asphalt mixing plant

How to modeling Asphalt Mixing Plant In ChinaSection 22.5 Fuels complete combustion and increased heat effectiveness are basic requests for the performance of asphalt mixing plant. Inside dryer drum, there are mainly two sections, one combustion chamber and the other heat exchange chamber. Combustion chamber should assure complete combustion, its rational length should not be too long, hence short and wide flame burners are recommended, this kind burner can combust completely in one not long section of dryer drum, enlarge the heat-exchange areas for cold aggregates and hot air stream, at last yield increased heat effectiveness. 3. Mixing tower (also known as Batch tower) 3.1 Hot elevator should have device to avoid elevator inverted, replaceable abrasion resistant lining board should be installed at its discharge port. 3.2 Vibrate screen a) By-pass device should be installed at the inlet position of vibrate screen. b) Leave spaces around vibrate screen to facilitate the replacement of screen; electric hoist device should be available if installed at high positions. c) Vibrator device outside the vibrate screen and ease of maintenance.(normally use vibrate motors as drive of vibrate screen, and free of maintenance.) 3.3 Hot bins a) Compartments ≥5 (normally) b) Mineral wool thickness:≥100mm (normally) c) Continous level indicators, simultaneously indicate datas in the control room. d) Temperature sensors and remote control. e) Each compartment should have maintenance gate, sampling port and overflow device. f) Discharge gate of hot bins should in form of eccentric fixed mode. 3.4 Mixing tower should have oversize aggregates(waste material) / overflow material storage and discharge hoppers, one for oversize aggregates, one for overflow hot material. Each hopper has one discharge gate and discharge the materials periodically. 4. Weighing system a) Famous brand weighing load sensors, Heat-resistant seal material among each weigh hoppers, hot bins and mixer should be in easy replaceable structures. b) Automatically compensate materials to meet the required value. c) Asphalt should be measured by an secondary meter to calibrate its quantity (better with a frequency convertor to adjust its speed); asphalt weigh-hopper should have insulations for heat effectiveness, overweigh and overflow protection functions. Fluid asphalt is sprayed into the mixer. 5. Mixer a) Surge bins under the mixer could avoid leaking mix scattered onto the driver room of dump truck. b) The mixer and surge bins should have insulations to be heat-effective (hot oil heating will be better). c) Normally compatible ports for connecting hot/cold RAP, SMA, modified asphalt cement and fiber input could be preset; thus no need to reconstruct the plant and this facilitate the plant updating and reduce costs for customers. d) Manual periodical lubricating or electrical lubricating for all the rotation sections. e) Remote infrared ray temperature meter sense temperatures under the discharge gate, and signal to the operator in control room, thus he can compare it with the discharging temperature out of dryer drum.f) Lining boards and flights should be durable for use of more than 100,000 times mixing. g) Maintenance gates have control switches. 6. Pneumatic System a) Protective devices protect the system in response to undesired air pressures. Control system must preset undesired air pressure value and alert to the operator if the air pressure is not desired, hence in this condition, all valves and devices should not be activated to assure the plant working in a stable mode. b) Exhaust valve should be supplied for maintenance and maintainers safety. c) Use famous / good quality pneumatic devices and air compressors (Screw air compressors often give stable air pressures) d) Normally dustproof room for air compressors, reservoirs tank and compressed air drier is intended to prolong compressors service life, assure constant air pressure and air supply, dry off moisture in the compressed air and increase the performance of pneumatic cylinders and electrical magnetic valves. e) Protective fence should cover outside of cylinders and openings for workmans safety. 7. Dust Pollution Control 7.1 Normally gravity(inertia) dust filter used together with baghouse dust filter. Dust emission from the baghouse dust filter will be ≤20mg/Nm3,Ringelmann Black number ≤I grade. 7.2 The cloth of filter bags in 2mm thickness, its weight per square meter will heavier than 450g, this filter bag should be able to withstand 250 celsius degrees instantaneous temperatures. 7.3 Normally clean mode is air-reverse-blow. 7.4 Exhaust fan uses famous / good quality brand, air gating device normally could be adjusted in connected response with the burner (frequency converter to control speed will be better). 7.5 Filler recycle mode: coarse particles collected by primary dust filter will be conveyed to hot elevator by screw conveyors; fines collected by baghouse dust filters will conveyed and elevated to filler reclaim bins through screw conveyors and elevator. Normally do not intend to use pneumatic method to convey the reclaimed fillers. 8. Filler Supply and Storage System 8.1 Pulse dust filter and automatic pressure unloader should be installed with the filler bin; air/pulse burst devices to prevent filler powders stick and blocking due to moisture; level indicators (continuous type will be better). 8.2 If tank truck is not available for pneumatically feeding fillers to filler bin, filler elevators should be supplied. 8.3 For companies, recycled fillers are not allowed for use, filler wetting device should be supplied to decrease the pollution caused by recycled filler particles. 9. Asphalt supply/storage and hot oil heating system 9. 1 Asphalt tank a) normally mineral wool thickness ≥100mm, energy effective and environmental; b) Asphalt heated/yielded temperatures can be automatically controlled. c) For companies use SMA modified asphalt, device against segregation should be installed onto at least one asphalt tank. d) To companies with none of asphalt storage warehouse, steel structure asphalt feed tank(hot oil heated) should be supplied and relative pumps are also included in supplies. e) Fluid level indicators should be supplied, when asphalt tank comes full or run out, flashes and sounds will alert the operator. f) should have man hole, ladders and maintenance platform. 9.2 normally thicker than 50mm mineral wool should be jacketed around the asphalt and hot oil pipelines; to avoid leakage, pipelines connection point use metal seal linings. 9.3 Only when the company get qualified certifications can it design, produce and install hot oil heater and pipelines. 9.4 Asphalt pumps, valves and pipelines should be heated by circulating hot oil.