Selection of PAM

According to ionic characteristics, polyacrylamide can be divided into four types: non-ionic, anionic, cationic and amphoteric polyacrylamide. According to the molecular weight, there are different specifications of molecular weight, ion degree, etc., and many models are derived. Faced with the market's messy specification system, it is really difficult to select the best polyacrylamide model for your own sewage system. How to deal with sewage or pollution? Common problems in the selection of mud polyacrylamide.

 1. Understand the source of sludge

Sludge is an inevitable product in sewage treatment. First of all, we should understand the source, nature, composition and solid content of sludge. According to the different main components contained in sludge, sludge can be divided into organic sludge and inorganic sludge.

Generally speaking, cationic polyacrylamide is used to treat organic sludge, and anionic polyacrylamide is used to treat inorganic sludge. It is not easy to use cationic polyacrylamide when the alkalinity is strong, and it is not suitable to use anionic polyacrylamide when the acidity is strong. When the solid content of the mud is high, the amount of polyacrylamide is usually larger.

2. The ion degree selection of polyacrylamide

For the sludge to be dewatered, flocculants of different ionicity can be screened through small experiments to select the best and suitable polyacrylamide, so that the best flocculant effect can be obtained, and the dosage of chemicals can be minimized, saving costs . The key point of ion selection:

(1) The size of the flocculation 

The size of the flocculation: too small a flocculation will affect the speed of drainage, too large a flocculation will cause the flocculation to bind more water and reduce the degree of mud biscuit. The size of the flocs can be adjusted by selecting the molecular weight of polyacrylamide.

(2) Floc strength (moisture content) 

The strength of the floc: The floc should remain stable and not broken under shearing. Increasing the molecular weight of polyacrylamide or choosing a suitable molecular structure can help improve the stability of the flocculation.

(3) The mixing of polyacrylamide and sludge 

Polyacrylamide must fully react with the sludge at a certain position of the dewatering equipment to cause flocculation. For this reason, the viscosity of the polyacrylamide solution must be appropriate, and it can be fully mixed with the sludge under the existing equipment conditions. Whether the two are uniformly mixed is a key factor for success. The viscosity of polyacrylamide solution is related to its molecular weight and preparation concentration.

(4) Dissolution of polyacrylamide

The flocculation function can be fully exerted only when it is dissolved well. As mentioned earlier, the dissolution process of polyacrylamide is actually the maturation process of polyacrylamide. Sometimes it is necessary to speed up the dissolution rate. At this time, consider increasing the concentration of the polyacrylamide solution.

Therefore, the best product selection must be determined by laboratory beaker experiments.

3. Selection of the molecular weight of polyacrylamide

The molecular weight of polyacrylamide refers to the length of the molecular chain in the molecule. The molecular weight of polyacrylamide is between 5 and 18 million. Generally speaking, the higher the molecular weight of polyacrylamide products, the viscosity is also However, when using, it is not a product with a higher molecular weight. The better the effect will be. In use, the appropriate polyacrylamide should be determined according to the actual application industry, water quality, treatment equipment and other conditions. Molecular weight.

Polyacrylamide is a high molecular weight coagulant. The products can be divided into low molecular weight (<1 million), medium molecular weight (2-4 million) and high molecular weight (>7 million) according to their average molecular weight.

Polyacrylamide is used in sewage treatment, a high molecular water-soluble organic polymer with a molecular weight of several million to several tens of millions. Domestic polymer polyacrylamides include: non-ionic polyacrylamide (abbreviated as NPAM, molecular weight 8-15 million), anionic polyacrylamide (abbreviated as APAM, molecular weight 8-20 million), cationic polyacrylamide (abbreviated as CPAM, molecular weight 800 -12 million, ion degree 10%-80%).

When used as a coagulant only, generally the higher the molecular weight, the tighter the flocs, the more economical the use of drugs, but the molecular weight of anionic polyacrylamide is recommended not to exceed 20 million.

If in terms of sludge dewatering. When using a belt filter press, the molecular weight should not be too high. If the molecular weight is too high, it may cause clogging of the filter cloth and affect the dehydration effect; for example, if you use a centrifugal filter press, the molecular weight requirement is higher because the centrifugal pressure The filter requires that the flocs can withstand shear as much as possible, so choose products with relatively high molecular weight. 

It can be seen from the above that the choice of molecular weight and ionicity is not absolute. It is best to do a selection test before selecting polyacrylamide, and it is best to run a computer operation test, so that the data obtained is the most accurate, and the preferred cost performance of polyacrylamide is higher.