Best Practices for Solid Sulphur Handling Dust Mitigation and Control
What causes dust generation? Contaminated feedstock – problems at the SRU. • Forming plant product quality – SUDIC and temperature. • Handling before storage. • Stockpile management. • Caking. • Segregation. • Dead storage (FIFO). • Reclaim methodology. • Downstream handling systems. • Ship/rail loading systems. •
How can we manage dust formation? Understanding the impact of contamination, catalysts & temperature. SRU operations and maintenance. • Leaks. • Operating off-specification. • H2S and degassing. • Catalysts. • High H2S content. • Temperature. • Polymeric content/thermal history. • Effect on forming process. •
How can we manage dust formation? Optimizing forming plant operation. What is expected of the forming plant? What is measured on a daily basis? Quantity before quality? • Quality management program in place? • Understanding the definition of quality • Sampling and testing • Maintaining records and sharing results • Product discharge temperatures • Hot product = caking in storage • Caking = reclaim issues and product damage •
What is ‘forming’? • (verb) …to give form or shape to, to make or produce… • Wet Prill • Pastilles • Granules
Why forming? Dust reduction. • Improved handling properties. • Consistent bulk density. • Optimum remelting characteristics. • PSD (surface area/kg). • Moisture (energy consumption). • Preserving product purity. •
But, who cares? What does ‘Product Quality’ mean to you? Purity: • Sulphuric acid plant owners. • Traders. • Physical characteristics: • Forming facility owners/operators. • Terminal owners/operators. • Transportation companies (truck, rail and shipping). • Sulphuric acid plant owners. •
How can we manage dust formation? Understanding the behavior of monoclinic and orthorhombic sulphur. Freshly produced product is in a monoclinic crystal phase, and converts during cooling and over time to an orthorhombic structure (aging). Monoclinic sulphur is stronger, and less likely to release • fugitive dust. Application of dust suppression moisture is typically not • required. Phase change in stockpile is exothermic, and may contribute • to product caking.
How can we manage dust formation? Handling product like the friable product it is. Traditional material handling systems may not be optimized for the properties of sulphur. Belt speeds. • Impact and abrasion damage. • Static generation. • Transfer points. • Number of transfer points. • Design of hoods, chutes and feed boxes. • Dust control. • Prevention vs. suppression – beware of collection! •
How can we manage dust formation? Stockpiling Traditional stockpile and reclaim systems also may not be optimized for the properties of sulphur. Stockpile feed system. • Impact and abrasion damage. • Caking – it’s a fact! • Role of temperature in caking. • Stockpile depth and cooling capacity. • Particle segregation. • FIFO •
How can we manage dust formation? Reclaiming from storage Reclaim systems contribute significantly to dust generation relative to the stresses imparted on the product. Gravity reclaim systems rely on the flow-ability of the • product with little product damage – caking can result in flow problems. Mechanical systems are more aggressive and impart more • stresses onto the product - less affected by caking to a point, but can result in equipment damage if severe.
How can we manage dust formation? Reclaiming from storage - gravity Gravity reclaim systems are usually associated with silos or storage bins. Design considerations include: Mass vs. funnel flow – FIFO. • Capacity limitations. • Compressive/crush strength limiting height. • Elevating product (long incline conveyors, bucket • elevators). Gravity reclaim systems will generally require less • equipment, therefore can offer low OPEX costs.
How can we manage dust formation? Reclaiming from storage - mechanical Mechanical systems can include portal reclaimers, eurosilos, front end loaders (FELs), grab buckets. Design considerations include: Large footprint (and large building) relative to the product • Angle of Repose (AOR). More difficult to manage FIFO stockpile management. • Particle segregation may result in high fines content at base. • Operating availability can be an issue. • Mechanical reclaim systems will generally require more • equipment, therefore expect high CAPEX and OPEX costs.
How can we manage dust formation? Ship/railcar loading Ship or rail car loading systems can contribute to dust generation, or, can help minimize dust. Design considerations include: Ability to minimize drop distances - slewing and sloughing • capability. Particle segregation in hold may result in high fines content • in some areas. Capability to vary dust suppression moisture relative to • observable dusting.
How can we manage dust formation? Dust prevention and suppression. Focus on preventing fugitive emissions rather than suppressing dust which has already escaped the product stream. Design considerations include: Application of foam upstream of transfer points. • Precise application of moisture relative to product flow rate • – variable by operator. Use dust prevention/suppression effectiveness feedback • from downstream stakeholders to optimize application rates. Use correct ratio of surfactant-water – too much or too little • will degrade effectiveness.
What about moisture? Typical solution to dust – is it good or bad? • Dust prevention vs. dust suppression • Surfactants and biocides – where to apply? • Moisture content – how much is enough? Does anybody care?
What about moisture? What if there’s too much moisture? Drainage during voyage – bilge pumping. • Dissolving protective coating (lime wash, HoldBlock). • Electrochemical reaction between sulphur and steel. • H2S formation. • Pyrophoric iron. • Thiobaccilli growth + time - increasing acidification en- • route and in stockpiles. Water collection and treatment. • Higher neutralization costs. • Increased filtration costs. • Higher energy costs. • Would you care about moisture?
How to Control Dust? Monitor the SRU – understand the impact a • problem at the SRU can have on sulphur forming and handling operations.
How to Control Dust? Measure and report forming plant product • physical quality – both SUDIC and temperature. Make product quality an measureable operating standard.
How to Control Dust? Review the handling system upstream of • storage – look for product damage, enhanced cooling opportunities, inappropriate moisture/chemical addition.
How to Control Dust? Develop a stockpile management plan to • avoid: Caking. • Segregation. • Dead storage (FIFO). •
How to Control Dust? Develop a reclaim methodology to ensure: • FIFO • Reduction in accumulated segregation • fines. Delivery of consistent physical quality •
How to Control Dust? Review downstream conveying and ship/rail • loading systems: Regular sampling and analysis • Determine high attrition points • Prevent dust rather than suppress •
How to Control Dust? Communicate! • Understand the objective • Communicate everyone’s role • Measure the progress • Share the results •
Forming and handling sulphur is all about effectively controlling dust… …SRU to acid plant!
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