From Recovery to Remelting

Mark Gilbreath, Matrix PDM Engineering, USA outlines infrastructure considerations for global dry sulfur logistics. Read more below or download the PDF here. 

Sulfuric acid – the most commonly used chemical in the world – is a primary feedstock in the production of fertilizers, as well as in the manufacturing processes of many other products.

Today, more and more sulfur is being generated as a result of increased global oil and gas production and environmental regulations that demand lower sulfur content in transportation fuels. The result is an evolving need for efficient sulfur storage and transportation logistics, which has, in turn, led to increased reliance on the production and transportation of dry formed sulfur that can be carried in bulk collier ships. Concurrently, large new facilities that have the capacity to form over 1000 tpd of sulfur are being constructed in Canada, India, Iran, Kuwait, Malaysia, Mexico, Turkey and Vietnam.

From recovery of molten sulfur, to dry bulk solids, and back to molten sulfur, this process requires specialized technology and infrastructure to ensure safe handling, transportation, and storage. This article focuses on those processes and infrastructure.

Degassing units
Sulfur that has been degassed to lower hydrogen sulfide (H2S) results in higher quality and much safer formed dry sulfur prill. Claus liquid sulfur contains 250 – 350 ppmw of dissolved H2S/H2Sx. With a long logistic supply chain, dangerous H2S is released during storage, handling, and transportation. This is particularly dangerous due to potential H2S buildup in a ship’s hold during ocean transportation.

Key drivers for sulfur degassing are safety, health, and environmental improvements. Degassing units that include contactor, cooler and mechanical systems are readily available in vertical modular packages.

Sulfur forming units
Products that can be handled as dry bulk solids are formed by either dry pastillation, granulation, or wet prilling. The objective is to solidify molten sulfur into a product with a shape and integrity that will create the minimum amount of fine sulfur particles during transport, transfer, storage, and reclamation. Sulfur dust is both a health hazard and presents the potential for explosion if collected in a confined space with an ignition source.

Pastillation units spray water under a steel belt on which sulfur drops are deposited to produce pastilles. Meanwhile, granulation units use water sprayed into a rotating drum for cooling the liquid sulfur that is sprayed onto a seed curtain to form granules.

Prilling introduces liquid sulfur at the top of a forming tank for direct countercurrent heat exchange with water to produce prills that are withdrawn from the bottom of the forming tank via screens. Unlike a pastillation or granulation unit, prilling units are readily adaptable for modular construction. Major components include the forming tray, fume hood and scrubber (if required), forming tank, dewatering screen and dry product conveyors. Mechanical equipment includes the process water and cooling tower supply pumps and cooling tower with fan units.