# The specifications for the sustainable-design of thermo-hydro-mechanical paths for the elaboration processes of agglomerated products

Bettina Bellocq, Bernard Cuq, Thierry Ruiz, Agnès Duri-Bechemilh,
Guillaume Delaplace, Fabrice Ducept

► To cite this version:

Bettina Bellocq, Bernard Cuq, Thierry Ruiz, Agnès Duri-Bechemilh, Guillaume Delaplace, et al. The specifications for the sustainable-design of thermo-hydro-mechanical paths for the elaboration processes of agglomerated products. 7. International Granulation Workshop, Jul 2015, Sheffield, United Kingdom. 2015. [hal-01604549](https://hal.science/hal-01604549)

HAL Id: hal-01604549

https://hal.science/hal-01604549

Submitted on 2 Jun 2020

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<figure><img src="image_1.png" /></figure>
160. THE SPECIFICATIONS FOR THE SUSTAINABLE-DESIGN
OF THERMO-HYDRO-MECHANICAL PROCESSES OR THE
ELABORATION OF AGGLOMERATED PRODUCTS

Bettina Bellocq, Agnès Duri, Bernard Cuq & Thierry Ruiz

UMR IATE 1208 CIRAD/INRA/Montpellier SupAgro/Université Montpellier – 2 Place Pierre Viala,
34060 Montpellier cedex 5, France.

E-mail: bellocq@supagro.inra.fr

Although scientific works have been conducted over the 15 last years, theory of agglomeration are still missing to understand the uses of reactive powders during the processing of durum wheat into agglomerated couscous grains. Due to the multiplicity of mechanisms, the end product properties cannot be predicted. More over the current industrial process is particularly poorly eco-efficient and energy consuming. The objective of the present work is to generate relevant data for the specifications for the sustainable-design of thermo-hydro-mechanical processes for the elaboration of couscous grains. Our approach is based on coupling experimental and modeling works to investigate the contributions at complementary scales: at the products and process scale. Knowledge integration is based on the elaboration of functional diagrams using a Dimensional approach (DA). The representation by dimensionless numbers for water/solid particle meeting, particle sticking and grain mobility, associated with the governing ratios which characterize the mechanisms of mass and energy transfers, allows to propose specific diagrams to describe the couscous process. Dimensional analysis (DA) is considered as a way to allow the decomposition of the whole couscous process. Dimensional Analysis is first conducted to investigate the rotating durum process under different trimming parameters and process conditions. The target parameters have been chosen from the physicochemical properties of the final agglomerated powder.
## Introduction & Objectives

We improve theoretical foundations to understand the uses of **thermo-hydro-mechanical paths of powders reactivity** during the process of durum wheat into **agglomerated couscous grains**. The current industrial process is poorly eco-efficient and energy consuming. There is a need for a **multidisciplinary approach** including **cereal technology**, **product engineering**, **soft-matter science** and **granular matter physics**.

<figure><img src="image_2.png" /></figure>

Major aims of this work are:

1. To identify and model **the structuration mechanisms** developed under thermo-hydro-mechanical stresses.

2. To compare **the energy consumption** at the process level to the energy needs for local structuring mechanisms.

3. To represent the conceptualization process using **dimensionless analysis**.

### 1. Mechanistic approach

The main goal of the mechanistic approach is to determine the specific contribution of the **powder reactivity** during agglomeration processing. Durum wheat powders undergo **reversible and irreversible physicochemical changes** when submitted to **thermo-hydro-mechanical stresses** in relation with its composition.

<figure><img src="image_3.png" /></figure>

Our objective is to specifically evaluate:

- The contribution of **physical characteristics** of particles to the **agglomeration mechanisms**.

- The contribution of **proteins** to the **irreversible physicochemical mechanisms**.

This task leads to the establishment of **specifications** concerning the proteins in durum wheat. This approach will allow to identify the **characteristics times and lengths**, and estimate the **energy requirements**, for each physical and physicochemical mechanisms that are induced by the successive stages during processing.

<figure><img src="image_4.png" /></figure>

### 2. Twin product/process engineering approach

Our work is focused on **morphogenesis and structuring mechanisms**, using different technology modes and process conditions. In parallel, we realize measurements of the **energy consumptions** to estimate the **energy cost** of the processing of durum wheat semolina in couscous and the impact of the raw **material diversity**.

<figure><img src="image_5.png" /><figcaption>Impact of the water content on the diameters of agglomerates (Hafsa I. et al., 2014)</figcaption></figure>

**Technology modes** are selected to generate different hydro-thermo-mechanical stresses during process:

- Mechanical or pneumatic **mixing process**.

- Rolling with **inclined rotating cylinder**.

- Different **cooking** and **drying technologies**.

<figure><img src="image_6.png" /><figcaption>Mixing</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Rolling</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Cooking</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Drying</figcaption></figure>

**Process conditions** are selected by promoting the mechanisms as successive long-times stages or a simultaneous short-times stages and to investigate the impact of:

- Shear

- Water content

- Times

- Temperature

This approach, associated with experiments at different scales and with different pilot designs and combined with dimensional analysis, will conduct to generate **specifications for the couscous process re-design**.

### 3. Knowledge integration approach

Knowledge integration approach, based on **conceptualization approaches**, allows the elaboration of **functional diagrams** using dimensionless criteria. **Dimensional Analysis** (DA) is a way to allow the decomposition of the whole couscous process in a "relevant number base" (dimensionless numbers), involving many complex mechanisms.

<table><caption>Example of a dimensional matrix on an inclined rotating cylinder</caption><thead><tr><th rowspan="2">Dimensional variables</th><th rowspan="2">Symbol</th><th colspan="3">Fundamental quantities</th></tr><tr><th>M</th><th>L</th><th>T</th></tr></thead><tbody><tr><td>Lenght of cylinder</td><td>L</td><td>0</td><td>1</td><td>0</td></tr><tr><td>Acceleration of gravity</td><td>g</td><td>0</td><td>1</td><td>-2</td></tr><tr><td>Diameter of cylinder</td><td>D</td><td>0</td><td>1</td><td>0</td></tr><tr><td>Angle of cylinder</td><td>α</td><td>0</td><td>0</td><td>0</td></tr><tr><td>Rotation number</td><td>N</td><td>0</td><td>0</td><td>-1</td></tr><tr><td>Input Agglomerates flow rate</td><td>D<sub>b</sub></td><td>1</td><td>0</td><td>-1</td></tr><tr><td>Input Agglomerates density</td><td>ρ<sub>p</sub></td><td>1</td><td>-3</td><td>0</td></tr><tr><td>Input Agglomerates median diameter</td><td>d<sub>p</sub></td><td>0</td><td>1</td><td>0</td></tr><tr><td>Outlet agglomerates median diameter</td><td>d<sub>50</sub></td><td>0</td><td>1</td><td>0</td></tr></tbody></table>

The approach is to initially list the influential variables to create a dimensional matrix. The **dimensional matrix** allows to express the process relationship linking the **target parameter** to the **key process parameters**. The target parameters are chosen from the physicochemical properties of the final agglomerated powder.

<figure><img src="image_10.png" /><figcaption>Model example to predict the water drop size obtained from different nozzles (Mandato S. et al., 2012)</figcaption></figure>

The diagonalization of the matrix allows to define the coefficients of the dimensionless numbers and the final model. The target parameter values can be mathematically described by the product of **exponential** and **powers laws**.