ARF18 - Energy from biofuels for process heating and power generation

Researcher:

Dr. Andrzej Sobiesiak, Dept. of Mechanical, Automotive and Mechanicals Engineering, University of Windsor

Objectives:

Overall:

To investigate and improve the combustion performance of liquid biofuels for applications in processes heating and power generation.

Specific:

1. Experimentally characterize the atomization and combustion of liquid biofuel spray.

2. Experimentally characterize the combustion of prevaporized liquid biofuel.

3. Develop a systematic understanding of such flames structure, pollutant emissions, and combustion stability.

4. Map-out the stable operating limits of flameless oxidation as a function of fuel, air, and exhaust gas streams momentum and fuel stream discharge position.

5. Investigate extent of internal fuel reformation with changes of the fuel stream discharge position.

6. Perform measurements of velocity and velocity fluctuations, temperature and its fluctuations, heat fluxes, and species concentrations within limits of burner stable operation.

7. Formulate physical models for flameless oxidation with internal fuel reforming.

8. Launch chemical kinetics modeling of flames oxidation with internal fuel reforming.

9. Develop a systematic understanding of such flames structure, pollutant emissions, and combustion stability.

10. Design practical combustion systems that incorporate partial internal fuel reforming in process heating (burners and furnaces) turbine combustors.

11. Transfer accumulated experience and knowledge to relevant industry.

12. Graduate at least two highly qualified engineers/ researchers in the area of advanced combustion technologies.

Expected Benefits:

The lack of reliable databases on biofuels droplet, spray and vapors mixing, thermal break-up and combustion is a barrier to biofuels market acceptance and commercialization. The proposed research aims to close that gap by advancing knowledge of biofuels combustion in industrial conditions to allow the development of combustion systems which minimize environmental impact. Combustion of biofuels in such optimized systems will emphasize the major advantage that the CO2 that is produced is naturally recycled through the photosynthesis process.           

Summary of Research Results:

In the first stage, biofuels such as canola based biodiesel (esters of straight vegetable oils and their blends with ethyl alcohol) and bio-ethanol, their mixtures, and petroleum based diesel fuel and its blends with biofuels were characterized for sooting characteristics in a single droplet combustion experiments. It was found out that biodiesel droplet contains half of the soot that is present in petroleum diesel droplet flame. Further reduction of soot was observed in blends with ethanol and when liquid fuel was initially preheated.

In phase 2, the experimental trials were done on a small scale set-up that includes burner/combustor in which: 1) biofuel was atomized by an ultrasonic atomizer, 2) atomized fuel was mixed with combustion air,
3) the lean fuel/air mixture was burned in a premixed flat-flame configuration, 4) the combustion products were recirculated and mixed with combustion air and then mixed with fuel.

In the final phase, the larger scale trials that, in addition to an ultrasonic atomizer, include an experimental furnace with internal recirculation of combustion products are done at Queen's University in Kingston. The key characteristics of such optimized combustion technology are as follows: 1) liquid biofuel atomization with the use of ultrasonic atomizer and initial premixing with combustion air and recirculated combustion products to form a prepared fuel mixture, 2) the prepared fuel mixture nozzles that are positioned at an optimized radial distance from the main combustion air stream(s) injecting the prepared mixture into furnace hot combustion products with low oxygen content, 3) both the prepared fuel mixture jet(s) and the main combustion air stream(s) entrain large quantities of combustion products prior their final mixing takes place, 4) the combustion zone is extended throughout the furnace without visible flame ( thus the name
flameless oxidation), 5) the in-furnace temperatures are uniform and relatively low ensuring ultra-low NOx emissions, 6) the radiative heat transfer is dominant mode of heat exchange to furnace load with uniform radiative heat fluxes.