Cogasification of Coal and Biomass: A Review

Table 1

Summary of research articles on cogasification of coal and biomass.

Source	Type of feedstock	Gasifier type	Gasification conditions	Effect on syngas compositions and comments
			(i) Gasification agent—oxygen-rich air-steam; (ii) Equivalent ratio (ER) increased from 0.31 to 0.47; (iii) Temperature 948–1026°C; (iv) Steam/carbon ratio (𝐹s/𝐹c)=0.83	(i) H2 and CO decreased; (ii) Total gas yield increased; (iii) Syngas yield decreased; (iv) Smaller ER is favorable to increase Syngas yield
Kezhong et al. [21]	(i) Shenmu bituminous coal; (ii) Pine saw dust/rice straw	Fluidized bed	(i) Steam/carbon ratio (𝐹s/𝐹c) increased from 0.26 to 0.88; (ii) Temperature 921–1033°C; (iii) Equivalent ratio (ER) = 0.4	(i) Bed temperature decreased (1033 to 921°C); (ii) H2 and CO first increased and then decreased; (iii) Steam/carbon ratio of 0.5 is preferred
			(i) Biomass/coal ratio increased from 0 to 33%; (ii) Equivalent ratio (ER) = 0.34; (iii) Steam/carbon ratio (𝐹s/𝐹c)=0.77; (iv) Temperature: 912–976°C	(i) Bed temperature increased (912 to 976°C); (ii) H2 increased and CO decreased; (iii) Slight decrease in Syngas yield
			(i) Temperature increased from 750 to 890°C; (ii) Gasification agent—air, steam, and mixture of both; (iii) Steam input rate = 5.0 Kg/h; (iv) Air input rate = 4.4 Kg/h	(i) CO2 decreased and H2 increased; (ii) Not much effect on char; (iii) Energy conversion increased; (iv) Gas composition (v/v) at 890°C: H2: 39.4%, CO: 17.3%, CO2: 20.4%, CH4: 14.9% and CnHm—7.6%
Pinto et al. [18]	(i) 60% coal; (ii) 20% pine; (iii) 20% polyethylene	Fluidized bed	(i) (Oxygen/oxygen + steam) ratio increased from 0.02 to 0.28; (ii) Temperature: 850°C; (iii) Feedstock input rate = 5.0 Kg/h	(i) 15% reduction in H2 production; (ii) 38% and 53% reduction in CH4 and hydrocarbons; (iii) Total gas yield decreased
			(i) (Steam + O2)/fuel ratio increased from 1.1 to 1.9; (ii) Air input rate = 4.4 Kg/h; (iii) Steam input rate = 5 Kg/h	(i) H2 and CO2 first increased and then decreased; (ii) CO and CH4 first decreased and then increased; (iii) (Steam + O2)/fuel ratio of 1.3–1.5 is preferred
Kumabe et al. [14]	(i) Mulia coal; (ii) Japanese cedar	Fixed bed downdraft	(i) Air-steam gasification; (ii) Biomass ratio increased from 0 to 1	(i) H2 decreased and CO2 increased; (ii) Cold gas efficiency increased; (iii) No effect on CH4 concentration
Vélez et al. [15]	(i) Columbian coal; (ii) Coffee husk; (iii) Sawdust; (iv) Rice husk	Fluidized bed	(i) Air-steam gasification; (ii) Biomass ratio was increased from 6% to 15%; (iii) Temperature <1000°C; (iv) Steam/fuel ratio was increased	(i) Bed temperature decreased by 30°C with 15% biomass; (ii) Energy efficiency decreased; (iii) High H2 concentration was obtained with increase in biomass ratio as well as steam/fuel ratio
Pan et al. [16]	(i) Pine chips; (ii) Black coal; (iii) Sabero coal	Fluidized bed gasifier	(i) Biomass ratio was increased: 0%, 25%, 40%, and 100%; (ii) Air-steam gasification; (iii) Temperature = 840–910°C	(i) CO increased; (ii) H2 first increased up to 25% of biomass and then decreased; (iii) Overall thermal efficiency increased (40% to 68%); (iv) Carbon conversion efficiency increased (63% to 83.4%)
Couhert et al. [28]	(i) Beachwood; (ii) Torrefied beachwood at 240°C; (iii) Torrefied beachwood at 260°C	Entrained flow reactor	(i) Feedstock: beachwood and torrefied beachwood; (ii) Temperature = 1200 and 1400°C	(i) CO2 remained same; (ii) H2 was increased by 7% with torrefied wood; (iii) CO was increased by 20% with torrefied wood