DOI: 10.17877/tudodata-2025-mih7lvgh
title: Replication Data for: Boosting Process Efficiency Through Concentrate Recycling in Suspension Melt Crystallization

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 &lt;title&gt;Project and Dataset Description&lt;/title&gt;
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&lt;h1&gt;PROJECT DESCRIPTION&lt;/h1&gt;

&lt;p&gt;
Suspension melt crystallization is a low-energy purification technology with growing potential in fields such as water and wastewater treatment. To increase melt (water) yield without compromising purity, we studied the impact of internal concentrate recycling on the performance of an integrated suspension melt crystallization pilot plant combining a scraped cooling crystallizer and a mechanical piston-type wash column. 
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&lt;p&gt;
Systematic recycling experiments were conducted for three aqueous model systems NaCl–H₂O, MgSO₄–H₂O, and a mixed NaCl/MgSO₄–H₂O solution under controlled suspension densities and stepwise decreasing operating temperatures. A key observation is that the process concentrate concentration deviates from solid–liquid equilibrium (SLE), primarily due to heat-transfer limitations that limit crystal growth despite near-equilibrium operating temperatures.
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&lt;p&gt;
Additionally, the study identifies challenges related to ice entrainment in the recycle and demonstrates partial mitigation strategies to improve process stability. Overall, concentrate recycling shifts the process trajectory within the SLE diagram, enabling higher concentrate levels and maximizing water yield while maintaining high purification efficiency (&gt;99%) and stable operation. The results further indicate that the developed operating strategies are transferable across systems with both known and unknown phase equilibria. Overall, the study highlights that controlled concentrate recycling can enhance production capacity while preserving purification efficiency. 
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&lt;p&gt;
Overall, the study highlights that controlled concentrate recycling can enhance production capacity while preserving purification efficiency.
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&lt;hr&gt;

&lt;h1&gt;DATASET DESCRIPTION&lt;/h1&gt;

&lt;p&gt;
This dataset provides a comprehensive collection of raw experimental data and visual representations from crystallization experiments. The focus is on investigating the influence of an internal concentrate recycle in a suspension melt crystallization plant on process performance, specifically water yield and purification efficiency.
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&lt;h2&gt;1. General Structure&lt;/h2&gt;

&lt;p&gt;The dataset is organized into two main categories:&lt;/p&gt;

&lt;h3&gt;Figures&lt;/h3&gt;
&lt;ul&gt;
 &lt;li&gt;.opju files (OriginLab project files) containing experimental data and corresponding plots.&lt;/li&gt;
&lt;/ul&gt;

&lt;h3&gt;Raw_data&lt;/h3&gt;
&lt;ul&gt;
 &lt;li&gt;Excel files with raw experimental data for Test Series 1 and 2 (RAW_DATA_TS1_TS2), including two subfolders:
 &lt;ul&gt;
 &lt;li&gt;RAW_DATA_TS1 (Test Series 1)&lt;/li&gt;
 &lt;li&gt;RAW_DATA_TS2 (Test Series 2)&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;Particle videos with analyzed particle size distributions for Test Series 1 (RAW_DATA_PSD_TS1_NaCl_1_3.5), including:
 &lt;ul&gt;
 &lt;li&gt;Subfolders containing videos for each individual experiment&lt;/li&gt;
 &lt;li&gt;One subfolder containing PSD results for all experiments&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h2&gt;2. Substance Systems&lt;/h2&gt;

&lt;p&gt;The experiments were conducted using different substance systems in Test Series 1 and 2:&lt;/p&gt;

&lt;ul&gt;
 &lt;li&gt;&lt;strong&gt;Sodium chloride (NaCl)&lt;/strong&gt; as impurity in aqueous solution
 &lt;ul&gt;
 &lt;li&gt;Feed concentrations: 1 wt% and 3.5 wt%&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;Magnesium sulfate (MgSO&lt;sub&gt;4&lt;/sub&gt;)&lt;/strong&gt; as impurity in aqueous solution
 &lt;ul&gt;
 &lt;li&gt;Feed concentration: 3.5 wt%&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;NaCl and MgSO&lt;sub&gt;4&lt;/sub&gt;&lt;/strong&gt; in equal proportion as impurities in aqueous solution
 &lt;ul&gt;
 &lt;li&gt;Feed concentration: 1 wt%&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;
Due to internal recycling, the operating temperature was reduced on each experimental day in order to decrease the solution concentration.
&lt;/p&gt;

&lt;h2&gt;3. File Contents and Data Description&lt;/h2&gt;

&lt;h3&gt;3.1 opju Files (OriginLab Project Files)&lt;/h3&gt;

&lt;p&gt;These files contain processed experimental data and visualizations:&lt;/p&gt;

&lt;ul&gt;
 &lt;li&gt;&lt;strong&gt;Concentration trajectories and suspension densities&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Three subfolders for each substance system&lt;/li&gt;
 &lt;li&gt;Each contains two worksheets and corresponding graphs:
 &lt;ul&gt;
 &lt;li&gt;Concentration trajectories in the solid–liquid equilibrium (SLE) diagram&lt;/li&gt;
 &lt;li&gt;Suspension densities&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;Data provided for both test series&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;

 &lt;li&gt;&lt;strong&gt;Particle Size Distribution (PSD)&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;One worksheet and graph containing cumulative volume distributions&lt;/li&gt;
 &lt;li&gt;Includes all NaCl experiments from Test Series 1 and both feed concentrations&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;

 &lt;li&gt;&lt;strong&gt;Purification efficiency&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;One graph showing purification efficiency&lt;/li&gt;
 &lt;li&gt;Covers all three substance systems for experiments conducted in Test Series 1&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;

 &lt;li&gt;&lt;strong&gt;Yield&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;One graph showing water yield&lt;/li&gt;
 &lt;li&gt;Covers all three substance systems for experiments conducted in Test Series 1&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h3&gt;3.2 RAW_DATA_TS1_TS2 Excel Files&lt;/h3&gt;

&lt;h4&gt;File naming convention:&lt;/h4&gt;

&lt;ul&gt;
 &lt;li&gt;&lt;strong&gt;Test Series 1 (TS1):&lt;/strong&gt;&lt;br&gt;
 Impurity_Date_Feed concentration_Set point temperature for recycling
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;Test Series 2 (TS2):&lt;/strong&gt;&lt;br&gt;
 TS2_Impurity_Date_Start concentration of experiment day
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h4&gt;Test Series 1 contains:&lt;/h4&gt;

&lt;ul&gt;
 &lt;li&gt;&lt;strong&gt;Raw data from the human–machine interface (HMI):&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Temperature data (process medium, melt loop, cooling medium)&lt;/li&gt;
 &lt;li&gt;Light transmission value&lt;/li&gt;
 &lt;li&gt;Scraper blade energy input&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;Raw data from LabVIEW:&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Inline conductivity data&lt;/li&gt;
 &lt;li&gt;Pressure data from the wash column melt loop&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;Offline conductivity measurements:&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Conductivity data for each sample taken during the process used to calculate salt concentration&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h4&gt;Test Series 2 contains:&lt;/h4&gt;

&lt;ul&gt;
 &lt;li&gt;&lt;strong&gt;Concentrations:&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Conductivity data for each sample taken during the process used to calculate salt concentration&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;&lt;strong&gt;Results:&lt;/strong&gt;
 &lt;ul&gt;
 &lt;li&gt;Raw data from the human–machine interface (HMI):
 &lt;ul&gt;
 &lt;li&gt;Temperature data (process medium, melt loop, cooling medium)&lt;/li&gt;
 &lt;li&gt;Light transmission value&lt;/li&gt;
 &lt;li&gt;Scraper blade energy input&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;Raw data from LabVIEW:
 &lt;ul&gt;
 &lt;li&gt;Inline conductivity data&lt;/li&gt;
 &lt;li&gt;Pressure data from the wash column melt loop&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h3&gt;3.3 RAW_DATA_PSD_TS1_NaCl_1_3.5&lt;/h3&gt;

&lt;p&gt;
Particle Size Distribution (PSD) results for the NaCl–water system at both feed concentrations.
&lt;/p&gt;

&lt;h4&gt;PSD Results folder&lt;/h4&gt;

&lt;p&gt;
Excel files named:&lt;br&gt;
PSDResults_Impurity_Date_Feed concentration_Set point temperature recycling
&lt;/p&gt;

&lt;ul&gt;
 &lt;li&gt;Cumulative distribution function (Q&lt;sub&gt;i&lt;/sub&gt;)
 &lt;ul&gt;
 &lt;li&gt;Characteristic variables and summation function&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;Characteristic parameters:
 &lt;ul&gt;
 &lt;li&gt;X&lt;sub&gt;10&lt;/sub&gt;, X&lt;sub&gt;50&lt;/sub&gt; (median), X&lt;sub&gt;90&lt;/sub&gt; (percentile values)&lt;/li&gt;
 &lt;li&gt;Agglomeration degree (Ag)&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
 &lt;li&gt;Probability density function (q&lt;sub&gt;i&lt;/sub&gt;):
 &lt;ul&gt;
 &lt;li&gt;Size distribution data for single crystals and agglomerates&lt;/li&gt;
 &lt;/ul&gt;
 &lt;/li&gt;
&lt;/ul&gt;

&lt;h4&gt;Other folder&lt;/h4&gt;

&lt;p&gt;
Folder name format:&lt;br&gt;
Impurity_Date_Feed concentration_Set point temperature recycling_QICPIC
&lt;/p&gt;

&lt;ul&gt;
 &lt;li&gt;Particle videos for each individual experiment&lt;/li&gt;
&lt;/ul&gt;

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description: Added related publication