It’s a surprising figure, however cement production is reckoned to emit 5 to 6 percent of total man made greenhouse gases, Some of the greenhouse emissions from conventional cement production come from using fossil fuels to heat up limestone to the high 1500degC, temperatures required by the process, so it is unsurprising that alternative fuelling methods are now being thoroughly exploited. The use of alternative fuels in European cement kilns is now estimated to be equivalent to 2.5 million tonnes of coal per year.
The use of alternative fuels is considered to represent the Best Available Techniques (BAT) for all cement manufacturers. Many UK cement producers have signed a climate change levy agreement with the UK government. The agreement sets a target of both klin fuel and electricity, which will result in a substantial reduction in carbon dioxide emissions.
Alternative fuels used in cement manufacturing have differing characteristics such as SRM (Secondary Raw Materials), RDF (Refuse Derived Fuel), SRF (Solid recovered fuel) and PSP (Pelletised/Processed Sewage Pellets) when compared to the more conventional fuels. Switching from conventional fuels to alternative fuels presents several challenges that must be addressed in order to achieve successful application. Poor heat distribution, unstable pre-calciner operation, blockages in the pre-heater cyclones, build-ups in the kiln riser ducts, higher SO2, NOX and CO2 emissions, dusty kilns and excessive wear in pipe work, valves, burners, chutes and cyclones are some of the major challenges.
The same problems arise in the increasing number of industries that are replacing fossil fuels with renewable materials or supplementing fuel streams with mixed waste and recyclate in order to achieve carbon offset. But managing biomass and mixed media can take its toll on processing equipment unless it has been designed or
adapted for handling products with varying characteristics that create excessive abrasion and corrosion.
Kingfisher Industrial is a world-recognised expert in the protection of plant and equipment for handling aggressive materials, such as mixed media fuels for cement plants, power generation, chemical processing and incineration.
As such Kingfisher can help cement plant operators ensure that their fuel handling equipment is able to withstand the rigours of conveying mixed media by offering a tailored solution to each situation to counter the detrimental effects of processing abrasive minerals and media The main technique used is to line handling equipment with an appropriate hardwearing lining system, matched to the materials being conveyed. For any given project, Kingfisher will assess the situation, recommend solutions based on the type of media mix design and manufacture plant for conveying, storing and processing the fuel, install and commission it. This will ensure that fuel handling equipment is reliable, wear and damage resistant over an extended working life (which is often measured in many years of service)
By implementing best engineering practise, Kingfisher says that key plant and equipment can operate on a continual basis and lead to increased efficiencies and profitability. The company has considerable expertise in combating wear and corrosion within cement and other heavy industrial plants and has frequently extended the service life of key processing equipment by utilising its range of protection systems.
Kingfisher works with a number of preferred materials suppliers to offer an unbiased approach to solving the problems experienced when handling bulk solid materials and allow it to offer the best solution or solutions for any given situation.
Despite manufacturers’ many claims to offer the ultimate material in the ‘fight against wear’, success levels can vary enormously, so there is a need to analysis each individual set of circumstances. Sometimes the wear-resistant properties of one material type may be in excess of requirements and conversely, those same properties may under-perform in a different application, putting the material’s
suitability in either case under question. Careful assessment is a key requirement for success.
Technically speaking three familiar material groups are most common for wear protection duties, ceramic, metallic and polymer.
Ceramics are available in their long-established cast form and as state of the art pressed products and are used in many, many situations: they range from high alumina, fused cast basalt, silicon carbide to fused corundum.
Metallic solutions are usually based on hardened versions of common metals and are suitable for a wide range of applications. They have been in use for many years and are much favoured by many users. Specialist metal alternatives are also available and can provide the optimum outcome to unusual situations, such as high chrome, ni – hard, manganese castings and chrome carbide overlay plate.
Polymers like rubber often work in a counter intuitive way, having the ability to absorb the shock of impact and dispel the damaging forces. Other polymers such as polyethylene, with its very low coefficient of friction, encourage the material to glide over it as opposed to scouring the surface thus, reducing the effects of friction or sliding induced abrasion. Polymers tend to be lightweight, flexible and relatively easy to apply.
The use of polymers to protect equipment where extreme impact prior to crushing is evident benefit from being lined with hard rubber liners and likewise the difficulties associated with the storage of coal and cement are eliminated due to the low coefficient of friction that polyethylene liners offer in assisting discharge. In all of these cases and in many more, the cement industry can achieve significant benefits when employing wear resistant linings and wear protection systems. New or existing equipment can be retrofitted with a protection system to add to its current asset value.
Kingfisher has wide expertise with all three material groups and carefully tailors solutions to each specific situation. Before making recommendations Kingfisher undertakes a full in-depth analysis of a plant’s operational criteria and identifies a system that is fit-for-purpose to meet the many requirements of the end user. Criteria
that are reviewed in the decision making process include the type of material being conveyed, size and shape, volume & velocity, operating temperature and of course the budget constraints versus the operating life cycle required.
Kingfisher has installed their wear resistant lining solutions within a number of plants that use the different types of alternative fuels. Referring to a project carried out at a cement plant situated in Derbyshire, the manufacturing plant have been working with the SRF since 2009. During the installation of the SRF system, Kingfisher were approached by a process engineering company to supply pipes lined with K-BAS Cast Basalt wear resistant lining systems. After a couple of months of operation the plant was advised to upgrade their conveying bends to K-ALOX Ceramic wear systems instead “due to the erosive nature of the material, the K-BAS lining system did not meet the life expectancy of the system” commented MD John Connolly, “as part of our after sales service our engineers identified the problem and advised the customer to upgrade the lining system to an alternative material type’’
Adding to the process Kingfisher has engineered bends with a removable wear back that is fitted with their very own Abralarm wear detection system. The system comprises of a low voltage electrical indicator that is integrated between the lining system and steel casing, when the lining system is breached it will sever the induction loop and send a signal through to the SCADA/PLC system located in the customers central room which enables the operation team to plan for replacements.
Kingfisher were also approached by the plant engineers to provide a suitable lining option for a Silo used within the SRF process, the problems encountered by the plant included 50-80mm bed of excessive material which was recovered at the bottom of the silo after every shutdown, usually the silo would be reasonably full hence the lining solution provided must be able to endure high impact without causing any issues. During the site visit carried out by Kingfisher’s Sales Manager he commented “the largest piece of material entering the silo was measured at 150 x 20 x 3mm thick. As material degrades in the silo, the moisture increases and the inside of the structure becomes saturated which in turn creates a dew point and excessive corrosion becomes a major problem if left untreated.
The solution suggested was Kingfishers polymer based epoxy resin spray application. The characteristics offer a tough, impermeable barrier suitable for steel and concrete surfaces. Providing outstanding resistance to most chemical agents, particularly strong acids (including 98% sulphuric acid) alkaline, and many solvents. The low odour system forms a very hard and excellent gloss finish being evident on the surface of the plant & equipment.
The materials that make up typical mixed media and biomass fuels can create many problems due to the size, shape, density and tonnages that are handled. Demonstrated by another international manufacturer within the cement industry, they have used alternative fuels since 1992 by successfully implementing the use, of recycled tyres, meat and bone meal (MBM) and Solid recovered Fuels (SRF), Kingfisher have supplied pipe work for the existing pilot plant, the pipe work supplied was lined with the K-BAS Cast basalt lining systems.
Kingfisher have also supplied similar wear resistant pipe work systems used at one of largest sludge drying centres in Europe, The plant processes sludge from hundreds of wastewater treatment plants into processed sludge pellets (PSP).
A Kingfisher solution will allow for this and will also optimise plant layout for clear flow lines without bottlenecks or other points of weakness. Applications such as the installation of low friction linings systems within the fuel reception hoppers can also eliminate the need for mechanical aids or personnel having to gain access in order to clear blockages. A Kingfisher built or adapted system will generally need far less maintenance, as the protective systems reduce the need to continually undertake repair work.
As well as handling the fuel, the Kingfisher technologies can also be applied to the actual process of cement manufacture, all the way from the quarried limestone to the bagged despatch point. This involves a multitude of activities with each operation depending on the success of the previous stage. Kingfisher can solve the problems experienced with mineral excavation, blending of clay and chalk, firing, cooling and storage of clinker and finally milling and conveying of cement. Equipment such as front loading buckets, crushing equipment and reception hoppers have seen
extended service life through the use of protection systems such as chromium carbide clad plate or manganese steel castings.
Plant and equipment that can achieve continual operation when handling aggressive bulk solids in the harsh environmental conditions of cement production is of the utmost importance if efficient, lean production is to be achieved. Correct application of protection systems within process critical plant and equipment can deliver substantial savings in downtime and maintenance costs when engineered correctly, however investment in the wrong system being used in the wrong application can lead to increased costs all round!
ALTERNATIVE FUELS EXPLAINED
Bio fuels are based on organic materials (plant or animal) and include organic waste, residues from agriculture and energy crops, meat and bone meal, methane from animal excrement or produced by bacterial action, ethanol and biodiesel.
Solid bio fuels (usually referred to as biomass) include plant tissues, such as wood, charcoal and yarns; agricultural by-products such as coffee husks, straw, sugar cane and its leaves, rapeseed stems, palm nut shells, rice husks, etc, etc. There are other non-agricultural biomass elements, such as animal fat, sewage, waste meats and bones, food scraps and domestic or industrial biodegradable wastes. In all cases, these materials are primarily composed of carbon based organic matter, which releases energy through combustion.
Refuse Derived Fuel (RDF) is a product of municipal waste/recycling programmes
It is available in increasingly vast quantities from local councils and authorities and from processors and is likely to be used more and more in the future.
Secondary Raw Materials (SRM) is a by-product of municipal recycling. SRM consists of materials such as paper, glass, metals and some plastics that have been manufactured, used then discarded and are to be used again.
Solid Recovered Fuel (SRF) is produced by sorting, shredding and drying mixtures of municipal solid waste (MSW) and other low grade materials. Strict specifications are specified so that a consistent quality of fuel is maintained.
Processed Sewage Pellets (PSP) are made by heat treating the sludge remaining after sewage processing. The technique was originally used to produce agricultural fertiliser or to ensure the sludge was acceptable for landfill. Its use as fuel is increasingly common and expected to continue growing
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