Covering up? enclosed storage solutions for the bulk industry

Domes and dry bulk

Geometrica works with plants and facilities at all altitudes to achieve the highest calibre of coordination between shipping and dry cargo handling and storage, writes Melanie Saxton of Geometrica.

• internal cladding especially designed to minimize internal dust and protect structures from corrosive or combustible stockpiles; and
• external cladding that covers stockpiles and spares the ecosystem from emissions, runoff, and air pollutants. Neither brutal saltwater environments nor heavy snow loads are a match for Geometrica’s Freedomes®, which can span up to a remarkable 300 metres without internal columns or barriers.

Other challenging environments, such as those with typhoon- force wind loads or extremely uneven topography, also require careful design and remarkable structural strength and flexibility. Options include circular, conical, longitudinal and freestyle storage solutions. These structures, plus cylinders and geodesic domes, are ideal covers for stockpiles. The goal is to turn an often dusty or combustible stockyard into an environmentally sustainable system regardless of terrain or climate. Lightweight yet incredibly strong, Freedomes are prefabricated, containerized and shipped anywhere in the world. Regardless of geography, construction may proceed before, during or after material handling equipment is installed. Frequently, these all-terrain domes are built over existing live material stockpiles with minimal or no downtime.

Following are examples of durable storage structures in extreme locations around the world.

TAI POWER SILOS

Four beautiful examples of corrosion-resistant infrastructure are the immense coal storage silos at Hsin-Ta Fossil Power Station in Kaohsiung Hsien,Taiwan (see picture above). Gibsin Engineers specified aluminium cladding and galvanized steel for the structure. Due to Geometrica’s prefabrication and barcoding system of round tubular members, the bid was competitively priced. A team consisting of Geometrica,Triumstar International Co. Ltd. and Chien Yang Construction and Engineering Co. Ltd. (both from Taipei), was awarded the job.

The long span solution consisted of four 126m diameter concrete wall and metal dome covers built in a marine environment over an internal automated stacker/reclaimer system. Each unit would store 180,000 tonnes of coal in a live pile for a total of 720,000 tonnes. Geometrica handled design, manufacturing and technical assistance during installation and construction of the domes on site. All units were assembled using the ‘perimeter-in’ method of construction: the first nodes and tubes were set on the supporting concrete wall. Each of three to five tubes were joined to one node forming a ‘spider’. Each spider was then raised to the work front and tapped into place, creating rings around the base that grew one on top of the other until the whole skeleton was formed. Co-ordination with other trades was easy, as the area under the dome was free of obstacles. Neither scaffolding nor other special equipment were required, and the project was completed with a perfect safety record.

Turnover of the domes and testing of the first silo started approximately 16 months after start of construction. Today the Taiwan Power Company produces electric power in a clean and safe environment for surrounding communities.

EL BROCAL

The new storage structure was to be built within a constrained space, which meant that copper ore must be delivered via a tripper conveyor suspended along the length of the building’s apex. Therefore, the building’s shape had to support wind, live and material loads efficiently. It also needed a structure strong enough to support the weight of the conveyor equipment, as well as the vibrations and impacts created by the conveyed copper ore. Furthermore, even in the constrained space, El Brocal management mandated that construction take place with minimal interruption to its nearby mining facilities.

UREA STORAGE PORTSIDE

In another quayside project, Grupo CICE, a diversified logistics and transportation company, called Geometrica about its need to store urea as it arrived at the port of Veracruz (see picture below). When exposed to humidity, this extremely corrosive material attacks both aluminium and galvanized steel. Further, the coast of the Gulf of Mexico is one of the most corrosive atmospheres anywhere on earth, as industrial and marine exposures combine to torture metal. Up to 15,000 tonnes of urea needed to be stored while waiting for transport, and CICE needed a building that would withstand the corrosive attacks from inside and outside the building.

Geometrica’s solution for this challenging problem was a unique building of 52m internal clearance width, 18m clear height at the centre, and 120m length. The building’s lightweight skeleton is made of high- strength aluminium alloy and left exposed. But since urea can attack aluminium, the structure was protected by applying FRP cladding to its underside. The combination is perfect, with each material exposed only to conditions they resist: the aluminium structure is resistant to the corrosive atmosphere, and the polymer cladding resists urea attack, and prevents it from attacking the structure.

Construction took place quickly. Half-arches were assembled on the ground and lifted onto place with two light cranes. The whole construction process took four months. CICE’s general manager on site, Cesar Zamora, said of Geometrica “Excellent quality, service, and products. One hundred per cent recommendable.”

DUST DEFEATED IN ESCONDIDA

Freedomes may also be used to close-off existing, open ended storage structures in the most efficient manner, as done at the Escondida mine in Chile. Geometrica designed and manufactured the end for a 100m span vault built several years earlier. The vault had open ends, through which dust continued to escape until the 99m span Geometrica Freedome was installed (see picture above).

Geometrica has built some of the largest, highest and longest industrial domes in the world. The question is, “What can Geometrica do for you?”

INTRODUCTION

The environmental debates that have raged since the Rio and Copenhagen conferences show clearly that environmental laws must be reinforced — and further laws created — to protect the environment.

In many countries, there is a glaring absence of rules about the storage of materials, and people can just store what they want, where they want.

Domes help to protect the environment because they are hermetically sealed, insulated and waterproof (Figure 1). Products — such as fertilizers, cement, alumina and fly ash — can be stored easily, protecting the environment, while other materials like sugar and cereals are protected against contamination during their storage time.

ADVANTAGES

Cost effectiveness

Domes remain among the most cost-effective storage infrastructures, and represent one of the more competitive solutions for the storage of large volumes of bulk material. Operation, maintenance, conservation and energy costs are kept to a strict minimum.

Rapidity in construction

Once the airform is inflated, all the work is carried out inside the dome. Consequently, the stored products are unaffected by exterior environmental factors such as rain, wind, and daylight.

Optimization of the land

Domes minimize floor space while optimizing the volume. This means lower cost per tonne of storage.

Reclaiming

Insulation

Domes are an ideal solution for the storage of bulk materials that are sensitive to temperature changes and humidity. The application of Vethane foam on the inner surface of the airform gives the dome the quality of being equivalent to a controlled atmosphere chamber. Condensation is practically eliminated inside the dome since the insulation of the dome will conserve a stable ambient temperature.The whole structure itself is perfectly adapted to the techniques of prolonged conservation of perishable products.

Waterproofing

A PVC membrane forms the exterior layer of PIRS’ domes and acts as the initial framework for the application of Vethane foam and shotcrete. Opposite to what is usually done in traditional construction, waterproofing is controlled at the very beginning of the process, once the airform is inflated. This membrane, added to the Vethane foam, ensures that water will never leak inside the dome and spoil the product.

Domes are an ideal solution for the storage of sensitive bulk materials.

CONCLUSION

PIRS concrete domes have proven their efficiency in protecting the environment and products against temperature and humidity. The filling and reclaiming systems, including operation and maintenance, are usually cheaper for domes than many other solutions. There are other factors that must be considered: the cost of the land, especially in a port (Figure 1 — see ‘PIRS SAS builds fertilizer terminal in the Port of Riga in Latvia’ on p84 of the November 2013 issue of Dry Cargo International) knowing that the domes will use less space than flat storage, for example. The time of execution can save financial costs and the operation can start earlier.

Domes are an innovative solution that are capable of bringing advantages in terms of product conservation, insulation, operation and maintenance costs. As a storage solution, they can help ensure maximum waterproofing and are a strong and durable solution for storage.

Safe silo storage of coal

Chris Geijs and Jaap P.J. Ruijgrok of ESI Eurosilo BV, the Netherlands, review fire protection in coal silos with the Eurosilo® system.

INTRODUCTION

EUROSILO® SYSTEM WORKING PRINCIPLE

This process continues for a complete layer of 360°. The winch system (located at the overhead bridge) hoists the auger frame one predetermined step after completing a full rotation. This cycle can be repeated until the silo is completely filled with bulk material.

During the discharge process, vibration devices, called Uncoalers, initiate a core flow in the middle of the silo to extract the bulk material. The overhead bridge and suspended auger frame rotate in a continuous counterclockwise direction, while one of the augers digs into the bulk material and transports the product towards the core flow in the centre of the silo. After a full rotation, the auger frame is lowered one step.This process continues until the silo is completely emptied. The Eurosilo® system also has the flexibility of simultaneous filling and reclaiming.

SELF-HEATING OF COAL DURING STORAGE

Self-heating of materials means the onset of an exothermic chemical reaction and a subsequent temperature rise within the combustible material, without the action of an additional ignition source. Generally, self-heating is supposed to occur when the rate of heat production exceeds the heat loss. When exposed to the atmosphere, nearly all types of coal show signs of self- heating, which results in a decrease of calorific value. Spontaneous combustion ultimately occurs when the heat build- up due to the right amount of oxygen is present over a longer period of time.

Enclosed storage in a silo protects the coal from rain. On top of that, spraying of the exposed surface to reduce dust emission is not required, thereby further reducing the percolation of water. The controlled method of stacking layers with the auger system ensures a minimum of segregation compared to the conventional chevron stacking method, which is used for most storage configurations. Layer stacking also establishes an optimal and evenly distributed compression of the stored bulk material.

EUROSILO® FIRE PREVENTION SYSTEMS

All the ingoing bulk material during filling is monitored temperature wise. Bulk material in excess of 55 C° (104 °F) is rejected, according to IMSBC-code [3].

Stated CO values refer to the IMSBC code [3]. All the ingoing bulk material during filling is monitored temperature wise. According to IMSBC, bulk material below 55°C can be stored in the silo.The operator gets an alarm for bulk material in excess of this temperature, resulting in intensified monitoring. When the temperature exceeds 70°C, the arriving coal shouldn’t be stored in the silo.

EUROSILO® FIRE SUPPRESSION SYSTEMS

All coal silos are equipped with a Nitrogen-purging system, enabling operators to purge the whole, or just a section of the silo, thus enabling longer trouble-free storage periods. The piping for this system is embedded in a layer of gravel at the bottom of the silo and covers the whole surface.

At upper bridge level, gel sprayers are present to cover specific parts of the coal surface with a layer of FIRESORB® gel [5] in case of a self-heating emergency. These sprayers are fed by a gel station, located in the roof gantry. The gel prevents the coal from having contact with the air and cools the coal down as well.

A spraying system is installed above the heat resistant conveyor belt in the basement of the silo to cool down heated coal.

Raised CO-values were found in one of the domes, caused by self-heating [6]. Further investigation showed increased temperatures up to 70°C for various locations in the stored coal. As a result, around 50,000 tonnes of coal were carried towards the Wedel power plant. It would have been better to deal with the cause of the problem in the first place, instead of having to struggle with the consequences.

An ounce of prevention is worth a pound of cure. Inherent to circular storage is the large exposed area and the impossibility to do continuous CO-monitoring of the entire surface. Subsequently, hot spots will not be detected in an early stage and drastic measures will be required to solve the problem. On top of this, nitrogen purging is not a possibility for this type of storage configuration, leaving carrying away of all the stored bulk material as the only viable solution.

DISCUSSION

Chris Geijs (MSc Eng.) R&D manager and Jaap Ruijgrok (MSc Eng.) Managing Director of ESI Eurosilo B.V.

REFERENCES

[1] BAM Report on the prediction of the hazard of self-ignition in a storage silo for black coal Reference Number : II.2-329/06, April 2006

[3] IMSBC-code, International Maritime Solid Bulk Cargoes code section 4 (fire protection)

[6] Moorburg storage dome fire - http://www.nonstopnews.de/ meldung/17634

A manufacturer of relocatable engineered fabric structures is leading the way in the space race when it comes to providing storage solutions to the ports and marine sectors.

Rubb was the first port of call when Sunderland City Council required a new cargo facility at Hendon Docks in the UK. A versatile storage area was needed to help continue the development of the Port of Sunderland’s cargo handling facilities. In conjunction with SGW Construction, Rubb erected a 24m span × 65m long BVE cargo handling and storage facility with 7.65m sidewalls. The design and quality of the structure provided a safe and pleasant cargo storage solution. Rubb’s innovative customized structures ensure safe and secure access to the storage area, while the translucent roof provides a natural source of light. The internal clear-span steel framework allows the maximum use of available storage space.

Rubb also helped a port building project grow at the Port of Belfast. Rubb began working with Belfast Harbour Commissioners back in 2001 to ensure that their ever changing and ever expanding storage requirements were met as use of the port developed. The first Belfast Harbour warehouse storage facility was erected in 2001 at the head of the dockside area. It measures 24m span × 45m. In 2005 an additional building measuring 24m span × 65m long was erected directly adjacent to the existing harbour structure. In 2003 a much larger harbour storage building measuring 45m span × 175m was installed at a different location on the dockside and in 2004 this was extended to 217.5m in length. In 2005 the Rubb design team was given a brief to erect the largest possible building on the remaining land on this site. Careful consideration had to be given to the design because of restrictions created by the nearby dockside traffic. However, a 32m span × 60m harbour storage facility was installed, maximizing all possible space available, taking the storage area constructed by Rubb to a massive 14,347m2.

Meanwhile the Port of Workington offers high-quality storage facilities in the form of two relocatable Rubb constructed ports buildings. The ports structures measure 25m span × 32m in length and 25m span × 61m in length. These port facilities provide storage space for animal feed and protection from the elements and light. The design features a split storage capability. As this part of the west coast of England is susceptible to severe winds and rain, the storage systems were constructed on top of 4m retaining walls. The walls consist of a steel support structure complete with pre-stressed concrete infill panels, which allow for quick and easy construction. This method provides a fully sealed facility to prevent water ingress and also allows for internal retaining walls to be built for different storage needs. The client required a dark covered port storage facility as animal feed needs to be protected from light, however the translucent PVC material used on other Rubb ports projects provides a brighter working environment without the need for windows.

Rubb Buildings Ltd was also tasked with designing, manufacturing and erecting two crane liftable buildings to cover offshore pile clusters in a marine environment. The two marine manufacturing covers from Rubb’s new BLE series for Harland and Wolff feature spans of 30m and each measure 35m in length. To increase the overall internal apex height of the manufacturing bays to 20.2m, H&W asked Rubb to use a 7.3m high wall constructed out of 40ft containers as the building’s foundation. A custom designed supporting frame was created to hold the containers together and act as the fixing base for the Rubb BLE structures.

The buildings are designed with reinforced base beams and anchor brackets so they can be easily lifted from their container foundations and moved to one side. This allows the client to then crane lift materials into the space within the foundation frames for various operations. The building roof is replaced to protect employees and materials from the elements. Each gable end of both paint and blast facilities includes a pedestrian door and a 4m x 4m roller shutter door for equipment access.

Ten advantages of selecting Rubb structures 

• all Rubb products are suitable for ports/logistics/warehousing type applications. The flexibility of a Rubb structure means it can be used to house a wide variety of goods;
• Rubb’s port storage solutions offer a number of advantages to our clients. Its climate controlled warehouses provide dehumidified storage environments, while our bulk storage facilities are ideally suited for storage of materials under the strenuous conditions of a marine environment; 
• Rubb storage buildings offer marine terminals a solution that allows for maximum flexibility with respect to multiple handling methods and configurations; 
• relocating and re-using these buildings to suit the changing needs of a busy port is easy and cost effective; 
• additional buildings can be added as required;
• the PVC cladding will not corrode in a marine environment and allows the structure to accept differential settlement without the need for expensive pile foundations. These same features give Rubb an advantage when it comes to preventing leaky roofs;
• Rubb structures provide large column free spaces, illuminated by natural light through a translucent roof. This provides a safer and more cost effective working environment than other traditional warehouse buildings;
• Rubb buildings can be designed, delivered and erected within eight weeks;
• these semi-permanent structures are designed to stand for as long as the client requires. All steel used in a Rubb building is hot dip galvanized to strengthen the frame and provide a durable maintenance free facility. The high quality PVC coated fabric cladding has been proven to last in excess of 30 years;
• Rubb’s unique custom solutions enable it to handle all types of projects, large and small, from designing, manufacturing and constructing large new plants to extending existing facilities.

Rubb Buildings Ltd was established in 1977 and is based in Gateshead, Tyne and Wear. The Rubb Group also has office and manufacturing facilities in Norway and the USA.

The project began when the company Hormigones Domingo Giménez decided that it needed to get maximum processing efficiency at its plant in the Port of Motril in Granada, Spain, writes Eduardo Heras Villoldo of Claudius Peters Ibérica, S.A.. This rectangular-shaped plant stores cement that is brought into the port by ship.

Claudius Peters Ibérica designed an optimum solution — flat silos. These silos had to meet two pre-conditions: they had to fit the rectangular surface, and meet the height limit of approximately 12m.

SILOS

The three silos measure 20m × 20m each, with a height of 12m and a total capacity of approximately 3 × 5,000 tonnes.

In traditional cement silos, there is always a significant loss of height, due to the need to place trucks below the silo for loading. One of the main advantages of this new silo design is that it uses the height from the ground level to store material, which leads to a significant gain in the silo capacity and the possibility of lower height in silos in places where needed to meet regulations.

SHIP UNLOADING

FEEDING THE SILOS

The cement is carried by tank trucks and, with their own compressors, is pneumatically conveyed to four inlet ducts for each silo that homogeneously spread the cement that is to be stored.

Another proposal, which was not pursued, was transporting the cement to the silos pneumatically, using a Claudius Peters pump and compressor.

EQUIPMENT IN THE SILO ROOF

In the roof of each silo, there is: v a filter bunker, for dedusting the air from the feeding system

FLUIDIZATION

Each silo is divided into four quadrants. Each of these has three fluidization sectors, that are further divided into subsectors. During normal operation these are fluidized via a programme in automatic cycles and by rotary blowers during residual discharge.

SILO EMPTYING AND TRUCK LOADING

Each silo is emptied radially, towards the centre, using four outputs through 90°, positioned in a 3.3m × 3.3m chimney in the centre of each silo.

Trucks are loaded automatically with the required weight. The loading speed is 250–300tph, and does not generate any dust. The system allows for the simultaneous feeding of the silo from 12 trucks, and at the same time is able to load three trucks from the silo. The silos began operation in August 2008, once all commissioning was complete and the performance guarantees were achieved to the full satisfaction of the customer. At that time, it was a new design for the storage and emptying of silos for this type of product.