Sulzer Crystallization Technology
Fractional melt crystallization: ultra-high purity without solvents
Fractional melt crystallization is one of the most powerful purification techniques available in process engineering. When conventional methods such as distillation reach their limits, because of close boiling points, azeotropes, thermal sensitivity or extreme purity targets, crystallization separates components by their melting behavior instead, at low temperature and without any solvent. Sulzer has been designing and supplying melt crystallization plants for decades, from static and falling film layer crystallizers to suspension crystallization with wash columns.
What is melt crystallization
Melt crystallization purifies a product by partially freezing the melt: the desired component solidifies as a crystal layer or as a suspension of crystals, while impurities stay concentrated in the remaining liquid. Because the heat of fusion is typically several times lower than the heat of vaporization, and because no solvent has to be added and recovered, the process is remarkably energy-efficient and gentle.
Sulzer offers the three industrially proven routes, static, falling film and suspension crystallization, and combines them when needed. Operating close to the melting point protects heat-sensitive and reactive products, and multi-stage operation with recycling of the sweat and residue fractions delivers purities beyond 99.9% that are hard to reach by any other technique.
How fractional melt crystallization works
A step-by-step breakdown of the distillation process that enables precise separation of liquid mixtures
1
Feed and cooling
The molten feed is brought into contact with a cooled surface (static plates or falling film tubes) or cooled in a scraped-surface crystallizer for suspension processes. The temperature is lowered in a controlled profile just below the melting point of the target component.
2
Crystal growth
The pure component crystallizes selectively, as a compact layer on the heat exchange surface or as free crystals in the melt, while impurities remain enriched in the residual liquid phase.
3
Separation of the residue
The impure residual melt is drained from the layer crystallizer, or the crystals are separated from the mother liquor in a wash column for suspension processes.
4
Sweating
The crystal layer is gently warmed to slightly below its melting point. Impurities trapped in pores and at the surface melt first and drain away, further increasing purity.
5
Melting and product collection
The purified crystal layer is melted and collected. Sweat and residue fractions are recycled to the appropriate stage so that overall yield is maximized while the final product reaches the target purity.
Batch Distillation
Azeotropic distillation
Extractive distillation
Continuous distillation
Explore Sulzer’s crystallization portfolio, from static layer crystallizers to suspension crystallization with wash columns
Batch distillation involves processing a fixed volume of liquid the "charge" where components are vaporized, rectified and collected sequentially. This process provides the critical flexibility required for multi-product facilities that must frequently switch between varying feedstocks.
Sulzer’s Excelot™ modular platform streamlines these operations by integrating advanced internals and high-efficiency evaporators, significantly reducing startup times and product loss while ensuring high-purity separation in a single cycle.
Learn more about Excelot™
Pressure swing distillation
Specialized distillation
(Distillation 2.0)
Reactive distillation
Mass Transfer Components
Structured Packing
Over 50 years of design experience makes us the ideal partner. Our MellapakPlus™ packing is a proprietary, high-efficiency solution, often copied but never equaled.
Random Packing
We offer a one-stop solution with a range including traditional and high-performance rings like NeXRing™ and Nutter Rings™, I-Rings™, C-Rings™, P-Rings™, and R-Rings™ in metal or plastic.
Trays
We hold the largest tray portfolio on the market, ranging from conventional fixed and movable valve trays to high-performance chordal downcomer, multi-downcomer, like VGPlus™ (one of the best high-performance trays ever tested at FRI). A specialized design with extremely low tray spacing slit trays as a state-of-art offer while tray are preferred for skid-mounted project.
Slit trays | Sulzer
Internals for Packed Columns
Even the best packing won't reach its full potential without appropriately designed internals. We ensure the perfect design for liquid distributors, supports, and collectors.
Column internals | Sulzer
Sulzer proprietary equipment for distillation
Advanced mass transfer and phase separation internals
Phase Separators and Statics Mixers
Gas-Liquid Separators
Sometimes the gas-liquid separator would be offer as part of the distillation solution while small amount of entrainment leads to concern of product quality, such as fine solids, metal ion and yellowness. We offer high-performance technologies to address those concerns. The portfolio includes KnitMesh™ mist eliminators, Mellachevron™ vane packs, which significantly enhances bulk de-entrainment.
Liquid-Liquid Separators (Coalescers)
In Some of distillation system, designer would make use the power of phase splitting to make separation smarter and more efficient. In order to secure the separation and not letting liquid disperse become noise of the process, Sulzer offer comprehensive portfolio to serve the need:
DC Coalescer™ utilizes proprietary co-knitted materials to enhance droplet growth and separation efficiency. To address stable secondary dispersions where droplets are too fine to settle by gravity,
Dusec™ and Dusec Plus™ are specifically engineered to break emulsions and ensure high-purity phases. Additionally, Mellaplate™ high-performance plate packs accelerate the process by significantly reducing settling distances within the vessel while system may prone to fouling.
Contact an expert
Our technical specialists are ready to help you find the optimal distillation solution for your specific application
Chris Lu
Head Soutions Development
Sulzer Advantage
Proven Process Solution Provider for complex and challenging separations
Full Service Provider for proprietary process equipment and plant solutions, backed by guaranteed performance
Provide solutions from design to operation
Unique technology portfolio and extensive application know-how
Unique experience in combining unit operations
Distillation is a fundamental separation process used to purify and separate liquid mixtures into individual components. It exploits the different boiling points of substances to achieve precise separation, making it essential in industries ranging from petrochemicals to pharmaceuticals.
The core principle: Heat a liquid mixture until it partially vaporizes, then cool and condense the vapor to separate components with different volatilities. Repeat this process to achieve the desired purity.
The choice depends on scale and flexibility. Batch distillation processes a fixed volume sequentially, offering the high flexibility needed for multi-product facilities using our Excelot™ platform. In contrast, continuous distillation is a steady-state operation designed for large-scale, uninterrupted production. Sulzer optimizes continuous processes through DistilCare™, utilizing high-performance internals like MellapakPlus™ to ensure consistent quality and maximum throughput.
Pressure swing distillation is the most effective solvent-free method for breaking azeotropes. By operating two columns at different pressure levels, the azeotropic point is shifted, allowing for high-purity separation in a continuous loop. This approach, supported by Sulzer’s advanced heat integration, significantly reduces OPEX and the overall carbon footprint compared to traditional azeotropic methods that require external chemical agents.
Reactive distillation combines chemical reaction and thermal separation into a single unit. This integration is ideal for equilibrium-limited reactions like esterification. By using proprietary Katapak™ catalytic packing, our solutions remove byproducts simultaneously with the reaction, shifting equilibrium to increase yield. This reduces CAPEX and OPEX by eliminating the need for separate reactors and downstream purification equipment.
Our GT-DWC™ technology consolidates a traditional multi-column sequence into a single shell. This allows for the high-purity separation of three-fraction mixtures within one unit. By reducing the number of reboilers and condensers, DWC technology significantly lowers capital investment and energy consumption, while drastically reducing the equipment footprint on-site.
As part of our "Distillation 2.0" initiative, Sulzer offers VoltaSplit™. This technology enables the electrification of distillation by replacing fossil-fueled steam reboilers with high-efficiency mechanical vapor recompression (MVR). Combined with advanced heat pump integration, this provides a direct pathway to Net-Zero operations by reducing Scope 1 emissions in thermal separation.
To optimize plant performance, we utilize advanced gas-liquid separators like KnitMesh™ mist eliminators and Schoepentoeter™ Plus inlet devices when the vapor line needs to eliminate the liquid droplet and concern behind (eg. solid, heavier component cause yellowness and even metal ion…etc.). For immiscible liquids, our DC Coalescer™ and Dusec Plus™ technologies break primary/secondary dispersions and take long time to be settle in the process equipment. These solutions ensure high-purity phases, minimize contamination of stream and results into lower internal circulation as a more effective separation solution.