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Benefits of Pulse Combustion Drying (PCD) Technology

The PCD technology is environmentally friendly, with a high energy and thermal efficiency. The lower pressure required for mixture delivery and smaller equipment footprint also add to the cost effectiveness of the process. The most attractive benefit of PCD is the profitable high quality food grade powder that it delivers as the input to a circular bio-economy.

Environmentally Friendly

A common environmental challenge with dryers is the formation of NOx gasses produced by boilers to provide energy for indirect dryers’ heat exchangers. The flame temperature is kept at an optimal temperature for efficiency, and this allows for the formation of NOx gasses. Despite the heat exchanger of the indirect drying system ensuring the dried product has no detectable NOx levels, the flue gas usually contains recordable levels of NOx (fuel and combustion temperature dependent).

In contrast, the flame temperature in the PCD burner is controlled to keep it well below 1300 °C to ensure that only negligible concentrations of NOx and other dioxins are formed. As a result, no significant levels of NOx or any dioxins are detected in the dried product and flue gas. This is especially advantageous in drying foods and bio-products destined for human consumption.

More energy efficient

The energy efficiency of PCD is significantly (up to 50%) better than its nearest rival. When coupled with concentration processes and high solids content drying, PCD has definite advantages over traditional technologies.

The energy consumption of PCD dryers is 1.15 kW/kg water evaporated (thermal and electric). Studies indicated that the energy consumption of spray drying processes can be as high as 2.3 kW/kg (8.4 GJ/metric ton).

Pulse Combustion Dryers require less air than conventional dryers which results in smaller drying chambers and lower electrical consumption for smaller fans. Due to simple product injectors and smaller fans, running costs are 20-30% lower than spray driers.The energy efficiency of PCD is significantly (up to 50%) better than its nearest rival. When coupled with concentration processes and high solids content drying, PCD has definite advantages over traditional technologies.

Higher thermal efficiency

The extremely short drying time indicates that the rates of heat and moisture transfer to and from the wet material are highly efficient, respectively. The advantage of this aspect of PCD ensures that sufficient energy is absorbed by the evaporating water allowing little increase in the temperature of the solids. This protects the quality attributes (nutritional value, colour, taste, and aroma) of the solids better than all the other drying methods, except freeze drying. Freeze drying provides good quality powders but is more expensive in most powder drying applications.

The short residence time of powders in a PCD allows for faster material throughput.

Higher quality of Dried Powder

The short residence time limits the exposure of product and the effectively lower product temperatures mean reduced denaturing of proteins and improves the level of available digestible protein. PCD also inactivates enzymes and harmful micro-organisms.

Overall, when drying food or by-products of processed food, the major quality parameters of the dried product such as natural colour, flavour, retention of nutrients (proteins, fats, antioxidants, etc.), re-hydration properties and chemical stability are minimally affected by PCD.

Lower pressure required for mixture delivery

To effectively atomize viscous mixtures in a spray dryer, the mixture is delivered to the spray nozzles at high pressure (12 – 30 bar). In a PCD dryer the viscous mixture is delivered to the injector nozzle at 1 - 2 bar via a low-pressure pump. The result is that mixtures with higher TS content can be pumped through the delivery system.

Lower maintenance cost

No high pressure pumps or high rotating equipment only a low pressure system ensures low maintenance. The atomization nozzle is so large — essentially, it’s an open pipe — abrasive and corrosive materials cause little harm.The parts in the atomizing process therefore requires little maintenance.

Reduced pre-treatment steps – shorter process

In atomizers utilising spray nozzles, the nozzle apertures are small. Viscous mixtures may contain small quantities of fibrous materials, causing nozzle blockage. It therefore requires a pre-treatment filtration step to prevent blockages. No pre-treatment filtration step is necessary in PCD systems because it can comfortably handle fibres up to 3mm long in the atomization nozzle which is essentially an open pipe.

Smaller equipment footprint

When comparing drying units with the same powder production rate, it can be expected that the PCD dryer will occupy a significantly smaller floor area.

Seasonality of Agricultural Products

When drying agricultural products the PCD can accommodate a variety of these products in the same dryer throughout the year. This ensures an economical viable plant with a possibility of valorized output products the whole year round.

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