17.1.1 The Importance of Phosphate Process Optimization from Mine to Market
The Importance of Phosphate Process Optimization from Mine to Market
Todd Parker - ArrMaz

Phosphate is a non-renewable resource and must be managed accordingly. Understanding the phosphate industry from beginning to end is the key to unlocking the true potential of phosphate ore to produce superior quality fertilizer sustainably and cost-effectively. Describing 10 key practices for better rock processing to improve grade and recovery thereby creating a more valuable rock and better feed stock for fertilizer plants, enabling them to produce higher value fertilizer. Better quality fertilizer in turn delivers greater benefits to farmers, improving crop yields, livestock nutrition and food quality to meet the needs of a growing global population. Mining chemicals and fertilizer process aids are essential to creating such value throughout the phosphate fertilizer supply chain.
Last updated: 2017-05-05

17.1.2 Quality Parameters in Crystallization
Quality Parameters in Crystallization
Sven Hanselmann - Ekato

Crystallization is a wide spread process step in many applications like food, chemicals, APIs or fertilizers. There are three main routes to form solids by crystallization

1. cooling
2. evaporation
3. precipitation

Depending on the applicable route, the mode of operation is either batch wise or continuous.

This paper will focus on the relevant quality parameters in crystallization. It is demonstrating by examples how to control formation of solids by optimized process conditions, i.e. cooling/evaporation strategy, seeding of crystals and vessel design as well as the influence of agitation.

In an optimized system the particle size distribution can be narrowed and the impact on the crystals, e.g. breakage or the production of fines will be reduced. This offers additional benefits in downstream process steps like filtration, drying or packing. The filters’ design can be simplified and the flow behaviour will be improved.

Examples like improved flow patterns in a draft tube baffled crystallizer or shear reduced mixing systems will be described and are supported by lab test results and computational fluid dynamic (CFD) simulations.

Last updated: 2017-05-05

17.1.3 Mosaic New Wales MicroEssentials Conversion
Mosaic New Wales MicroEssentials Conversion
Doug Belle - Hatch, TBD - Mosaic

Mosaic is the world’s leading producer and marketer of concentrated phosphate and potash fertilizer products. In 2013, Mosaic identified a project that would provide the additional production capacity needed to meet increased market demand for Mosaic’s patented MicroEssentials (MES) Products. Mosaic selected Hatch to provide full Engineering, Procurement and Construction Management (EPCm) services for the New Wales MicroEssentials Project. The project included the conversion of an existing dual train (East and West) Di-Ammonium Phosphate (DAP) Plant to MES and Granular Mono-Ammonium Phosphate (MAP) Production. The scope of work for this project included the installation of new closed circuit scrubbing systems, modifications to the recycle system to increase capacity, new ammonia vaporizers, new 65,000 ton product warehouse with automatic re-claimer, new sulfur pit with molten sulfur transfer systems and the facilities for the unloading, storage and pneumatic conveying of micro-nutrient raw materials for the production of MES products. The Hatch Tampa, Florida Office worked together with Mosaic and executed Front End Loading (FEL) 2-Pre-Feasibility, 3-Feasibility, 4-Detailed Engineering and provided Procurement, Construction Management and Commissioning Services for this multi-million USD Capital Project. This paper will present the overall scope of work for the project and discuss the challenges related to the engineering and construction of a heavy brown-field granulation plant project.
Last updated: 2017-05-05

17.1.4 Maximizing P2O5 Effects from Di-Hydrate
Maximizing P2O5 Effects from Di-Hydrate
James Byrd, Elton Curran - Jacobs

Phosphoric Acid plants are benchmarked by production and yield, typically in terms of P2O5. Production has been the benchmark, but as the industry evolves and economics tighten the importance of yield is becoming more pronounced. Yield, also referenced in terms of recovery or losses, is a complex evaluation when studied in detail. Often, yield across the filter, typically quoted by licensors, is confused with yield across the plant. The latter is more appropriately termed Global Recovery and can be complex both in measurement and in control. Global Recovery is simply the difference between P2O5 fed to a reactor and P2O5 produced in terms of phosphoric acid. The losses across the filter are relatively easy to measure, but accounts for only a fraction of Global Recovery. The differential can be substantial and in some cases can be larger than filter losses. This differential is often termed mechanical losses and can result from shut downs, wash downs, equipment malfunctions and other miscellaneous operational factors. There are proven methods to mitigate mechanical losses in the plant as well as losses across the filter. This paper will discuss such methodologies for both existing and conceptual facilities.
Last updated: 2017-05-05

17.1.5 Phosphorus Removal & Recovery from Enhanced Biological Phosporus Removal Sludge
Phosphorus Removal & Recovery from Enhanced Biological Phosporus Removal Sludge
Nadezhda Zalivina, Maraida Balaguer-Barbosa, Andres Garcia Parra, Sarina Ergas - University of South Florida, Luke Mulford, Public Utilities Department, Hillsborough County.

Excess phosphorus in surface waters causes algal blooms and consequent eutrophication. One of the sources of phosphorus is wastewater effluent. Therefore, prior to discharge, phosphorus should be removed from the wastewater. At the same time, phosphorus is a limited resource and phosphate mining is a
very energy intensive process, which has negative impacts on the environment.

Enhanced Biological Phosphorus Removal (EBPR) is a popular wastewater treatment process worldwide. During EBPR phosphorus is taken up by polyphosphate accumulating microorganisms, stored inside their cells and subsequently removed from the wastewater with the waste activated sludge. The anaerobic digestion of the sludge is used for bioenergy recovery in the form of methane, which makes the wastewater treatment process more energy efficient. However, during the digestion of EBPR sludge, stored polyphosphates are released and carried in a sidestream. Sidestreams are typically recycled back to the head of a treatment plant, thus, making the treatment process highly inefficient (increased treatment costs). One successful option for phosphorus removal and recovery is struvite precipitation. Struvite (MgNH4PO4) is a mineral that can be used as a substitute for phosphate fertilizer, thus, generating a possible revenue for wastewater treatment plants. In addition, struvite is a slow release fertilizer, which application reduces non-point sources of pollution. Currently, there is a lack of information about struvite precipitation from sidestreams produced during the digestion of EBPR sludge.

A thermophilic anaerobic digester with the working volume of 24 liters (L) and hydraulic residence time of 12 days was operated in the lab at the working temperature of 55±2°C. The digester was fed three times a week with EBPR sludge from the Falkenburg Advanced Wastewater Treatment Plant (Brandon, Florida). The sidestream containing high concentrations of phosphorus as well as nitrogen was used as an influent for the 4-L fluidized bed reactor used for struvite precipitation. Prior to as well as after the precipitation, the sidestream was centrifuged to remove the solids. The sidestream was seeded with some commercially produced struvite seed from Ostara® and its pH was raised to 8.5 by 2N NaOH addition. If necessary, magnesium salt was also added based on the stoichiometric ratio Mg:NH4:PO4 (1.3:1:1).

The preliminary results showed a substantial phosphorus removal (95-99%) as well as a significant removal of nitrogen (25%) from the sidestream. This indicates that struvite precipitation can help reduce the impact of phosphorus on the environment as well as generate a revenue stream for the wastewater treatment plants which can offset some of the operating costs. A side benefit of
phosphorus recovery is nitrogen recovery. Struvite precipitation can decrease the concentration of nitrogen recycled back with the sidestream, which reduces energy and chemical requirements.

Last updated: 2017-05-05

17.1.6 Phosacid Storage Tanks: Why do they build up with solids?
Phosacid Storage Tanks: Why do they build up with solids?
Todd Hutchinson - Philadelphia Mixing Solutions Ltd.,

Phosacid Storage tank agitators are typically sized for off-bottom solids suspension. Customers have reported that this design requires the tanks to be cleaned out every 6-12 months. Cleaning can involve days to remove the solids and often results in damaged tank linings requiring repairs.

We have found sizing for solids suspension is not the only requirement that needs to be taken into account. There are heat transfer effects that, if not addressed, allow for gypsum formation on the walls. Over time the large formations break off and fall to the floor. In some cases the build-up was enough to damage the agitator.

This presentation will discuss how to solve for this wall build-up allowing for much longer time between inspections.

Last updated: 2017-05-05

17.1.7 Importance of Bubble Size Distribution in Modeling in Gas-Liquid Stirred Vessels
Importance of Bubble Size Distribution in Modeling in Gas-Liquid Stirred Vessels
Ravindra Aglave - Siemens/CD-Adapco

Gas-liquid systems form a key component many chemical industry processes. In such systems, the knowledge of gas volume fraction, its distribution and its eventual effect on mass transfer and reactions is absolutely essential. Experimental measurements have allowed to look in to such systems to a good level of details, resulting in to generation of correlations. These correlations are commonly used in the design process. However, they are very much limited to the size, type and character of the lab or pilot scale system from which they were created. This leaves process engineers with a task of ascertaining if a particular design will meet all the process conditions or not. CFD simulations have allowed process engineers to look at plant scale designs due to the ability to investigate them virtually using computer models.
In many such models, certain assumptions are made. As more research and numerical techniques are developed, these assumptions are relaxed to gain more accuracy. In gas liquid flows, it is commonly assumed that the bubble sizes are uniform or have a mean value. However in reality, there is a varying size of bubbles. This assumption can introduce large error in the calculation of gas volume fraction. Moreover, it can give a misrepresentation of the distribution as well. This means there could be area where the gas volume fraction could be critically lower than process requirement, destabilizing the process or even an unsafe condition. In this paper we present the results from a simpler method, known as S-gamma model, which accounts for coalescence and break up of bubbles and uses only a distribution function.
Last updated: 2017-05-05

17.1.8 Reduction of Phosphogypsum by Optimizing Final Product Mix
Reduction of Phosphogypsum by Optimizing Final Product Mix
Curtis Griffin - PegasusTSI

The production of wet phosphoric acid generates 5 tons of phosphogypsum per ton P2O5. Phosphogypsum refers to the gypsum formed as a by-product of the production of fertilizer from phosphate rock. Phosphogypsum is mainly composed of gypsum (CaSO4·2H2O). Although gypsum is a widely used material in the construction industry, phosphogypsum is usually not used, but is stored indefinitely because of its weak radioactivity. The US EPA has banned all applications of phosphogypsum due to the low radiation levels. The storage and handling of phosphogypsum is very expensive and eventually additional land is required for new stacking.
The ability to reduce the amount of phosphogypsum produced per ton of P2O5 can result in reduced costs and extended stack life. This paper will show how final product mix can reduce the amount of phosphogypsum produced. Products such as Single Super Phosphate (SSP), Dicalcium Phosphate and Monocalcium Phosphate from Hydrochloric Acid (HCL), Granulated Triple Superphosphate (GTSP), lower grade Monoammonium Phosphate (MAP) and addition products can reduce the amount of gypsum produced or in some cases eliminate phosphogypsum production all together.
The various products mentioned above and others will be discussed, basic flow sheets will be reviewed and the reduction in phosphogypsum per ton of P2O5 will be shown. The impact on costs and stack life will also be evaluated.
Last updated: 2017-05-05