Function of scale inhibitor: delay, reduce or prevent scaling

most of the commonly used scale inhibitors are used to prevent the growth of scale crystals, that is, the scale inhibitors need to work when the fine crystals of scale in water are just formed from water

inorganic phosphate

trisodium phosphate (Na3PO4), tetrasodium pyrophosphate (Na4P2O7), sodium hexametaphosphate ((NaPO3) 6), sodium tripolyphosphate (na5p3o10)

features: the price of the agent is appropriate, and the effect of preventing CaCO3 scale is excellent. It is easy to hydrolyze to produce orthophosphate and react with calcium ions to produce insoluble calcium phosphate; With the increase of water temperature, the hydrolysis rate was accelerated. The high service temperature is 80 ℃

organic phosphoric acid and its salts

amino trimethylidene phosphonic acid (ATMP), ethylenediamine tetramethylidene phosphonic acid (EDTMP), sodium hydroxyethylidene diphosphate (HEDP)

features: it is not easy to hydrolyze, and the dosage is low. It has good anti scaling effect. It has good compatibility with other sewage treatment agents. The use temperature is up to 100 ℃

polymer

polyacrylic acid (PAA), polyacrylamide (PMA), polymaleic anhydride (HPMA), etc. HPMA has good effect on preventing CaSO4 and BaSO4 scale

complex complex

several single agents with different effects are mixed in a certain proportion. As long as they do not react with each other, have no counteracting effect, and play their own characteristics, they can be compounded into a complex

selection and evaluation of scale inhibitors

evaluation of scale inhibitors

the relative effect is measured by laboratory tests and expressed by the scale inhibition rate P

selection of scale inhibitor

the following factors should be considered in the selection of scale inhibitor:

chemical composition of scale: analyze the main components of scale sample, find out the main ions forming scale, select scale inhibitor targeted, and achieve good scale inhibition effect

scale severity: the effect of scale inhibitor is affected by saturation. When there is a small amount of scale, the scale inhibitor has good effect. When the scale forming speed is high, the scale inhibitor and its dosage shall be selected according to the severity of the structure

compatibility with other sewage treatment agents: whether the scale inhibitor reacts with other agents in the system (such as actual main agent, corrosion inhibitor, deoxidizer, etc.) to offset their respective effects

temperature: with the increase of temperature, the effect of scale inhibitor decreases. Each scale inhibitor has an upper limit temperature

if the scale inhibitor with excellent effect has been selected, two criteria need to be protected:

(a) when the scale crystal in the water is just formed, the added scale inhibitor needs to be able to prevent the further growth of the scale crystal with the best effect - the scale inhibitor needs to be added to the upstream of the problem location

(b) the scale inhibitor needs to be continuously added to the water, so as to prevent the growth of scale crystals precipitated from the water

note: whether it is continuous injection of anti scaling agent or "batch treatment", the system shall be protected