Gdischarge: energy efficiency for cement silos from IBAU HAMBURG 

Mario Rämmele and Juha Schirmer of IBAU HAMBURG, Germany, describe the new Gdischarge system, which is up to 25% more energy efficient than other systems for large capacity central cone silos.

INTRODUCTION

Energy efficiency has become a major focus of the cement industry and IBAU HAMBURG has been looking at ways to reduce the energy demand of large central cone cement silos, which use compressed air for fluidizing the cement material in the discharge process.

IBAU HAMBURG has equipped more cement silos with extraction systems than any other company and has always set the standards for this technology. In the last few years large- scale tests have been made at the silo plants of several clients to identify how to significantly reduce the energy requirements of silo extraction.

The results are better than expected. Not only can up to 25% of energy consumption be reduced, but wear in the downstream equipment is less and bulk loading times improved. Additionally, silo wall stresses were lower.

THE CENTRAL CONE DISCHARGE TECHNOLOGY

The central cone silo was introduced to the market in 1975 and is used for silos with diameters from 10m to 30m and more with storage capacities of up to 40,000 tonnes (see Fig 1 on p58). Such large-capacity silos for the storage of cement require an efficient and trouble-free discharge system.

The central cone has a displacement function for the material in the silo, which allows the material to flow freely during discharge. The central cone forms a ring area on the silo bottom, which is divided into individual aeration sections that are inclined slightly downwards towards the discharge openings in the cone. The silo bottom (Fig. 2 on p58) is equipped with open fluidslides (aeration pad type) that have an air-permeable fabric on the upper side. The aeration air is blown under the fabric in order to fluidize the cement on the fabric. Each aeration section has its own discharge outlet with a flow control gate (Fig. 3 on 61) that provides a controlled discharge from the silo to the downstream collecting bin.

For silo discharge, one silo section is active at a time. This means that only the fluidslides of one section are aerated and the relevant flow control gate is opened for discharge. The silo bottom is aerated section by section, so that all sections are aerated in a complete cycle. Each outlet has a right-hand and a left-hand aeration sector that can be actuated individually, one after the other, to generate small discharge flow funnels as required by the aeration scheme. So, for discharge only the bulk material above the activated section is in motion and with the uniformity of this procedure large uncontrolled material movements and load peaks on the silo walls are avoided. The result is a controlled silo discharge with a controlled mass flow in the silos according to the ‘Safety First” principle1,2.

The advantages of the IBAU discharge system are: 

  • 100% safe operation;
  • complete usage of the storage volume;
  • no uncontrolled material movements within the silo;
  • almost uniform discharge during an aeration cycle; and
  • no interruption during silo operation. 

 

The quantities of material that can be discharged with such a system vary between 100tph (tonnes per hour) and 1,000tph, depending on the size of the silo and loading requirements. Only very small quantities of air are needed for the material discharge, and the aeration air is removed along with the discharged cement. Typically the energy requirement for such silos with extraction rates of 250tph is in the range of 0.10 to 0.12kWh/t of extracted cement.

About 75% of the power consumption is for the material extraction from the silo, while 25% is for the material transport to the bulk loading, where the biggest consumers are vibrating screens for sieving foreign bodies and the winches of the bulk loading devices. The silo aeration requires about 40–50% of the power consumption in the material extraction from the silo and the rest is required for filter fans, venting system and the control air for the devices.

THE GDISCHARGE CONCEPT

The idea behind the Gdischarge was to optimize the energy requirement for large cement silos with an advanced discharge control system using the
latest blower and compressor technology. With an effective limitation of the differential pressure for the silo bottom aeration, the power used for the generation of the compressed air can be significantly reduced. Furthermore, due to less pressure loss and other energy saving operations, the energy consumption and energy costs are significantly reduced. Regarding this invention, IBAU HAMBURG has filed a European Patent Application (EP2698328).

No compromises have been made to the IBAU central cone concept which is characterized by a number of separate discharge outlets (Fig. 4 below). All system components such as fans and metering devices are designed for maximum discharge capacity and optimized by the Gdischarge system for the required discharge situation. This means that during operation the air volume flow of the blower is automatically adjusted via a controller. In the control procedure alternative discharge requirements for downstream conveying to varying numbers of trucks, railcars, mixer and packing plants can be integrated.

Fig. 5 (right) illustrates how the aeration air can be adjusted for the loading of a truck and the feeding of a mixer with 150tph and 10tph, respectively, from a silo with six discharge outlets. Beside truck loading and mixing other downstream equipment can be incorporated. A converter for the blower and a sensor at the blower form a control unit, which is linked to an intelligent controller (BB). This controller regulates the opening and closing of the flow control gates for the silo discharge to achieve the necessary discharge rate and adjusts the motor speed of the blower depending on the pressure in the flow line.

Target and actual pressure in the flow line regulate the air quantity of the blower.
The blowers that are used by IBAU allow a very wide control range from 25% to 100%. It goes without saying that these blowers are robust and durable, very easy to service and maintain and provide complete oil-free aeration air.

There are two further configuration levels for the Gdischarge: the additional control of the filter installation by means of the monitoring of the negative pressure as well as through the integration of a measuring system which additionally controls the flow rate at the silo discharge (weighing system).

All this leads to a further optimization of the whole discharging process.

TEST RESULTS AND GDISCHARGE ADVANTAGES
The new silo discharge system has been tested by IBAU HAMBURG at different clients in Western Europe under real operating conditions. The results with the Gdischarge are very impressive. In the tests, the power consumption of the existing silo systems was analysed and attempts were made to minimize it.

Table 1 on p63 contains the results of the new installation in Germany. At this client, tests were made with 1 and 2 bulk loading systems of 250tph each. Data for the specific energy consumption in the different sections such as the silo discharge and material transport to the truck loading as well as for the silo aeration, which is part of the silo discharge, are given.

The total specific energy demand has been set at 100% for the discharge of 250tph with the conventional standard discharge system. With the new Gdischarge system and 250tph about 17.5% of energy was saved for the total system. While for the transport system no savings were possible the energy consumption for the silo discharge was reduced by 23.5% and for the silo aeration by as much as 50%.

Economy of scale also has an impact. When in the standard case extraction rates of 250tph and 500tph are compared, it becomes clear that the larger extraction rate reduces the specific energy consumption by 42%. For the silo aeration instead of 35.1% of energy used only 17.5% are used. So, the largest savings in specific energy consumption are by the Gdischarge system at a 500tph extraction rate. Instead of 35.1% for standard silo aeration and 250tph extraction only 8.8% of the energy is required for the Gdischarge and 500tph. Instead of 100% specific energy requirement for the total system only 49.2% is needed.

The new Gdischarge system for 500tph will require about 51,670kWh per year, compared to about 67,540kWh for the standard system before the modification. With an electricity

price of €0.1/kWh the annual savings are in a range of €1,575 to €1,600 Euro. When comparing the price of blowers and converters, amortization rates of less than three to five years can be achieved by the new system.

It is important to know that the new system offers even more benefits. One such aspect is the reduced wear within the system of flow control gates and valves due to a reduction in the air quantities and velocities used resulting in a reduction of the maintenance costs of the system. Furthermore the filter loads are also reduced due to the lower air quantities in the system. Another positive effect is that faster loading operations for trucks and railcars can be achieved due to less aeration air in the cement.

Last but not least a very positive effect is achieved on the formation of flow funnels in the silo. Because of the reduced silo aeration pressure and aeration air quantities, the flow funnels in the silo are smaller in diameter and the core funnels do not touch the silo walls so that the horizontal pressures on the silo walls are more homogenous within the silo and peak loads are reduced.

OUTLOOK

The new Gdischarge system has already been tested successfully and is already planned for new installations. Because of its modular design existing silos can also be modified and equipped with the system. The amortization time of silo modifications will depend mainly on the silo diameter and extraction rates and how much of the new blower technology will be needed. To illustrate the ‘Safety concept’ and reduced formation of flow funnels in the silo, measurements by 3D-laser scanning are envisaged. 

 
 
SCHWENK Zement KG relies on BEUMER Group pipe conveyors  

OPERATIONAL GAINS WITH MINIMAL DISRUPTION AND WITHOUT ANY MATERIAL LOSS
Schwenk Zement KG is replacing its old drag chain conveyor line with a modern pipe conveyor from BEUMER Group. Schwenk Zement required a solution that would transport alternative fuels such as crushed plastic material, textiles and paper from the warehouse to the feeding system of the oven in its cement plant in Bernburg, Germany; this fully closed conveying system makes transporting bulk material more environmentally friendly and energy efficient. Maintenance costs are also considerably lower.

Pipe conveyors are able to navigate long distances and tight curve radii. Due to their ability to negotiate curves, considerably fewer transfer towers are required compared to other belt 

conveyors. This results in substantial cost savings for the customer and delivery of a system customized for individual routing. BEUMER Group supplied and installed a system with a diameter of 200 millimetres and a length of 230 metres. It conveys up to 15 tonnes of material per hour. BEUMER was also responsible for the design of the system and the entire steel structure.

Another system advantage is the reduced noise emission of the pipe conveyors. Special idlers as well as low-noise bearings and electric motors work very quietly. This improves the quality of the employees' day-to-day work environment and ensures the 

people living near the plant are not disturbed. It took only eight months from the time the contract was awarded until commissioning of the new system in February 2014.

BEUMER Group is an international manufacturing leader in intralogistics in the fields of conveying, loading, palletizing, packaging, sortation and distribution technology. Together with Crisplant a/s and Enexco Teknologies India Limited, the BEUMER Group employed some 4,000 people in 2014. The group generated an annual turnover of approximately €680 million. With its subsidiaries and sales agencies, BEUMER Group is present in many industries worldwide.

The pipe c

HAVER ADAMS® – water-tight cement bagging that is clean and efficient 

“HAVER ADAMS® – clean, efficient ... and excellent in every sense of the word!” This praise comes from experts who know what they are talking about: as part of a Lafarge supplier competition covering the cement sector, the HAVER & BOECKER ADAMS® technology for filling powder-type products into water-tight PE bags received the prize in the category of sustainability. “With the ADAMS® we have developed a filling machine for PE bags that offers a series of advantages,” explained Robert Bru¨ggemann, Business Unit General Manager HAVER Chemicals. “The PE bags used are characterized by enormous water-tightness and resistance to tearing. Bag damage and ruptures during filling can be reduced by an average of 80% to 90% percent,” added Heinz-Werner Bunse, Sales Manager of the Cement business unit at HAVER & BOECKER.

Packing into PE bags enables customers to benefit from a series of advantages. During filling and transport there is a comparably lower level of product loss. Cost savings in transport are the result of reduced freight volume and the elimination of additional protective packaging. “Less bag breakage, high levels of weight accuracy, improved health protection from a dust-free solution and CO2 savings with 100% recyclable material lead to significantly higher customer satisfaction,” says Bru¨ggemann, who is convinced of the new technology.

Bunse experienced the development of the bags first hand: approximately 49 years ago the technician began his apprenticeship at HAVER & BOECKER. Back then, he was familiar with the use of jute sacks. “During the 1920s, when the technology was developed, there was a huge technical development in this segment,” Bunse said while summarizing his impressions of the decades-long innovation management. They were customized to suit the individual needs of various industrial branches, and increasingly more efficient solutions were brought to the market. “The filling of PE bags expands the opportunities in the global cement market and creates options that improve and simplify the weather-proof storage of goods,” says Bunse. Bru¨ggemann adds:“Currently some 10% of all bags do not reach their point of destination — mainly because of inadequate shelf life and bag breakage. This error rate can be profoundly reduced

by using PE bags.” He proudly points to more than 70 references in 18 countries where the ADAMS® technology has been in use since 2005. Here the scrap amount has been reduced to almost zero. These machines were designed to handle 5–50kg bags. Now a current reference project is opening up totally new perspectives for one building material producer who wishes to pack products into PE bags within a weight range of one to ten kilograms. “The packing possibilities increase, and accuracy in filling is improved, transport and handling are simplified. This altogether has positive effects on sales and customer use,” says Bru¨ggemann.

All these advantages result in large part also from the innovative vibration technology and the dust-tightness of the process, which in the end assures a clean final product. “With the ADAMS® we have succeeded in developing a technology that fulfills all the market requirements when it comes to improving storage capacity and product cleanliness,” elaborated Bru¨ggemann. Once the filling of powder-type products into PE bags had gained acceptance on the market, a Innovation Management team went to work on a HAVER & BOECKER

ROTO-PACKER ADAMS® MINI over a period of two years. The team used past experience with the technology and developed new, detailed solutions for small bags which are to be on display in the standing position on store shelves.

The new machine forms a tube from a flat film by welding the side seams and bottom seam and then cutting off the produced bag from the plastic film tube. The bags are then placed in open cassettes arranged in a circle on a rotating unit. The product is filled step-by-step, precisely dosed and compacted. By siphoning off the air just above the product and welding the top seam, a hermetically sealed package that provides optimum protection against moisture is the final result.

“The ADAMS® technology is foremost suitable for countries where processes such as loading and unloading are mostly done manually. At the same
time the technology is suitable for climatic conditions where the material has to be protected from the weather elements,” says Bunse. But this does not only make the ADAMS® technology a leading export for Africa, Asia and South America: “We are convinced that this technology will replace the older, classic HAVER & BOECKER ROTO-PACKER® all across Europe.” For plant operators, using ADAMS® technology also means the opportunity to free up personnel and to allow them to take on new duties and to improve plant productivity. “The high level of automation requires an operator skill profile that is more than what we were used to seeing in the past,” admits Bru¨ggemann. However with the right training it is absolutely possible to rely on a single person for the operations and monitoring of various machines. For this case the HAVER specialists have created a training programme that includes the aspects of material flow and bag handling.

Aspects such as recycling and re-use of PE material are especially important factors in countries where manual handling was common in transport and storage.“Filling powder products into PE bags will define a new industrial standard,” Bru¨ggemann is convinced.The resilience with which HAVER & BOECKER wishes to develop new technology is best illustrated by a machine of an earlier generation, one that is now currently operating at Lake Baikal in Siberia: here HAVER & BOECKER technology has been in operation for 78 years. 

 
Protecting environment by keeping dust emission to a minimum 

Controlling dust emission is an ongoing challenge when handling dry bulk materials — including cement — as dust pollution is both an environmental threat and constitutes a severe health hazard. An increased focus on dust emission, combined with stricter legislation, demands better technological solutions and high-performance equipment.

Cimbria Moduflex has a long history of supplying dust-free loading chutes to the cement industry to improve the general environment and working conditions as well as assist the manufacturers in reducing the running costs for their outloading stations. The company’s success is based on the ability to differentiate on a market characterized by increased demands for flexible and environmentally compatible equipment. A wide high- quality product programme consisting of standard parts makes it possible to customize loading chutes to match specific customer applications. This, combined with short and reliable time of delivery, makes Cimbria Moduflex a preferred supplier of loading solutions. Furthermore, the company is an acknowledged problem solvers with the ability to create innovative solutions that take particular customer requirements into account.

SUPPLYING RECENTLY DEVELOPED MODEL FOR THE CEMENT INDUSTRY
In co-operation with Cimbria Moduflex’s Belgian partner,TBMA Belgium, Cimbria Bulk Equipment has delivered a Moduflex loading chute for the Holcim site in Obourg, Belgium.

The loading station is situated along the quay site and the company needed equipment for open and closed outloading of cement into various types of ships and barges from the same installation taking specific requirement as flexibility, dust elimination and installation height into account. In 2011, the company TBMA Belgium ordered a type N300 Moduflex loading chute with interchangeable outlets for the Holcim site in Obourg. The same customer recently ordered a loading chute similar to the earlier supplied chute. The loading chute is delivered with flatbed outlet, but prepared for the earlier supplied interchangeable outlets.

This specific model was chosen as it contains an integrated filter and has a low built-in height. For years, Cimbria Bulk 

Equipment has supplied loading chutes with integral filter, where the filter module is part of the inlet construction. This is a well- proven solution when it comes to functionality; nevertheless, it requires a certain built-in height for installation. The N300 model is a recently developed model with a side-mounted filter which makes the built-in height virtually the same as a non-filter loading chute. The model also contains an integral filter and therefore the costly installation of the duct work into a central filter bag installation is avoided. The filter is mounted on a rectangular flange built out on a transition piece from the inlet part of the chute and it is externally supplied with 5–6 bar pressurized air; it is managed by the PLC in the control box of the loading chute.The side- mounted filter is characterized by being very service friendly as it provides easy access to replacement of the filter cartridges from the ‘clean side’. At the same time, it has been possible to increase the filter surface area that, in some cases, is needed to handle particular products.

For increased outloading flexibility the loading chute is prepared for interchangeable outlets for loading into both tanker ships and open barges from the same installation. For easy change-over the chute outlets are equipped with a special snap lock system.

Due to the abrasive character of the product, the chute inlet is supplied with an inlet liner in Hardox 400. The chute is equipped with 27 PVC chute modules which give the chute an extended length of more than 9,000mm. The modular construction ensures an quick and easy replacement in case of modification or repairs. The replacement can be carried out with limited downtime as it can be done out without dismantling the loading chute.

The chute is equipped with internal overlapping cones in steel for optimum separation of product and exhaust air. 

 
SUPPLYING THE CEMENT INDUSTRY IN PORT TERMINALS  

The Spanish Moduflex partner, Masanes Suministros Industriales S.A, recently supplied a loading chute for loading cement clinker into flatbed trucks. The temperature and the abrasive character of the material demanded high temperature execution and abrasion-resistant equipment. The supplied loading chute is a Moduflex D300, a heavy duty model supplied as a complete solution independent of external filters as it equipped with a fully self-contained built-in filter with its own fan, pressure tank and nine filter cartridges. For high durability the chute inlet is supplied with replaceable 4mm Hardox 400 in-liner.

The chute is equipped with 10 chute modules manufactured in heavy duty NPG material that has high resistance against the heat radiating from the material (working range up to 130°C). The modular construction ensures an easy and quick replacement in case of maintenance or repairs. The replacement can be carried out with minimal downtime without dismantling the loading chute.

For optimum separation of product and exhaust air, the chute is equipped with internal overlapping cones in Hardox 400. Furthermore, the chute is equipped with an outlet for flatbed trucks, with a high temperature rubber skirt for encapsulating the dust arising from the material pile during the loading process. A high temperature capacitive indicator is placed in the chute outlet where it acts as a control of the automatic raising of the chute during loading. When the material reaches the indicator, the chute will raise a pre-determined distance, until the indicator is free of the material, and then stop in order to keep the skirt in contact with the material pile. This action will continue during the loading process until the flow of the material is stopped by the control system.

With almost 14,000 units produced, Cimbria Moduflex dust-free loading chutes for bulk materials loading are in operation world wide. Inherent functional efficiency is enhanced by the modular nature of their design, an innovation that contributes significant savings in overall lifecycle costs. Cimbria Bulk Equipment supplies dust-free chute systems through a network of agents in more than 30 countries around the world.  
 
 

Mondi launches rain-resistant Splash Bag

In response to lively customer interest for rain-repellent paper bags, Mondi has developed the Splash Bag. This new bag resists rain for up to two hours and withstands humidity better than a standard paper bag.

Standard paper bags for packaging cement and other powdery products are generally vulnerable to rain. To tackle the issue, Mondi, working in collaboration with major cement producer Lafarge, has developed an innovative rain-repellent bag particularly suitable for cement. The new wet-strengthened, machine-finished Splash Bag is designed to absorb less moisture than conventional bags. Its outer ply of Mondi Advantage Protect sack kraft paper has a water-repellent surface and is formulated to keep high tensile strength even in a wet environment. It also helps prevent moisture ingress if conditions are damp or humid during storage. Advantage Protect sack kraft papers have a water-repellent surface and are formulated to have high tensile strength, to help prevent rupture. For example, the wet tensile strength of Advantage Protect in a grammage of 80g/m2 is three times higher than that of standard sack kraft paper — an impressive figure.

Splash Bag’s water-resistive properties are immediately apparent in side-by-side visual testing versus standard paper cement bags (test conditions simulating direct exposure to rain). “Water gathers on the bag’s surface without being absorbed, then evaporates over a period of several minutes, leaving the bag essentially dry,” explains Claudio Fedalto, deputy COO Mondi Industrial Bags. “By contrast, the standard bag absorbs the water, weakens as a result and may potentially rupture if exposed to extremely wet conditions,” he adds. Results of Cobb tests, which measure the amount of water absorbed into the surface by sized paper over a set period of time, indicate that Splash Bags are resistant to rain for two hours. If inadvertently left in damp (rather than wet) conditions, e.g. on damp sand, Splash Bag resists moisture ingress for up to 12 hours.

Even after two hours of direct exposure to rain, Splash Bags can be moved, handled and emptied without any difficulties. Bag breakage rates are significantly reduced, leading to genuine cost savings: fewer broken bags translate to lower vehicle and site clean-up costs, fewer trips from warehouse to site, as well as time savings for logistics and site managers. Excellent moisture resistance can also mean better protection of the filling good if conditions are damp or humid at the warehouse.

Importantly, none of these advantages comes at the expense of filling speeds or de-aeration rates, which match those of standard bags (in tests performed on Mega Gurley equipment at Mondi’s Bag Application Centre in Austria).

According to interviews carried out at construction sites, Splash Bag has already won generous plaudits from construction workers for its ability to resist rain and moisture when used to package cement.The construction workers surveyed were particularly impressed that the bag shrugs off rain and remains strong and easy to handle even under damp conditions.

ABOUT MONDI INDUSTRIAL BAGS

Mondi Industrial Bags, a business segment of Mondi’s Europe & International Division, is a major international producer of industrial paper bags, selling around 5 billion bags per year. Thanks to its broad range of bag specifications, Mondi Industrial Bags serves major industries including cement and building materials, chemicals, food, feed and seed. The business segment operates a dense sales and service network, the specialized filling equipment department Natro Tech, as well as its Bag Application Centre, where researchers develop and test innovative packaging solutions.

ABOUT MONDI

Mondi is an international packaging and paper group, employing around 24,000 people in production facilities across 30 countries. In 2013, Mondi had revenues of €6.5 billion and a return on capital employed of 15.3%. The group’s key operations are located in central Europe, Russia, the Americas and South Africa. The Mondi Group is fully integrated across the packaging and paper value chain - from the management of its own forests and the production of pulp and paper (packaging paper and uncoated fine paper), to the conversion of packaging paper into corrugated packaging, industrial bags, extrusion coatings and release liner.  
 
 
Bulk storage and handling for the cement sector  

One thing all cement manufacturers have in common is dry bulk stockpiles... and the need for storage and handling solutions, writes Melanie Saxton, Geometrica. The goal is to protect the chemical properties of the raw materials (especially limestone), while safeguarding the surrounding landscape from contaminates. Another goal is to cover the stockyard as efficiently as possible regardless of location, topography or climate.

Geometrica domes accommodate the commercial equipment necessary to produce cement within column-free domes. The no-barrier interior permits maximum use of space without the traditional restrictions of post and beam systems. Now stockpiles that have been left uncovered can contain dust and contaminated runoff without resorting to silos, which are small and expensive.

For spans of 50m and above, traditional framing systems become too complex and expensive. Geometrica offers practical, affordable and beautiful solutions with elliptical or compound domes that result in a smaller surface area and better clearance for vehicles around the perimeter. Geometrica domes provide the most efficient shape for a stockpile enclosure because they are lightweight and can span up to 300m without intermediate supports. The goal is to have the dome ‘hug’ the clearance line of the stacker-reclaimer.

RING-SHAPED STOCKPILES

The shape and size of the stockyard determines the dimension and span of the dome. Ring-shaped stockpiles are normally stored inside a covered dome to address environmental concerns. A slewing stacker at the centre stacks the material and creates the pile, while a bridge or a portal rake reclaims the material from a face of the pile. Limestone, clay, marl, coal, and many other materials are stored in automated ring piles.

Typically, a dome for this application will need to cover an additional 3m to 6m width area around the base circumference of the pile for reclaimer clearance and circulation of maintenance personnel or small vehicles. Thus, the diameter of a dome for this application is usually 6m to 12m more than the pile’s diameter. The dome’s height is normally set at about 1/3 of the diameter for efficiency, but may be substantially lower or higher if desired.

Geodesic domes for ring piles also need to clear the reclaimer at its highest point near the perimeter of the stockpile, as well as provide a minimum height for the vehicles in the free area around the material. Instead of using an expensive vertical wall to achieve this, Geometrica can supply domes with elliptical or compound parabolic profiles that have a steep slope near the perimeter. Such geometries provide the necessary clearance and achieve additional savings compared to conventional framed buildings or domes with plain circular cross section.  

CONICAL PILES

Clinker is often stored in conical piles and reclaimed through underground extraction hoppers and tunnel conveyors. Dead loads may be handled with front-end loaders. Because of larger drops when stacking a conical pile as compared with a slewing stacker, conical stockpiles produce blinding amounts of dust when left uncovered. For these piles it is possible to use domes with a profile that closely follows the shape of the pile, such as a parabola. This form results in a most economical enclosure. The dome may also be set on a concrete wall, increasing capacity while realizing substantial savings as compared with a concrete dome solution.

If the dome sits on the ground, it is important to consider the effect of accumulating fines around the perimeter, at the base of the pile. The dust is aerated when settling, which gives it a very small angle of repose. Because of this, the pile grows over time. It is advisable to mount the dome on a short (1.5m- to 2.5m- high) concrete wall, or leave a gap around the pile where a small front-end loader may circulate to remove accumulated dust.

Ideally the reclaim tunnel(s) will extend all the way across the pile area to the opposite side, so that the dead-load fines may also be easily pushed to the reclaim chute and removed from the dome with the use of the front-end loader. Geometrica also offers replaceable breakaway panels that may be installed on the bottom module of the dome to prevent damage in case of accidental lateral overloading. Geometrica domes are designed to withstand the specified or requested loading for each installation. With Geometrica’s unique perimeter-in construction technology, geodesic domes for conical piles may be installed over operating stockpiles, minimizing or eliminating downtime.

LONGITUDINAL STORAGE

Another common way to store large volume bulk materials is by stacking them in long, prismatic piles. The material is loaded with a side stacker, or with a tripper car from above. Reclaiming is done with a bridge or side scrapper reclaimer or with front end loaders. Geometrica offers efficient longitudinal structures in cross sections that suit the project’s conditions. Parabolic or acute geometries are best for large crest loads, such as tripper cars, which these domes can easily support. Circular cross sections are ideal for large wind loading sites. Bents start vertically to minimize the footprint of the building. The ends of any enclosure may be left open, or closed with semi- domes or flat space frame walls.

Geometrica longitudinal structures are particularly suited for highly corrosive environments. The structural tubes may be galvanized steel or aluminium, and either of these materials may be finished with a highly resistant thermoset epoxy or polyester coating. Cladding may be steel, aluminium, fibre-reinforced plastic (FRP), polycarbonate, or a combination of these. For aggressive interior environments, FRP cladding may be applied internal to the structure.

ECONOMICAL AND EFFICIENT

Dozens of Geometrica’s stockpile storage and materials handling domes have been built around the world to safely enclose stockyard machinery, personnel, and raw materials. Parts are packaged, bar coded and shipped in small crates that can be easily handled in remote locations. The parts are assembled by local labour without special equipment over a stockpile, even while the pile remains in operation — no downtime. The light, prefabricated domes offer overall lower lifetime maintenance cost when compared to traditional structures.

 
 
Specialist technologies overcome cement materials handling challenges  

“Many players in the industry are justifiably asking whether the cement industry is the next ‘hot’ industry in Africa, given that this continent needs to expand and build its infrastructure if its full economic potential is to be unlocked”, says Paul van de Vyver, General Manager of materials handling and niche process plant specialist, DemcoTECH Engineering.

There is increased buoyancy in the cement industry with producers looking to increase capacity, but cautious because of the general world economic climate,” he adds.

DemcoTECH completed a contract for a new 40,000-tonne capacity, multi-discharge clinker silo working in joint venture with Kantey & Templer Engineers of South Africa. DemcoTECH was contracted as part of an expansion drive by NPC-Cimpor, a leading manufacturer and distributor of cement, concrete and
aggregate products to the hardware retail, ready-mix, concrete product and construction industries.

The expansion included a new, second cement kiln, for its Simuma Plant in Port Shepstone in South Africa’s KwaZulu-Natal Province. Cement kilns are used to manufacture an intermediate cement product known as clinker, the primary ingredient in cement. The second cement kiln required an additional silo for storage of the increased clinker production.

“The contract had a number of design and construction challenges, including the need to complete it within 15 months, the ability to handle hot clinker up to 205oC and to feed clinker to either the new or existing silo, alongside which it is positioned.

“In addition, the Simuma Cement Plant is located adjacent to the limestone source in the mountainous, environmentally sensitive Oribi Gorge area of KwaZulu-Natal and ensuring control of dust emissions from the plant are controlled well below regulatory requirements was an absolute priority,” says van de Vyver. “Dust extraction filters were included on the silo and at all the transfer points to ensure the dust emissions comply with the safety and health regulatory limits.”

Kantey & Templer was responsible for the civil and structural design, engineering and project execution of the silo — a 40,000-tonne free capacity, reinforced, pre-stressed structure with a 30m internal diameter and 55m height. The clinker silo was designed with two reclaiming tunnels and a precast concrete conical roof.

The silo is founded on a full raft foundation, 36m in diameter and 1.3m thick, which, in turn, is founded on an engineered fill layer, extending 4m below the natural ground level.

“DemcoTECH provided the materials handling expertise for the project, which included the mechanical and electrical design, engineering and project execution of the system,” notes van de Vyver. 

The silo receives clinker from the kiln, via a silo feed steel pan conveyor. DemcoTECH then supplied and installed an additional Aumund Pan conveyor feeding from the existing pan conveyor to the new silo. This modification included the design and replacement of the transfer chute. Two DemcoTECH-designed reclaim belts with heat resistant belting are in turn used to feed the existing plant or rail loading system. The silo discharges at 250tph (tonnes per hour) onto each of the two reclaim conveyor belts.

“The award of the contract for the Simuma plant was part of a good working relationship we have enjoyed over past years with NPC-Cimpor, which has ranged from project execution to studies such as a concept study for a new limestone handling and processing project.”

ADVANCED TECHNOLOGIES

With the poor flow characteristics of the raw materials handled at a cement plant, producers are always looking for new improved technologies that can cope with dusty, very abrasive materials that are also prone to build up in chutes and on conveyor belts, explains van de Vyver.

“Our range of specialist conveying technologies, which includes AeroConveyorsTM, pipe conveyors and pneumatic conveying systems fully satisfy this requirement. And, as maintaining a clean environment is a priority, all equipment we design and install complies with international environmental and safety standards.”

DemcoTECH Engineering supplied, in conjunction with Claudius Peters, a 150tph pneumatic transport system to convey cement from the kiln to multiple storage silos at a new milling plant at Nova Cimangola’s cement plant in Luanda, Angola.

The system has a conveying distance of 300m and, as a brownfield project, had to be designed to follow a tortuous route to fit into the existing plant and include a number of discharge points into the multiple silos. As an operating plant, the downtime needed to be minimized during tie-in so as not to negatively impact on production.

DemcoTECH was subcontracted for the upgrade to the plant and also to provide four travelling maintenance trolleys to NOVA Cimangola for the pipe conveyor at its Luanda plant. The trolleys were fully equipped with maintenance tools and maintenance power sockets and designed to negotiate an incline of up to 15°, which presented a number of challenges.

A DemcoTECH design, the trolleys were manufactured and pretested in South Africa at a 15° inclination, before being containerized for transport to site. The trolleys are self- propelled by an on-board generator and include hydraulically driven travel mechanisms for a high level of control. The trolleys feature a number of safety features, including being fully enclosed and equipped with emergency brake facilities and heavy duty traction control.

Specializing in pipe conveyors, DemcoTECH has supplied this technology to a number of cement producers, both in Africa and in India, as well as for other commodities.

The pipe conveyors comprise both fabric and steel cord belting, have up to 2,250tph conveying capacity and are up to 500mm in diameter. They can be engineered as two-way, multiple curve and distributed drive pipe conveyors. In addition, DemcoTECH pipe conveyors can be designed using a triangular tubular gantry fitted with a mobile maintenance trolley.

“Pipe conveyors are ideally suited to the cement industry as the material transported by a pipe conveyor is enclosed by the conveyor belt for most of its travel length. This obviates problems of material spillage on the carrying and return sides, belt training, limitations to the angle of incline and horizontal curves and the need for multiple transfer points, often associated with conventional conveyors,” says van de Vyver.

ABOUT DEMCOTECH

DemcoTECH is a leading specialist in the bulk materials handling field, offering its clients a range of services from conveyor design to turnkey niche process plants, from concept to full, turnkey project completion. DemcoTECH has carried out the design and engineering for large import/export port facilities, gold plants, diamond tailings disposal systems, manganese storage and export facilities, sampling plants and a wide range of other projects.

“Our services include concept design, feasibility studies, detail design, engineering, procurement, expediting, construction and commissioning. In addition to the cement sector, our clients come from a wide range of industries, including the power generation, mining, metallurgy and manufacturing industries, as well as port facilities,” states van de Vyver.

Materials handling products offered by DemcoTECH include troughed conveyors, pipe conveyors, air-assisted AeroConveyorsTM, rail-mounted slewing stackers, pivot-boom conveyors and mobile conveyors.These systems include all structural, mechanical, electrical and control systems.  
 
 
Siwertell receives a repeat order for road-mobile unloader in Kuwait  

Siwertell, part of Cargotec, will supply a second road-mobile unloader to Acico Construction Co in Kuwait. The company took delivery of its first mobile unit from Siwertell in July 2014, following earlier very positive experiences when operating Siwertell mobile unloaders.

“The growing numbers of satisfied customers placing repeat orders is a great confirmation of the high quality and efficiency of our unloading solutions,” says Jo¨rgen Ojeda, Director, Mobile Unloaders, Siwertell. “With its growing experience of operating and owning our mobile unloaders, Acico fully appreciates their flexibility and high capacity. Combined with their low operational and maintenance costs, these factors had a major impact on Acico’s decision to buy a second unloader.”

The trailer-based, diesel-powered, Siwertell 10000 S road mobile unloader will be used at Shuaiba Port in Kuwait to discharge cement at 300 tonnes per hour. It will be equipped with a double bellows system to allow continuous unloading operations, and a dust filter to minimize dust creation. Scheduled for delivery by the end of May 2015, the unit is under construction at Siwertell’s manufacturing premises in Bjuv, Sweden.

Siwertell mobile unloaders were originally designed for handling cement, and their reliable, eco-friendly and durable qualities make them the natural first choice for the job. As they do not need any local civil engineering works, they feature immediate availability on delivery. Furthermore, Siwertell can offer short lead times, so the period between placing an order and going operational can be remarkably short.

Acico Construction, part of Acico Industries Company, was founded in 1990. In 2012, it won the Arabian Business Magazine award for ‘Green Building Company of the Year’, highlighting the company’s aim for good environmental credentials.