Californian Shasta Class 2
Having returned from
a visit to our gasification development project in California at CalForest
Forestry Nursery, some may find it interesting to see how the " Shasta
Class 1" (this is the new designated name for this series of linear hearth
gasifiers) gasifier project has progressed since my last visit 18 months
ago. With the new "Shasta 2" now finally in existence, the alternative of the
blown mode of gasification will be investigated. The photos can be seen on the
Fluidyne Archive www.fluidynenz.250x.
Shasta 1 was put to work these last two Northern Winters to heat the green house as shown in the last project report, and other than what could be called normal unexpected stoppages due to shear bolts breaking and chips in the wrong moving place, proved to be more than adequate for the heating requirement. The heat exchanger that was built, proved a little small to test the upper gas outputs, but as a complete system, provided a test bed for the automation allowing unattended operation.
Operation of Shasta 1 over the annual seasonal changes while hooked up to a online gas analyzer, highlighted the variations that can be experienced by the gas making process, some of which are almost impossible to detect, let alone control. The stability and natural evolution of the packed bed oxidation and reduction chars has always been considered the most important aspect to our gas making philosophy, so a new design feature of Shasta Class, is adjustment of the bed during operation in responce to gas quality changes. Char extraction is not used in any way to maintain the process, but some char does exit the reduction zone naturally with soot's entrained in the gas, and the dropped larger fraction augured out the bottom. The cyclone then removes most of the char entrained in the gas stream.
We are interested in two options for using producer gas to heat greenhouses; gas/air or water/air heat exchangers. Shasta 1 has been using a gas/air exchanger. Shast 2 will be tested firing a hot water boiler, with the gasifier operating in the blown mode. Drawing from experience of operating the Pacific Class gasifiers in the blown mode with hot gas cleaning using a four cluster cyclone, particulates down to about 10 micron (talcum powder) are removed before gas combustion. The test flare after cycloning was without angry red feathers or sparks and had very nice colors without any stinging radiation to indicate the presence of uncracked hydrocarbons. Flare colors are still an instant insight to indicate gas quality, and my hope in the future is to see these colors matched in real time to the gas analysis. Although Shasta 2 was designed around the original 100 kWe ( 320Nm3/hr) gas output, converting approximately 140 kg/hr fuel, the gas making will be pushed to it maximum, now that weights can be more accurately established using scales under the trailer fuel bin.
To facilitate easier management of the fuel chip supply for this test programme, the gasifier, fuel feeders, walking floor trailer storage and chipper, are together next to the log storage area. With something like 600 tons on site, one begins to appreciate how much wood you need to supply a 1-150 kWe gasifier, which clearly illustrates the concept of feeding a forest through a funnel. Bearing in mind that when a gasifier is placed in a location that is not ideal, the installation lay-outs lack ergonomics due to reusing and recycling of quite expensive components. The gasifier remains a bare bones model without mounting skids or service decks, as we fully expect to have a need to modify the fuel input componentry.
Waste char from the
gasifiers at CalForests, which everyone now calls biochar, completed first stage
composing trials last season with excellent results. These bin trials were to
establish how the various temperature profiles develop, plus of course how the
seedlings respond to these blends. The next phase is to conduct trial
of windrow piles, as there is now substantial stored char, opening up
another exciting activity associated with this Nursery business. With
the 2013 season the busiest yet, when some 20 million trees will be
shipped out to Forestry operators, they still find time to
provide continued support to research institutions, and remain privately
funded from this commercial activity.
I can only take my hat off to Tom Jopson and his dedicated staff, to show you a tiny portion of what I experience during my visits. My work on site is now less than necessary, but still rewarding to see as it provides capability for sustainable activity in a rural economically depressed area.
|Set out in a larger working area, the Shasta 2 is located next to the log storage area and Laimet Chipper. The gas outlet and flare assembly is not yet in place.|
|This view shows more of the CalForest Nursery located in Scott Valley, with the town of Etna in the distance. The ultimate plan is to heat all these glass houses via gasification.|
|Unexpected rain cause a few problems but with the conveyer flows measured for the timer programme and the horizontal test flare in place, we were ready to put all the theory to the test.|
|The twin electric igniter ports were lit with a gas torch for this first time test, due to the limited amount of charcoal available. A low flow of air bought the oxidation zone up slowly to establish a good char bed, then was increased when the gas flare could be ignited.|
|The oxidation color through the viewing port shows the healthy bed temperature at the air nozzles. We to use this port to observe the bed movement, providing valuable information during fuel testing with other than less friendly chip sizes.|
|The first lazy ignitable gas after about five minutes, shows that raw wood is still in the wrong places in the bed, and the red color comes from uncracked pyrolysis gas. This should be expected if charcoal is not filled to the expected levels found during normal operation.|
|As exothermic heat increases, the gas quality gradually changes from red to a mauve mixture but at this low output, the cyclone efficiency also allows more particulate to join the flare gas, also present in the previous photo.|
|Tom Jopson on my right looks as happy as myself after the first successful firing of the Shasta 2 Class gasifier in the blown mode.|
|Testing continued into the night to obtain data on how the automated feed timing cycle affected the flame color. The red has disappeared with only mauve and yellows present.|
|Increased output brings a slight orange feather tinge just for a very shot time, then returned to the mauve color.|
|As the fuel feed timers failed to keep up with the consumption, the loss of new pyrolysis gas from raw wood saw the gas turning to predominately CO, and the more purple flame.|
|These changes happen quickly, and the colors change from mixed to very defined as the predominant gas combusting display their presence.|
|This tells us that the gasifier is now consuming it's oxidation and reduction charcoal due to lack of refueling on time.|
|At last a fresh load of wood chip arrives into the gasifier and we can see an immediate flush of H2 in the white and a restoration of the mixed color.|
|The Laimet chipper has now been repowered with a newer engine and fitted with a hydraulic clutch.|
|The log pile is just on 600 tons and has been found to be the best way of pre-drying the fuel before chipping dry. Replacing the earlier 20 ft tops, these tops are now trucked as 40 ft logs which improve the transport economics.|
|My hand span is 9.5 inches (245 mm) to show size range of these tops. My Omega watch has been in these photos for 30 years!|
|This is a micro focus of the char from the cyclones, so you are looking at carbon blacks, soot and char down to talcum power in size. The white you see is not visible to the eye, as it is very black and sooty.|
|This larger char from the bottom clean out auger has been ground up into the finer char by the augers and is normally about 3/8" (8mm) diameter. Planned for consumption at the Nursery, finer chars are easier to use and disperse in potting mixes.|
|The reused fertilizer bags are perfect to store the waste charcoal, now described as biochar. This batch will enable larger windrow composting trials to be conducted this summer, then followed by larger trails as the amount of char increases from Shasta 1 and 2 operation this 2013 season.|
|These are some of the cast iron segments to the hot water boiler that will be used with the Shasta 2 blown gasifier. More will be shown of this project later this year.|
|We have always named our gasifiers in relationship to the region they were developed. Mt Shasta is an active volcano in the area, and provided the name for the Shasta Class Series of gasifiers.|