To treat liquids with numerous impurities to separate these impurities from the liquid or concentrate them, one of the microfiltration methods, which is called “tangential”, is used. It consists of the inlet liquid with impurities circulating along the microfiltration membrane at a high linear velocity, washing the membrane surface. At the same time, a part of the liquid flows through the membrane under the created pressure. The liquid part in which impurities remain is called the concentrate. The liquid part from which the impurities are separated while passing through the membrane is called the filtrate. Tangential microfiltration is very effective in the case of high concentrations of admixtures because it combines two processes: filtration and flushing of impurities from the membrane surface. A stable filtration process can be achieved with a relatively high residual quantity of thick concentrate.
Litech Aqua has extensive experience in the design and manufacture of microfiltration systems for the treatment of various liquids, such as
— saline solutions;
— water, etc.
In particular, the microfiltration system can be used to filter a urea solution, which is further used to prepare a catalytic exhaust gas cleaning agent for diesel vehicles.
The tangential microfiltration plant consists of tubular type microfiltration membranes, a high-capacity pump, a control cabinet with the controller, a set of automation and instrumentation (includes high pressure and dry running relays, analogue pressure sensor, gauges), a set of valves and valves with electric drive and a stainless steel frame. The piping includes concentrate and filtrate piping, wash fluid piping and pneumatic piping.
The tangential microfiltration process is divided into two main stages: the filtration stage and the washing stage.
During the filtration stage, the filtered liquid is pumped from the circulation tank into the circulation path of the microfiltration membranes and returned to the circulation tank. The flow constriction at the outlet of the circulation path creates pressure inside the circulation path. This pressure causes the filtered liquid to pass through the porous membrane walls and, cleaned of impurities, is fed into the filtrate vessel. In the circulating tank, the impurities present in the liquid are gradually concentrated. Depending on the type of liquid, quantity and type of impurities, the amount of concentrate at the end of the filter process will be 5-30 per cent.
The tangential microfiltration unit requires periodic washing. This washing process is multistage. During washing, the filtrate and concentrate remaining inside the unit are displaced into suitable containers. It is followed by washing the membranes with water in the concentrate line and then backwashing in the opposite filtered direction. The microfiltration unit may also contain a circulation system for chemically enhanced washing. This system is used to supply the membrane flushing reagent and water to the concentrate part of the pipeline. With the help of a pump, the resulting washing fluid circulates inside the membrane, washing away hard-to-dissolve impurities in the process. The washing reagents are selected depending on the type of contaminants deposited on the membrane surface. These contaminants may be of organic or non-organic origin. In general, the stages of the membrane washing process and their duration can be individually adapted to each type of filtered liquid.
The task of microfiltration water treatment can be divided into two types: obtaining a high-quality filtrate or obtaining a liquid concentrate. It depends on whether the objective of the microfiltration treatment is to get a filtrate or a concentrate.
If you have this request, please do not hesitate to contact us. Our specialists will help you. Our company provides laboratory and pilot testing services to obtain microfiltration results directly on your product.