[Gasification] Characterization of waste water from biomass gasification equipment: A case-study from Cambodia

Peter Davies idgasifier at gmail.com
Mon Jan 4 20:28:19 CST 2016

Dear Tom,

The end of 2015 has been very busy for us, and the start of 2016 looks 
even busier. Essentially we have successfully proven our gasifier 
systems with high ash, pelleted ag-residues in a high temperature, low 
tar gasifier scenario with simple dry scrubbing. Even when slightly over 
aspirated with some residual oxygen coming through the tars were limited 
to low viscosity condensates (and very little of these), though the gas 
quality varied slightly with the appearance of some C2-C8 hydrocarbons 
(nothing higher though, within detectable limits of the GC system used 
by the lab). We also now have one of the leading European CHP providers 
sign off on our gas quality for use in their IC engine systems, so 
expect to be able to supply complete turnkey plants shortly which have a 
global support network.

Yes it does require a pelleting step at this stage, but we are working 
with a couple of pellet equipment manufacturers for a lower cost, 
gasifier optimised pellet which will be substantially cheaper and lower 
maintenance than conventional wood pellet plants used for the combustion 
industry. Accompanying innovative financing for village scale 
densification systems is also now well advanced.

So we don't agree that water scrubbing is either necessary or where 
gasifiers will be in the future. However if you only have old gasifier 
tech to work with then you can try torrefied sawdust filters to 
recirculate your scrubber water through, our early testing found these 
very effective till we fixed the hearth core in the gasifier design so 
they were not needed.

New Years Cheers,
ID Gasifiers Pty Ltd

On 5/01/2016 2:31 AM, Tom Miles wrote:
> 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
> tmiles at trmiles.com <mailto:tmiles at trmiles.com>
> 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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Peter Davies
Managing Director
ID Gasifiers Pty Ltd
Delegate River, Victoria
Ph: 0402 845 295

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