educate people about their risks. These emissions are also known as particulate pollution or particulate matter.
Control of particulate emissions using cyclones Sources of particulate emissions Sources of particulate emission can be man made or natural. the vast majority of such emissions coming from factories around 10% coming from vehicles on the road. Combustion of fossil fuels also releases other substances and particulates into the air Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray.
Control of particulate emissions using cyclones Why its necessary to control the particulate emissions? Sometimes, particulate emissions are visible in the form of soot or smoke, because the particles are so large. Most are not visible, however, which is part of what makes them dangerous, because people do not realize that the emissions are occurring. Small particles are also more dangerous because they are less likely to be trapped in the mucus linings of the nose and throat.
Control of particulate emissions using cyclones Effect of particulate emissions on the humans If the particles, which can be composed of any combination of hundreds of chemicals and elements, are able to get through the defenses of the nose and mouth, then they can find their way into the lungs and possibly even pass into the blood stream. This can cause respiratory problems and potentially contribute to a higher risk for certain types of cancer or heart disease.
Control of particulate emissions using cyclones Effect of particulate emissions on the plants The particulates may block their leaves so that they cannot photosynthesize properly. The climate as a whole can be heavily impacted by such emissions, as they can block the sunlight so that it cannot reach the Earth. Cause a decrease in crop yields, and contribute to global warming trends.
Control of particulate emissions using cyclones Effect of particulate emissions on the animals For animals, particulate emissions pose a threat to cardiovascular and lung health. In the lungs, particulates can block or rupture the alveoli, interfering with lung function. A number of respiratory conditions including asthma and cancer are linked to exposure to particulate emissions. The heart muscle and blood vessels can also be damaged by particulates if they enter the bloodstream through the lungs, causing widespread medical problems.
Control of particulate emissions using cyclones Many stacks Are still emitting high levels of particulateBut particulate emission control requirementswill become more and more stringent
Control of particulate emissions using cyclonesWhat systems are available to controlParticulate emissions ? • Electrostatic precipitator • Bag house fabric filter • Wet scrubber • High efficiency cyclones
Control of particulate emissions using cyclones Main steps of ESP The processes of electrostatic precipitator are known as three main stages: particle charging transport collection.Evaluation of ESP: • High cost (investment, maintenance & operation) • Complex large size plant with sub-systems • Requires constant gas conditions (sulphur, temp, moisture)
Control of particulate emissions using cyclones Main process of bag house fabric filter Bughouses are very efficient particulate collectors because of the dust cake formed on the surface of the bags. The fabric provides a surface on which dust collects through the following four mechanisms: •Inertial collection •Interception •Brownian movement •Electrostatic forcesEvaluation of bag filters for industrial boilers: • High cost (investment, maintenance & filter bags) • Difficult to handle sulphur and sparks • Not robust (one faulty bag destroys efficiency)
Control of particulate emissions using cyclones Mechanism Main process of wet scrubber Wet scrubbers relay on the liquid spray to remove dust particles from the gas stream. It is also useful in fume extraction systems. It removes air pollutants by inertia of diffusional impaction, reaction with absorbent or reagent slurry or absorption into a liquid solvent. The inlet gas stream usually enters the bottom of the tower and moves upward, while liquid is sprayed downward from one or more levels. Evaluation of wet scrubbers for industrial boilers: • High cost (large water treatment plant) • Difficult to separate fine particulate • Sulphur control costly & difficult
Control of particulate emissions using cyclonesHistory:1975 - 1980 work with Prof. Stairmond (UK)Cyclones for coal fired gas turbine 80 MW PFBC1993 – 1998basic research incyclone technologyCape Towndevelopment center
Control of particulate emissions using cyclonesProject 1996 / 9730 year old Büttner solid fired wood chip dryer equippedwith low efficiency cyclone. Emission > 650 mg / Nm3Solution:Step 1 = retrofitting of high efficiency cyclones Reduction of emission to < 100 mg / Nm3First idea of agglomeration spray in 1997Step 2 = installation of THERMAX agglomeration sprays upstream of cyclones Reduction of emission to < 20 mg / Nm3
Control of particulate emissions using cyclonesWhat is the agglomeration spray?•Water spray with very fine droplets•Fully evaporative (dry system)•Droplets capture small particles•and agglomerate them•Larger particles are easily collectedTypical water consumption30 liter / t steam generation
Control of particulate emissions using cyclones High efficiency cyclone plant with fully evaporative fine agglomeration sprays (Installation 1997) Efficiency > 99 % Emission < 20 mg / Nm3
Control of particulate emissions using cyclones Cyclones Cyclones are inertial separators that operate on the principle of centrifugal force to remove particles from gas streams. A standard cyclone design is able to remove particles that have a size greater than 20 μm.
Control of particulate emissions using cyclones Cyclones Cyclones can be used as it is or combined with other control device. Cyclones are used to pretreat the gas stream by removing the purge particles while the second device will function to collect smaller particles present at a much reduced particulate loading but at higher collection efficiency.
Control of particulate emissions using cyclones The dirty airs enter the side. The airs swills around the cylinder. Particulate falls out from the bottom of the cone and out. Dust discharge
Control of particulate emissions using cyclones Working principle The working principle of the cyclone is as follow: The gas stream enters the cyclone in a manner that spirals around inside of the cyclones. The particles with a great inertia will be forced to the outside walls of the device. The particles will then fall to the cone to the collection hopper due to the collision with the outside walls of the cyclone. The clean gas will then rise near the center and is exhausted through the top of the device. There are two methods that cause the gas to spin in the cyclone. VII. One of its by introducing the gas to the device in a tangential manner. The gas will curve around the body of the device. VIII. The second method is by using axial vanes at the inlet of the cyclones which will cause the gas to spin when it passes through the vanes.
Control of particulate emissions using cyclonesCommercial applications of high efficiency cyclones: BurnerMax Fluidized bed furnace High efficiency cyclones operating at 400 C
Control of particulate emissions using cyclonesCurrent CyDesign specifications foradvanced cyclone technology:Integrated cyclone system withfully evaporative agglomerationwater spray (20 l / h per cyclone)To provide a robust, economic,low maintenance,very high performance,flue gas cleaning system
Control of particulate emissions using cyclones Cyclone parts are manufactured to high precision as erosion & corrosion resistant castings Wax diesCyclone vortex blade ringwith pressure recovery Castings
Control of particulate emissions using cyclones Advantages • Relative simplicity and few maintenance problems • Relatively low operating pressure drop (for the degree of particulate removal obtained) in the range of approximately 5–15 cm (2–6 inches) water column • Temperature and pressure limitations imposed only by the materials of construction used • Dry collection and disposal • Relatively small space requirements
Control of particulate emissions using cyclonesDisadvantages: Low collection efficiency due to: • Bad manufacturing quality • Lack of maintenance (blockage of cyclone cells) • Inability to handle sticky materialsBut cyclone system advantages are low cost and robust installationCan a cyclone reach efficiencies of ESP / Bag filter / Wet scrubber?This question triggered our cyclone development Programin 1994 to improve cyclone efficiency and to invent the “dry spray agglomeration principle”
Control of particulate emissions using cyclones Examples where the common control devices used Common control devices Pollutants Examples where they used Electrostatic precipitators Particulate matters Power plants ,steel and paper mills, cement plants ,oil refineries Bag houses fabric filter Particulate matters Steel mills, fertilizer plants and other industrial processes Wet scrubber Gasses ,vapors , solid particles, Coal burning power plants: liquid particles facilities that emit sulphur oxide, hydrogen sulphide,ammonia and other gasses that can be absorbed in the water and can neutralized with the appropriate reagent Cyclones Large particulate matters Wood working shops, cotton gins, rock crushers, cement plants
Control of particulate emissions using cyclonesSelection criteria ESP Bag house Scrubber High efficiency CyclonesEmission 100 30 200 < 100 mg/Nm 3Reliability ++ + ++ ++++Cost ++++ ++++ +++ +
Control of particulate emissions using cyclonesOutlook:Its necessary tocontrol theparticulateemissionsFor a cleanerEnvironment!