Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
Biomass Torrefaction System for Enhanced Energy Density and Product Uniformity Using Dual-Loop Indirect Heating
2. APPLICANT(S)
Name Nationality Address

Steamax Envirocare Private Limited
Indian B-54, Upper Ground, New Krishna Park, Vikaspuri, New Delhi, 110018

PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specification describes the invention.
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.
4. DESCRIPTION (Description shall start from next page.)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble— “I/ We claim” on separate page)
6. DATE AND SIGNATURE (to be given at the end of last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on separate page)

 
FIELD OF THE INVENTION
The present invention relates to biomass processing technologies, specifically to systems and methods for torrefaction of biomass using heating methods and optimization of energy efficiency.

BACKGROUND OF THE INVENTION
Biomass torrefaction is a critical process in biomass energy production, involving the thermal treatment of biomass in the 200–300 °C range under low-oxygen conditions. Existing systems either rely on direct heating, leading to uncontrolled combustion, or use single-loop heating systems that fail to offer adaptive control over drying and torrefaction phases.
Traditional torrefaction systems often suffer from inefficiencies in thermal delivery, inconsistent heat exposure, and high energy consumption due to reliance on direct combustion or single-loop heating systems. Furthermore, non-uniform drying or overheating of biomass can degrade feedstock quality and limit operational flexibility.
In certain embodiments, the system is configured to allow recycling of all or a portion of the torrefier off-gas, wherein the non-condensable gases (NCGs) generated during torrefaction are recirculated and optionally utilized as a supplemental fuel within the thermal system. This configuration enhances energy efficiency by reducing external fuel requirements and facilitating partial energy self-sufficiency of the process.
The torrefaction reactor may be further designed to support both counter-flow and co-flow configurations between the process gas and the biomass feed. The counter-flow arrangement enables improved heat exchange efficiency, while the co-flow configuration may offer operational simplicity and uniform material conveyance.
The system may also incorporate automated control mechanisms for regulating critical process parameters including, but not limited to, temperature, pressure, flow rates, and gas composition. These controls ensure stable operation, precise thermal management, and consistent product quality across varying biomass feedstocks.
Additionally, the system is equipped with means for sampling the biomass feed, torrefied product, and off-gas streams, thereby enabling real-time or periodic analysis of thermal decomposition behavior, physicochemical changes, and overall system performance. This feature supports process optimization, quality assurance, and diagnostic evaluation during development, scale-up, or industrial operation
There is a pressing need for a system that not only ensures uniform heating but also allows independent control of drying and torrefaction stages, minimizes energy consumption by recovering torrefaction gases, and improves the quality and consistency of the torrefied biomass product.
There exists a need for a more efficient, scalable, and controllable torrefaction system that can adapt to various biomass types and deliver uniform thermal treatment throughout the drying and torrefaction stages.
The present invention addresses these limitations by introducing a dual-stage system for biomass drying and torrefaction, designed to operate with indirect heating via a closed-loop thermic fluid system. By employing independent thermal loops, the system enables precise and customizable heat delivery to both the drying and torrefaction units, ensuring greater control over process parameters such as temperature and residence time. This approach not only reduces reliance on external fuels but also optimizes thermal recovery within the process.
The invention ultimately aims to deliver uniform, high-quality torrefied biomass through scalable and adaptable equipment suitable for industrial deployment, particularly in contexts where feedstock variability and fuel efficiency are critical factors.
SUMMARY OF THE INVENTION
The invention relates to an advanced biomass torrefaction system comprising a four-stage indirect belt dryer and an auger-screw reactor, both thermally powered by a dual-loop thermic fluid heating circuit. This configuration enables precise and independent thermal control over the drying and torrefaction processes, significantly improving energy efficiency by utilizing both biomass and torrefaction gases as fuel. The system ensures consistent heat delivery, accommodating a wide range of feedstocks while enhancing process stability and fuel utilization. By applying controlled, indirect heat, the system promotes improved hydrophobicity, friability, and bulk energy density in the torrefied biomass, achieving energy values up to 23-27 MJ/kg. The resulting output exhibits reduced fines and minimal binder requirements, making it ideal for pelletization or briquetting. Overall, the invention ensures production of market-grade torrefied biomass with uniform fuel quality and high performance.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Schematic diagram of the dual loop heating zone of dryer and reactor
Figure 2: Cross-sectional view of the four-stage belt dryer and auger-screw reactor

DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a indirect biomass torrefaction system, specifically designed to improve the thermal efficiency, adaptability, and consistency of biomass pre-treatment for use as a solid biofuel. The system integrates a multi-zone indirect drying mechanism with a controlled torrefaction reactor, all operating under a closed-loop, thermic fluid-based heating circuit powered by firing of biomass. This configuration offers precise thermal management, modular operation, and energy optimization.
The system comprises the following primary components:
Fuel Conveyance System: Raw biomass is lifted from a ground-level hopper to the dryer inlet using a bucket elevator enclosed in a mild steel casing to minimize air intrusion. It includes inspection doors and maintenance access points for operational reliability.
Biomass Belt Dryer (Indirect Type): A four-stage indirect belt dryer utilizes thermic fluid radiators located beneath the belt to remove moisture from biomass efficiently. Conveyor speed and residence time are optimized based on feed moisture content and biomass type to ensure uniform drying without combustion risk.
Torrefaction Reactor: The dried biomass is fed into an auger-screw type torrefaction reactor enclosed in thermic fluid jacketing. Operating at 270–280 °C under oxygen-limited conditions, the reactor thermochemically upgrades the biomass during auger transport, enhancing its energy density, hydrophobicity, and storability.
Thermic Fluid Heating Unit: The heating system consists of a closed-loop thermic fluid heater fired by both biomass and torrefaction gases. A spiral coil above the combustion chamber heats the fluid to 300–330 °C. The heated fluid is circulated via two independent loops: one to the belt dryer and the other to the torrefaction reactor. Each loop features separate flow, temperature, and pressure control systems for precise thermal management
The invention encompasses a four-stage, thermally-integrated biomass torrefaction system designed for the efficient thermal upgrading of lignocellulosic feedstock. The system operates through sequential stages, combining indirect heat transfer with oxygen-restricted processing to produce torrefied biomass with enhanced fuel properties. The integrated stages and their operation are described below:
In the initial stage, raw biomass is introduced into a boot hopper, from where it is conveyed vertically by a bucket elevator to the inlet of the four-stage belt-type indirect biomass dryer. The belt dryer comprises a continuous conveyor system segmented into multiple thermal zones. Each stage of the belt dryer is heated indirectly using a thermic fluid radiator installed beneath the belt surface. The radiator transfers heat to the conveyor through conduction and convection without direct contact with the biomass, thereby avoiding combustion risks.
Biomass advances along the belt at a controlled and adjustable speed (2-3 rpm), and the residence time of 30 mins within each zone is optimized based on the moisture content and feedstock. The raw biomass contains oxygen and carbon ratio of 0.4-0.8 and Hydrogen to carbon ratio is 1.2-2. The moisture level of raw biomass is 10-30%. The drying process elevates the biomass temperature to a maximum of approximately 110 °C, effectively reducing moisture content to desired levels. The chamber includes a strategically placed exhaust and venting system to remove moisture-laden air while minimizing heat loss and maintaining a low-oxygen environment.
Dried biomass is discharged from the terminal outlet of the belt dryer into a sealed inlet hopper of the torrefaction reactor. The transition from dryer to reactor is facilitated through an enclosed duct designed to prevent atmospheric air from entering the process stream, maintaining the system’s anaerobic or low-oxygen conditions. This configuration ensures continuous and uninterrupted feeding of pre-dried biomass into the reactor, reducing thermal shocks and preserving the controlled atmosphere necessary for uniform torrefaction.
The torrefaction process occurs inside a horizontal auger-screw reactor, which is entirely enclosed in a thermic oil jacketing system. The reactor is maintained at temperatures ranging from 270 °C to 280 °C. Reactor capacity is of 2500 Kg/hr and residence time of 30 mins for the moisture level of the biomass content around 4-6%.
Heat is transferred indirectly through conduction and convection, ensuring uniform torrefaction. Gases (torr gases) released during the process are extracted and redirected for combustion in the thermic fluid heating unit.
The heating unit is a thermic fluid heater fuelled by biomass and torr gas. A multi-pass spiral coil mounted above the combustion chamber heats the fluid to ~300–330 °C. The hot fluid is circulated through:
Thermic fluid radiator loop and Thermic oil jacketing loop.
Once heated, the thermic fluid is circulated into two independent loops, each dedicated to a
specific process unit:
• Thermic Fluid Radiator Loop (Dryer Loop): Delivers heat to the belt dryer’s radiator assembly, primarily for moisture removal. Typically receives 40–60% of the total thermic fluid flow depending on biomass moisture content.
• Thermic Oil Jacketing Loop (Reactor Loop): Supplies heat to the torrefaction reactor’s jacket to maintain optimal reaction temperatures. Usually receives 60–40% of the total flow depending on drying load.
Each loop is equipped with independent circulation pumps, pressure control valves, and temperature regulation systems, enabling precise control over process parameters for each functional stage.
After heat transfer, the now-cooled thermic fluid returns to the spiral coil in the heating unit for reheating, thereby completing a closed thermodynamic cycle.
The independent thermal zoning and controllable residence time make the dryer highly adaptable to various biomass types with differing moisture profiles, ensuring uniform pre-drying conditions.
Dried biomass exiting the belt dryer is introduced into a horizontal auger-screw reactor, where it is subjected to torrefaction under low-oxygen conditions. The reactor comprises a screw conveyor (auger) enclosed in a thermic oil-jacketed vessel, which enables indirect heating to operating temperatures in the range of 270–280°C.
The auger mechanism ensures that the biomass is conveyed uniformly through the heated chamber, providing consistent residence time and heat exposure. The reactor is sealed or purged with inert gases (e.g., nitrogen) to maintain a low-oxygen environment and prevent combustion.
The integration of mechanical conveyance within the reactor, combined with uniform thermal jacketing, ensures consistent, safe, and efficient torrefaction without direct flame contact or oxidation.
A thermic fluid heating unit supplies heat to both the dryer and the torrefaction reactor. It comprises a multi-pass spiral coil heat exchanger positioned above a combustion chamber. The unit is capable of firing internally recovered torrefaction gases (torr gas) and biomass. This fuel approach not only enhances the energy efficiency of the system but also enables partial energy self-sufficiency by recovering and utilizing process-generated gases.
The dual independent loops allow tailored heat delivery based on the specific thermal requirements of the drying and torrefaction processes, accommodating feedstock variability and increasing operational flexibility.
The closed-loop thermic fluid heating system provides stable and fine-tuned temperature regulation across both the drying and torrefaction units. This allows the process to operate within a narrow and optimized torrefaction temperature window (typically 270–280 °C), preventing accidental pyrolysis or combustion. By maintaining the thermal environment below the ignition threshold yet above the devolatilization range of hemicellulose, the system ensures controlled thermal decomposition with minimal degradation of cellulose and lignin, leading to the production of uniform, high-quality torrefied biomass.
The torrefaction reactor employs an auger-screw enclosed within a 360° thermic oil-jacketed casing, enabling all-directional and indirect heat transfer to the biomass as it moves through the reactor. This uniform heating configuration eliminates thermal gradients, prevents the formation of cold spots or localized overheating, and ensures even moisture removal and torrefaction. The result is biomass with consistent friability, hydrophobicity, and elevated fixed carbon content, crucial for densification processes such as pelletization.
By utilizing a completely indirect heating strategy, the invention ensures that biomass never comes into contact with combustion gases or ambient air. This design maintains an oxygen-starved environment, essential for safe and effective torrefaction. The elimination of direct flame or air exposure prevents the risk of ignition, uncontrolled combustion, and oxidative degradation, enhancing both process safety and torrefaction efficiency.
The staged drying system allows progressive and uniform moisture evaporation from the biomass prior to thermal decomposition. As the biomass enters the torrefaction zone, volatile organic compounds are released gradually due to controlled indirect heating, minimizing the risk of steam blockage, non-uniform heating, or biomass agglomeration—issues commonly encountered in direct-fired reactors. The smooth torrefaction curve supports optimal devolatilization without damaging structural integrity.
The indirect system ensures that no flue gas, tar, or particulate matter comes into contact with the biomass, resulting in cleaner end products free from fouling or contamination. This configuration reduces the burden on downstream emission control systems, treatment, and minimizes corrosion and fouling, thereby simplifies gas extending equipment lifespan and ensuring lower maintenance requirements.
Controlled heating conditions foster the development of uniform hydrophobicity, higher energy density, and mechanical stability in the torrefied biomass. The resulting product exhibits reduced fines, better flowability, and enhanced compatibility for pelletization or briquetting, often with minimal or no binder. These properties enable the system to produce market-ready solid fuels with predictable combustion behavior and high commercial value.
The indirect heating approach is particularly advantageous for alkali-rich feedstocks (e.g., rice husk, coconut shell), which are prone to slagging, ash fusion, or clinker formation in direct-fired environments. By preventing exposure to direct combustion, the system significantly reduces reactor fouling, slag deposition, and downtime, leading to improved process uptime and maintenance efficiency.
Dual-Zone Thermic Fluid Heating System: A shared thermal loop delivering precise and independent heat control to both drying and torrefaction stages.
Closed-Loop, Low-Pressure Thermal Circuit: Enhances system safety by eliminating auto-ignition risks and maintaining consistent heating without high-pressure hazards.
Torr-Gas Recovery and Reuse: Volatile gases released during torrefaction are redirected and utilized as a fuel supplement for the thermic fluid heater, reducing dependency on fossil fuels.
All-Directional Jacketed Auger Heating: Enables uniform heat application from all sides, ensuring consistent biomass conversion without hot or cold zones.
This combination of design innovations and process controls enables a safe, scalable, and efficient solution for producing high-quality torrefied biomass fuel of 23-27 MJ/kg energy density and suitable for thermal energy applications, co-firing, or densified solid biofuel markets.
, Claims:We claim:
1. A dual-loop indirect heating biomass torrefaction system comprising:
(a) a four-stage indirect belt dryer configured to operate at a conveyor speed of 2–3 RPM, providing a residence time of approximately 30 minutes for efficient moisture removal from biomass
(b) an auger-screw torrefaction reactor having a processing capacity of up to 2500 kg/hr, designed to operate at a temperature range of 270–280 °C under low-oxygen conditions, the reactor being enclosed within a thermic fluid-heated jacket to ensure uniform thermal treatment
(c) a closed-loop thermic fluid circulation system thermally coupled to both the belt dryer and the torrefaction reactor, said circulation system comprising:
a thermic fluid radiator loop configured to deliver indirect heat to the belt dryer’s radiator assembly for drying, receiving approximately 40–60% of the total thermic fluid flow depending on the initial moisture content of the biomass; and
a thermic oil jacketing loop configured to supply thermal energy to the jacketed torrefaction reactor for maintaining optimal torrefaction conditions, receiving approximately 60–40% of the total thermic fluid flow depending on the drying load;
wherein both thermal loops include independent flow, temperature, and pressure control mechanisms for precise and stable heat delivery.
2. The system of claim 1, wherein the belt dryer comprises four independent heating zones, each receiving thermic fluid through separate radiator circuits to enable adjustable thermal zoning.
3. The system of claim 1, wherein the residence time of biomass in the belt dryer is approximately 30 minutes and the belt operates at a speed of 2–3 RPM, facilitating moisture removal without thermal degradation.
4. The system of claim 1, wherein the torrefaction reactor has a biomass processing capacity of up to 2500 kg/hr and provides a residence time of approximately 30 minutes under low-oxygen conditions.
5. The system of claim 1, wherein the auger-screw mechanism within the torrefaction reactor simultaneously conveys and agitates the biomass to ensure uniform heat distribution during torrefaction.
7. The system of claim 1, wherein the dual-loop circulation system distributes thermic fluid such that 40–60% of the total fluid flow is directed to the belt dryer loop and 60–40% to the reactor loop, based on drying load and moisture conditions.
8. The system of claim 1, wherein the independent control of temperature, pressure, and flow rate in each loop allows dynamic thermal adjustment to accommodate varying feedstock types and moisture levels.
9. A method for thermally upgrading biomass using a dual-loop indirect heating system, the method comprising the steps of:
(a) conveying raw biomass into a four-stage indirect belt dryer and drying the biomass at a controlled conveyor speed of 2–3 RPM for a residence time of approximately 30 minutes using a first thermic fluid loop (radiator loop) to supply indirect heat for moisture removal;
(b) feeding the dried biomass into an auger-screw torrefaction reactor configured to operate at 270–280 °C under low-oxygen conditions for approximately 30 minutes, wherein the reactor is indirectly heated via a second thermic fluid loop (jacketing loop);
(c) circulating thermic fluid in a closed-loop heating system that independently distributes thermal energy to both the belt dryer and the torrefaction reactor, wherein:
o the radiator loop delivers approximately 40–60% of the total thermic fluid flow to the dryer based on biomass moisture levels; and
o the jacketing loop delivers approximately 60–40% of the total thermic fluid flow to the reactor based on the drying load;
(d) regulating flow, temperature, and pressure within each loop independently to maintain optimal and consistent drying and torrefaction conditions.

Dated this 27th July ‘2025