La lecture en ligne est gratuite
Le téléchargement nécessite un accès à la bibliothèque YouScribe
Tout savoir sur nos offres
Télécharger Lire

Definition of a continuous neutral electrolytic pickling process (DEN) entirely devoid of noxious industrial releases

De
128 pages
Commission of the European Communities technical steel research Properties and service performance Definition of a continuous neutral electrolytic pickling (den) process entirely devoid of noxious industrial releases Commission of the European Communities technical steel research Properties and service performance Definition of a continuous neutral electrolytic pickling (den) process entirely devoid of noxious industrial releases N. Azzerri, R. Bruno Centro Sperimentale Metallurgico S.p.A. Via di Castel Romano 1-00129 ROMA Contract No 7210.EA/403, 7254.25.4/282 (1.6.1976-31.5.1980) FINAL REPORT Directorate-General Science, Research and Development 1983 EUR 7436 EN Published by the COMMISSION OF THE EUROPEAN COMMUNITIES Directorate-General Information Market and Innovation Bâtiment Jean Monnet LUXEMBOURG LEGAL NOTICE Neither the Commission of the European Communities nor any person acting on behalf of then is responsible for the use which might be made of the following Information IECSC-EEC-EAEC, Brussels · Luxembourg centro «perimenti*» metalúrgico apta. DEFINITION OF A CONTINUOUS NEUTRAL ELECTROLYTIC PICKLING (DEN) PROCESS ENTIRELY DEVOID OF NOXIOUS INDUSTRIAL RELEASES FINAL REPORT Authors : Nazzareno Azzerri Roberto Bruno Beneficiary of Convention: Centro Sperimentale Metal lurgico SpA, Via di Castel Romano, ROME (Italy) 7210.EA/4/403-7254.25/4/282 Convention No.
Voir plus Voir moins

Vous aimerez aussi

Commission of the European Communities
technical steel research
Properties and service performance
Definition of a continuous neutral
electrolytic pickling (den) process
entirely devoid of noxious
industrial releases Commission of the European Communities
technical steel research
Properties and service performance
Definition of a continuous neutral
electrolytic pickling (den) process
entirely devoid of noxious
industrial releases
N. Azzerri, R. Bruno
Centro Sperimentale Metallurgico S.p.A.
Via di Castel Romano
1-00129 ROMA
Contract No 7210.EA/403, 7254.25.4/282
(1.6.1976-31.5.1980)
FINAL REPORT
Directorate-General
Science, Research and Development
1983 EUR 7436 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Information Market and Innovation
Bâtiment Jean Monnet
LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following Information
IECSC-EEC-EAEC, Brussels · Luxembourg centro
«perimenti*»
metalúrgico apta.
DEFINITION OF A CONTINUOUS NEUTRAL ELECTROLYTIC
PICKLING (DEN) PROCESS ENTIRELY DEVOID OF NOXIOUS
INDUSTRIAL RELEASES
FINAL REPORT
Authors : Nazzareno Azzerri
Roberto Bruno
Beneficiary of Convention: Centro Sperimentale Metal
lurgico SpA, Via di Castel
Romano, ROME (Italy)
7210.EA/4/403-7254.25/4/282 Convention No.:
Date of Commencement: 1 June 1976
31 May 1980 Date of Completion: CONTENTS
Page
SUMMARY I
SOMMARIO 'V
SOMMAIRE Χ
ZUSAMMENFASSUNG XVI
1. INTRODUCTION 1
2. PRELIMINARY TECHNICAL-ECONOMIC FEASIBILITY
STUDY 3
3. DEFINITION OF PROCESS 4
3.1 Definition of Electrochemical System 4
3.2 Study of Electrolytic Conductivity 5
3.3y of Fundamental Electrode Reactions 6
3.4 Influence of Scale-Cracking Treatment
and of Operative Conditions on Cyclic
Impulse Polarization 12
3.5 Anodic Behaviour of Silicon Steel 20
4. TREATMENT OF DEN SLUDGE 25
5. PILOT PLANT EXPERIMENTAL TESTS9
6. DEFINITION AND ANALYSIS OF DEN QUALITATIVE
AND ECOLOGICAL CHARACTERISTICS 3
7. CONCLUSIONS AND FUTURE PROSPECTS 41
LEGENDES DES TABLEAUX 46
TABELLENANWEISUNG7
DIDASCALIE TABELLE8
LEGENDES DES FIGURES9
ABBILDUNGSANWEISUNGEN 53
DIDSCALIE FIGURE
TABLES AND FIGURES 61 - I -
DEFINITION OF A CONTINUOUS NEUTRAL ELECTROLYTIC
PICKLING (DEN) PROCESS ENTIRELY DEVOID OF NOXIOUS
INDUSTRIAL RELEASES
S U M M A R Y
Since pickling (i.e. the removal of mill scale from
the surface of hot-rolled products) is normally performed
by means of acids, this operation constitutes one of the
steel manufacturing steps contributing most highly to
environmental pollution. Some costly technical solutions
have been devised recently for limiting ecological damage
connected with the use of acids and with the disposal of
spent pickling baths; but a more radical solution is re
quired if the pickling process is to be rendered ecologi^
cally harmless.
The Neutral Electrolytic Pickling (DEN) process is an
electrochemical treatment for descaling and surface finish
ing hot-rolled steel products which uses a neutral sodium
sulfate solution. The process is economically competitive
with conventional pickling methods (e.g. the use of sulphu
rie or hydrochloric acid) and has been developed by CSM
for treating carbon steels, low alloy steels and silicon
steel strip for magnetic materials.
The DEN process does not employ any acids, alkalis or
salts which cannot be discharged with safety into waste
water systems and therefore presents a viable solution of
those ecological problems that up to now have beset the
pickling operation.
In addition to ecological benefits, DEN offers a range
of technical and economic advantages which fully justify
the interest aroused in the iron and steel industry by this
new process. Among the most important advantages are the
reduction of routine and special maintenance costs, the
more efficient re-use of process residues and (above all)
the improved surface quality of the treated steel.
Firm evidence has in fact been obtained confirming -Il­
that DEN not only improves surface quality, but also per
mits quality control without difficulty. These results
are sufficient per se to demonstrate the importance of
the new process given (a) the difficulties associated
with traditional pickling methods in ensuring a consis
tently acceptable surface quality, and (b) the growing
demand for high-quality hot-rolled and cold-rolled prod
ucts for specific uses.
The research program for developing the DEN process
included studies at laboratory level as well as trial
runs on a pilot plant.
The laboratory studies were carried out on hot-rolled
carbon steel and silicon steel products. The basic elee
trochemical reactions of the DEN process were defined as
well as the principal operating parameters (temperature,
concentration and flow-dynamics of electrolyte, amplitude
and sequence of cathodic and anodic polarizations). The
influence of mill scale morphology and structure on the
DEN electrochemical reactions was determined and the ef
ficiency of the process evaluated. Methods were defined
for regenerating the electrolyte and for re-using the pro
cess residues (ferric oxide production).
The object of the subsequent pilot plant trials was
to determine the best operating conditions over the range
of interest for industrial application of the process.
The most important achievements in this connection can be
summarized as follows.
Both temperature and concentration of the neutral
sodium sulfate solution influence electrolyte conductivi
ty; their values, therefore, should be as high as is com
patible with correct industrial practice. In effect, it
was found that the Na2SO^ concentration should range be
tween 200 and 250 g/1 and that the optimum operating tern
perature should be around 90°C. The optimum current
density range is between 2 and 5 kA/m2; the value of
^4 kA/m2 can be considered typical.
The pulse sequence of the cathodic and anodic polari
zations applied to the steel strip undergoing DEN treat
ment should include at least three cycles; assuming a

Un pour Un
Permettre à tous d'accéder à la lecture
Pour chaque accès à la bibliothèque, YouScribe donne un accès à une personne dans le besoin