These proceedings deal with all aspects of salt. Most of these are of course interrelated. Before treating the different themes in details, first a rough outline of each theme will be given and also the relations between the different themes.
To group the contribution to the 8th World Salt Symposium 10 themes with a number of sub-themes have been defined:
1. Salt sources and occurrences General geology - Diaperism Geochemistry 2. Salt extraction
Solution mining Rock mechanics Analysis, design and storage 3. Salt production a. Rock salt b. Evaporated salt
c. Sea/solar salt d. By-product salts e. Electrodialysis 4. Salt processing and salt sampling and analysis 5. Salt markets and applications a. Chlor-alkali markets b. Winter road maintenance c. Food and agriculture
6. New uses of salt 7. Salt and the environment Salt works as eco-systems
8. Iodized salt for sustaining IDD elimination 9. Salt and history
10. Salt and health
The papers and the posters in these proceedings have been organised in the following way. The proceedings start with the plenary papers of topics 8 and 10. Then the papers presented in the parallel sessions follow in the order mentioned above. Though not specifically mentioned in the table of contents the poster contributions in the following section are in the same order. A number of papers were not ready when the page numbering started for various technical reasons and have therefore been added as late papers.
Topic 1: salt sources and occurrences is subdivided in two parts, the general geology part and the geochemistry part. This topic is closely related to topic 2, as the latter needs geological data to predict the influence of salt extraction on the stability of the surroundings of the cavern and the surface subsidence. Since the salt layers have been depos-ited by prehistoric evaporation of seas, topic 1 is of course also closely related to topic 3, especially the sub topics on rock salt mining, evaporated salt/ crystallisation and sea/solar salt. In topic 4 attention is paid to the analysis of inclusions in salt crystals, which is useful for interpreting the circumstances under which the salt layers are formed.
As mentioned, topics 2 and 1 are closely related. In topic 2 the attention is more directed to the mechanical behaviour of the salt deposits and their surroundings. In this topic also solution mining and the use of the resulting caverns for storage purposes are discussed. The topics treated here are of course also important for rock salt mining, topic 3a. The construction of a salt cavern can be monitored in a number of ways. Most are treated in topic 2, in topic 4 a paper can be found on the brine analysis for monitoring cavern development. In this topic also a number of other analysis techniques useful for predicting mechanical behaviour can be found. Surface subsidence is an item common to both solution mining and rock salt mining. Papers on this phenomenon can both be found in topics 2 and 3a.
Salt production is divided in a number of separate sections, which all concern a different way to produce salt. Topic 3a deals with rock salt mining, the quality of the produced salt and the maintenance of rock salt mines. Topics 3b, 3c and 3d deal with the direct crystallisation of salt, the main difference being the composition of the brine. Topic 3b mostly deals with the evaporation of brines obtained by solutions mining, which have a low magnesium, potassium and carbonate content. Topic 3c deals mostly with the evaporation of brines obtained by concentrating seawater, which are rich in bitterns. In topic 3d the crystallisation of sodium chloride from a wide variety of brines is treated.
All these three topics are related to the geochemistry part of topic 1 and analysis part of topic 4. In addition to the mentioned items, topic 3b contains a number of papers on the fundamentals of salt crystallisation and industrial crystallisation, in-cluding amongst others, new measurement tech-niques, antisolvent crystallisation and the design of crystallisers. In contrast to the evaporation of brines obtained by solution mining, the concentration of seawater by solar energy extensively involves living organisms. Papers on the behaviour of organisms in medium to extremely saline environments can be found in both topic 3c and topic 7. Topic 3c furthermore concerns the design, maintenance and performance of solar ponds. Topic 3d mainly treats the crystallisation of sodium chloride from waste streams in order to decrease the waste volume. This is of course closely related to the item salt and the environment. Topic 3e has the brine electrolysis and brine concentration using membranes as common de-nominator. The influence of the brine quality on the electrolysis is treated, which is of course related to topic 5a (chlor-alkali markets). Many papers in this section come from Japan, where these techniques are the only way to obtain concentrated brines. Topic 4 deals with two more or less separate issues: processing and analysis.
The former concerns purity, crystal size and in-clusions and is as such closely related to the section on production. Another part of the processing is the application of anti caking agents. Papers on this topic can also be found in topic 5b. The latter deals with analysis, both chemical (purity) and physical (observation of crystal growth processes). Again, these topics are closely related to the crystallisation section. Analysis of iodine in salt, of utmost importance for the proper iodization of salt can be found in topic 8, which amongst others deals with salt iodization technology. The applications and markets of salt are treated in topic 5. Salt has three main applications: chlor-alkali production, winter road maintenance and food and agriculture. The first sub item of topic 5 is primarily focussed on the chlor alkali markets, more technical papers, partly dealing with the economy of the process itself can be found in topic 3e. The second sub item treats a number of aspects of winter road maintenance, ranging from cost/benefit analysis to the role of weather forecasts (late paper) to the use of anti caking agents (which also can be found in topic 4). The third sub item contains a number of papers on the use of salt in and the influence of salt on food, excluding additives to food grade salt, which are treated in topic 8. In the agricultural section papers treat the influence of salt on plants and livestock. Also the use of iodized salt for livestock is discussed here. More technical papers on the influence of saline environments on bacteria, weeds and eco-systems in general can be found in section 6 (new users) and 7 (salt and the environment). The topic salt and the environment covers the whole spectrum of influences which salt can exert on the environment, ranging from the disposal of waste brine to the influence on organisms, eco-systems and the use of solar salts works as a habitat for birds. This part is intertwined with the section on sea/solar salt (3c) and papers discussing the role of organisms in solar salt production and the influence of the salt production on organisms can be found in both sections. Papers on the relation between salt use and health are split into two sections, the major part falls in section 8, salt iodization for sustaining IDD elimination, whereas the minor part are 4 plenary papers on the relation between salt and hypertension (section 10). Section 8 contains papers on the production technology of iodized salt, its analysis (which is related to topic 4) and its use. Also the effects of the use of iodized salt on the elimination of IDD are extensively treated in the papers covering this topic. The application of iodized salt for livestock is treated in section 5b. The addition of micronutrients other than iodine is also covered in topic 8. The section on salt and history (topic 9) contains papers covering topic ranging from prehistoric settlement to salt production in recent times. As this topic is mainly focussed on production technologies, there is a relation with the papers in topic 3.
Session 1: Salt sources and occurrences Session manager: Lukas Hauber
It is well known that salt may be produced in three different ways: in solar ponds, by dry mining and by solution mining. The two latter techniques need a geological expertise in regard to extent, structure and quality of the salt layers or diapirs. It is therefore the task of the geology to prepare the demanded information in as good and complete manner as possible. An up-to-date and complete description of the occurrence of a salt layer or a diapir is most important for the success of a mining project and for the safety of the operation. Salt is not only a mineral essential for the human being and chemical industry today. It has also a specific interest in other domains such as oil industry where salt with its tightness builds up the roof of oil and gas reservoirs and influences the migration of hydrocarbons. Another use which becomes more and more important is the creation of space for underground storage for hydrocarbons such as oil and gas for the disposal of chemical or radioactive waste In the first case the leaching process is used to create the necessary cavern, mostly in salt domes, in the second case existing space of dry mining is used for storage. In regard to the safety of the storage the geology is one of the most important criteria. Let us not forget that salt is also a very important medium in geology as a lubricant in overthrusting and in hydrogeology it is an important factor of groundwater chemistry due to the high solubility. When we look at the nearly thirty papers of this section we realise the complexity of the geological questions to be answered. Some papers deal with general aspects of salt occurrences in restricted basins and in rift valleys with subsidence, even with salt dissolution and drying up in between the cycles.
The largest part of the papers deals in one or another way with the knowledge of the internal structure. There are different ways to get the relevant data, e.g. by seismic surveys, mostly done by the oil industry, the analysis of the embedded insoluble sheets, or the examination of the fabric and composition of salt crystals The creation of digital models of salt diapirs is also discussed and is a good tool to check the data with the general setting of the salt field. These models can also be usefull in regard to problems of security of caverns or waste disposal. An other important field in section 1 is the different aspects of geochemistry. There are two main aspects treated: the geochemistry of continental salars or salt basins and the geochemistry of fluid inclusions in salt crystals. The mineralogical composition of restricted, closed continental basins depends on the. geological framework of the basin. Very often volcanological events help to add a specific geochemistry, e.g. Boron, which therefore may be found in salt layers of continental origin as Borate. The analyses of fluid Inclusions In salt crystals lead to resulting compositions of the seawater during the geological time scale. It seems that the chloride and sulphate ratio may have changed during geological times. Other contributions in the geochemical part of session 1 document the occurrence of rare elements in brines and their economical impact. Further on we find also experiences with sulphate saturation in warm brines and the use of these brines. Some papers deal with the modelling of the geochemical composition of different brines in complex chemical systems. This allows a better understanding of the origin of the salt layer but also of the treatment of such brines, mostly in continental basins. This short summary shows that the field of salt geology is still very active and that it takes advantage of new tools in the field of geology, such as geophysics and modelling. Modelling of geological problems will have a broad use in the future.
Session 2: Salt extraction Session Manager: Reinhard B. Rokahr
At first sight the contributions for the 8th symposium can be subdivided in the following fields just like at the last congress in Kyoto in 1992: Cavern-Solutioning, Laboratory and Field Testing, Operation and Storage, Subsidence and Environment, Finite Element Modeling. At second sight it becomes apparent that the authors have made the effort to present their results not isolated anymore but have brought them into a greater context. The question is treated to what extent the subjects are interconnected in certain cases.
It becomes evident that concerning the dimensioning of salt caverns, one is not content anymore to make certain assumptions but wants to get the certainty that the assumptions apply to a specific case. Of course, it is no surprise to observe this trend as cavern operators have gathered sufficient experience and data and the constant development of different instruments and computer technology and software have made a more exact registration of the actual situation possible. Furthermore there is more interest in analyzing more deeply the experimental laboratory data and in-situ observations in order to undertake a more economical optimization during cavern operation. The criteria for the selection of the papers were very strict: In particular it was asked for that at least 50% of the findings should be up-to-date and have not yet been published. Also the progress should be visible that has been achieved since the 7th symposium. Altogether 23 contributions that are demanding from the scientific point of view, interesting from the engineering point of view, and orientated by practice from the industry's point of view were selected. For the first time data is published that is going to receive international attention because of it's importance concerning the forecast of subsidence as a result of cavern operation. The way is presented how to assess cavern convergence sufficiently accurate on the basis of production data. Besides the definite answer is given concerning the question whether the quantity of rock salt which is tested in the laboratory is sufficient to give a statement on the material response of millions cubic meters of in-situ rock salt. The subject of creep rupture which was discussed at the 6th symposium in Toronto in 1983 has been taken up again -this time embedded in the subject of damage and healing of rock salt under loading and unloading conditions. Additionally interesting experiences in underground storage of industrial waste in the USA are presented. Furthermore the problems are described vividly which arose during brine production and the drilling phase and which asked for a high amount of creativity, courage and experience.
Session 3: Production
Session 3a: Rock salt mining Session manager: Vincent Defourny
Since the highest antiquity, mankind extracted out of the mine the substances, among which salt, it needs for its life and realizations. It is amazing to see how various branches of science have impregnated the mining methods in order to improve their productivity and safety. And still, the miner faces Nature who is his everyday but always to be respected and feared partner. The papers in this section can be divided into two groups. The first group deals with the process technologies involved in rock salt mining, mine operation and exploration. Optical sorting of rock salt, radar investigation of salt deposits and the description of the operation of several rock salt mines are amongst the papers in this group. The second group of papers deals with the issue of mine protection. Especially the influence of water, in the form of an inflow or in the form of humid air is an important factor. Three papers deal with a water inflow and its consequences, one paper treats the influence of changes in air humidity on a rock salt mine.
Session 3b: Evaporated salt Session manager: Gerda van Rosmalen
Crystallisation of salt is one of the fundamental processes in the production of salt. For evaporated salt and solar salt this is of course obvious, but also in the case of rock salt an additional (re)crystallisation step may be a very efficient means to improve the product purity. Such a process is treated in detail in the keynote lecture by L. Ninane.A number of papers concern the crystallisation of salt in order to improve its characteristics in terms of purity and product performance. Efficient washing of salt is addressed as is the role of supersaturation and the formation of inclusions. In industrial crystallisation the choice of the crystalliser has a decisive influence on the quality of the crystalline product. The choice of a crystalliser, especially for large scale products is never straightforward. Papers by Yamada, DiMonte, Ishii, Hasegawa show the importance of this issue and the results, which can be achieved with a proper equipment choice. Crystallisation of salt by brine evaporation remains an energy consuming technique. No wonder that alternatives to circumvent the evaporation get ample attention. Especially antisolvent crystallisation is extensively studied in a number of papers, ranging from studying crystal growth phenomena (Takiyama, Kaneko) to an economic evaluation of this technique (Zijlema).
Session 3c: Sea/solar salt Session manager: Paul-Andre Capdequi-Peyranère
The production of salt by natural evaporation is a very ancient technical method, perhaps the oldest known to man. Still, research in this field is continued and new methods are found to improve the economy of operation and the quality of the product on one hand and application of new technologies on the other hand.
An example of the latter is the use of the G.P.S. technology to improve and increase the rate of a salt harvesting in Spain. The variety of topics, ranging from the design of an integrated solar salt plant with vacuum salt in India, studies on the uses of the lithium and others secondary salts in Tunesia, the production of MgCl2 salt by mixing of bitterns remaining as residual brines in Egypt, prove that sea-salt is still an active field of technical research. A new concept is growing now. The sea salt plant, from the seawater and its different algae to the bitterns and their extremely halophilic bacteria, is studied as a self-consistent eco-system. Con-tributions on this topic show that the concentration of salt in solar ponds influences the eco-system, but equally important, how the eco-system influences the efficiency and quality of the solar salt operation as a whole.
In that sense one can say "The oldest known is still young".
Session 3d: By product salt Session manager: ChristineTahon
Waste minimisation is a constant objective in the manufacturing industries. This is reflected in this session which reviews several innovative processes to recover salt from various types of effluents: from waste brine and solid waste salt, from co-produced salts in potassium fertiliser plant, from solid effluent of hydrazine manufacturing plant, from municipal solid waste incineration residues and finally from the heavily polluted waters of the Salton sea in California.
In parallel, two interesting presentations are made of processes to convert into a valuable mineral fertiliser respectively the effluents of a thermal evaporation salt plant in Austria and of a seawater solar plant in Venezuela.
Session 3e: Electrodialysis and desalination Session manager: Gerda van Rosmalen
The use of the membrane electrolysis process for the production of chlorine and sodium hydroxide puts very stringent demands on the purity of the salt used for this process. The amounts of bromine and various metals must be extremely low. The purity of the salt used for electrolysis is therefore a prime concern of salt producers world-wide.
Two papers in this session show how the efficiency of the membrane electrolysis is influenced by the impurities in salt. The use of membrane does not only put stringent requirements on the purity of salt used, it offers also new opportunities for the brine purification prior to crystallisation, thus improving the salt purity. This aspect is also treated in a number of papers. When using liquid membranes, host molecules specific to a single ionic species can be used. Two papers in this session give examples how such techniques can be used to purify brine or extract specific ions from brine.
Session 4: Sampling and analysis and salt processing Session manager: Leon Ninane
here is a steady flow of work in analysis: new techniques are emerging like Atomic Force Microscopy, HPLC, IR spectrometry. The study of fluid inclusions is a very active field and these studies are helped by these new techniques. Routine and new techniques are the basis for gaining knowledge on salt and for controlling production in industrial processes. Validation of analytical techniques is described and bring data quality objectives into the analytical chemical laboratories
Properties and production of flake salt have been revisited in the first paper: new multistage crystallizer has been designed, and new superior properties of dissolution, adhesion and mixing are exhibited. Salt processing is described through 3 successive papers: one describes particle destruction in centrifuge, one is concerned with the fluid bed technology for drying salt and the third one with management of risk based inspection Caking of salt at freezing temperatures is studied; this paper describes a method for preventing caking with the help of additives. The last paper describes the effect of carbonate additive to salt as a stabiliser of iodine in the iodised salt.
Session 5: Salt markets and applications Session manager: David Steven
The size and location of the salt market is changing with customers adopting a global perspective to their businesses. Strategic investment decisions are being made based on their view of future demand in both the developed and emerging economies. The location of salt producers and their future production volumes will be strongly influenced by these global decisions. The chlor-alkali industry is a key salt market and the location and size of manufacturing plants is influenced by the geography of their future customer base, variations in the price of energy and the ability to satisfy environmental pressures. Presenters, who are expert in their fields, address these challenges and predict the likely impact upon salt producers.
Salt for road de-icing is a very important large volume market. Customers' cost reduction and environmental improvement agendas have placed pressure on this traditional application. Papers are presented which discuss these issues and provide cost/benefit evidence that business and society are best served by local authorities allocating sufficient resource to provide an effective winter maintenance programme.
Salt is an essential element to a balanced diet and has been used for thousands of years to preserve and add taste to food. However, over recent years, the relationship between salt and blood pressure has been the subject of much controversy. Papers are presented which show the invaluable role of salt within the food industry but, equally important, new scientific work is outlined which confirms the unique qualities of salt as a micronutrient carrier and as a useful component in the disease management of crops.
Session 6 New uses of salt
Session manager: Leon Ninane
For a product known for thousands of years, it is still possible to find new uses for salt, which the purpose of this session Salt as a capsulation agent is described; seeds are prepared then coated with a foreign substance and finally the coated salt is grown. In-depth knowledge of crystallisation process is needed for this new high-tech application. Salt can also be used for covering protection of hay bales. Effect of salt for controlling the development of tropical algea has been investigated brine ponds are also used for accumulation of solar energy; the energy can be used for thermal usage or electricity production.
Session 7 Salt and the environment Session manager: Christine Tahon
Various bacteria live in solar ponds and seriously affect the quality and production rate of salt. Therefore biological management for solving these problems becomes more and more important. Five presentations deal with this topic: One shows that salinas act as depurating systems towards undesirable bacteria, another studies the favourable role of extreme halophilic bacteria in the precipitation of salt. A third one proposes to use diatoms as indicators to determine time-integrated conditions in preference to direct water quality measurement. A fourth study deals with the determination of the halophatic bacteria content of mineral and biological media. The last study presents a biogeochemical model to predict salt behaviour and provides a framework for addressing remediation and potential problems.
Two more fundamental studies are concerned with the survival of halotolerant bacteria: brevibacterium so. JCM 6894 and Halobacterium salinarium.
The other studies in the session are dealing with the management of the production of Artemia cysts, the existence of life in ancient salt sediments mostly in the dormant state and the salt extraction to improve the environment of the salty Lake Qaroun in Egypt.
The next sub-session groups various studies dealing with more general environmental matters: The ecology of the mangroves, of salinas in the Mediterranean and of a polluted bay in southeast Brazil, the influences of deep well injection of waste brine on the envirom-nent in Germany and the long-term behaviour of cement based backfill materials in salt formations.
Session 8: Iodized Salt for Sustaining IDD Elimination Session manager: Frits van der Haar
Science offers many insights from its study of cause and effect. A recent understanding from the integration of available knowledge is that iodine deficiency has multiple consequences on the health, learning ability, productivity and prosperity of individuals, communities and nations. Another key finding from nutritional science is that iodine deficiency threatens the rich and poor of the world alike. The rich cannot consider themselves protected from being in the privileged world. At a recent gathering of public health experts it was reasoned that the 20th Century would be remembered for its indifference about the world's inequity. As we enter the 21st Century, we can no longer distance ourselves from a vision that the future shall be marked by compassion for those who do not enjoy even the minimum conditions to attain their human potential for social and economic development. In the case of the global conquest of iodine deficiency, this is not in the interest of the poor only. It is in the interest of all. Many scientists involved in the global elimination of iodine deficiency disorders have responded to the invitation from the salt industry to be guest at the 8th World Salt Symposium. Their contributions have been conveniently packaged in a section named "Iodized Salt for Sustaining IDD Elimination". The keynote paper for this section by Ramalingaswami, an eminent public health scientist with an experience that encompasses at least half of the past Century, paints the holistic picture of cost to the world arising from continued iodine deficiency. Long ignored, and initially understood for its health impact, the problem of iodine deficiency now has dawned upon the world as the largest preventable cause of countless losses of opportunities from impaired health status, diminished cognitive ability, reduced work performance and, ultimately, stunted development of individuals, communities and nations. While the range and extent of the iodine deficiency disorders were compelling enough for giving it public health priority, we now have learned to consider the iodine deficiency problem and its global solution as a development issue. And the attempts are visible already of a comprehensive approach not only in attacking the condition, but also ensuring that its consequences remain eliminated forever. The basic ingredients for this new approach are contained in the papers for plenary presentation in the session named "An IDD-free World: How to Keep It that Way!". Alnwick presents the growth history of the global alliance of partners that aims at improving the efficient application of the available science. Mannar gives the global overview of the trends, developments and prospects for universal salt iodization. And Haxton contributes a forward-looking view of the new attitudes and operational styles as well as the modern tools for sustaining the elimination of iodine deficiency into our world's future. Tremendous global progress is being made in universal salt iodization. The oral and poster presentations at this Symposium are testimony to the fact that the technical, financial and managerial obstacles to global elimination of iodine deficiency disorders can be overcome. The bold political statements and courageous follow-up actions from the past decade continue to yield the results called for. The agreed-upon guideline for global policy, formulated between the World Health Organization and UNICEF with inputs of the International Council for Control of Iodine Deficiency Disorders, is to "iodize all salt for human and animal consumption, including salt for food processing (Universal Salt Iodization)". This policy is steadfastly being pursued in virtually all countries where iodine deficiency disorders is a priority from public health information. The perspectives from China, by the President of the National Salt Industry, from the Republic of South Africa, the Russian Federation, Zimbabwe and Indonesia are selected examples of the progress in country after country. They are presented in a session entitled "Examples of Success from National Programs". The session on "Markets of Iodized Salt" allows salt producers and investigators from countries as diverse as Bangladesh, Croatia, France, Bulgaria and Nigeria to present and discuss the barriers and opportunities in delivering the product for sale to consumers. The session on "Quality of Iodized Salt" offers a scientific debate on the usefulness of on-the-spot testing of iodized salt for iodine, followed by contributions about the stability of the fortificant potassium iodate in iodized salt, and the assessment of human iodine status after its consumption. The successful application of edible salt as carrier of iodine naturally attracts ideas for other beneficial purposes, i.e. fluoride for caries prevention, iron for addressing iron deficiency and diethylcarbamazine (DEC) for eradicating lymphatic filariasis. The technologies, programmatic approach and scientific investigations are presented in the session entitled "Salt as Vehicle for other Public Health Efforts". A capstone for this section in the Symposium is composed of contributions from recent gatherings and actions by salt producers and salt traders in a number of world regions. After it was realized that not all salt producers of the world would be able to afford to attend at Salt2000, a coalition of partner organizations from November 1998 onwards has collaboratively promoted the holding of regional salt suppliers' meetings in preparation of the 8th World Salt Symposium. These meetings aimed to take stock of regional progress made, discuss and agree on ways to reach universal application and prepare a regional plan
