Notes from Windward: #68

Bringing Seamus Home

Adding a storage tank to our gasifier gear

      One of our three key research projects involves the conversion of woody biomass (everything from chipped branches to junk mail) into fuels we can use to end our reliance on purchased fuels such as gasoline, diesel and propane. While the day to day business of operating a community absorbs much of our time, we're also steadily tracking down and acquiring the components needed to create our energy plant. Because we've intentionally distanced ourselves from the money economy, we rely on re-use wherever possible rather than purchase new.

     Now that the GEK is generating combustable producer gas--essentially a mixture of hydrogen, carbon monoxide, nitrogen and carbon dioxide--we're looking at the steps needed to transform that into syngas; i.e. a two to one mixture of hydrogen and carbon monoxide. There are a number of ways to go about doing that using techniques such as scrubbing with water to remove the carbon dioxide, and auto-thermal steam reformation, a step which will boost the percentage of hydrogen and eliminate the nitrogen.

     It's theoretically possible to send the gas generated by the GEK directly into the equipment designed to process the gas, but that would require synchronizing two complex processes--better to produce the gas and store it for later processing. By decoupling the generation of the gas from its conversion into a liquid fuel, a challenging project is made a bit easier.

     To store the gas, we needed a good size steel tank, the sort of tank that cost a dollar-a-gallon new last year and steel prices have gone up considerably since then. Fortunately, I remembered that the single-walled fuel tank which had formerly served the gas station in Klickitat had been removed when the state of Washington required all gasoline vendors to switch over to double-walled tanks in order to prevent the leakage of gasoline into ground water.

     My recollection was that the tank had been fairly new when removed, and so I went on a search to see where it had gotten to. Turned out that it was nestled away in a grove of oak trees a few miles down river from Klickitat. We met with the current owner, explained what we wanted to use the tank for, and were able to buy it for well below its scrap metal value. That left the considerable challenge of getting it loaded and hauled up to Windward.

     While I talked with the owner, Sarah and Opalyn went over to check out the nine-feet long, six feet wide 2,000 gallon tank. Acting in her capacity as our resident artist in charge of whimsey, Sarah decided that the tank's persona was that of Seamus the River Hippo, and the name stuck.

Seamus (pronounced "Shamus") hiding back in the oaks

     A few day later we returned with tools, our flat bed trailer and a passel of interns to fetch Seamus and bring him home to Windward to start his new life. The easy way to load a tank that size involves renting a crane, but given the cost of bringing in that heavy a crane all the way from The Dalles, the easy way wasn't going to happen. Instead, the 'terns got a lesson in what can be done given enough tools and time.

     The first step was to back the trailer most of the way into Seamus' lair.

backing the flat trailer into place

     The next step was to get a holding line around Seamus, and then roll him the rest of the way to the trailer.

rolling Seamus to the trailer

     We attached two steel ramps to the back of the trailer, and used a heavy-duty come-along and chain to slowly winch Seamus up the ramps and onto the flat trailer. Andrew used the hand wench to do the heavy lifting as Kerst and Sarah kept the safety lines snug.

wenching Seamus onto the trailer

     The key to this part of the loading was to go slow, keep the safety lines snug, and have heavy chocks in place so that the tank couldn't roll more than a couple of inches at a time.

Seamus leaves the ramps and rests on the end of the trailer

     Now came the tricky part since it was natural for people to relax once the tank was sitting on the trailer. So we stopped and had a safety talk about how important it was to remain attentive to what was going on as we rotated Seamus 90° and positioned him so that the trailer put the right amount of load on the trailer hitch.

the crew poses with Seamus

     As the sun was setting, we tightened down the chains and ropes that secured Seamus to the trailer, and headed home happy with our day's work.

Syngas -- when woody biomass is heated it generates a wide mixture of products including charcoal and various organic compounds ranging from the single carbon alcohol methanol to the complex tars and organic acids that cause smoke to burn your eyes. Most gasifiers are designed to go a bit further and convert those complex compounds, along with some of the charcoal, into hydrogen and carbon monoxide. Some gasifiers such as a Top Lit Up Draft gasifier produce a tar-rich gas which is great if you're going to burn it without notable cooling, but that gas would gum up an internal combustion engine in minutes. Other gasifiers such as the GEK we're working with, are down-draft types that do two things at once--they generate the tarry pyrolitic gas and moisture, and then draw that through glowing charcoal that breaks the gas and moisture down into hydrogen and carbon monoxide. The energy needed to drive that process comes from the partial oxidation of the charcoal. If air is used as an oxidizer, then there'll also be a good deal of nitrogen in the gas produced since air is 80% inert nitrogen.

     Essentially, the term "producer gas" refers to whatever gas a gasifier produces. While that's good enough for some applications, it's not good enough for others. For example, gas produced from either coal or woody biomass is going to contain some sulphur, something which will deactivate the catalyst used to convert carbon monoxide to methanol. Since the conversion operates at pressure, the more inert nitrogen you have to compress, the less efficient your reactor.

     Once producer gas has been cleaned of its impurities, it still needs to be adjusted so that the ratio of hydrogen to carbon monoxide is two to one. Once that's been accomplished, the gas is ready to be used to synthesize methanol which is where it gets the name of "syngas."

Notes From Windward - Index - Vol. 68