Advanced Flue Gas Recycle and Reforming Technology

Flue gas recycle (FGR) is a proven means of reducing NOx emissions. FGR systems divert a portion of the cooled flu gas leaving the boiler to be mixed with the combustion air and fuel gas entering the burner. In the case of the boilers in waste to energy plants, recycle of the flue gas also helps to control the temperature of the hot gasses entering the boiler. This helps reduce fouling of the boiler tubes and  extend boiler service life.

Shown below is a color coded layout of an EPR tandem reactor gasification line with flue gas recycle. The the thermal generation components of the plant are shown in Green, the heat exchange and steam production components are in Blue and the flue gas recycle and clean-up components are shown in Red.

An isometric view of an EPR tandem reactor gasification line is shown below. In this configuration, carbon containing ash from two shallow bed updraft gasifiers is conveyed to a rotary kiln, which can also accept ancillary fuels such as tire shreds or medical waste. Temperatures in the rotary kilns are sufficiently high to assure full conversion of the carbon in the ash, and in the ancillary fuels to fuel gas. Solid residue leaving the rotary kilns is an inert non-hazardous and carbon free sintered material that is suitable for use as landfill daily cover or as construction fill.

Each of these modular systems can be scaled to process up to 480 tons per day and produce between 16 and 24 MWe or renewable electrical power.

 

Reforming of the raw producer gas from the gasifiers can be carried out using air, steam, recycled flue gas, oxygen, or any combination of these gasses. Reforming with oxygen is particularly effective in cracking any tars in the raw gas to make it suitable for pipeline transport in cases where a low Btu gas customer is located within a reasonable distance.