Lead Author: V.K.Bindlish, Unit Head JSL
Co- Author: Ashok Sharma Head ESG Cell JSL
Co- Author: Manoj Gupta – GM SMS JSL
Co- Author: Sandeep Agarwal – GM ESG Cell JSL
Co- Author: Arvind Sharma – Sr. Manager ESG Cell JSL
(Jindal Stainless Limited Hisar, Haryana, India)
Abstract
This research explores the strategic adoption of bio-coal, derived from coconut shells, as a substitute for traditional coke in the Steel manufacturing process. Focused on the reduction of carbon emissions and overall environmental impact, the study evaluates the viability of bio-coal through comprehensive trials and analyses. The bio-coal blends demonstrated comparable metallurgical properties, with promising carbon recovery rates and favourable heat characteristics. Stack emission reports indicate a no negative environmental performance during the trials.
The business benefits of integrating bio-coal are manifold. Environmental advantages include a lower carbon footprint and improved sustainability alignment. Operationally, the higher energy content and potential cost savings contribute to increased competitiveness. Diversifying energy sources enhances long-term resilience. Bio-coal adoption fosters a positive corporate image, appealing to stakeholders valuing sustainability, and positively positions the company in the market. Proactive compliance with evolving environmental regulations ensures minimal operational disruptions, highlighting a strategic approach to risk mitigation.
A series of trials were conducted across multiple grades, varying the ratio of coke to bio-coal to assess its impact on carbon recovery and heat characteristics. Results from ten trials revealed an average carbon recovery rate of 76% for average different stainless-steel grades and in grades like 201 & JSLUDD, more than 85% carbon recovery, indicating the potency of bio-coal blends as a reducing agent in the steelmaking process.
The outcomes of the trials not only demonstrated the compatibility of bio-coal with metallurgical requirements but also showcased its ability to contribute to sustainable steel production.
Problem Definition
Stainless steel is manufactured through melting of scrap and ferro alloys, coke serving as a primary reducing agent. The reduction of reactive metal oxides by coke at elevated temperatures produces carbon monoxide (CO) and releases the metal, effectively removing oxygen from the oxide But carbon emission of coke is very high with the emission of 3.33 kg of CO2 for every 1 kg of coke used, according to the Intergovernmental Panel on Climate Change (IPCC).
Heat carbon% and carbon recoveries are key factors of considerations. Now is a need to find an alternate of coke which has same characteristics in which process chemistry must not impact and has less emissions. Coke can be major challenge to achieve Net zero path.
This research paper aims to contribute valuable insights into the quest for a sustainable future in stainless steel production. By addressing the challenges associated with coke usage and exploring alternatives that align with the Net Zero carbon emissions path, the metallurgical industry can embark on a transformative journey towards environmental responsibility and resource efficiency.
Properties of Bio-Coal for Metallurgical Processes:
The properties of bio-coal play a significant role in determining its viability as a substitute for metallurgical coke in industrial processes. This section dig into key characteristics, including calorific value, ash content, volatile matter, fixed carbon, moisture, sulfur, and their collective impact on metallurgical product quality. Through comprehensive analysis and comparison with traditional coke, this exploration aims to provide a subtle difference understanding of bio-coal’s potential in optimizing energy efficiency and product outcomes in metallurgical applications.
Characteristics Comparison Between Bio-Coal and Coke in Steel Industry
The following table shows how Bio-Coal simply outperforms coke from coal.
| Chemistry Compare | |||
| Characteristics | UOM | Bio Coal | Coke |
| Moisture | % | 5.5 | 15 |
| VM | % | 15.16 | 2.3 |
| Ash | % | 2.33 | 16 |
| Fixed Carbon | % | 82.51 | 81.3 |
| GCV | Kcal/Kg | 7000 | 6800 |
| Sulphur Content | % | 0.1 | 0.66-0.81 |
*Bio-Coal has higher calorific value comparing to regular coke from coal. Calorific value is the most important characteristics of a good fuel.
Examining the data, bio-coal demonstrates a lower moisture content (5.5% vs. 15%) and significantly higher volatile matter (15.16% vs. 2.3%) compared to coke. Moreover, bio-coal exhibits lower ash content (2.33% vs. 16%) and a slightly higher fixed carbon composition (82.51% vs. 81.3%). Notably, the calorific value (GCV) of bio-coal surpasses that of coke (7000 Kcal/Kg vs. 6800 Kcal/Kg), suggesting enhanced energy potential. Furthermore, the negligible sulphur content in bio-coal (0.1%) aligns with environmental considerations.
Calorific Value
Bio-coal presents a promising alternative to traditional metallurgical coke due to its competitive calorific value. The calorific value of bio-coal, expressed in kilocalories per kilogram (KCal/kg), is a crucial parameter influencing the energy efficiency of metallurgical processes. In comparison to metallurgical coke, bio-coal exhibits 7000 Kcal/kg, indicating its potential as an energy-rich substitute which is comparable to Metallurgical Coke being used in the process with energy value of 6800 Kcal/kg.
Reactivity and Combustion Characteristics
The reactivity of bio-coal during combustion significantly impacts temperature profiles and overall combustion efficiency in metallurgical processes. The average tapping temperature during the trail was remained at around 1560 degree Celsius using bio-coal which was in accordance with the desired outcome.
High Fixed Carbon Content
The fixed carbon content in bio-coal contributes significantly to its energy content. Comparative analysis with metallurgical coke fixed carbon composition (81.3%) & Bio-Coal fixed carbon composition (82.51%) provides insights into the potential of bio-coal as an energy source in metallurgical applications. The fixed carbon content is integral to understanding the combustion efficiency and energy release during the process, carburizing effect, better Slag Foaming: protect Lining & better Reducing property.
Low Sulfur Content
Lower sulfur content translates to reduced sulfur dioxide (SO2) emissions during combustion, lower sulfur content supports improved air quality and human health. Sulfur content in bio-coal is a critical parameter with environmental implications. Comparative studies indicate Bio-Coal with sulfur content less than 0.12% of bio-coal and its potential impact on emissions. Low sulfur content aligns with sustainable and green initiatives, making bio-coal an attractive option for industries aiming to reduce their environmental impact and promote corporate social responsibility.
Low Carbon Footprint:
Bio-coal is derived from biomass sources, which absorb carbon dioxide (CO2) during their growth. As a result, the combustion of bio-coal releases CO2 that was recently captured, making it a carbon-neutral or even a carbon-negative fuel source. The substitution of bio-coal for coke in metallurgical processes can directly contribute to reducing the greenhouse gas intensity of these operations.
High Level Solution
In order to replace the coke and to maintain the liquid metal chemistry, Coconut shell charcoal natural lumps identified as a replacement of coke having following characteristics.
| Description | UOM | Coconut Shell |
| Moisture | % | 5.5 |
| VM | % | 15.16 |
| Ash | % | 2.33 |
| Fixed Carbon | % | 82.51 |
| GCV | Kcal/Kg | 7000 |
| Sulphur Content | % | 0.1 |
Trial plan was made and implemented to replace the coke as reducing agent. 5 grade were identified and trial done with Mixing of Coke and Bio coal (Coconut Shells).
Comparative analysis of the trial for different grade manufacturing (Graphs / infographics) and different combination of coke: biochar ratio
| Heat Description | Grade | Coke Used-Kg | Bio Coal used-Kg | Heat Carbon% | Carbon Recovery |
| 2308J0282 | JSLUDD | 122 | 180 | 2.25 | 97% |
| 2308J0283 | JSLUDD | 227 | 180 | 1.97 | 87% |
| 2308J0294 | 409L | 759 | 360 | 1.81 | 68% |
| 2308J0296 | 409L | 680 | 390 | 1.78 | 57% |
| 2308J0331 | J-201 | 70 | 400 | 1.8 | 87% |
| 2308J0332 | J-201 | 103 | 400 | 2.0 | 85% |
| 2308J0340 | SUH409L | 0 | 680 | 1.9 | 77% |
| 2308J0341 | SUH409L | 120 | 690 | 1.75 | 76% |
| 2308J0361 | IRSM | 0 | 640 | 1.82 | 71% |
| 2308J0362 | IRSM | 50 | 700 | 1.70 | 55% |
| Average recovery | 76% | ||||
Stack Emission Report
| S. No. | Particulars | Unit | Data Observed |
| 1. | Ambient Temp. | oC | 38 |
| 2. | Stack Temp. (Avg.) | oC | 97 |
| 3. | Velocity of Flue Gas | m/sec | 10.90 |
| 4. | Sampling Duration | Minutes | 50 |
| S. No. | Parameters | Unit | Results | Standard Limits | Protocol Used | OK / Not OK |
| 1. | Particulate Matter | mg/ NM3 | 19.37 | 150 | IS 11255 (P-1) :1985 | OK |
Business Benefits
Bio-coal emerges as a standout alternative to traditional biomass fuels, bringing with its higher energy content, lower moisture, and improved handling and storage features. In a departure from fossil coal, bio-coal is free from sulfur, nitrogen oxides, and mercury. Plus, its remarkably lower ash content makes for a cleaner burn, effectively reducing greenhouse gas emissions.
These advancements in fuel technology not only boost efficiency but also align with sustainability goals. The absence of harmful pollutants commonly found in coal positions bio-coal as a promising choice for a cleaner and more environmentally conscious energy future.
Some of the key benefits are mentioned for a panorama understanding of importance of shifting to such energy alternative which are highley efficient together with low carbon emission properties.
Environmental Advantages:
- Lower carbon footprint through reduced greenhouse gas emissions.
- Improved environmental performance aligns with sustainability goals.
Diversification of Energy Sources:
- Reduces dependency on conventional fossil fuels, enhancing long-term resilience.
Positive Corporate Image:
- Appeals to consumers, investors, and stakeholders valuing sustainability.
Market Positioning:
- Positions the company as a responsible industry leader.
- Attracts environmentally conscious customers and investors, enhancing brand loyalty.
Regulatory Compliance and Risk Mitigation:
- Proactive adoption of sustainable practices mitigates regulatory compliance risks.
- Ensures alignment with evolving environmental regulations, minimizing operational disruptions.
Benefits achieved from the trial
The potential benefits of using Bio-coal as an enabler in respect of carbon abatement is highly scalable in a NetZero business scenario. Yearly consumption at the trail plant location is around 4000MT of Coke which can impact significant in CO2 reduction of more than 13000MT.
Operational / handling challenges
There were no major handling challenges were overserved during or after the trial. Satisfactory for use as a replacement of conventional coke.
Summary
The research explores the feasibility of replacing coke with bio-coal in stainless steel manufacturing processes. Trials and analyses demonstrate that bio-coal, specifically from coconut shells, can serve as an effective reducing agent with comparable metallurgical properties. The business benefits encompass improved environmental performance, reduced carbon emissions, and a more sustainable approach to steel production. This study provides valuable insights into transitioning towards a cleaner and more sustainable practice for the steel industry. This could also be a key enabler in transitioning from high to low carbon economy and a successful driver to achieve NetZero ambitious path for any Industry as well as the Nation.