EDUCTOR AGITATION FOR HEAVY NICKEL DEPOSITION:

A CASE STUDY.

DAVID GABELOUGHBOROUGH UNIVERSITY

and

CLIVE PORTERFormerly DOWDING and MILLS LTD.

A sponsored research project for the MSc course in Surface

Engineering.

Nottingham – Loughborough – Hull - Sheffield Hallam

Universities

MANAGEMENT OBJECTIVES

• Focus on refurbished marine engine components

• To improve the process throughput and production rates

• To improve the product quality

PURPOSE OF PROJECT

• To obtain data to justify the installation of eductor agitation

• To improve plant instrumentation and to monitor the enhanced process

• To establish criteria to measure the degree of process enhancement

PRESENTATION CONTENTS

• Design of an Eductor system• Some performance parameters• Bonuses

DESIGN OF EDUCTOR SYSTEM

• Tank and pump sizing• Eductor numbers and placement• System costing• Commissioning• Benchmarking• Optimization• Monitoring

INSTALLATION

• 6000l tank having air agitation• Total agitation flow of 4000l/min• Pumped vol. of 800l/min• Pump size; 2.2kW three-phase• 20 x 3/8in eductors, 5 each side• Eductors mounted in swivel tubes• System costing (2002): £2509

TANK PREPARATION

• Both air and eductor agitation were retained for comparisons

• Thorough cleaning vital! Any residual sludge is highly abrasive.

• Additional ammeters needed for independent current monitoring

BENCHMARKING

• Air agitation alone • Eductors alone• Eductors at several swivel angles• Use of test panels jigged at various

positions in the tank• Test panels thoroughly thickness

tested over whole surface

PATTERN OF AGITATION

• Agitation observed using air bubble entrainment

• The installation was modelled before use using clean water and good lighting

• Each bank of eductors was adjustable for angle of jetting

DEPOSITION RATES(Watts nickel)

• Air agitation 3.709g/hr• Eductor agitation (30º) 4.527*• Optimized eductors 5.054*

* Increases of 22% and 36.3% respectively

THICKNESS VARIANCE

Agitation Time for 0.2mm Corner excess, type mm.

Air 22 hr 0.8Eductors 8 hr 48 min 0.24*Optimized eductors 6 hr 17 min 0.0575*

*Waste improvements of 70% and 92% respectively

THICKNESS DISTRIBUTIONS

Criterion Air Eductors Optimized

Wt. gain(g): eductor20.4 24.9 27.8

Thickness(mm):Corners 0.25 0.275 0.225Centre 0.05 0.125 0.175Variance 0.2 0.15 0.075

EDUCTOR ADVANTAGES(Gabe, Ward* and Porter** using Cu* and Ni**)

• Agitation Enhancement over air: 7-10x

• Deposition rate improvement: 36%• Shorter process times: 71%• Reduced thickness variability: 92%

EDUCTOR BONUSES

• Zero fume emission• Reduced power usage in tank (ie. no

insulative air bubbles) worth 1-2V or ~25% per tank

• Reduction in sludge production (ie no oxidising air) and condensate

• Reduced additive consumption• Saving of heating energy with no fume

losses: 10-20%

AIRBORNE EMISSIONS*

• AIR 0.5-1.0mg nickel per m3 air volume

• EDUCTORS 0

• *Draeger tube emission measurements

EDUCTORS AND PROCESS FUME

• Process fume is substantially created by the gas phase and its release at the surface

• Affected by surfactants and mist suppressants• The fume consists of a solvent/solute mist• Use of Eductors eliminates 95% of the mist• Only public domain data is for nickel

electroplating (see Porter and Gabe, Plating & SF 2005). • Ni content of Eductor fume was practically

zero.• Fume carries heat; heat losses can be reduced

PROCESS SLUDGE

• Process sludge is produced by oxidation of dissolved metal and organic additives, and precipitation.

• Agitative air is the oxidation medium and eductors eliminate this source of sludge.

• Anodic oxidation of additives is primarily an anode material problem. Choice of anode can be an issue.

CONCLUSIONS

• Increased rates of production and improved film thickness distribution

• Saving of power usage to offset increased pumping costs

• A reduction in oxidation and sludge formation; reduced fume and heat losses

• Technology also useful for cleaning, pickling, etching, rinsing etc.