lable at ScienceDirect

Journal of Cleaner Production 18 (2010) 1092e1099

Contents lists avai

Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Toward cleaner production of hot dip galvanizing industry in China

Gang Kong a,b,*, Rob White b

a School of Material Science and Engineering, South China University of Technology, No.381, Wushan Road, Guangzhou 510640, Chinab International Zinc Association, 168 Avenue de Tervuren/Box4, B-1150 Brussels, Belgium

a r t i c l e i n f o

Article history:Received 12 December 2008Received in revised form6 March 2010Accepted 9 March 2010Available online 17 March 2010

Keywords:Hot dip galvanizing industryCleaner productionSustainabilityChina

* Corresponding author. School of Material ScienceUniversity of Technology, No.381, Wushan Road, Guþ86 20 85511540.

E-mail address: konggang@scut.edu.cn (G. Kong).

0959-6526/$ e see front matter � 2010 Elsevier Ltd.doi:10.1016/j.jclepro.2010.03.006

a b s t r a c t

China has now the largest annual outputs of galvanized steel and the most amount of galvanizing plantsin the world. However, with obsolete technology, the hot dip galvanizing industry has been proved asone of the industries, which consume large amounts of raw materials and energy, produce numerouspollutants and causes serious contamination in China. Cleaner Production in the hot dip galvanizingindustry is now the only way to achieve the sustainable development of hot dip galvanizing industry. Theimplementation of the Common Fund for Commodities (CFC) project: The Transfer of Technology andPromotion of demand: Batch hot dip galvanizing in China launched by International Zinc Association (IZA)is introduced in this paper, The Best Available Technologies of operation, energy and environmentalmanagement in the world are also introduced. With the implementation of the project, an assessmentsystem of Cleaner Production and a training system have been developed and implementation oftechnical updating to the demonstration plant shows that the reduction of zinc loss, and water and fuelcost savings can be achieved. It is believed that the methodology of the project can be appliedthroughout China as the galvanizers see the cost benefits.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

According to the survey of the Chinese Society for Corrosion andProtection in 2006, themonetary loss of steel parts due to corrosionis estimated to be 50 billion yuan (RMB) annually, approximately 5%of GDP in China. Experts say it could be lowered by 20e30% ifeffective protection measurements were adopted. Hot Dip Galva-nizing (HDG), as a metal finishing industry, provides steel productswith good corrosion resistance in the air, and galvanized steel nowis widely used in construction, transportation, communication, andmany fields of society. The importance of the galvanizing industryhas become clear.

The rapid growth of the Chinese economy has proved to bea boon for the galvanizing industry. Investment in infrastructureand a construction bonanza have resulted in a proliferation of newgalvanizing plants and the expansion of those already established(White, 2007). However, with obsolete technology, equipment andmanagement, the HDG industry has been shown to be one of theindustries which consumes large amounts of raw materials andenergy, produces numerous pollutants and causes seriouscontamination in China.

and Engineering, South Chinaangzhou 510640, China. Tel.:

All rights reserved.

With the increasing concern on environmental and productioncost problems, effective control of pollution and energy saving havebecome urgent tasks for managers and engineers. CleanerProduction (CP), as a strategy for reducing negative environmentalimpact throughout the production processes, avoids and decreasespollution at its source and increases the competitiveness of enter-prise. In the context of manufacturing, CP involves conserving rawmaterials and energy, eliminating toxic chemicals, and reduces thequantity and toxicity of emissions and wastes generated duringproduction (Wang, 1999). The emphasis of such reduction istransferred from end-of-pipe treatment to whole-procedurecontrol. CP has been widely recognized as a useful approach tomitigate pollution during industrial production and is playing anincreasingly prominent role in China’s industrial and environ-mental protection policies. Now CP has been employed in electro-plating, alcohol (Guo et al., 2006), coal (Lu et al., 2008), pulp andpaper (Ren, 1998) industries in China. Many reports (Zhang et al.,2008; Yuan & Shi, 2009; Hicks & Dietmar, 2007) show that thecompetitive advantages of the enterprises are increased byreducing production costs and improving environmental perfor-mance through the implementation of CP.

However, for the HDG industry in China, the evolution process isrelatively slow. Although a few HDG plants have employed someindividual CP technologies, the benefits are quite limited because ofa lack of integration and optimization of CP technologies. Toimprove the efficiencies of reduction of pollutant discharge and

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e1099 1093

resource consumption, effective assessment and optimization of CPsystems for the HDG industry are desired.

The Common Fund for Commodities (CFC) project: The Transferof Technology and Promotion of demand: Batch hot dip galvanizing inChina launched by International Zinc Association (IZA) is assistingin the development of a sustainable after fabrication batch hot dipgalvanizing industry through provision of assistance to key galva-nizers who wish to extend their capabilities of product rangethrough the adoption of relevant technologies and market devel-opment strategies. The predicted achievements of the project are:(1) introduction of advanced technologies and the setting up ofdemonstration plants; (2) development of a complete audit systemof CP for hot dip galvanizing; (3) development of an operationtraining system for hot dip galvanizing. The project is aimed atupgrading the Chinese HDG industry through interventions andinvestment at selected plants and improving the implementation ofCP among plants in China. This paper introduces the Best AvailableTechnologies of operation (Department for Environment Food andRural Affairs, 2004), energy (Briar Associates, 2004) and environ-mental management (Fresner et al., 2007) for hot dip galvanizing,and the implementation progress of the CFC project amongst theselected enterprises.

2. The transfer of technology toward CP for HDG industry

2.1. Features of typical HDG process

A typical hot dip galvanizing process has been developed inmore than one hundred years and now can be divided into thefollowing steps: pre-treatment (degreasing, pickling, fluxing, anddrying), galvanizing and post-treatment (quenching, passivating).Most plants follow this typical galvanizing process duringproduction in China. The galvanizing operation produces atmo-spheric emissions, contaminated wastewaters and solid wasteemissions which could have an environmental impact and maysuggest need for CP options. With the development of HDG tech-nology, there are many Best Available Techniques (BAT) of opera-tions, energy and environmental processes in the world(Department for Environment Food and Rural Affairs, 2004; BriarAssociates, 2004; Fresner et al., 2007; Regel-Rosocka, 2010;Bennasr et al., 2008), which can be transferred and used in CP forHDG in China.

2.2. Advanced operating technology

Good process flow, optimized plant layout and good housekeepingare essential to get high product efficiency, minimize the environ-mental impact and energy usage. In many old and simple plants,flow of materials causes interruption in production; racks, baskets,crates may not return to the starting point; storage methods ofchemicals, raw materials and articles may be poor; incorrectreceiving regulations of black articles can occur. All these wouldlead to low efficiency, bad product quality and waste of resources.

Articles to be galvanized are first degreased to get rid ofcontaminated oils or grease, then pickled to remove adhering millscale, rust and oxide films on the surface of the article by

Table 1Specific energy consumption in a HDG plant (MJ/ton of steel galvanized).

Natural gas Elect

Zinc kettle heating Caustic and flux tanks heating Crane

Average 1785 797 6Percentage 66.4% 29.6% 0.3%Range 1150e2740 460e1200 4e9

immersion in either hydrochloric acid or sulphuric acid solutions.Low acid concentration pickling technology can be used in order tominimize acid fume emission if the pickling rate can be satisfiedwith the galvanizing production. Suitable acid inhibitors and fumesuppressants can be used at same time. In Europe, some plants usean acid tank to do zinc stripping. This step is to strip the coating ofre-galvanized articles, jigs and zinc wires by using low concentra-tion fresh hydrochloric acid, and the stripping solution containingzinc chloride can be reused.

Rinsing operations following acid pickling are performedprimarily to ensure that acid and iron contaminants carried fromthe pickling bath with the work are prevented from adverselyimpacting the fluxing and galvanizing operations. In order to getminimum contaminant carryover to the flux bath, a very cost-effective rinsing process, backwards counter-flow rinsing, can beused.

The acid-cleaned steelwork is immersed in a chemical fluxsolution that removes the iron oxidefilm (which formson the highlyreactive steel surface after acid cleaning) and prevents furtheroxidation before galvanizing. The flux also facilitates optimumreaction of themolten zincfilm, resulting inmore uniform coverage.Theuseof zinc ammoniumchloride solution (ZAC) as aflux results inless fume release during galvanizing than occurs with the alterna-tive ammonium chloride process. Iron build-up in the flux solutioncanproduce excessive dross generation in the zinc kettle and shouldbe monitored to determine maximum permissible levels. A FluxingPurification and Regeneration System can be used to treat flux solu-tions continuously, whichmakes the iron precipitate out of solutionas ferrichydroxideand regenerates zinc chloridebyadding strippingsolution from acid stripping bath.

Galvanizing is performed by the immersion of fluxed and driedsteelwork in molten zinc contained in a kettle heated to approxi-mately 440e460 �C. Zinc alloy technology has been proved to beeffective, which can lower the cost and improve the quality ofproduct.

After galvanizing, the work is commonly quenched inwater andthen passivated to protect it from wet storage stain (white rust).Chromum-free passivating technology can be used instead of toxichexavalent chromium passivation.

2.3. Advanced energy technology

By far the greatest energy consumption in a galvanizing plant iszinc kettle heating, other energy uses include heating of pre-treatment (degrease, flux, etc.) tanks, drying, cranes and so on.Specific energy consumption in a HDG plant is shown in Table 1 inmega joules per ton of steel galvanized. As seen from Table 1, withinthe galvanizing process over 95% of the energy use is thermal, andenergy saving opportunities can arise by some special methods.

2.3.1. Degrease and flux tanksThe degreasing (including rinse) and flux tanks can be heated to

improve the degreasing and fluxing efficiency and pass some heatinto the article prior to galvanizing.

The energy consumption of these heated tanks can be reducedin the following ways.

ricity Total

s Process equipment and lighting Other peripheral uses

95 5 26883.5% 0.2% 100%56e120 3e12

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e10991094

Cover during non-production hours. For the process tanks, Heat islost from the tanks primarily through convection and evaporationfrom the surface of the liquid. The rate of loss is dependent uponthe differential temperature between the tank and workspace andthe surface exposure to air movement.

Insulation of tank walls. Where tanks are heated the externalvertical walls should be fitted with suitable composite insulatingpanels.

Temperature control (if heated from a boiler). Many tanks areheated by waste heat from the galvanizing baths and temperaturecontrol is not a requirement. Where tanks are heated from a dedi-cated boiler, via a heat exchanger or internal tank coils, then suit-able temperature controls should be installed to prevent both overand under temperature conditions occurring.

Set Back or off for non-production periods. Boiler operation isparticularly inefficient at low loads. As a result, where tanks areheated from a dedicated boiler plant consideration should be givento switching the boiler off during non-production periods, such asweekends.

Improving boiler efficiency. Boilers that heat pre-treatment tanksshould be regularly maintained, including flue gas testing to opti-mize the combustion conditions.

Pipework insulation. All pipework and valves within the boilerhouses and on the distribution circuits that serve the tanks shouldbe fitted with suitable insulation jackets.

2.3.2. Drying chambersDrying in a chamber can result in a considerable increase in the

article temperature prior to galvanizing, so reducing the thermalshock on the bath. However, the poor operation of dryers can leadto a profound and substantial increase in the energy consumptionof supplementary burners. In Europe, many galvanizing companiesutilize drying chambers after the flux tank and prior to dipping inthe zinc bath. Others allow a period of natural drying prior todipping although the use of dedicated drying chambers canincrease throughput. Where drying chambers are installed manyopportunities exist to ensure their efficient operation.

Door seals. Doors are commonly fitted to chambers to reduceheat loss.

Isolation of supplementary burners when doors open. Whereadditional burners are installed to supplement the waste heat fromthe baths, these should be linked to the operation of the door.When the doors are opened the burners should modulate to lowfire (or off).

Supplementary burner control. The temperature required in thechamber should be set to maximize the available benefit from thewaste heat andminimize the operation of the supplementary burners.

2.3.3. Galvanizing bathsThe galvanizing baths are the largest user of energy at all sites,

with typical furnace efficiencies of 60e70%. Bath energyconsumption can be reduced in a number of ways througha combination of improved housekeeping, maintenance and capitalinvestment in new technology.

Improving combustion system settings to reduce gas consumption.Covering the bath to reduce surface losses.Reducing minimum heat input.Replacement burner types. Flat flame radiant burners or highvelocity pulse fired burners are first choice during the initialconstruction of the bath. Providing controls are set effectivelyand the bath has been designed with consideration for the typeof burner installed, there is little to choose in terms of efficiencybetween radiant and convective type heating.PLC furnace control to provide continual optimum performance.

2.3.4. Heat recoveryWaste heat can be recovered from furnace flue gases and the

quench tank. It is estimated that 15% of the galvanizing bath heatinput can be saved by utilizing the waste heat. The recovered heatcan be used at pre-treatment tanks, as a priority, and then thedrying chamber.

2.4. Advanced environmental technology

Some expected emission points would be generated at eachprocess step, and can be treated in advanced environmentalequipments.

Spent caustic solutions, spent acid solutions and spent rinsewater can be treated in Waste Water and Spent Acid TreatmentSystems. The treated water can be reused after a careful chemicalanalysis.

To reduce acid fume emitted in the plant, Pickling Fume Extrac-tion System can be used and the fume can be extracted and absor-bed in water.

In order to separate the fume particles and clean discharged air,Zinc fume capture & filter systems should be installed to capture andfilter all fume emissions.

During galvanizing, zinc dross, a zinceiron alloy, forms andsettles to the bottom of the kettle; and zinc ash, a mixture of zincoxide and quantities of entrained zinc, forms on the surface of themolten zinc. It is possible to recover metallic zinc from theseresidues. It has been shown that between 60 and 80% metalliczinc can be recovered from ash (ZnO) and reused for coatingproduct. Zinc residues of ash and dross have values of between 60and 80% of the market price of zinc. These zinc by-products areused as additives in paint and agricultural fertilizers. Zinc resi-dues represent a source of substantial and costly material waste,which should be managed correctly in order to reduce opera-tional costs.

In general, the CP system is integrated technology, which isexpected to be composed of a series of individual techniques. Usingthe above mentioned BATs, a suggested CP system can be built upand is illustrated in Fig. 1.

3. Opportunities for improvement of Chinese HDG

Though CP techniques can be available and government ismaking efforts to promote CP at all levels, CP in the Chinese HDGindustry still faces many challenges (Shi et al., 2008; Liu, 2009;Zhang and Wen, 2008; Shen et al., 2010), these include:

� limited financial incentives (these are no systems in place toassist with costing or assessing environmental managementprocesses and no government partnerships such as tax incen-tives, rebates or soft loans)

� insufficient awareness (without national policy devolving toprovinces and municipalities in a coherent manner, there is nomeans to promote the concept at local level. Thus, awareness ofhow to address environmental matters is left to individuals andnot promoted in a sensible manner).

� no understanding of the cost benefits (CP can save costs ininstanceswhere process changes lead to improved efficienciesealthough largely a result of poor awareness there is no incentivefor CP suppliers to promote their services).

� human resources (often, expertise lies only with very topmanagement and little time can be devoted to non-coremanagement issues. Second tier management is often poorlyeducated with few skills and has learnt technical skills throughpractice resulting in an inability to search for new concepts andideas)

PROCESS Wastes OUtputs

DEGREASING

WATER RINSE

PICKLING

spent solution

Wastewater

spent acid

Waster water & spent acid treatment system

Acid fumes

Clean water

Filter cakes

Pickling fume extractionsystem

Flux purification & regeneration system

Zinc fume capture & filter plant

ZINC STRIPPING

WATER RINSE

FLUX

DRYING

GALVANIZING

WATER QUANCH

PASSIVATING

Stripping solution

Wastewater

Flux solution

Zinc dross, zinc ash

Wasterwatewastewater

Spent solution

Zinc fume

Off-site recovery

Wastewater

Clean air

Filter cakes

Treated solution

filter powder

Chromum-free passivatingtechnoglgy

By-products

Recoved zinc

CP TechnologiesPROCESS Wastes OUtputs

DEGREASING

WATER RINSE

PICKLING

spent solution

Wastewater

spent acid

Waster water & spent acid treatment system

Acid fumes

Clean water

Filter cakes

Pickling fume extractionsystem

Flux purification & regeneration system

Zinc fume capture & filter plant

ZINC STRIPPING

WATER RINSE

FLUX

DRYING

GALVANIZING

WATER QUANCH

PASSIVATING

Stripping solution

Wastewater

Flux solution

Zinc dross, zinc ash

Wasterwatewastewater

Spent solution

Zinc fume

Off-site recovery

Wastewater

Clean air

Filter cakes

Treated solution

filter powder

Chromum-free passivatingtechnoglgy

By-products

Recoved zinc

CP Technologies

CP technologies for the process of Hot dip galvanizing

Fig. 1. CP technologies for the process of Hot dip galvanizing.

Table 2The galvanizing cost reported for a Chinese plant and a North American plant.

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e1099 1095

� technical know-how (although a CP Law is in place in China,there are no service bureau to assist companies to implementCP technologies)

� inadequate implementation (an ad-hoc process is developingwhere some companies have an environmental managementpolicy which is implemented whereas many just give lip-service to the concept e systems may be installed and leftunused or just not installed if insufficient regulatory pressure isapplied by the local authority)

� policing (no equitable penalty process is in place and regula-tions are applied in a favour or conflict manner)

As a result, overall, in China, many enterprises have the ideathat CP just means environmental protection. Environmental

Item Type % Costin China

% Cost inNorth America

Capital and interest Fixed duringpay-back period

8.8 24.3

Administrative Fixed 1.2 3.5Supplies Variable 1.4 5.2Maintenance Mostly fixed 1.1 3.4Energy Mostly fixed 7.5 7.1Zinc Variable 72 27.1Spent chemicals Variable 3 2.1Labor Variable 5 27.3

Total 100 100

protection, as emphasized by local government, is still focused onend-of-pipe treatment and the application of pollution controltechnologies. Environmental protection is therefore often viewed asa technical andnecessaryexpensiveoutlay that is primarily requiredto meet pollution control standards. The challenge in China is thedevelopment of a correct awareness for the enterprises, and tomakeenterprises understand that CP can bring economic benefits as wellas improving environmental performance, and provides opportu-nities for developing a sustainable hot dip galvanizing industry.

To highlight the opportunities; galvanizing costs in a Chineseplant are compared to those in a North American plant (see Table 2).

The percentage costs of rawmaterials, chemicals and energy used inthe production process are up to about 80% in China, but only 36.3%in North America. This highlights the potential improvement toreduce the cost of galvanizing by technical improvement. Forexample, Many Chinese galvanizers believe that coal is the cheapestfuel if there is no environmental pressure. Table 3 shows the data offuel consumption and energy costs from different types ofcombustion systems in different plants. As can be seen from Table 3,the lowest direct cost of energy is not using coal as fuel. A goodcombustion system and clean fuel canprovide a lowenergy cost and

Table 3Comparison with different type of fuel.

Type of fuel Temperaturecontrol/combustion system

Energy consumption(/tonne of steel)

Unit pricea

(RMB/tonne)Energy cost(RMB/tonne of steel)

Merits and Demerits

Coal Manual 100e130 kg 800 80e104 Burning incompletely;Difficult control of zinc bath;Short life service of zinc kettle;Heavy pollution(SO2, CO2)

Waterecoalegas Manual 70e100 kg 800 56e80 Difficult control of zinc bath;Short life service of zinc kettle;Heavy pollution(SO2, CO2)

Heavy-oil Manual 30e40 kg 3500 105e150 Difficult control of zinc bath;Short life service of zinc kettle;Heavy pollution(SO2, CO2)

Diesel Auto-control/flat-fire 20e25 kg 5500 110e137.5 Good control of zinc bath;Long life service of zinc kettle

Electricity Auto-control/Thyristor 110e130 kWh 0.7 77e91 Good control of zinc bath;Long life service of zinc kettle

Natural gas Auto-control/High speed pulse fire 20e25 Nm3 2.5 50e62.5 Good control of zinc bath;Long life service of zinc kettle

a The unit price is different in different places in China.

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e10991096

long zinc kettle service life. Therefore, CP provides opportunities forcost savings and increased productivity, less waste, fewer air emis-sions and effluent production and improved plant capability.

Although some individual CP technologies have been applied ina number of plants, an integrated assessment and implementationprocedure are lacking for proceeding with practical CP technologiesfor HDG plants in China. The CFC project aims to set such proce-dures to prompt CP in China.

Overseas auditor

training

Pre-audit system

development

Plant selection

Pre-audits

Full audit system

development

Identification and sel

technology suppliers

Full audits

Feasibility studies

capital applications

UNEPIE and other prOperator training

tool development

Installation

Implementation of

technologies

Training in new

Practices and system

Conclusion seminar

Implementation of tThe systems development

Flow Chart of the CFC p

Fig. 2. Flow Chart of the

4. Systems approach built up during the implementation ofthe CFC project

4.1. Project implementation

Abrief descriptionof theoverall project process is shown inFig. 2.Four representative plants have been chosen to implement theproject. Among them, Plant 1 is a state owned (SOE) transmission

ection of

Development of market data

base system & project report

Market data report and industry

education/conference 1

Market data and project impact

report

and

using

otocols

Market data report and

industry education/conference

2

and

new

Works

s

Market data and project impact

report

Market data report and

industry education/conference

3

he project Promotion of the project

roject process

CFC project process.

Fig. 3. Radar map of the pre-auditing assessment of the selected plants.

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e1099 1097

tower producer and has the biggest HDG production line in China,attached to its steel fabricated plant; Plant 2 is one of the mostprofessional hot dip galvanizing enterprise and has the largestannual production in China, and it is a private enterprise; Plant 3 isa middle scaled professional hot dip galvanizing enterprise anda foreign investment enterprise; Plant 4 is a private enterprisespecialized in design and manufacture of Port and Harbor machin-eries, tapered steel tubes and steel structures. These 4 plantsrepresent the different types of Chinese plants, and will becomedemonstration plants after the project finished.

Two technical peoplewith experience in hot dip galvanizingwereselectedas theTechnicalAuditors for theproject, andhavecompletedAuditing Training which included advance technologies of HDG,energy saving and CP auditing at the Danish Technical Institute.

The selected plants have completed the pre-auditing, full-auditing, feasibility analysis, and the final layout of CP and technicalimprovements have been determined. Using the loan from the CFC

Table 4CP technologies needed in the selected plant.

Activity Outputs

Process control 1. Increase in pickling tanks2. Rinse cascade system used after pickling3. Installation of flux purification system

Automatic temperaturecontrol zinc furnace

4. Electric heating system instead of heavy oil com

Environmental equipment 5. Installation of wastewater treatment system6. Installation of acid fume exaction system7. Zinc fume capture & filter system

project, the plants have been built up an integrated CP systemcombined with the several technologies.

With the implementation of the project, an assessment systemfor the CP of the Chinese HDG industry and a training system foroperators have been developed, and the idea of CP to Chinesegalvanizers promoted through several industrial conferences.

4.2. Assessment system for the plants

A complete assessment system, which helps plants to know thecurrent status and determine an integrated CP system combinedwith a series of Best Available Technologies, has been developed.The system includes pre-auditing, full-auditing and feasibilityanalysis.

The pre-audit assessment identifies the main areas where CPoptions could be further assessed and implemented in the plant byorganizing baseline investigations, carrying out on-site inspections

Outcomes

1. Lower acid use, less fume, longer tank life2. Efficiency improvements in water use, less discharge3. Chemicals savings

bustion system 4. Good temperature control5. No emissions of CO2 and SO2

6. Compliance to BAT7. Efficiency improvements8. Extended service life of zinc kettle9. Energy Savings.10. Wastewater can be treated and reused11. Reduce acid fume to atmosphere;12. Reduce zinc fume to atmosphere;13. Good environment for workers.

Table 5Environmental and annual cost benefits analysis for one demonstration plant afterimplementation of CP technical updating.

Environmental benefitsReduction of SO2 emission 120 tonReduction of CO2 emission 6000 tonReduction of zinc consumption 6.7 kg/ton steelReduction of acid consumption 6 kg/ton steelReduction of zinc chloride consumption 1.5 kg/ton steelReduction of water consumption 340 liter/ton steelEnergy consumption(Electricity instead

of heavy oil)120 kwh/ton(40 kg/ton steel)

Economical analysisTotal investment cost $1,205,958Cost of raw materials

saving(zinc, acid, zinc chloride)$839,000

Cost of water saving $5950Cost of energy saving $542,160Cost of maintenance saving $7000Increased operating cost of

environmental equipments�$17,227

Net profit $1,376,883Pay-back period 0.9 year

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e10991098

and evaluating pollution generation and emissions. A pre-auditingquestionnaire was developed and used in the on-site inspections toevaluate the status of each plant from 6 aspects: Operation, Quality,Chemical Analysis, Environmental Management, Safety and Health,and Organization Management. The results of the pre-audits in theselected plants are shown in Fig. 3 as radar maps. This enablesplants to easily assess the current status, set CP goals and developno/low-cost measurements.

Full-auditing and Feasibility analyses identify the optimum CPsystem. In this project, the technical updating andmeasurements forCP have been determined by plants and auditors after full-auditingincluding analyzing causes of waste generation, establishing mate-rial balances and discussions with experts in the country or abroad.Table 4 shows the activities of the technical transfer based on theassessment of full-auditing and feasibility study in one demonstra-tion plant which annual production is about 50,000 tons.

In order to make the whole integrated CP system operateeffectively, a training system has been developed and will be usedin the selected plants after technical improvement adoption. Theevaluation of the whole assessment system will be done duringfuture implementation of the project.

4.3. Cost and benefits analysis after implementation of CP system

A comparisonwith the costs before and after implementation ofCP in the selected plant has been carried out, and the initialinvestments and the benefits after implementation have beenanalyzed as follows:

4.3.1. Process control

(1) Low HCl concentration pickling technology was adopted. 8 pick-ling tanks were built replacing 2 old tanks. The concentration ofHCl is lowered to8e15% from20to25%asthepicklingratecatchesupwith the rateofgalvanizing. TheconsumptionofHCl is loweredto 30 kg/tonne steel from 36 kg/tonne steel. Less acid fumes areemitted and less over-pickling occurs by using this technology.

(2) A rinse cascade systemwas used after pickling. Cascade rinsingcan reduce discharged rinse water volume 100e1000 timescompared to a single tank system. The water consumption islowered from 400 litre/tonne steel to 60 litre/tonne steel. Also,the articles are cleaner and less Fe2þ salt is taken into the fluxsolution (reducing zinc consumption).

(3) A flux purification & regeneration systemwas adopted to filterand clean the flux solution. Stripping zinc from the rejectedproducts, jigs and wires, can generate zinc chloride. So zincchloride, one of the flux chemicals, is saved.

4.3.2. Improved furnace heating systemAnelectrical heating & automatic temperature control systemwas

introduced instead of heavy oil heating & manual temperaturecontrol. The electrical heating system makes the distribution of thefurnace temperaturemoreuniformand the temperature lower. So theservice life of the zinc kettle canbe extended to 10 years (nowonly 2þyears).Automatic temperaturecontrolsareemployed,whichcankeepthe temperature of the zinc bath more stable and is easy to control.Onlyoneworker isneeded forzinc furnacecontrol insteadof4 furnaceworkers. Zinc consumption is lowered to 55 kg/tonne steel from61.7 kg/tonne steel. The emission of CO2 and SO2 is distinguished.

4.3.3. Environmental equipment

(1) A new wastewater treatment system was installed. Forneutralization, NaOH is replaced by lime. Lime is cheaper thusreducing treatment costs. However, the filer cake volume is

increased. At the same time, treated water reusing pipe systemis employed, which can save at least 50% of the water use, andwas connected to the rinse cascade system.

(2) Acid fumewas collected and extracted by enclosing the area andusing an acid fume extraction system. Due to the extraction ofacid fumes in the plant, better conditions forworkers prevail andlonger service life of cranes and other equipment in the plant canbe expected. So air emissions are reduced even though now inChina, no penalty costs are currently in place for poor air emis-sions. Due to the corrosion from acid fume the annual mainte-nance costs of equipment in the plant was about $7000/year.

(3) A zinc fume capture & filter systemwas used to capture the zincfume during production to improve working conditions andreduce air emissions. Currently, there is no legislation tocontrol emissions, implying that fume capture is made ona voluntary basis.

After half a year’s production, a summary of CP technicalupdating options that have been implemented and the cost savingis shown in Table 5. As can be seen from the table, the environ-mental benefits and the cost savings are remarkable.

Through the implementation of the project, four demonstrationplants have been built up to show the cost benefits to other HDGenterprises and the good impacts to the local governments; anassessment system for CP has been developed to make the enter-prises to minimize the investment for technical updating and gainthe most effective results; A training system for operators has beenavailable to make the enterprises get more skillful workers and theimplementation can be implemented sustainably.

5. Conclusion

With industry development of more than 20 years, many plantsare now moving from small family enterprises to more developedand advanced companies to satisfy the need of competition and therequirements of more serious environmental impacts. Governmentstill treats the HDG industry as one of the industries whichconsumes large amounts of raw materials and energy, numerouspollutants and causes serious contamination. To ensure thesustainable development of the hot dip galvanizing industry, theonly way forward is to adopt CP. The need for CP is driven by twoimperatives, the need to meet environmental regulations and theneed to lower production costs.

G. Kong, R. White / Journal of Cleaner Production 18 (2010) 1092e1099 1099

ACP system has been introduced into the Chinese HDG industry.The system has been successful as it addressed:

(1) the whole plant and identified key areas where CP applicationwould provide measurable cost benefits. This comprehensiveapproach has ensured that all aspects of plant operation areaddressed.

(2) the industry through the use of four Demonstration Plants tohighlight the benefits possible, illustrate key technologies andprovide working examples of the application of CP

(3) training through the development of a full plant audit protocoland a plant auditor training program. Trained auditors are nowavailable for ongoing use by the industry

(4) the development of a plant work skills training process toensure that sustainable use of the CP systems is maintained.Whilst it may be argues that a Continuous ImprovementManagement process should be developed, this may be tooambitious at this stage of industry development.

(5) poor awareness within industry and government throughpresentations at various forums within the country.

(6) the financial process to be followed to ensure that sufficientcapital can be leveraged via funding sources by providing a fullcost/benefit analysis through the development of a financialfeasibility framework

Two footnote comments are worthy of mention:A CP Program is being developed by a sub-committee of the

China Galvanizers Association to provide recommendations tocentral government on emission limits and the required policingthereof.

Many Chinese HDG plants have approached the InternationalZinc Association to continue the program and are willing to pay forthe continuation. Thus, it would appear that a sustainable devel-opment model has been developed.

Acknowledgements

The authors are indebted to the many practicing galvanizerswho gave information to assist in compiling this paper. In addition,CFC, ILZSG and IZA are thanked for technical and financial support.

References

Bennasr, J., Snoussi, A., Bradai, Ch., Halouani, F., 2008. Effect of the withdrawal speedon the thickness of the zinc layer in hot dip pure zinc coatings. Materials Letters62, 2150e2152.

Briar Associates, 2004. Energy efficiency opportunities in the UK galvanizingindustry. Good Practice Case Study 393, 1e10.

Department for Environment Food and Rural Affairs, 2004. Integrated pollutionprevention and control (IPPC)dSecretary of State’s Guidance for the A2Galvanizing Sector. Environment Angency, UK.

Fresner, J., Schnitzer, H., Gwehenberger, G., Plannasch, M., Brunner, Ch., Taferner, K.,Mair, J., 2007. Practical experiences with the implementation of the concept ofzero emissions in the surface treatment industry in Austria. Journal of CleanerProduction 15, 1228e1239.

Guo, H., Chen, B., Yu, X., Huang, G., Liu, L., Nie, X., 2006. Assessment of cleanerproduction options for alcohol industry of China: a study in the Shouguangalcohol factory. Journal of Cleaner Production 14, 94e103.

Hicks, C., Dietmar, R., 2007. Improving cleaner production through the applicationof environmental management tools in China. Journal of Cleaner Production 15,395e408.

Liu, Y., 2009. Investigating external environmental pressure on firms and theirbehavior in Yangtze River Delta of China. Journal of Cleaner Production 17,1480e1486.

Lu, X., Yu, Zh., Wu, L., Yu, J., Chen, G., Fan, M., 2008. Policy study on developmentand utilization of clean coal technology in China. Fuel Processing Technology89, 475e484.

Regel-Rosocka, M., 2010. A review on methods of regeneration of spent picklingsolutions from steel processing. Journal of Hazardous Materials 177, 57e69.

Ren, X., 1998. Cleaner production in China’s pulp and paper industry. Journal ofCleaner Production 6, 349e355.

Shen, L., Tam, V.W.Y., Tam, L., Ji, Y., 2010. Project feasibility study: the key tosuccessful implementation of sustainable and socially responsible constructionmanagement practice. Journal of Cleaner Production 18, 254e259.

Shi, H., Peng, S., Liu, Y., Zhong, P., 2008. Barriers to the implementation of cleanerproduction in Chinese SMEs: government, industry and expert stakeholders’perspectives. Journal of Cleaner Production 16, 842e852.

Wang, J., 1999. China’s national cleaner production strategy. Environmental ImpactAssessment Review 19, 437e456.

White, R., 2007. A review of the general galvanizing industry and the IZA supportactivities. In: 7th Asia-Pacific General Galvanizing Conference. Beijing,September, pp. 25e33.

Yuan, Z., Shi, L., 2009. Improving enterprise competitive advantage with industrialsymbiosis: case study of a smeltery in China. Journal of Cleaner Production 17,1295e1302.

Zhang, K., Wen, Z., 2008. Review and challenges of policies of environmentalprotection and sustainable development in China. Journal of EnvironmentalManagement 88, 1249e1261.

Zhang, B., Bi, J., Yuan, Z., Ge, J., Liu, B., Bu, M., 2008. Why do firms engage inenvironmental management? An empirical study in China. Journal of CleanerProduction 16, 1036e1045.