Water and Effluent Treatment Magazine
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16 | INNOVATION 2018 T he Water 2020 report published by the regulator Ofwat encour- ages sludge trading markets between operators in order to move sludge from a com- pany where it is expensive to treat, to one that is cheaper. Ofwat modelling suggests that if its proposed changes are implemented, around 30 per cent of all sludge could move between different water companies. Wherever it ends up, this sludge will need to be pro- cessed, increasing the need to convey dewatered sludge from reception bunkers to, for example a thermal processing energy plant. However, a long pipeline does not have to be a barrier to efficient sludge transfer. SEEPEX have devel- oped a new way of handling dewatered sludge and other highly viscous products - Smart Air Injection (SAI). SAI combines the advantages of two conveying technologies to transport dewatered sludge over long distances in an energy-efficient manner. The future of sludge transfer SAI conveys dewatered sludge over distances of up to 1,000 metres, with a low cost of ownership when combined investment and running costs are considered. Until now, long distance transfer of dewatered sludge has been carried out by belt and screw conveyors and bucket elevators, which require a lot of costly main- tenance, especially when working at heights, if silos are filled. In addition, these systems are frequently open to the environment, resulting in unpleasant odours and rehydration by rainwater. An alternative closed piping can be used in conjunction with multi-stage progres- sive cavity (PC) pumps and piston pumps, which are suitable for highly viscous media and high pressures. However, because of the high discharge pressures, these require comparatively high investment costs for higher pressure-rated pipework and valves (in some cases more than 100 bar) and have higher energy costs. Plant-specific solution SEEPEX Smart Air Injec- tion uses a combination of PC pump technology and dense-phase pneumatic conveying. A solid 'plug' of dewatered sludge is formed by an open hopper pump which is then split into smaller 'plugs' by compressed air in the discharge pipework and transported onwards by pulsed compressed air injec- tion. The system is pressure- controlled via an algorithm optimised for the application so that the discharge pressure remains below 4 bar. The pneumatically-transported sludge plug is lubricated with boundary layer liquid, for example dilute polymer solution. This reduces friction in the pipework and improves the energy efficiency of the system as a whole. Adjusting system param- eters, such as polymer and air volumes, at the location makes it possible to set a plant-specific, energy-opti- mised operating point. The reduction in friction losses and the discharge pressure requirements mean that pumps fitted with Smart Conveying Technology (SCT) can be used for long distance, high viscosity transfer duties. Pump maintenance time is minimal as pipework removal is not required for mainte- nance. The lower discharge pressure additionally ensures an increased service life for the components as does the integral process monitoring integrated into existing auto- mation and control systems via conventional interfaces. All functional components, sensors and actuators are part of the scope of supply, and are integrated into the control so'ware SAI, which is INNOVATION 2018 optimised for the respective application. This alternative to con- ventional means of handling dewatered sludge has already been installed at a number of plants throughout Europe, and has generated a rapid re- turn on investment. SAI is be- ing integrated into one of the UK's largest water companies later this year, as an energy- efficient, high-performance alternative to conventional sludge handling systems. The customised pumping solution is being engineered to fulfill the plant's specific require- ments and to be configured at the location for optimum energy consumption. SEEPEX, 3 Armtech Row, Houndstone Business Park, Yeovil, Somerset BA22 8RW Contact: Lesley Eaton Tel: 01935 472376 Email: sales.uk@seepex.com Website: www.seepex.com Overcoming the issues of transporting dewatered sludge The SEEPEX Smart Air Injection system