Muthu Kumar K

Area of interest

Combustion and gasification

Faculty Advisors

Guide : Prof. Amit Kumar, AE, IITM

Co-Guide : Dr. Varunkumar S, ME, IITM

Course expertise

Aerospace propulsion
Fundamentals of combustion
Computational heat and fluid flow
Advanced fluid mechanics

Thermodynamics
Heat and mass transfer

Thesis title:

Self-Sustained single step in-situ process for synthesis of charcoal and activated carbon from coconut shells

Problem Description

To develop a self-sustainable single-step process for synthesizing market quality activated carbon and Charcoal (also known as biochar) from coconut shells and other ligno-cellulosic biomass without fossil fuel use.

Research objective

This research is aimed at developing an economical and eco-friendly self-sustainable system that uses novel processes for AC and charcoal synthesis:

AC: A ‘self- Sustained single step activation in-situ’ (s-Susstains) process is developed to produce AC in a single step directly from the raw material, without using any external heat source for activation and steam generation.
Charcoal: A ‘Self-sustained controlled oxidative flash de-volatilization’ process for high yield biochar synthesis from coconut shells ( or any other ligno-cellulosic biomass).

RESEARCH WORK

1. Ultra-rich carbonization through flash devolatilization for synthesis of biochar from biomass (full paper : click here)

Biochar setup

Biochar Technology.mp4

Operation video

Abstract:

This paper presents a scalable ultra-rich carbonization process in counter-current packed bed (CCPB) for synthesizing biochar/charcoal with a yield of more than 33% and fuel consumption rate of more than 200 g/m2s (which is at least 2 times more than the maximum achievable with conventional gasification) from coconut shells (CS). The novelty of the process lies in the use of reactant pre-heating to slightly below the devolatilization temperature of CS as a strategy to achieve steady and controlled conversion of CS to biochar/charcoal. The basis for this idea is that the ignition time (tig) of biomass particles decreases significantly with pre-heating while the time for devolatilization (tv) remains more or less the same. Single particle experiments with CS as fuel and atmospheric air as oxidizer show that tv/tig increases from 1.3 to 7.7 with a corresponding increase in pre-heating temperature Ti from 30 to 170 ∘C. The bed operation, in terms of flame propagation, equivalence ratio, and charcoal yield, with pre-heating to slightly below devolatilization temperature in CCPB systems, shows several interesting behaviors not observed in traditional gasifier systems. Two prominent examples of such behaviors are steady flame propagation under extremely rich conditions (volatile equivalence ratio, ϕv > 10) and reduction in peak bed temperature (Tpb) well below 600 ∘C. The biochar yield of the developed process is at least 25% more than traditional CCPB gasification system. The feedstock flexibility, self-sustainability, and scalability of the developed process are also brought out .

2. Single step in situ activation process for activated carbon synthesis from coconut shells (full paper: click here)

Batch schematic AC.pdf

Schematic

Abstract:

Biomass-based activated carbon is used in filtration and purification due to its high porosity and absorptivity. This paper reports a scalable single-step self-sustained process to synthesize activated carbon from coconut shells. The process uses mixtures of air and steam as the activation agent (referred to as the activator) in a counter-current packed bed system. The ratio of air to steam in the activator and the strain rate of the activator (a parameter derived from the activator flow velocity) are the key controlling parameters of activation. For a fixed ratio of air to steam in the activator, the extent of activation (quantified by the iodine value of the product) is found to initially increase with an increase in strain rate and starts to decrease beyond a certain critical value. For a given air-steam ratio, this critical value called as extinction strain rate is found to be linked to a fundamental characteristic of the gas-phase flame formed around fuel particles due to the release of volatiles. It is observed that activation increases with an increase in strain rate as long as the gas-phase flame engulfs the fuel particle. Beyond the extinction strain rate (found to be around 250 ± 10 s− 1), the engulfing flame is extinguished and activation starts to fall; this is inferred to be due to the surface oxidation of char due to the absence of gas-phase flame, leading to a lack of pore formation and hence a decrease in activation. For activator flow rates within the extinction strain rate, various regimes for AC synthesis are identified based on the degree of activation and yield. Maximum activation of 850 mg/g iodine value at 8% yield is obtained at an air to steam ratio of 2 and an activator strain rate of 244 s− 1 .

3. In-situ gasification-activation system with staged oxidizer supply for generation of activated carbon and intrinsic hydrogen rich by-product gas from coconut shells (Full paper: click here)

3D schematic

continous system paper R1.mp4

Operation video

Abstract:

A bottom lit open top packed bed In-situ Gasification-Activation System with Staged Oxidizer Supply (IGAS-SOS) for co-generation of activated carbon (AC) and intrinsic hydrogen rich producer gas from coconut shells in single step is demonstrated. Primary air is used for gasification. Superheated steam, in conjunction with secondary air, is employed for activation by injecting it directly into the char bed and distributing it evenly. It is identified that volatile equivalence ratio between 2.1 and 2.5, steam temperature Tsteam of ~700 oC, and tact of ~3 h are critical for char-steam reaction to be kinetically controlled. Increase in Tsteam from 250 oC to 700 oC increases both maximum activation and intrinsic H2 yield from 624 m2/g and 16 g/kg of biomass to 965 m2/g and 27 g/kg of biomass, respectively without much compromise in AC yield. Further, preferred configuration of oxidizer supply also ensures tar free exit gas, with higher hydrocarbon levels below 2.5 g/kg of biomass. SABET and yield are enhanced at least twofold compared to earlier works on in-situ physical activation.

Publications

Muthu Kumar, K., and S. Varunkumar. "Ultra-rich carbonization through flash devolatilization for synthesis of biochar from biomass." Biomass Conversion and Biorefinery (2023): 1-12.
Muthu Kumar, K., and S. Varunkumar. "Single step in situ activation process for activated carbon synthesis from coconut shells." Biomass Conversion and Biorefinery (2023): 1-11.
Muthu Kumar, K. "In-situ gasification-activation system with staged oxidizer supply for generation of activated carbon and intrinsic hydrogen rich by-product gas from coconut shells." Biomass Conversion and Biorefinery (2024): 1-13.

Patent

Muthu Kumar K, Varunkumar S, Syed Mughees Ali, "Self-Sustained single step activation in-situ process for activated carbon synthesis from agro residues", Patent No: 389137.
Muthu Kumar K, Varunkumar S, “Self-sustained controlled oxidative flash devolatilization system for biochar synthesis from agro residues”, App no: 202141056397.

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