DESIGN GUIDE FOR AIR SLIDE CONVEYOR No
Subject
Requirement (Rule of thumb & Application)
1 2
Aerated bulk material density Appl Applic icat ated ed mate materi rial al dens densit ity y for for air air sli slide de conv convey eyor or
0.66 multiply by bulk density 5 up up to to 200 200 lb/f lb/ft^ t^3, 3, For material has angle of repose 35 up to 40 deg is categorized as most free flowing material (Book)
3
Pressure required for close type conveyor
· For bulk density ≤ 70PCF - 20inch WG in plenum chamber · For bulk density > 70PCF - 27inch WG in plenum chamber
4
400 mmWG ≡ 40mBar Permeability and pressure drop of Porous of Porous DIAPHRAM unknown Perm ermeabil bility 1.5 1.5 m^3/ ^3/m^2 m^2.min, min, Press essure dr drop 100mmWG (1 (10mBar)
5
Mini Minimum mum sug sugest ested ed conv conveyo eyorr angle angle
8 deg, but may be as low low as 6 degrees depending on product material type.
7 deg, currently aplicated on Tonasa V project is 7 deg (not as minimum but applied conveyor angle)
References and notes DCL, if aerated bulk density is not known DCL
DCL, 70PCF ≡ 1.24ton/m^3 20 inch WG ≡ 50 mBar 27 inch WG ≡ 67 mBar FLSmidth DCL FLSmidth → For case P630, length 35m and diaphram area is 0.63*35 = 22.05 m^2, check fan capacity selected from graphical table 43m^3/min (40mBar) → Air flow rate through Porous Membrane= 1.5m^3/m^2.min * 22.05m^2 = 33 m^3/min --------------------------------------------------------∴ Safety factor for air flow rate for fan according to porous membrane requirement is about 43/33 ≈ SF1.3 DCL , Most product suitable for air gravity conveying are handled on a conveyor sloped at between 6 and 12 degrees. The slope can be reduced to 1 or 2 degrees for product which have excellent fluidizing characteristics. FLSmidth, The areated material flows like a liquid at a suitable inclination of the conveyor o
o
(4 -15 ) depending on the type of material conveyed
6a The volume of free air required (Fan flow rate)
10 SCFM (Standard cubic feet per minute) per square foot Dimension of air slide conveyor of DCL A=24 inch (2 ft), length=35m (115 ft) Membrane area = 2 x 115 (ft^2) = 230 ft^2 -------------------------------------------------------Free air requirement = 10 SCFM/sqft * 230 sqft = 2300 SCFM (65 m^3/min) ∴ Fan flow rate = standard 65 m^3/min
6b
DCL The volume of free air required for most applications is approximately 10 SCFM per square foot of conveying media when handling a product like cement, fly ash, phosphate rock dust, and lime products. However the air requirements may vary for other materials from 4 to 15 SCFM (standard cubic feet per minute) per square foot. In conveying alumina and bauxite, the air requirement for fluidization can be as little as 4 SCFM. Please be aware that there is no definite formula for calculating the volume of free air required. In order to establish the proper air requirements for materials not previously handled, DCL offers testing at their facility Handbook of pneumatic conveying engineering Chapter 18. Fluidized motion conveying system Basic property of cement portland: 1. Bulk density : 1,070kg/m^3 ≡ 67lbs/ft^3 2. Particle density : 3,060kg/m^3 º 191lbs/ft^3 3. Mean particle size : 14µm -------------------------------------------------------------Taken from table that (approximation) Terminal velocity needed is 5ft/sec ≡ 0.025m/s Porous membrane area is 230ft^2 ≡ 21.37m^2 → Fan flow rate is 0.025m/s*21.37m^2 ≡ 0.534 m^3/s ≡ 32m^3/min → SF=1.3 (FLSmidth - previous result) -------------------------------------------------------------------------Fan flow rate requirement = 1.3 * 32m^3/min ≈ 42m^3/min ∴ Fan flow rate = standard 42m^3/min
6c
FLSmidth Fan flow rate based on P630 and conveying distance 35m is 43 standard m^3/min ∴ Fan flow rate = standard 43m^3/min
7 8
Air supply interval Air pressure for open type conveyors installed in silos or hoppers are generally determined by the head of product over the conveyor
Up to 100 m Air pressure for all material: • head product over conveyor, H< 2ft - 1PSI • head product over conveyor, 2≥H<15ft - 2PSI
• head product over conveyo, H>15ft - 6PSI Except for alumina, pressure of 3 PSI is adequate regardless of head 9a Standard dimension of conveying channel
FLSmidth DCL, pressure up to 1PSI can be supplied by centrifugal blower and pressure greater than 1PSI should be supplied by positive displacement blower . A high pressure compressor plant is not recommended for use in supplying fluidization air as this source is considered “dirty air” meaning the presence of water and oil Fuller® Airslide™ Conveying Technology, FLSmidth For example, Material Cement Portland (A36M/A16M) A36M: 1.27 up to 1.75 ton/m^3 A16M: 1.06 up to 1.32 ton/m^3 Angle of repose 30-44 deg For A=600 Nominal capacity > 1,500 m^3/h For A16M Cement portland, the capacity is > 1,500 ton/h
9b
DCL 24 inch (600 mm) - 39,000 ft^3/h ≡ 1,100m^3/h For A16M Cement portland, the capacity is > 1,100 ton/h
9c
9d
FLSmidth For example, For P630, capacity range is from 250 up to 1000 m^3/h For A16M Cement portland, the capacity up to 1,000 ton/h Conveying angle minimum 4 deg , apllied 7 deg For 35m conveyor length, Fan capacity 35m^3/min (based on 400mmWG air pressure)
Conveyor box width (b) ≈ 0.65 (mass flow rate/particle density)^0.5 Mass flow rate = 800 ton/h Cement portland (non aerated) density = 72 ~ 99 lbs/ft^3 → 85lbs/Ō^3 0.5 as aspect ratio (depth/width of flowing bed) --------------------------------------b ≈ 0.65 (800/85)^0.5 ≈ 2ft ≈ 610mm
Handbook of pneumatic conveying engineering Chapter 18. Fluidized motion conveying system
