Combustion Plants Research Articles

Dioxin concentrations and congener distribution in biomass ash from small to large scale biomass combustion plants.

Biomass plays a pivotal role in global energy production, with a significant share allocated for industrial heat and power generation. The combustion of biomass generates biomass ash, which is widely utilized as a fertiliser. However, concerns arise regarding the presence of dioxins in biomass ash, which may limit its continued use. Dioxins are toxic compounds listed under the Stockholm Convention due to their persistence and detrimental effects on human health and the environment. This study investigates the dioxin content in biomass ashes produced in various combustion plants with a capacity of 1-50MWth in Estonia, where biomass is widely used for heating and power production. The research encompassed samples from nine biomass combustion plants with varying technical parameters considering both bottom and fly ash. Dioxin concentrations were determined for 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), and 12 dioxin-like PCBs (PCBs). The results indicate that dioxin TEQ content in all samples was well below the European Union's (EU) POP Regulation limit of 5µg TEQ/kg, with most values being at least tenfold lower. However, some samples failed to meet the EU Fertilising Products Regulation's threshold of 20ng TEQ/kg. Notably, fly ash exhibited higher dioxin concentrations than bottom ash. While PCBs were in significant concentrations, PCDDs dominated the overall dioxin TEQ content. This study provides essential insights into the dioxin content in biomass ash and its correlation with current EU regulatory limits. It also highlights the complex distribution of dioxin congeners, particularly PCBs, within biomass ash, emphasizing the continued research's importance.

Characteristics, Sources Analysis, and Environmental Impacts of VOCs Based on Photochemical Loss in Summer in Zhengzhou

To clarify the pollution characteristics and sources of atmospheric VOCs in Zhengzhou City in the summer, multi-site offline sampling and laboratory analyses of atmospheric VOCs in Zhengzhou were carried out in August 2022. The observed and initial VOC volume fraction levels, OFP, SOAFP, and sources were compared. During the study period, the average values of three-site observation and initial φ（VOCs） during the study period were （31.83 ±13.51）×10-9 and （35.92 ±15.30）×10-9,respectively. Olefins （52.5 %） and aromatic hydrocarbons （29.7 %） were the components with a higher photochemical loss rate, and the spatial variations of the observed TVOCs concentration at each site were： Zhengzhou University （ZZU） > Gangli Reservoir （GLR） > Jingkaiqu （JKQ）, and the concentrations of alkanes and OVOCs at each site were higher. Olefins and aromatic hydrocarbons were the components that contributed greatly to the formation of O3 and SOA. Motor vehicle sources, solvent-use sources, and industrial sources were the main contributing sources of atmospheric VOCs in Zhengzhou. Compared with the source analysis results based on the initial concentration, the contribution rates of motor vehicle sources, industrial sources, and solvent use sources were relatively high, and the contribution rates of combustion sources, plant sources, and oil and gas volatilization sources were relatively low.

Comparative Analysis of Primary and Secondary Emission Mitigation Measures for Small-Scale Wood Chip Combustion

The objective of this study is to systematically investigate not only the influence of different additive types—beyond the much-considered case of aluminum-silicate-based additives—but also to carry out an additional comparison between primary and secondary emission mitigation measures during small-scale wood-chip combustion. Hence, combustion trials are realized within a 33-kW combustion plant. Pine wood chips additivated with 1.0 wt%a.r. of four additives have shown promising emission reduction effects in the past; namely kaolin (i.e., aluminum-silicate-based), anorthite (i.e., aluminum-silicate- and calcium-based), aluminum hydroxide (i.e., aluminum-based), and titanium dioxide (i.e., titanium-based). In addition to the primary mitigation measure (i.e., (fuel) additivation), an electrostatic precipitator (ESP) as a common secondary mitigation measure for total particulate matter (TPM) reduction is used for comparison. In addition to standard analyses (e.g., gravimetric determination of TPM emissions), an extended methodology (e.g., characterization of the elemental composition and ultrafine particle fraction of TPM emissions) is applied. The results show that the additivation of wood chips with kaolin and anorthite can lead to an operation of the combustion plant in compliance with the German legal TPM limit values by undercutting the absolute emission level achievable by the ESP. Additionally, kaolin and anorthite achieve significant reductions in carbon monoxide (CO) emissions, while kaolin simultaneously, and similarly to ESP, also leads to a shift in the particle size number distribution of PM emissions towards coarser particles. All additives show a significant reduction of potassium (K) emissions by the formation of high-temperature stable K compounds in the resulting ashes.

Failure Analysis of Corrosion Pit on Outer Wall of Membrane Wall Pipe

Abstract Flue gas pipework is a critical component of a flue gas treatment system, mainly transporting the flue gases produced by a combustion plant from the source to the vent. Flue gas pipework is vital in all applications, such as thermal storage gas stoves, heaters, and gas water heaters. However, due to negligent management during the use of piping. Corrosion pits were created in several places on the outer wall of a membrane wall pipe located on the flue gas side of the membrane wall pipe. The external circulation medium of the membrane wall pipe is mainly high-temperature flue gas, and the internal circulation medium is water. This paper determines the causes of the corrosion pits by macroscopic observation, metallographic microstructure analysis, scanning electron microscopy, and energy dispersive spectroscopy (EDS). It was found that the outer wall of the flue gas sidewall pipe of the failed part was covered with reddish-brown rust, wide and shallow corrosion pits were observed, and the detection area of the inner surface of the pits had a high ‘S’ content. To reiterate, it was concluded that the cause of the corrosion pits was the flue gas dew-point corrosion.

Stable isotope compositions, source apportionment and transformation processes of carbonaceous aerosols in PM10 in the urban city of Hyderabad, India

This study apportions sources of carbonaceous aerosols using isotopic characteristics of total carbon (TC) and elemental carbon (EC) in PM10 aerosols using filter-based CTO-375 method for pre-monsoon (summer), post-monsoon, and winter (2019–2021) over Hyderabad, India. Highest secondary organic carbon, SOC (primary organic carbon, POC) of 13.78 ± 10.25 (7.87 ± 2.48) μg/m3 was during post-monsoon 2020 (2019), while lowest was 8.90 ± 5.55 (4.18 ± 0.92) μg/m3 during pre-monsoon 2021 (post-monsoon 2020), respectively. Average effective carbon ratio (ECR) > 1 indicates dominance of light scattering aerosols during pre-monsoon and post-monsoon. δ13CTC and δ13CEC varied from – 28.1 to – 24.7 ‰ (avg. – 26.5 ± 0.7) and - 32.5 to – 24.6 ‰ (avg. – 27.4 ± 1.1), indicating contribution from C3 plant burning and liquid fuel combustion. Positive value of δ13COC – δ13CEC and heavier δ13CTC, along with gradual enrichment in δ13CTC and δ13CEC from December 2020 to March 2021, suggested photochemical aging of carbonaceous aerosols. Lighter δ13CTC and OC/EC > 4 for all seasons indicates dominance of biomass burning (wood and crop residue burning), photochemical oxidation and secondary organic aerosol (SOA) formation. The tropical study experiences dominance of lighter δ13CEC compared to subtropical, high latitude regions.

Low-carbon optimal dispatch strategy of power systems considering the combined operation of oxy-fuel combustion and electric hydrogen production

ABSTRACT Oxy-fuel combustion technology offers a promising solution for achieving nearly zero carbon dioxide emissions from coal-fired units, presenting a viable path toward low-carbon dispatch. This study establishes a simulation model for the low-carbon operation of power systems, focusing on the integrated operation of an oxy-fuel combustion plant and electric hydrogen production. By incorporating oxygen generated from electric hydrogen production into the oxy-fuel combustion plant, the primary objective is to minimize system operation costs. Through simulation analysis and verification, a comparative scenario is constructed to evaluate performance. The simulation results indicate that the joint operation approach yields significant benefits. In comparison to separate operation, the joint operation strategy leads to a reduction of approximately 7.38% in total system costs, 18.79% in operating costs, and 23.56% in carbon emissions. This integrated approach not only achieves lower carbon emissions but also results in reduced overall system costs.

Design and Performance Analysis of a Small-Scale Prototype Water Condensing System for Biomass Combustion Flue Gas Abatement

This article outlines the design and performance of a flue gas condensation system integrated with a biomass combustion plant. The system comprises a biomass plant fuelled by wood chips, generating flue gases. These gases are condensed via a double heat exchanger set-up, extracting water and heat to reduce concentrations of CO, CO2, and NOx while releasing gases at a temperature close to ambient temperature. The 100 kW biomass plant operates steadily, consuming 50 kg of wood chips per hour with fuel energy of 18.98 MJ/kg. Post combustion, the gases exit at 430 °C and undergo two-stage cooling. In the first stage, gases are cooled in a high-temperature tube heat exchanger, transferring heat to air. They then enter the second stage, a flue gas/water heat exchanger, recovering sensible and latent thermal energy, which leads to water condensation. Flue gas is discharged at approximately 33 °C. Throughout, parameters like the flue gas temperatures, mass flow, fuel consumption, heat carrier temperatures, and water condensation rates were monitored. The test results show that the system can condense water from flue gas at 75 g/min at 22 °C while reducing pollutant emissions by approximately 20% for CO2, 19% for CO, 30% for NO, and 26% for NOx.

Understanding adhesion induced by calcium compounds at 900 °C using model particles

In waste and biomass combustion plants, ash adheres to the inside of the combustors and surfaces of air heaters, etc., accumulating over time and causing operational problems due to the deposited ash layer. Here, we evaluated the adhesion properties of calcium-rich ash using synthetic ash. Specifically, we investigated the role of Ca-Al in ashes. The adhesion of Ca-Al synthetic ash and mixed ash of Ca-Al and SiO2, which is included in ash and utilized as a bed material in fluidized-bed combustion systems, was investigated. Adhesion was found to increase when three conditions were met: Ca/Al molar ratio >1, SiO2 coexistence, and 900 °C. The increase in tensile strength of the powder bed corresponded to shrinkages in volume, specific surface area, and total pore volume, suggesting solid phase sintering as the cause of increased adhesion. Adding alumina nanoparticles to the highly adherent sample successfully suppressed the adhesion increase.

Pressurized oxy-fuel combustion with sCO2 cycle and ORC for power production and carbon capture

The pressurization of oxy-fuel combustion presents the opportunity to recuperate more latent heat from the flue gas within the boiler. This study proposed a coal-fired pressurized oxy-fuel combustion plant coupled with the sCO2 Brayton cycle for simultaneous power production and carbon capture. Two configurations, i.e., sCO2 recuperator split and sCO2 bottom cycle, are conceived to fully exploit the flue gas heat from the boiler. Waste heat from various sources, including the air separation unit, the CO2 compression and purification unit and the sCO2 cycle, are recuperated by the organic Rankine cycle (ORC) to augment the net power efficiency. Sensitive analyses, including the turbine parameters, the recuperator split ratio, and the ORC parameters, are conducted to optimize the design and operation conditions of the plant. The plant net power efficiency ranges between 39.4 % and 42.9 %, inclusive of CO2 compression. The levelized cost of electricity (LCOE) is calculated, and the LCOE results are in the range of 101.60 $/MWh and 106.07 $/MWh for different configurations. These findings suggest the system's viability for future coal-fired plant with carbon capture.

Relevance and prediction of N2O in small-scale multi-fuel biomass furnaces using primary NOx reduction measures

The relevance of the greenhouse gas N2O was investigated in two small-scale biomass combustion plants, a 30-kW fixed bed and a 70-kW moving grate furnace, both of which use double air staging. Furthermore, the 70-kW furnace was simulated with ideal reactor models, applying a detailed nitrogen chemistry mechanism to gain insights into N2O formation mechanisms that occur during double air-staged combustion.The experimental and simulated results confirm the existence of correlations between CO, NOx and N2O. For all investigated fuels, N2O reached the highest levels (increase of up to 300 %) when high CO and low NOx concentrations were present. Therefore, caution is advised when looking for minimum NOx emissions, due to the risk of having high N2O emissions, an aspect which is often overlooked.A deeper analysis of the N2O formation mechanisms revealed that N2O is mainly generated from HCN in the oxidation zone and it is thermally dissociated at high temperatures. Finally, a comparison between the results of both plants showed that the concern about high N2O emissions at minimum NOx concentrations is not a reactor-specific problem; therefore, it is necessary to ensure that CO and N2O are kept at a low level during NOx reduction with primary measures.

A comparative ammonia recovery study of solid wastes discharged from rice husk gasifi cation and combustion plants

A comparative ammonia recovery study of solid wastes discharged from rice husk gasifi cation and combustion plants

Optimum operation condition of fluidized-bed homogeneous crystallization technology for the recovery of carbon dioxide captured in flue gas

The decarbonization of industry, particularly in "hard-to-decarbonize" sectors like combustion plants, poses a significant challenge due to the limited availability of low-carbon options. Carbon capture, utilization, and storage (CCUS) offers a promising solution to this challenge. Chemical precipitation is one method of converting CO2 into precipitated mineral carbonates, which can be stored and converted into valuable materials. This study explores fluidized-bed homogeneous crystallization (FBHC) technology for recovering carbonate from simulated CO2-enriched flue gas, resulting in stable calcium carbonate granules. Factors such as pH, carbonate concentration, reactor type, and reactants significantly impact carbonate removal and crystallization efficiency. Optimal conditions were found at 0.086 M input carbonate concentration, pH 9.0, and using a two-stage reactor, achieving 99.9 % removal and 93.2 % crystallization efficiency. Potassium-based absorbents yield higher crystalline intensity and larger granules compared to sodium. X-ray diffractometry confirms the composition of calcium carbonates, demonstrating FBHC's effectiveness for CO2 capture and storage. Utilizing calcium carbonate granules for carbon dioxide sequestration can potentially reduce emissions, pending resolution of investment and feasibility challenges.

Optimizing waste-to-energy conversion: Unveiling the potential of unsupervised clustering through the new HOM classification system

The correct and informative classification of a given fuel is essential in optimizing the utilization of the fuel. While the physical properties of the fuels provide more complete information about the fuel, conventional fuel classification systems (CSs) are based on the fuels’ source or origin. In this study, the novel HOM CS is proposed from the data of fuels’ ultimate and proximate analysis and HHVs by utilizing k-means clustering where the number of clusters are optimized. The obtained clusters are investigated in comparison with the conventional CSs by using several methods such as contingency matrices, PCAs, ternary plots, and Van-Krevelen diagrams. Finally, the clusters are appropriately named and the HOM CS is distinctly defined. The proposed CS can be used in informative class assignment of any kind of fuel including fuel mixtures or fuels of unknown source or origin which are generally categorized vaguely as “composite-streams”, “wastes”, or “others” in conventional CSs. Thus, by the implementation of the new CS, these materials can now be categorized in a manner that provides insight into their specific application possibilities. This categorization can assist researchers in determining the most efficient conversion methods especially for the waste-to-energy processes including combustion, gasification, and biogas plants.

Chemical Speciation, Leaching Behavior, and Environmental Risk Assessment of Trace Elements in the Bottom Ash from Biomass Power Plant.

Biomass combustion for power generation stands as a pivotal method in energy utilization, offering a promising approach for renewable energy utilization. However, the substantial volume of slag produced by biomass burning plants poses environmental challenges, impeding sustainable energy practices. This article systematically studies the characteristics of ash generated from typical biomass direct combustion power plant ash and analyzes the chemical composition, trace element content characteristics, leaching characteristics, and chemical forms of biomass bottom ash. Furthermore, it assesses the environmental ecology and bioavailability of trace elements in bottom ash using the ecological risk assessment method and RAC method. The results demonstrate that the biomass bottom ash contains plant nutrients, such as K, Ca, Mg, and P, while the content of harmful trace elements is lower than the relevant Chinese standards. In dissolution experiments, the leaching rate of nearly all elements remains exceptionally low, primarily due to the distribution of trace elements within the lattice structure of stable minerals. Trace elements predominantly exist in the residual phase, Cu and Zn primarily found in organic compounds and sulfide bound states, while other elements mostly exist in the form of iron manganese oxide bound states. Ecological risk assessment indicates a significant risk level for Cd, contrasting with the slight risk associated with other elements. RAC results indicated no ecological risk of all of the trace elements. Consequently, the utilization of bottom ash in agricultural and forestry soils is deemed to be viable. These findings serve as a crucial foundation for biomass bottom ash resource utilization and underpin the sustainable utilization of biomass energy.

Use of solid recovered fuels for heat production - analysis of Czech legislation

The article is about solid recovered fuel (SRF) and its legislation possibilities to use them as a fuel in heating plants. This solution is quite popular because it brings solution of two very problematic tasks – the decreasing of waste landfilling and the end of fossil fuel (especially coal) combustion. Due to these arguments are there many producers which offer SRF (often in the pellets form) to conventional heating plants. However heating plant have flue gas cleaning technologies, which are able to combustion SRF and keep current emissions limits, the usage of SRF is forbidden for them. The reason is in the classification of origin material as a waste and the permission and limits as a waste combustion is required. The criteria and limits for waste combustion are much stricter and for heating plants is very difficult to reach them if it is possible. The article is about view of Czech legislation, where some of law had different interpretation about waste material and SRF combustion. Article compare requirements and results for SRF from waste and SRF from waste biomass. The interpretation is described from a view of waste, air protection, IPPC, EU ETS and support of renewable energy sources law based on Czech a EU law documents. The most important is origin of SRF. When the SRF is made by waste (municipal or industrial) all laws must assess final combustion technology as waste combustion technology, the support for renewable energy sources is not allowed (except biodegradable municipal waste) and CO2 emission permit is not required. With new regulation No. 169/2023 Coll. is possible to combustion SRF, which is based on waste biomass from forestry and agriculture. The permits and limits for combustion plants are same as biomass combustion, support for renewably energy sources is possible and CO2 emission permits are not required. Investment to SRF combustion technology is not advantageous, because purchase prize of SRF will be higher than standard waste but requirements for technology will be same. Meaning of the newest legislation was not in possibilities to use of more SRF in heating plant, but bring waste and air protection law into accord, because some of waste biomass was possible to combust, however it was waste by waste law.

Atmospheric aerosol chemistry and source apportionment of PM10 using stable carbon isotopes and PMF modelling during fireworks over Hyderabad, southern India

This study examined the influence of fireworks on atmospheric aerosols over the Southern Indian city of Hyderabad during festival of Diwali using mass closure, stable carbon isotopes and the EPA-PMF model. Identification of chemical species in day and night time aerosol samples for 2019 and 2020 Diwali weeks showed increased concentrations of NH4+, NO3−, SO42−, K+, organic carbon (OC), Ba, Pb and Li, which were considered as tracers for fireworks. PM10 source apportionment was done using inorganic (trace elements, major ions) and carbonaceous (organic and elemental carbon; OC & EC) constituents, along with stable isotopic compositions of TC and EC. K+/Na+ ∼1 and K+nss/OC > 0.5 indicated contribution from fireworks. High NO3−, NH4+, Na+, Cl− and SO42− suggested the presence of deliquescent salts NaCl, NH4NO3 and (NH4)2SO4. TAE/TCE >1 suggested H+ exclusion, indicating possible presence of H2SO4 and NH4HSO4 in the aerosols. Ba, Pb, Sb, Sr and Fe increased by 305 (87), 12 (11), 12 (3), 3 (2) and 3 (4) times on Diwali nights, compared to pre-Diwali of 2019 (2020), and are considered as metallic tracers of fireworks. δ13CTC and δ13CEC in aerosols closely resembled that of diesel and C3 plant burning emissions, with meagre contribution from firecrackers during Diwali period. The δ13CEC was relatively depleted than δ13CTC and δ13COC. For both years, δ13COC-EC (δ13COC - δ13CEC) were positive, suggesting photochemical aging of aerosols during long-range transport, while for pre-Diwali 2019 and post-Diwali 2020, δ13COC-EC were negative with high OC/EC ratio, implying secondary organic aerosols formation. High toluene during Diwali week contributed to fresh SOA formation, which reacted with precursor 12C, leading to 13C depletions. Eight-factored EPA-PMF source apportionment indicated highest contribution from residue/waste burning, followed by marine/dust soil and fireworks, while least was contributed from solid fuel/coal combustion.

Spatial distribution, environmental behavior, and health risk assessment of PAHs in soils at prototype coking plants in Shanxi, China: Stable carbon isotope and molecular composition analyses

To investigate the environmental behavior of and carcinogenic risk posed by 16 priority-controlled polycyclic aromatic hydrocarbons (PAHs), soil samples and air samples from the coke oven top were collected in two prototype coking plants (named PF and JD). The PF soils contained more PAHs than the JD soils because the PF plant employed the side-charging technique and had a lower coke oven height. The soils from both plants contained enough PAHs to pose a carcinogenic risk, and this risk was higher in the PF plant. Data were collected on the source characteristic spectrum of stable carbon isotopic composition (δ13C) of PAHs emitted from the coke oven top (δ13C values of −36.02‰ to −32.05‰ for gaseous PAHs and −34.09‰ to −25.28‰ for particulate PAHs), and these data fill a research gap and may be referenced for isotopic-technology-based source apportionment. Diagnostic ratios and isotopic technology revealed that the coking plant soils were mainly influenced by the coking process, followed by vehicle exhaust; the soils near the boundary of each plant were slightly affected by C3 plant burning. For most PAHs [excluding fluoranthene, benzo(k)fluoranthene, indeno(1,2,3-c,d)pyrene, and dibenzo(a,h)anthracene], the dominant migration process was the net volatilization of PAHs from soil to air. In the PF plant, 13C was depleted in gaseous PAHs during volatilization.

Economical Operation and Hazardous Air Pollutant Emissions of Biodegradable Sludge Combustion Process in Commercial Fluidized Bed Plant

Waste sludge is characterized by high moisture, volatile compounds, toxic compounds, and ashes. The efficient operation of a commercial fluidized bed combustion (FBC) plant is important for reducing operational costs. We selected a commercial FBC plant for industrial waste sludge combustion to investigate the mass balance of the FBC process and the performance of the air pollution control device. Based on fuel analysis, the flow rate of incineration air was calculated as 4567 Nm3/h. After FBC combustion, the flow rate of the incineration gas increased to 8493.8 Nm3/h. Analysis of the heat balance showed that some heat potential was lost through leakage during the combustion process. The temperature of the incineration gas decreased to 200 °C at the inlet of the air pollution control device. According to the hazardous air pollutant emission testing of sampling points, the operation factors of lime slurry injection for SOx and HCl in the semi-dry reactor were 64.20 and 4.81 kg/h, respectively. In the wet scrubber, the operation factors of NaOH for SOx and HCl were 23.88 and 3.14 kg/h, respectively. At these operation factors, the available waste generation in the semi-dry reactor and wet scrubber was optimized to 76.6 and 42.57 kg/h, respectively.

The role of SRF in achieving the EU landfill targets in the Umbria Region, Italy

In December 2015, the European Commission published the circular economy package “Closing the loop - An European action plan for the Circular Economy” with four quantitative objectives: long-term recycling targets for municipal waste (55% in 2025, 60% in 2030 and 65% in 2035) and landfill target of 10% by 2030. In Umbria (Italy) 43% of waste are landfilled in 2020, so the region is far from the European target. Hence, it is significant to analyse different strategies to improve the waste management in the region. In particular, the main issue is how to reduce waste landfill in the most efficient way. The SRF and waste-to-energy approaches are the most interesting to study as a substitute for landfilling. In the communication “The role of waste-to-energy in the circular economy”, the European Commission clarifies the position covered by the different energy processes in the waste hierarchy and identifying the technologies with the highest potential in terms of efficient management of resources and environmental impact. Among the most efficient waste-to-energy technologies, the document mentions the gasification of recovered solid fuel (SRF) and co-incineration of the resulting synthesis gases in the combustion plant to replace fossil fuels in the production of electricity and heat and co-incineration in the cement production. The European Commission recognizes the important role of energy recovery in the transition to the circular economy, if this does not stop the improvement in recycling rates. In this paper, MSW management policy in Umbria (Italy) and possible solutions are discussed. The paper considers three scenarios in the management of MSW: i) direct combustion of residual waste in waste-to-energy plants; ii) combustion of SRF in waste-to-energy plants; iii) combustion of F-SRF in dedicated plants (cement plant). All three scenarios may be able to match the 10% landfill EU target.

Ways to reduce CO emissions in the polypropylene medical products disposal

A large number of polypropylene medical products require special disposal conditions. The most effective and simplest method is combustion. At the same time, it is necessary to minimize harmful emissions that inevitably arise when organizing this process. The paper presents the study results of the combustion rate and combustion completeness depending on the oxidizer supply conditions and the characteristics of the external electric field created in the combustion zone. The possibility of increasing the productivity and combustion plant environmental friendliness has been shown.