Modeling the gasification based biomass co-firing in a 600MW pulverized coal boiler

Gasification based biomass co-firing was an attractive technology for utilizing biomass as an additional fuel in utility boilers. Compared to directly co-firing biomass and coal, it showed following benefits: (1) avoiding biomass delivery into the boiler, (2) reduced boiler slagging, (3) avoiding altered ash characteristics. In co-firing demonstration project, higher percentage of biomass gas for co-firing was expected. But the effect of percentage of biomass gas on combustion efficiency, boiler efficiency and pollutant emission was not clear. In the study, numerical simulation of co-firing producer gas from biomass gasification and coal in a 600 MWe tangential PC boiler was carried out with CFD method. Combustion behavior and pollutant emission for the coal fired only case and six co-firing cases were compared. The results showed that The effect of co-firing on combustion efficiency was slight, the reduction of NOx emission can be achieved. The NO removal rate was between 45% and 71%. In addition, slagging can be reduced for the temperature decreasing. And the convection heat transfer area should be increased or the biomass gas should be limited to a low percentage to achieve higher boiler efficiency.