Energy recovery in mixed combustion of industrial waste and coal in fluidized-bed boiler

With the aim of developing an effective way of utilizing waste as an energy source, and thereby promot the use of alternatives to fossil fuel, a mixed fuel of industrial waste and coal was burned, and a running test for energy recovery was conducted, using an internal-circulation-type fluidized bed boiler designed for sole combustion of coal with a maximum steam generation rate of 70.6 t/h. Evaluation is then carried out with the focus on emissions at the exhaust and on heat recovery, revealing that industrial waste can be utilized as an alternative to coal. One of the findings is that the combustion temperature range around 1,100 K is most suitable for stable combustion of a mixed fuel of waste and coal, and it is also effective in reducing the concentration-of SO2. On the other hand, due to a lack of uniformity in properties among the components of waste when compared to sole combustion of coal and the consequent need for an extra amount of air in the furnace,adverse effects such as increased NOx and decreased boiler efficiency are observed. It is also found that the concentration of HCl, which may cause the boiler to corrode or incur other difficulties at the time of energy recovery, can be maintained at a lower level in the energy recovery zone.