Preparation Of Scale Inhibitors Adapting To High Hardness, High Alkalinity And High PH

In the open industrial circulatory water cooling system, various kinds of salt will accumulate in cooling water as water evaporating. And thus, some problems appeare in the system after long run, such as scale-forming, corrosion and microorganism over-reproduction. With the development of water alkaline treatment technology and the increase of concentration times, the quality of circulating water tend to become high hardness, high alkalinity, high pH value and even high temperature, which deepened the difficulty in controlling these problems. In this research, two types of new copolymers were successfully prepared by changing polymerization conditions, such as the ratio of monomers, the ratio and dosage of initiators, reaction temperature and reaction time. One of the copolymers was derived from maleic anhydride (MA) and 2-acrylamido-2-methylpropane sulphonic acid (AMPS), and the other from MA ,AMPS and 2-acrylamido-2-methylpropane phosphonic acid (AMPP). The polymerization was initiated by hypophosphite sodium and peroxide in an aqueous solution. The copolymers possessed three functional groups of carboxyl, sulphonate and phosphine, so the copolyers were good scale inhibitor and dispersion agent. The polymerization rate of MA/AMPS depolymer was up to 80%, and MA/AMPS/AMPP terpolymer's was up to 90%.Using static scale inhibiting tests, the effects of some factors, such as copolymer concentration, hardness, alkalinity, temperature and pH value of the experimental water, on copolymer's scale inhibiting ability were investigated. The results showed that: (1) under the following conditions: 375mg/L of Ca2+, HCO3- (both measured in the form of CaCO3 after concentrating 1.5 times, the same as the following), temp.=80℃, without adjusting pH value, MA/AMPS/AMPP terpolymer's CaCO3 scale-inhibiting rate was 100%, better than some good scale inhibitors bought in the market (e.g. XF-210 etc), and MA/AMPS depolymer's CaCO3 scale inhibiting rate was 93.26%, almost at the same level of those scale inhibitors mentioned above; (2) under the following conditions: 780mg/L of Ca2+, HCO3-, temp.=65℃, pH=8.5, MA/AMPS/AMPP terpolymer's CaCO3 scale inhibiting rate was still up to 80%; (3) under the following conditions: 860mg/L of Ca2+, 800mg/L of HCO3-, temp.=65℃, pH=8.5, MA/AMPS depolymer's CaCO3 scale inhibiting rate was 66.20%; if it was used together with JC-333 (ATMP), CaCO3 scale inhibiting rate would increase above 80%.Using dynamic model test, MA/AMPS/AMPP terpolymer's synthetical performance was investigated under the following conditions: 550 mg/L of Ca2+ and 400 mg/L of HCO3- of the replenish water, cooling water temp.in=30℃, temp.out=38℃, heat water temp.= 95℃, pH = 8.5, concentration times=2, after circulating 15 days, the average corrosion velocity was 11.5mdd, adhesion velocity was 12.3mcm and the limit thermal resistance of filth was 1.35×10-4m2·h·K/Kcal. The results reached the "good" level of Chinese Petrochemical Industrial Evaluation Standard.In this paper, copolymer's performance in inhibiting Ca3(PO4)2 scale and zinc salts precipitation and dispersing ferric oxide were also investigated. The results showed that: (1) MA/AMPS depolymer's Ca3(PO4)2 scale-inhibiting rate was 100% (9mg/L of depolymer's dosage) and MA/AMPS/AMPP terpolymer's Ca3(PO4)2 scale-inhibiting rate was 95.92% (18mg/L of terpolymer's dosage) under the following conditions: 5mg/L of PO43- , 250mg/L of Ca2+, pH=9.0; (2) MA/AMPS/AMPP terpolymer's inhibiting rate of zinc salts precipitation was close to 70% (28mg/L of terpolymer's dosage ) under the following conditions: 5mg/L of Zn2+, 250mg/L of Ca2+,HCO3- ,temp.=80℃; (3) Copolymers were good dispersion agents for ferric oxide. The ray penetration percent of Fe2+ solution after treatment was 44.4%.