[Stoves] Understanding what TLUD means.... was Re: stoves and credits again

Mon Oct 2 13:36:49 CDT 2017

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Ronal W. Larson
Sent: sunnuntaina 1. lokakuuta 2017 2.41
To: Discussion of biomass <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Understanding what TLUD means.... was Re: stoves and credits again

Jaakko cc Gordon and list

                          It has been too long since we heard from you!

                          Googling showed that we had a very satisfying conversation on TLUD theory in mid August, 2014 (3 years!) - over 3-4 exchanges.  Thank you again for that.

                          I agree with all four of your sentences, below.  But can you agree with my “greater value” explanation?  (Which may not be Gordon’s intention)

                          I am reminded that the second stove had better not be a TLUD, if one is trying to determine the value of the TLUD-produced char.

                          What is happening in Finland re TLUDs?   Re biochar?  Re your own research?

Ron

                          ps.  Finland is probably the most wood-conscious country of all countries.  Hopefully biochar-consciousness also.   (I have read that Finns respond on surveys as the happiest!!)

Dear Ron and the list,

my research has recently focused on fluidized bed combustion using mixture of oxygen and carbon dioxide (to allow CO2 removal from flue gases). I have retired but still a docent in Lappeenranta University of Technology.

There has been much discussion on the use of wood, forests and global warming in Finland. Recently in the European Parliament there has been a proposal to tax the use of wood even the amount of wood and carbon storage in the forests is now growing more than it is cut in Finland. It is claimed that use of wood releases carbon in the atmosphere. This seems unfair to Finland, since many European countries have burnt their forests long time ago. Luckily for Finland the preliminary decision was in favor of the forest industry. The forests were considered as a sink of carbon. In the long run, the growth and use are in a balance and there is a sink of carbon due to use of wood in long lasting products (wooden houses, structures, furniture…). Some environmentalists emphasize the near future in the climate change. The claim has been that forest is renewing too slowly and it is better to keep the carbon the in the forest. However, they seem not to give good energy efficient alternatives for these wood products (paper, toilet paper, cardboard package, wood fuel… ) that release carbon in a shorter time. Alternative district heating could be possible by storing solar heat in large storages in the Finnish granite rock ground (I wrote a university report and a conference paper on this over 30 years ago), but production of renewable electricity from other sources than wood is problematic in Finland, since the sun is away in winter and it is not always windy. Wood chips cut from residual parts of wood (branches) are a good source of energy in Finland replacing fossil fuels. The waste of wood derived short rotation material (paper, cardboard) after recycling can also be finally burned to energy replacing the use of fossil fuels. If the forest is left by itself, it may be destroyed in storms, fires and by insects releasing the carbon without utilizing its potential.

In old times in Finland corn was cultivated on burned forest land due better fertility. It is much similar to Terra preta. From Google with word “kaskenpoltto” one can find pictures. See an artist’s view on this https://fi.wikipedia.org/wiki/Tiedosto:Raatajat_rahanalaiset.JPG . I think this girl would had been happier if TLUD had already been invented. Ash from boilers contain also some char as unburned and it is well-known that it is a good fertilizer to increase the forest growth.

There is much discussion and some commercial activity in Finland on biochar to improve the fertility and as means to reduce global warming (emeritus professor Veli Pohjonen). If you Google “biohiili”, which is biochar in Finnish, you can find what is happening here in this area, but it is mostly in Finnish. For example, a company Pajupojat (Willow Boys in English) http://pajupojat.fi/paju/biohiili/ produce biochar from fast growing willow trees. Biochar in parks in towns is also good for preventing flooding during heavy rains due to its porous structure. Biochar can be used to replace coal. Scandinavian Biopower is building a factory in town Mikkeli having capacity 200 000 tons of biochar pellets per year.

Grate combustion is similar to TLUD, the fuel is ignited from the top and pyrolysis flame front propagates downwards leaving finally a char layer that is combusted at the bottom by the primary air. For char production, the thickness or the mass of the char layer at the moment the flame front reaches the bottom is of interest to maximize the amount of char. I did not much give attention to this when our experiments were carried out about twenty years ago using a large TLUD (pot furnace) on a balance with a fan, because the char was burnt anyway for energy production. So, air was fed to the char layer also after the flame front reached the bottom. If the amount of char is to be maximized, the primary air rate should be not too high during the flame stage and stopped at its end to reduce the burning of char. Maybe there is some optimum for it to maximize the productivity. If the fuel size can be freely chosen (processed) I think a large particle size would be better to reduce the effect of char gasification. Dryer fuel is also better, because with moist fuel, one needs much energy to evaporate the water and much of this comes from char. I will maybe look anew through the measurements files to study these effects with respect to the char production.

Finland, initiated by two Finnish emeritus professors, made 2014 an initiative to the United Nations for forestation of Sahara Desert by “UN environmental troops” (in analogy to UN peacekeeping). There has been some discussion on this in Finland, but mostly in Finnish (Veli Pohjonen, Anttonen http://www.techsite.io/p/651691/gp_ref=1502253477 ). The salt would be removed from water by solar energy. The funding could be obtained from carbon taxes. In addition to reducing global warming this would also create better living conditions reducing the stream of refugees to Europe. This could be utilized to other deserts, since they are located mostly in sunny areas. There has also been fears that the sea level will rise due to ice melting in global warming. If deserts would be converted to forests, they would store much of this water in the soil and plants. Biochar is a good means to improve fertility. It could be produced in connection with energy production. In Finland, there are many CHP and district heating plants using wood that could also be used to mass production of char. Existing grate furnaces could be converted to char producers by increasing the grate movement velocity or by decreasing primary air under grate. Moving grate is much analogous to TLUD, when one follows a section moving, but it is continuous and not a batch process. The pyrolysis gas would be used for the energy and the char would be collected and quenched in the end of the grate. So the potential of biochar is great.

Jaakko

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