CHEMICALS & PLASTICS
filter cake drying
No matter what method and device is used for upstream mechanical solid-liquid separation – be it filter press, band-pass filter, candle filter, decanter, centrifuge, or suction filter – to achieve the desired final moisture content, a thermal drying mixer is required downstream. The vertical HVW and HVM series MITRAVA conical dryers have defined the chemical industry drying technology standard ever since AVA introduced it on the market. They allow you to achieve residual moisture in the ppm range and, due to their special design, guarantee high availability and minimum maintenance. As an alternative to vertical contact drying mixers, AVA also supplies the AVA horizontal HTC and HTK series shovel drying mixers. These machines are equipped with Becker shovels and work continuously or in batch operation. Heating temperatures up to 800°C in vacuum operation can be achieved, depending on the application.
When it comes to homogenizing and drying agribusiness powders and granulate formed products, the HVW and HVM series vertical mixers and vertical drying mixers are the tools of choice. The fragile products are processed rapidly and particularly gently, and the reproducibility of recipes is ensured. The special shape of the mixing container means that the product is almost fully discharged at the bottom side while the agitator is running. For cleaning purposes, the machines are highly accessible or alternatively, cleaning processes can be automated. Design and construction are carried out in accordance with GMP, and there is a wide choice of application-specific variants.
In addition to individually supplied drying mixers with integrated heated vapor filters, AVA also supplies complete drying assemblies that include a condensing unit or vacuum condensing unit and heater. Here, the ability to recover the condensate or used solvents and feed the materials back into the process or use them in other applications represents a significant financial benefit.
battery masses i
High-performance AVA mixers are used for mixing of battery base mixes. Here, filter cake, additive powders, and liquids are intensively mixed. The HTC type batch mixers are made of stainless steel and equipped with a CIP cleaning system. The proven AVA agitator contains adjustable shovels, which, depending on the task, allow a wall clearance of between 1 mm and 25 mm. Separately driven choppers ensure agglomerate-free mixing. A lip seal or liquid-lubricated, double mechanical seal ensures optimal shaft sealing.
drying of plastic powders
"Continuous stripers" for polymer powder manufacturing
Often in the production process for plastic powders, a solvent such as methanol or alcohol is used, which then has to be completely evaporated again at a later stage. Depending on the consistency of the product, evaporating the solvent is not always particularly easy and the drying process often finishes with residual moisture content in the range of 3% - 5%. At this point, evaporation has to be supported by means of adding pre-heated nitrogen, dry-saturated steam or hot air, the so called “stripping” process, in order to achieve a residual moisture content of 0%. AVA supplies a “continuous stripper” especially for this problem formulation in an ATEX-conforming design, with a special agitator, which supports the flow of the plastic powder with the carrier medium, but also serves to guarantee heat transfer by means of a cylinder jacket. Due to the geometry of the agitator, a high level of re-mixing is achieved and the retention time in the dryer is increased. This guarantees a constant temperature and humidity in the entire dryer as well as a homogenous and dry end product.
coating of plastic granules
In order to increase the production output of extruders and injection moulders, the flow and processing characteristics of plastic granules has to be modified. Especially for polyamides (PA) and polystyrene (PS) this occurs by means of powdering (coating) with powder additives. In doing so, two different methods are employed. The pure dry mixing of plastic granules with the powder additives and the moistening of plastic granules with liquid binding agents / powder additives. With both methods it is necessary to create an extremely homogenous end-product with very high repeatability, in order to guarantee a sustained product quality, as any deviation in quality immediately shows up as a flaw in the surface during the subsequent processing in the extruder or the injection moulding machine.
The AVA horizontal mixers of type HTC (batch operation) and HTK (continuous operation) achieve best results in terms of homogeneity under high throughput performance. As the mixing and detention times in the mixers are very short, a fast moistening of all plastic granules with the binding agent and additives without product damage is vital. For this reason the machines are adapted to the corresponding customer’s requirements and are designed for gentle or turbulent mixing. This mixing optimisation enables AVA’s customer’s high quality requirements to be achieved superbly for both processes.
The high availability of the AVA mixers and the constant extremely good qualities of the intermediate and end products are the guaranteed advantages in daily operation for the benefit of our customers.
SAP (super absorbent polymers)
Superabsorbers (SAP, superabsorbent polymers) are plastics, which are able to absorb 1000 times their own weight in liquid. The main areas of application are baby nappies as well as products for female hygiene and incontinence care. The problem formulation for AVA was to improve the existing SAP product quality, to increase the throughput of the overall plant, and to enable several process stages to be undertaken in one machine. Due to the product changeover from batch operation to continuous operation with AVA mixers of type HTK, the throughput performance of the overall plant could be increased by more than 50%. Turbulent mixing with the adjustable AVA paddles enabled the addition and dispersing of liquid additives into the AVA mixer. The upstream process stage for moistening the SAP powder was thereby saved.
Thanks to this increase of capacity, the existing plant could be used by our customer to considerably reduce production costs, without having to replace the complete plant technology.
grading screen for pelletized products
Custom designed specialist fertilizer screens type SNS are used for 'cutting' the product at 4 & 2mm. The screens are mounted on a 30 deg. incline, whilst utilising a contra-rotating eliptical vibratory motion. Longitudinal tensioned decks are fitted to ensure a constant bed depth across the screen deck for the most efficient screening.
fully dust proof screens
The specialist screens can be equipped with fully dust proof static hoods, and including dust extraction facilities if required. The hood can be designed to include motor supports and discharge chutes, for a fully sealed self contained unit, to prevent any environmental contamination.