STACK ANALYSIS MONITORING STACK S AMPLING
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- 2. • Particulate matter - SPM, Fluoride , Lead, PAH Temperature , Velocity, Flow • Gaseous pollutants – Routine parameters- O2 , CO2 , HC , CO SO2 , NOx Acid mist as HCl /H2SO4 Cl2 , NH3 , H2S 2
- 3. Selection of Sampling location and Minimum Number of Traverse Points • Select the sampling location at any cross section of the stack at least eight stack diameters downstream (8D) and two stack diameters upstream (2D) from any point of flow disturbance (bend, expansion, contraction, visible flame, or stack exit) • Cross section of stack is divided into a number of equal areas where traverse points are located • Determine the number of traverse points required. Inside diameter of stack or duct (m) Number of points I.D. ≤ 0.3 4 0.3 ≤ I.D. ≤ .6 8 0.6 ≤ I.D. ≤ 1.2 12 1.2 ≤ I.D. ≤ 2.4 20 2.4 ≤ I.D. ≤ 5 32 3
- 4. Location of traverse points on circular cross section 4 For circular stack divide the cross section into equal parts by two right-angle diameters, locate half the traverse points symmetrically along each diameter.
- 5. Rectangular stacks • Equivalent diameter shall calculated first, De = 2 (L) (W) / L + W • Determine the number of traverse points • Determine the grid configuration 5 Number of Traverse points Matrix Layout 9 3x3 12 4x3 16 4x4 20 5x4 25 5x5 30 6x5 36 6x6 42 7x6 49 7x7
- 6. Location of traverse points on rectangular cross section 6 Divide the stack cross-section into as many equal rectangular elemental areas as traverse points, and then locate a traverse point at the centroid of each equal area
- 7. If (8 D – 2 D) criterion cannot be met • Determine the distances from the measurement site to the nearest upstream and downstream disturbances • Divide each distance by the stack diameter or equivalent diameter, to determine the distance in terms of the number of duct diameters. • Determine from Figure the minimum number of traverse points that corresponds: (1) to the number of duct diameters upstream; and (2) to the number of diameters downstream. • Select the higher of the two minimum numbers of traverse points. 7
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- 9. Location of traverse points on diameters of cross section of circular stacks 9
- 10. Example showing circular stack cross section divided into 12 equal areas, with location of traverse points 10
- 11. • For stack having dia. > than 0.61 m , no traverse point shall be located within 2.5 cm of stack wall. • For stack diameters < than 0.61 m , no traverse point shall be located within 1.3 cm of stack wall. • If any traverse points falls within 2.5/1.3 cm of stack wall, relocate them away from stack wall. • For elliptical stacks having unequal perpendicular diameter, separate traverse points shall be calculated along each diameter. • Use same traverse points and locations for velocity and particulate measurements. 11
- 12. Location of sampling port • To ensure laminar flow, 8D- 2D i. Number of sampling port – min. 2 ports are required, so that full cross- sectional area of stack can be covered for measurements. ii. Dimensions of sampling port – standard flanged pipe of 0.10 m inside diameter with 0.15 m bolt circle diameter. Port should extended outward from the exterior stack wall not less than 40mm, installed at height between 0.90 and 1.2 m above the floor of working platform. iii. Platform – If two ports are required at 90o , half of stack circumference and If four ports are required, entire circumference ; minimum platform width shall always be 1.2 m iv. Platform access – caged ladder, stairway, rooftop v. Platform loading – support load of at least three men and equipments vi. Power supply – At platform and stack base 12
- 13. 13 ˃ Position of sampling ports in a circular stack
- 14. Iso-kinetic sampling • Obtaining representative particulate sample • Kinetic energy of gas stream in stack should be equal to kinetic energy of gas stream through the sampling nozzle • If sampling velocity is greater than velocity in duct tube will suck extra particles, collecting higher percentage of smaller particles, the sampling will have a lower mass concentration • If the sampling velocity is less than velocity in duct then tube will became pressurized and particles will want to be expelled from the tube. The particles more easily dispelled are small particles resulted into collection of larger particles ,PM has a higher mass conc. 14
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- 16. Stack Temperature and Velocity Measurement • VVM-1 • Temperature- Has a digital pyrometer and thermocouple. • Velocity- A digital pressure cell (for measurement of pressure in mm of H2O) along with pitot tube. 16 Thermocouple Inter-connection tubings Carrying case Extension for pitot tube Pitot tube Pyrometer Digital pressure cell
- 17. VVM1 - Specifications i. Temperature range :- Ambient to 600o C ii. Velocity range :- 0 to 100 m/sec iii. Thermocouple sensor :- length= 0.6m with 2m long cable iv. Manometer :- With 0 – 1300 mm of H2O range v. Pitot Tube :- S type, 0.6m length with extension of 0.6m. vi. Inter-Connection tubings :- for inlet and outlet gas connections 17
- 18. Stack Temperature and Velocity Measurement • APM 602 • Temperature- Has a digital pyrometer and thermocouple. • Velocity- An inclined cum vertical manometer along with pitot tube. 18 Pitot tube Thermocouple sensor Manometer Digital pyrometer Inter-connection tubings Spirit level
- 19. APM 602 - Specifications i. Temperature Range : Ambient to 600°C ii. Velocity Range : 0 to 30 m/sec iii. Thermocouple sensor : Stainless steel, length of insertion : 1m with 2m long cable iv. Manometer : Inclined/vertical Glass Borosilicate tube with spirit level attached for levelling, max. of 50m/s with red oil & Range increased to 75m/s with CCl4 v. Pitot tube : Modified S-type ,length- 1m, 1.5m, 2m and 4m vi. Interconnection : 3 m long, synthetic rubber tube. 19
- 20. Temperature Measurement • Thermocouple is connected with the Pyrometer • Switch on the pyrometer to measure the Ambient temperature (Tm) • Insert the thermocouple sensor into the stack through sampling port • Allow the temperature to stabilize for atleast 10 minutes • Record Stack temperature (Ts) from pyrometer • Remove the thermocouple • Hold the sensor by its handle, it is likely to be hot. 20
- 21. Stack gas velocity determination • Connect two ends of the manometer marked “pitot” to ends of Pitot tube (pitot end which has mark is connected to ‘+ve’ end of manometer) • Manometer sets to zero before hoses are connected • Insert pitot tube into stack keeping marked end of the tube facing the air stream • Plug the clearance between the port hole walls and pitot tube with asbestos wool to prevent air flow through port hole • Orient the pitot tube axis and search best alignment (highest reading ) • Note the manometer reading at various traverse points • Disconnect the pitot tube when entire cross-section of stack has been traversed 21
- 22. Pitot tube with Manometer 22
- 23. Type S pitot tube 23
- 24. i. Stack gas velocity V = k (2GH Dm/Ds)1/2 here Ds = Da x Ta/Ts V = 0.2043 x (H x Ts)1/2 where, V = Air velocity (m/sec) k = Pitot calibration constant (0.890) G = Acc. Due to gravity, 9.81 m/sec2 H = Manometer reading in mm H2O Dm= Density of manometer fluid (1000 kg/m3 for H2O) Ds = Stack gas density ( kg/m3 ) Da = Density of atm. Air (1.25 kg/m3 ) Ta = Ambient air temperature (K) Ts = Stack gas temperature (K) 24
- 25. ii. Stack gas volumetric flow Rate The following equation is used to calculate Qs. Qs = V x 60 x 1000 x Tm/Ts x A where, Qs = Flow rate (lpm) V = Velocity of stack gases (m/sec) A = Cross - sectional area of nozzle (m2) Tm= Absolute ambient gas temperature (K) Ts = Absolute stack gas temperature (K) 25
- 26. Nozzles • Stainless steel (SS 304) with sharp tapered leading edges. • Minimum recommended internal diameter is 7 mm. • Select the nozzle size which provides meter sampling rate up to 30 LPM. • Nozzle Sizes :- 26 Nozzle (inches) Internal diameter (mm) Area (m2) 1/2 12.58 12.4 x 10-5 3/8 8.60 5.8 x 10-5 1/4 6.32 3.1 x 10-5 1/8 3.10 7.5 x 10-6
- 27. Sampling Period for Particulate matter • A minimum of 1 m3 of dry gas has been withdrawn for sampling. • The mass of particulate matter amounts to atleast 20 percent of the mass of the filtering medium in the sampler. • Sampling period should be of lesser duration in heavy dust concentrations. • Too short time may give unreliable results and too long a time may cause resistance of sampling train to exceeds capabilities of vacuum pump. 27
- 28. Sampling Period for Gaseous pollutants Period of sampling Rate of sampling (LPM) 30 minutes 2 1 hour 1 1 to 4 hours 0.5 8 hours 0.2 8 to 24 hours 0.1 to 0.2 28 Based on practical experience over the years of sampling in India, it is recommended that air sampling rates which give minimum of evaporation with reliable efficiency should be :-
- 29. Handy Stack Sampler APM-620 • The SPM is trapped and collected in a Filter media • Various gaseous pollutants are absorbed in suitable reagents, then analysed subsequently by simple wet chemistry methods to determine the concentrations. 29 Dry gas meter Vacuum pump Nozzle Filter holder Probe Sampler Hose pipes Rotameter
- 30. Handy Stack Sampler APM-620 i. Nozzles : A set of 4 stainless steel nozzles with internal diameter of 12.5mm, 98.6 mm, 6.3 mm & 3.1 mm. ii. Filter Holder : Stainless steel (SS 304), Suitable to hold (a) cellulose filtration thimble (size 28mm lD X 100mm long) (b) glass micro fibre thimble (size 19mm lD X 90mm long) iii. Sampling Probe : Made from SS 304 , 0.3m and 1 m in length iv. Impingers : 2 No. (240 ml) and 3 No. (120 ml) borosilicate glass impingers with Ball socket joints accommodated in ice tray. v. Rotameter : Used for flow measurement, Plastic body rotameter , 0 – 30 lpm for particulates and 0-3 lpm for gaseous pollutants monitoring vi. Dry Gas Meter : Mechanical Type with a range of 40 lpm flow rate. vii.Vacuum Pump : Monoblock Rotary Vane type, oil lubricated, 0.5 HP single phase motor (230V) with 50 lpm free flow capacity 30
- 31. Accessories with Stack Sampler • Heated Probe - for sampling of flue gases containing high moisture • Cyclone - for high dust concentration to avoid choking of thimbles as in cement plants • Flourine kit - for monitoring Fluorine / Fluorides • Carbon monoxide bottle - to collect samples with high CO levels as in Carbon-black plants and DG sets • Extension Vacuum Hoses - for sampling ports located at a distance • Differential Density Manometer - for monitoring velocities in low velocity conditions as in natural draft boilers. 31
- 32. Stack Nozzle 1st impinger set Silica gel impinger Rotameter Dry Gas meter Filter holder Probe Manifold 2nd Impinger set Stack gases Stack gases Sampling train for stack gases Two sets of impingers, one set as gas sampling impingers and the other set as moisture absorption and estimation impingers, are used Rotameter Vacuum pump Mercury manometer
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- 34. Filter media - Thimbles • Paper thimbles – used at temp. up to 150o C • Alundum thimbles – able to withstand high temp. up to 550o C, high wet strength, chemical resistance • Glass fibre thimbles – used in heavy dust loading conditions, able to withstand 550o C of temperature 34
- 35. THANKS 35