Coal Biomass Research Articles

Co-combustion of biomass and bituminous coal in a fluidized two-bed reactor

ABSTRACTThe combustion of hazelnut shells and bituminous coal was studied in a novel reactor with two disks, supporting two fluidized beds located one above the other. The reactor allows for the study of the impact of the fuels’ vertical arrangement in the combustion zone on SO2 emission. The biomass and coal were combusted in separate beds or as a mixture. The gas species concentrations were measured. A major drop in the SO2 coal emission was observed when the coal was combusted underneath the biomass bed, and a minor one, when above.

Porosity development and reactivity changes of coal–biomass blends during co-pyrolysis at various temperatures

While co-firing of coal and biomass represents an inexpensive, efficient, short-range future method to incorporate more renewable fuels into our energy generation portfolio, we know little about how U.S. domestic coals and biomasses behave together. Computational fluid dynamics models are routinely used to model combustion of solids in packed and fluidized beds, for which porosity changes are a key variable to predicting heterogeneities in transport and fuel reactivity. This work probes the changes in carbon contents, thermal reactivities, surface areas, and porosities as a function of blend ratio and pyrolysis temperature for a series of Pennsylvania coal and feed corn stover biomass blends. There is a fairly linear trend between both percent biomass in a blend and pyrolysis temperature with volatile matter content of the char; this additive nature of the blended streams does not extend to surface area and porosity. Surface areas (measured by N2 adsorption isotherms) peaked for the pure coal and 10wt% biomass peaks around 600°C, and for the 20 and 50wt% biomass and pure biomass between 600 and 750°C. The surface area decreases for all samples when the pyrolysis temperature reaches 900°C. Generally, higher temperatures led to enhanced microporosity across all fuels and blends, though this was not a linear trend. Of keen interest to co-firing scenarios was the disappearance of segregated oxidation behavior of the coal–biomass blends at pyrolysis temperatures as low as 300°C, suggesting that co-firing could be improved by preheating the comingled fuels and low temperatures before their introduction into the boiler.

Coal–biomass mixing characteristics in a bubbling fluidized bed of Geldart A particles

In an effort to assess fluidization of coal–biomass mixtures, experiments and numerical simulations were used to better understand the dynamics in terms of mixing and bed characteristics. The computational platform MFiX was employed to simulate the particle–particle interactions of coal–biomass mixtures and compare the predictions with experimental data. The mixtures included sub-bituminous coal and hybrid poplar wood, which both are classified as Geldart A particles. Three mass ratio mixtures of 90:10, 80:20, and 70:30 coal:poplar wood were studied, and pressure drop and bed height for various gas inlet velocities were analyzed and compared to the experiments, which were in good agreement. It was found that the bed with 10% poplar wood showed characteristics consistent with a bed of coal and the bed with only 30% poplar wood was similar to a bed of poplar wood. A quantitative analysis of the mixing index confirmed that as the poplar wood mass ratio increased, the quality of mixing improved, with an average mixing index of 62%. Therefore, reasonable amounts of biomass can be added with coal without adverse effects of segregation or elutriation.

Co-firing coal and biomass blends and their influence on the post-combustion CO2capture installation

Co-firing of biomass with coal for energy production is a well-known technology and plays an important role in the electricity sector. The post-combustion capture integrated with biomass-fired power plants (Bio-CCS) seems to be a new alternative for reducing greenhouse gas emissions.This study refers to the best known and advanced technology for post-combustion CO 2 capture (PCC) based on a chemical absorption in monoethanolamine (MEA). The co-firing of hard coal with four types of biomass was investigated using a laboratory fixed bed reactor system. The comparison of gaseous products emitted from the combustion of coal and different biomass blends were determined using gas chromatography.Research proved that co-firing of biomass in fossil fuel power plants is beneficial for PCC process. It may also reduce the corrosion of CO 2 capture installation. The oxygen concentration in the flue gases from hard coal combustion was comparable with the respective value for a fuel blend of biomass content of 20% w/w. It was also noted that an increase in biomass content in a sample from 20 to 40 % w/w increased the concentration of oxygen in the flue gas streams. However, this concentration should not have a significant impact on the rate of amine oxidative degradation.

Assessment of the Low Heat Values of Plant Biomass, Peat and Fossil Coal Based on Technical Analysis

Assessment of the Low Heat Values of Plant Biomass, Peat and Fossil Coal Based on Technical Analysis

Assessment of the Low Heat Values of Plant Biomass, Peat and Fossil Coal Based on Technical Analysis

Assessment of the Low Heat Values of Plant Biomass, Peat and Fossil Coal Based on Technical Analysis

Circulating Fluidized Bed Gasification: Status, Challenges and Prospects in Indian Perspective

Objective: The present work relates the need for change and how Circulating Fluidized Bed (CFB) technology could prove a better alternative than the existing gasifiers in India. Background/Analysis: India is an energy deficit nation although it has rich coal reserves and biomass diversity. India ranks 3rd in world coal production, but it is low in grade comprising of high ash content. Biomass present in abundance includes bio-residue like bagasse, rice husk and saw dust beside other prominent crops that are found in India. Gasification technology is widely accepted way of harnessing these abundant energy resource. Findings: Presently conventional fixed bed gasifiers are installed in different regions of the country but this is gradually becoming obsolete. CFB gasification is at present an emerging technology for harnessing this vast resource of biomass and coal efficiently and environment friendly in India. It has evolved as an environment friendly technology for utilizing different of carbonaceous fuels like peat, lignite, biomass etc., for producing fuel gas with improved energy conversion ratio. A comprehensive survey has been conducted to study the CFB gasifiers and gasification processes in CFB so that it can be designed for scale-up and direct use in existing and upcoming related industries in India. This paper analyzes the feasibility of adopting the circulating fluidized bed technology for utilization of low grade coal and biomass available in India. Novelty/Applications/Improvements: Road map for adoption of CFB gasification technology for decentralized rural power production in India along with its future scope has been discussed.

Techno-economic analysis of direct coal-biomass to liquids (CBTL) plants with shale gas utilization and CO2 capture and storage (CCS)

In this paper, techno-economic analysis of direct coal biomass to liquids (CBTL) plants is performed in Aspen Process Economic Analyzer (APEA) using high fidelity process models developed in Aspen Plus for four different configurations of direct CBTL plants. Results from the economic model are validated with the data in the open literature, if available. Sensitivity studies are conducted to evaluate the impacts of key investment parameters, design parameters, and potential government-subsidized credits on the main economic measures including net present value (NPV), internal rate of return (IRR), break-even oil price (BEOP) and equivalent oil price (EOP). Using the North America 2015 pricing basis in APEA, this study shows that the BEOP of direct CBTL processes ranges from $56.9/bbl to $80.5/bbl for large scale (50,000bbl/day) plants and from $77.3/bbl to $97.5/bbl for small scale (10,000bbl/day) plants. It is observed that integrating a carbon capture and storage (CCS) unit to the direct CBTL process can increase the BEOP by about 10%, while utilization of the cheap and abundant shale gas (especially in the continental US) can make the direct liquefaction processes considerably more attractive than the indirect CBTL processes.

The effect of CO on coal–biomass co-gasification with CO2

In this study, co-gasification of coal and biomass chars with CO2 in the presence of CO was investigated at three different temperatures: 850, 875, and 900°C. A coal–biomass (bituminous-pineapple sawdust) mixture with a mass ratio of 1:1 was used for devolatilization and co-gasification. Random pore model was employed to determine the kinetic coefficient from experimentally obtained carbon conversion data. The Langmuir–Hinshelwood (L–H) equation, which has been widely used in literatures to describe the relationship between kinetic coefficient of the gasification and partial pressures of reacting gases, effectively represented the inhibition effect of CO on char–CO2 gasification. The kinetic parameters of the L–H equation were acquired from the experimental data. The activation energy (E) and pre-exponential factor (A) of each kinetic parameter of L-H equation were obtained using the Arrhenius equation. CO inhibition effect was more powerful in the Char-CO2 co-gasification of the mixed sample compared to those in the unmixed samples. Further, for each sample, the inhibition effect was stronger at lower temperature owing to a smaller number of active sites.

Process modeling of direct coal-biomass to liquids (CBTL) plants with shale gas utilization and CO2 capture and storage (CCS)

Direct coal liquefaction (DCL) technologies have been commercially demonstrated for producing transportation fuels from non-petroleum sources. However, significant amount of hydrogen is required in the DCL process due to the low H/C ratio in coal. As a result, DCL processes are usually associated with a high level CO2 emission from hydrogen production units. Hence, direct coal biomass to liquids (CBTL) processes with CO2 capture and storage (CCS) and shale gas utilization are proposed in this work as an option for reducing CO2 emission. In this study, the focus is on process simulation and calculation of material and energy balances of novel direct CBTL plants, which can be used as a basis for further studies, such as optimization, techno-economic analysis and life-cycle analysis. In this process, coal with moderate amount of biomass is converted into syncrude through reaction with H-donor solvent and gaseous hydrogen in a catalytic two-stage liquefaction unit. Hydrogen required for the liquefaction and product upgrading unit is produced from the liquefaction residue partial oxidation unit and the shale gas steam reforming unit or from the coal/biomass/residue co-gasification unit. Different CCS technologies are evaluated to achieve 90% overall carbon capture if high extent of CO2 capture is considered. Results of individual plant sections are validated with the existing data, if available. Sensitivity studies have been conducted to analyze the effects of key operating parameters and design parameters, such as the sources of hydrogen, CCS technologies, extent of CCS, and biomass/coal ratio. Key measures studied in this work include the fuel yield, thermal efficiency, CCS penalty and CO2 emission.

Distribution, sources, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface water in industrial affected areas of the Three Gorges Reservoir, China.

Water samples were collected from wastewater treatment plant (WWTP), drain water (DW), major tributaries (MT), and main course of the Yangtze River (MY) in areas of three industrial parks (IPs) in Chongqing city in the Three Gorges Reservoir (TGR). Sixteen EPA priority polycyclic aromatic hydrocarbon (PAH) pollutants were quantified to identify the effects of industrial activities on water quality of the TGR. The results showed that 11 individual PAHs were quantified and 5 PAHs (naphthalene (Nap), acenaphthylene (Acy), benzo[k]fluoranthene (BkF), indeno[1,2,3-cd]pyrene (InP), and benzo[g,h,i]perylene (BgP)) were under detection limits in all of the water samples. Three-ring and four-ring PAHs were the most detected PAHs. Concentrations of individual PAHs were in the range of not detected (nd) to 24.3ng/L. Total PAH concentrations for each site ranged from nd to 42.9ng/L and were lower compared to those in other studies. The mean PAH concentrations for sites WWTP, DW, MT, and MY showed as follows: DW (25.9ng/L) > MY (15.5ng/L) > MT (14.0ng/L) > WWTP (9.3ng/L), and DW contains the highest PAH concentrations. Source identification ratios showed that petroleum and combustion of biomass coal and petroleum were the main sources of PAHs. The results of potential ecosystem risk assessment indicated that, although PAH concentrations in MT and MY are likely harmless to ecosystem, contaminations of PAHs in DW were listed as middle levels and some management strategies and remediation actions, like strengthen clean production processes and banning illegal sewage discharging activities, etc., should be taken to lighten the ecosystem risk caused by PAHs especially risks caused by water discharging drains.

Kinetic study on coal–biomass mixed char co-gasification with H2O in the presence of H2

The coal–biomass mixed char co-gasification with H2O in the presence of H2 was investigated under atmospheric conditions using a tube furnace and gas analyzer. Various partial pressures of H2O and H2 were tested within a temperature range of 825–900°C. Bituminous coal, pineapple sawdust, and a mixture of these two having a mass ratio of 1:1 were used to prepare chars. Random pore model was utilized to explain the experimental results. The results demonstrated that the inhibition effect of H2 on char-H2O gasification can be described using the Langmuir–Hinshelwood (L–H) equation. The inhibition effect on the mixture sample was more intense than on the pure samples. The L–H equation kinetic parameters were acquired and expressed in an Arrhenius equation form to determine the pre-exponential factor and activation energy.

Oxygen enriched co-combustion of biomass and bituminous coal

ABSTRACTThe oxy-fuel co-combustion behavior of two herbaceous biomass species (Bermuda grass and cornstalk) with bituminous coal was investigated by thermal gravimetric analysis (40°C/min). The incorporation of Bermuda grass or cornstalk could improve combustion indices of the bituminous coal. Once blending the biomass with bituminous coal, ignition temperatures of blends could be advanced by about 100–170°C. With increasing the oxygen concentration or blending ratio, the comprehensive performance index of the most blends and their parent samples increased. For the 80%grass/20%coal blend, there was a strong synergistic effect in its parent samples at 60% oxygen concentration.

Techno-Economic Analysis of a Novel Indirect Coal–Biomass to Liquids Plant Integrated with a Combined Cycle Plant and CO2Capture and Storage

The indirect coal to liquids (CTL) plant based on gasification and Fischer–Tropsch (FT) technology is technically feasible, but it is plagued with high CO2 emission in comparison to the petroleum-based fuel production processes. Addition of a moderate amount of biomass to the feed and inclusion of CO2 capture and storage (CCS) technology to the indirect CTL process can reduce its environmental footprint, but at the cost of higher capital investment as well as larger operational penalty. In this study, a techno-economic analysis of a novel indirect coal–biomass to liquids (CBTL) plant with CCS is performed using Aspen Process Economic Analyzer based on a process model developed in Aspen Plus. This paper has evaluated the impact of key investment parameters, such as raw material cost, project contingency, and process capacity, on the economic measures, including net present value, internal rate of return, payback period, and break-even oil price. In addition, the impacts of technology choices for product up...

Life-Cycle Assessment of coal–biomass based electricity in Chile: Focus on using raw vs torrefied wood

In this article, the environmental impacts associated to cofiring coal with forest biomass for electricity production in Chile are analyzed for: (i) untreated pine pellets and (ii) torrefied-pretreated pine pellets. Results show that energy production from cofiring coal/untreated wood pellets or coal/torrefied pellets, featured significant reductions in environmental impacts, as compared with pure coal plants. Indeed, reductions in acidification (28–26%), abiotic depletion (15–7%), eutrophication potential (15–12%), global warming potential (16–6%), photochemical oxidation (28–23%), human toxicity (17–15%), terrestrial ecotoxicity (12–9%), and marine aquatic ecotoxicity (17–15%) were obtained when untreated or treated pellets were used as a substitute for coal. Moreover, the environmental profile of torrefied pine evidenced its low impact per energy unit, in most of the studied categories except for eutrophication and marine aquatic ecotoxicity, for which the harvesting, logistic chain and torrefaction processes were the most important contributors.

Co-gasification of coal–biomass blended char with CO2 and H2O: Effect of partial pressure of the gasifying agent on reaction kinetics

This short communication reports the results of an experimental study that is an expansion of two previous studies (Jeong et al., 2014, 2015). In this study, mixtures of coal and biomass with different mass ratios were co-gasified with CO2 or H2O. Five different partial pressure conditions between 0.2 and 0.6bar were tested for both gasifying agents. Random pore model was used to interpret the carbon conversion data. Pre-exponential factors and reaction orders of CO2 and H2O gasifications were determined using the Arrhenius equation and activation energies obtained in the two previous studies.

Influence of biomass addition on Jincheng coal ash fusion temperatures

The ash fusion temperatures (AFTs) of Jincheng (JC) coal, two kinds of biomass (cotton stalk (CS) and sargassum natans (SA)) and various coal–biomass mixtures were investigated in this study. Fluid temperatures (FT) were found 1531°C, 1534°C and 1428°C for JC, CS and SA ash respectively, which were higher than the normal operating temperature of entrained bed gasifier. However, the FTs of JC and CS mixture ash were lower than that of either single JC or CS ash, which showed a minimum value of 1292°C with 80% CS, and the FTs of JC and SA mixture ash showed the similar trend with a minimum value of 1258°C when SA proportion was 40%. At high temperature, refractory minerals were presented in three respective ashes, which were mullite of JC ash, lime and periclase of CS ash, merwinite and akermanite of SA ash. And they could support the ash skeleton structure. Interaction between coal and biomass ash occurred during blending ash melting process, which formed co-eutectic and decreased the AFTs. The relationship between the ash fusion temperatures and the ash chemical composition was also discussed.

Modeling and Analysis of an Indirect Coal Biomass to Liquids Plant Integrated with a Combined Cycle Plant and CO2Capture and Storage

A model of an indirect coal biomass to liquids (CBTL) plant integrated with CO2 capture and storage (CCS) and a combined cycle plant has been developed in Aspen Plus 7.3.2. In the CBTL plant, syngas produced in the gasifier is sent to a water-gas shift (WGS) reactor to obtain the desired H2/CO ratio in the syngas for Fischer–Tropsch (FT) synthesis. The product upgrading section is configured to satisfy the desired product specifications. CO2 generated in the syngas and syncrude production units are captured by different CO2 capture technologies. Fuel gas and steam generated in the plant are used as either utilities or sent to the combined cycle plant for power generation. The CBTL plant includes a novel integrated hydrotreating unit, which has the potential to reduce both operating and capital costs of the product upgrading section, in comparison to conventional separate hydrotreating units for gasoline and diesel. Impacts of a number of key input and operational variables, such as the steam/carbon ratio ...

Second-generation sustainability: Application of the distributed activation energy model to the pyrolysis of locally sourced biomass–coal blends for use in co-firing scenarios

While first generation biofuels paved the way for a vision of a renewable energy future, their competition for arable land limited widespread applicability. Second generation fuels, made from a variety of carbonaceous wastes, are considerably more “sustainable” in a land competition sense, but require a higher degree of processing to extract energy. Here we extend the idea of second-generation sustainability by investigating blends of coal and biomasses found within 20miles of coal-fired power stations in the Northeast United States for use in co-firing scenarios that would limit long-range transport of biomass. A commercial high volatile bituminous Pennsylvanian coal was blended at 90, 80, and 50wt% with one of three biomasses: feed corn stover from a local farm, brewer’s spent grains from Redhook Brewery, or cocoa shells from the Lindt chocolate factory. The Distributed Activation Energy Model was applied to analyze the pyrolysis kinetics of the solid fuels and blends, yielding activation energies as a function of mass fraction conversion ranging from 304 to 522kJ/mol for coal, 164 to 304kJ/mol for the biomasses, and 218 to 530kJ/mol for the coal–biomass blends. Overall, the peak reaction rates and temperatures for the primarily biomass decomposition stages were linearly correlated with the percent biomass in the blend. Such an additive scheme did not represent the blends’ kinetics, instead over-predicting the activation energies. Synergy was noted between the fuels, in that the biomass does appear to be promoting the devolatilization of the coal at lower temperatures.

Pyrolysis Characteristics of Coal, Biomass, and Coal–Biomass Blends under High Heating Rate Conditions: Effects of Particle Diameter, Fuel Type, and Mixing Conditions

The pyrolysis characteristics of two Chinese coals, two biomass materials, and their blends were investigated by both experimental and numerical methods. Single particles of the coal and biomass were prepared for the pyrolysis experiment through grinding and pressing, while the blended particles were made by mixing the coal and biomass powder with different ratios before the pressing. Sample particles pyrolyzed in a single-particle reactor system, with the time history of the particle temperature and mass recorded. The analysis of the measured pyrolysis data of the coal, biomass, and coal–biomass blends indicate the absence of a synergistic effect between the coal and biomass pyrolysis. A numerical method coupling the chemical percolation devolatilization (CPD) model with a particle energy equation was employed to analyze the pyrolysis process. The model prediction agreed well with the experimental data for different particle diameters, fuel types, and blend mixing conditions. The fact that the co-pyrolysis of blended coal–biomass particles is well-predicted by the simple addition of the individual pyrolysis characteristics of its components also corroborates the lack of synergistic interactions. These findings will be useful for the co-combustion modeling of coal–biomass blends.