Important Visitor to New Zealand
New Zealand is about as far away as you can go from anywhere, and only a few of those dedicated to gasification make the effort to eventually get down here to talk gasification. This week has seen a person who's name is stamped on many books and papers related to gasification, and who's efforts in the early 1970's began the almost impossible task of weaning the World away from a dependence of fossil fuels for engines, Prof Bjorn Kjellstrome from Sweden.
Able to spend four very full days catching up on the last 21 years since I last enjoyed his company, it was possible to use the opportunity to discuss quite a diverse range of technical subjects that impede the implementation of gasifiers from a commercial perspective. We did a number of fuel trials to demonstrate the behaviour of the char bed evolution between fuel species in the same gasification temperatures, and observed the unattended stability of the engine power generation. As a very hands on experience, black hands were the order of the day, even though gloves did stop most of the dirt under the nails!
Due to the arrival of much needed rain, time was taken out to visit natural forests close by, and discuss the variation of plant life that a healthy native forest requires to sustain it's self, and visit the rugged West Coast forests and beaches of West Auckland.
The following photos were taken during our sessions at the gasifier, and you can see for yourself some of the interesting thing observable in a packed charcoal bed.
|Prof Bjorn Kjellstrome from Sweden, and Doug Williams preparing for a few hours of run time with the original 1987 Pioneer Class gasifier.|
With about 70 years of personal gasification experience between us, there are plenty of funny stories to tell.
|Gasification demonstrations for visitors consume a lot of fuel, and this 34 year old Radiata pine close to the installation, gave up one of it's branches as a 300mm (12") log.|
|Cut into 50mm (2") slices, these easily cut into blocks with an axe at the rate of 50kg/hr ready for the gasifier. The economics of hand prepared fuel can be justified in appropriate rural gasification projects, where about 6kg of blocks can do the same work, and have the same value as 1.6 litres of diesel fuel.|
Taking advantage of the sun, drying the green blocks before loading into the fuel dryer in the back ground, can make a huge difference in how the gasifier performs, especially in a variable power demand situation.
|As part of this demonstration for Prof Kjellstrome, we did several separate runs with both Pine and shrub prunings from Privet hedging. This first run shows the Privet charcoal with the first of the pine at the separation line of the two fuels. The privet is a very dense hardwood with paper thin bark, and beginning to torrify 150mm (6") above the nozzles.|
|At the nozzle level, you can see that the char making is completed, and reducing in size as it enters the oxidation zone. The tar line is 50mm (2") above the nozzles, and no tar survives on the naturally forming hardened slope from the nozzles to the throat. The bed is very clean and free of char dust as can be expected from hardwood fuels.|
|Lower down the natural slope, a thick line of ash was found under each nozzle, and a sintered clinker forming on the lip of the throat tube. This is the result from using some types of wood that has thin bark and fast growing tip woods like brush,shrubs, hedging, with the bigger willow and poplar coppice. The high ash content of the bark from these fuels can be controlled by design if they are the most common fuel available in the region in these types of downdraft gasifiers.|
|Compare this photo of the pine block charcoal at the nozzle level, and see that there is much more char dust forming from this faster reacting fuel wood.|