Since 2005 hundreds of small scale gasifiers have been installed in Myanmar, Cambodia and other South East Asian countries to offset high cost diesel to generate shaft and electric power in rice mills and palm factories. They are often in the 100+kW scale. Initially they were dual fueled with diesel but increasingly they are 100% producer gas. Ankur Scientific introduced a dry cleaning system in 2009 but in most cases the gasifiers use water scrubbers and the waste water and sludge is discharged into ponds without remediation. Simon Shackley and others have published a thorough characterization of waster waters from several gasifiers.
Crop residues are best gasified at low temperatures. Low temperatures generate tars. Scrubbers are the lowest cost cleaning technique. Water strips toxic chemicals from the gas which become carried into the environment with water and sludge. Gasifier char is very useful. Sludge and black water are dangerous. The remediation of gasifier wastewater is a challenge for us. As we look forward to installing small scale gasifiers around the world we need to solve this problem . What are your solutions for filtering and remediating gasifier scrubber water? One solution might be running continuous blowdown though a vegetated biological filter where the biochar is used as part of the media. What have you tried? Tom T R Miles Technical Consultants Inc Portland, OR 97225 [email protected] <mailto:[email protected]> www.trmiles.com <http://www.trmiles.com> Characterisation of waste water from biomass gasification equipment: A case-study from Cambodia Article in World Review of Science Technology and Sustainable Development 12(2):126-151 · December 2015 DOI: 10.1504/WRSTSD.2015.073829 Abstract The gasification of rice husks for small-scale power generation in rice mills and other small factories in Cambodia has spread rapidly in the past decade and has a favourable investment payback period where the facility is off-grid. The technology is widely regarded as a sustainable, low-carbon power option. However, installed gasification technologies produce a black waste water which is frequently disposed of into the local environment without any treatment. An analysis was undertaken to identify and measure the key potential contaminants and compare concentrations in the water and sediment with regulatory thresholds established in Cambodia and within other jurisdictions. It was found that concentrations of organic contaminants such as phenols and benzene-type molecules (BETX) (water and sediment) and polycyclic aromatic hydrocarbons (PAHs) (sediment), as well as macro water quality indicators, were far higher than regulatory thresholds prescribe, posing threats to sensitive aquatic ecosystems into which such waste is introduced.
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