GB1110365A - Inhibition of scale in saline water evaporators - Google Patents

Abstract

A composition for inhibiting the deposition of scale from saline water comprises one part by wt. of a water-soluble amino compound of the formula <FORM:1110365/C3/1> "n" is a whole number from 1 to 3 and "m" is hydrogen, ammonium, alkali metal, zinc, magnesium, or calcium where M may be the same or different, in a group (OM)2, optionally 1-4 parts of tannin or sulphonated lignin, up to 0.4 parts of a polymer having a molecular weight of at least 50,000, said polymer being polyacrylic acid, polyacrylamide or partially hydrolysed polyacrylamide, up to about 1 part of a compatible anti-foam agent, e.g. a polyalkylene glycol or an ester or ether derivative thereof, and up to about one part of a hydrotropic agent, e.g. an aromatic sulphonate. The amino compound may be amino tri-(methylphosphonic acid) or its alkali metal salt, or ethylene diamine tetra-(methylphosphonic acid) or its alkali metal salt.ALSO:A method of inhibiting the deposition of scale from saline water on to the heat-exchange surfaces of a saline water evaporator comprises adding to said saline water an effective amount of a water-soluble amino compound of the formula <FORM:1110365/C1/1> "n" is a whole number from 1 to 3 and "M" is hydrogen, ammonium, alkali metal, zinc, magnesium, or calcium, where M may be the same or different in a group (OM)2. The water-soluble amino compound may be amino tri-(methylphosphonic acid) or its alkali metal salt or ethylene diamine tetra-(methylphosphonic acid) or its alkali metal salt. It may be added in a concentrate of from 1 to 25 p.p.m. in the form of a composition which also comprises 1-4 parts by wt. of tannin or sulphonated lignin, up to 0.4 parts of a polymer having a molecular weight of at least 50,000, said polymer being polyacrylic acid, polyacrylamide or partially hydrolysed polyacrylamide, up to about 1 part of a compatible antifoam agent and up to about one part by weight of a hydrotropic agent (parts are parts by weight per one part by weight of the amino acid).ALSO:Saline water is treated with a scale-inhibitor comprising a soluble organic compound of the type specified below, and the treated water is pumped through copper coils in a steam heat exchanger, and then submitted to flash evaporation. The residual saline water is then pumped through another set of copper coils in the same heat-exchanger, and again flashed. The class of organic compounds is that having the formula:- <FORM:1110365/B1-B2/1> where R is <FORM:1110365/B1-B2/2> or -(CH2)n <FORM:1110365/B1-B2/3> "n" is a whole number from 1 to 3, and "M" is hydrogen, ammonium, alkali metal, zinc, magnesium, or calcium. The distillation of sea water in a regenerative, single-stage flash evaporator, and in an eight-stage evaporator, is referred to.