2010 Annual Report for FNE10-684
Waste Vegetable Oil Fired Flame Weeder
Summary
Our initial plan was to use Babbington Ball burner technology to sterilize the seed bed. Our goal remains the same, but our prototypes of the flamer have changed several times.
We started with the idea of running a small generator off the PTO to run the compressor pump and oil pumps required for the Babbington Ball burners. We changed this to use a PTO driven compressor and pumps. Lastly, based on our Technical Advisor Drew Lewis, we are going to try a different burner design.
Our initial prototype of the Babbington Ball burner worked well in the shop as a stationary burner. In the field, the flow of waste oil over the balls became intermittent and the flame would go out as the unit gently bumped along under field conditions. This prototype did not have a constant ignition, so when the flame went out you had to stop and reignite it. Also, because of the way in which the oil flows over the ball, separation of the flow would occur making it difficult to direct the full heat of the flame downward at the soil. Optimum burn occurred with the flame at 90 degrees from the soil which is not very effective at killing the weeds. A shield was used to direct the flame downward but a nozzle that could be directed closer to a 45 to 60 degree pitch down would be much more efficient. Other minor problems we had were with the sheave ratio which did not run the compressor fast enough to maintain 45 psi, and our trough that caught the excess oil as it flowed off the ball was too shallow and tends to slop out some vegetable oil in the field. This excess oil and the need to return it to the oil reservoir is an inherent issue with the Babbington ball burner. Only a small percentage of the oil is atomized and burned and the rest is cycled back to the reservoir. Having un-atomized waste oil in the trough is also a fire hazard. We did include a fire suppression system on the prototype but it would be far better to minimize the chance of fire. Based on input from Drew, we are going to try modifying standard oil burner guns to operate off a hydraulic motor and increase the nozzle size to prevent clogging.
Objectives/Performance Targets
Our Goal is to build a flame weeder that uses waste vegetable oil to kill seedlings to prepare a clean bed to grow our baby lettuce crop. Our initial plan was to use Babbington Ball burner technology to sterilize the seed bed. Our goal remains the same, but our prototypes of the flamer as well as determining the best burner have changed several times. We are continuing to improve the burner.
Accomplishments/Milestones
We learned a lot about Babbington burners including understanding some of the limitations in the design. The burner is most well adapted to stationary applications and difficulties arise when using the unit over the field. These limitations can be overcome; however, it may be more practical to modify a standard oil burner and increase the nozzle size so that it will not plug. Standard oil burners have limitations burning waste oil as they plug when used in typical home heating applications that burn for several hours at a time. Therefore we went with the Babbington Ball. However, in our application, we will use the burner to kill weeds for one or two hours a week and the nozzles can be cleaned out between uses. We will continue to explore the use of standard home heating fuel burner this winter.