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Carbonization

Carbonization is the thermochemical process by which organic materials, such as plant matter or biomass, are converted into carbon-rich residues through pyrolysis or destructive distillation in the absence of oxygen, resulting in the loss of volatile components like water, hydrogen, and oxygen while increasing the carbon content.^[1]^[2] This process occurs naturally in geological contexts, notably during coalification, where accumulated plant debris in peat bogs undergoes progressive transformation under heat, pressure, and tectonic influences, advancing through stages from lignite to anthracite with escalating carbon concentrations—from about 65% in lignite, to 82–89% in bituminous coal, and over 90% in anthracite (dry, ash-free basis)—accompanied by dehydration and devolatilization.^[3] In paleontology, carbonization preserves delicate organic structures, such as leaves or insects, by reducing them to thin, stable carbon films through the expulsion of non-carbon elements as gases, often yielding detailed impressions in sedimentary rocks without altering the original shape.^[4] Industrially, carbonization is pivotal for producing materials like coke from coal, achieved by heating at 900–1,100°C in oxygen-limited environments to yield a porous, high-carbon fuel essential for steelmaking via the blast furnace process, alongside byproducts such as coal gas and tar.^[5] For biomass, such as wood or agricultural residues, slow pyrolysis at 400–700°C breaks down complex carbonaceous structures into elemental carbon and volatile compounds, generating charcoal or biochar valued for fuel, soil amendment, and carbon sequestration due to its stable, porous structure that enhances nutrient retention and microbial activity.^[6] Advanced variants, like hydrothermal carbonization, apply moderate heat (180–250°C) and pressure to wet feedstocks, mimicking natural coalification to produce hydrochar—a coal-like solid with high energy density—for waste valorization and renewable energy applications.^[7] These applications underscore carbonization's role in energy production, materials engineering, and environmental management, balancing resource efficiency with emissions control.

Definition and Principles

Definition

Carbonization is the thermochemical conversion of organic materials, such as biomass or coal precursors, into carbon-rich solid residues through pyrolysis or destructive distillation in an environment with limited or no oxygen, leading to the volatilization of non-carbon components and enrichment of fixed carbon content.^[1] This process differs from broader pyrolysis, which encompasses any thermal decomposition of organic matter without oxygen but does not specifically emphasize carbon residue production, and from gasification, which involves partial oxidation to primarily yield combustible gases rather than solids.^[2] The process typically occurs at temperatures ranging from 300°C to 1000°C, depending on the feedstock and desired product, resulting in a solid phase like charcoal or coke, alongside liquid byproducts such as tars and oils, and gaseous emissions including carbon monoxide (CO), hydrogen (H₂), and methane (CH₄).^[6] Unlike complete combustion, which fully oxidizes the material to carbon dioxide and water, carbonization preserves the carbon skeleton by restricting oxygen access, thereby avoiding total mineralization.^[8] Carbonization encompasses both natural geological processes and artificial industrial applications; in nature, it manifests as coalification, where ancient plant matter transforms into coal over millions of years under heat and pressure in sedimentary basins.^[9] Artificially, it includes the production of charcoal from wood in controlled kilns or coke from coal in ovens, serving as foundational steps in fuel and material manufacturing.^[10]^[11] The term "carbonization" derives from "carbon" combined with the suffix "-ization," denoting the act of forming carbon, and first appeared in scientific literature in the early 19th century (first known use in 1804), gaining prominence in the 19th century to describe coal processing techniques during the Industrial Revolution.^[12]^[11]

Chemical and Physical Principles

Carbonization involves a series of thermal decomposition stages that transform organic feedstocks into char, gases, and liquids through pyrolysis in an oxygen-limited environment. The process begins with preheating, where temperatures below 200°C facilitate the drying and evaporation of volatiles and moisture, preparing the material for subsequent reactions. This is followed by primary decomposition between 200°C and 500°C, characterized by devolatilization that releases tars, gases, and light volatiles through the breakdown of biopolymers. Finally, secondary reactions above 500°C promote char formation via cracking and repolymerization of intermediates, enhancing the carbon content of the solid residue.^[13]^[14] Chemically, carbonization entails endothermic thermal decomposition of polymeric components such as cellulose, hemicellulose, and lignin, requiring external heat input to drive bond cleavage and rearrangement. For instance, the decomposition of cellulose can be represented by the simplified reaction:

\text{C}_6\text{H}_{10}\text{O}_5 \rightarrow 6\text{C} + 5\text{H}_2\text{O} + \text{volatiles}

This reaction exemplifies the conversion of oxygenated biomass to carbon-rich char, water, and gaseous/liquid byproducts like CO and H₂O, with heat transfer playing a critical role in sustaining the endothermic process across particle surfaces.^[15]^[16] Physical parameters significantly influence the outcomes of carbonization, including temperature, heating rate, pressure, and residence time. Higher temperatures and longer residence times generally increase char yield by allowing more complete devolatilization and secondary cracking, while elevated pressure can suppress vapor release and promote solid retention. Slow heating rates favor higher char production, yielding up to 35% char from wood biomass, whereas rapid heating enhances liquid yields by minimizing secondary reactions.^[13] The process exhibits complexity due to heterogeneous reactions occurring at solid-gas and solid-liquid interfaces, compounded by catalytic effects from minerals in the feedstock ash, such as alkali metals that accelerate decomposition and alter product distribution. Yields vary with feedstock composition; for example, lignin-rich biomass produces more char than cellulose-dominant materials owing to lignin's aromatic structure resisting volatilization.^[17]^[18] The resulting char shows increased fixed carbon content, typically ranging from 50% to 90%, alongside a marked decrease in volatile matter, reflecting the enrichment of stable carbon structures. These properties are quantified through proximate analysis, where fixed carbon is calculated as 100% minus the sum of moisture, ash, and volatile matter percentages.^[19]^[20]

Historical Development

Ancient and Pre-Industrial Uses

Archaeological evidence indicates that the use of charcoal, produced through the carbonization of wood in hearths, dates back to approximately 30,000 years ago, when early humans in regions with limited wood access began controlling fire for warmth and cooking.^[21] This practice became widespread in ancient civilizations, where charcoal served as a critical fuel for metallurgy; for instance, Egyptians around 3000 BCE employed charcoal in furnaces to smelt copper and gold, enabling the production of tools, ornaments, and weapons.^[22] Similarly, the Greeks and Romans utilized charcoal extensively for iron smelting in bloomery furnaces from the 8th century BCE onward, heating iron ore with charcoal to produce workable blooms of iron.^[23] Traditional methods of carbonization relied on simple, low-tech setups such as earth pits or mound kilns, where hardwood stacks were partially buried or covered with soil and ignited to undergo pyrolysis in low-oxygen conditions, yielding approximately 20-25% charcoal by weight from the original wood mass.^[24] These techniques produced charcoal primarily for fuel in heating and cooking, but also for creating black pigments in art and as a medicinal agent to treat wounds and odors, as documented in Egyptian records from around 1500 BCE.^[25] The cultural significance of carbonization was profound, intertwining with societal needs and environmental management; in Europe, intensive charcoal production for ironworks contributed to widespread deforestation, reducing forest cover in areas like Scotland to just 4% by the mid-18th century.^[26] To sustain supplies, communities integrated carbonization with agriculture through coppicing, a practice dating to Neolithic times where trees were cut back to stumps to regrow shoots for periodic harvesting, balancing wood demand with woodland regeneration.^[27] On a pre-industrial scale, charcoal remained the sole carbon source for high-temperature processes, powering iron production in regions like ancient China from the 4th century BCE, where it fueled early blast furnaces for cast iron without the later adoption of coke.^[28] In Africa, traditional bloomery smelting using charcoal thrived from the 8th century BCE in sites like Ethiopia and expanded across sub-Saharan regions, supporting tool-making and trade economies reliant entirely on wood-derived fuel.^[29]

Industrial Advancements

The industrial advancements in carbonization commenced in the early 18th century when Abraham Darby pioneered the use of coke—derived from coal carbonization—for iron smelting in 1709 at Coalbrookdale, England, replacing scarce charcoal and enabling scalable production that fueled the Industrial Revolution.^[30] This breakthrough addressed the inefficiencies of wood-based charcoal, limited by widespread deforestation, and laid the foundation for coal's dominance in metallurgy. By the late 19th century, beehive ovens emerged in the United States and United Kingdom, offering improved control over the carbonization process through enclosed brick structures that heated coal to produce higher-quality coke more reliably than open-heap methods.^[31] In the late 19th and early 20th centuries, carbonization evolved toward by-product recovery systems, with slot-type coke ovens introduced around the 1910s to capture gases, tars, and other volatiles during coal heating, transforming waste into valuable chemicals and boosting overall efficiency.^[32] This innovation supported massive scale-up in the steel sector; by 1900, U.S. coke output exceeded 19 million short tons annually, primarily to meet iron and steel demands that had surged with industrialization.^[33] The transition from charcoal to coke in American iron production, occurring primarily between 1840 and 1880, was necessitated by severe forest depletion, which had rendered charcoal supplies unsustainable and shifted reliance to abundant coal resources.^[34] Further milestones in the 1920s included the broader implementation of slot ovens, which optimized carbonization yields through precise heating in narrow chambers, achieving up to 70% coke conversion from coal while minimizing emissions compared to earlier designs.^[35] Globally, these techniques spread to Japan during the Meiji era (1868–1912), where coke adoption at facilities like Yawata Iron Works integrated imported coal carbonization to modernize blast furnaces and drive rapid industrialization.^[36] Throughout the 20th century, automation advancements, such as computerized controls for oven heating and charging in battery systems, enhanced operational precision, reduced manual labor, and improved energy efficiency in large-scale coke production.^[37]

Carbonization Processes

Dry Pyrolysis Methods

Dry pyrolysis methods, a subset of thermal decomposition processes, involve heating carbonaceous feedstocks such as biomass or coal in an oxygen-limited or inert atmosphere to produce char or coke while minimizing combustion. This technique, often conducted at temperatures between 400°C and 1000°C, relies on controlled heating rates to drive off volatiles and concentrate carbon in the solid residue.^[15]^[38] In slow pyrolysis variants, heating rates of 0.1–10°C/min are employed to maximize solid char yield, typically achieving 25–35% from dry wood biomass, with the remainder forming gases and liquids.^[38]^[39] Equipment such as retorts, kilns, or ovens maintains the anaerobic conditions essential for carbonization, preventing oxidation and ensuring high-quality product formation.^[40] The transformation of wood into charcoal via dry pyrolysis proceeds through distinct stages: initial drying, carbonization, and cooling. During drying, moisture content is reduced from typical levels of 20–50% to below 10%, often at temperatures up to 100–200°C, to facilitate efficient heat transfer and avoid energy loss to evaporation.^[41] Carbonization follows at 280–500°C, where thermal decomposition breaks down hemicellulose, cellulose, and lignin, releasing volatiles like water vapor, CO, CO₂, and tars, while forming a porous char structure with 75–85% fixed carbon content.^[40]^[41] The final cooling phase, lasting 48 hours or more in airtight systems, prevents re-ignition and stabilizes the charcoal, yielding approximately 25–33% by dry weight from hardwoods like oak.^[40] Traditional Brazilian earth kilns, common for eucalyptus wood, operate batch-wise with yields around 20–25%, while modern retort systems achieve up to 35% yield through better heat recovery and continuous operation.^[42]^[43] Coke production from coal employs similar dry pyrolysis principles but at higher severities to suit metallurgical applications. Caking coals, which soften and bind during heating, are charged into ovens and pyrolyzed at 1000–1100°C for 15–20 hours, expelling 20–30% volatiles as coke oven gas and tar while forming a strong, low-reactivity coke mass.^[44]^[45] Yields reach 70–80% of the dry coal input, depending on coal rank and blend, with the resulting coke exhibiting high mechanical strength for blast furnace use.^[45] Horizontal slot ovens, arranged in batteries of 30–60 units, enable efficient heat transfer via wall conduction, contrasting with obsolete beehive designs that wasted byproducts through open combustion.^[45]^[32] Variations in dry pyrolysis include slow and intermediate regimes, differentiated by heating rates and residence times to tailor product distribution. Slow pyrolysis (0.1–1°C/min, hours to days at 400–600°C) prioritizes char maximization for applications like soil amendment or fuel, often in batch kilns.^[38]^[16] Intermediate pyrolysis (1–10°C/min, moderate times at 500–800°C) balances char (20–30% yield) with increased liquid and gas outputs, suitable for integrated biorefineries using continuous retorts.^[16] For coke, non-recovery beehive ovens historically operated at similar temperatures but with lower efficiency due to byproduct flaring, whereas modern horizontal ovens recover gases for energy reuse, enhancing overall process viability.^[32]^[45]

Hydrothermal Carbonization

Hydrothermal carbonization (HTC) is a thermochemical conversion process that transforms wet biomass and organic waste into a carbon-rich solid product known as hydrochar, along with process water and gaseous byproducts, by heating a biomass-water slurry under moderate temperatures and pressures.^[7] The process typically involves heating the slurry to 180–250°C under autogenous pressures of 10–40 bar for 0.5–8 hours, resulting in hydrochar yields of 50–80% on a dry basis, depending on feedstock and conditions.^[16]^[7] The mechanism of HTC occurs in subcritical water, where initial hydrolysis breaks down biomass polymers such as cellulose, hemicellulose, and lignin into simpler monomers, followed by dehydration and decarboxylation reactions that remove oxygen and hydrogen, leading to carbon enrichment.^[46] Maillard reactions between sugars and amino acids further contribute to the formation of spherical, aromatic structures in the hydrochar, enhancing its stability and uniformity. Compared to dry pyrolysis, HTC requires lower energy input because water acts as both a reaction medium and heat transfer agent, eliminating the need for feedstock drying and adapting pyrolysis principles to aqueous conditions.^[16] A key advantage of HTC is its ability to process high-moisture feedstocks, such as sewage sludge and food waste, directly without energy-intensive pretreatment, making it suitable for waste valorization.^[46] The resulting hydrochar typically contains 60–80% carbon and exhibits a higher heating value of 20–30 MJ/kg, comparable to sub-bituminous coal, enabling its use as a biofuel precursor.^[16]^[7] HTC was first described in 1913 by Friedrich Bergius, who developed it to mimic natural coal formation under controlled conditions.^[47] In the 2020s, European pilot projects, such as those by HTCycle and TerraNova Energy in Germany, have scaled HTC to process tons of sewage sludge per day for biofuel production, demonstrating commercial viability through multi-batch and continuous reactor systems.^[48]^[47]

Applications

Traditional Fuel and Material Production

Charcoal, produced through the carbonization of wood via dry pyrolysis, serves as a versatile traditional fuel and material, primarily for household and industrial applications. Globally, charcoal production reaches approximately 55 million tons annually as of 2022, with the majority used as a fuel for cooking and heating in developing regions, where it provides an accessible energy source for over 2 billion people.^[49] In metallurgical processes, charcoal acts as a reductant, notably in silicon production, where its high carbon content and reactivity facilitate the reduction of silica in electric arc furnaces, contributing to the manufacture of silicon metal for alloys and electronics. Additionally, charcoal is a key precursor for activated carbon, which is further processed to enhance its adsorptive properties for filtration and purification. Coke, derived from the carbonization of coal, remains the cornerstone of traditional iron and steel production, functioning as both a fuel and reducing agent in blast furnaces. Global metallurgical coke production stands at around 726 million tons per year as of 2022, essential for reducing iron ore to pig iron, with each ton of steel requiring approximately 0.4 tons of coke. Its desirable properties, including low reactivity and high strength after reaction (CSR >60%), ensure structural integrity under the high-temperature, CO2-rich conditions of the furnace, minimizing degradation and optimizing gas flow for efficient smelting. This reliance on coke underscores its integral role in the steel industry, which consumes over 70% of global production.^[50] Beyond fuels, carbonization yields specialized materials like carbon black, bone char, and carbon fibers. Carbon black, obtained from the incomplete combustion or thermal decomposition of oil or wood-derived hydrocarbons, is widely used as a reinforcing filler in rubber products such as tires, enhancing durability and abrasion resistance, and as a pigment in inks for printing applications due to its intense black color and fine particle size. Bone char, produced by carbonizing animal bones at high temperatures, is employed in sugar refining as a decolorizing and deashing agent, adsorbing impurities from cane sugar syrup to achieve the clarity of white refined sugar, a process still utilized in much of the global sugar industry. Carbonization is also essential in the production of carbon fibers, where polymer precursors like polyacrylonitrile are heated in an inert atmosphere at 1000–1500°C to form high-strength, lightweight filaments used in advanced composites for aerospace, automotive, and sporting goods applications.^[51] Economically, the charcoal market was valued at approximately $8 billion in 2023, driven by demand in energy and industrial sectors, while the metallurgical coke market, closely tied to steel production, exceeded $340 billion in the same year, reflecting its foundational importance to global manufacturing.

Modern Uses in Energy and Environment

In modern energy applications, hydrochar produced through hydrothermal carbonization (HTC) serves as a solid biofuel, particularly in pellet form for co-firing in coal power plants, offering a renewable alternative with higher heating values typically ranging from 20 to 25 MJ/kg.^[52] This energy density makes hydrochar suitable for direct substitution in existing infrastructure, reducing reliance on fossil fuels while maintaining combustion efficiency comparable to sub-bituminous coal.^[53] Additionally, carbonization processes like pyrolysis yield bio-oils that act as blendstocks for biodiesel, enhancing fuel stability and performance when integrated into conventional diesel engines through hydrotreating.^[54] Carbonization plays a key role in waste management by converting high-moisture organic wastes, such as sewage sludge and food waste, into hydrochar via HTC, achieving volume reductions of up to 70% and minimizing landfill use.^[55] The resulting hydrochar stabilizes waste, reduces pathogen content, and enables energy recovery, while process liquors can be repurposed as fertilizers. Furthermore, activated carbon derived from agricultural residues through pyrolysis or activation is widely used for water purification, effectively adsorbing contaminants like heavy metals and organic pollutants due to its high surface area exceeding 1000 m²/g.^[56] Environmentally, biochar from slow pyrolysis of biomass is applied as a soil amendment to enhance fertility, retain water, and sequester carbon, with a global technical potential estimated at 2.6 Gt CO₂ equivalent per year.^[57] This long-term storage in soils mitigates climate change by preventing CO₂ release from decomposing biomass. Recent innovations in the 2020s include HTC of algal biomass to produce hydrochar biofuels, leveraging algae's rapid growth and high lipid content for yields up to 25 MJ/kg while treating wastewater.^[58] Carbonized biomass, particularly biochar, also serves as a heterogeneous catalyst in biodiesel production, improving transesterification yields by over 90% and enabling recyclable, low-cost processes from feedstocks like waste oils.^[59]

Safety and Environmental Considerations

Occupational Health and Safety

Workers in carbonization operations, such as coke oven and charcoal kiln processes, face significant occupational hazards primarily from the release of toxic gases, particulate matter, and flammable volatiles during thermal decomposition. Carbon monoxide (CO) and hydrogen sulfide (H2S) are among the most prevalent gases, with H2S concentrations in raw coke oven gas reaching up to 1000 ppm, posing risks of acute respiratory distress and neurotoxicity at levels above 100 ppm.^[60] Tar and smoke emissions contribute to chronic respiratory issues, including irritation of the eyes, nose, and lungs, often manifesting as chronic cough among charcoal production workers exposed to wood smoke for extended periods.^[61] Additionally, the volatile components in coke oven gas, which include hydrocarbons with a lower explosive limit of 4%, present explosion risks during charging, pushing, or venting operations.^[62] Historical accidents, such as fires in 19th-century beehive coke ovens due to uncontrolled ignition and gas leaks, underscore these dangers, with documented incidents causing burns and fatalities in early industrial settings.^[31] To mitigate these hazards, comprehensive safety measures are implemented, focusing on engineering controls, personal protective equipment (PPE), and ongoing monitoring. Effective ventilation systems, including enclosed hoods and gas capture mechanisms, can achieve over 90% efficiency in containing emissions during coke pushing and charging, significantly reducing airborne exposure.^[63] Workers are required to use PPE such as respirators with organic vapor cartridges for gas protection and fire-resistant suits to guard against thermal and explosion risks.^[64] Air quality monitoring ensures compliance with permissible exposure limits (PELs), such as OSHA's 50 ppm 8-hour time-weighted average for CO, with real-time sensors alerting to exceedances.^[65] Training programs for kiln and oven operators emphasize hazard recognition, emergency response procedures, and proper handling of equipment to prevent accidents.^[66] Industrial standards further guide occupational safety in carbonization facilities. In the United States, OSHA's standard for coke oven emissions limits exposure to 150 micrograms per cubic meter as an 8-hour average in regulated areas, mandating medical surveillance for workers.^[63] In the European Union, the Industrial Emissions Directive (2010/75/EU) sets emission limit values for coke oven operations, indirectly supporting worker protection by requiring best available techniques to minimize releases, while national occupational exposure limits align with EU Framework Directive 89/391/EEC on workplace safety.^[67] Modern enclosed retort systems significantly reduce worker exposure to emissions compared to traditional open-pit or methods, through better containment and automation.^[68] Mitigation through automation, such as mechanical ash handling and remote kiln monitoring, has proven effective in reducing direct contact and respiratory risks in contemporary facilities.^[69]

Environmental Impacts and Sustainability

Carbonization processes, including dry pyrolysis and hydrothermal carbonization (HTC), present a dual profile of environmental impacts, offering opportunities for carbon sequestration and waste valorization while posing risks from emissions and resource use. In dry pyrolysis, the thermal decomposition of biomass under oxygen-limited conditions at 100–1000°C preserves approximately 50% of the original carbon in a stable biochar form, enabling long-term soil carbon sequestration with a global potential of 0.7–1.8 Gt CO₂-C equivalent per year.^[70] This process can achieve a negative global warming potential (GWP) of -1323 to -1355 kg CO₂-eq per ton of biomass, classifying it as carbon-negative when integrated into life cycle assessments.^[70] However, pyrolysis emits CO₂, CO, volatile organic compounds (VOCs), methane, particulate matter (PM), and NO₂, with PM levels potentially 40 times higher than European Union limits for municipal waste incineration, necessitating advanced emission controls.^[71] Energy demands for drying wet feedstocks can contribute 25–83% of supply chain greenhouse gas emissions if fossil fuels are employed, though syngas and bio-oil co-products can offset this through energy recovery.^[71] HTC, operating at 180–250°C under pressure with wet feedstocks, mitigates some drying-related energy burdens and recovers higher energy yields from waste biomass, producing hydrochar with 15–30 MJ/kg energy content and yielding up to 61% solids on a dry basis.^[7] This method reduces overall environmental impacts compared to landfilling or incineration by emitting fewer pollutants and odors, while enabling nutrient recovery (e.g., phosphorus and nitrogen) for soil amendment and CO₂ adsorption for sequestration.^[7] Process water from HTC, comprising 65% of outputs, can be recycled or repurposed for irrigation, minimizing freshwater use, though its emissions and hydrochar combustion remain significant contributors to system-wide impacts like eutrophication and acidification in life cycle analyses.^[72] Despite these benefits, both processes can introduce contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), and dioxins into soils and water if feedstocks are impure, potentially enhancing pollutant migration, phytotoxicity, and aquatic organism inhibition.^[73] Biochar application may also increase soil CO₂ emissions by 18–73% at high rates (15.75–47.25 tons/ha) due to boosted microbial activity, underscoring the need for optimized dosing.^[70] Sustainability in carbonization hinges on circular economy principles, transforming biomass wastes into value-added products like biochar for soil enhancement, which boosts crop yields by up to 20% at 10 tons/ha and reduces nutrient runoff and erosion.^[70] By diverting organic wastes from landfills, these processes lower methane emissions and support goals like SDG 13 (climate action) through durable carbon storage lasting centuries.^[70] Life cycle assessments indicate GHG reductions of 62–66% for biochar from yard waste or corn stover, promoting economic viability with a projected global market of US$368.85 million by 2028.^[70] To enhance sustainability, strategies include feedstock selection to minimize contaminants, process integration for energy efficiency (e.g., TRL 6–9 for pyrolysis), and regulatory frameworks for emission monitoring, ensuring net positive environmental outcomes over traditional waste management.^[71]

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1. Biomass moves from drying to pyrolysis, which is a thermal decomposition process in the absence of oxygen that separates com- ponents of ...
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Effects of temperature and heating rate on the characteristics of ...
At low temperature (400 °C), the char yield rate was positively correlated to the heating rate. But at higher temperatures (500 to 700 °C), the char yield rates ...
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[PDF] Charcoal - its Manufacture and Use - Forest Products Laboratory
All plants have in common, however, two main operating steps in which (a) the wood is predried and carbonized and (b ) the crude liquid products obtained are ...Missing: stages | Show results with:stages
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[PDF] Charcoal Production, Marketing, and Use
In the kiln, heat converts wood to charcoal in two stages--the drying and the coaling stage. The heat needed for drying and to initiate coaling conditions is ...
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[PDF] Iron and charcoal: the industrial fuelwood crisis in Minas Gerais
The traditional kiln has an energy efficiency of 49% (ratio of energy content of charcoal output to energy content of wood input) and accounts for about 80% of ...Missing: earth | Show results with:earth<|separator|>
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[PDF] Review of Technologies for the Production and Use of Charcoal
Mar 1, 2005 · We compare the efficiencies of over thirty kilns with dry weight yield efficiencies ranging from 12 to over 40% along with production volumes ...
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[PDF] Energy Efficiency Improvement and Cost Saving Opportunities for ...
In a coke oven, coal is heated to. 1830-2010°F (1000-1100°C) for 14-24 hours in the absence of air (to prevent combustion) to remove the volatile matter. The ...
[45]
[PDF] 12.2 Coke Production Final May 2008
Foundry coke production uses a different blend of coking coals, longer coking times, and lower coking temperatures relative to those used for metallurgical coke ...Missing: caking | Show results with:caking
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Hydrothermal carbonization process - ScienceDirect.com
Hydrothermal carbonization is a thermochemical process converting biomass into solid biofuel, liquid, and gas. It is effective for sewage sludge disinfection ...<|separator|>
[47]
Process Waters from Hydrothermal Carbonization of Waste ... - MDPI
Friedrich Bergius first presented the process in 1913 as an imitation of the natural generation of hard coal in controlled process conditions [12]. The process ...
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HTCycle EU Project
We aim to demonstrate and commercialize the proprietary technology for hydrothermal carbonization (HTC) using sewage sludge as raw and main material, showing ...Missing: 2020s | Show results with:2020s
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Fuel properties and combustion performance of hydrochars ...
Oct 7, 2022 · RF-derived hydrochars exhibited better fuel properties due to the increased carbon content, HHV, combustion adequacy, and low ash content. Thus, ...
[50]
Techno-Economic Assessment of Co-Hydrothermal Carbonization of ...
Feb 15, 2019 · In this study, technoeconomic analysis of Co-HTC was performed for a scaled-up Co-HTC plant that produces fuel for 110 MWe coal-fired power plant.
[51]
From Biomass to Fuel Blendstocks via Catalytic Fast Pyrolysis and ...
The CFP pathway with the hydrodeoxygenation catalyst gave the highest overall carbon efficiency from biomass to fuel blendstocks (34%) but, at the same time, ...
[52]
Sewage Sludge Management at District Level: Reduction and ...
Oct 5, 2022 · The objective of the simulation is to investigate the performances of AD + HTC treatment to reduce sludge production and improve nutrient and energy recovery.Missing: food | Show results with:food
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Activated carbon from agricultural residues: a review - ScienceDirect
Activated carbon is a main element for treatment of wastewater, groundwater and water purification. The activating agents greatly affects the porosity and ...
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Chapter 8: Soil Carbon Sequestration and Biochar - Books
Aug 22, 2022 · Biochar's feasible technical potential is 2.6 Gt CO2eq per year. Both SCS and biochar can be implemented on existing land and bring additional ...
[55]
[PDF] Mineral carbonation and industrial uses of carbon dioxide
Olivine: Mg2SiO4 + 2CO2 → 2MgCO3 + SiO2. + 89 kJ mol–1CO2. (2a). Serpentine: Mg3Si2O5(OH)4 + 3 CO2 → 3MgCO3 + 2SiO2 + 2H2O. + 64 kJ mol–1CO2. (2b). Wollastonite ...Missing: 4CO2 | Show results with:4CO2
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Hydrothermal Carbonization of Microalgae Biomass from ... - NIH
Jul 21, 2025 · Hydrothermal carbonization (HTC) of wastewater-grown microalgae biomass is an attractive route for producing hydrochar (a solid fuel).Missing: 2020s | Show results with:2020s
[57]
[PDF] Advancements of Biochar-Based Catalyst for Improved Production of ...
Jan 5, 2023 · Biochar, made from thermochemical processes, can act as a catalyst in biodiesel production via transesterification, which uses oils and animal ...
[58]
[PDF] COKE OVEN GAS - Drummond Co.
Feb 10, 2009 · 800 ppm. 0.10. WATER. N/A. N/A. N/A. 3.20. HYDROGEN SULFIDE. C-20 ppm peak 50 ppm 10 min. Duration. 0.10. Section III - Physical/Chemical ...
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A cross-sectional analysis of respiratory ill-health among charcoal ...
Jan 24, 2019 · Despite the significantly higher prevalence of wheeze, chest tightness and chronic cough among charcoal workers, their hazard control practices were inadequate.
[60]
Coke Oven Gas, its Characteristics and Safety Requirements
Apr 29, 2015 · It is a flammable gas with lower explosive limit of 4 % and upper flammability limit of 75 %. Its vapour density is 0.39 (air=1) and relative ...
[61]
https://pmc.ncbi.nlm.nih.gov/articles/PMC6347919/
[62]
NIOSH Pocket Guide to Chemical Hazards - Coke oven emissions
OSHA PEL ; Symptoms. irritation eyes, respiratory system; cough, dyspnea (breathing difficulty), wheezing; [potential occupational carcinogen] ; Target Organs.
[63]
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1029
[64]
[PDF] OCCUPATIONAL EXPOSURE - Clean Air Council
At those times the carcinogenic hazards of coke oven emissions shall be presented to the worker, and the early symptoms and signs of cancer shall be explained, ...
[65]
[PDF] commission implementing decision - EUR-Lex - European Union
Feb 28, 2012 · BAT is to use desulphurised and dedusted surplus coke oven gas and dedusted blast furnace gas and basic oxygen gas (mixed or separate) in ...
[66]
Comparison of Technical and Operational Conditions of Traditional ...
Nov 24, 2023 · Our study aimed to comprehensively compare five distinct charcoal production systems, including both traditional and modern solutions.
[67]
Potential Health Effects of Crystalline Silica Exposures from Coal Fly ...
The amount of crystalline silica in coal fly ash (CFA) depends on a variety of factors, including the amount of silica in the pre-combustion coal, ...
[68]
(PDF) Comparison of Technical and Operational Conditions of ...
Nov 15, 2023 · Our study aimed to comprehensively compare five distinct charcoal production systems, including both traditional and modern solutions, with a ...
[69]
Use of biomass-derived biochar as a sustainable material for carbon ...
Aug 5, 2025 · The carbon sequestration potential of biochar in soil varies in the range of 0.7–1.8 Gt/Pg CO2-C(eq)/year. In addition to carbon sequestration, ...
[70]
[PDF] Biochar - evidence on potential environmental impacts and social ...
Pyrolysis and gasification offer greater flexibility, compared to Hydrothermal Carbonization ... impacts: the environmental impacts associated with the pyrolysis.
[71]
Assessing the environmental impact of energy production from ...
Results from this analysis indicate that HTC process water emissions and hydrochar combustion most significantly influence system environmental impact, with a ...
[72]
https://research.cec.sc.edu/berge/publications/assessing-environmental-impact-energy-production-hydrochar-generated-hydrothermal