Process description

CPF™ (Concentrated Powder Form) and PGSS™ (Particles from Gas Saturated Solutions) are spray processes for powder generation. CPF™ is used to load liquids on powders (liquid load up to 90 %, depending on carrier), while PGSS™ is used for the generation of powders from melts and for the encapsulation of ingredients.

Both processes normally do not involve drying. Temperatures in the spray tower are low after the nozzle due to the Joule-Thomson effect. CPF™ and PGSS™ should therefore not be confused with spray drying.

Powder generation with high pressure spray processes
CPF™ and PGSS™

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CPF™ process

The CPF™ process generates powders from liquids, which are not solidified during spraying. First the liquid and the gas (CO₂) are pressurized and mixed together in a static mixer. Then the mixture is expanded through a nozzle into a spray tower. The CO₂ expands rapidly, cools down due to the Joule-Thomson effect and creates a fine spray of droplets. A powdery carrier is added concurrently, which binds the droplets, so that a free flowing powder with a liquid load up to 90 wt.% is formed. Fine particles are separated in a cyclone or filter. The process was patented under patent number WO9917868.

Essential oils and other liquids like plant extracts, flavours, vegetable oils and fats, vitamins, alcoholic liquids or aqueous liquids can be processed. The process is suitable both for low viscous and high viscous liquids. Emulsions and suspensions can be processed as well and remain stable in powder form.

A wide range of powder carriers (more than 500) have already been tested like starch, silicic acid, celluloses and sugars. Particle sizes are in the range of 5 µm to 2 mm, bulk densities vary between 50 kg/m³ and 1400 kg/m³. The achievable load depends on the bulk density of the carrier. Low density, porous carriers allow high liquid loads, because the fine droplets infiltrate the porous carriers, while non-porous carriers lead to adsorption of the liquid or agglomeration by capillary forces.

The main advantages of the CPF™ process are low gas consumption, inert atmosphere and low temperatures. Oxygen sensitive, temperature sensitive and high volatile liquids can be processed. Aroma losses are reduced. A wide range of liquids and carriers can be used which allows tailor-made product design of free flowing powders with high liquid loads.

Powder Composites


adsorption	agglomeration open composites (PGSS™ and CPF™)	impregnation	encapsulated liquid closed composites (PGSS™)

PGSS™ process

The PGSS™ process produces particles by spraying gas saturated solutions. A substance is melted, mixed with the dense gas and then expanded via a nozzle into a spray tower. The dense gas dissolves partly in the melt and reduces the viscosity. After the expansion the solubility is immediately reduced and the volume increase of the disappearing gas causes the liquid to disintegrate into tiny droplets. Due to the Joule-Thomson effect the gas cools down and consequently the droplets solidify almost immediately. The powder product is collected on the bottom of the spray tower. Finer particles are removed from the gas in a cyclone or filter. The process was patented under patent number WO9521688.

Morphologies of the particles depend on processing parameters like pressure, temperature, mass flow and gas to product ratio. Spheres, porous spheres, porous particles, micro-foams or fibers can be generated.

Morphologies (PGSS™)


spheres	porous spheres	porous particles	micro foams	fibers

Apart from powders from pure substances also composites can be produced. In this case two vessels are used for the raw materials. In the first vessel the shell material (e.g. a polymer, fat or wax) is melted. The second vessel contains the liquid substance. Both materials are pressurized and mixed with supercritical CO₂ in the static mixer. Micro droplets of the liquid substance are formed in the molten encapsulating material. The emulsion is expanded through a nozzle into a spraying tower and forms fine droplets. Due to the Joule-Thomson effect the gas is cooling down rapidly and withdraws heat from the sprayed substances, so that the shell material solidifies. Depending on processing parameters open or closed composites are formed together with the liquid.

Powders can also be generated from two substances, which are solid at ambient temperature. In this case both have to be melted, pressurized, mixed with supercritical CO₂ and sprayed. In this way e.g. immiscible melts or reactive blends can be pulverized.

Advantages of the PGSS™ process are low gas consumption (normally 0,1 - 2 kg gas/kg powder), inert atmosphere and low thermal stress. Spray towers are relatively small and scale-up can easily be realized based on our experience. PGSS™ is applicable for a multitude of substances including low melting, high viscous and reactive compounds. The powders have tailor-made properties with adjustable morphology (bulk density 90 kg/m³ - 600 kg/m³) and particle size (500 nm to 1000 µm).

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