How to correctly choose the right polyacrylamide

2021-10-20 11:21:14

Common mistake of choice

Myth　１:

Many users in the choice of polyacrylamide (PAM) that the greater the molecular weight of polyacrylamide, the higher the flocculation efficiency, the better the effect will be. So is the higher the molecular weight, the better?

Not necessarily. Polyacrylamide has more than 100 models, the nature of sewage produced by different enterprises is different, some are acidic water quality, some are alkaline water quality, some are neutral water quality, some contain oil, some contain a lot of organic matter, some contain color, some contain a lot of sediment, and a variety of situations. Not one type of polyacrylamide can solve all the problems, the sewage of all different water quality can be treated to standard. It is necessary to determine the best dosage through experimental trial selection, and then on the machine test, so as to achieve the best effect of less dosage and low cost.

Myth　:

Molecular weight and ionic degree are two important indicators of polyacrylamide (PAM), so polyacrylamide in the industry is mainly based on the level of ionic degree to select it?

Ionicity refers to the positive or negative of the chemical's ion charge, as well as its charge density. The higher the ionic degree, the smaller the molecular weight, and the higher the ionic degree, the higher the price of the product, the tightness of the product flocculation and water content are affected, in the selection process need further test to determine the required polyacrylamide model.

Myth 3:

Polyacrylamide (PAM) dissolve and stir for as long as possible?

Polyacrylamide appearance is white crystal particles, generally between 60-80 mesh, in use should be fully dissolved, generally dissolved stirring time should not be less than 30 minutes, winter temperature should be extended when the dissolution stirring time.

In many cases, PAM is not fully dissolved due to the short dissolution and stirring time, which cannot be effectively and quickly flocculated in sewage.

Myth 4:

Many users do not know the configuration concentration of polyacrylamide (PAM), think that the higher the concentration of flocculation is better, this is the correct operation?

Polyacrylamide configuration concentration is generally 0.1-0.3%, suitable for flocculation precipitation (according to PAM molecular weight size or according to the precipitation rate). Urban and industrial sludge dewatering configuration concentration is between 0.2%-0.5% (according to the size of sludge concentration to allocate the configuration concentration).

PAM configuration concentration depends entirely on the concentration of sewage sludge, sewage impurities in the polyacrylamide configuration concentration should be increased. Concentration is too large will also affect the use of the effect, so before using the machine must do a good test to determine the reasonable dose!

Myth 5:

Many users of polyacrylamide (PAM) ion characteristics of the resolution is very fuzzy, not according to the actual choice of polyacrylamide ion characteristics type?

Polyacrylamide models can be roughly divided into three: anionic, cationic, non-ionic. Anion is suitable for sewage flocculation, precipitation, precipitation, clarification, etc., can also be used for inorganic sludge dewatering. Cationic polyacrylamide is suitable for complex water flocculation, sedimentation, decolorization, clarification, municipal sludge dewatering, organic sludge dewatering, etc. Non-ionic polyacrylamide is suitable for soil water retention, weak acid sewage flocculation, sedimentation, dehydration, etc.

2. How to choose the right type of PAM?

Polyacrylamide (PAM) can be divided into four types of non-ionic, anionic, cationic and amphoteric polyacrylamide according to ionic characteristics. According to the molecular weight to have different specifications of molecular weight, ionicity and so on derived from a lot of models, in the face of the disorderly specification system of the market, for their own sewage system to optimize the best polyacrylamide model is really difficult, how to solve the common problems of sewage or sludge polyacrylamide selection.

1. Understand the source of sludge

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

Generally speaking, cationic polyacrylamide is used for the treatment of organic sludge, anionic polyacrylamide is used for the treatment of inorganic sludge, strong alkaline cationic polyacrylamide is not easy to use, and strong acid should not use anionic polyacrylamide, sludge solid content is usually high when the amount of polyacrylamide is larger.

2, polyacrylamide (PAM) ionic degree selection

In view of the sludge to be dehydrated, flocculants of different ionic degrees can be used to screen through small experiments to select the best suitable polyacrylamide, which can achieve the best flocculant effect, but also can make the least dosage, cost saving. The key to choose ion degree:

(1) The size of flocs

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

(2) Floc strength (water content)

Strength of flocs: Flocs should remain stable without breaking under shear action. Increasing the molecular weight of polyacrylamide or choosing the appropriate molecular structure can improve the stability of the floc.

(3) the mixture of polyacrylamide and sludge

Polyacrylamide in a certain location of dehydration equipment must be fully reacted with sludge, flocculation occurs. To this end, the viscosity of polyacrylamide solution must be appropriate, and it can be fully mixed with sludge under the conditions of existing equipment. Whether the two are evenly mixed is a key factor for success. Polyacrylamide solution viscosity and its molecular weight and preparation concentration.

(4) the dissolution of polyacrylamide

Only good dissolution can give full play to flocculation. The previous polyacrylamide dissolution process is actually the curing process of polyacrylamide, sometimes need to speed up the dissolution rate, then you can consider improving the concentration of polyacrylamide solution.

So the best choice of products to have beaker laboratory experiments to determine.

3, polyacrylamide (PAM) molecular weight selection

Polyacrylamide molecular weight refers to the length of molecular chain in the molecule, polyacrylamide molecular weight between 5-18 million, generally speaking, the higher the molecular weight of polyacrylamide products, the greater the viscosity, however, in use, not the higher the molecular weight of the product, the use effect is better, specific in use, According to the actual application of the industry, water quality, treatment equipment and other conditions, to determine the appropriate polyacrylamide molecular weight.

Polyacrylamide is a polymer coagulant aid, the product according to its average molecular weight can be divided into low molecular weight (<1 million), medium molecular weight (2 -4 million) and high molecular weight (>7 million) three categories.

Polyacrylamide used in sewage treatment, molecular weight from millions to tens of millions of polymer water-soluble organic polymer. Domestic polymer polyacrylamide: non-ionic polyacrylamide (ABBREVIATED NPAM, molecular weight 8-15 million), anionic polyacrylamide (abbreviated APAM, molecular weight 8-20 million), cationic polyacrylamide (abbreviated CPAM, molecular weight 8-12 million, ionic degree 10%-80%).

If the use of simple coagulant aid, the higher the general molecular weight, the closer the flocs, the more provincial the drug, but the molecular weight of anionic polyacrylamide is not more than 20 million.

If in sludge dewatering aspect. The use of belt filter press, the general molecular weight can not be too high, if the molecular weight is very high may lead to blockage of the filter cloth, affecting the dehydration effect; For example, if you use centrifugal filter press, the molecular weight requirements will be a little higher, because the centrifugal filter press requires that the flocs can be shear resistant as far as possible, so we should choose relatively high molecular weight products.

It can be seen from the above that the choice of molecular weight and ionicity is not absolute. It is best to do the selection test before choosing polyacrylamide, and it is best to run the test on the machine, so that the data is the most accurate and the preferred polyacrylamide is more cost-effective.