Downstream Processing

A high-temperature vacuum distillation system is used for the distillative purification of high-boiling substances or mixtures of substances. The core components of the system are a degasser, a short-path evaporator, and a thin-film evaporator with a rectification column. The individual units can be interconnected as needed. Particularly for temperature-sensitive substances, it is important to distill them at gentle temperatures under a high vacuum to prevent decomposition.

Technical specifications

• Pressure range 0.005 – 100 mbar
• Temperature ranges 200 / 250 / 350 °C
• Degasser, short-path evaporator 0.4 m²
• Thin-film evaporator 1.0 m² with rectification column
• Throughput 50 kg/h
• Material 1.4404 / 1.4571
• ATEX-compliant (Zone 2, T1/T2)
• Inert product filling into drums or IBCs

Pilot process

The high-temperature vacuum distillation unit is used, among other things, for the distillative purification of tall oil. (Crude) tall oil is a byproduct of pulp production. It consists primarily of tall oil fatty acids (particularly oleic acid and linoleic acid), resin acids (mainly abietic acid), and neutral and unsaponifiable components, the main component of which is β-sitosterol. In the degasser, highly volatile impurities are first separated out. In the flash evaporator, the fatty and resin acids are then roughly separated from the unsaponifiable components. In the subsequent thin-film evaporator with a rectification column, fatty acids with a purity of more than 95 percent can be recovered. Fatty acids serve, among other things, as feedstock for downstream products such as fatty acid epoxides.

Applications

• Fatty acid processing
• Purification of phenolic feedstreams
• Fractionation of naphtha, kerosene, diesel, etc., from crude oil

We use various technologies for the drying of intermediates and products. For concentrating solutions or suspensions, we can gently evaporate under vacuum at Fraunhofer CBP (300 L/batch) and subsequently dry further under vacuum (30 L/batch in the cabinet dryer or 600 L/batch in the vacuum filter dryer) as well as spray drying (7.5 kg/h) or freeze drying (24 L/batch).

We are happy to provide larger drying capacities, also under hygiene requirements for the food sector, through our partner network.

Laboratory facilities for evaporation, freeze drying and spray drying are available at Fraunhofer IGB in Stuttgart for investigating the feasibility and drying of smaller sample quantities. The nozzle variants available here for spray drying enable both the spraying of homogeneous solutions (two-substance nozzle) and the spraying of two liquids that are unmixable with each other (three-substance nozzle).

The superheated steam drying process developed at Fraunhofer IGB allows volatile substances to be separated during the drying step and condensed for further use or separate disposal.

Our high-pressure extraction system enables the enrichment or isolation of valuable compounds from biomass. This specialized process is characterized by the fact that carbon dioxide exhibits excellent solubility under supercritical conditions and is separated from the resulting extract without leaving any residue through decompression following the extraction process. By using ethanol as a co-solvent and employing multiple expansion stages, the selectivity of the extraction and fractionation can be further enhanced. As an alternative, we also use liquid propane as an extraction agent for the extraction of nonpolar valuable substances.

Technical specifications

Temperature up to 80 °C

Extraction agents

• Propane (up to 100 bar); 10 kg/h
• scCO₂ /+ EtOH (up to 500 bar); 10 kg/h

Material to be extracted

• Solids (in a 2-L batch extractor, particle size min. 100 µm)
• Suspensions in a countercurrent column, flow rate 2 kg/h, particle size min. 1–10 µm, solids content 0.5–20%

Separation of valuable substances

• One- to three-stage with scCO₂
• Three-stage with propane
• Extraction agent recovery

Material 1.4571 / 1.4410, suitable for seawater

ATEX-compliant (Zone 1, T3)

Pilot process

Currently, Fraunhofer CBP is primarily investigating the extraction of valuable compounds from algal biomass. Microalgae can produce a wide variety of substances that are of interest to the food industry. Depending on the species used and the cultivation conditions, they produce large quantities of fatty acids (as triacylglycerides), proteins, polar membrane lipids (containing omega-3 fatty acids), as well as various carotenoids and phytosterols. For example, the successful extraction of beta-carotene from the microalga Dunaliella salina has already been demonstrated.

The reaction unit consists of a 100-liter enameled steel reactor with a condenser and exchange tanks. The system can be used to carry out liquid-phase reactions at temperatures ranging from –20 °C to +200 °C. The reactor is temperature-controlled by a thermostat. The condenser allows solvents to be separated by distillation and reaction products to be concentrated. Alternatively, operation under reflux is possible. Reactions and distillation take place at atmospheric pressure or under vacuum at pressures down to approximately 20 mbar (abs). The vacuum is generated by a vacuum pump and regulated to the desired setpoint.

In the extraction unit, separation processes of liquid media are investigated using liquid-liquid extraction at atmospheric pressure and temperatures up to 50 °C. To optimize mass transfer, the two phases are passed in countercurrent flow through the extraction column. By varying operating parameters such as stirrer speed or flow rate, we create optimal conditions for the separation process under investigation.

Technical specifications

Reaction unit

• Distillation / reflux distillation possible
• Material: Enameled steel / borosilicate glass / PTFE
• Volume: 100 liters
• Pressure: 50 – 1013 mbar
• Temperature: –50 – 200 °C
• Dosing pumps: max. 80 – 120 L/h
• ATEX-compliant (Zone 2, T3)

Extraction unit

• Agitated countercurrent extraction column with two heatable feed tanks (100 L each) and two product tanks (100 L each)
• Material: borosilicate glass and PTFE
• Throughput: up to 84 L/h
• ATEX-compliant (Zone 2, T3)

Accessories

• Mobile filter unit for pressure and vacuum filtration

Pilot process

The reaction and extraction plant is used, among other things, for the extraction of phytosterols from tall soap. Tall soap is a byproduct of the pulp industry and contains at least 2 percent sterols, primarily β-sitosterol, which, after separation and purification, are used in the cosmetics industry or as dietary supplements. Through a multi-stage process consisting of continuous liquid-liquid extraction, crystallization, filtration, solvent recovery, and drying, we produce phytosterols with a purity of more than 98 percent.

Biobased furan derivatives, such as 2,5-furandicarboxylic acid (FDCA), are increasingly gaining in importance, in particular as biogenic building blocks for polymer applications. The Fraunhofer Center for Chemical-Biotechnological Processes CBP is conducting intensive research into the separation and purification of furan derivatives from process water of the hydrothermal conversion of raw materials containing lignocellulose, using a variety of thermal, mechanical and physico-chemical separation methods. Intensive research and development has been carried out in projects including those funded by the German Federal Ministry of Education and Research (BMBF), ”KomBiChemPro” and ”BBChem”, as well as the project ”SteamBio”, ”BioSPRINT”, and ”Circular-C” funded by the EU.

Separation by cross-flow membrane filtration

We use cross-flow membrane systems to separate off the dissolved and undissolved constituents. The aim is to separate polymers from monomers and to reduce the water content to optimize the purification process energetically. Cross-flow membrane filtration also plays a central role in the separation of temperature-sensitive substances, such as 5-hydroxymethylfurfural (5-HMF) and formic acid. Furfural derivatives can also be successfully separated from the process water using rectification, which we have demonstrated at the pilot scale with a throughput of 2.5 kg/h. Investigations into liquid-liquid extraction and adsorption/desorption revealed targeted separation of the carboxylic acids from furan derivatives. In this case, we were able to successfully demonstrate the essential feasibility of separating furan derivatives in process waters from hydrothermal conversion up to the 100-liter scale.