Hurll Nu-Way offers ‘continuous anaerobic digester gas mixing systems’ manufactured in the UK by Utile Engineering.
These systems utilise sliding vane gas compressor technology, which is proven to be the most efficient and cost effective method to mix, absorbing approximately one third of the power required for ‘pump’ mixing.
Gas mixing requires a reliable gas compressor to work in conjunction with the most efficient and effective mixing systems. Overseas operators have recognised that continuous unconfined gas mixing using very efficient sliding vane gas compressors provides the best results for both reliability and whole life cost.
Power usage is also three times more in slurry (pump) mixing than in a sliding vane machine for the same duty point. The introduction of a small, metered amount of oil to the gas compressors may therefore be seen to be a small price to pay for longer life, reduced maintenance, lower power consumption and noise levels, and less downtime. All of these factors contribute to considerably lower whole lifecycle costs of a sliding vane mixing system.
With the increasing uptake of co-generation, the reduced power absorbed by a sliding vane machine results in huge increases in available power that can be exported from the site to provide a significant income. The operator benefits from having a very reliable system at low capital cost with excellent power consumption, thus reducing carbon footprint.
It is logical to select robust and reliable equipment that requires the least amount of maintenance. The sliding vane gas compressor uses a simple, well proven design to compress the gas inside the heavy duty ductile iron cylinder resulting in a quiet machine that delivers pulsation-free gas.
In contrast, a pump-type unit that relies on high velocity sludge flow through feed pipe work to mix accurately can result in bore erosion. Coupled with nozzle wear inside the tank, it can mean high maintenance and additional expenses. The downtime comes with a reduction in overall mixing efficiency, and as a consequence, results in lower gas production.
Sludge pump seal failures could result in sludge on the floor, creating health and safety issues for operators to deal with in addition to the obvious maintenance aspects. Sludge pumps are also intolerant and susceptible to varying sludge depth, and also require a stable head with fixed sludge depth to ensure suitable mixing.
Maintenance routines for the Utile sliding vane gas compressors on site typically involve periodical topping up of the oil tank along with annual checking of blades for wear, which can be carried out without having to dismantle the machine.
When investing in equipment, it is therefore important to consider not only the short term capital costs, but both the direct and indirect whole life costs.