[Gasification] Characterization of waste water from biomass gasification equipment: A case-study from Cambodia
linvent at aol.com
linvent at aol.com
Mon Jan 4 12:10:18 CST 2016
The water handling is an environmental issue that cannot be ignored. One group recommends "drying" the amount produced, but the volatiles are quite nasty and will cause illness at least. Any biological system will be slow and take up a large area, the contaminants are, like creosoted wood, anti-biotic so that any microbial activity is severely limited in it's ability to reduce the organics. Cancer is promoted from exposure to the contaminants, as with virtually any product of combustion, are not healthy.
Many of the gasifiers attempt to reduce the water production by allowing the gas to go into the prime mover at higher temperature, but at these temperatures, the organics and acids in the gas will shorten the lifetime of the engine and it's output from lower heating value in the cylinder, and lord only knows what the emissions are from combusting these compounds, and if he finds out, new regulations will abound.
Over the years we have tried a variety of methods to break the contaminants down and somewhat through accident happened onto one process that can take the coffee or dark tea looking water and make it crystal clear in one step, and can easily be reused for a long period of time. The removed components are neutralized using a mild chemical and there is essentially no residue from this reaction. Other processes are used to pre-treat the water stream that also do the same but with lesser effect to reduce the load on the system.
Going from that stage to dischargeable, boiler feed grade, or potable water uses conventional systems that are relatively inexpensive, small footprint, and easy to maintain.
These systems are standard on our gasifiers as not having them would prohibit any reasonable cost installation in the US and other jurisdictions will only take time to force the abandonment of other less effective systems.
The application of this technology will be shown in on-site medical waste projects, a 200 ton/day MSW to power plant under development on the East Coast, European interests and other applications.
Leland T. "Tom" Taylor
From: Tom Miles <tmiles at trmiles.com>
To: gasifiers <gasifiers at bioenergylists.org>; biochar <biochar at yahoogroups.com>
Sent: Mon, Jan 4, 2016 8:33 am
Subject: [Gasification] Characterization of waste water from biomass gasification equipment: A case-study from Cambodia
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?
T R Miles Technical Consultants Inc
Portland, OR 97225
tmiles at 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
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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