IPPC BAT REFERENCE DOCUMENT LARGE VOLUME SOLID INORGANIC CHEMICALS FAMILY PROCESS BREF FOR SODA ASH

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1 EUROPEAN CHEMICAL INDUSTRY COUNCIL IPPC BAT REFERENCE DOCUMENT LARGE VOLUME SOLID INORGANIC CHEMICALS FAMILY PROCESS BREF FOR SODA ASH ESAPA European Soda Ash Producers Association Issue N : 3 Date of issue: March 2004 Document approved by ESAPA

2 Soda Ash Process BREF - Issue N 3 March

3 PROCESS BREF FOR SODA ASH TABLE OF CONTENTS PREFACE... 8 DEFINITIONS GENERAL INFORMATION HISTORY OF THE PRODUCTION OVERVIEW ABOUT TYPE OF PRODUCTION Solvay process Trona and nahcolite based process Trona Nahcolite Nepheline syenite process Carbonation of caustic soda USES IN INDUSTRIAL SECTORS Glass industry Detergent industry Steel industry Non-ferrous metallurgy industry Chemical industry Sodium bicarbonate Sodium sesquicarbonate Chemically pure sodium carbonate Sodium bichromate Sodium percarbonate Sodium phosphates Sodium silicates Sodium sulfites Other applications PRODUCTION CAPACITY IN THE WORLD AND IN EUROPE Worldwide European Union SOCIO-ECONOMICAL ASPECTS Main characteristics of the industry Social integration - employment General economic standing Environmental taxes and levies Manufacturing and operating cost APPLIED PROCESS AND TECHNIQUES PROCESS Main chemical reactions Process steps Brine purification Soda Ash Process BREF - Issue N 3 March

4 Lime kilns and milk of lime production Absorption of ammonia Precipitation of sodium bicarbonate Separation of sodium bicarbonate from mother liquid Sodium bicarbonate calcination Ammonia recovery Product storage and handling RAW MATERIALS Brine Typical composition Storage Limestone Carbon for the lime kiln Typical composition Storage Ammonia Characteristics Storage Miscellaneous additives MAIN OUTPUT STREAMS POSSIBILITIES FOR PROCESS OPTIMIZATION AND IMPROVEMENTS Purity of raw materials Raw material consumptions Energy PRESENT INPUT/OUTPUT LEVELS RAW MATERIALS UTILITIES Steam Process water Cooling waters Electricity GASEOUS EFFLUENTS Particulate dust Carbon dioxide and monoxide Nitrogen oxides Sulfur oxides Ammonia Hydrogen sulfide LIQUID EFFLUENTS Wastewater from distillation Wastewater from brine purification SOLID EFFLUENTS Fines of limestone Non recycled stone grits at slaker CO-PRODUCTS Calcium chloride Refined sodium bicarbonate Background information Soda Ash Process BREF - Issue N 3 March

5 Process description Major environmental impact CANDIDATE BEST AVAILABLE TECHNIQUES ENVIRONMENTAL ASPECTS ENERGY MANAGEMENT Energy conversion of primary fuels Energy saving in the process Heat recovery Energy minimisation GASEOUS EFFLUENTS MANAGEMENT Calcination of limestone Precipitation of crude sodium bicarbonate Filtration of the bicarbonate Production of dense soda ash Conveying and storage of light and dense soda ash LIQUID EFFLUENT MANAGEMENT Liquid effluent treatments Marine outfalls Lake and river discharge Settling ponds Purpose and principles Operation of settling basins Monitoring during operation Hydraulic confinement Coverage and final closure Underground disposal Liquid effluent discharge management Concept of equalisation in modulation basins Performance Available techniques Management of equalization basins Adjustment of ph By-products recovery and reuse Dissolved CaCl 2 in distillation wastewater Suspended solids in distillation wastewater Product from brine purification SOLID MATERIALS MANAGEMENT Limestone fines Grits from slaker BEST AVAILABLE TECHNIQUES FOR THE MANUFACTURING OF SODA ASH INTRODUCTION CONSIDERATION TO BE TAKEN INTO ACCOUNT WHEN DETERMINING BAT FOR THE MANUFACTURING OF SODA ASH EMISSION TO WATER Ammonia Suspended solids Soda Ash Process BREF - Issue N 3 March

6 5.4. EMISSION TO AIR Lime kilns gas Quantity of lime kiln gas produced Composition of lime kiln gas Gas effluent of the manufacturing sector Dust ENERGY Heat recovery Energy minimisation REFERENCES Soda Ash Process BREF - Issue N 3 March

7 PROCESS BREF FOR SODA ASH LIST OF TABLES Table 1 Worldwide capacity of soda ash manufacture (reference year : 2000) Table 2 European soda ash capacity and producers (reference year : 2002) Table 3 Soda ash manufacturing costs Table 4 Plant area/operations Table 5 Raw and purified brines (typical composition ranges) Table 6 Coke for lime kilns (typical composition ranges) Table 7 Main output streams from the soda ash process Table 8 Soda ash process major Input/Output levels Table 9 Wastewater from distillation Table 10 Effluent from brine purification (typical composition) Table 11 Solid effluents from soda ash process Table 12 Worldwide Refined Sodium Bicarbonate Annual Capacities (reference year : 2002) Table 13 Consumption of Refined Sodium Bicarbonate in EU (reference year : 2002) Table 14 European Refined Sodium Bicarbonate capacity and producers (reference year : 2002) Table 15 Vent gas from bicarbonation columns blown with lime kiln gas Table 16 Vent gas from lime kilns after cleaning Table 17 Vent gas from column section after washing Table 18 Filter gas after washing Table 19 Typical gas composition resulting of limestone calcination Table 20 Vent gas from column section after washing Table 21 Ranges of energy consumption LIST OF FIGURES Figure 1 Geographic distribution of soda ash plants (Solvay process) within the European Union (2002) Figure 2 Process block diagram for the manufacture of soda ash by the Solvay process Figure 3 Process block diagram for the manufacture of refined sodium bicarbonate.. 49 Soda Ash Process BREF - Issue N 3 March

8 PREFACE The European Soda Ash Producers Association (ESAPA), through CEFIC, has produced this Best Practice Reference Document (BREF) in response to the EU Directive on Integrated Pollution Prevention and Control (IPPC Directive). The document was prepared by technical experts from the ESAPA member companies and covers primarily the production of soda ash (sodium carbonate) by the Solvay Ammonia-Soda process. This BREF reflects industry perceptions of what techniques are generally considered to be feasible and presently available and achievable emission levels associated with the manufacturing of soda ash. It does not aim to create an exhaustive list of Best Available Techniques (BAT) but highlights the most widely used and accepted practices. The document uses the same definition of BAT as that given in the IPPC Directive 96/61 EC of BAT covers both the technology used and the management practices necessary to operate a plant efficiently and safely. The principles of Responsible Care to which the companies voluntarily adhere provide a good framework for the implementation of management techniques. The BREF is focused primarily on the technological processes, since good management is considered to be independent of the process route. It should be noted that different practices have developed over time, dependant upon national and local regulatory requirements, differences in plant location and issues of local environmental sensitivity. This has resulted in differences in best practices between EU Member States. Moreover certain practices may be mutually exclusive and it must no be assumed that all achievable minima can be met by all operations at the same time. Neither CEFIC, ESAPA nor any individual company can accept liability for accident or loss attributable to the use of the information provided in this document Soda Ash Process BREF - Issue N 3 March

9 DEFINITIONS The following definitions are taken from Council directive 96/61/EC of 1996 on Integrated Pollution Prevention and Control: Best Available Techniques shall mean the most effective and advanced stage in the development of activities and their methods of operation which indicate the practical suitability of particular techniques for providing, in principle, the basis for emission limit values designed to prevent or, where that is not practicable, generally to reduce emissions and the impact on the environment as a whole: "Techniques" include both the technology used and the way in which the installation is designed, built, maintained, operated and decommissioned. Available techniques shall mean those developed on a scale which allows implementation in the relevant industrial sector, under economically and technically viable conditions, taking into consideration the costs and advantages, whether or not the techniques are used or produced inside the Member State in question, as long as they are reasonably accessible to the operator. Best shall mean most effective in achieving a high general level of protection for the environment as a whole. Soda Ash Process BREF - Issue N 3 March

10 1. GENERAL INFORMATION 1.1. HISTORY OF THE PRODUCTION Before the advent of industrial processes, sodium carbonate, often-called soda ash, came from natural sources, either vegetable or mineral. Soda made from ashes of certain plants or seaweed has been known since antiquity. At the end of the 18 th century, available production was far below the growing demand due to the soap and glass market. The French Academy of Science offered an award for the invention of a practical process to manufacture soda ash. Nicolas Leblanc proposed a process starting from common salt and obtained a patent in The so-called Leblanc or black ash process was developed in the period 1825 till The major drawback of this process was its environmental impact with the emission of large quantities of HCl gas and the production of calcium sulfide solid waste which not only lost valuable sulfur but also produced poisonous gases. In 1861, Ernest Solvay rediscovered and perfected the process based on common salt, limestone and ammonia. Competition between both processes lasted many years, but relative simplicity, reduced operating costs and, above all, reduced environmental impact of the Solvay process ensured its success. From 1885 on, Leblanc production took a downward curve as did soda ash price and by the First World War, Leblanc soda ash production practically disappeared. Since then, the only production process used in Western Europe as well as in main part of the world is the Solvay process. In the meantime and mainly since the twenties, several deposits of minerals containing sodium carbonate or bicarbonate have been discovered. Nevertheless the ore purity and the location of these deposits, as well as the mining conditions of these minerals, has limited the effective number of plants put into operation. Soda Ash Process BREF - Issue N 3 March

11 1.2. OVERVIEW ABOUT TYPE OF PRODUCTION Solvay process The Solvay process, also called ammonia soda process, uses salt (NaCl) and limestone (CaCO 3 ) as raw materials. Ammonia, which is also used in the process, is almost totally regenerated and recycled. The main advantage of this process is the availability of the raw materials, which can be found almost everywhere in the world and therefore allows operating production units relatively close to the market. The Solvay process produces light soda ash, with a specific weight or pouring density of about 500 kg/m3. It is used in that form mainly for the detergent market and certain chemical intermediates. Light soda ash is transformed by recrystallization firstly to sodium carbonate monohydrate, and finally to dense soda ash after drying (dehydration). Dense soda ash has a pouring density of about 1000 kg/m3. It is used mainly in the glass industry. Dense soda ash can also be produced by compaction. Some producers have made several modifications to the original process. The main ones are: - the dual process, which allows production units to co-produce in nearly equal quantities ammonium chloride, which is used as a fertilizer in rice cultivation. There are several plants in the world which are working with that process. Most are situated in China - the Akzo or dry lime process, which uses dry lime instead of lime milk for ammonia recovery Trona and nahcolite based process All processes are based on ore treatment from which impurities (i.e. organics and insolubles) have to be stored underground or in tailing ponds Trona Trona minerals can be found underground (Green River trona deposit in Wyoming - USA, Inner Mongolia - China, Henan - China) or in dry lakes (Searles Lake trona brine deposit in California USA, Magadi Lake trona brine deposit in Kenya, Sua Pan trona brine deposit in Botswana). Soda Ash Process BREF - Issue N 3 March

12 Underground "dry" trona processing consists in several steps: - mechanical mining by the room and pillar or long wall method - as trona is an impure sodium sesquicarbonate mineral (Na 2 CO 3 NaHCO 3 2H 2 O), it has firstly to be calcined to produce a soda ash still containing all the impurities from the ore - next, calcined trona is dissolved, the solution is settled and filtered to remove impurities (insolubles and organics) - the purified liquor is sent to evaporators where sodium monohydrate crystals precipitate - the monohydrate slurry is concentrated in centrifuges before drying and transformation into dense soda ash Deposits from trona lakes and solution mined trona are processed as follows : - dissolving trona in wells - carbonation of the solution in order to precipitate sodium bicarbonate - filtration of the slurry - calcination of the bicarbonate to get light soda ash, recycling of the carbon dioxide to the carbonation - light soda ash transformation into dense by the monohydrate method - carbon dioxide make-up produced by burner off-gas enrichment Nahcolite A Nahcolite deposit has been found in Piceance Creek in Colorado - USA and an industrial soda ash plant has been put into operation at the end of the year Little practical experience of this process is therefore available. Nahcolite is processed as follows: - by solution mining (wells, with injection of hot mother liquor returned from the surface facilities) - as nahcolite is an impure sodium bicarbonate mineral (NaHCO 3 ), it must be treated - the hot solution is decarbonated by heating - the solution is sent to settling and filtration. - next, the purified liquor is sent to evaporators where sodium monohydrate precipitates - the slurry is concentrated by centrifugation and the monohydrate crystals transformed to soda ash by drying - the mother liquor is sent back to the solution mining Soda Ash Process BREF - Issue N 3 March

13 Nepheline syenite process There is still a process operated in Russia, mainly in a plant situated in Siberia, which uses mixed minerals and allows the coproduction of alumina, cement and soda ash. The soda ash produced is of poor quality Carbonation of caustic soda Small quantities of soda ash are made by the carbonation of caustic soda. This produces a soda liquor solution which is treated in similar ways to those described above. Alternatively where this caustic soda is from diaphragm cells it contains high levels of residual sodium chloride which can be used either in conjunction with a conventional Solvay ammonia soda process or in the brine purification process USES IN INDUSTRIAL SECTORS Soda ash is a commodity chemical used in several branches of industry. The main ones are quoted in the following paragraphs Glass industry Soda ash is used in the manufacturing of flat and container glass. Acting as a network modifier or fluxing agent, it allows lowering the melting temperature of sand and therefore reduces the energy consumption Detergent industry Soda ash is used in a large number of prepared domestic products: soaps, scouring powders, soaking and washing powders containing varying proportions of sodium carbonate, where the soda ash acts primarily as a builder or water softener Steel industry Soda ash is used as a flux, a desulfurizer, dephosphorizer and denitrider. Soda Ash Process BREF - Issue N 3 March

14 Non-ferrous metallurgy industry - treatment of uranium ores - oxidizing calcination of chrome ore - lead recycling from discarded batteries - recycling of zinc, aluminium Chemical industry Soda ash is used in a large number of chemical reactions to produce organic or inorganic compounds used in very different applications Sodium bicarbonate - animal feeds to balance their diets to compensate for seasonal variations and meet specific biological and rearing needs - paper industry for paper sizing - plastic foaming - water treatment - leather treatment - flue gas treatment, especially in incinerators - detergent and cleaning products such as washing powders and liquids, dishwashing products, etc - drilling mud to improve fluidity - fire extinguisher powder - human food products and domestic uses : baking soda, effervescent drinks, toothpaste, fruit cleaning, personal hygiene, etc - pharmaceutical applications : effervescent tablets, haemodialysis Sodium sesquicarbonate - bath salts, water softener Chemically pure sodium carbonate - pharmaceuticals industry, cosmetics, food industry and fine chemicals Soda Ash Process BREF - Issue N 3 March

15 Sodium bichromate Sodium percarbonate - bleaching agent for various fabrics and constituent of domestic detergent powders - cosmetology Sodium phosphates Sodium silicates Sodium sulfites Other applications - production of various chemical fertilizers - production of artificial sodium bentonites or activated bentonites - manufacture of synthetic detergents - organic and inorganic coloring industry - enamelling industry - petroleum industry - fats, glue and gelatine industry, etc PRODUCTION CAPACITY IN THE WORLD AND IN EUROPE Worldwide The current worldwide soda ash nameplate capacity is estimated to be around 42 million t/year. The split between processes and geographical zones is given in Table 1. Soda Ash Process BREF - Issue N 3 March

16 Table 1 Worldwide capacity of soda ash manufacture (reference year : 2000) Production capacity EU25 Rest of Europe North. America Latin America Asia Africa Oceania Total million t/year Solvay process Na minerals process Others Total European Union There are only four producers in the European Union (EU15) applying the Solvay process: Solvay, Brunner Mond, Novacarb, Sodawerk Stassfurt, with a total capacity of 6625 kt/year. BASF has two plants which co-produce sodium carbonate with a combined capacity of 65 kt/year. Solvay has 7 plants situated in 6 countries: France, Germany, Italy, Spain, Portugal and Austria with a total capacity of 4200 kt/year. Brunner Mond has 3 plants in 2 countries: United Kingdom and Netherlands with a total capacity of 1375 kt/year. Novacarb has one plant, in France, with a capacity of 600 kt/year. Sodawerk Stassfurt has one plant, in Germany, with a capacity of 450 kt/year. The enlarged European Union (EU25) will take in two additional plants in Poland operated by Ciech with a combined capacity of (1100 kt/year) already member of ESAPA. ESAPA also represents the Turkish operation of Şişecam (800 kt/year) and the Bulgarian factory (1200 kt/year) operated as a production joint venture between Solvay (75%) and Şişecam (25%) and the two Romanian factories operated by Bega with a combined capacity of (710 kt/year). These give a combined additional production capacity of 3810 kt/year. Soda Ash Process BREF - Issue N 3 March

17 Table 2 European soda ash capacity and producers (reference year : 2002) Producers Country - location Capacity (kt/year) Plant start-up (*) Solvay France Dombasle Germany Rheinberg Germany Bernburg Spain Torrelavega Italy Rosignano Portugal Povoa Austria Ebensee Solvay - Şişecam Bulgaria Devnya Brunner Mond United Kingdom Northwich (Winnington/Lostock) The Netherlands Delfzijl Novacarb France - La Madeleine Sodawerk Stassfurt Germany Stassfurt Ciech Janikosoda Poland Janikowo Ciech Soda Matwy Poland Inowroclaw Soda Sanayii Turkey Mersin Bega Govora Romania Govora Bega Upsom Romania Ocna Mures Sodaso Bosnia Herzegovina BASF (*) Obviously, all these plants have been revamped several times in order to implement technology upgrade and plant capacity has been increased progressively to follow market demand. Production sites in the European Union are shown on a map in Figure 1. Soda Ash Process BREF - Issue N 3 March

18 Northwich (2) Delfzijl Inowroclaw Stassfurt Rheinberg Janikowo Bernburg Torrelavega Dombasle La Madeleine Ebensee Rosignano Lukavac Ocna Mures Govora Devnya Povoa Mersin Figure 1 Geographic distribution of soda ash plants (Solvay process) within the European Union (2002) Soda Ash Process BREF - Issue N 3 March

19 1.5. SOCIO-ECONOMICAL ASPECTS Main characteristics of the industry Soda ash is a chemical product of the inorganic commodity family. As one of the major raw materials of the chemical and glass industry, it is also of strategic importance for the industrial framework in the world and especially in Europe. The estimated invested capital necessary to build a new soda ash plant in the EU is very high : about 600 /t of annual capacity (excluding the cost of steam and power plant). The current economic situation could not justify the construction of new plants and for many years producers have been progressively revitalizing and modernizing existing plants Social integration - employment The total number of people employed directly by the European producers (EU25) is estimated at 8500 persons (or about 900 t per person employed per year). These numbers will of course depend upon the boundary of operation and will therefore vary from site to site. Furthermore, there are a certain number of subcontractors working in the plants on activities such as bagging, loading, transport, engineering, construction, maintenance, which can be estimated to persons. In Western Europe it is estimated that about are employed, directly and indirectly, in the production of soda ash and direct derivatives General economic standing Since the end of the eighties, the progressive opening of the borders, the reduction of trade barriers and the reduction of transportation costs have created very competitive conditions in the soda ash business to the point where today this market can be considered as worldwide and predominantly commodity. The European Union soda ash industry has suffered severely from these changes. In the last ten years, five plants shut down: three in Germany, one in France and one in Belgium. Constant efforts have been made by the European soda ash industry to improve its competitiveness in order to resist cheap Eastern Europe and US imports. The soda ash industry in these other regions is favoured by lower energy costs both for natural gas and electricity. Soda Ash Process BREF - Issue N 3 March

20 Total manpower costs in the EU are, in general, significantly higher than in the US and than in Eastern Europe. At the beginning of the twenty-first century, the European soda ash industry is still being challenged by US and Eastern Europe imports Environmental taxes and levies There is no consistent picture throughout Europe on Environmental Taxes or Levies. In the UK the majority of the costs are associated with maintenance of existing authorisations where as in other member states the emphasis is on taxes for specific discharges to water, or emissions to atmosphere. As for other industries, a number of taxes and levies are imposed on producers, such as social or environmental fees. The soda ash sector is especially sensitive to those when they are based on occupied surface, water consumption or energy inputs/outputs and emission. In some countries, the total amount of taxes and levies, including local taxes, energy, mining, housing, training, properties are as high as 6.4 /t soda ash Manufacturing and operating cost Exact Figures for production costs are obviously confidential. A rough existing indication provided by consultants is given in Table 3. These data have to be considered carefully since operating costs will vary depending on the production location. Table 3 Soda ash manufacturing costs Item Cost [ /t soda ash] Raw materials 25 Energy 40 Labour 35 Maintenance 20 Total (cash costs) 120 Soda Ash Process BREF - Issue N 3 March

21 The actual cost will vary according to a number of factors including location and ownership of raw materials, energy sources etc. 2. APPLIED PROCESS AND TECHNIQUES 2.1. PROCESS Main chemical reactions The SOLVAY process relative to the production of soda ash could be summarized by the theoretical global equation involving the two main components: sodium chloride and calcium carbonate. 2 NaCl + CaCO 3 Na 2 CO 3 + CaCl 2 In practice this direct way is not possible and it needs the participation of other substances and many different process steps to get the final product: soda ash. First reactions occur in salt solution (brine). First of all, ammonia is absorbed (1) and then, the ammoniated brine is reacted with carbon dioxide to form successive intermediate compounds: ammonium carbonate (2) then ammonium bicarbonate (3). By continuing carbon dioxide injection and cooling the solution, precipitation of sodium bicarbonate is achieved and ammonium chloride is formed (4). Chemical reactions relative to different steps of the process are written below: NaCl + H 2 O + NH 3 NaCl + NH 4 OH (1) 2 NH 4 OH + CO 2 (NH 4 ) 2 CO 3 + H 2 O (2) (NH 4 ) 2 CO 3 + CO 2 + H 2 O 2 NH 4 HCO 3 (3) 2 NH 4 HCO NaCl 2 NaHCO NH 4 Cl (4) Sodium bicarbonate crystals are separated from the mother liquor by filtration, then sodium bicarbonate is decomposed thermally into sodium carbonate, water and carbon dioxide (5). 2 NaHCO 3 Na 2 CO 3 + H 2 O + CO 2 (5) CO 2 is recovered in the carbonation step (see equations 2 and 3 above). CO 2 recovery cycle is shown in Figure 2. Soda Ash Process BREF - Issue N 3 March

22 Mother liquor is treated to recover ammonia. The ammonium chloride filtrate (4) is reacted with alkali, generally milk of lime (6), followed by steam stripping to recover free gaseous ammonia: 2 NH 4 Cl + Ca(OH) 2 CaCl NH H 2 O (6) NH 3 is recycled to the absorption step (see equation 1 above). Ammonia recovery cycle is shown in Figure 2. Carbon dioxide and calcium hydroxide originate from limestone calcination (7) followed by calcium oxide hydration (8). CaCO 3 CaO + CO 2 (7) CaO + H 2 O Ca(OH) 2 (8) Brine (NaCl) has to be treated before the input in the process to remove impurities : calcium and magnesium. If not removed they would react with alkali and carbon dioxide to produce insoluble salts contributing to scale formation inside equipment. Brine purification reactions are described in the following equations: Ca 2+ + CO 3 2- CaCO 3 (9) Mg OH - Mg(OH) 2 (10) Sodium carbonate formed (equation 5) is called "light soda ash" because its bulk density is approximately 0.5 t/m3. A subsequent operation called densification enables this value to be doubled by crystallisation into sodium monohydrate, by adding water (equation 11) then followed by drying (equation 12). Final product is "dense soda". Na 2 CO 3 + H 2 O > Na 2 CO 3.H 2 O (11) Na 2 CO 3.H 2 O > Na 2 CO 3 + H 2 O (12) Process steps The SOLVAY process has been described in details in several recognized references (see chapter 6). Chemical reactions described in are realized industrially in different areas illustrated in the block diagram of Figure 2. Soda Ash Process BREF - Issue N 3 March

23 GO1 vent or recovery for bicarbonate production LIMESTONE screening of the limestone fines GO4 SO1 water vapor water fines containing inert material lime SO2 washing of the gas calcination lime kilns slaking of the lime lime milk CARBON (COKE, ) NH3 CO2 unburnt limestone water NH3 make up ammonia recovery cycle LO3 bis washing and cooling RAW BRINE brine purification NH3 absorption carbonation of ammoniated brine air reagents LO3 LO1 wastewater with salt impurities (CaCO3, Mg(OH)2 ) GI2 gas washing with purified brine water cooling LO4 CO2 gas GO2 energy gas compression steam recovery of ammonia filtration CO 2 recovery cycle wastewater LI2 GI3 LO2 treatment of the wastewater calcination of crude bicarbonate gas cooling and washing with purified brine GO6 GO3 GO5 water vapor gas washing with purified brine vacuum pumps washer condenser energy GI5 monohydratation of the light soda ash drying of the monohydrate water dedusting storage of light soda ash dedusting GO7 storage of dense soda ash LIGHT SODA ASH DENSE SODA ASH energy LEGEND process optional operation solid liquid liquids gaseous streams XXX GI, GO LI, LO SI, SO = Gaseous, Liquid, Solid streams Inlets/Outlets raw materials, end products Figure 2 Process block diagram for the manufacture of soda ash by the Solvay process Soda Ash Process BREF - Issue N 3 March