Last February (2017) we went to Thailand for a week, in order to test our preliminary design and discuss our design with the farmers. We collected a lot of data, got useful feedback and we had an amazing time. We made an after movie about our trip, check it out below! Furthermore, the design, experiments and survey will be briefly discussed on this page.
There is one traditional design that is used widely in the Thailand. There are some variations on it, but the basic concept is shown on the left side of the picture below. The container filled with wood is the reaction container, where pyrolysis takes place. To heat the container, which is often a 200 L oil-barrel, a fire is made at the entrance of the reaction container. The hot air is pushed inside the container with a fan. The long hollow pipe, most of the time made out of concrete or bamboo, is the condenser. The wood vinegar will flow downwards, into the bucket. The arrows in the pictures give an indication of the direction and temperature differences inside the installations. Our host in Thailand, Tanonchai, had already made the improvement to the traditional design by replacing the old condenser with a design that uses water to cool the hot gases. This way he could already produce more wood vinegar than the conventional design. His installation can be seen to the right of the picture.
The picture below shows our preliminary design in Thailand. First, we installed a more effective condenser. The condenser now exists out of a larger water reservoir and a milk churn. By having a higher cooling capacity, it makes sure that all the wood vinegar is extracted from the outflowing gases. The leftover heat is used to heat up the drying container. This is the second major change for the design. The drying container, which is a 200 L oil barrel, is filled with wood for the next run. The wood will be dried by the remaining heat of the non-condensed gases, which means the next run will take less time because a lot of the water is already extracted from the wood.
The design above is not the ideal setup we would have wanted to test in Thailand. One of the major things was that the exit from the reaction container into the condenser is low, while the entrance in the condenser should be high. Right now, there might be some losses of wood vinegar, because the pipe in the condenser is cooled by the water. The wood vinegar that condensates inside that pipe is lost. In the final design, this will be taken into account.
Experiments and feedback
We did run the original installation of Tanonchai once and we ran the installation with our adjustments. A run and the cooling down of the installation takes more than a full day, which was the limiting factor to do it more often. During these runs, we measured the temperature of different positions and took notes of what Tanonchai did, for example changing the water. Other small experiments we did include calculating the density of the used wood.
As you could see in the video, we have discussed our ideas with farmers and let them make a survey. The survey and the discussion gave us more insight into the life of the farmers and how they would like to see our solution. With these insights, a more efficient and more user-friendly design of the wood vinegar setup can be created. One of the things that stood out during discussing this set-up with the farmers is that they prefer to see a solution which can be bought at one place instead of building it themselves. Another fact was that they wanted to spend more money than was suggested beforehand.
We have learned quite a lot from our trip to Thailand and we are now working as hard as we can to process all the data and creating a final report and design. The report will be handed in on May the 28th. After the report, we will be busy creating a manual to finalise the project.