In the agricultural and sideline products, wine, vinegar and soy sauce are fermented from starch,of grain. The filtration of these products is an important production process, and the quality of the filtration directly affects the quality of the products. Traditional filtration methods include natural sedimentation, active adsorption, diatomite filtration, plate and frame filtration, etc. These filtration methods have some problems in different degrees of time, operation, environmental protection and other aspects, so it is necessary to choose a more advanced filtration method.
Hollow fiber can intercept large molecular substances and impurities between 0.002 ~ 0.1μm, and allow small molecular substances and dissolved solids (inorganic salts) to pass through, so that the filtered liquid can keep its original color, aroma, and taste, and achieve the purpose of heat-free sterilization. Therefore, using hollow fiber filter to filter wine, vinegar, soy sauce is a more advanced filtering method.
Polyethersulfone (PES) was selected as the membrane material, and the hollow fiber ultrafiltration membrane made of this material has high chemical property, resistant to chlorinated hydrocarbons, ketones, acids and other organic solvents, and stable to acids, bases, aliphatic hydrocarbons, oils, alcohols and so on. Good thermal stability, good resistance to steam and superhot water (150 ~ 160℃), fast flow rate, high mechanical strength. The filter membrane is easy to clean with internal pressure hollow fiber membrane, and the membrane shell, pipe and valve are made of 304 stainless steel, which is sanitary and easy to clean.
For wine, vinegar, soy sauce is a variety of amino acids, organic acids, sugars, vitamins, organic material such as alcohol and ester and water mixture, and adopts the cross-flow filtration method, through the pump will be required to filter the liquid pipelines into the filtration membrane, the membrane filtered liquid for the finished product, not through the liquid to the concentrate pipe to return to the same place
Due to the discharge of concentrated liquid, a large shear force can be formed on the surface of the membrane, thus effectively reducing the membrane pollution. The ratio of the flow rate of the concentrated liquid to the flow rate of the finished product can be adjusted according to the specific situation of the filtered liquid to reduce the contamination of the membrane, and the concentrated liquid can return to its original place and re-enter the ultrafiltration system for filtration
The cleaning system of hollow fiber is an important part of the filter, because the surface of the membrane will be covered by various impurities trapped, and even the membrane holes will be blocked by fine impurities, which will degrade the separation performance, so it is necessary to wash the membrane in time.
The cleaning principle is that the cleaning liquid (usually filtered clean water) is input reversely by the cleaning pump through the pipeline into the hollow fiber filtration membrane to wash away the impurities on the membrane wall, and the waste liquid is discharged through the waste discharge pipeline. The cleaning system of the filter can be cleaned in positive and negative ways.
Positive wash (such as pressure flushing) particular way is close the filtrate outlet valve, open the water outlet valve, pump will start production membrane body fluid input, this action make hollow fiber inside and outside pressure on both sides are equal, the pressure differential adhesion in loose dirt on the surface of the membrane, increase traffic again wash surface, soft film on the surface of a large number of impurities can be removed.
Backwash (reverse flushing), the specific approach is to close the filtrate outlet valve, fully open the waste liquid outlet valve, open the cleaning valve, start the cleaning pump, the cleaning liquid into the membrane body, remove impurities in the membrane wall hole. When backwashing, attention should be paid to the control of washing pressure, backwashing pressure should be less than 0.2mpa, otherwise it is easy to crack the film or destroy the bonding surface of hollow fiber and binder and form leakage.
Although regular positive and reverse cleaning can maintain the membrane filtration speed well, with the extension of the running time of the membrane module, the membrane pollution will become more and more severe, and the membrane filtration speed will also decrease. In order to recover the membrane filtration flux, the membrane module needs to be cleaned chemically. Chemical cleaning is usually done with acid first and then alkali. Generally, 2% citric acid is used in pickling, and 1% ~ 2% NaOH is used in alkali washing.