The last few years have seen a drive to build more biomass plants and to develop fuel from organic and sustainable materials, for instance converting wood chippings and food and agricultural waste into ‘green’ energy. This renewable energy solution is heavily dependent on the supply of high quality water and has the potential to deliver significant carbon savings. Burning wood or other organic matter releases carbon, but this is offset by the carbon dioxide absorbed in the original growth of these combustible materials. Together with combined heat and power (CHP) technology, biofuels provide a proven, cost-effective and environmentally-friendly means of meeting future energy needs.
Biomass plants not only contribute to the circular economy, but also provide commercial opportunities for their owners and operators. Typically, a “gate” fee is charged for incoming biomass, which is then burnt to generate electricity for use on site or to return to the electric grid. Like the electricity produced from biomass, heat from a CHP plant can be used to make the site self-sufficient, or can be supplied to the community.
Demanding water specifications
In a biomass plant, the heat generated from burning is used to convert water into steam that then powers a turbine, which in turn is connected to a generator. Very high quality water with an extremely low silica specification is required for this to prevent glass pellets forming on the turbine, which can potentially throw it dangerously off balance. Skid-mounted water pretreatment systems have been very successful in this regard, with a typical platform incorporating a softener, a carbon filter and a reverse osmosis (RO) unit, removing over 99 percent of impurities. A final polishing step using continuous electrodeionisation (CEDI) brings the water to the required specification.
One system, many benefits
Skid-mounted systems offer further benefits beyond water purification. On a busy site with many contractors, the time taken to install a water purification system needs to be kept to a minimum. Skid-mounted systems can be pre-tested and commissioned in just a few days rather than weeks, before being delivered to site. In addition, RO-CEDI technology means that you can avoid the hazardous substances used by older chemical deionisation systems. Not only is this better from a health and safety perspective but the ongoing operating cost of buying the chemicals is reduced.
Mobile solution for fast commissioning
Mobile water treatment plants also have a role in complementing the biomass water purification systems, offering temporary additional capacity to speed up the commissioning process. A mobile plant, comprising deionisation and RO units installed in a trailer, can be transported to the site and used to flush the newly installed biomass system prior to its initial operation, ensuring that the drum and pipework are clean. Typically, biomass plants are relatively small, requiring a system capable of generating 5-10 m3 of purified water per hour. However, the plants usually feature a large drum, which takes a long time to fill at this rate of water purification. Here too, mobile units are beneficial, enabling rapid filling of the drum at the commissioning stage. A final, and hopefully unnecessary, application for the mobile units is as an emergency backup. If the unthinkable were to happen, a mobile unit can be rapidly installed to ensure water purification continues during the maintenance period.