«From Threat to an Asset: Water in Steelworks How modern steelworks can improve water related performance via benchmarking and development of High ...»
From Threat to an Asset: Water in Steelworks
How modern steelworks can improve water related
performance via benchmarking and development of High
Density Sludge (HDS) Process
Thesis submitted to the Cardiff University
for a degree of Engineering Doctorate
School of Engineering
Water in Steelworks P. Suvio
The Water Framework Directive (WFD) 2000/60/EC is set to overhaul the management of the water environment within the EU. Following its enforcement in 2015, changes are expected to the current water related regulations and water intensive industries, including steelworks, ought to prepare themselves for changes.
In 2007 Corus Group was taken over by Tata Steel, now one of the World’s top 10 steel producers with its production of 31 MTPA (million tonnes per annum of crude steel).
Tata Steel Port Talbot Integrated Steelworks is one of Tata Steel’s main sites, currently producing some 4.33 MTPA (in 2007) of crude steel (slab) and is a major user of water with its 8 production facilities and supporting functions.
From 2007 to 2011 the author worked as a core member of the World Steel Association Water Management Project. The project included development of a survey to gather water-related data from the World’s steelworks. 29 steelworks took part in the survey and using the data, an extensive assessment of water related performance in steelworks around the World has been carried out. The findings show that water performance related figures, including water use and effluent generation, vary from under 1 to near 150 m3/ts. The average consumption figure being 28.4 m3/ts with once-through cooling using an average 82% of this water. The average effluent discharge figure is 25.4 m3/ts.
For Port Talbot Steelworks these figures are 33.8 m3/ts and 28.8 m3/ts respectively.
An investigation into effluent treatment technologies and efficiencies included carrying out chemical precipitation and co-precipitation titration experiments, especially looking at zinc, in order to better understand the behaviour of relevant metals during hydroxide precipitation reactions. The experimental results were compared against PHREEQCi theoretical geomodelling precipitation prediction data and PHREEQCi 2 indicated minimum zinc solubility is received at pH 9.5. Laboratory experiments support this.
Iron enhances zinc precipitation strongly via co-precipitation. A similar effect, although to a lesser extent, is achieved for zinc co-precipitation with nickel and lead.
The author’s study of the Port Talbot water systems established that the chemical precipitation processes in operation leads to the generation of voluminious sludge that is hard to dewater further. This prompted the initiation of an investigation into the suitability of the High Density Sludge (HDS) process in treating high volume, nonacidic low metal concentration effluents, such as steelworks final effluent. Prior to this research the HDS process has been used mainly for the treatment of mine effluents and its suitability in treating non-acidic, low metal concentration effluent has not been fully explored. During the trial, a 10 L/h influent feed rate was aimed for with a half hour retention time at the first two reactors. The flocculant feed rate was around 2.5-3 mg/l of treated effluent throughout the trial. At the end of the trial the sludge concentrations exceeded 17% (w/w), while the treatment efficiencies of zinc and other metals stabilised and improved. Furthermore, the sludge was behaving as HDS sludge achieving high settling rates in excess of 22 m/h at 5% (w/v). Solids concentrations and sludge filterability had improved with the specific cake resistance reducing from the ‘single pass’ precipitation sludge near 35,000 Gm/kg to the 777 Gm/kg after 2 weeks of trial to a mere 169 Gm/kg at the end of the HDS trial.
Declaration This work has not previously been accepted in substance for any degree and is not being concurrently submitted in candidature for any degree.
Signed ……………………………………….. (candidate) Date ……………………… Statement 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of EngD.
Signed ……………………………………….. (candidate) Date ……………………… Statement 2 This thesis is the result of my own independent work/investigations, except where otherwise stated. Other sources are acknowledged by explicit references.
Signed ……………………………………….. (candidate) Date ……………………… Statement 3 I hereby give consent for my thesis, if accepted, to be available for photocopying and inter-library loan, and for the title and summary to be made available to outside organisations.
Signed ……………………………………….. (candidate) Date ………………………
I would like to thank Mr. James D Davies, Manager of Strategic Utilities Development and the whole Energy Operations Department of Tata Steel Port Talbot Steelworks for their support during the project. I would also like to thank G.E. Water and Process Technologies for their help during the earlier stages of the research.
I am very grateful to my supervisors at Cardiff University, Professor Keith Williams and Professor Tony Griffiths for their help and guidance throughout the project.
I am thankful to Tata Steel Strip Products Europe for the support during the research and for the permission to publish this thesis and the Engineering and Physical Sciences Research Council for the support during the project.
Last but not least, I would like to thank Peter for his understanding and support throughout this project.
2.1 UK Water Related Legislation
2.1.1 Environment Agency
2.1.2 Environmental Protection Act 1990
2.1.3 Dangerous Substances Directive 1976
2.1.4 Integrated Pollution Prevention and Control
2.1.5 Water Act 2003
2.1.6 Water Framework Directive
2.2 Tata Steel Europe Port Talbot Steelworks
2.2.1 Port Talbot Steelworks Integrated Steel-making Process
2.3 Water in Integrated Steelworks
2.3.1 Effluent from Steelworks
2.3.2 Sustainable Water Management (SWM) in Steelworks
2.4 Introduction into Industrial Effluent Treatment
2.4.1 Treatment technologies
3 CRITICAL ANALYSIS OF THE PORT TALBOT STEELWORKS WATERSYSTEMS
3.2 Water Supply Systems
3.2.1 Water Supply Flows
3.2.2 Water Mass Balance
3.2.3 Supply Water Quality and Pretreatment
3.3 Effluent Water Systems
3.3.1 Effluent Water Flows
3.3.2 Nautilus Final Effluent Water Treatment System
3.4 Steelworks Wastewater Constituents
3.4.1 Discharge Consent Limits
3.4.2 Wastewater Constituents against Consent Limits at the Long Sea Outfall........... 47 3.4.3 Wastewater Constituents against Consent Limits at the Facilities
3.4.4 Nautilus Final Effluent Treatment System Performance Results
3.4.5 Nautilus Effluent Treatment System Performance Experiment
3.4.6 Nautilus Effluent Treatment System Performance Experiment Results............... 59
3.5 Facility-Specific Water Systems
3.5.1 Water and Effluent Performance
3.5.2 Coke-Ovens Water Systems
3.5.3 Sinter Plant and Raw Material Handling Water Systems
3.5.4 Blast Furnaces Water Systems
3.5.5 BOS Plant Water Systems
3.5.6 Continuous Casting Water Systems
3.5.7 Hot Mill Water Systems
4 WORLDSTEEL WATER MANAGEMENT PROJECT
4.1.1 Aim and Objectives
4.2 Project timeline and meetings
4.3 Project team
4.4.1 Scope and Boundaries
4.5.1 Survey Data
4.5.2 Calculations for Water Related Performance
Steel Plants’ Water Consumption and Discharge
4.5.3 4.5.4 Integrated versus Non-Integrated Steel Plants
4.5.5 Water Performance per Facility
4.5.6 Coke Making
4.5.7 Blast Furnaces
4.5.8 Cooling Water Usage
4.5.9 Water Management Matrix
5 METAL REMOVAL FROM WASTEWATER BY CHEMICALPRECIPITATION
5.2 Metal Solubility
5.3 Chemical Precipitation and Co-precipitation
5.3.2 Choice of a Precipitation Reagent
5.4 Laboratory Studies - Precipitation and Co-precipitation Experiments
5.4.1 Experimental Solutions
5.4.2 Sodium Hydroxide Titrations
5.5 Theoretical Prediction with PHREEQC
5.6.1 Zinc Precipitation and Co-precipitation Results
5.6.2 Copper Precipitation and Co-precipitation Results
5.6.3 Nickel Precipitation and Co-precipitation Results
5.6.4 Lead Precipitation and Co-precipitation Results
5.6.5 Iron Precipitation and Co-precipitation Results
5.6.6 Cadmium Precipitation and Co-precipitation Results
6 FORMATION OF HIGH DENSITY SLUDGE FROM STEELWORKSEFFLUENT
6.2 Types of Treatment Processes
6.2.1 Conventional wastewater treatment system
6.2.2 Simple Sludge Recycle Process
6.2.3 High Density Sludge (HDS) Processes
6.3 Formation of High Density Sludge
6.3.1 Development of the HDS Process
6.4 Important Process Parametres for the Formation of HDS
6.4.1 Solid Recirculation Ratio
6.5 Sludge Quality
6.5.1 Sludge Densities during HDS
6.6 Advantages of HDS
6.6.1 Sludge Disposal
6.7 Sludge Dewatering
6.7.1 Filter Pressing
6.7.2 Sludge Filterability
6.8 Laboratory Studies – Continuous High Density Sludge Process Trial for Steelworks Final Effluent
6.8.1 Plant Description
6.8.2 Sludge Recirculation
Laboratory Studies – Filtration Experiments
6.9 6.9.1 Svedala Piston Press Description
6.9.2 Filtration Experiment Procedure
6.10 Water Analysis Techniques
6.11.1 Pilot Plant Performance Monitoring
6.11.2 Sludge Filtration Characteristics
9 FUTURE WORK
11.1 Appendix I Publications
vii Water in Steelworks P. Suvio Figures FIGURE 2.1 WEST WALES RIVER BASIN DISTRICT (ENVIRONMENT AGENCY, 2009)
FIGURE 2.2 CLASSIFICATION OF SURFACE WATER
FIGURE 3.1 WATER ABSTRACTION POINTS AT TATA PORT TALBOT STEELWORKS (WATER EXPERTS TEAM,2006)
FIGURE 3.2 MAIN WATER RESERVOIRS AT THE PORT TALBOT STEELWORKS
FIGURE 3.3 PORT TALBOT WATER MASS BALANCE (2007)
FIGURE 3.4 PORT TALBOT SERVICE WATER SYSTEMS (MORRIS, 2009)
FIGURE 3.5 TATA PORT TALBOT STEELWORKS WASTEWATER SYSTEM LAYOUT
FIGURE 3.6 WASTEWATER FLOWS INTO SUMP NO.
2 (M3H) IN 2008
FIGURE 3.7 PICTURE OF THE NAUTILUS WATER TREATMENT SYSTEM FROM THE TOP (GOOGLE MAPSWEBSITE)
FIGURE 3.8 HORIZONTAL CROSS-SECTION OF THE NAUTILUS SEDIMENTATION CHANNELS (DRAWINGOFFICE, 2007)
FIGURE 3.9 PICTURE OF ONE OF THE NAUTILUS
FIGURE 3.10 LSO DAILY AVERAGE FLOWS IN 2007
FIGURE 3.11 LSO DAILY AVERAGE PH IN 2007
FIGURE 3.12 LSO DAILY AVERAGE SUSPENDED SOLIDS CONCENTRATION IN 2007
FIGURE 3.13 LSO DAILY AVERAGE SOLUBLE ZINC CONCENTRATION IN 2007
FIGURE 3.14 LSO DAILY AVERAGE OIL CONCENTRATION IN 2007
FIGURE 3.15 COLD MILL EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007.
............. 51 FIGURE 3.16 CAPL EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007
FIGURE 3.17 BOS PLANT EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007.
............ 52 FIGURE 3.18 CONCAST EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007................. 53 FIGURE 3.19 SUMP NO 10 EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007............. 53 FIGURE 3.20 BLAST FURNACES EFFLUENT SUMP DAILY SUSPENDED SOLIDS CONCENTRATIONS IN 2007.... 54 FIGURE 3.21 BLAST FURNACES EFFLUENT SUMP DAILY SOLUBLE ZINC CONCENTRATIONS IN 2007............ 55 FIGURE 3.22 CONCAST PLANT EFFLUENT SUMP DAILY SOLUBLE ZINC CONCENTRATIONS IN 2007............. 56 FIGURE 3.23 BOS PLANT EFFLUENT SUMP DAILY SOLUBLE ZINC CONCENTRATIONS IN 2007
FIGURE 3.24 NAUTILUS WATER TREATMENT SYSTEM WEEKLY COMBINED INFLUENT VERSUS EFFLUENT IN2005-2007
FIGURE 3.25 NAUTILUS WATER TREATMENT SYSTEM PERFORMANCE IN 2005-2008
FIGURE 3.26 NAUTILUS EAST AND WEST CHANNEL REMOVAL EFFICIENCY OF SUSPENDED SOLIDS.
........... 60 FIGURE 3.27 NAUTILUS EAST AND WEST CHANNEL REMOVAL EFFICIENCY OF ZINC
FIGURE 3.28 PORT TALBOT STEELWORKS FULL WATER MASS BALANCE (ADAPTED FROM ENERGYDEPARTMENT, 2005)
FIGURE 3.29 MORFA COKE-OVENS WATER MASS BALANCE (ADAPTED FROM DENLEY, 2007)
FIGURE 3.30 SINTER PLANT WATER MASS BALANCE
FIGURE 3.31 RAW MATERIAL HANDLING WATER MASS BALANCE
FIGURE 3.32 BLAST FURNACES DOCK WATER MASS BALANCE