IN-LINE PARTICLE SIZING FOR PROCESS CONTROL IN NEW DIMENSIONS

CHINA PARTICUOLOGY Vol. 2, No. 4, 185- 188, 2004IN-LINE PARTICLE SIZING FORPROCESS CONTROL IN NEW DIMENSIONSWolfgang Witt, Michael Heuer and Markus SchallerSympatec GmbH, System-Partikel Technik, Burgtatter StraBe 6, D .38678 Clausthal-llerfeld, GemanyAbstract The combination of laser dffraction with upstream sampling realized a break-through for the in and on-lineparticles size analysis in industrial applications. Today, the combination of representative sampling, dry dispersion, parti-cle size analysis by laser dffraction and integrated feedback of the sample is well accepted in many industrial applica-tions. No more interactions of the user are required, and for standard applications the on.line monitoring of particle sizesbecame nearly as simple as the monitoring of any other process parameter. The increase of inspection interval from24-hour operation to months has increased user confidence in this technology, and industies with more demandingmeasurement requirements are seeking to benefit from this performance. This challenge could not be solved with simplescale-ups or scale-downs. New solutions had to be found for the sampling system, the measuring sensor, the adaptationto the environmental conditions and the processing of fast growing volume of data.Keywords in-line, particle size analysissplit samples, the remaining errors resulting from sampling1.Introductionstrongly dominate. So for reliable in-line particle sizeAn on-line system for particle size analysis (PSA) withanalysis representative sampling is of decisive importance.In a pipe the whole cross-section has to be scanned and allthe subsequent stages of representative sampling, effec~areas must contribute equally weighted. The mechanicaltive dry dispersion (Leschonski et al, 1984) and PSA by solution ofered by the TWISTER mechanics is shown inmeans of laser dffraction (LD) was already displayedFig. 1. The opening of the sampling tip is driven on a spiralabout two decades ago (e.g., Heuer & Leschonski, 1984).line with varying velocity v. The velocity is contrlled in aAs many subsequent process stages are connected by way that equal areas are scanned in equal times. Thepipes an innovative solution was offered by (Witt & Rothele,change of the aspect ratio of the opening due to the incli-1995; Witt & Rothele, 1998), which itegrated the complete nation is also taken into account. In the patented em-sampling and measuring system inside a pipe- repre- bodiment e.g. a system of connected levers is used, assenting a real in-line system. This solution consists outof displayed in Fig. 1. Combined with the rotation a nut istwo devices, the representative sampler "TWISTER" and driven on a vertical thread varying the value of z and hencethe subsequent dry disperser and PSA“MYTOS".the value rvia Eq. (1).1.1 TWISTER: the representative samplingstageH| ((H-1)(1)As modern LD PSAs usually have reproducibilty interms of standard deviations of less than 0.1% for wellO中国煤化工MYHCNMHGFig. 1 Let: tajetories of sampling orifice, centre: lever actin, right: sampling finger mechanics.186CHINA PARTICUOLOGY Vol. 2, No. 4, 2004This system offers many advantages:the partial flow for a reference measurement or idle●The partial flow is kept inside the process pipe, socondition. A scraper at the parking position cleansany pressure in the pipe does not affect the sam-the inlet.Finally the particles have to be sucked into the samplingpling.Space saving 90° elbows are avided. This reduces pipe. This is done qusisokinetic (Rothele, 1982), i.e, thewear.sampling is performed at nearly constant velocity of the●No moving gaskets and the use of bllws instead partcles. The cotollablel flow pump of the subsequent dnyallow for the operation in hazardous areas.disperser is used for this purpose.●Small moving masses enable a small drive unit.1.2 MYTOS: the dry dispersion and PSA stageAll parts accessed by the product flow have wideThe complete system is displayed in Fig. 2. The well.mechanical tolerances and can be manufactured outestablished dry disperser of RODOS is used for the dryof hardened material (e.g. ceramics).●The adaptation to dferent process throughputs φdispersion stage of the MYTOS. Particle-to-particle, parti-can be made by variation of the diameter d of thecle-to-wall collisions and centrifugal forces due to stronginlet cap. If d is smaller than all subsequent stages,velocity gradients smoothly disperse particles down to0.1 um. Although the lifetime of the dispersing line coversthe cap acts as a 'security screening' .Simple adaptation to diferent diameters D of themore than 100,000 measurements of 5 g Cement PZ35Fprocess pipe by variation of the length of the sam-the benefit of no eftect of wear during idle periods whilesampling pipe is in parking position, leads to lifetimes ofpling pipe.A parking position at the intersection point of theapproximately 2 years with 6 measurementshour. Addi-trajectories allows for a break without stopping in thetionally cleaning by an integrated flush-back stage safelyproduct stream, which would result in an overesti-avoids blocking.mation of that position. This also allows to interrupt| aitr inlet forinlet of parial flowfrom samplerl dry disperserI air inlet for flowI dispersing linefocussing andrinsingmeasuring zone[ light source & bean| expansion unitwindow| merging stage名| detector & dataacquistion untFourier opticsFig.2 Cross section of dry disperser and LD PSA, Sympatec "MYTOS" with 200/150 mm inner diameter.The subsequent LD system is identical in all major parts uring range. For the three measuring ranges from 0.25 umto the standard f-line LD PSA (HELOS). A separate con- to 875 um and the two ranges from 9 um to 3,500 μm dif-trol box comprises power supply, laser, the sampler and ferent optimized setups are used.disperser control unit and a fibre-optical communication| flow is re-combinedlink to PC. All components are encapsulated as IP65; with tl中国煤化工he centre line of thehazardous areas are supported as option.proceCNMHG_; wear at the processThe measuring zone is equipped with a flow focusing wallsmplete separation ofinjector, which concentrates the aerosol beam along the the PSA from the process.centre line and keeps the windows free of particles. TheIn combination with a cap in the parking position thismechanics of the measuring zone depends on the meas- creates a bypass inside the pipe and enables cleaningWitt, Heuer & Schalle: In-Line Particle Sizing for Process Control in New Dimensions187while the process is running. Bayonet fastenings of the detected very near to the centre of the detector, i.e. to thelight source and detector unit simplify the serviceability.bright focal point.Basing of this concept a complete family of TWISTER|(r)=6e23iw'and MYTOS units have been developed, currently covering十Working distanceFourier lensDetectorprocess pipe diameters from 50 to 200 mm and particlesRosize ranges from 0.25 μm to 1,750 um. Their performancehas been proven in various applications.一可2. Scale-ups and Scale-downs(6)For process pipe diameters larger than 200 mm theParticle ensemblesampling tube cannot be elongated ofthand. The enhanced Fig.3 Spot diameter w as functin of the required beam diameter 2W%.forces had to be taken into account. Completely new con-cepts for mechanics, sensor technologies, control, elec-Ideally the beam diameters have to be adapted to thetronics and operating sequence had to be developed and measuring range. Up to -500 mm (Xmax<875 um) it is pos-were accomplished. Currently pipe diameters up to sible to use a relatively small beam diameters of 3 mm to660 mm are supported.10 mm and a multi-chamber system is suficient to avoidScale-downs to pipe diameters below 100 mm require contaminations of the windows. From =1000 mmthat the drive unit of the TWISTER and the MYTOS have to (xma=1750 um) on the beam must have a minimum dibe moved outside the pipe. For 50 mm diameter a new ameter of 30 mm to keep the focal point sficintly small.sampler has been developed, that still performs the scan Here a multi chamber system would be in the size of theon a spiral line and incorporates a parking position. Aquick tube diameter. So a new concept had to be developed: arelease mechanism for all components fllows the cleaning special flow chamber with the advantage of less gas con-request in pharmaceutical aplications. The device is best sumption and small design. In adition a new Fourier Op-suited for the control of small cassrimili combinatins. tics was developed, in order to improve the mechanicalEven more demanding is the extension to larger parti stbility. Now an optical system with f-2000 mmcles. The output of a laser has usually a Gaussian intensity (Xmax =3,500 um) fits in a cyinder with a length of onlydistribution () with 2Wo seciying the fll width at /b=1/7. 300 mm. Fig. 4 shows the design. The unit has to be op-As the dfraction pattern on the detector is the Fourier erated verically.transform of the spatial distribution of the particles and theFinally the software has to be scaled-up as well. Cycleiluminating beam, the centre of the detector is also ilumi- times down to about 1 minute and the combination of sev-nated by a Gaussian intensity distribution. The width wis eral PSA in a single process create an enormous amounttransformed by Eq. (2), which defines diameter of the focal of data - up to about 500,000 measurements per sensorpoint. This means that the beam itselft reacts as a large and year. So the concept of the controling software had toparticle, which is transformed.be expanded. A new powerful database (INTER-BASETM),Afthe implementation of a well defined client/server structureW=;(2)πW,and an integrated security systems compliant with CFR 21For the analysis of large particles it is important, thatRule 11, allows for the unlimited parallel operation of sev-W>>Xmax because large tocal lengths fhave tobe usedfor eral PSA units and is proven to handle more thanthe measurement and significant intensity has to be 100000 data sets.| ary disperee wth nner| Puses fushesthel dametera 10 mmdefteter unt wthpreceding Fouer opecsight source wthDeam erpansicn| pech wave enclbc中国煤化工urngthedle stateMHCNMHGFig.4 Dry disperser and PSA with new flow concept for focal length of 2000 mm (xmax=3500 um), Sympatec "MYTOS".188CHINA PARTICUOLOGY Vol. 2, No. 4, 20043. ApplicationsWhile the challenge of the first example in Table 1 is thevery low concentration, the very high air velocity and theOut of a variety of aready established aplications, the high temperature with temperature change, the callengefollowing two examples are specified in detail: Metalof the second in Table 2 and Fig. 5 is the large maximumspraying and coal milling.particle size, the sticky material and the high throughput,which required a pre-sampling unit.Table 1 Specifications of process parameters, insallation ofTWISTER 660 mm中and on-line MYTOS4. ConclusionsMetal spraying of aluminumThe combination of representative sampling, dry disper-Particles up to400 μmsion, particle size analysis by laser difraction has createdProduct temperature100°Ca powerful family of devices, suitable for in-line and on-lineMass flow rate1000 kg-h'particles size analysis of dry powders and suspensions.Air flow rate60,000 m3.n'Air velocity40 m-s'Several scale-ups and scale-downs possible within thisTube diameterDN 660 mmtechnology have been performed and have, widened thePressure0.1 barfield of applications. Currenty, particle size ranging fromSet upupside down0.25 um to 3,500 um and pipe diameter ranging fromTWISTER sampling time2050 mm to 860 mm are covered. Aplications at high tem-Distance MYTOS - PC200mnn:deperatures, for high particle velocities, low concentrations,ATEX zone 20 insidezone 22 outsideAntistatic designabrasive or sticky particles in standard or hazardous areas(also fllowing the new ATEX 20/200 standard) have beenTable 2. Specifications of process parameters, insallation ofsuccessfully implemented. The new software allows for theMYTOS, (Xmax-3500 um)parallel operation of many PSAs on the same database. Itcan handle very large volumes of data, as acquired overMilling of raw coalyears, and is fully compliant with CFR 21 Rule 11.Xxg0-3000 um40°CReferences400 th'Distance MYTOS- PC200 mHeuer, M. & Leschonski, K. (1984). Erfahrungen mit einem neuenGerat zur Messung von Partikel-groBenvereilungen ausBeugungsspektren. 3. Europ. Symp. Pariemestechnik inNimberg.Leschonski, K., Rothele, S. & Menzel, U. (1984). A Special Feederfor Difraction Patterm Analysis of Dry Powders, Part. Charact. 1(pp.7- 13).Rothele, S. (1982). Vertahren zur geschwindigkeits-gleichen Ab-saugung mit iferenzdrucksonden. Staub - Reinhalt. Luft,42(1), 6- 10.Witt, W. & Rothele, S. (1995). Laser dffraction - unlimited? 6.Europ. Symp. Particle Charact, (pp.227-290).Witt, W. & Rothele, S. (1998). In-line laser dfraction with innova-tive sampling. 7. Europ. Symp. Particle Charact. (pp.611-624).Fig. 5 Dry disperser and PSA with new flow concept for focal lengthof 2000 mm (xrmxr 3500 um), Sympatec "MYTOS".中国煤化工MYHCNMHG