REPRINT ZKG PROCESS PROCESS

Transcription

1 4 Planning detail for integration of the into the existing plant peripherals a rotary feeder, the otor for 180 t/h of raw eal, for exaple, has a rating of 5.5 and during operation it uses less than Grain destruction The high copression of the bulk aterial due to the relative oveent of the screw pup leads to destruction of the grains, which, depending on the industry (e.g. the aluina industry), shall be avoided. Kreisel s cause no appreciable grain destruction. veying air will increase. This leads to an increase in velocity. The pressure before the nozzle falls significantly but the pressure after the nozzle falls only slightly. Operation of screw pups at reduced load is therefore very unfavourable fro the energy point of view. 4.7 Wear reduction by reducing the speed The wear on the depends on factors such as hardness and shape of the bulk aterial, the pressure difference across the feeder and the rotational speed of the feeder. The wear can be reduced by adjusting the rotary speed to suit the respective conveying bulk aterial ass flow. This is not possible with screw pups. The high rotational speed of the screw shaft is required to fulfil the sealing function. 5 Screw pup 4.8 Influence of the back pressure on the pup otor The size of otor for the screw pup is alost linearly dependent on the back pressure in the conveying line. Even at average conveying capacities this results in otor sizes of 30 to 250. On the other hand the otor for the rotary feeder is deterined only by the size of the rotary feeder. In 4.10 Motor control centre (MCC) Thanks to the sall drive otor for the rotary feeder and the saller pressure generator otor the MCC can be also ade considerably saller and therefore less expensive. These costs can aount to tens of thousands of euros Coissioning As already entioned in Sections 4.2 and 4.3, the screw pup reacts to various syste paraeters. Multiple odifications are necessary to achieve the correct screw pup configuration during the coissioning while taking the points in 4.2 and 4.3 into account. Screw pitch, plug length, nozzle diaeter and return flap adjustent ust be deterined in tie-consuing conversion processes. The rotary feeder, however, does not respond to these paraeters. A rotary feeder can usually be brought into operation in one to two days Space requireent The low space requireents of the ZSVH can be entioned as the final advantage. As can be seen fro Figure 2 and Figure 7, the ZSV-H can be adapted to suit virtually all local conditions. A rotary feeder can be installed anywhere where there is space for a screw pup with its pup surge bin. At PPC Hercules, for exaple, the screw pup is 4500 long while the Kreisel ceraic rotary feeder requires only 2150 including otor Leakage air Because of the prevailing pressure differences the leakage air flow in rotary feeders is directed against the flow of bulk aterial. This lies between 5% and 12% of the total quantity of conveying air. It is discharged via the dust collector. At PPC the leakage air accounts for 6.4 % of the total copressor power while the energy loss caused by the screw pup nozzle is 15.5 % Capacity of the Cerafeed ZSV-H Depending on the length of the rotary feeder the conveying capacity of the ZSV-H is between 0.3 and 250 3/h. Conveying line pressures of up to 2.0 bar can be applied, depending on the bulk aterial. 5 Energy balance using the exaple of PPC Hercules PPC operates various pneuatic conveying systes at the Hercules plant. Two of the are used to transport ceent fro the grinding plant to the receiving silos. The ceent was fed into the conveying lines by screw pups. Repeated probles, loss of capacity and high energy consuption gave PPC reason to bring about soe technical changes. PPC settled for the latest state of the art s fro Kreisel Gerany. Table 1 shows the syste paraeters of the pneuatic conveying plant with a screw pup as the feed coponent. The data records show a axiu stable conveying capacity of t/h, depending on the type of ceent. In addition to the inadequate conveying capacity there were screw pup failures for various reasons. The operation was disrupted by overfilling and otor failures. In Septeber 2015 the standby conveying screw pup was replaced by a Kreisel ZSV-H, size 700. It was coissioned within two days. A stable conveying capacity of 140 t/h was obtained during the coissioning. The plant capacity was increased to 175 t/h by optiizing the grinding and filter processes and it was found that the Kreisel ZSV-H had not yet reached its liits. So far the plant has been in continuous operation for four onths. Table 1 Plant data of the pneuatic conveying of ceent at PPC Hercules Plant data Bulk solid Blaine Bulk density Raw density Max. conveying distance Conveying altitude Conveying line diaeter Screw pup size Rotary feeder size Motor (installed) Bulk solid teperature Plant altitude Max. stable conveying capacity ²/g DN C t/h Screw pup Ceent /130 Ceraic rotary feeder Ceent > 175 Figure 2 shows the plant layout after conversion to the Kreisel ZSV-H. The inlet was adapted to allow continued use of the support structure for the supporting the screw pup This resulted in very short conversion ties. The driving power of the rotary feeder is easured continuously by the custoer. Due to the special bearings the rotary feeder operates at a power of less than 1. Replaceent of the screw pup by a ceraic rotary feeder has saved a significant proportion of the energy costs of pneuatic conveying. As a result, the return on investent is less than one year. 6 Suary By replacing the screw pup with a Kreisel ceraic rotary valve PPC was able to increase its ceent transport capacity to at least 175 t/h. Other advantages are a stable, reliable pneuatic conveying syste with a very low energy consuption. An annual aount of energy saving of approxiately has been achieved. This is one of ore than two dozen successful projects involving a Kreisel. Meanwhile, PPC has ordered ore ZSV-Hs to replace screw pups in South Africa. Kreisel and PPC are jointly investigating the behaviour and lifetie of the rotary valve. Table 2 Energy dates Data Operation tie Energy cost Shaft power requireent of the feeder Shaft power requireent of the copressors Su energy deand Total energy consuption Energy costs Energy savings Energy costs savings per year Retourn of invest h/a /h h/a /a % year Screw pup size 300 Rotary valve size 700 x < 3/4 This article reports on the advantages of the ZSV-H Kreisel over screw pups and on the successful coissioning of a ZSV-H for PPC Hercules in South Africa. TEXT JD Visser1, Process Engineer, Nyiko Mayiele1, Plant Engineer, Mario Dikty2, Branch Manager 1 PPC Ceent, Hercules/South Africa 2 Kreisel GbH & Co. KG, Krauschwitz/Gerany

2 3 Coissioning of the Kreisel Kreisel invited the plant engineers fro PPC to Gerany in Deceber 2014 to present the Kreisel. After detailed design discussions PPC decided to replace the screw pup by the Kreisel. The rotary feeder was installed after a delivery tie of 5 onths. Kreisel engineered the integration of the Kreisel ZSV-H (Figure 3) into the existing plant configuration (Figure 4). It was possible to use the existing support structures of the screw pup for the assebly. The existing screw pup was disantled and the Kreisel ZSV-H was installed within a very short tie frae. The project anageent was carried out so that the air lines of the pressure generators, the ceent feed and the conveying pipeline could be optially integrated into the technical process. The erection and coissioning were supervised by Kreisel. The installation was followed by the coissioning in which the half-day cold coissioning was followed by the hot coissioning. The grinding plant was started at 100 t/h. After a short tie the plant capacity was increased to 110 t/h and this capacity was kept constant overnight. Over the next two days of operation the ill output was adjusted to the expected conveying capacity of the of 150 t/h. The conveying line back pressure settled to about 1.1 bar. The increase in ill output during the coissioning resulted in the evaluation that the ZSV-H could feed at least 180 t/h of ceent into the existing conveying pipeline. Kreisel achieved the axiu degree of filling by further developent of the inlet geoetry of the leakage air collector to iprove the flow. The leakage air is carefully separated to achieve the optiu constant capacity. KREISEL GMBH & CO. KG Successful coissioning of a at PPC Hercules 1 Introduction The transport of fine bulk solids, such as ceent, raw eal, fly ash or coal, usually takes place pneuatically over coplicated conveying line routes. This eans that the bulk aterial is transported by conveying air through a pipeline syste. The friction that occurs between the bulk aterial and the pipeline wall and the vertical lift in the bulk aterial conveying lines causes a loss of pressure in the conveying air. Consequently, the conveying air for the product transport ust be ade available at a plant-specific pressure. The bulk aterial has to be fed into the air flow of the conveying line against this plant pressure. Different feed systes can be used for this purpose. Coplicated pressure vessel systes or screw pups were used in the past. For over half a decade these systes have been replaced by highly wear-resistant ZSV-H ceraic rotary feeders produced by Kreisel GbH & Co. KG, Gerany. The ost iportant criterion for the use of the Kreisel is the energy saving during plant operation and the considerable wear resistance of the coponents. PPC in South Africa chose a Kreisel ZSV-H 700 for their work in Hercules as the replaceent for a screw pup to ake a power consuption saving of 130 for driving the screw pup. 2 Plant description Figure 1 is a flow chart for a ceent grinding plant. The Hercules PPC factory operates a vertical roller ill for grinding the ceent. The ceent is collected in the downstrea baghouse. An output rotary feeder is placed under each of the two hoppers as well as a shut off valve below the baghouse. It doses the ceent into an airslide that transports the aterial to the DV22 distributor. The airslide diverter feeds the two feeding syste shown in Figure 2 for pneuatic conveying:» the Kreisel (Figure 2, on the right)» the standby screw pup (Figure 2, on the left) The Duo-Cell silo and the packing plant are fed by the pneuatic conveying syste. The Kreisel ZSV-H has been installed so that it can load all three receiving points. The pneuatic transport covers approxiately with a vertical conveying height of 53. The conveying capacity is 150 t/h. The existing pressure generators can also be used by the ZSV-H operation. The ceraic rotary feeder and its feed hopper were fitted into the existing plant so that no odifications on the steel structure or the conveying line were necessary. All Kreisel 1 Flow diagra of the pneuatic conveying plant 4 Coparison of the Kreisel with a screw pup With the Kreisel ZSV-H, Kreisel GbH & Co.KG has a feeder that eets current custoer deands for high precision. After decades of developent and optiization the rotary feeders fro Kreisel are known across all industries for their high quality of anufacture and their reliability. The ceraic lining of the product contact surfaces allows this traditional product to be used as a feeder in pneuatic conveying systes with abrasive aterials. For a long tie the wear caused by flow had been the reason why the rotary feeders were not used as feeders for abrasive aterials. The use of the latest ceraic eleents eans that the necessary requireents for the feeders are now far exceeded. The Kreisel ZSV-H can not only contribute its outstanding properties to the pneuatic conveying The functioning of a screw pup is explained briefly with the aid of the scheatic diagra (Figure 5) so that the Kreisel ZSV-H can be copared with a screw pup. The bulk aterial falls through the inlet (1) in the pup surge bin (2). This is used to draw off the sealing air and the air displaced fro the bulk aterial. The bulk aterial is picked up and transported to the outlet by the high speed copression screw (1000 rp). The bulk aterial is heavily copressed. This copression is assisted by a check flap (4). The copression produces a high-density plug of bulk aterial that provides a seal against the pressure in the conveying pipeline. The solid bulk plug then drops into the outlet of the screw pup where it is picked up by the conveying air and transported into the conveying pipeline. The conveying air has to pass through a nozzle or, depending on the design, several nozzles in the outlet housing. This nozzle produces a pressure drop of about 0.30 bar and serves to accelerate the conveying air and the bulk aterial. The differences between Kreisel Ceraic feeders and screw pup are as follows. systes but is also better than the established input systes with regard to service life, aintenance and spare parts requireents. The arguent that was often cited in the past for a high energy loss because of the escaping leakage air in the feed area has been countered by the use of side plates at the rotor and by the precision of the very sall gaps. Solid construction and grinding of the ceraic eleents guarantee the sall gaps and define predictable quantities of leakage air. These copare favourably with the energy loss of the nozzles used in other systes. Now that the Kreisel ZSV-H had et the custoer requireents for reliability and energy efficiency it was still necessary to verify the integration. Here again the Kreisel s can reveal their potential thorough their sall space requireent and low weight, and have no proble with satisfying the safety officers. Regulated space conditions and the static liits of the existing steel structure for loads and vibration severely liited the plant anufacturer s roo for anoeuvre. This is why it is only with the rotary feeder that the custoer s chosen transfer points could be ipleented. 2 Stand-by pup (on the left) and new Kreisel rotary feeder (on the right) after odification 4.1 Foreign bodies If foreign bodies, such as the reains of grinding balls, are introduced accidentally with the bulk aterial then they ust pass through the feeder. Using the exaple at the PPC the screw pup has a peripheral speed of > 15 /s, whereas the rotary feeder works with < 0.70 /s. In screw pups this can lead to breakage of the wear bushes or the end flight of the screw. In the rotary feeder it is unlikely that these foreign bodies will eet the rotor in such a position that they cause jaing, and even jaing does not norally daage the rotary feeder. 4.2 Properties of the bulk aterial The properties of the bulk aterial, such as fineness (Blaine), grain size distribution, bulk density and oisture, are necessary for diensioning a screw pup. In addition to the back pressure in the conveying pipeline these paraeters affect the diensioning of the drive otor. If these properties are changed by fluctuating processing conditions, this can lead to failure of the screw pup. The results are loss of capacity, otor overloading and sealing probles. Bulk aterial that is too fine or too coarse can only be fed at low pressures (<0.5 bar) because the plug foration is inadequate. For the design of the rotary feeder, however, only the density of the bulk aterial is crucial. The drive is deterined exclusively by the diensioning of the rotary feeder. A 5.5 otor is installed for the rotary feeder at the PPC plant. This draws a power of less than 1 during operation. 4.3 Grinding aid Grinding aids are used to reduce the energy input during grinding. However, these greatly change the conveying and fluidizing behaviour of bulk aterials because they affect the interolecular forces. The experience of recent years has shown that grinding aids can also have a strong influence on the copression behaviour of the bulk aterials. This reduced the capacity of the screw pups by 30 %. In this connection the 132 otor that was installed proved to be under-diensioned. The rotary feeder does not generate any copression of the bulk aterial for sealing purposes so the grinding aid has no negative effect on the conveying and drive capacity of the rotary feeder. 4.4 Overloading of the inlet area If the aterial dosing to the screw pup is irregular and the screw pup is operated close to the capacity liit, then overloading of the inlet area reduces the capacity. If the pup surge bin fills with bulk aterial then the copressed air fro the plug can no longer be discharged at the inlet. The air is transported through the syste by the plug. The plug becoes unstable and can no longer for a seal against the existing conveying line pressure. This causes a reduction in capacity. The design of the inlet to the rotary feeder separates the dust reoval area fro the inlet area. Overfilling of the inlet therefore leads priarily to an increase in capacity rather than a reduction. 4.5 Wear during operation at reduced load If the ass flow of bulk aterial to the screw pup is too low then the requisite sealing plug cannot for properly. The plug breaks down and the conveying air flows into the inlet area at high speed. This acts on the screw like a sand blast nozzle while in the ceraic-lined rotary feeder this does not have a negative effect. There would also be the option of reducing the wear by lowering the rotational speed. 3 3D ounting planning detail for integration of the ceraic rotary feeder into the existing plant configuration 4.6 Energy consuption during operation at reduced load When the rotary feeder is the input device then, if the ass flow drops, the requisite conveying line pressure also drops. If the back pressure in the conveying line drops then the otor current consuption of the pressure generator will drop too. However, this situation with screw pup conveying is different. In this case the influencing coponent is the nozzle (Figure 6, ite 9) in the outlet housing. As with any nozzle the pressure loss increases with increasing flow rate. If the delivery line pressure in the screw pup conveying syste drops then the operating volue of the con-

3 3 Coissioning of the Kreisel Kreisel invited the plant engineers fro PPC to Gerany in Deceber 2014 to present the Kreisel. After detailed design discussions PPC decided to replace the screw pup by the Kreisel. The rotary feeder was installed after a delivery tie of 5 onths. Kreisel engineered the integration of the Kreisel ZSV-H (Figure 3) into the existing plant configuration (Figure 4). It was possible to use the existing support structures of the screw pup for the assebly. The existing screw pup was disantled and the Kreisel ZSV-H was installed within a very short tie frae. The project anageent was carried out so that the air lines of the pressure generators, the ceent feed and the conveying pipeline could be optially integrated into the technical process. The erection and coissioning were supervised by Kreisel. The installation was followed by the coissioning in which the half-day cold coissioning was followed by the hot coissioning. The grinding plant was started at 100 t/h. After a short tie the plant capacity was increased to 110 t/h and this capacity was kept constant overnight. Over the next two days of operation the ill output was adjusted to the expected conveying capacity of the of 150 t/h. The conveying line back pressure settled to about 1.1 bar. The increase in ill output during the coissioning resulted in the evaluation that the ZSV-H could feed at least 180 t/h of ceent into the existing conveying pipeline. Kreisel achieved the axiu degree of filling by further developent of the inlet geoetry of the leakage air collector to iprove the flow. The leakage air is carefully separated to achieve the optiu constant capacity. KREISEL GMBH & CO. KG Successful coissioning of a at PPC Hercules 1 Introduction The transport of fine bulk solids, such as ceent, raw eal, fly ash or coal, usually takes place pneuatically over coplicated conveying line routes. This eans that the bulk aterial is transported by conveying air through a pipeline syste. The friction that occurs between the bulk aterial and the pipeline wall and the vertical lift in the bulk aterial conveying lines causes a loss of pressure in the conveying air. Consequently, the conveying air for the product transport ust be ade available at a plant-specific pressure. The bulk aterial has to be fed into the air flow of the conveying line against this plant pressure. Different feed systes can be used for this purpose. Coplicated pressure vessel systes or screw pups were used in the past. For over half a decade these systes have been replaced by highly wear-resistant ZSV-H ceraic rotary feeders produced by Kreisel GbH & Co. KG, Gerany. The ost iportant criterion for the use of the Kreisel is the energy saving during plant operation and the considerable wear resistance of the coponents. PPC in South Africa chose a Kreisel ZSV-H 700 for their work in Hercules as the replaceent for a screw pup to ake a power consuption saving of 130 for driving the screw pup. 2 Plant description Figure 1 is a flow chart for a ceent grinding plant. The Hercules PPC factory operates a vertical roller ill for grinding the ceent. The ceent is collected in the downstrea baghouse. An output rotary feeder is placed under each of the two hoppers as well as a shut off valve below the baghouse. It doses the ceent into an airslide that transports the aterial to the DV22 distributor. The airslide diverter feeds the two feeding syste shown in Figure 2 for pneuatic conveying:» the Kreisel (Figure 2, on the right)» the standby screw pup (Figure 2, on the left) The Duo-Cell silo and the packing plant are fed by the pneuatic conveying syste. The Kreisel ZSV-H has been installed so that it can load all three receiving points. The pneuatic transport covers approxiately with a vertical conveying height of 53. The conveying capacity is 150 t/h. The existing pressure generators can also be used by the ZSV-H operation. The ceraic rotary feeder and its feed hopper were fitted into the existing plant so that no odifications on the steel structure or the conveying line were necessary. All Kreisel 1 Flow diagra of the pneuatic conveying plant 4 Coparison of the Kreisel with a screw pup With the Kreisel ZSV-H, Kreisel GbH & Co.KG has a feeder that eets current custoer deands for high precision. After decades of developent and optiization the rotary feeders fro Kreisel are known across all industries for their high quality of anufacture and their reliability. The ceraic lining of the product contact surfaces allows this traditional product to be used as a feeder in pneuatic conveying systes with abrasive aterials. For a long tie the wear caused by flow had been the reason why the rotary feeders were not used as feeders for abrasive aterials. The use of the latest ceraic eleents eans that the necessary requireents for the feeders are now far exceeded. The Kreisel ZSV-H can not only contribute its outstanding properties to the pneuatic conveying The functioning of a screw pup is explained briefly with the aid of the scheatic diagra (Figure 5) so that the Kreisel ZSV-H can be copared with a screw pup. The bulk aterial falls through the inlet (1) in the pup surge bin (2). This is used to draw off the sealing air and the air displaced fro the bulk aterial. The bulk aterial is picked up and transported to the outlet by the high speed copression screw (1000 rp). The bulk aterial is heavily copressed. This copression is assisted by a check flap (4). The copression produces a high-density plug of bulk aterial that provides a seal against the pressure in the conveying pipeline. The solid bulk plug then drops into the outlet of the screw pup where it is picked up by the conveying air and transported into the conveying pipeline. The conveying air has to pass through a nozzle or, depending on the design, several nozzles in the outlet housing. This nozzle produces a pressure drop of about 0.30 bar and serves to accelerate the conveying air and the bulk aterial. The differences between Kreisel Ceraic feeders and screw pup are as follows. systes but is also better than the established input systes with regard to service life, aintenance and spare parts requireents. The arguent that was often cited in the past for a high energy loss because of the escaping leakage air in the feed area has been countered by the use of side plates at the rotor and by the precision of the very sall gaps. Solid construction and grinding of the ceraic eleents guarantee the sall gaps and define predictable quantities of leakage air. These copare favourably with the energy loss of the nozzles used in other systes. Now that the Kreisel ZSV-H had et the custoer requireents for reliability and energy efficiency it was still necessary to verify the integration. Here again the Kreisel s can reveal their potential thorough their sall space requireent and low weight, and have no proble with satisfying the safety officers. Regulated space conditions and the static liits of the existing steel structure for loads and vibration severely liited the plant anufacturer s roo for anoeuvre. This is why it is only with the rotary feeder that the custoer s chosen transfer points could be ipleented. 2 Stand-by pup (on the left) and new Kreisel rotary feeder (on the right) after odification 4.1 Foreign bodies If foreign bodies, such as the reains of grinding balls, are introduced accidentally with the bulk aterial then they ust pass through the feeder. Using the exaple at the PPC the screw pup has a peripheral speed of > 15 /s, whereas the rotary feeder works with < 0.70 /s. In screw pups this can lead to breakage of the wear bushes or the end flight of the screw. In the rotary feeder it is unlikely that these foreign bodies will eet the rotor in such a position that they cause jaing, and even jaing does not norally daage the rotary feeder. 4.2 Properties of the bulk aterial The properties of the bulk aterial, such as fineness (Blaine), grain size distribution, bulk density and oisture, are necessary for diensioning a screw pup. In addition to the back pressure in the conveying pipeline these paraeters affect the diensioning of the drive otor. If these properties are changed by fluctuating processing conditions, this can lead to failure of the screw pup. The results are loss of capacity, otor overloading and sealing probles. Bulk aterial that is too fine or too coarse can only be fed at low pressures (<0.5 bar) because the plug foration is inadequate. For the design of the rotary feeder, however, only the density of the bulk aterial is crucial. The drive is deterined exclusively by the diensioning of the rotary feeder. A 5.5 otor is installed for the rotary feeder at the PPC plant. This draws a power of less than 1 during operation. 4.3 Grinding aid Grinding aids are used to reduce the energy input during grinding. However, these greatly change the conveying and fluidizing behaviour of bulk aterials because they affect the interolecular forces. The experience of recent years has shown that grinding aids can also have a strong influence on the copression behaviour of the bulk aterials. This reduced the capacity of the screw pups by 30 %. In this connection the 132 otor that was installed proved to be under-diensioned. The rotary feeder does not generate any copression of the bulk aterial for sealing purposes so the grinding aid has no negative effect on the conveying and drive capacity of the rotary feeder. 4.4 Overloading of the inlet area If the aterial dosing to the screw pup is irregular and the screw pup is operated close to the capacity liit, then overloading of the inlet area reduces the capacity. If the pup surge bin fills with bulk aterial then the copressed air fro the plug can no longer be discharged at the inlet. The air is transported through the syste by the plug. The plug becoes unstable and can no longer for a seal against the existing conveying line pressure. This causes a reduction in capacity. The design of the inlet to the rotary feeder separates the dust reoval area fro the inlet area. Overfilling of the inlet therefore leads priarily to an increase in capacity rather than a reduction. 4.5 Wear during operation at reduced load If the ass flow of bulk aterial to the screw pup is too low then the requisite sealing plug cannot for properly. The plug breaks down and the conveying air flows into the inlet area at high speed. This acts on the screw like a sand blast nozzle while in the ceraic-lined rotary feeder this does not have a negative effect. There would also be the option of reducing the wear by lowering the rotational speed. 3 3D ounting planning detail for integration of the ceraic rotary feeder into the existing plant configuration 4.6 Energy consuption during operation at reduced load When the rotary feeder is the input device then, if the ass flow drops, the requisite conveying line pressure also drops. If the back pressure in the conveying line drops then the otor current consuption of the pressure generator will drop too. However, this situation with screw pup conveying is different. In this case the influencing coponent is the nozzle (Figure 6, ite 9) in the outlet housing. As with any nozzle the pressure loss increases with increasing flow rate. If the delivery line pressure in the screw pup conveying syste drops then the operating volue of the con-

4 3 Coissioning of the Kreisel Kreisel invited the plant engineers fro PPC to Gerany in Deceber 2014 to present the Kreisel. After detailed design discussions PPC decided to replace the screw pup by the Kreisel. The rotary feeder was installed after a delivery tie of 5 onths. Kreisel engineered the integration of the Kreisel ZSV-H (Figure 3) into the existing plant configuration (Figure 4). It was possible to use the existing support structures of the screw pup for the assebly. The existing screw pup was disantled and the Kreisel ZSV-H was installed within a very short tie frae. The project anageent was carried out so that the air lines of the pressure generators, the ceent feed and the conveying pipeline could be optially integrated into the technical process. The erection and coissioning were supervised by Kreisel. The installation was followed by the coissioning in which the half-day cold coissioning was followed by the hot coissioning. The grinding plant was started at 100 t/h. After a short tie the plant capacity was increased to 110 t/h and this capacity was kept constant overnight. Over the next two days of operation the ill output was adjusted to the expected conveying capacity of the of 150 t/h. The conveying line back pressure settled to about 1.1 bar. The increase in ill output during the coissioning resulted in the evaluation that the ZSV-H could feed at least 180 t/h of ceent into the existing conveying pipeline. Kreisel achieved the axiu degree of filling by further developent of the inlet geoetry of the leakage air collector to iprove the flow. The leakage air is carefully separated to achieve the optiu constant capacity. KREISEL GMBH & CO. KG Successful coissioning of a at PPC Hercules 1 Introduction The transport of fine bulk solids, such as ceent, raw eal, fly ash or coal, usually takes place pneuatically over coplicated conveying line routes. This eans that the bulk aterial is transported by conveying air through a pipeline syste. The friction that occurs between the bulk aterial and the pipeline wall and the vertical lift in the bulk aterial conveying lines causes a loss of pressure in the conveying air. Consequently, the conveying air for the product transport ust be ade available at a plant-specific pressure. The bulk aterial has to be fed into the air flow of the conveying line against this plant pressure. Different feed systes can be used for this purpose. Coplicated pressure vessel systes or screw pups were used in the past. For over half a decade these systes have been replaced by highly wear-resistant ZSV-H ceraic rotary feeders produced by Kreisel GbH & Co. KG, Gerany. The ost iportant criterion for the use of the Kreisel is the energy saving during plant operation and the considerable wear resistance of the coponents. PPC in South Africa chose a Kreisel ZSV-H 700 for their work in Hercules as the replaceent for a screw pup to ake a power consuption saving of 130 for driving the screw pup. 2 Plant description Figure 1 is a flow chart for a ceent grinding plant. The Hercules PPC factory operates a vertical roller ill for grinding the ceent. The ceent is collected in the downstrea baghouse. An output rotary feeder is placed under each of the two hoppers as well as a shut off valve below the baghouse. It doses the ceent into an airslide that transports the aterial to the DV22 distributor. The airslide diverter feeds the two feeding syste shown in Figure 2 for pneuatic conveying:» the Kreisel (Figure 2, on the right)» the standby screw pup (Figure 2, on the left) The Duo-Cell silo and the packing plant are fed by the pneuatic conveying syste. The Kreisel ZSV-H has been installed so that it can load all three receiving points. The pneuatic transport covers approxiately with a vertical conveying height of 53. The conveying capacity is 150 t/h. The existing pressure generators can also be used by the ZSV-H operation. The ceraic rotary feeder and its feed hopper were fitted into the existing plant so that no odifications on the steel structure or the conveying line were necessary. All Kreisel 1 Flow diagra of the pneuatic conveying plant 4 Coparison of the Kreisel with a screw pup With the Kreisel ZSV-H, Kreisel GbH & Co.KG has a feeder that eets current custoer deands for high precision. After decades of developent and optiization the rotary feeders fro Kreisel are known across all industries for their high quality of anufacture and their reliability. The ceraic lining of the product contact surfaces allows this traditional product to be used as a feeder in pneuatic conveying systes with abrasive aterials. For a long tie the wear caused by flow had been the reason why the rotary feeders were not used as feeders for abrasive aterials. The use of the latest ceraic eleents eans that the necessary requireents for the feeders are now far exceeded. The Kreisel ZSV-H can not only contribute its outstanding properties to the pneuatic conveying The functioning of a screw pup is explained briefly with the aid of the scheatic diagra (Figure 5) so that the Kreisel ZSV-H can be copared with a screw pup. The bulk aterial falls through the inlet (1) in the pup surge bin (2). This is used to draw off the sealing air and the air displaced fro the bulk aterial. The bulk aterial is picked up and transported to the outlet by the high speed copression screw (1000 rp). The bulk aterial is heavily copressed. This copression is assisted by a check flap (4). The copression produces a high-density plug of bulk aterial that provides a seal against the pressure in the conveying pipeline. The solid bulk plug then drops into the outlet of the screw pup where it is picked up by the conveying air and transported into the conveying pipeline. The conveying air has to pass through a nozzle or, depending on the design, several nozzles in the outlet housing. This nozzle produces a pressure drop of about 0.30 bar and serves to accelerate the conveying air and the bulk aterial. The differences between Kreisel Ceraic feeders and screw pup are as follows. systes but is also better than the established input systes with regard to service life, aintenance and spare parts requireents. The arguent that was often cited in the past for a high energy loss because of the escaping leakage air in the feed area has been countered by the use of side plates at the rotor and by the precision of the very sall gaps. Solid construction and grinding of the ceraic eleents guarantee the sall gaps and define predictable quantities of leakage air. These copare favourably with the energy loss of the nozzles used in other systes. Now that the Kreisel ZSV-H had et the custoer requireents for reliability and energy efficiency it was still necessary to verify the integration. Here again the Kreisel s can reveal their potential thorough their sall space requireent and low weight, and have no proble with satisfying the safety officers. Regulated space conditions and the static liits of the existing steel structure for loads and vibration severely liited the plant anufacturer s roo for anoeuvre. This is why it is only with the rotary feeder that the custoer s chosen transfer points could be ipleented. 2 Stand-by pup (on the left) and new Kreisel rotary feeder (on the right) after odification 4.1 Foreign bodies If foreign bodies, such as the reains of grinding balls, are introduced accidentally with the bulk aterial then they ust pass through the feeder. Using the exaple at the PPC the screw pup has a peripheral speed of > 15 /s, whereas the rotary feeder works with < 0.70 /s. In screw pups this can lead to breakage of the wear bushes or the end flight of the screw. In the rotary feeder it is unlikely that these foreign bodies will eet the rotor in such a position that they cause jaing, and even jaing does not norally daage the rotary feeder. 4.2 Properties of the bulk aterial The properties of the bulk aterial, such as fineness (Blaine), grain size distribution, bulk density and oisture, are necessary for diensioning a screw pup. In addition to the back pressure in the conveying pipeline these paraeters affect the diensioning of the drive otor. If these properties are changed by fluctuating processing conditions, this can lead to failure of the screw pup. The results are loss of capacity, otor overloading and sealing probles. Bulk aterial that is too fine or too coarse can only be fed at low pressures (<0.5 bar) because the plug foration is inadequate. For the design of the rotary feeder, however, only the density of the bulk aterial is crucial. The drive is deterined exclusively by the diensioning of the rotary feeder. A 5.5 otor is installed for the rotary feeder at the PPC plant. This draws a power of less than 1 during operation. 4.3 Grinding aid Grinding aids are used to reduce the energy input during grinding. However, these greatly change the conveying and fluidizing behaviour of bulk aterials because they affect the interolecular forces. The experience of recent years has shown that grinding aids can also have a strong influence on the copression behaviour of the bulk aterials. This reduced the capacity of the screw pups by 30 %. In this connection the 132 otor that was installed proved to be under-diensioned. The rotary feeder does not generate any copression of the bulk aterial for sealing purposes so the grinding aid has no negative effect on the conveying and drive capacity of the rotary feeder. 4.4 Overloading of the inlet area If the aterial dosing to the screw pup is irregular and the screw pup is operated close to the capacity liit, then overloading of the inlet area reduces the capacity. If the pup surge bin fills with bulk aterial then the copressed air fro the plug can no longer be discharged at the inlet. The air is transported through the syste by the plug. The plug becoes unstable and can no longer for a seal against the existing conveying line pressure. This causes a reduction in capacity. The design of the inlet to the rotary feeder separates the dust reoval area fro the inlet area. Overfilling of the inlet therefore leads priarily to an increase in capacity rather than a reduction. 4.5 Wear during operation at reduced load If the ass flow of bulk aterial to the screw pup is too low then the requisite sealing plug cannot for properly. The plug breaks down and the conveying air flows into the inlet area at high speed. This acts on the screw like a sand blast nozzle while in the ceraic-lined rotary feeder this does not have a negative effect. There would also be the option of reducing the wear by lowering the rotational speed. 3 3D ounting planning detail for integration of the ceraic rotary feeder into the existing plant configuration 4.6 Energy consuption during operation at reduced load When the rotary feeder is the input device then, if the ass flow drops, the requisite conveying line pressure also drops. If the back pressure in the conveying line drops then the otor current consuption of the pressure generator will drop too. However, this situation with screw pup conveying is different. In this case the influencing coponent is the nozzle (Figure 6, ite 9) in the outlet housing. As with any nozzle the pressure loss increases with increasing flow rate. If the delivery line pressure in the screw pup conveying syste drops then the operating volue of the con-

5 4 Planning detail for integration of the into the existing plant peripherals a rotary feeder, the otor for 180 t/h of raw eal, for exaple, has a rating of 5.5 and during operation it uses less than Grain destruction The high copression of the bulk aterial due to the relative oveent of the screw pup leads to destruction of the grains, which, depending on the industry (e.g. the aluina industry), shall be avoided. Kreisel s cause no appreciable grain destruction. veying air will increase. This leads to an increase in velocity. The pressure before the nozzle falls significantly but the pressure after the nozzle falls only slightly. Operation of screw pups at reduced load is therefore very unfavourable fro the energy point of view. 4.7 Wear reduction by reducing the speed The wear on the depends on factors such as hardness and shape of the bulk aterial, the pressure difference across the feeder and the rotational speed of the feeder. The wear can be reduced by adjusting the rotary speed to suit the respective conveying bulk aterial ass flow. This is not possible with screw pups. The high rotational speed of the screw shaft is required to fulfil the sealing function. 5 Screw pup 4.8 Influence of the back pressure on the pup otor The size of otor for the screw pup is alost linearly dependent on the back pressure in the conveying line. Even at average conveying capacities this results in otor sizes of 30 to 250. On the other hand the otor for the rotary feeder is deterined only by the size of the rotary feeder. In 4.10 Motor control centre (MCC) Thanks to the sall drive otor for the rotary feeder and the saller pressure generator otor the MCC can be also ade considerably saller and therefore less expensive. These costs can aount to tens of thousands of euros Coissioning As already entioned in Sections 4.2 and 4.3, the screw pup reacts to various syste paraeters. Multiple odifications are necessary to achieve the correct screw pup configuration during the coissioning while taking the points in 4.2 and 4.3 into account. Screw pitch, plug length, nozzle diaeter and return flap adjustent ust be deterined in tie-consuing conversion processes. The rotary feeder, however, does not respond to these paraeters. A rotary feeder can usually be brought into operation in one to two days Space requireent The low space requireents of the ZSVH can be entioned as the final advantage. As can be seen fro Figure 2 and Figure 7, the ZSV-H can be adapted to suit virtually all local conditions. A rotary feeder can be installed anywhere where there is space for a screw pup with its pup surge bin. At PPC Hercules, for exaple, the screw pup is 4500 long while the Kreisel ceraic rotary feeder requires only 2150 including otor Leakage air Because of the prevailing pressure differences the leakage air flow in rotary feeders is directed against the flow of bulk aterial. This lies between 5% and 12% of the total quantity of conveying air. It is discharged via the dust collector. At PPC the leakage air accounts for 6.4 % of the total copressor power while the energy loss caused by the screw pup nozzle is 15.5 % Capacity of the Cerafeed ZSV-H Depending on the length of the rotary feeder the conveying capacity of the ZSV-H is between 0.3 and 250 3/h. Conveying line pressures of up to 2.0 bar can be applied, depending on the bulk aterial. 5 Energy balance using the exaple of PPC Hercules PPC operates various pneuatic conveying systes at the Hercules plant. Two of the are used to transport ceent fro the grinding plant to the receiving silos. The ceent was fed into the conveying lines by screw pups. Repeated probles, loss of capacity and high energy consuption gave PPC reason to bring about soe technical changes. PPC settled for the latest state of the art s fro Kreisel Gerany. Table 1 shows the syste paraeters of the pneuatic conveying plant with a screw pup as the feed coponent. The data records show a axiu stable conveying capacity of t/h, depending on the type of ceent. In addition to the inadequate conveying capacity there were screw pup failures for various reasons. The operation was disrupted by overfilling and otor failures. In Septeber 2015 the standby conveying screw pup was replaced by a Kreisel ZSV-H, size 700. It was coissioned within two days. A stable conveying capacity of 140 t/h was obtained during the coissioning. The plant capacity was increased to 175 t/h by optiizing the grinding and filter processes and it was found that the Kreisel ZSV-H had not yet reached its liits. So far the plant has been in continuous operation for four onths. Table 1 Plant data of the pneuatic conveying of ceent at PPC Hercules Plant data Bulk solid Blaine Bulk density Raw density Max. conveying distance Conveying altitude Conveying line diaeter Screw pup size Rotary feeder size Motor (installed) Bulk solid teperature Plant altitude Max. stable conveying capacity ²/g DN C t/h Screw pup Ceent /130 Ceraic rotary feeder Ceent > 175 Figure 2 shows the plant layout after conversion to the Kreisel ZSV-H. The inlet was adapted to allow continued use of the support structure for the supporting the screw pup This resulted in very short conversion ties. The driving power of the rotary feeder is easured continuously by the custoer. Due to the special bearings the rotary feeder operates at a power of less than 1. Replaceent of the screw pup by a ceraic rotary feeder has saved a significant proportion of the energy costs of pneuatic conveying. As a result, the return on investent is less than one year. 6 Suary By replacing the screw pup with a Kreisel ceraic rotary valve PPC was able to increase its ceent transport capacity to at least 175 t/h. Other advantages are a stable, reliable pneuatic conveying syste with a very low energy consuption. An annual aount of energy saving of approxiately has been achieved. This is one of ore than two dozen successful projects involving a Kreisel. Meanwhile, PPC has ordered ore ZSV-Hs to replace screw pups in South Africa. Kreisel and PPC are jointly investigating the behaviour and lifetie of the rotary valve. Table 2 Energy dates Data Operation tie Energy cost Shaft power requireent of the feeder Shaft power requireent of the copressors Su energy deand Total energy consuption Energy costs Energy savings Energy costs savings per year Retourn of invest h/a /h h/a /a % year Screw pup size 300 Rotary valve size 700 x < 3/4 This article reports on the advantages of the ZSV-H Kreisel over screw pups and on the successful coissioning of a ZSV-H for PPC Hercules in South Africa. TEXT JD Visser1, Process Engineer, Nyiko Mayiele1, Plant Engineer, Mario Dikty2, Branch Manager 1 PPC Ceent, Hercules/South Africa 2 Kreisel GbH & Co. KG, Krauschwitz/Gerany

6 4 Planning detail for integration of the into the existing plant peripherals a rotary feeder, the otor for 180 t/h of raw eal, for exaple, has a rating of 5.5 and during operation it uses less than Grain destruction The high copression of the bulk aterial due to the relative oveent of the screw pup leads to destruction of the grains, which, depending on the industry (e.g. the aluina industry), shall be avoided. Kreisel s cause no appreciable grain destruction. veying air will increase. This leads to an increase in velocity. The pressure before the nozzle falls significantly but the pressure after the nozzle falls only slightly. Operation of screw pups at reduced load is therefore very unfavourable fro the energy point of view. 4.7 Wear reduction by reducing the speed The wear on the depends on factors such as hardness and shape of the bulk aterial, the pressure difference across the feeder and the rotational speed of the feeder. The wear can be reduced by adjusting the rotary speed to suit the respective conveying bulk aterial ass flow. This is not possible with screw pups. The high rotational speed of the screw shaft is required to fulfil the sealing function. 5 Screw pup 4.8 Influence of the back pressure on the pup otor The size of otor for the screw pup is alost linearly dependent on the back pressure in the conveying line. Even at average conveying capacities this results in otor sizes of 30 to 250. On the other hand the otor for the rotary feeder is deterined only by the size of the rotary feeder. In 4.10 Motor control centre (MCC) Thanks to the sall drive otor for the rotary feeder and the saller pressure generator otor the MCC can be also ade considerably saller and therefore less expensive. These costs can aount to tens of thousands of euros Coissioning As already entioned in Sections 4.2 and 4.3, the screw pup reacts to various syste paraeters. Multiple odifications are necessary to achieve the correct screw pup configuration during the coissioning while taking the points in 4.2 and 4.3 into account. Screw pitch, plug length, nozzle diaeter and return flap adjustent ust be deterined in tie-consuing conversion processes. The rotary feeder, however, does not respond to these paraeters. A rotary feeder can usually be brought into operation in one to two days Space requireent The low space requireents of the ZSVH can be entioned as the final advantage. As can be seen fro Figure 2 and Figure 7, the ZSV-H can be adapted to suit virtually all local conditions. A rotary feeder can be installed anywhere where there is space for a screw pup with its pup surge bin. At PPC Hercules, for exaple, the screw pup is 4500 long while the Kreisel ceraic rotary feeder requires only 2150 including otor Leakage air Because of the prevailing pressure differences the leakage air flow in rotary feeders is directed against the flow of bulk aterial. This lies between 5% and 12% of the total quantity of conveying air. It is discharged via the dust collector. At PPC the leakage air accounts for 6.4 % of the total copressor power while the energy loss caused by the screw pup nozzle is 15.5 % Capacity of the Cerafeed ZSV-H Depending on the length of the rotary feeder the conveying capacity of the ZSV-H is between 0.3 and 250 3/h. Conveying line pressures of up to 2.0 bar can be applied, depending on the bulk aterial. 5 Energy balance using the exaple of PPC Hercules PPC operates various pneuatic conveying systes at the Hercules plant. Two of the are used to transport ceent fro the grinding plant to the receiving silos. The ceent was fed into the conveying lines by screw pups. Repeated probles, loss of capacity and high energy consuption gave PPC reason to bring about soe technical changes. PPC settled for the latest state of the art s fro Kreisel Gerany. Table 1 shows the syste paraeters of the pneuatic conveying plant with a screw pup as the feed coponent. The data records show a axiu stable conveying capacity of t/h, depending on the type of ceent. In addition to the inadequate conveying capacity there were screw pup failures for various reasons. The operation was disrupted by overfilling and otor failures. In Septeber 2015 the standby conveying screw pup was replaced by a Kreisel ZSV-H, size 700. It was coissioned within two days. A stable conveying capacity of 140 t/h was obtained during the coissioning. The plant capacity was increased to 175 t/h by optiizing the grinding and filter processes and it was found that the Kreisel ZSV-H had not yet reached its liits. So far the plant has been in continuous operation for four onths. Table 1 Plant data of the pneuatic conveying of ceent at PPC Hercules Plant data Bulk solid Blaine Bulk density Raw density Max. conveying distance Conveying altitude Conveying line diaeter Screw pup size Rotary feeder size Motor (installed) Bulk solid teperature Plant altitude Max. stable conveying capacity ²/g DN C t/h Screw pup Ceent /130 Ceraic rotary feeder Ceent > 175 Figure 2 shows the plant layout after conversion to the Kreisel ZSV-H. The inlet was adapted to allow continued use of the support structure for the supporting the screw pup This resulted in very short conversion ties. The driving power of the rotary feeder is easured continuously by the custoer. Due to the special bearings the rotary feeder operates at a power of less than 1. Replaceent of the screw pup by a ceraic rotary feeder has saved a significant proportion of the energy costs of pneuatic conveying. As a result, the return on investent is less than one year. 6 Suary By replacing the screw pup with a Kreisel ceraic rotary valve PPC was able to increase its ceent transport capacity to at least 175 t/h. Other advantages are a stable, reliable pneuatic conveying syste with a very low energy consuption. An annual aount of energy saving of approxiately has been achieved. This is one of ore than two dozen successful projects involving a Kreisel. Meanwhile, PPC has ordered ore ZSV-Hs to replace screw pups in South Africa. Kreisel and PPC are jointly investigating the behaviour and lifetie of the rotary valve. Table 2 Energy dates Data Operation tie Energy cost Shaft power requireent of the feeder Shaft power requireent of the copressors Su energy deand Total energy consuption Energy costs Energy savings Energy costs savings per year Retourn of invest h/a /h h/a /a % year Screw pup size 300 Rotary valve size 700 x < 3/4 This article reports on the advantages of the ZSV-H Kreisel over screw pups and on the successful coissioning of a ZSV-H for PPC Hercules in South Africa. TEXT JD Visser1, Process Engineer, Nyiko Mayiele1, Plant Engineer, Mario Dikty2, Branch Manager 1 PPC Ceent, Hercules/South Africa 2 Kreisel GbH & Co. KG, Krauschwitz/Gerany