1、International Standard INTERNATIONALORGANIZATION FORSTANDARDIZATION*MEX,4YHAPOflHAR OPTAHMBAIJHR DOCTAHAAPTH3AUWiRGANlSATlON INTERNATIONALE DE NORMALISATION Cleaning equipment for air and other gases - Classification of dust separators Skparateurs akrauliques - Classification des d.Gpoussi - impinge
2、ment; - centrifugal. 3.1.1 Gravity separators Inertial separators in which the particles are sedimented under the effect of gravity. Example : Settling chambers. 3.1.2 Impingement separators Separators in which the dust-laden flow is forced to make various changes of direction. The particles which f
3、ollow less curved trajectories than the lines of the gaseous flow, move towards depositing surfaces, along which they descend by gravity to discharge hop- pers. Example : Baffle chambers. D i 0 v 1) At present at the stage of draft. 1 Copyright International Organization for Standardization Provided
4、 by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6584-1981 (El 3.1.3 Centrifugal separators Inertial separators which employ a rotating flow. The particles are separated under the effect of cen- trifugal forces from the gaseous flow
5、 and are released in a radial direction. Examples : Cyclones, multicyclones. 3.2 Wet separators Separators in which forces are applied to promote the transfer of particles from a gaseous flow to a liquid phase which is later removed from the gaseous flow by other mechanisms. 3.2.1 Bubble washers Wet
6、 separators which employ fixed or movable elements immersed in the scrubbing liquid to bring about intimate contact of the particles with the scrub- bing liquid. Examples : Turbulent scrubbers (or flooded beds), fixed or mobile packed towers. 3.2.2 Spray washers Wet separators which employ a liquid
7、spray generated by pressure, impaction or some external energy source, to bring the particles into contact with the washing liquid. Examples : Spray washers, wet cyclones, disintegrators, rotating paddles. 3.2.3 Restricted flow scrubbers Wet separators in which the particles are brought into contact
8、 with the washing liquid in a restricted zone which causes a change in pressure or velocity conditions in the flowing gas. Examples : Venturi or orifice scrubbers, induced gas scrubbers, flooded disks, ejectors, electro-dynamic venturi. 3.3 Porous layer separators Separators in which the gas passes
9、through a porous layer which retains the particles. 3.3.1 Fibrous filter separators Filtering separators where the particles are separated by means of a medium consisting of natural, mineral, synthetic or metallic fibres which constitute a woven or an unwoven material. These filtering media are gene
10、rally in the form of bags or pockets. Examples : Bag filters, pocket filters, panel filters. 3.3.2 Packed tower separators Filtering separators where the particles are separated by mineral, metallic or other materials which form a layer of packing. Example : Gravel bed filters, 3.4 Electrostatic pre
11、cipitators Separators in which the gaseous flow is subjected to an emission of ions which charge the particles. The charged par- ticles are attracted towards surfaces of different polarity to which they adhere. They are periodically or continuously detached from the surfaces by rapping or washing, a
12、nd descend under gravity to discharge hoppers. Example : Electrostatic precipitators, plate or tube type. 4 Definition of dust separator characteristics 4.1 Data to be established The data to be established for a dust separator are the parameters required for determining the characteristics of the d
13、ust separator, i.e. the parameters which enable estimates to be made of the manner in which it fulfils its function. The prin- cipal data required for designing a dust separator are as follows. 4.1.1 Nature and physical characteristics of the gas at the inlet of the separator - Chemical composition.
14、 - Water content. - Absolute pressure Pt. - Absolute temperature Tt. - Density , . - etc. 2 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ISO6584-1981(E) 4.1.2 Flow rat
15、e of the gas stream at the dust separator separator inlet is constant : inlet qml (kg/s) or qvl h3kJ c, - qm1 qv1 The flow rate of the gas stream at the dust separator inlet is the mass or volume of gas which passes through the inlet section of the dust separator in one second. In the case of mass f
16、low rate, it should be specified whether or not this takes into account the mass of the suspended particles. expressed in kg/m3 (practical unit : g/m$ When the volume flow rate is expressed at standard con- ditions : The volume flow rate is usually reduced to standard conditions CT, E,) by two conve
17、ntional methods : c 1 = qmcl or c = qnd l- 9voD qvoH a) by taking account of the dry gas only, i.e. subtracting expressed in kg/m3 dry (practical unit : g/m3 dry) or in the water content. kg/ma wet (practical unit : g/m3 wet). This defines the dry volume flow rate (qvo,) under standard conditions :
18、b) when the mass flow rate qml of the gas at the dust separator inlet is constant : qvoD = q”, x (P, x -5 PO Tl C, _ qnnc1 4ml b) by assuming that the behaviour of the water vapour is that of an ideal gas. expressed in kg/kg (practical unit : g/kg). This defines the wet volume flow rate, (qvoH) unde
19、r stan- dard conditions : cl if the mass flow rate varies by vapour exchange, it is possible to relate the dust concentration Ct” to unit mass of the dry gas. qvoH = 41 x U-,) To -X- PO T1 where q, is the actual volume flow rate; P, is the actual pressure of the gas (absolute); 4.1.4 Concentration o
20、f particles at the separator outlet The maximum concentration of particles at the separator outlet is often fixed by regulations concerning pollution of the environment or work place; it may also be fixed in relation to economic or safety constraints. These values of maximum concentration associated
21、 to parameters defined in this clause contribute to the choice of the type of separator. T, is the actual temperature of the gas (absolute); p is the partial pressure of water vapour at tempera- ture T, and pressure Pt (absolute); PO is the pressure for standard conditions, 101 325 Pa; To is the tem
22、perature for standard conditions, 273 K. 4.1.5 Nature of the particles and their physico-chemical properties - Density. - Particle size. - Shape factor. In all cases, it is necessary to indicate the choice made between the dry volume flow rate and the wet volume flow rate. If the flow rate is not co
23、nstant, it is advisable to specify its variation over a certain time. - Solubility. - Hygroscopicity. - Abrasiveness. 4.1.3 Concentration of particles at the separator inlet, Cl, Cl or C,” - Angle of repose. The concentration of particles in the gas flow at the separator inlet is the ratio of the ma
24、ss flow rate of these particles (q,ncI) to the flow rate of the gas. - Resistivity. - Chemical composition. Distinction is therefore made for the following situations : - Flammability. a) when the volume flow rate qvl of the gas at the dust - etc. 3 Copyright International Organization for Standardi
25、zation Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6584-1981 (El 4.2 Main characteristics of dust separators Separators are mainly characterized by the mass of particles (121 at the separator outlet. If established data
26、 are known for the outlet and the inlet of the dust separator, its efficiency can be expressed by one or more of the following values.” 4.2.1 Overall efficiency of separation, 7 The overall efficiency of separation is equal to the ratio of the mass of particles retained by the dust separator (m, - I
27、Q to the mass of particles which enters it (ml) within the same time interval. (It is usually expressed as a percentage.) ml - m2 rl= “1 4.3 Secondary characteristics These secondary characteristics also need to be specified. 4.3.1 Flow rate of the treated gas c/, (kg/s) or 4,.2 (n-3/s) 4.3.2 Temper
28、ature at the outlet, r, (K) 4.3.3 Pressure drop across the separator, dp, (Pa) This is the difference in total pressures between the inlet and outlet of the dust separator. where m2 is the mass of particles leaving the separator. 4.3.4 Power requirements (kW) 4.2.2 Grade efficiency, qg The grade eff
29、iciency, usually expressed as a percentage, is the efficiency of the dust separator for each fraction of dust of a given particle size. 42.3 Cut diameter This is the diameter of particles (assumed to be spherical) at which the grade efficiency falls below 50 %. It is assumed that larger particles ar
30、e arrested and that smaller particles pass through the separator. NOTE - This is a theoretical concept which is generally not applicable to dust having a complex particle size distribution and it is not ap- plicable to most dust separators other than certain mechanical dust separators. These are as
31、follows : - the power necessary for the functioning of devices, such as automatic shakers, rotary dischargers, etc.; - the power absorbed by apparatus used in electrostatic precipitators, particularly high tension generators; - the power necessary for the use of pressurized water or compressed air;
32、- various other forms of power. The following also need to be considered : a) the mean power absorbed by auxiliary units : 4.24 Penetration, w Penetration lor slip), usually expressed as a percentage, is equal to the ratio of the mass of particles leaving the dust separator (m2) to the mass of matte
33、r which enters it (m,) within the same time interval. w=!2 ml 4.2.5 Amount of particles separated per unit time, qmc (kg/s) If qmrl is the mass flow rate of dust at the inlet and qmc2 the mass flow rate of dust at the outlet, the mass of the particles separated during unit time is given by the formu
34、la 4,nc = 4mcl - 4mc2 This is the amount of power consumed during a certain time divided by this time. If the plant does not function continuously, but has cyclic operation (periodic cleaning units, etc.), the power con- sumed has to be referred to the period. Certain elements which enter into the c
35、alculation of the mean power con- sumption shall be stated by the user. Example : Compressed air or pressurized water used in the distribution network of the factory. b) the installed capacity : The sum of the rated power of the machines which run directly all the elements required for the operation
36、 of the dust separator. This is considerably different from the mean power absorbed. 1) These characteristics refer to the total mass of dust or, in certain cases, to their chemical components (for example lead). 4 Copyright International Organization for Standardization Provided by IHS under licens
37、e with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 8584-1981 (El 4.3.5 Consumption of materials required for operation Two types of material are used in operation : - materials for washing, moistening, cleaning, such as water, oil, compressed air, etc.,
38、which are consumed con- tinuously; - materials used directly in the dust collector, such as filtering media, electrodes, etc., which have to be changed periodically. This consumption is related to a given period of time, for exam- ple ma/h, kg/month, mn/year, etc. 4.3.6 Storage capacity of the disch
39、arge chambers This is the mass or volume of dust that the discharge chambers of the dust separators can retain. It is expressed in kilograms, tonnes or cubic metres. The capacities varywith the nature and state of the dust. 4.3.7 Maintenance The periodicity of maintenance and the period of time duri
40、ng which the dust separator has to be stopped for maintenance, the different operations and the various materials required shall be specified. Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
