http://www.forbes.com/sites/rodadams/2016/09/16/sequestering-carbon-using-mass-quantities-of-small-scale-supertorrefaction-systems/#140c94e4282f
Sequestering Carbon Using Mass Quantities Of Small Scale Supertorrefaction Systems SEP 16, 2016 @ 10:11 AM Rod Adams Many schemes proposed for carbon capture and sequestration (CCS) operate on a massive scale. The visions are so big that testing them involves multi-billion dollar investments and project timelines that run into decades. As a result, there are only a tiny number of demonstrations and none of them provide a full system proof that CO2 can ever be economically separated, captured and permanently stored underground. Frank Shu is a world renowned astrophysicistwho recently turned his attention to the tightly linked challenge of producing plenty of energy for human society while also actively reducing — and eventually controlling — atmospheric CO2 concentrations. Dr. Shu is convinced that if humans can destabilize the climate by dumping CO2 into the atmosphere, we can also find and use ways to reverse the instability we’ve added by actively removing CO2 from the atmosphere. Shu knows that a large portion of human-produced CO2 comes out of hundreds of millions, if not billions, of small combustion units. The overall rate of production is massive. He has determined that removal might be most effective if the necessary systems can be almost equally well-distributed, with massive numbers of small-scale operations. Shu’s invention is a patented process that he calls “supertorrefaction.” It is a substantial improvement on a long established process known as torrefaction, which is a method of creating a carbon-rich material — often called char — by heating biomass to a temperature in the range of 200 ℃ to 280 ℃ in the absence of oxygen. The traditional torrefaction processes burn some of the biomass to create the heat. They use the resulting combustion gasses as the heat transfer medium. It can take several days to complete the conversion of biomass into char. Note: You probably recognize that torrefaction is a technical-sounding name for the ancient process of producing charcoal. Shu’s improvements to torrefaction involve using higher temperatures and molten salts as the heat transfer fluid. Supertorrefaction (STR) submerges wood chips or other forms of shredded biomass into a bath of molten salts — NaOAc/KOAc for example — that is held at an average temperature of 450 ℃. Direct contact in a fluid that has a volumetric heat transfer capacity that is about 2000 times that of combustion gasses at a substantially higher temperature turns the several-day-process of torrefaction into a 10 minute per batch process. Using multiple chemical reactors each with porous baskets to hold the biomass and a conveyor system, the STR process can be turned into a continuous process with a steady throughput. Shu established a company called Astron Solutions Corporation (ASC) and has worked with a team of researchers from the University of California and Academia Sinica (Taiwan) to test and create pilot-scale equipment demonstrating the process. The machinery is designed to be transportable by truck to places where there are abundant resources of biomass that is not useful for other purposes. One of the biggest disadvantages of biomass as a fuel source is that it is not very energy dense because it contains water and a number of non-combustible components. That makes it bulky and difficult to transport; it is cheaper to move the STR machinery to the source of material than to gather the material and move it to a much larger, centralized processing facility. In his ultimate clean energy vision (pg 19-23) the heat required to melt the salt and maintain it at operating temperature will be provided by molten salt reactors, either an advanced, two fluid breeder or a simplified burner like those being developed by Terrestrial Energy and ThorCon. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
