Examensarbetet handlar om avslamningsbassänger och pumpgropar i Bolidens svenska underjordsgruvor. Avslamningsbassänger och pumpgropar är en del av vattenhanteringen i gruvorna. I dagsläget är designen och arbetssättet i gruvorna olika. Målet är att konstruera och dimensionera en avslamningsbassäng som passar alla gruvor samt dokumentera nuvarande design och arbetssätt. Syftet är att få fram ett underlag till en SOP (standard operating procedure).   Metodiken består främst av fältstudier som utförts i Kristinebergsgruvan, Renströmsgruvan, Kankbergsgruvan samt Garpenbergsgruvan. Även ett besök i en annan svensk underjordsgruva har gjorts för att se hur designen och arbetssättet ser ut i en gruva som inte tillhör Boliden. En enklare litteraturstudie har även genomförts för att dels få en inblick i hur optimal sedimentering fungerar samt om tidigare studier har gjorts om detta ämne. Tillämpning av Stokes lag samt Hazens ytbelastningsteori har använts för att dimensionera avslamningsbassängen med hänsyn till optimal sedimentering. Två olika designer på en pumpgrop och två olika designer på en avslamningsbassäng har tagits fram. En horisontell pumpgrop som kräver lite drivning i berget samt en mobil pumpgrop som är en färdig konstruktion vilken kan byggas ovanjord. I den mobila pumpgropen undviks sedimentering som gör att slamhanteringen kan flyttas till ett lämpligare ställe. Där det exempelvis är lättare att ta reda på slammet. För avslamningsbassängen togs det fram en enkel avslamningsbassäng samt två stycken parallella avslamningsbassänger där sedimentering sker i två steg. Med ett antagande att flödet in i avslamningsbassängen är 20 m3/h och partikelstorleken i slammet är 0,02 mm behöver arean vara 80 m2. Eftersom den beräknade sedimenteringshastigheten och ytbelastningen aldrig kan tillämpas fullt ut behöver bassängen överdimensioneras.

I LKAB:s gruva i Kiirunavaara i Malmfälten tillämpas brytningsmetoden skivrasbrytning, som går ut påatt driva ortar in i malmkroppen, från dem borra uppåtgående hål i malmkroppen, spränga och sedanlasta ut malmen, som med gravitationens hjälp rasar ner i orten.Ett mål för detta examensarbete är att undersöka fragmenterings- och volymmätningens potentiellaeffekt på det dataunderlag som ligger till grund för beslutsfattande i produktionslastningen. Ett målär också att undersöka fragmenteringens effekt på skrymdensiteten vid skivrasbrytning.Analysarbetet baseras på data från ett markörförsök som utfördes i Kiirunavaaragruvan 2013/2014.För att verifiera tillförlitligheten hos det mätdata som ligger till grund för analysen, har metodernaför mätning av massa och skopvolym testats. En känd volym stenmaterial med en givenfragmentering vägdes i en lastmaskin och fotograferades på samma vis som under markörförsöken.Resultatet för volymmätningen visade på en överskattning som minskade med ökande volym och varmindre än 5 % för volymer över 4 m3. Resultatet för viktmätningen indikerade dock ett konsekventfel på över 20 %, vilket dock berodde på felaktig eller inte genomförd kalibrering av just denlastmaskinen.Volymanalysen visade att beräkningsmetoden som LKABs mjukvara för beräkning av järnhalt (WOLIS)använder sig av har utrymme för förbättringar. Efter att de föreslagna ändringarna genomförts,kvarstår dock en överskattning på 14 % av järnutbytet för WOLIS jämfört med volymmätning. Vidjämförelse av järnhalterna vs. utlastningsgrad, så visar WOLIS och volymmätningar liknande trendermed vissa skillnader, och dessa bedöms inte vara stora nog för att påverka lastningsbeslut.Den första hypotesen inför fragmenteringsanalysen var att det skulle finnas ett samband mellanblandad fragmentering och skrymdensitet för skopor som bedömts innehålla endast malm; detta pågrund av att mindre fragment teoretiskt fyller ut hålrummen mellan större fragment. Något sådantsamband kunde inte styrkas utifrån analysen. Den andra hypotesen var att det finns ett sambandmellan grövre fragmentering och lägre skrymdensitet för de analyserade skoporna (både malm- ochgråbergsskopor), och bekräftades av analysen. Detta stämmer väl överens med erfarenheten avbrytningsmetoden, där grövre fragmenterat material ofta inte kommer från malmkroppen, ochdärmed inte är uppsprängt som material i sprängkransarna.Volym- eller fragmenteringsmätning i produktionen rekommenderas inte av detta arbete. Iställetföreslås förändringar av beräkningsmodellen i WOLIS. En systematisk överskattning av malmutbytetkvarstår dock. Överskattningen utreds inte i detta arbete utan föreslås som fortsatt arbete,tillsammans med att se över produktionens rutiner för att motverka förekomsten av överlastning ochutebliven eller felaktig skopvågskalibrering vid service. / In the LKAB-mine in Kiirunavaara in the ore fields of Norrbotten, the mining method Sublevel Cavingis used. Drifts are developed transverse through the orebody from which blast rings are drilledupwards. The ore is blasted while the hangingwall progressively fails and fills the void. By means ofgravity flow both materials may be transported to the drawpoint from which mucking is carried out.One objective of the thesis is to examine the potential effect of volume measurement on the datawhich serves as basis for decision-making in the mucking operation. Another objective is toinvestigate the effect of fragmentation on bulk density. The analysis is based on data acquired from agravity flow study executed in the Kiirunavaara Mine in 2013/2014.In order to verify the reliability of the measured data, which is the basis of the analysis, the methodsfor measurement of bucket mass and bucket volume were tested. A known amount of crushed stoneof a certain size fraction was weighted in an LHD bucket and photographed in the same manner asduring the marker trials. The volume results showed an over-estimation of less than 5 % for bucketswith volumes larger than 4 m3.The error decreased with increasing volume. The weight, however,was consistently off by over 20 %, which could be attributed to improper or overlooked calibration ofthat particular LHD.The volume analysis showed that there is room for improvement in the calculation methods appliedin the software used by LKAB to calculate iron content (WOLIS). With the proposed changeshowever, a 14 %-over-estimation of iron recovery remains for WOLIS compared to the volumemeasureddata. When comparing iron content and extraction rate, the WOLIS-based curves showsimilar trends with some differences. They are not, however, expected to be enough to have bearingon mucking decisions.The first hypothesis for the fragmentation analysis is that a correlation exists betweeninhomogeneous fragmentation and bulk density for buckets containing exclusively ore. Theoretically,smaller fragments should fill the void between larger fragments. Such a correlation could not befound though. The second hypothesis is that coarser fragmentation is correlated to lower bulkdensity (for both ore- and waste rock buckets), which was also confirmed by the analysis. This is inaccordance with the experiences of the mining method, as coarsely fragmented material oftenderives from the hangingwall, and thereby isn’t as finely blasted as the actual blasted ore.A consequent volume measurement is not recommended in the thesis. Instead, changes in thecalculation model of the present measurement system are proposed. A systematic over-estimationof the ore production remains, however. It is suggested to investigate this in a further study. Inaddition it should be paid attention to the current procedures in mucking in particular, the observedoverloading and possible calibration errors.

På grund av nya lagar och företagets egna initiativ om uppföljning av energier och utsläpp har NCC påbörjat kartläggning av dessa faktorer i bergtäkter. För deras bergtäkter av mindre storlek har de önskat framställa en metod med vilken platscheferna själva ska kunna utföra detta arbete. Detta har föranlett till den undersökning som redovisas i denna rapport. Målet med arbetet var att undersöka hur mycket information som finns tillgänglig om energier vid Eker bergtäkt. Sedan ska den informationen användas för att utveckla en metod som förenklar arbetet för platschefer på mindre bergtäkter samt att kartlägga energi och koldioxidutsläpp per ton vid Eker under produktionsåret 2018. I slutändan skapades en excel-fil som beräknar och fördelar energier och utsläpp om information om förbrukat bränsle och el tas fram och matas in. Nyckeltalen som beräknades för energier var 10,03 kWh/ton för totalen, 4,82 kWh/ton för produkter efter krossteg 1, 7,74 för produkter efter krossteg 2 och 14,25 kWh/ton för produkter efter krossteg 3. Nyckeltalen för koldioxid var 2,39 kg CO2/ton för totalen, 1,05 kg CO2/ton för produkter efter krossteg 1, 1,80 för produkter efter krossteg 2 och 3,49 kg CO2/ton för produkter efter krossteg 3. Resultaten visar på att det går att utföra denna typ av undersökningar med den framtagna metoden. Undersökningen avgränsades vid det förberedande arbete med losshållning av berg fram tills lastning på kunds lastbil. Endast de större påverkande faktorerna diesel och el undersöktes. / Due to new laws and the company’s own initiative concerning tracking of energies and emissions in quarries, NCC has begun surveying these factors. For their smaller quarries they mean to produce a method for local site managers, with which they themselves can perform this task. Because of these reasons the study in this rapport has been done. The end goal was to study the amount of available informtion about the energies at Eker quarry. Then Using this information to create a method for site managers to simplify their work as well as performing a survey in Eker concerning energies and emissions per ton of produced materials during 2018. The end product was an excel-file that calculates och distributes energies and emissions as long as data about used diesel and electricity is entered into the file. The survey produced the key figures for energies, 10,03 kWh/ton for the total 4,82 kWh/ton for products after the first crusher stage, 7,74 for products after the second and 14,25 kWh/ton for products after the third crusher stage. The key figures for emissions are 2,39 kg CO2/ton for the total, 1,05 kg CO2/ton for products after the first crusher stage, 1,80 for products after the second and 3,49 kg CO2/ton for products after the third crusher stage. The results show the possibilities to perform this type of survey with the produced method. The survey’s limitations were at the preliminary work with salvoes and ended when the product was loaded to a customer. Only the major factors of diesel and electricity was studied.

The general trend in flotation technology today is towards larger flotation cells, which enables a higher throughput. However, adverse effects such as segregation and reduced froth transport efficiency have also been observed in larger cells. To better understand these problems it is of relevance to understand how the minerals of interest are moving and distributed inside flotation cells. A sampling investigation of industrial scale tank cells has been carried out. The samples have been analyzed by their physical properties, such as grade, solid concentration, particle size distribution and mineral composition. A novel method of measuring the wettability has been validated against traditional techniques for characterizing the surface properties of mineral samples. Different techniques and devices for sampling has also been evaluated. The results showed segregation inside the cells, with the quiescent zone having lower particle size (P80) and lower weight % solid. The grade profile in the vertical direction was relatively constant even though the P80 and weight % solid decreased in the quiescent zone. The smaller particles in the quiescent zone contained higher fraction of soft clay particles, which also correlated with a higher degree of hydrophilicity.

Mine automation has been in development since the 1980s and began to be implemented in the 1990s with the biggest drivers being safety, reduced maintenance and increased productivity. Automation is used in many different mining methods performing a variety of tasks. However, very few studies have been conducted regarding the performance of automatic vehicles in real world mines, neither has much research been done when comparing automated and manual loading.   The purpose of this thesis is twofold. First it is to identify and produce metrics that can be used to compare automatic and manual loading in an underground mining environment. A literary study is presented as a basis for these metrics where the development history is chronicled and the mechanics by which an automated system controls an automatic vehicle is explained. Also included is a description of different mining methods and the part that automation plays in them.   Secondly, the goal is to use these metrics in a real world case study of automated loading in an actual operational mine. The Garpenberg mine, owned by Boliden Minerals, is an underground metal mine located in Dalarna, Sweden, and mining has been done there since the 1200s. Load-Haul-Dump (LHD) machines are used to load and haul ore ether using automation or tele operation. For this study information is extracted from Bolidens internal databases to calculate the metrics which are then used to analyze the performance and reliability of automated loaders, and also to compare manual and automatic loading.   There are mainly three types of metrics that are relevant to automatic and manual loading, these being time related metrics, production related metrics and reliability related metrics.   Since the LHDs dealt with in this thesis are operated both manually and automatically the main use of the time related metrics is to find the relationship between modes of operation in regards to engine hours spent in action, the amount and character of downtime that occurred during the analyzed time span, and the utilization of automatic LHDs during the workday. The most straightforward comparison between manual and automatic loading is the production, i.e. the tonnage of loaded material per unit time. In this thesis production will be analyzed per hour and per loading activity (which run between 3 and 4 hours). Lastly automated and manual loading will be compared on the basis of availability and maintenance, the reason being that LHDs are driven in different ways depending on the mode of operation.   The results show that automatic loading consists of between 14 and 29% of production time while contributing to between 17 and 28% of downtime. No clear connection can be seen between downtime and the relationship of automatic to manual loading, as the difference is not bigger than 10% either way. Manual loading constitutes between 2500 and 3250 engine hours, while time spent during automatic loading constitutes between 420 and 1095 engine hours. The majority of all downtime is not specific to either mode of operation, although automatic specific stops constitutes up to 50% of total downtime for two of the LHDs studied. The distribution of loading activities is similar for both manual and automatic loading, with the number of concurrent activities dipping during lunch breaks and stopping entirely during shift changes. Manual loading peaks around 1000 concurrent jobs while automatic peaks at just fewer than 200.   Regarding production the results show that manual loading is more effective in the short term, as three out of four LHDs has had a higher tonnage loaded per hour. However, when locking at the tonnage loaded per activity, automatic loading catches up to manual loading and produces more tonnage in the long term, with three out of four LHDs getting this higher production.   One interesting result can be found in regards to fuel economy, as one of the LHDs show a reduced consumption of fuel while at the same time having had the largest percentage of time spent in automatic mode. No clear connection can be seen with the rest of the LHDs however, as they show no clear connection between time spent in ether mode of operation and the amount of fuel consumed.   Automatic loading proved to have slightly higher availability than manual loading. In all cases however, the difference in no more than 10% and both modes of operation is above 90% availability. The higher availability of automatic loading is attributed to the fact that manual loading constitutes much more time than automatic loading, and thus there has been more time for breakdowns and production stops to occur for manual loading. The relationship of preventive and corrective maintenance is the same for all four LHDs irrespective of amount of time spent in ether operating mode. Preventive maintenance jobs accounts for more than 90% of the number maintenance actions for all LHDs.   When analyzing what kinds of production stops are the most prevalent, there are differences between manual and automatic loading. For manual loading the most common stops are those that have to do with external circumstances in the mine such as blocked access and fallen boulders, and those to do with minor breakdowns of the LHD. For automatic loading the most common stops are those to do with the automatic system and the equipment used to operate the automated LHD, followed by those caused by external circumstances, similarly to manual loading. Automatic loading has proportionally fewer stops than manual loading in all categories except those unique to automation, which is in turn the biggest category of all production stops.   The conclusions that can be drawn from these results are that automatic loading can outperform manual loading in the long term, but that continuous uninterrupted loading activates are important to achieve this. Automatic and manual loading show comparable reliability when it comes to maintenance and repairs (serious breakdowns are very rare). Availability and the relationship of preventive and corrective maintenance are similar between both modes of operation. The analysis of production stops show that the biggest problem with automatic loading is the automatic systems and the specialized equipments inability to handle the underground environment. Problems with recorded routes and falsely tripped safety systems are the most common stops.       Recommendations to Boliden Minerals regarding the automatic system consist of improving remote troubleshooting and streamlining of problem solving dealing with automation software and hardware. Steps should also be takes towards tailoring the underground environment to better suit automation.   Suggestions to further research consist of deeper studies of all the metrics presented in this thesis to better analyze the role of automation in the global mining industry. Another avenue of study is the combination of the findings in this thesis with the actual environment and layout in the Garpenberg mine to better understand the connection between operating environment and the reliability and productivity of the automatic system.

Zinkgruvan is a Pb-Zn-Ag deposit located in south-central Sweden, owned and operated by Lundin Mining. The ore is beneficiated by a collective-selective flotation circuit, recovering both galena and sphalerite in a bulk rougher-scavenger flotation stage and later on separating them into two final products. Opportunities for increase in zinc recovery in the bulk rougher scavenger flotation stage have been identified as the plant is relying on natural Pb-activation to process the ore. Process mineralogical tools were used to characterize four different orebodies from Zinkgruvan (Burkland, Borta Bakom, Nygruvan and Sävsjön) and evaluate the metallurgical performance for flotation and magnetic separation, following a geometallurgical approach to better understand and predict the behavior of such ore types in processing plant. The first hypothesis in this thesis is that by addition of copper sulfate and increased collector dosage, Zn recovery will be improved without being detrimental to galena flotation. Results demonstrated that there is a significant increase in Zn recovery by further increasing collector dosage and copper-activating the flotation pulp in the scavenger stage. For instance, an increase in zinc recovery up to 16% has been achieved after addition of copper sulfate. Galena is readily floatable while sphalerite takes longer to be recovered. In addition, iron sulfides take longer to be recovered and, after addition of copper sulfate, there was an increase in iron sulfide recovery. The amount of iron sulfides reporting to the concentrate should still not be a problem to the plant. Most of the Fe in the concentrate is still coming from the sphalerite lattice. However, it might be that some orebodies coming into production in the near future have higher amounts of pyrrhotite, which might be a problem. Therefore, magnetic separation methods have been tested to remove pyrrhotite from the bulk ore. The second hypothesis is that the high Fe content in the concentrate might be due to the presence of iron sulfides, in which case they could be selectively removed by magnetic separation. XRD analyses demonstrated that Sävsjön is a highly variable orebody, and that its high Fe content varies with the location inside the orebody, being caused by either iron sulfide or iron oxide minerals. Both monoclinic and hexagonal pyrrhotite have been observed. Davis Tube could remove monoclinic pyrrhotite but it was very inefficient when dealing with hexagonal pyrrhotite. WHIMS, on the other hand, performed well for both types of pyrrhotite. When applying Davis Tube on Sävsjön OLD feed, a concentrate with up to 52.3% pyrrhotite is achieved, at a recovery of 35.32%. However, sphalerite is also reporting to the magnetic concentrate, which would generate Zn losses for the overall process. Zinc losses were up to 15.3% when the highest field strength was applied. Therefore, the applicability of magnetic separation for Zinkgruvan ore must be further evaluated.

Dams that comprise broadly and widely graded glacial materials, such as moraines, have been found to be susceptible to internal erosion, perhaps more than dams of other soil types. Internal erosion washes out fine-grained particles from the filling material; the erosion occurs within the material itself or at an interface to another dam zone, depending on the mode of initiation. Whether or not internal erosion proceeds depend on the adequacy of the filter material. If internal erosion is allowed, it may manifest itself as sinkholes on the crest, increased leakage and muddy seepage once it surfaces, which here is called surfacing internal erosion (i.e. internal erosion in the excessive erosion or continuation phase). In spite of significant developments since the 1980s in the field of internal erosion assessment, the validity of methods developed by others on broadly graded materials are still less clear because most available criteria are based on tests of narrowly graded granular soils. This thesis specifically addresses dams that are composed of broadly graded glacial soils and investigates typical indicators, signs and behaviors of internal erosion prone dams. Based on a review of 90+ existing moraine core dams, which are located mainly in Scandinavia as well as North America and Australia/New Zealand, this thesis will show that not only the filter’s coarseness needs to be reviewed when assessing the potential for internal erosion to surface (i.e., erosion in the excessive or continuing phase); in addition, the grading stability of the filter and the core material as well as non-homogeneities that are caused by filter segregation need to be studied. Cross-referencing between these aspects improves the assessment of potential for internal erosion in dams of broadly graded soils and furthermore it provides aid-to-judgment. / QC 20100715

Stone is a useful resource, for example as a building material, which means that stone materials play a large role in the construction of society. Stone is mined and refined in so-called quarries. There are activities in quarries that have negative impact on the environment. In addition, such industries have traditionally consumed a substantial amount of fossil fuel. Due to these aspects, among others, the quarrying industry should become more sustainable.  Circular economy has the fundamental idea of reducing, reusing and recycling, and can be useful for improving sustainability. To make a business more sustainable, all parts of it should improve in this aspect, including the processes. Process improvement is a strong area of the Lean, which strives to create flow and to remove everything that interferes with the flow. The purpose of the study was to obtain a deeper understanding of how quarries can be improved from a sustainability perspective with a combination of circular economy and Lean. This by reviewing previous theory of sustainability, circular economy, Lean and other relevant areas. The study was carried out as a qualitative case study at, and in collaboration with, a quarrying company in Sweden. The data collection consisted of interviews with relevant people from the company and observations of quarries. The results were compared with the theoretical framework to answer the formulated research questions. The study resulted in several conclusions, the most fundamental is that increased awareness and knowledge about sustainability would bring better possibilities for the company in its work towards a more sustainable busiss. According to the company investments must yield economic profitability, and hence a large responsibility is laid on the customers to demand sustainable products.  Permissions and regulations are, according to the interviewees, obstacles to increased recycling of stone materials, and consequently obstacles to circular economy. An adjustment of permissions to allow more reuse of materials would benefit circular economy. Lean is not entirely applicable due to the long lead times in quarries. However, some aspects of Lean are useful, especially its focus on minimizing wastes. An approach characterized by a circular mindset and by process improvement can be adopted with a combination of circular economy and Lean. Overall, quarrying needs to be seen from a holistic perspective and the communication between all parties in the distribution chain needs to be improved.

In recent years, automated mineralogy has become an essential tool in geometallurgy. Automated mineralogical tools allow the acquisition of mineralogical and liberation data of ore particles in a sample. These particle data can then be used further for particle-based mineral processing simulation in the context of geometallurgy. However, most automated mineralogical tools currently in application are based on two-dimensional (2D) microscopy analysis, which are subject to stereological error when analyzing three-dimensional(3D) object such as ore particles. Recent advancements in X-ray microcomputed tomography (µCT) have indicated great potential of such system to be the next automated mineralogical tool. µCT's main advantage lies on its ability in monitoring 3D internal structure of the ore at resolutions down to few microns, eliminating stereological error obtained from 2D analysis. Aided with the continuous developments of computing capability of 3D data, it is only the question of time that µCT system becomes an interesting alternative in automated mineralogy system. This study aims to evaluate the potential of implementing µCT as an automated mineralogical tool in the context of geometallurgy. First, a brief introduction about the role of automated mineralogy in geometallurgy is presented. Then, the development of µCT system to become an automated mineralogical tool in the context of geometallurgy andprocess mineralogy is discussed (Paper 1). The discussion also reviews the available data analysis methods in extracting ore properties (size, mineralogy, texture) from the 3D µCT image (Paper 2). Based on the review, it was found that the main challenge inperforming µCT analysis of ore samples is the difficulties associated to the segmentation of the mineral phases in the dataset. This challenge is adressed through the implementation of machine learning techniques using Scanning Electron Microscope (SEM) data as a reference to differentiate the mineral phases in the µCT dataset (Paper 3).

Due to the increasing usage of Sn in different electronics, such as solders and in touchscreens, together with Boliden Rönnskärs increased intake of electronic waste as a secondaryraw material, a Zn-containing product called Zn-clinker has increasing amounts of Sn. TheZn-clinker is shipped to Boliden Zn-smelter in Odda, where the Zn-clinker is mixed in withcalcine (roasted concentrate) and leached in several steps. Since Zn-clinker is a product froma halogen removal in a clinker-furnace, the feed material (Mixed Oxide), for this furnace, wasalso investigated since there are plans to replace clinkering with soda-washing in the future.Most of the Sn ends up in the leaching residue which then is deposited in the mountaincaverns close by the Boliden Odda smelter. Boliden is studying the possibility to recoverPb/Ag and Sn content from the leaching residue and create a valuable by-product. Bystudying how the leaching of Sn behaves, together with a characterization of the materials, thefollowing question should be answered: “During which sulphuric acid leaching conditions, ofZn-clinker and Mixed Oxide, is the leaching of Sn minimized?” The leaching results for Zn-clinker showed that 8-10% Sn will leach out, despite changingtemperature, redox potential, time and pH. A characterization of the material with SEM-EDSand XRD-analysis was also conducted to see if Sn could be identified in any phases in thematerials. The studies provided enough evidence that Zn2SnO4 could be concluded to be themain phase in the leaching residue for Zn-clinker, a form that would not leach underconditions presented in this project. However, 8-10% of the Sn will come together with Feand when Fe leach out, so does Sn. The leaching results for Mixed Oxide pointed towards that different phases from them foundin Zn-clinker was present. Sn losses varied between 10-20% but raised to 47% whentemperature was changed to 80 °C during leaching. The SEM-EDS analysis showed that theidentified Sn-phases contained more Sn than in Zn-clinker and together with the leachingresults, a conclusion that Sn would mainly be found as SnO2 or SnO in the Mixed Oxide, butthere is still uncertainty about the distributions of these forms. Unfortunately half of the As leached out during the soda-washing for Mixed Oxide, creating aleachate with Cl, F and As that need to be taken care of. This could be challenging andpresenting a costly side-project for the route different from the Zn-clinker route used today.Another observation was that PbCO3 formed during the soda-washing, a phase that willconsume more sulphuric acid during leaching.