Final Report Summary - ATEXDEDUST (Atex Deduster for small particles)
Executive Summary:
The generic goal of AtexDeDust project was the scientific investigation and first demonstration of suitability and viability of a new approach of industrial air cleaners. The idea behind the project aims for spatial and time controlled conditions inside the filter house. It excludes the contemporary appearance of potential explosive dust concentrations and ignition sources. An additional objective was the extension to nano-scale particulate separation along with high filtration rates.
The RTD-project AtexDeDust achieves the general objectives to implement the new technology in air cleaning systems. This improvement of technology covers the three key issues for more efficient and safer air cleaners:
• mobile instrumentation gaining clean air quality, that allows re-circulation directly or within machine integrated filter approach
• preventing conditions, which require explosion proof equipment
• extension of particle size range down to nano-scale
These general objectives will be reached by several technical, respectively technological changes in the deduster’s design. The most important ones are the splitting of the deduster house into two sections as well as the use of drum filter. The two compartments of the filter house are aimed at avoiding potential explosion risk. The implementation of the filter drum allows a more controlled regeneration of the filter surface, accompanied by remarkable low pressure loss over the filter. Latter is supported by specialised filter material and drum design. The specialised textile filter material supports very high filtration rates together with efficient separation of particulate sized down to the 1 micrometre scale. For dust separation with mainly nano-scaled fraction a pleated filter drum design was developed, which can be regenerated by sucking accordingly. Design and procedure are detected to be new and have been applied for patent. In lab scale the pleated filter drum along with a sophisticated filtration material show very high separation rates for pure and solely nano-sized particulate lower than 100 nm with filtration rates comparable to normal sized dust.
Beside the focus on filtration efficiency the RTD activities result in a set of technological investigations and procedures to shorten the time to market. These results include soft-ware tools to estimate the separation behaviour for detailed applications and the relevant dust concentrations insides. They include as well finding out technical components, reliable in operation under the rough environment inside the machine.
The project covers a 4-month demonstration of the innovative air cleaning technology on the floor.
Design and construction of this first demonstration unit was approved by Air cleaning Notified Body to be safe and avoids explosion risk.
The consortium set-up a favourable Use and Exploitation Plan and strives for turnover within the first post project year. The new realised deduster design lets expect not only economic benefit for the SME partner but provides beneficial features for clients and environment, saving energy in operation and allowing mobile as well as indoor installations.
Project Context and Objectives:
The AtexDeDust project was implemented to find a new approach for industrial air cleaners with scientific and technical objectives. The project was launched by a consortium of three SME from Germany, Poland and Denmark. According to the “Research for the benefit for SME”- FP7 framework two RTD-performer from Germany and Austria have provided scientific knowledge and cutting edge measurement resources.
Totally the project was split in three periods:
• Set-up of lab testers and investigation of basics of separation and regeneration behaviour of filter
• Elaboration of detailed scientific and technical aspects, able to be realised in industrial scale
• Design, realisation and test of a demonstration unit
The innovations of the project, aimed by an idea to avoid explosion proof installation of the cleaners in most of application cases, were determined by the fact that potential explosion risks appear during cleaning process. On raw gas side of the cleaner the dust concentration normally is so low that explosion levels won’t be reached. Collecting dust respectively dust layers on filter surfaces let grow the hazard for explosion significantly, in particular it let grow this hazard during regeneration of the filter. When the dust cake is pushed away - for example during jet-pulses – the dust concentration reaches explosion level in relevant numbers of applications. The idea behind AtexDeDust overcomes this situation by changing the regeneration method as well as by dividing the cleaner in sections with controlled dust atmospheres. The innovations were defined before project starts and they were realised in lifetime of AtexDeDust. They are the backbone of the project as well as the features of the new AtexDeDuster:
• To divide the filter house in at least two parts, separating the high volume, low particulate concentration air stream from a secondary compartment, with low volume, high concentrated particulate stream, where the dust is finally deposited
• To employ an improved on textile filter material with best filter characteristics and with allowing precipitation of different size of particulate matter down to nano-scale
• To precipitate low concentrated particulate inside the first compartment into the surface of a filter thereby forming a dust cake
• To dislodge the growing dust cake from small areas of the filter surface continuously or step by step and to transfer it to the secondary compartment
• To monitor the appearance of ignition sources like sparks, glowing spots, hot metal pieces etc. and to exclude transfer of any kind of ignition source into the secondary compartment
The design of the AtexDeDust cleaner is based on a drum filter. Whereas the dust from raw gas stream is separated on surface of the turning drum, thus surface is regenerated by a sucking unit, which finally transfers the collected dust to dust bin. The use of drum filter design - along with the application of filtration material allowing very high filtration rates – result in low pressure loss over the filtration surface for the raw gas stream. Beside control of dust concentrations inside the two general compartments, low pressure loss for the high volume primary volume reduces energy in cleaning procedure.
Scientific, technical and economic objectives in project span a frame for successful implementation, realisation and outcomes of the project. These main objectives are:
In scientific terms:
• Scientific knowledge on the behaviour of particulate on the new textile material surface especially behaviour of ultra-fine particles during filtering and during regeneration
• Mechanisms of agglomeration of ultra-fine particulate on the filter
• Calculation respectively simulation the flow parameters especially the flow pattern of air and defined sized particulate during filtering and during regeneration
• Measurement of the particulate motion and separation in a laboratory model by means of high resolution anemometers and optical particle sizer
• Estimation of the altering of the filter material, in particular precipitation and sucking off of particulate
• Extension to ultra-fine particulate size smaller 100 nm
• Validation of ATEX regulation proof design, especially the prevention of potential explosive particulate concentrations inside the filter house
On the other hand a set of technical request has to be met to establish a continuously working air cleaner with the defined functions. In a first step the process was set-up in laboratory scale followed by industrial scale with 5000 m3/h device. In technical terms this means an enhanced drum design with appropriate filter material, a supervision regime to recognise ignition sources beyond doubt including industrial available sensors, the development of a sucking unit for regeneration of the drum, a dust resistant drum drive unit and a housing for all components, optimised for flow and hindering deposition of dust away from filter.
The most relevant detailed measures shall improve the filtration performance significantly. These are an air permeability of filtration material from 700 to 1100 l/m²s, a pressure loss over filter surface between 150 to 500 Pa; a filtration efficiency for 0.1 micron particles of 80 – 90 % and as most important one - a residual concentration in cleaned air under 1 mg/m3 . This low concentration allows recirculation of cleaned air to the floor. Additionally it allows integration into commercial and/or existing machinery as retrofit kit.
Generally the project’s tasks were organised in 8 Work Packages whereas 3 Work-Packages deal with scientific investigations, 3 Work Packages with technical development, one with the demonstration and one with management tasks.
Work-Packages
WP1
Mechanisms of Precipitation of Nano Particulate into the surface of filter material
WP2
Filter regeneration of a wide partition of the Atex regulation
WP3
Design of compartmented dedusting technology
WP4
Automatic detection of ignition sources
WP5
Filter design
WP6
Failure safe and cost efficient construction
WP7
Demonstration of dedusting process
WP8
Project management
Summarised the planned tasks and the realisation within the project was consistent according to the measures and to the planned capacities and budget. The timetable in particular the reporting was a challenge for the consortium.
Nevertheless with a ready for demonstration unit, already operation inside a production line and an approval by an ATEX regulation Notified Body, the main objectives of the project were met. Detailed results, in particular detailed results related to filter design and filtration performance were provided next.
Project Results:
Summarized, the goal and the objectives of the project have been achieved.
As well as the objectives of the project differ between scientific ones and technological ones the main result do even. Discussing the results, all investigations and decisions were made under the postulation that dust concentration downstream will be below 1mg/m3 – the limit for indoor re-circulation.
The most relevant scientific results are:
Drum with continuously or step by step sucking off regeneration in pleated design
Use of a turning drum was a design option from the beginning of the project along with the regeneration of this drum via sucking of small areas. This method supports the goal to avoid dust concentrations potential hazardous to explode. On the other hand, the development of industrial air cleaners in the last decades to designs with fixed installation of filter or numbers of filter in one unit help to install a large active filtration area. In these designs the pressure loss over the filter material is strongly linked to separation ability of small particulate, e.g. smaller particulate bear more tight filter material and higher pressure loss. To manage large raw gas volumes the active area has to be increased.
Drum design hinders this enlarging of active area. Increasing drum area will result in undesirable increase of unit size.
To resolve this contradictory facts the use of a new high permeable textile filtration material Hycoknit® was foreseen for the filter drum. This woven textile has a smooth but dense structure and additional crinkled threads inside for separation of dust.
Investigations have demonstrated the suitability of Hycoknit® for separation of a couple of dust kind. Dust with mixed particulate can reach very good result and a high performance in pressure drop. Investigation of two types of Hycoknit demonstrates an initial pressure drop of 50 Pa rising to maximum 250 Pa in operation. If the dust contains particulate in submicron size (e.g. soot particulate 0,1 µm) the separation efficiency drops down and downstream concentration will rise to 2-4 mg/m3, what does not match the objectives. However for suitable dust without submicron fraction, the Hycoknit® textile covered drum is an excellent option for high volume rates and low pressure loss.
For dust - containing different sized fraction down to the submicron range - a new approach of a pleated filter has been developed and investigated. Whereas pleated drum is a new design, the sucking-off of the pleats with very good regeneration results is very new. There are several modes to organise the sucking-off, continuously, step by step in sections of the cylindrical shape or controlled by pressure gap over filter surface. In all kind only a partition of the filter is regenerated and the other areas remain in filtration process.
The pleats are directed parallel to the drums turning axe. They are supported by an inner cylindrical cage and are tightly fixed at lower and upper end of drum. Investigation were performed in lab scale for several kind of mixed dust, where the test dust itself was a recommended one and the submicron fraction could be varied and spent by soot generators.
As filter material some polyester materials were investigated, covered with aluminium, PTFE and uncovered. The aluminium covered material provides the best and most stable regeneration performance. For relevant volume rates and dust concentrations the pressure gap over the filter is between 150 – 350 Pa depending of chosen the regeneration cycles. Naturally the regeneration period between two regeneration cycles determines the uploaded filter cake. Deep filter cake generates an additional pressure gap over filtration layer as usual in other filter installations. According to the fact, that regeneration does not disturb the filtration process and can be controlled, an optimum set of filtration and regeneration parameters can be found for specific application cases.
The performance of the pleated drum with aluminium coated material has been investigated for lab probes including particle size distribution and precipitation cut-off. It has been investigated for lab scale drum and for the demonstrator drum. All trials show very good performance with test dust of known particulate size distribution and with real dust in demonstration period.
Calculation and estimation of the pleats design related to filtration performance
The pleats design, e.g. the depth, the number per circumference length, the angle at ground edge can be varied widely. Variation have been investigated systematically for a depth between 7 mm and 35 mm and a distance from upper fold to upper fold between approx. 3mm to approx. 20 mm.
To find out a rule for filtration and regeneration behaviour these samples have been tested in lab scale tester with the parameters face velocity in separation and, sucking velocity in regeneration as well as the linked parameters like volume rates upstream and in sucking unit respectively the pressure situation in main volume stream and in side channel flow.
The measurement and investigations result in a formula to predict suitable and best filtration and regeneration parameters and estimate the characteristics of both processes without trial. It has been incorporated in a calculation sheet for the estimation of design and operation parameters related to application. The calculation sheet allows estimation of the filtration parameters, alerts critical values and recommends the suitable set of design and operation parameter for a not yet realised application. Additionally it calculates the probable dust concentration based on operation loads and supervises the critical hazardous dust levels. Critical dust loads come from GESTIS data-base. New applications as well as the critical dust levels can be added and changed.
Procedure for ultrafine nano-particulate handling in filtration and regeneration
In application cases with mainly and solely small sized NP in the 100 nm range the filtration process by drum filter becomes more challenging. All results in this topic are based on counting of particles related to size; the results do not cover weight measurements. By weight the dust concentration on clean gas side is always under 1 mg/m3 also of the efficiency is in the 40 percentage range.
For the same test design like described above but the application of solely submicron (30 – 200 nm) particle sized dust , the filtration efficiency is with under 40 percentage - far away from objectives. An additional drop down of efficiency can be seen for 180 nm sized particles. After some filtration and regeneration cycles the efficiency increases, but the risk of blocking is high. The increase performance of filtration of ultrafine NP dust a preconditioning of the virgin drum was established with a drastic and significant increase of filtration efficiency to over 99 percentages. The drop down at 180 nm disappears. Regeneration becomes effective, so the blocking of the filter after some cycles disappears accordingly. With pre-coating the pressure loss over the pleated drum can be held under 500 Pa. Filtration and regeneration can be organised parallel, the regeneration cycle should be linked to measured pressure gap.
For the discussion of detailed behaviour from 10 to 200 nm particles we refer to the appropriate deliverable. The investigations were performed on lab scale tester and on lab scale drum. They demonstrate the suitability of the drum design respectively the pleated drum design also for the very specific cases with “pure” ultrafine particulate. Nevertheless for an industrial realisation of these very specific applications further development is essential to guarantee the functionality and suitability for the technical components as well as the tightness (for such small NP) in technical and practical scale. For industrial scale a re-design of the deduster is indicated as well as the more complicated task to measure these ultrafine particulate on the floor.
Considering these scientific results, our consortium has decided to split the application cases according to particle scaling respectively fractions. Whereas the “normal” sized particulate can be cleaned down to 1 µm size and the near submicron range, the separation of ultrafine nano-particulate needs more application knowledge and more application effort, to catch ultrafine nano particles efficiently and safely on industrial scale.
One additional important result is the calculation respectively simulation of the flow pattern inside the deduster. These simulations were realised for the lab scale drum tester. The result links scientific findings of the ambitious simulation, which bears advices for the deduster’s design. The calculation of the flow pattern allows the consideration of velocities and turbulences according to the situation around the drum. On the other hand it allows to detect spaces inside the filter house, where precipitation of dust can take place at false locations. This results in layering of dust inside the filter house, the inlet and outlet and in pre-separator. To detect such locations before realisation can lower the optimisation of design and construction in further realisation.
Comparison of the simulation effects with the problematic zones inside demonstration unit comply. The simulated pattern supports the re-design of some partition of the demonstration unit like the pre-separator and the surface under the drum. Also dimensioning and positioning of the sucking nozzles could be supported by the simulated flow pattern.
The most relevant technical results are:
Supervision and detection of ignition sources
For ATEX safe installation one of the key questions is , how to detect prime sources for ignition or explosion before potential hazardous situations appear. Else if the design of the new deduster lowers the risk, when dust is separated and stored, a residual risk remains for ignition or explosion. Answering the question a monitoring and supervision system was investigated, elaborated and in demonstrator integrated. It is based on different acting sensors for alerts and for control of actors.
The outcome of the activities was a clearly addressed scheme, were to use which sensors and how to include it in design. Depending on application, i.e the properties of the separated dust and relevant concentrations, a deduster needs a supervision in the inlet against sparks, a sensor for monitoring the surface of the filter drum itself and a sensor for the dust bin to monitor potential ignition. In some cases additionally a sensor for electrostatic charges may be required, but for the metal coated pleated drum no charging could be measured. The combination of IR sensors, gas sensors and spark trap in the inlet can detect and avoid risk in the first filter house. However, in case of ignition source on the drum itself (glowing, electrostatic discharge) additional gas sensor and light sensitive sensor will stop the filtration process immediately.
The time schedule for detection, alerting and reaction of the control system has to be designed very carefully according to the fact, that the second filter house – with higher dust concentrations and the dust bin – is much more sensitive against hazard. Therefore all means have been applied to hinder spark or glowing matter entry into this section.
The concept has been realised in the demonstration unit. It has been discussed during approval with the experts from ATEX Notified Body and found to be compliant for the foreseen application case.
Robust drum drive inside raw gas section
The drum drive itself must be installed in the raw gas section where rough conditions for mechanical turning parts are observed. Nevertheless the requests for drum drive are in some aspects contradictory. On one hand side the bearing of the drum should be gas tight to lower abrasion and must support a considerable momentum on the axis, applied by the sucking force on outer surface of drum. On the other side it must be very smooth to move to lower friction and to and to avoid electrostatic charging. The task was solved by a special designed bearing, able to support the drum relatively far away from axis. Contemporarily bearing itself and the turning parts are sealed with large sealing diameter. The drive is realised by a belt construction, where the driving motor is outside the filter section. Transfer is realised by a drive shaft entering the filter section on raw gas side. A belt transfers the force to a ring construction on drum shaft.
At all, the drum drive needs some technical optimisation. With a drum diameter of 700 mm and the sucking nozzles at the outer surface, the turning was disturbed by the resulting momentum and shows some stuttering moves up to drop out of turning. Design of the drum drive belongs to the innovation of the AtexDeDust project.
Sucking-off unit
The sucking-off unit covers all technological knowledge and optimisation of parameters for regeneration in a technical component. Now at the end of the project it appears very simple. The sucking unit covers in the demonstration design (1000 mm length of drum) tree independent nozzles, placed and fixed in one row parallel to axis. Distance to drum as well as the front opening of the nozzles have been optimized to guarantee appropriate velocity of sucking off air, smooth movement along the cylindrical part of filter drum, covering of in minimum two fold edges of the pleats and an surface curvature to minimize friction.
Each nozzle is equipped with an automatic ball valve, which can be opened and closed by the controller and allow a consecutive regeneration of the cylindrical drum outside. Nozzles, controlled valves and dust bin are connected by tubing. The suck-off is driven by a side channel blower, whereas the dust bin outlet is protected by small policy filter.
Set-up of a soft-ware tool for the calculation of the deduster’s dimensioning
Based on excel as license free and wide spread language a complex calculation sheet was developed, described and evaluated by the SME for future design set-up and consultancy of clients. The tool allows estimation of drum filter and operation parameters. It covers the main flow behaviour for main stream and suck-off stream, it calculates the arising dust concentrations in the different compartments and checks these ones against explosion hazard due to GESTIS database.
It provides geometric respectively active area dimensions for the several components of the deduster and supervises the necessary parameters and inputs for complete and safe set-up. In case of critical parameters it recommends changes in dimensioning or operation time cycles. The tool is evaluated by the SME to be very useful for post project technical and market activities of the SME and is part of take-over of knowledge from RTD-performers.
Demonstrator in modular design
It seems difficult to describe the whole functionality of the demonstrator. However, the demonstrator integrates the results of the before run RTD Work Packages. Due to the designed modular concept it can built up based on design and construction methods of the novus product line.
The core of the unit is the drum filter house, equipped with the drum itself, the sucking nozzles and the detection sensors. Main volume raw gas stream is sucked by a fan with integrated policy filter, who is situated on clean gas side. Filtration occurs from the outside of the drum to the inner cylindrical shape. At back side the pre-cleaner is located, equipped with an additional and controlled sucking line to transfer the fallen down dust directly to dust bin.
Over the primary filter house the drivers motor is located as well as the main fan. The secondary filter house is constructed from tubing, which connects sucking nozzles to dust bin, driven by side channel blower. The dust bin is located at the lowest bottom. Equipped with filter bags it allows the removal of separated dust from the unit.
The inlet is organised on top of the tower, the smooth outlet on one side of the tower.
To visualise the unit we refer to the video with the principle functionality.
The unit was tested with the Hycoknit® textile drum as well as with the pleated drum. After some optimisation mainly for a better drum drive and for lower deposition of drum inside the house, it was tested on site and sent to customer for test on floor. There it is in action now.
The application case deals with a very inhomogeneous dust consisting of macroscopic chips, different sized fibres and charcoal down to 1 µm range or submicron fraction. Particles and fibres can be separated very efficiently and safely. The chips have to be separated in pre-cleaner and sucked of from there separately.
A clean gas concentration of lower 1 mg/m3 can be realised up to now. Initial and arising pressure gap over the filter material are very low and stay very low in filter loading and filter regeneration cycles. For these kind and size of particles the filtration parameters, respectively the quality parameters can be reached with a separation rate of more than 99 %. The challenge in the application case is not the separation at all but additionally the separation at the right location. So the macroscopic chips era problems in case they enter the filter house itself. Therefore optimisation of the pre-cleaner was a strong task.
With a volume rate of 5000 m3/h and the very good filtration performance the AtexDeduster meets the demands of the customer as it complies with the objectives of the project. In parallel to test on floor the AtexDeduster was inspected by IBExU, a Notified Body for ATEX regulation items. The approval (in German) is included in attachment. Summarized their expertise approve the new deduster design and compliance with ATEX regulation. They recommend a case by case check in first applications, in particular the check for potential risk concentrations inside suction line.
Potential Impact:
Industrial dedusters are a big market in EU and international. The equipment is worth to workers protection as well as to air pollution and emission regulations. The new deduster matches the trend to small, mobile instrumentation without fixed ductwork installation. It can operate near the dust source.
The modern concept of the deduster allows recirculation of air within production lines. This feature enables companies to fit or retro-fit their machines with the new deduster inside the factory floor. Hereby the ability to recirculate allows saving a lot of heating energy due to the fact that indoor air can stay indoors with same temperature and humidity. We have estimated the energy saving spend by recirculation with approximately 1.3 105 kWh per anno for a 5000 m3/h unit under middle European climate conditions. This is a strong argument for our customer to purchase the new deduster in case of modernisation beside the benefit of ATEX compliance without explosion proof instrumentation.
For a lot of cases this explosion proof instrumentation can be avoided by the new design. The expertise of ATEX Notified Body recommends a case by case calculation of the appearing concentrations to proof the dust conditions.
The implementation to market is planned for the year 2014. Turnover shall arise in the next years to 4 Mio EUR per year.
Prospectively pure and sole Nano-particulate will be separated by AtexDeduster in long term period. For this specific kind of dust we have to improve the technical realisation of elaborated methods and filter design. According to the modular construction of the machine, this will bear main effort for application trials and tests primarily.
European and international expectations for nano particle implementation in technical and technological processes is very ambiguous due to increasing performance and to economic impact. Development and beginning deployment of nano particles is a scientific and international issue at least for the last two decades. In European framework the systematic development of nanotechnology started with the FP4 Program (1994-1998). Nanotechnology and nano-materials belong to one of the ten key thematic issues in the Cooperation part of the 7Framework Program. With 3500 million EURO the Nano production covers middle worth budget amongst the ten. On the other hand pure Nano Particle implementations are countable up to now primarily in laboratories. Strong industrial production of Nano-Particles are seldom up to now.
Summarised the project AtexDeDust and the out-coming scientific and technical results have strengthen our competitiveness and innovation in deduster market. Applying a new patent in the last month of project shall protect the invention and provide benefit to our consortium on market.
To protect our results a patent application was filed in in summer 2013.
Several dissemination activities were performed to support exploitation of results.
There are a couple of publications in workshops, international conferences and peer-reviewed periodica to demonstrate the principle, technology and benefits to the scientific and air cleaning community. Additionally the future product was demonstrated on two international industrial fairs in 2013 to the customer public.
For marketing and advertisement of the AtexDeDuster we refer to the video clip on website.
List of Websites:
public website: www.atexdedust.eu
websites of the AtexDeDust partners:
www.novusair.com
www.bamet.pl
www.envi-filter.dk
www.ilkdresden.de
www.vt.tuwien.ac.at
The generic goal of AtexDeDust project was the scientific investigation and first demonstration of suitability and viability of a new approach of industrial air cleaners. The idea behind the project aims for spatial and time controlled conditions inside the filter house. It excludes the contemporary appearance of potential explosive dust concentrations and ignition sources. An additional objective was the extension to nano-scale particulate separation along with high filtration rates.
The RTD-project AtexDeDust achieves the general objectives to implement the new technology in air cleaning systems. This improvement of technology covers the three key issues for more efficient and safer air cleaners:
• mobile instrumentation gaining clean air quality, that allows re-circulation directly or within machine integrated filter approach
• preventing conditions, which require explosion proof equipment
• extension of particle size range down to nano-scale
These general objectives will be reached by several technical, respectively technological changes in the deduster’s design. The most important ones are the splitting of the deduster house into two sections as well as the use of drum filter. The two compartments of the filter house are aimed at avoiding potential explosion risk. The implementation of the filter drum allows a more controlled regeneration of the filter surface, accompanied by remarkable low pressure loss over the filter. Latter is supported by specialised filter material and drum design. The specialised textile filter material supports very high filtration rates together with efficient separation of particulate sized down to the 1 micrometre scale. For dust separation with mainly nano-scaled fraction a pleated filter drum design was developed, which can be regenerated by sucking accordingly. Design and procedure are detected to be new and have been applied for patent. In lab scale the pleated filter drum along with a sophisticated filtration material show very high separation rates for pure and solely nano-sized particulate lower than 100 nm with filtration rates comparable to normal sized dust.
Beside the focus on filtration efficiency the RTD activities result in a set of technological investigations and procedures to shorten the time to market. These results include soft-ware tools to estimate the separation behaviour for detailed applications and the relevant dust concentrations insides. They include as well finding out technical components, reliable in operation under the rough environment inside the machine.
The project covers a 4-month demonstration of the innovative air cleaning technology on the floor.
Design and construction of this first demonstration unit was approved by Air cleaning Notified Body to be safe and avoids explosion risk.
The consortium set-up a favourable Use and Exploitation Plan and strives for turnover within the first post project year. The new realised deduster design lets expect not only economic benefit for the SME partner but provides beneficial features for clients and environment, saving energy in operation and allowing mobile as well as indoor installations.
Project Context and Objectives:
The AtexDeDust project was implemented to find a new approach for industrial air cleaners with scientific and technical objectives. The project was launched by a consortium of three SME from Germany, Poland and Denmark. According to the “Research for the benefit for SME”- FP7 framework two RTD-performer from Germany and Austria have provided scientific knowledge and cutting edge measurement resources.
Totally the project was split in three periods:
• Set-up of lab testers and investigation of basics of separation and regeneration behaviour of filter
• Elaboration of detailed scientific and technical aspects, able to be realised in industrial scale
• Design, realisation and test of a demonstration unit
The innovations of the project, aimed by an idea to avoid explosion proof installation of the cleaners in most of application cases, were determined by the fact that potential explosion risks appear during cleaning process. On raw gas side of the cleaner the dust concentration normally is so low that explosion levels won’t be reached. Collecting dust respectively dust layers on filter surfaces let grow the hazard for explosion significantly, in particular it let grow this hazard during regeneration of the filter. When the dust cake is pushed away - for example during jet-pulses – the dust concentration reaches explosion level in relevant numbers of applications. The idea behind AtexDeDust overcomes this situation by changing the regeneration method as well as by dividing the cleaner in sections with controlled dust atmospheres. The innovations were defined before project starts and they were realised in lifetime of AtexDeDust. They are the backbone of the project as well as the features of the new AtexDeDuster:
• To divide the filter house in at least two parts, separating the high volume, low particulate concentration air stream from a secondary compartment, with low volume, high concentrated particulate stream, where the dust is finally deposited
• To employ an improved on textile filter material with best filter characteristics and with allowing precipitation of different size of particulate matter down to nano-scale
• To precipitate low concentrated particulate inside the first compartment into the surface of a filter thereby forming a dust cake
• To dislodge the growing dust cake from small areas of the filter surface continuously or step by step and to transfer it to the secondary compartment
• To monitor the appearance of ignition sources like sparks, glowing spots, hot metal pieces etc. and to exclude transfer of any kind of ignition source into the secondary compartment
The design of the AtexDeDust cleaner is based on a drum filter. Whereas the dust from raw gas stream is separated on surface of the turning drum, thus surface is regenerated by a sucking unit, which finally transfers the collected dust to dust bin. The use of drum filter design - along with the application of filtration material allowing very high filtration rates – result in low pressure loss over the filtration surface for the raw gas stream. Beside control of dust concentrations inside the two general compartments, low pressure loss for the high volume primary volume reduces energy in cleaning procedure.
Scientific, technical and economic objectives in project span a frame for successful implementation, realisation and outcomes of the project. These main objectives are:
In scientific terms:
• Scientific knowledge on the behaviour of particulate on the new textile material surface especially behaviour of ultra-fine particles during filtering and during regeneration
• Mechanisms of agglomeration of ultra-fine particulate on the filter
• Calculation respectively simulation the flow parameters especially the flow pattern of air and defined sized particulate during filtering and during regeneration
• Measurement of the particulate motion and separation in a laboratory model by means of high resolution anemometers and optical particle sizer
• Estimation of the altering of the filter material, in particular precipitation and sucking off of particulate
• Extension to ultra-fine particulate size smaller 100 nm
• Validation of ATEX regulation proof design, especially the prevention of potential explosive particulate concentrations inside the filter house
On the other hand a set of technical request has to be met to establish a continuously working air cleaner with the defined functions. In a first step the process was set-up in laboratory scale followed by industrial scale with 5000 m3/h device. In technical terms this means an enhanced drum design with appropriate filter material, a supervision regime to recognise ignition sources beyond doubt including industrial available sensors, the development of a sucking unit for regeneration of the drum, a dust resistant drum drive unit and a housing for all components, optimised for flow and hindering deposition of dust away from filter.
The most relevant detailed measures shall improve the filtration performance significantly. These are an air permeability of filtration material from 700 to 1100 l/m²s, a pressure loss over filter surface between 150 to 500 Pa; a filtration efficiency for 0.1 micron particles of 80 – 90 % and as most important one - a residual concentration in cleaned air under 1 mg/m3 . This low concentration allows recirculation of cleaned air to the floor. Additionally it allows integration into commercial and/or existing machinery as retrofit kit.
Generally the project’s tasks were organised in 8 Work Packages whereas 3 Work-Packages deal with scientific investigations, 3 Work Packages with technical development, one with the demonstration and one with management tasks.
Work-Packages
WP1
Mechanisms of Precipitation of Nano Particulate into the surface of filter material
WP2
Filter regeneration of a wide partition of the Atex regulation
WP3
Design of compartmented dedusting technology
WP4
Automatic detection of ignition sources
WP5
Filter design
WP6
Failure safe and cost efficient construction
WP7
Demonstration of dedusting process
WP8
Project management
Summarised the planned tasks and the realisation within the project was consistent according to the measures and to the planned capacities and budget. The timetable in particular the reporting was a challenge for the consortium.
Nevertheless with a ready for demonstration unit, already operation inside a production line and an approval by an ATEX regulation Notified Body, the main objectives of the project were met. Detailed results, in particular detailed results related to filter design and filtration performance were provided next.
Project Results:
Summarized, the goal and the objectives of the project have been achieved.
As well as the objectives of the project differ between scientific ones and technological ones the main result do even. Discussing the results, all investigations and decisions were made under the postulation that dust concentration downstream will be below 1mg/m3 – the limit for indoor re-circulation.
The most relevant scientific results are:
Drum with continuously or step by step sucking off regeneration in pleated design
Use of a turning drum was a design option from the beginning of the project along with the regeneration of this drum via sucking of small areas. This method supports the goal to avoid dust concentrations potential hazardous to explode. On the other hand, the development of industrial air cleaners in the last decades to designs with fixed installation of filter or numbers of filter in one unit help to install a large active filtration area. In these designs the pressure loss over the filter material is strongly linked to separation ability of small particulate, e.g. smaller particulate bear more tight filter material and higher pressure loss. To manage large raw gas volumes the active area has to be increased.
Drum design hinders this enlarging of active area. Increasing drum area will result in undesirable increase of unit size.
To resolve this contradictory facts the use of a new high permeable textile filtration material Hycoknit® was foreseen for the filter drum. This woven textile has a smooth but dense structure and additional crinkled threads inside for separation of dust.
Investigations have demonstrated the suitability of Hycoknit® for separation of a couple of dust kind. Dust with mixed particulate can reach very good result and a high performance in pressure drop. Investigation of two types of Hycoknit demonstrates an initial pressure drop of 50 Pa rising to maximum 250 Pa in operation. If the dust contains particulate in submicron size (e.g. soot particulate 0,1 µm) the separation efficiency drops down and downstream concentration will rise to 2-4 mg/m3, what does not match the objectives. However for suitable dust without submicron fraction, the Hycoknit® textile covered drum is an excellent option for high volume rates and low pressure loss.
For dust - containing different sized fraction down to the submicron range - a new approach of a pleated filter has been developed and investigated. Whereas pleated drum is a new design, the sucking-off of the pleats with very good regeneration results is very new. There are several modes to organise the sucking-off, continuously, step by step in sections of the cylindrical shape or controlled by pressure gap over filter surface. In all kind only a partition of the filter is regenerated and the other areas remain in filtration process.
The pleats are directed parallel to the drums turning axe. They are supported by an inner cylindrical cage and are tightly fixed at lower and upper end of drum. Investigation were performed in lab scale for several kind of mixed dust, where the test dust itself was a recommended one and the submicron fraction could be varied and spent by soot generators.
As filter material some polyester materials were investigated, covered with aluminium, PTFE and uncovered. The aluminium covered material provides the best and most stable regeneration performance. For relevant volume rates and dust concentrations the pressure gap over the filter is between 150 – 350 Pa depending of chosen the regeneration cycles. Naturally the regeneration period between two regeneration cycles determines the uploaded filter cake. Deep filter cake generates an additional pressure gap over filtration layer as usual in other filter installations. According to the fact, that regeneration does not disturb the filtration process and can be controlled, an optimum set of filtration and regeneration parameters can be found for specific application cases.
The performance of the pleated drum with aluminium coated material has been investigated for lab probes including particle size distribution and precipitation cut-off. It has been investigated for lab scale drum and for the demonstrator drum. All trials show very good performance with test dust of known particulate size distribution and with real dust in demonstration period.
Calculation and estimation of the pleats design related to filtration performance
The pleats design, e.g. the depth, the number per circumference length, the angle at ground edge can be varied widely. Variation have been investigated systematically for a depth between 7 mm and 35 mm and a distance from upper fold to upper fold between approx. 3mm to approx. 20 mm.
To find out a rule for filtration and regeneration behaviour these samples have been tested in lab scale tester with the parameters face velocity in separation and, sucking velocity in regeneration as well as the linked parameters like volume rates upstream and in sucking unit respectively the pressure situation in main volume stream and in side channel flow.
The measurement and investigations result in a formula to predict suitable and best filtration and regeneration parameters and estimate the characteristics of both processes without trial. It has been incorporated in a calculation sheet for the estimation of design and operation parameters related to application. The calculation sheet allows estimation of the filtration parameters, alerts critical values and recommends the suitable set of design and operation parameter for a not yet realised application. Additionally it calculates the probable dust concentration based on operation loads and supervises the critical hazardous dust levels. Critical dust loads come from GESTIS data-base. New applications as well as the critical dust levels can be added and changed.
Procedure for ultrafine nano-particulate handling in filtration and regeneration
In application cases with mainly and solely small sized NP in the 100 nm range the filtration process by drum filter becomes more challenging. All results in this topic are based on counting of particles related to size; the results do not cover weight measurements. By weight the dust concentration on clean gas side is always under 1 mg/m3 also of the efficiency is in the 40 percentage range.
For the same test design like described above but the application of solely submicron (30 – 200 nm) particle sized dust , the filtration efficiency is with under 40 percentage - far away from objectives. An additional drop down of efficiency can be seen for 180 nm sized particles. After some filtration and regeneration cycles the efficiency increases, but the risk of blocking is high. The increase performance of filtration of ultrafine NP dust a preconditioning of the virgin drum was established with a drastic and significant increase of filtration efficiency to over 99 percentages. The drop down at 180 nm disappears. Regeneration becomes effective, so the blocking of the filter after some cycles disappears accordingly. With pre-coating the pressure loss over the pleated drum can be held under 500 Pa. Filtration and regeneration can be organised parallel, the regeneration cycle should be linked to measured pressure gap.
For the discussion of detailed behaviour from 10 to 200 nm particles we refer to the appropriate deliverable. The investigations were performed on lab scale tester and on lab scale drum. They demonstrate the suitability of the drum design respectively the pleated drum design also for the very specific cases with “pure” ultrafine particulate. Nevertheless for an industrial realisation of these very specific applications further development is essential to guarantee the functionality and suitability for the technical components as well as the tightness (for such small NP) in technical and practical scale. For industrial scale a re-design of the deduster is indicated as well as the more complicated task to measure these ultrafine particulate on the floor.
Considering these scientific results, our consortium has decided to split the application cases according to particle scaling respectively fractions. Whereas the “normal” sized particulate can be cleaned down to 1 µm size and the near submicron range, the separation of ultrafine nano-particulate needs more application knowledge and more application effort, to catch ultrafine nano particles efficiently and safely on industrial scale.
One additional important result is the calculation respectively simulation of the flow pattern inside the deduster. These simulations were realised for the lab scale drum tester. The result links scientific findings of the ambitious simulation, which bears advices for the deduster’s design. The calculation of the flow pattern allows the consideration of velocities and turbulences according to the situation around the drum. On the other hand it allows to detect spaces inside the filter house, where precipitation of dust can take place at false locations. This results in layering of dust inside the filter house, the inlet and outlet and in pre-separator. To detect such locations before realisation can lower the optimisation of design and construction in further realisation.
Comparison of the simulation effects with the problematic zones inside demonstration unit comply. The simulated pattern supports the re-design of some partition of the demonstration unit like the pre-separator and the surface under the drum. Also dimensioning and positioning of the sucking nozzles could be supported by the simulated flow pattern.
The most relevant technical results are:
Supervision and detection of ignition sources
For ATEX safe installation one of the key questions is , how to detect prime sources for ignition or explosion before potential hazardous situations appear. Else if the design of the new deduster lowers the risk, when dust is separated and stored, a residual risk remains for ignition or explosion. Answering the question a monitoring and supervision system was investigated, elaborated and in demonstrator integrated. It is based on different acting sensors for alerts and for control of actors.
The outcome of the activities was a clearly addressed scheme, were to use which sensors and how to include it in design. Depending on application, i.e the properties of the separated dust and relevant concentrations, a deduster needs a supervision in the inlet against sparks, a sensor for monitoring the surface of the filter drum itself and a sensor for the dust bin to monitor potential ignition. In some cases additionally a sensor for electrostatic charges may be required, but for the metal coated pleated drum no charging could be measured. The combination of IR sensors, gas sensors and spark trap in the inlet can detect and avoid risk in the first filter house. However, in case of ignition source on the drum itself (glowing, electrostatic discharge) additional gas sensor and light sensitive sensor will stop the filtration process immediately.
The time schedule for detection, alerting and reaction of the control system has to be designed very carefully according to the fact, that the second filter house – with higher dust concentrations and the dust bin – is much more sensitive against hazard. Therefore all means have been applied to hinder spark or glowing matter entry into this section.
The concept has been realised in the demonstration unit. It has been discussed during approval with the experts from ATEX Notified Body and found to be compliant for the foreseen application case.
Robust drum drive inside raw gas section
The drum drive itself must be installed in the raw gas section where rough conditions for mechanical turning parts are observed. Nevertheless the requests for drum drive are in some aspects contradictory. On one hand side the bearing of the drum should be gas tight to lower abrasion and must support a considerable momentum on the axis, applied by the sucking force on outer surface of drum. On the other side it must be very smooth to move to lower friction and to and to avoid electrostatic charging. The task was solved by a special designed bearing, able to support the drum relatively far away from axis. Contemporarily bearing itself and the turning parts are sealed with large sealing diameter. The drive is realised by a belt construction, where the driving motor is outside the filter section. Transfer is realised by a drive shaft entering the filter section on raw gas side. A belt transfers the force to a ring construction on drum shaft.
At all, the drum drive needs some technical optimisation. With a drum diameter of 700 mm and the sucking nozzles at the outer surface, the turning was disturbed by the resulting momentum and shows some stuttering moves up to drop out of turning. Design of the drum drive belongs to the innovation of the AtexDeDust project.
Sucking-off unit
The sucking-off unit covers all technological knowledge and optimisation of parameters for regeneration in a technical component. Now at the end of the project it appears very simple. The sucking unit covers in the demonstration design (1000 mm length of drum) tree independent nozzles, placed and fixed in one row parallel to axis. Distance to drum as well as the front opening of the nozzles have been optimized to guarantee appropriate velocity of sucking off air, smooth movement along the cylindrical part of filter drum, covering of in minimum two fold edges of the pleats and an surface curvature to minimize friction.
Each nozzle is equipped with an automatic ball valve, which can be opened and closed by the controller and allow a consecutive regeneration of the cylindrical drum outside. Nozzles, controlled valves and dust bin are connected by tubing. The suck-off is driven by a side channel blower, whereas the dust bin outlet is protected by small policy filter.
Set-up of a soft-ware tool for the calculation of the deduster’s dimensioning
Based on excel as license free and wide spread language a complex calculation sheet was developed, described and evaluated by the SME for future design set-up and consultancy of clients. The tool allows estimation of drum filter and operation parameters. It covers the main flow behaviour for main stream and suck-off stream, it calculates the arising dust concentrations in the different compartments and checks these ones against explosion hazard due to GESTIS database.
It provides geometric respectively active area dimensions for the several components of the deduster and supervises the necessary parameters and inputs for complete and safe set-up. In case of critical parameters it recommends changes in dimensioning or operation time cycles. The tool is evaluated by the SME to be very useful for post project technical and market activities of the SME and is part of take-over of knowledge from RTD-performers.
Demonstrator in modular design
It seems difficult to describe the whole functionality of the demonstrator. However, the demonstrator integrates the results of the before run RTD Work Packages. Due to the designed modular concept it can built up based on design and construction methods of the novus product line.
The core of the unit is the drum filter house, equipped with the drum itself, the sucking nozzles and the detection sensors. Main volume raw gas stream is sucked by a fan with integrated policy filter, who is situated on clean gas side. Filtration occurs from the outside of the drum to the inner cylindrical shape. At back side the pre-cleaner is located, equipped with an additional and controlled sucking line to transfer the fallen down dust directly to dust bin.
Over the primary filter house the drivers motor is located as well as the main fan. The secondary filter house is constructed from tubing, which connects sucking nozzles to dust bin, driven by side channel blower. The dust bin is located at the lowest bottom. Equipped with filter bags it allows the removal of separated dust from the unit.
The inlet is organised on top of the tower, the smooth outlet on one side of the tower.
To visualise the unit we refer to the video with the principle functionality.
The unit was tested with the Hycoknit® textile drum as well as with the pleated drum. After some optimisation mainly for a better drum drive and for lower deposition of drum inside the house, it was tested on site and sent to customer for test on floor. There it is in action now.
The application case deals with a very inhomogeneous dust consisting of macroscopic chips, different sized fibres and charcoal down to 1 µm range or submicron fraction. Particles and fibres can be separated very efficiently and safely. The chips have to be separated in pre-cleaner and sucked of from there separately.
A clean gas concentration of lower 1 mg/m3 can be realised up to now. Initial and arising pressure gap over the filter material are very low and stay very low in filter loading and filter regeneration cycles. For these kind and size of particles the filtration parameters, respectively the quality parameters can be reached with a separation rate of more than 99 %. The challenge in the application case is not the separation at all but additionally the separation at the right location. So the macroscopic chips era problems in case they enter the filter house itself. Therefore optimisation of the pre-cleaner was a strong task.
With a volume rate of 5000 m3/h and the very good filtration performance the AtexDeduster meets the demands of the customer as it complies with the objectives of the project. In parallel to test on floor the AtexDeduster was inspected by IBExU, a Notified Body for ATEX regulation items. The approval (in German) is included in attachment. Summarized their expertise approve the new deduster design and compliance with ATEX regulation. They recommend a case by case check in first applications, in particular the check for potential risk concentrations inside suction line.
Potential Impact:
Industrial dedusters are a big market in EU and international. The equipment is worth to workers protection as well as to air pollution and emission regulations. The new deduster matches the trend to small, mobile instrumentation without fixed ductwork installation. It can operate near the dust source.
The modern concept of the deduster allows recirculation of air within production lines. This feature enables companies to fit or retro-fit their machines with the new deduster inside the factory floor. Hereby the ability to recirculate allows saving a lot of heating energy due to the fact that indoor air can stay indoors with same temperature and humidity. We have estimated the energy saving spend by recirculation with approximately 1.3 105 kWh per anno for a 5000 m3/h unit under middle European climate conditions. This is a strong argument for our customer to purchase the new deduster in case of modernisation beside the benefit of ATEX compliance without explosion proof instrumentation.
For a lot of cases this explosion proof instrumentation can be avoided by the new design. The expertise of ATEX Notified Body recommends a case by case calculation of the appearing concentrations to proof the dust conditions.
The implementation to market is planned for the year 2014. Turnover shall arise in the next years to 4 Mio EUR per year.
Prospectively pure and sole Nano-particulate will be separated by AtexDeduster in long term period. For this specific kind of dust we have to improve the technical realisation of elaborated methods and filter design. According to the modular construction of the machine, this will bear main effort for application trials and tests primarily.
European and international expectations for nano particle implementation in technical and technological processes is very ambiguous due to increasing performance and to economic impact. Development and beginning deployment of nano particles is a scientific and international issue at least for the last two decades. In European framework the systematic development of nanotechnology started with the FP4 Program (1994-1998). Nanotechnology and nano-materials belong to one of the ten key thematic issues in the Cooperation part of the 7Framework Program. With 3500 million EURO the Nano production covers middle worth budget amongst the ten. On the other hand pure Nano Particle implementations are countable up to now primarily in laboratories. Strong industrial production of Nano-Particles are seldom up to now.
Summarised the project AtexDeDust and the out-coming scientific and technical results have strengthen our competitiveness and innovation in deduster market. Applying a new patent in the last month of project shall protect the invention and provide benefit to our consortium on market.
To protect our results a patent application was filed in in summer 2013.
Several dissemination activities were performed to support exploitation of results.
There are a couple of publications in workshops, international conferences and peer-reviewed periodica to demonstrate the principle, technology and benefits to the scientific and air cleaning community. Additionally the future product was demonstrated on two international industrial fairs in 2013 to the customer public.
For marketing and advertisement of the AtexDeDuster we refer to the video clip on website.
List of Websites:
public website: www.atexdedust.eu
websites of the AtexDeDust partners:
www.novusair.com
www.bamet.pl
www.envi-filter.dk
www.ilkdresden.de
www.vt.tuwien.ac.at