One-third of the food produced in South Africa goes to waste – and yet 14 million people suffer from food insecurity.  Agro-industrial waste is major valuable biomass that presents potential solutions to this problem, but only if appropriate technologies are used to valorize it first.

At Sinowatek we create processes that valorize agro-industrial waste streams.  We design and implement ‘fit for purpose’ processes by selecting and integrating state-of-the-art technologies and equipment.

The first step in valorizing a waste stream is the separation of the mixture into solids and liquid.  The solid fraction, still in viscous form, is valorized by drying it with the progressive pulse combustion drying (PCD) technology.

In essence, the PCD method works like this:

The solid fraction (a slurry or paste) is pumped from a tank and injected at low pressure into a high velocity pulsating gas stream.  In milliseconds the pulsating gas stream, with temperatures of 650°C-750°C, produces ultra-fine (5-50μm) droplets and converts the surface moisture of the droplets into super-heated steam, leaving behind a very dry fine powder.  The powder particles have spherical shapes and smooth surfaces.

PCD technology has important advantages when compared to other drying technologies:

• Environmentally friendly

The flame temperature in the PCD burner is controlled to keep it well below 1300°, thereby ensuring that no significant levels of toxic NOx, SOx or any dioxins are formed in the dried product and flue gas.  This is especially advantageous when drying foods and bio-products destined for human consumption.

• Energy efficiency

The energy efficiency of PCD is significantly (up to 50%) better than its nearest rival. Energy savings are achieved by using evaporators to concentrate the product first. Unlike traditional drying technologies, PCD can dry high total solid content suspensions (pastes), ensuring more dried powder for lower energy consumption.

• Higher quality of dried powder

The short residence time in the PC dryer limits the exposure of the product to heat.  The effectively lower product temperature achieves reduced denaturing of proteins and improves the level of available digestible protein.  PCD also deactivates enzymes and harmful micro-organisms.  Overall, when drying food or by-products of processed food, the major quality parameters of the dried product are much better preserved when drying by PCD than by other technologies.

• Cost effectiveness

The smaller air volumes, lower pressure required for mixture delivery, reduced pre-treatment steps and smaller equipment footprint make the process more cost-effective than its competitors.

At the Sinowatek PCD Test Centre materials to be dried can be tested for suitability and compatibility with the PCD drying method.  Process parameters and product quality are established during this process.

Once the correct parameters for the application are established, Sinowatek, as specialist designer and applicator, will provide the process analysis and engineering inputs to design a complete process, to specification, which can receive, process and deliver products for circular economies.

Products successfully dried using PCD include spent brewer’s yeast, fish stick water, prawn, soy pulp, whole blood, apple pomace, chicken and milk, to name but a few.