Biomass Blending Ratio Research Articles

Taguchi approach for co-gasification optimization of torrefied biomass and coal

This study employs the Taguchi method to approach the optimum co-gasification operation of torrefied biomass (eucalyptus) and coal in an entrained flow gasifier. The cold gas efficiency is adopted as the performance index of co-gasification. The influences of six parameters, namely, the biomass blending ratio, oxygen-to-fuel mass ratio (O/F ratio), biomass torrefaction temperature, gasification pressure, steam-to-fuel mass ratio (S/F ratio), and inlet temperature of the carrier gas, on the performance of co-gasification are considered. The analysis of the signal-to-noise ratio suggests that the O/F ratio is the most important factor in determining the performance and the appropriate O/F ratio is 0.7. The performance is also significantly affected by biomass along with torrefaction, where a torrefaction temperature of 300°C is sufficient to upgrade eucalyptus. According to the recommended operating conditions, the values of cold gas efficiency and carbon conversion at the optimum co-gasification are 80.99% and 94.51%, respectively.

Thermogravimetric analysis and kinetics of co-pyrolysis of raw/torrefied wood and coal blends

The properties of biomass can be improved via torrefaction, and torrefied wood is a fuel with the potential to partially replace coal. In this study, raw Cryptomeria japonica (WRaw) is torrefied at 250 (TW250) and 300°C (TW300) for 1h, and then mixed with an anthracite coal to undergo co-pyrolysis. A thermogravimetric analyzer is used to examine the co-pyrolysis characteristics of fuel blends and five different biomass blending ratios (BBRs) of 100, 75, 50, 25, and 0wt.% are taken into consideration. When WRaw, TW250, and the coal are tested, the pyrolysis is characterized by a three-stage reaction, whereas four-stage thermal degradation is found for TW300 and fuel blends. The predictions from the linear superposition of the thermal decomposition of individual fuels fit the experimental data of the fuel blends, suggesting that the interaction or synergistic effect of co-pyrolysis between the raw/torrefied C. japonica and the coal is slight. The co-pyrolysis kinetics of the fuel blends is also analyzed. The variation of chemical kinetics with decreasing BBR in the second stage is different from that in the third stage. That is, an increase in BBR leads to an increase in the activation energy in the second stage, whereas it causes a decrease in the third stage. This is attributed to that the reactivities of cellulose and lignin in biomass are different from that of coal in the two stages.

Effects of feedstock on co-pyrolysis of biomass and coal in a free-fall reactor

The effects of feedstock on the co-pyrolysis of biomass and coal were investigated in a free-fall reactor from 500°C to 700°C with a biomass blending ratio of 0 to 100%. The selected coal samples were Dayan brown coal (DY) and Tiefa bituminous coal (TF), and the biomass samples were agricultural residues legume straw (LS) and woody residues pine sawdust (SD). The results indicate that synergy can occur even in a short-gas-residence time during the co-pyrolysis of biomass and coal in a free-fall reactor. The product yields and the CO 2 reactivity of char from the co-pyrolysis are greatly influenced by the type of feedstock. The synergy in the presence of LS with high holocellulose and ash content is more significant than that in the presence of SD. The liquid yield of high-rank TF coal co-pyrolysis is higher than that of low-rank DY coal. The char reactivity can be improved by the co-pyrolysis at specific conditions. The co-pyrolysis in the presence of DY can improve the reactivity of the char produced.

Combustion Characteristics of Coal and Biomass Blends with Adding Absorbing Sulfur Agent

The combustion characteristics of coal and biomass blends with adding adsorbing sulfur agent was investigated using thermogravimetric analyzer. The results indicated that the combustion process of the blends were similar to that of pure coal and biomass, which there were two apparent weight-loss peaks--one for volatile burning and another for char burning. The combustion stages could be divided into the dewatering period, volatilization and burning, char burning and burnout. Nevertheless, the combustion characteristics of blends varied with the biomass blending ratio and Ca/S ratio. Due to the increase of biomass blending ratio, the volatile matter content of blends increased, which leaded to the increase of peak value for volatile burning stage. In this stage, due to the lower reaction temperature, less SO2was produced and the reaction to CaO was slower. With the progress proceeding, char began to be burned and large heat was released and the adsorbing sulfur reactions were becoming stronger. Although the mass of blends reduced fastly, the mass of CaSO3and CaSO4increased compared to CaO, Which leaded to a wider temperature range of weight-loss for the char burning period. At the same linear temperature gradient, an increase of Ca/S decreased the temperature of volatilization and char burning, and the residue was increased due to more CaO additive. Therefore, the appropriate ratio of Ca/S was necessary to improve the combustion and adsorbing sulfur efficiency. In this study, a basic kinetics analysis for coal and biomass blends is provided. The kinetics parameters reveal that the combustion process of coal and biomass blends with adding absorbing sulfur agent can be described by a first order reaction equation.

The effect of air staged, co-combustion of pulverised coal and biomass blends on NO x emissions and combustion efficiency

Co-firing of biomass residues with coal is continuously increasing in it’s application in coal-fired boilers for electricity production. In this study, co-firing experiments were performed using a Russian coal with a range of biomasses, shea meal (SM), cotton stalk (CS), sugarcane bagasse (SB T), sugarcane bagasse (SB R) and wood chips (WC) as biomasses in 5%, 10% and 15% thermal fractions to evaluate their potential as substitute fuel and an agent for NO x control. It was found that the addition of biomass increased NO reduction under both un-staged and air-staged conditions. However, NO reductions obtained under optimum conditions of primary zone stoichiometry (SR 1 = 0.9) and over-fire air (OFA) injection port location 3, were found to be significantly higher than un-staged co-firing for the same biomass thermal share in the fuel blend. It was found that the addition of biomass has a positive effect on carbon burnout under the optimum conditions that were determined in the study. A 10% biomass blending ratio (BBR) was found to be optimum for air-staging conditions. When co-fired under optimum air-staged conditions, a 10% BBR of sugarcane bagasse (SB R), shea meal (SM), wood chips (WC), cotton stalk (CS) and sugarcane bagasse (SB T) in coal gave NO reduction of 49%, 51%, 53%, 60% and 72%, respectively.

Shea meal and cotton stalk as potential fuels for co-combustion with coal

The efficient management of waste biomass is an important environmental problem in agricultural countries. Often land-fill is the main disposal route with ramifications including CH 4 release having 21 times greater global warming potential per molecule than CO 2. Biomasses are considered to be CO 2-neutral fuels when combusted. Moreover, they are renewable and covered by the renewable obligation scheme and eligible for certificates in the UK. The overall objective of the investigation is to assess the performance of selected biomass and coal co-firing under two different modes of operation, air-staging and fuel-staging with the benefit of reduced-NO x and SO 2 emissions in power plant. The biomasses chosen for the study, shea meal (SM) and cotton stalk (CS) have very different cellulose/lignin compositions and different reported thermal behaviour. A series of experiments have been carried out in a 20 kW, down fired combustor using coal, shea meal–coal and cotton stalk–coal blends under un-staged, air-staged and fuel-staged co-combustion configurations. For air-staging, an optimum value of primary zone stoichiometry SR 1 = 0.9 was found. Keeping it fixed, the shea meal and cotton stalk content in the coal–biomass blends was set to 5%, 10% and 15% on thermal basis. NO reductions of 51% and 60% were achieved using SM and CS, respectively, with an optimum thermal biomass blending ratio (BBR) of 10%. The results obtained were compared with un-staged and air-staged results for coal without the addition of biomass. Similarly for fuel-staging, keeping the length of the reburn and burnout zone fixed, SM and CS were evaluated as reductive fuel using different reburn fuel fractions ( R ff) of 5%, 10%, 15% and 20%. NO reductions of 83% and 84% were obtained with an optimum R ff of 15% with an optimum reburn zone stoichiometry of SR 2 = 0.8 for both SM and CS, respectively. SO 2 reduction and char burnout efficiency were also evaluated. It was found that addition of biomass coupled with air and fuel-staging techniques reduced-NO x and SO 2 simultaneously while at the same time improving the char burnout efficiency.

Co-gasification of Biomass with Coal and Oil Sand Coke in a Drop Tube Furnace†

The present paper is aimed at investigating the co-gasification of biomass with coal and oil sand fluid coke. Chars were obtained from individual fuels and blends with different blend ratios of coal, oil sand coke, and biomass in a drop tube furnace at different temperatures. The chars were then gasified in a thermogravimetric analyzer (TGA) under CO2 atmosphere to determine their reactivity. Results showed that the effect of the blending ratio of biomass to other fuels on the reactivity of the co-pyrolyzed chars is more pronounced on chars prepared at low temperatures and the effect becomes less significant as the pyrolysis temperature increases. The increased reactivity at a higher biomass blending ratio is due to the presence of synergetic effects originating from the interaction of the two fuels. Scanning electron microscopy images showed differences in shapes and particle size distribution of char particles from biomass and coal/coke. These also showed the agglomeration of coal and coke chars with bi...

An evaluation on rice husks and pulverized coal blends using a drop tube furnace and a thermogravimetric analyzer for application to a blast furnace

To evaluate the potential of pulverized coals partially replaced by rice husks used in blast furnaces, thermal behavior of blends of rice husks and an anthracite coal before and after passing through a drop tube furnace (DTF) was investigated by using a thermogravimetry (TG). For the blends of the raw materials in the TG, fuel reaction with increasing temperature could be partitioned into three stages. When the rice husks were contained in the fuel, a double-peak distribution in the first stage was observed, as a consequence of thermal decompositions of hemicellulose, cellulose and lignin. A linear relationship between the char yield and the biomass blending ratio (BBR) developed, reflecting that synergistic effects in the pyrolytic processes were absent. This further reveals that the coal and the rice husks can be blended and consumed in blast furnaces in accordance with the requirement of volatile matter contained in the fuel. After the fuels underwent rapid heating (i.e. the DTF), a linear relationship from the thermogravimetric analyses of the unburned chars was not found. Therefore, the synergistic effects were observed and they could be described by second order polynomials. When the BBR was less than 50%, varying the ratio had a slight effect on the thermal behavior of the unburned chars. In addition, the thermal reactions of the feeding fuels and of the formed unburned chars behaved like a fingerprint.

Co-combustion performance of coal with rice husks and bamboo

Biomass has been regarded as an important form of renewable energy due to the reduction of green house gas emission such as carbon dioxide. An experimental study of co-combustion of coal and biomass was performed in a laboratory-scale combustion facility. Rice husks and bamboo were the selected biomass fuels in this study due to their abundance in the Asia-Pacific region. Experimental parameters including the biomass blending ratio in the fuel mixture, relative moisture content and biomass grinding size were investigated. Both energy release data and pollutant emission information were obtained. Due to the decrease in the heating value from adding biomass in the fuel mixture, the combustion temperature and energy output from the co-firing process were reduced compared with coal combustion. On the other hand, gaseous pollutant emissions including carbon monoxide (CO), carbon dioxide (CO 2), nitrogen oxides (NO x ) and sulfur dioxide (SO 2) were reduced and minimum energy-based emission factors were found in the range of 10–30% biomass blending ratio. With an increase in the moisture content in the biomass, decreases in combustion temperature, SO 2, NO x and CO 2 emissions were observed, while an increase in CO emissions was found. It has also been observed that chemical kinetics may play an important role compared to mass diffusion in the co-firing process and the change in biomass grinding size does not have much effect on the fuel burning rate and pollutant emissions under the current experimental conditions.

Co-firing coal with rice husk and bamboo and the impact on particulate matters and associated polycyclic aromatic hydrocarbon emissions

The potential of co-firing rice husk and bamboo with coal was studied in a bench-scale pulverized fuel combustion reactor. Experimental parameters including biomass blending ratio in the fuel mixture, biomass grinding size, excess air ratio and relative moisture content in the biomass were investigated. Particulate Matters in the forms of PM 10, PM 2.1, ultra fine particles as well as the associated Polycyclic Aromatic Hydrocarbons (PAHs) emissions were evaluated. An operation range between 10% and 30% of biomass to coal ratio was found to be the optimum range in terms of minimum pollutant emissions per unit energy output. Co-combustion of coal with biomass seemed to have the effect of moving the fly-ash in PM 2.1 to a larger size range, but increasing the number counts of the ultra fine particles. It was noted that the much higher volatile matter content in the biomass fuels has played a key role in improving the combustion performance in the system. However, slagging, fouling and formation of clinker could be the issues requiring attention when using biomass co-combustion in conventional boilers.

97/04000 Effect of burner design on combustion and SH/RH spray performance

Co-firing of biomass residues with coal is continuously increasing in it’s application in coal-fired boilers for electricity production. In this study, co-firing experiments were performed using a Russian coal with a range of biomasses, shea meal (SM), cotton stalk (CS), sugarcane bagasse (SBT), sugarcane bagasse (SBR) and wood chips (WC) as biomasses in 5%, 10% and 15% thermal fractions to evaluate their potential as substitute fuel and an agent for NOx control. It was found that the addition of biomass increased NO reduction under both un-staged and air-staged conditions. However, NO reductions obtained under optimum conditions of primary zone stoichiometry (SR1 = 0.9) and over-fire air (OFA) injection port location 3, were found to be significantly higher than un-staged co-firing for the same biomass thermal share in the fuel blend. It was found that the addition of biomass has a positive effect on carbon burnout under the optimum conditions that were determined in the study. A 10% biomass blending ratio (BBR) was found to be optimum for air-staging conditions. When co-fired under optimum air-staged conditions, a 10% BBR of sugarcane bagasse (SBR), shea meal (SM), wood chips (WC), cotton stalk (CS) and sugarcane bagasse (SBT) in coal gave NO reduction of 49%, 51%, 53%, 60% and 72%, respectively.