One Mixer Fulfill Drying and Mixing Technology

01-04-2017

With development of chemical and food process technology, more and more manufacturers prefer to simplify their process and to improve working efficiency. For some typical area, producers need to dry raw material and to be mixed together. In old process, there is a drying system machine before mixing which waste much energy. But now, Vortex MT develops a multi-functional mixer to combine drying, mixing and also cooling together to fulfill complex process in one machine. Since 2008, Vortex engineer started to study and develop heating drying mixer from Europe technology.

How to remove the liquid?
Evaporation (flash and vacuum drying) is a best way to separate liquid and solid. It is not enough if only use heating because the water will still remain in the vessel. So, heating + vacuum is a double solution to evaporate water and to draw off water vapor at the same time. However, drying result is proportional to vacuum value. Generally speaking, our engineer suggest customer to use at least -0.6-0.8 barg but if need better drying effect, the vacuum value need to be full vacuum (-0.9-1 barg).
moisture content & drying time vapour pressure solvents

Two Types of moisture
There are two types of moisture which is surface moisture (free water) and bound & entrapped moisture (bound moisture water). It is very easy to dry surface moisture product such as wet sand. However, bound moisture such as starch is complicated and takes long time to dry. There are two ways to dry the bound moisture product. One is to make full vacuum as high as possible to reduce left air space inside vessel because only 5-10% air space will also influence on final drying result. Another way is to add nitrogen into vessel to let air out.

surface moisture

Heating Medium and Vacuum Drying
Medium: Hot Water, Hot Air, Steam, Hot Oil
Temperature: 0-350 degree
Vacuum Pump: Condenser, Vacuum Filter, Water Circulate Vacuum Pump

Some Tips on Drying Mixer
No matter conical screw mixer, ribbon blender and ploughshare mixer, they all can be used in heating and drying function. However, Vortex engineer think ploughshare mixer is a better one to fulfill complex process because it is versatile and can be designed in many options such as negative or positive pressure, vacuum, heating, cooling, drying and reacting. In mixer design, there are some important tips need to be focused:
A. Pressure
No matter positive or negative pressure, it is an important issue for mixer manufacturer to design a suitable strength including vessel, jacket, end plate, shaft and drive unit, otherwise, the vessel will be broken easily in the future.
B. Seal
Considering most customers will use this mixer to dry material by high temperature, the seal material is very important and we shall use high temperature resistant seal material such as Teflon. Please be highly noticed that air purge seal is not suitable for drying mixer.
Furthermore, if there is pressure inside vessel beyond 2 barg, the normal teflon packing seal is not enough and it need to be replaced by double faces mechanical seal for main shaft and choppers in ploughshare mixer.
C. Drive Part
According to the knowledge of drying process, it is from material with moisture to paste to semi-powder to dry powder. The shaft of mixer will have high torque demand during semi-powder and liquid stage. So, it has to be run at low speed but with large torque. It is better to use double speed motor or fluid coupling to keep same torque from high speed to low speed. The shaft must also be designed strong enough to meet different challenges.

Ploughshare Mixer
Ploughshare Mixer

In 2011, Vortex MT successfully finished a 2000L ploughshare mixer used in modified starch field and our engineer concluded more experience on drying and mixing technology in order to present best solution to our customers. If you want to know more information about this, please feel free to contact us.