Vertical Roller Mill Layout for Biomass Torrefaction and Fine Grinding
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Solution Overview
Problem
Existing torrefaction devices are inefficient in terms of both comminution and torrefaction, particularly for fresh biomass and waste materials, leading to issues with particle size and energy consumption.
Innovation Solution
A vertical roller mill with a grinding unit and hot gas supply system is used, where raw material is fed from below the grinding elements, allowing initial torrefaction before comminution, and a vortex zone is created for enhanced heat transfer and particle separation, resulting in a more efficient and complete torrefaction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If raw material is fed from the top into the working chamber above the grinding elements, then the comminution process can proceed, but the torrefaction is incomplete and requires additional downstream processing
Solution Approach 1:
The raw material is fed from the bottom of the working chamber below the grinding elements, allowing it to be torrefied by hot gas before entering the grinding zone. This preliminary torrefaction weakens the cell structures and makes the material more brittle, enabling complete torrefaction and comminution in a single integrated process without requiring additional downstream processing steps
2Manufacturing precision
If conventional top-feeding is used, then the device structure is simple, but the particle fineness is insufficient and energy consumption increases
Solution Approach 1:
By feeding raw material from the bottom below the grinding elements, the material undergoes preliminary torrefiction in the hot gas zone before grinding. This pre-treatment makes the material more brittle and easier to comminute, achieving finer particle size distribution and reducing the energy required for downstream comminution operations
Solution Approach 2:
The invention merges the torrefiction and comminution zones vertically within a single working chamber, with the torrefiction zone positioned below the grinding elements. This integration allows simultaneous heat transfer and mechanical breakdown, improving particle fineness while reducing overall energy consumption compared to separate processing stages
3Speed
If hot gas is supplied above the grinding unit, then the torrefiction process can occur, but the heat transfer efficiency is reduced and processing time increases
Solution Approach 1:
Instead of supplying hot gas from above the grinding unit as in conventional designs, the invention inverts the arrangement by supplying hot gas from the bottom of the working chamber below the grinding elements. This inversion creates an upward hot gas flow that efficiently heats the raw material from below, improving heat transfer efficiency and reducing processing time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves faster and more complete torrefaction with improved particle fineness, reducing the need for downstream comminution and minimizing energy losses, while producing a homogeneous product suitable for gasification.
Implementation Method 1
Torrefiction is a mild thermal treatment of solid fuels without exposure to air (oxygen content preferably below 4 wt%), resulting in pyrolytic decomposition and drying. It typically takes place at temperatures of 200 to 320 °C.
Implementation Method 2
a vortex zone is created for enhanced heat transfer and particle separation
Implementation Method 3
the torrefied particles fall from the upper region into the lower region of the working chamber
Data Source
Figure 1~3
Figure 4~9C
AI summary
Torrefaction device for producing a fine-grained fuel from energy raw materials, in particular comprising biomass and/or alternative fuels from waste, with a reactor (2) for comminution and torrefaction of the raw material. A hot gas supply device (4) and a separation device (6) are provided below a grinding mill (35) in a working chamber (22). The grinding mill is a vertical roller mill (3), with the raw material supply device (4) being located in the lower part of the reactor (2) such that it opens into the lower part of the working chamber (22). Since the hot gas is also supplied there, torrefaction begins even before the raw material reaches the grinding media, utilizing the high temperature of the hot gas at the inlet. Thus, pre-embrittlement of the raw material is achieved on the short path from the feed point to the initial contact with the grinding media. It is therefore comminuted more effectively by the grinding media.Initially, improved comminution and torrefaction are achieved. This combination increases efficiency.