Biomass Co-firing Research Articles

NO formation during co-combustion of coal with two thermally treated biomasses

The combustion behavior of biomass as a fuel varies dependent on source of the raw material, but also on the type of pre-treatment. In this work steam exploded and torrefied woody biomass were studied with respect to NOx formation in co-firing experiments. Most of the reported data is based on small scale experiments and simulations. In this work, however, have three different cases been investigated experimentally in a 1.5MWth combustor supported by reaction simulations. One case corresponds to firing 100% Utah bituminous coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Two of the cases was also studied in a utility scale 1.3 GWth industrial boiler. In both units did the case with pure coal result in the highest amount of NO formed, which was expected due to the higher amount of fuel-bound nitrogen in the coal, as compared to the biomass fuels. The fuel analyses indicate that the nitrogen content is the same in the two investigated biofuels. However, the amount of NO formed differed. Gas composition measurements reveal that the partitioning of volatile nitrogen species (HCN and NH3) varies between the biomass co-firing cases. This was investigated further using detailed reaction simulations and is suggested as the main reason for the observed difference in NO formation.

MILD combustion of co-firing biomass and pulverized coal fuel blend for heterogeneous fuel NO and PM2.5 emission reduction

A sawdust and bituminous coal blend is studied experimentally under MILD combustion conditions, and the PM2.5 emissions of MILD combustion are measured. MILD combustion is established by low-temperature preheated air in a 200-kW pilot-scale furnace. The pilot tests consist of the conventional flame combustion through a swirl nozzle, MILD combustion through symmetrical double straight nozzles, and MILD combustion through an asymmetrical single straight nozzle. Compared to conventional swirl flame combustion, the MILD combustion of the sawdust blend can reduce the fuel-NO emission by at least 45.5%. The results further reveal that the PM2.5 emissions are decreased by over 37%. The burnout rates of the sawdust blend MILD combustion are higher than 95%. Considering the in-furnace distribution, low NO and PM2.5 emissions, and high burnout rate, MILD combustion is an effective way to utilize biomass fuel blends on a large scale. This work extends fuel adaptation of MILD combustion to biomass blends. Compared with previous MILD combustion studies, this investigation further confirms the inhibitory effect of MILD combustion on the formation of fine particles.

Co-firing of coal and biomass under pressurized oxy-fuel combustion mode: Experimental test in a 10 kWth fluidized bed

• Pressurized oxy-fuel combustion of coal/biomass in a fluidized bed is successful. • Stable, pressurized, oxy-fuel combustion mode using coal/biomass can be realized. • Increased pressure leads to higher combustion efficiency and CO 2 enrichment. • Increased pressure has the advantages of reducing CO, NO x , and SO 2 emissions. • Increased pressure makes the fly ash particles finer with surface more cracked. Pressurized oxy-fuel combustion (POFC) of solid fuels in fluidized beds possess the potential for CO 2 capture at low cost. However, the practical experience of oxy-coal combustion in pressurized fluidized beds (PFB) is still very limited, and there is a lack of attempts on the co-firing of coal and other fuels. In this study, the co-firing of coal and biomass in a POFC mode at a 10 kW th PFB was tested. The dynamic behaviors of the start-up process and combustion mode switching were investigated. The effects of key operating parameters, including combustion pressure ( P ), biomass blending ratio ( M b ), and excess oxygen coefficient ( α ), on the temperature distributions, CO 2 enrichment and conversion, pollutant emissions (CO, NO X , SO 2 ), and solid residues were methodically studied. The results show that the stable, pressurized, and oxy-fuel combustion mode with coal and biomass mixtures as fuels can be successfully realized in a fluidized bed. Increasing P and M b not only conduces to better temperature distribution, more CO 2 enrichment in flue gas, and higher combustion efficiency but also has the advantage of reducing NO x and SO 2 emissions by over 30%. In the oxy-fuel PFB, the positive effect of α on the combustion performance is more significant than that under atmospheric conditions. As P increases, the fly ash surface is more cracked, and the particle size distribution of fly ash decreases, while the bottom slag surface is smoother. Besides, the increase in P results in a decreased specific surface area and cumulative pore volume but an increased average pore diameter in fly ash.

Numerical modelling of the coal phase-out through ammonia and biomass co-firing in a pilot-scale fluidized bed reactor

The co-firing of ammonia (NH3) with coal has raised awareness, boosting NH3 research and development on its use and deployment as a sustainable fuel. Recent advancements point towards the co-firing of coal with biomass and NH3 as a state-of-art strategy to phase-out coal from coal-based power stations. The implementation of NH3 to the coal-biomass fuel mix allows not only to decarbonize coal-fired processes but also reduces biomass exploration costs to avoid feedstock availability disruption while increasing the power station production efficiency. Moreover, such a strategy brings an alternative player into the environmentally friendly power mix portfolio, accelerating the coal phase-out from electricity production. However, the use of NH3 for power generation still presents some research gaps. Thus, this study delivers a 2D Eulerian-Lagrangian numerical model to describe the co-firing of coal with biomass and NH3 in a pilot-scale fluidized bed reactor. The numerical model is validated against experimental data on coal and biomass combustion to assess the model's accuracy. The coal, biomass, and NH3 co-firing ratios are varied to the point where coal is gradually reduced from the fuel mix, and its effect on the combustion processes is broadly investigated to determine the biomass and NH3 impact on the reactor's emissions. Overall, the use of both biomass and NH3 showed to broadly reduce carbon and NO emissions from coal-fired energy systems, emphasizing the potential addressed to biomass as an alternative to coal and NH3 as an effective carbon-neutral fuel of the future.

Three-dimensional modeling study of the oxy-fuel co-firing of coal and biomass in a bubbling fluidized bed

In this work, the co-firing of biomass and coal in an oxy-fuel bubbling fluidized bed combustor is numerically explored using a multiphase particle-in-cell reactive model. After model validation, the complex in-furnace phenomena and thermochemical properties are thoroughly studied. The results show that the lateral injection of solid fuels and secondary gas flow results in the non-uniform distributions of gas-solid fluxes and gas products. Segregation makes sand particles concentrate in the bottom region. Particle mass decreases axially, corresponding to the coal in the medium region and biomass in the upper region. Higher oxygen concentration leads to higher gas temperature and lower gas density attributed to the enhanced oxidation reactions. Elevating superficial gas velocity causes a lower gas temperature, higher gas density, lower CO2 and H2O concentrations because of the reduced residence time of gas-solid flow. A larger portion of primary gas flow causes the reduced O2 concentration, increased H2O concentration, but unchanged CO2 concentration in the lower region.

Numerical simulation of combustion of sulfide- biomass concentrate ingredients and contaminants in copper furnace smelting

Co-firing biomass and fossil fuels in industrial furnaces is a suitable way to reduce the environmental impact of human activities with acceptable investment. In this paper, the results of numerical simulation co-firing of sulfide concentrate and three auxiliary fuels, including gasoil, kerosene, and sawdust biomass, are compared in the flash furnace copper smelting. For modeling of turbulent flow and combustion, RNG, k-ε model, and probability density function model (pdf) have been used, respectively. This study has been carried out to investigate the furnace temperature and combustion pollutants distribution. The numerical simulation results show that the flame temperature resulting from the combustion of diesel fuel and sawdust as auxiliary fuel is the highest and lowest, respectively. In biomass combustion, despite that the flame temperature is low, but the NOx mass fraction increases because there is nitrogen in the sawdust chemical composition. Also in sawdust combustion, the oxygen content is high, the SO2 and SO3 sulfur pollutants increase in the high temperatures regions of the furnace and the lower temperature of the auxiliary fuel burner, respectively. Because SO2 is formed at high temperatures (> 1273K), oxygen-rich and SO3 species are produced at relatively low temperatures with excess oxygen. The amount of CO emissions in sawdust combustion is much lower than the amount of combustion of diesel and oil. In the peak of the flash furnace for sawdust and diesel auxiliary fuels, the temperature is 2.29E+03 K, and the distribution of NOx, CO2, O2, SO2, and SO3 are 1.51E-04, 9.72E-02, 2.33E-03, 1.71E-01 and 2.45E-02 respectively.

Plant conversions and abatement technologies cannot prevent stranding of power plant assets in 2\u2009\xb0C scenarios

Continued fossil fuel development puts existing assets at risk of exceeding the capacity compatible with limiting global warming below 2 °C. However, it has been argued that plant conversions and new abatement technologies may allow for a smoother transition. We quantify the impact of future technology availability on the need for fossil fuel power plants to be stranded, i.e. decommissioned or underused. Even with carbon capture and storage (CCS) and bioenergy widely deployed in the future, a total of 267 PWh electricity generation (ten times global electricity production in 2018) may still be stranded. Coal-to-gas conversions could prevent 10–30 PWh of stranded generation. CCS retrofits, combined with biomass co-firing, could prevent 33–68 PWh. In contrast, lack of deployment of CCS or bioenergy could increase stranding by 69 or 45 percent respectively. Stranding risks remain under optimistic technology assumptions and even more so if CCS and bioenergy are not deployed at scale.

Environmental and socio-economic implications of woody biomass co-firing at coal-fired power plants

We apply a detailed power sector model to explore the near-term role of woody biomass co-firing at existing coal facilities in the Eastern US in the decarbonization of US electricity generation. We evaluate five public policy interventions: a biomass co-firing subsidy, two carbon emissions fees, and two clean energy standards. Treating woody biomass as a carbon neutral feedstock, we find co-firing weakly supports decarbonization. However, policies subsidizing co-firing can delay retirement of coal facilities and reduce generation from nuclear, natural gas, wind and solar. Consequently, corresponding sector-wide emissions of CO2 and SO2 may increase (slightly) due to greater utilization of coal plants including relatively inefficient facilities. We assume NOX emissions increase due to generation efficiency losses, but this remains uncertain. Due to higher emissions, a biomass subsidy for co-firing yields small (near zero) economic welfare losses, while in contrast other policies advance decarbonization and yield significant welfare gains. We find justification for biomass use from a local perspective based on first-order impacts on employment and economy activity, but less so air quality.

Effects of Cofiring Coal and Biomass Fuel on the Pulverized Coal Injection Combustion Zone in Blast Furnaces

CO2 emissions are a major contributor to global warming. Biomass combustion is one approach to tackling this issue. Biomass is used with coal combustion in thermal power plants or with blast furnaces (BFs) because it is a carbon-neutral fuel; therefore, biomass provides the advantage of reduced CO2 emissions. To examine the effect of co-firing on pulverized coal injection (PCI) in BFs, two coals of different ranks were blended with the biomass in different proportions, and then their combustion behaviors were examined using a laminar flow reactor (LFR). The PCI combustion primarily functions as a source of heat and CO to supply the upper part of the BF. To create a similar PCI combustion environment, the LFR burner forms a diffusion flat flame with an oxygen concentration of 26% with a flame temperature of ~2000–2250 K at a heating rate of 105 K/s. The combustion characteristics, such as the flame structure, burning coal particle temperature, unburned carbon (UBC), and CO and CO2 emissions were measured to evaluate their effect on PCI combustion. With the increase in the biomass blending ratio, the brightness of the volatile cloud significantly increased, and the particle temperature tended to decrease. The fragmentation phenomenon, which was observed for certain coal samples, decreased with the increase in the biomass blending ratio. In particular, with an increase in the biomass blending ratio, the optimum combustion point occurred, caused by the fragmentation of coal and volatile gas combustion of biomass.

Potential of biomass and coal co-firing power plants in Indonesia: a PESTEL analysis

Biomass co-firing technology for coal power plants has been widely applied in developed countries. The government of Indonesia is currently encouraging the implementation of biomass co-firing to achieve the target of 23% new and renewable energy (NRE) share in the national energy mix by 2025. Although only a few technical issues are left on the implementation of biomass co-firing in coal power plants, the challenges for the large-scale application and the long-term sustainability of the technology still need to be investigated. To identify and overcome these challenges, this paper applies the Political, Economic, Social, Technological, Environmental, and Legal (PESTEL) framework to analyze the business prospects for biomass co-firing for coal power plants. There is potential for biomass co-firing in 114 units of coal power plants with a total capacity of 18.1 GW spread across various locations in Indonesia. As a consequence, it requires around 9 million tons of biomass per year. This huge potential market of biomass opens opportunities for people to participate in supplying the raw materials. The biomass market as co-firing fuels will push agricultural and industrial waste management to be used more efficiently. The biomass supply chain needs to be well developed so that the biomass supply can be sustainable at an economically feasible price, to ensure that electricity prices generated from utilities are affordable for the public. The technical specifications for biomass need to be standardized. The 10% co-firing acceleration of the total coal power plant capacity, or equivalent to around 1.81 GW, can directly contribute to the achievement of the NRE target for the electricity sector and simultaneously reduce greenhouse gas emissions. The government needs to prepare related supporting instruments such as technical regulations, technological and economic aspects, and policy support.

Computational fluid dynamics modeling of biomass co-firing in a 300 MW pulverized coal furnace

Biomass energy is one of the most accessible and readily available carbon-neutral energy options as a RES. It is regarded as a viable alternative fuel for coal combustion, particularly for biomass co-firing with pulverized coal, with numerous applications. The CFD can provide reasonably accurate solutions to complex thermo-chemical-fluid interactions, which is useful for understanding the design or retrofit of boilers and can save time, money, and effort. In this study, a CFD simulation of a 300 MW pulverized coal boiler with biomass co-firing was performed to investigate the impact of biomass co-firing with coal, considering the biomass co-firing ratio, mixing effect, and feeding temperature. The results show that the flow field in the furnace does not change significantly under different bio-mass blending ratio. Biomass co-firing can reduce peak temperatures in the furnace and make the temperature distribution more uniform. The concentration of unburned carbon in the furnace decreases as the biomass blending ratio increases. Furthermore, biomass blending has a significant impact on nitrogen oxide reduction, with NOx emissions reduced by 20% and 28%, respectively, when the biomass blending ratio is 15% and 30%. The change of parameters inside the furnace caused by the reduction of biomass powder feeding temperature about 80 K is not significant. On the other hand, co-firing biomass with coal, reduces the risk of biomass spontaneous combustion while maintaining the furnace combustion stability and boiler combustion efficiency. The optimum ratio of biomass co-firing ration is deduced in this study is up to 20%.

Efekti primjene prirodnog gasa pri sagorijevanju čvrstih goriva u letu – reburning tehnologija

The energy transition basically implies a phased and significant reduction in the use of fossil fuels, until the final cessation of use in the near future. Renewable energy sources and alternative fuels are an increasingly important part of the energy transition. At the same time, it is necessary that energy systems increase energy efficiency and environmental acceptability. In this regard, great efforts are being made to expand the portfolio of primary fuels in existing large energy systems, e.g. thermal power plants. Therefore, today in large boilers, in order to reduce NOx emission, staged air supply for combustion is inevitably used as the primary measure in the furnace (air staging). In addition to the previous measure, there are many examples of staged fuel supply to the combustion zone (fuel staging), and still a small number of examples of the use of third or additional fuel, e.g. application of biogas or natural gas in combustion of pulverized solid fuels (reburning technology). General, these measures simultaneously increase the efficiency of primary energy conversion from fuel and reduce the emission of undesirable components into the environment. The results of this paper show the extent to which the effects of the use of natural gas in the co-firing of Bosnian coal and waste wood biomass are expressed. In this process there is an additional reduction of NOx in proportion to the share of gas - at a process temperature of 1350 °C and at 10% of the energy content of gas in combustion with coal, compared to emissions without additional fuel, recorded reduction of NOx emissions by more than 250 mg/mn 3.

EXPERIMENTAL STUDY ON BED-TO-TUBE HEAT TRANSFER COEFFICIENTS IN BUBBLING FLUIDIZED BED

The overall bed-to-tube heat transfer coefficients of the blends of Lafia-obi coal and coconut shells have been investigated in a bubbling fluidized bed combustor. Experiments were performed at five different particle sizes of coal (5, 10, 15, 20 and 25 mm) and five different particle sizes of coconut shells (2, 6, 10,14 and 18 mm) for different blend proportions of 10%, 20%, 30%, 40% and 50%. Results obtained showed that the overall bed-to-tube heat transfer coefficient decreased with increasing coconut shell particle size in the blends. Combined effects of high radiation from large particle size of coal (25 mm) and high convection heat from small particle size of coconut shell (2 mm) at blend proportion of 10 and 50% produced the maximum bed-to-tube heat transfer coefficient. Due to the importance of heat exchange in the fluidized bed, it is observed that the contribution of biomass co-firing with coal is significant, hence, co-firing at optimal particle size and biomass blend ratio is imperative for achieving higher bed-to-tube heat transfer in the fluidized bed boiler.

A coal-fired power plant integrated with biomass co-firing and CO2 capture for zero carbon emission

A coal-fired power plant integrated with biomass co-firing and CO2 capture for zero carbon emission

Economics of co-firing rice straw in coal power plants in Vietnam

As governments forced electricity producers to use more renewable energy sources, over a hundred thermal power plants in high-income countries turned to biomass as a partial or complete replacement for coal. Is the co-firing technology appropriate for Vietnam? To assess the technology we build an integrated model simulating the economics, environmental and social implications of blending 5% of rice straw in two existing coal power plants in Vietnam. The business value of co-firing is positive –straw is cheaper than coal– but not large enough to motivate the stakeholders. The external social benefit of co-firing –reduced air-borne pollution– are several times larger than the business value. Within that external benefit, the social value of avoided PM2.5 and NOx emissions dominates the social value of avoided CO2 emissions. The net job creation effect is positive: collecting straw creates more employment than using less coal destroys. This is the first technology assessment of co-firing biomass in coal power plants in Vietnam and one of the first for a subtropical middle-income country. The study only considers rice straw, and it does not address the role of government nor the biomass market functioning. The price of coal is the primary determinant of co-firing business value. There is an empirical economic justification for a public intervention to promote co-firing biomass in Vietnam, mainly as a way to reduce open-field straw burning. Local air quality goals, rather than greenhouse gas reduction policy, can justify such regulations.

Investigating the Palm Oil Mill Wastes Properties for Thermal Power Plants

Renewable energy is a reliable solution for addressing global warming and fossil fuel depletion issues. Due to the abundance of biomass resources, such as palm oil wastes, which are currently underutilised, this is an opportunity for Malaysia to seize and implement this renewable energy solution for power generation. Palm oil mill wastes, such as empty fruit bunch (EFB), palm mesocarp fibre (PMF), and palm kernel shell (PKS), are worth to be investigated as a possible feedstock for combustion in thermal power plants. Co-combustion or co-firing of biomass in coal-fired thermal power plants offers a significant potential to reduce harmful emissions and represents a low cost and low-risk method. This paper aims to review and compare existing biomass thermal combustion technologies globally to evaluate the potential of utilising palm oil waste with coal. Before undergoing various pretreatment options, it is necessary to understand the feedstock characteristics for thermal power plant combustion. It is recommended to implement the combustion of palm oil wastes with coal in Malaysia to reduce harmful pollution. Based on the findings, Malaysia appears to be on the right track to optimise the use of palm oil wastes for electricity generation. The enhanced usage will reduce the negative impact of greenhouse gas (GHG) emissions.

Potential And Characteristics Of Eichhornia Crassipes Biomass And Municipal Solid Waste As Raw Materials For RDF In Co-Firing Coal Power Plants

The government has regulated the use of RDF biomass for coal co-firing in power plants. This paper examines biomass (Eichhornia Crassipes and municipal solid waste) characteristics and its potential use as RDF for co-firing in CPP. The method includes the analysis of the composition, supply of raw materials, and biomass characteristics. These results will compare with the coal’s characteristics in CPP. The density of Eichhornia Crassipes in Lake Tondano was 25 kg/m2, with the wet mass of 45,350 tons. The results of the Eichhornia Crassipes sample test for parameters of moisture content, volatile matter, ash content, fix carbon and gross calorific value have a value range of 93%, 5.8-7.1%, 60.21-63.5%, 17.9-22%, 11.4% and 2681-3068 kcal/kg. Amurang CPP uses coal with 4200 kcal/kg calories as much as 1056 tons/day. The co-firing target of 5% requires 52.8 tons of biomass per day. The existing Eichhornia Crassipes biomass in Lake Tondano only supplies the CPP for 62 days. MSW typically has calorific values and moisture with Eichhornia Crassipes biomass, about 3766-4194 kcal/kg and 31.7-87.1%. The use of MSW to cover the lack of Eichhornia Crassipes will ensure the sustainability of the supply of biomass raw materials in the co-firing program at CPP.

Pilot-Scale Experimental Study on Impacts of Biomass Cofiring Methods to NOx Emission from Pulverized Coal Boilers—Part 2: NOx Reduction Capability through Reburning versus Cofiring

In this study the NOx reduction capability of reburning three biomasses (i.e., wood pellet, torrefied biomass, and empty fruit bunch) via 12 cases (i.e., four reburning ratios for every biomass) is investigated in a 1 MWth-scale pilot-scale furnace. These reburning cases are compared with 12 cofiring cases presented in the Part 1 paper on a consistent basis. It is found that, for every cost to purchase and prepare biomass, reburning technology provides significantly better NOx abatement performance than cofiring (up to 3.4 times). NOx reduction effectiveness as high as 4.9 could be achieved by reburning, which means the percent of NOx abatement could be 4.9 times higher than the percent of reburning ratio. It is found that the highest NOx reduction per thermal unit of biomass happens at the lowest reburning ratio, and increasing the reburning ratio leads to a reduction in NOx abatement effectiveness in an exponential decay manner. Unlike cofiring technology, reburning was found to have little dependence on the fuel characteristics, such as fuel ratio or fuel-N, when it comes to NOx abatement potential.

Stackelberg game based co-firing biomass with coal under carbon cap-and-trade regulation

Coal-fired power industry is under enormous pressure to accomplish carbon emission reduction targets. This paper proposes a bi-level multi-objective model for co-firing biomass with coal under carbon cap-and-trade regulation which considers a leader-follower Stackelberg game between the authority and the coal-fired power plants. The upper level regards social welfare maximization and allocation satisfaction maximization as its multiple objectives, while the lower level attempts to maximize the profits of each coal-fired power plant. The inherent uncertainty prompts the motivation for employing fuzzy set theory to characterize the uncertain parameters and determine their exact values. A case study from Shandong Province, China is provided to demonstrate the practicality and efficiency of the optimization model. [Formula: see text]-constraint method and interactive algorithm are used to solve the model, and furthermore the solutions associated with different free carbon emission quota levels and minimal allocation satisfactions have been generated to examine the influences. Based on the analysis and discussion, the methodology can meet the carbon emission reduction goals and transit to a lower-carbon power generation. It also assists the decision makers to develop desired quota allocation strategy in accordance with their attitudes and actual conditions.

Modelling the co-firing of coal and biomass in a 10 kWth oxy-fuel fluidized bed

The oxy-fuel co-firing of solid fuels (such as coal, biomass, and solid waste) in fluidized beds is one of the most promising technologies for the industrial application of CO2 capture and waste disposal. However, both the practical experimentation and numerical simulations for elucidating co-firing in an oxy-fuel fluidized bed are still limited. In this study, a multiphase particle-in-cell scheme based on a 3D Eulerian–Lagrangian model was further developed following our previous research on oxy-fuel co-firing in a micro fluidized bed (Powder Technol. 2020, 373, 522–534). The refined JL 4-step mechanism for the CO-CO2 homogeneous reactions, the heterogeneous reactions of char oxidation and gasification, the heterogeneous reactions of NO and N2O formation from char-N, and the self-desulfurization effect were comprehensively considered. The improvement of the models was verified through the continuous operation of 10 kWth oxy-fuel fluidized bed tests (Fuel 2021,286,119,312; Energy Fuels, 2020, 34, 7373–7387), and the effects of the biomass blending ratio (Mb) on co-firing characteristics were discussed. It was found that the improvements could enhance the adaptability of the models to the oxy-fuel atmosphere, and the accurate prediction of NO, N2O, SO2. With an increase in Mb, the main reaction zone expanded or moved up along the riser height, and the volume of the high-temperature area increased, which promoted the burnout of particles and CO2 emission when Mb is 50%. The high volatility of biomass increased O2 consumption and CO concentration at the upper part of the riser, reduced N2O formation, and had a significant impact on NO reduction. The low sulfur content and high Ca/S ratio of the biomass considerably reduced the SO2 concentration. The simulation results also provided helpful information for the design and operation control of oxy-fuel co-firing of coal and biomass in a fluidized bed, such as the oxidant supply in different areas and grades, appropriate increase in the riser height, and reasonable adoption of Mb.