EVALUATION OF BIOMASS AND COAL CO-GASIFICATION OF BRAZILIAN FEEDSTOCK USING A CHEMICAL EQUILIBRIUM MODEL

Rodrigues, R.; Muniz, A. R.; Marcilio, N. R.

doi:10.1590/0104-6632.20160332s00003479

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THERMODYNAMICS • Braz. J. Chem. Eng. 33 (2) • Apr-Jun 2016 • https://doi.org/10.1590/0104-6632.20160332s00003479 copy

EVALUATION OF BIOMASS AND COAL CO-GASIFICATION OF BRAZILIAN FEEDSTOCK USING A CHEMICAL EQUILIBRIUM MODEL

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Coal and biomass are energy sources with great potential for use in Brazil. Coal-biomass co-gasification enables the combination of the positive characteristics of each fuel, besides leading to a cleaner use of coal. The present study evaluates the potential of co-gasification of binary coal-biomass blends using sources widely available in Brazil. This analysis employs computational simulations using a reliable thermodynamic equilibrium model. Favorable operational conditions at high temperatures are determined in order to obtain gaseous products suitable for energy cogeneration and chemical synthesis. This study shows that blends with biomass ratios of 5% and equivalence ratios ≤ 0.3 lead to high cold gas efficiencies. Suitable gaseous products for chemical synthesis were identified at biomass ratios ≤ 35% and moisture contents ≥ 40%. Formation of undesirable nitrogen and sulfur compounds was also analyzed.

Keywords:
Coal and biomass energy; Co-gasification; Equilibrium modeling

Phase	Group	Chemical species
Gas	Carbon compounds	C(g), CH₄, CO, CO₂
	Oxygen compounds	O, O₂
	Hydrogen compounds	H, H₂, OH, H₂O
	Nitrogen compounds	N, N₂, NH₃, NO, HCN
	Sulfur compounds	S, S₂, SH, SO, SO₂, SO₃, H₂S, COS, CS₂
	Chlorine compounds	Cl, Cl₂, HCl, ClO, SCl₂
	Phosphorus compounds	P₂, PH₃, PO, PO₂, P₂O₅, P₃O₆, P₄O₁₀, PCl₃
	Other compound	Ar
Solid	Carbon	C(s)
	Aluminium compounds	Al₂O₃, AlN, AlCl₃, Al₂SiO₅, Al₆Si₂O₁₃
	Calcium compounds	Ca, CaO, CaO₂H₂, CaS, CaSO₄, CaCl₂
	Iron compounds	Fe, FeO, Fe₂O₃, Fe₃O₄, FeS, FeCl₂
	Potassium compounds	K, K₂O, KCN, K₂CO₃, K₂S, K₂SO₄, KCl
	Magnesium compounds	MgO, MgS, MgSO₄,MgCl₂, MgAl₂O₄, MgSiO₃, Mg₂SiO₄
	Sodium compounds	Na₂O, Na₂CO₃, NaCN, Na₂SO₄, NaCl, NaAlO₂
	Silicon compounds	Si, SiC, SiO₂, Si₃N₄, Si₂N₂O
	Titanium compounds	TiC, TiO₂, Ti₂O₃, TiN, TiCl₃

Equilibrium reaction	ΔH_r (MJ/kmol)	Equation
CH₄ + H₂O ↔ CO + 3H₂	+ 206.0	(R1)
CH₄ + CO₂ ↔ 2CO + 2H₂	+ 247.4	(R2)
CO + H₂O ↔ CO₂ + H₂	- 41.0	(R3)
C(s) + H₂O ↔ CO + H₂	+ 131.4	(R4)
C(s) + 2H₂O ↔ CO₂ + 2H₂	+ 90.1	(R5)

	Coal¹ 1 Kalkreuth et al. (2006),	Rice husk² 2 CIENTEC (1986)apudHoffmann (1999),	Coconut residue ³ 3 Andrade et al. (2004) and Nogueira et al. (2000)apud Andrade et al. (2004),	Sawmill wood waste⁴ 4 Wander et al. (2004),	Charcoal⁵ 5 Fuwape (1993),	Sugarcane bagasse⁶ 6 Linero and Lamônica (2005)apudSeabra et al. (2010),	Sugarcane straw⁶ 6 Linero and Lamônica (2005)apudSeabra et al. (2010),	Elephant grass⁷ 7 Broetto et al. (2012)
Proximate analysis (%^wt wt = weight, , ^db db = dry basis, )
Moisture (^wb wb = wet basis,	11.06	12.00	83.74	11.78	7.14	50.20	2940	9.97
Volatile matter	20.29	67.80	10.20	86.44	^N/A N/A = not available.	79.90	83.30	68.93
Fixed carbon	25.09	13.60	79.70	13.22	^N/A N/A = not available.	18.00	12.80	7.95
Ash	42.71	18.60	10.30	0.35	2.43	2.20	3.90	12.84
Ultimate analysis (%^wt wt = weight, , ^daf daf = dry ash free basis, )
C	33.39	38.30	48.23	51.46	65.19	44.60	46.20	46.52
H	3.47	4.00	5.23	6.10	5.55	5.80	6.20	5.87
N	0.61	0.50	2.98	0.26	0.83	0.60	0.50	1.47
O	16.68	38.60	33.19	41.85	25.65	44.50	43.00	46.04
S	2.15	0.08^* * Mean value from Vassilev et al. (2010).	0.12	0.01^* * Mean value from Vassilev et al. (2010).	0.37	0.10	0.10	0.10
Cl	0.013	0.12^* * Mean value from Vassilev et al. (2010).	^N/A N/A = not available.	0.01^* * Mean value from Vassilev et al. (2010).	^N/A N/A = not available.	0.02	0.10	0.21^* * Mean value from Vassilev et al. (2010).
HHV (MJ/kg, b)	13.39	15.49	22.81	20.25	25.28	18.10	17.40	16.94

	Ash composition (%^wt wt = weight, , ^db db = dry basis. )
Fuel	SiO₂	CaO	Al₂O₃	Fe₂O₃	Na₂O	K₂O	MgO	P₂O₅	TiO₂	SO₃
Coal¹ 1 Kalkreuth et al. (2006),	29.04	1.02	9.02	4.21	0.16	0.70	0.41	0.03	0.36	2.28
Rice husk² 2 Mean value from five sources (Vassilev et al., 2010),	94.48	0.97	0.21	0.22	0.16	2.29	0.19	0.54	0.02	0.92
Coconut residue³ 3 Mean value for natural biomass (Vassilev et al., 2010),	29.14	25.99	4.49	5.60	2.54	19.40	5.60	5.92	0.24	3.27
Sawmill wood waste⁴ 4 Mean value for woody biomass (Vassilev et al., 2010),	22.22	43.03	5.09	3.44	2.85	10.75	6.07	3.48	0.29	2.78
Charcoal⁴ 4 Mean value for woody biomass (Vassilev et al., 2010),	22.22	43.03	5.09	3.44	2.85	10.75	6.07	3.48	0.29	2.78
Sugar cane bagasse⁵ 5 Mean value from two sources (Vassilev et al., 2010),	46.79	4.91	14.60	11.12	1.61	6.95	4.56	3.87	2.02	3.57
Sugar cane straw⁶ 6 Mean value for straws (Vassilev et al., 2010),	43.94	14.13	2.71	1.42	1.35	24.49	4.66	4.13	0.16	3.01
Elephant grass⁷ 7 Mean value for grasses (Vassilev et al., 2010).	46.18	11.23	1.39	0.98	1.25	24.59	4.02	6.62	0.08	3.66

	Gas composition (%^vol vol = volume, , ^wb wb = wet basis, )							Gas yield (Nm³/kg, ^db db = dry basis, )	^HHV HHV = higher heating value, (MJ/kg, ^db db = dry basis, )	^CC CC = carbon conversion, (%)	^CGE CGE = cold gas efficiency. (%)
	H₂	CO	CH₄ (ppm)	CO₂	H₂O	H₂S (ppm)	NH₃ (ppm)	Gas yield (Nm³/kg, ^db db = dry basis, )		^CC CC = carbon conversion, (%)	^CGE CGE = cold gas efficiency. (%)
High ash coal	10.6	21.5	0.77	5.51	4.50	1690	3.53	0.66	4.31	99.8	44.0
Rice husk	12.2	23.1	0.67	8.64	7.55	86.8	4.07	0.96	6.26	99.9	53.4
Coconut residue	13.8	24.1	1.26	6.03	5.70	31.2	5.00	1.34	9.12	100	55.9
Wood waste	14.6	23.6	1.18	6.77	6.91	0.0002	5.31	1.44	9.37	100	66.1
Charcoal	13.3	28.1	2.87	3.29	2.58	187	4.85	1.76	13.7	100	75.9
Cane bagasse	14.5	22.0	0.84	8.15	8.88	52.2	5.17	1.27	7.79	100	60.7
Cane straw	14.9	21.8	0.96	7.54	8.55	37	5.45	1.32	8.03	100	66.8
Elephant grass	13.7	21.5	0.73	8.35	8.79	7.06	4.80	1.12	6.84	100	56.5

	MC (%^wt wt = weight, )	ER	Gas composition (%^vol vol = volume, , ^wb wb = wet basis, )							CC (%)	Gas yield (Nm³/kg, ^db db = dry basis, )	^HHV HHV = higher heating value, (MJ/kg, ^db db = dry basis, )	^CGE CGE = cold gas efficiency. (%)
	MC (%^wt wt = weight, )	ER	H₂	CO	CH₄ (ppm)	CO₂	H₂O	H₂S (ppm)	NH₃ (ppm)	CC (%)	Gas yield (Nm³/kg, ^db db = dry basis, )		^CGE CGE = cold gas efficiency. (%)
High ash coal	0	0.1 0.2 0.6	22.4 19.0 4.92	28.1 31.1 11.6	296 85.6 0.02	0.17 0.39 10.5	0.23 0.39 7.39	2920 2340 1320	8.33 7.34 1.21	69.6 90.4 100.0	0.59 0.68 0.59	3.76 4.85 2.85	50.2 58.4 24.9
	10	0.2 0.4 0.6	22.8 12.3 5.89	27.7 16.9 9.16	10.1 0.45 0.02	3.39 7.83 11.3	4.63 9.43 12.1	2070 1570 1260	8.71 4.21 1.53	99.3 99.9 100.0	0.79 0.70 0.62	4.33 3.34 2.19	75.3 48.4 26.5
	20	0.2 0.4 0.6	23.4 12.8 6.13	21.1 12.8 6.81	3.11 0.23 0.01	6.47 9.42 11.9	11.9 15.6 17.7	1830 1430 1170	8.46 4.27 1.56	99.8 100.0 100.0	0.82 0.71 0.61	3.32 2.51 1.59	82.9 51.5 26.7
	40	0.2 0.4 0.6	20.5 10.9 4.42	10.8 6.26 2.74	0.41 0.03 0.001	9.41 10.6 11.7	29.5 30.7 31.2	1370 1130 95	6.17 3.07 0.88	100.0 100.0 100.0	0.78 0.65 0.53	1.74 1.21 0.62	95.4 52.7 20.8
Wood waste	0	0.1 0.2 0.6	33.2 27.6 7.23	38.7 39.4 13.3	1130 13.8 0.06	0.12 0.58 11.2	0.17 0.67 10.1	1.62×10^-4 1.42×10^-4 1.89×10^-4	12.6 11.2 2.04	81.7 100.0 100.0	1.46 1.63 1.27	9.82 11.9 6.54	90.5 100.0 38.8
	10	0.2 0.4 0.6	28.2 15.2 7.59	34.8 21.0 11.8	22.6 0.86 0.05	2.88 7.97 11.7	3.86 9.51 12.4	1.94×10^-4 2.17×10^-4 2.26×10-4	11.3 5.53 2.16	100.0 100.0 100.0	1.67 1.47 1.28	10.0 7.87 5.45	104.1 68.2 39.4
	20	0.2 0.4 0.6	28.1 15.2 7.51	29.9 18.0 9.93	9.39 0.55 0.03	5.09 9.18 12.3	7.93 12.8 15.4	2.56×10^-4 2.68×10^-4 2.79×10^-4	11.0 5.46 2.10	100.0 100.0 100.0	1.67 1.45 1.26	8.24 6.39 4.31	105.4 67.5 37.6
	40	0.2 0.4 0.6	25.7 13.4 5.73	19.7 11.3 5.35	1.98 0.14 0.005	8.77 11.2 13.2	19.0 21.9 23.4	4.12×10^-4 3.98×10^-4 3.84×10^-4	9.30 4.37 1.36	100.0 100.0 100.0	1.54 1.30 1.08	5.01 3.63 2.09	97.5 56.5 25.6

Blend	^Scenario* *Scenario (I) considers the recommended BR to reach CGE ≥ 80% for cogeneration purposes and H2/CO = 2.0 ± 5% for chemical synthesis purposes. Scenario (II) includes scenario (I) and appropriate H2S and NH3 contents.	Cogeneration purposes			Chemical synthesis purposes
Blend		BR (%)	MC (%)	ER	BR (%)	MC (%)	ER
Coal	(I)	^N/A N/A = not applicable,	10-50	≤ 0.25	^N/A N/A = not applicable,	40-50	^- -(dash) = any value.
Coal	(II)	Not found			^N/A N/A = not applicable,	50	≥ 0.75
Coal-rice husk	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.35	^- -(dash) = any value.	40-50	^- -(dash) = any value.
Coal-rice husk	(II)	≥ 95	≤ 5	≤ 0.1	≤ 20	50	≥ 0.75
Coal-coconut	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.4	≤ 65	40-50	^- -(dash) = any value.
Coal-coconut	(II)	≥ 70	5-30	≤ 0.3	≤ 10	50	≥ 0.75
Coal-wood	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.3	≤ 60	40-50	^- -(dash) = any value.
Coal-wood	(II)	≥ 90	≤ 25	≤ 0.3	≤ 10	50	≥ 0.75
Coal-charcoal	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.5	≤ 35	40-50	^- -(dash) = any value.
Coal-charcoal	(II)	Not found			≤ 5	50	≥ 0.75
Coal-cane bagasse	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.4	≤ 85	40-50	^- -(dash) = any value.
Coal-cane bagasse	(II)	≥ 95	≤ 10	≤ 0.1	≤ 10	50	≥ 0.75
Coal-cane straw	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.45	≤ 90	40-50	^- -(dash) = any value.
Coal-cane straw	(II)	≥ 75	≤ 20	≤ 0.3	≤ 10	50	≥ 0.75
Coal-elephant grass	(I)	^- -(dash) = any value.	^- -(dash) = any value.	≤ 0.4	^- -(dash) = any value.	40-50	^- -(dash) = any value.
Coal-elephant grass	(II)	≥ 55	^- -(dash) = any value.	≤ 0.4	≤ 15	50	≥ 0.75

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Acompanhe os números deste periódico no seu leitor de RSS

[TFN01] ^wt
= weight,

[TFN02] ^db
= dry basis,

[TFN03] ^wb
= wet basis,

[TFN04] ^daf
= dry ash free basis,

[TFN05] ^N/A
= not available.

[TFN06] ¹
et al,

[TFN07] ²
CIENTEC (1986)CIENTEC, Aproveitamento Energético da Casca de Arroz. Fundação de Ciência e Tecnologia, CIENTEC, Porto Alegre, Brazil (1986). (In Portuguese).apudHoffmann (1999)Hoffmann, R., A method to evaluate the regionalised energy generation, with power plants lower than 1 MW, by the residual biomass administration-The rice husk's case. PhD Thesis, Department of Mechanical Engineering, Federal University of Rio Grande do Sul, Porto Alegre, Brazil (1999). (In Portuguese).,

[TFN08] ³
et al and et alapud Andrade et al. (2004),

[TFN09] ⁴
et al,

[TFN10] ⁵
Fuwape (1993)Fuwape, J., Charcoal and fuel value of agroforestry tree crops. Agroforest. Syst., 22(3), p. 175-179 (1993).,

[TFN11] ⁶
Linero and Lamônica (2005)Linero, F. A. B., Lamônica, H. M., Integração BIG/GT - Usina. Geração de energia por biomassa: Bagaço e palha de cana. Seminário Alternativas Energéticas a partir da Cana-de-açúcar. Centro de Tecnologia Canavieira, CTC, Piracicaba, Brazil (2005). (In Portuguese).apudet al,

[TFN12] ⁷
et al

[TFN13] ^*
Mean value from et al.

ΔH_r	Heat of reaction (MJ/kmol)
N	Number of chemical species
n_O ₂	Number of moles of O₂ injected into the reactor (kmol)
n_O _2,stoic	Stoichiometric number of moles of O₂ (kmol)
x_i,est	Estimated volume fraction of species i (m³/m³)
x_i,exp	Measured volume fraction of species i (m³/m³)
Y	Gas yield (Nm³/kg)
*Abbreviations*
BR	Biomass Ratio (kg/kg)
CC	Carbon Conversion (kmol/kmol)
CGE	Cold Gas Efficiency (MJ/MJ)
daf	Dry ash-free basis
db	Dry basis (H₂O-free basis)
ER	Equivalence Ratio (kmol/kmol)
HHV	Higher Heating Value (MJ/kg)
LHV	Lower Heating Value (MJ/kg or MJ/Nm³)
MC	Moisture Content (kg/kg)
N/A	Not Available, Not Applicable
%vol	Volume percent (m³/m³)
wb	Wet basis
%wt	Weight percent (kg/kg)