CN104694937A

CN104694937A - Heat exchanger electrochemically-induced film formation method in circulating cooling water micro-alkalifying transition period

Info

Publication number: CN104694937A
Application number: CN201510099788.0A
Authority: CN
Inventors: 曾惠明; 吕亮; 程慎玉; 沈晓莉; 范蕊
Original assignee: Quzhou University
Current assignee: ZHEJIANG CHANGSHAN LISHENG NEW MATERIAL CO.,LTD.
Priority date: 2015-03-08
Filing date: 2015-03-08
Publication date: 2015-06-10
Anticipated expiration: 2035-03-08
Also published as: CN104694937B

Abstract

The invention relates to a heat exchanger electrochemically-induced film formation method in a circulating cooling water micro-alkalifying transition period. The method comprises the following steps: connecting a circulating cooling water system heat exchanger with an active metal zinc block to constitute a primary cell, regulating the pH value of circulating water to 2-4, monitoring the metal ion content of the circulating water in the operation process, and after 2-3 days, finishing cleaning when the rise trend slows down; as for a brass heat exchanger, regulating the system to alkality, adding an oxidizer, and forming a Cu2O passivating film on the surface after some time, wherein after the cathode protection is removed, the Cu2O passivating film is gradually converted into a stable CuO passivating film, and afterwards, the brass corrosion rate is less than 0.005 mm/a; and as for the a carbon steel heat exchanger, adding Fe<2+> at one time, circulating for some time, regulating the solution to alkality, adding an oxidizer, removing cathode protection after some time, and forming a compact ferric oxide passivating film on the surface, wherein the corrosion rate is less than 0.01mm/a. The method prevents local corrosion and completes the circulating cooling water micro-alkalifying transition period.

Description

A kind of recirculated cooling water micro-alkalization transitional period interchanger electrochemical induce film

Technical field

The present invention relates to the modified transitory stage of the micro-alkalization of recirculated cooling water, the matting of heat exchanger metal and process for corrosion control, especially utilize galvanic protection and oxygenant passivation to combine, make brass and steel surface produce the method for uniform passivation film.

Background technology

Existingly relating to recirculating cooling water system interchanger matting and pre-membrane technique, is use corrosion inhibiting and descaling agent to realize both having removed metallic surface dirt, and when reducing again cleaning, acidic medium is to the dual purpose of the erosion of metallic matrix.This technology is divided into two classes, and a class is off-line cleaning, and a class is on-line cleaning.Both principles are identical, namely add the weak acid of rare strong acid or tool complexing, and add corrosion inhibiting and descaling agent, medicament is at system internal recycle certain hour, one deck organic membrane is adhered in new surface after cleaning namely, only need supplement medicament, carry out suitable repairing to organic membrane in operational process afterwards.But both drug concentrations and cycling time are distinguished to some extent, off-line cleaning is carried out between down period, and medicament is denseer, and the treatment time is shorter, within 1 ~ 2 day, can complete, and after having cleaned, scavenging solution needs to upgrade.On-line cleaning then adding consistency is lower, and the treatment time continues about 15 ~ 20 days, after having cleaned, and scavenging solution progressively discharges with dense water.The process of this purging method follow-up use method for dosing medicine is comparatively appropriate.

The micro-alkalization process of recirculated cooling water is then cycle for the treatment of cooling water replenishment, remove the scale-forming ion such as calcium, magnesium ion wherein, remove the nutritive element such as nitrogen, phosphorus, and the chlorion and sulfate ion that promote corrosion are converted into carbanion or the bicarbonate ion of alkalescence, by modified for recirculated cooling water to slight alkalinity scope (pH=8.0 ~ 9.0), under the condition of recirculated water not dosing separately, realize the microorganisms such as antiscale, protection against corrosion and anti-algae and multiply, realize zero release simultaneously.After traditional matting and pre-membrane process process, what formed in metallic surface is organic membrane, and when micro-alkalization is modified, the film on surface will constantly come off, and new film is difficult to be formed, and incomplete film will cause forming microelectrode, acceleration local corrosion.Therefore, the operation of the pre-inapplicable micro-alkalization process of membrane process of tradition, needs to develop a kind of cleaning prefilming method newly.

Recirculated cooling water micro-alkalization operating requirement interchanger metallic surface forms the passive film of one deck densification, and its main component is the oxide compound of metal itself, and matting and oxide compound film forming conflicting.For solving the problem, when the present invention utilizes cathode protecting process to alleviate matting, the erosion of the pickling medium that metallic matrix is subject to, after cleaning, metallic surface keeps clean.For the brass interchanger of comparatively inertia, after cleaning, medium is adjusted to alkalescence, and add oxygenant, first by the progressively passivation of sacrificial anode surface, again the cupric ion of slow releasing is deposited on its surface, forms dense oxidation film, remove sacrificial anode, realize the pre-film of inorganic oxide of brass surfaces, complete micro-alkalization process transition.For comparatively active simple steel heat exchanger, because its surface ion is active, more easily there is local corrosion, thus form galvanic cell.Therefore, under the prerequisite using zinc anode protection, Fe is added ²⁺ion, first forms the irony film of one deck external source, more slowly closes anode and negative electrode, realize surface compact film forming, complete micro-alkalization transition on its surface.In this way carry out matting and pre-film, realize the method for micro-alkalization process smooth transition, have not yet to see report.

Summary of the invention

The object of the invention is: provide a kind of system heat exchanger electrochemical induce realizing the modified smooth transition of the micro-alkalization of recirculated cooling water balanced film, especially for metallic recuperator surface cleaning and the balanced film forming of brass and carbon steel material.

The object of the present invention is achieved like this:

1, the matting of interchanger under galvanic protection condition.Select the metal more more active than interchanger metal, the metal that namely redox potential is lower, as sacrificial anode, puts into recirculated cooling water after utilizing wire it to be connected with interchanger metal.Add the strong acid such as a certain amount of hydrochloric acid or sulfuric acid again, or there is the citric acid of complexation property, by system water pH regulator to 2 ~ 4, the ion that in working cycle, close monitoring heat exchanger metal discharges, when ionic concn rises to vertex, cleaning terminates;

2, the electro-adsorption of heat exchanger surface reduces pre-film.For comparatively active carbon steel matter interchanger, because its surface easily forms local corrosion district, after adding oxygenant, occur to accelerate galvanic corrosion, need in acid condition, add Fe2+ ion and carry out pre-film, in maintenance system, Fe2+ concentration is 1mmol/L ~ 10mmol/L.Under galvanic protection Galvanic interaction, Fe2+ is adsorbed on heat exchanger surface, and is converted into atoms metal, completes pre-film.For the brass wire of comparatively inertia, then need not pre-film separately;

3, pre-film transforms by oxidizing reaction.Add basifier, after system water quality balance, pH=8 ~ 9, then add oxygenant, after running for some time, sacrificial anode oxide is closed, and negative electrode slowly loses protection, and the iron ion of release will be converted into oxide compound, and uniform fold, on its surface, forms passive film;

4, remove galvanic protection, realize a smooth transition.After removing galvanic protection, interchanger metallic surface passivating film, by under the acting in conjunction of OH-and dissolved oxygen, slowly upgrades, and realizes the tight protection to matrix.

Feature of the present invention is:

1, use cathode protecting process to replace traditional corrosion inhibiting and descaling agent, in Process of Chemical Cleaning, ensure the dirt can removing heat exchanger surface, reduce thermal resistance, improve heat transfer efficiency, can metallic matrix be protected again, prevent perforation, matting rear surface cleanliness without any pollution;

2, the galvanic cell of galvanic protection is utilized, in acid condition, at the uniform metallic membrane of active metal plated surface last layer, prevent because surface exists erosion point or dirt, form galvanic cell, during passivation, local accelerated corrosion occurs, for follow-up oxygenant passivation creates favorable conditions;

3, the passivator after pre-film can select hydrogen peroxide etc., and it is a kind of chemical agent of clean environment firendly, generates water after oxidizing reaction, and therefore, passivating solution does not need discharge, great lot of water resources can not be caused to waste and environmental pollution, be more conducive to realizing on-line cleaning and transition;

4, the method achieve the improvement to traditional method, decrease the application of corrosion inhibiting and descaling agent, be conducive to advancing the micro-alkalization process of the recirculated cooling water of energy-conserving and environment-protective more applying industrially simultaneously, larger Social benefit and economic benefit will be produced. embodiment

Below in conjunction with specific embodiment, the present invention is described in further detail, but protection scope of the present invention is not limited in this.

embodiment 1

For the old system between the new construction system of brass material interchanger or overhaul time, take off-line chemical cleaning method.Select 500mm × 500mm × 10mm zine plate or aluminium sheet to immerse in recirculated cooling water as sacrificial anode, use 12mm ²anode is connected with interchanger two ends by blister copper wire, forms galvanic cell.Re-use hydrochloric acid, sulfuric acid or select one and Proportion of Citric Acid to be that recirculated water is adjusted to acidity, pH=2 ~ 4 by the solution of 1:1, circular flow 24h, in cleaning process, 2h once measures Cu ²⁺content, and detect pH, if pH rises to some extent, then supplement acid solution in time.Draw concentration changes with time curve, curve rises to vertex, stops pickling.

Add NaOH, Na ₂cO ₃, NaHCO ₃wherein one or more combination is made into carbonate buffer solution, by recirculated water pH regulator to 8 ~ 9, then adds hydrogen peroxide, makes H in recirculated water ₂o ₂concentration is 0.2% ~ 0.8%(v/v), after running 2 ~ 5h, brass surfaces forms the red Cu of light ₂o passive film.

Remove zine plate or aluminium sheet, brass surfaces oxide film gradates the CuO film into black under Effect of Dissolved Oxygen, and under stable slight alkalinity condition of water quality, film teaching display stand upgrades and running balance, and protection matrix metal, reduces erosion rate.

embodiment 2

For the old system between the new construction system of carbon steel material interchanger or overhaul time, take to adopt method in example 1 to carry out off-line matting.

After cleaning, add FeSO ₄, Fe (NO ₃) ₂or FeCl ₂in a kind of ferrous salt, make Fe in recirculated water ²⁺ion content is 1mmol/L ~ 10mmol/L, Fe ²⁺ion to movable cathode, is adsorbed on heat exchanger surface under galvanic cell electric field action, and is reduced into iron atom, forms the pre-film of material identical with matrix, and effects on surface dirt or erosion point effectively cover, and under can preventing alkaline oxygenated environment, local accelerated corrosion occur.

Recycle the step identical with example 1 to carry out alkalizing and passivation, final carbon steel is crossed water surface and is formed fine and close ferric oxide film, and in stable alkaline buffer solution, teaching display stand upgrades and mending-leakage, the erosion rate of carbon steel is controlled in standard range.

embodiment 3

For the old system that need run without interruption, take in-site chemical cleaning method.Adopt the galvanic protection scheme in example 1, strong acid and the dosing of citric acid 1:1 proportioning, be adjusted to 3 ~ 4 by system pH, and monitor metal ion and pH in recirculated water every day, adds cleaning acid in good time, run about 15 days, complete in-site chemical cleaning.

For copper heat exchanger, then directly adopt example 1 method alkalization oxidation, obtain the pre-film of oxide compound, complete micro-alkalization transition.For carbon steel matter interchanger, then adopt example 2 first to carry out the pre-film of ferrous absorbing and reducing, then adopt in example 1 method for oxidation that alkalizes to obtain the pre-film of oxide compound, complete transition.

Claims

1. recirculated cooling water micro-alkalization transitional period interchanger electrochemical induce film: first, uses metallic zinc as sacrificial anode, forms galvanic cell with interchanger metal, and in cycle chemistry cleaning process, protection interchanger matrix exempts from acidic medium corrosion; After the cleaning of brass heat exchanger system, water quality is adjusted to alkalescence, adds oxygenant, make its surface form Cu ₂o protective layer, after removing galvanic protection, oxide skin gradates as stable CuO protective layer, completes micro-alkalization transition; After simple steel heat exchanger cleaning systems, FeSO need be added ₄ion, under the effect of galvanic cell, Fe ²⁺ionic adsorption in matrix surface, and is reduced, and plating last layer film, cover uneven spot corrosion district, then water quality is adjusted to alkalescence, add oxygenant, slow oxidation forms fine and close ferric oxide protective membrane, completes micro-alkalization transition.

2., in claim 1, after simple steel heat exchanger cleaning, add FeSO ₄time, it is characterized in that:

a,pH maintains between 2 ~ 4, HCl or H selected by conditioning agent ₂sO ₄;

b,fe ²⁺ion is provided by following one or more combination, comprises FeSO ₄, FeCl ₃with Fe (NO ₃) ₂deng;

c,fe ²⁺after ion adds system, the content in system is between the mmol/L of 1mmol/L ~ 10;

d,fe ²⁺the ion film plating reaction times is between 10h ~ 48h.

3., in claim 1, during recirculating cooling water system alkalization, it is characterized in that:

a,pH is that between 8 ~ 10, basicity maintains 10mmol/L ~ 38mmol/L;

b,basifier is the combination of one or more medicaments following, as NaOH, Na ₂cO ₃, NaHCO ₃, Ca (OH) ₂deng.

4., in claim 1, when recirculating cooling water system adds oxygenant, it is characterized in that:

a,oxygenant is following one or more combination, as hydrogen peroxide, Sodium Nitrite, potassium permanganate or potassium bichromate;

b,oxidant concentration is 10mmol/L ~ 200mmol/L;

c,oxygenant in systems in which cycling time be 2 ~ 12h.