reduced labour requirements. Its use also minimises the formation of any emulsion and improves separation, thereby reducing carryover into the finished product. This type of mass transfer has been utilised in a range of applications since 1977. When used for treating light hydrocarbons such as liquefied petroleum gas (LPG) in a high-efficiency caustic treating process, the mass transfer device removes mercaptans (RSH), H₂S, carbon dioxide (CO₂), carbonyl sulphide (COS), and elemental sulphur. For heavier streams such as gasoline/ naphtha, condensate, and crude oil streams, this mass transfer device is used in a caustic/ catalyst/air system that sweetens mercaptans. The use of improved mass transfer devices, such as the non-dispersive fibre-containing device, has allowed the supplier to support its client’s ability to remove millions of pounds of sulphur annually by treating H₂S and mercaptans. Removal of the impurities, in turn, eliminates the emission of millions of pounds of SO₂. To facilitate even better outcomes, an advanced high-efficiency version of the same mass transfer technology has been launched to increase hydrocarbon treating rates from new and existing mass transfer treating units by up to 150%. Accompanying mass transfer technologies Fiber Film Contactors are the preferred non- dispersive technology solution used to treat mercaptans (RSH) and H₂S in a variety of licensed technology types provided by Merichem Technologies, LLC. Examples of some of the technologies are below. The most commonly used technology solution uses caustic as the treating reagent in liquid and gas hydrocarbon streams to easily remove H 2 S, RSH and CO₂. With other additives like amine, it can remove carbonyl sulphide (COS) as well. Typical treatment to remove H₂S and RSH uses 14-20 wt% sodium hydroxide (caustic). Caustic will also remove CO₂ and some elemental sulphur. For COS removal, the system uses MEA/caustic, which is effective at hydrolysing COS to meet end clients’ specifications. The most common technology used for sweetening mercaptan compounds in gasoline/ naphtha, condensate and crude oil streams using caustic/catalyst/air as treating reagents was first licensed in 1977. A single vessel
Untreated feed in
Feed Treating solution
Aqueous treating solution in
Treated product out
Treating solution out
can achieve RSH sweetening with no need for additional settling vessels. It facilitates pipeline specification requirements for natural gas liquid (NGL), Y-grade fuels, pentane, or condensate and removes odorous RSH with minimal processing to meet total sulphur specifications. Additionally, there is another technology widely used for the removal of total acid compounds (TAN) such as H₂S, naphthenic and phenolic compounds, mainly found in diesel, kerosene and jet fuel cuts. The use of the Fiber Film Contactor minimises mixing energy, allowing for a high caustic spending into sodium naphthenate without producing the emulsions or carryover typically experienced in conventional prewashes, such as those consisting of mixer/electrostatic precipitators. The use of caustic to remove mercaptans can become costly if the caustic is not regenerated. In addition to the treatment technologies, another technology serves just that purpose. The goal of these units is to minimise the reintroduction of disulphide oil (DSO) into the hydrocarbon stream being treated for mercaptan removal while regenerating the caustic to allow it to continue to remove mercaptans, thus lowering operating expenses. The combination of the extraction and regeneration units can handle turndown scenarios well and has even handled up to 20% of C₅+ material in a particular feed, with the only impact being increased caustic consumption. Figure 1 Fiber Film technology achieves efficient contact, maximising interfacial surface area, enhancing microscopic diffusion and mass transfer while minimising mixing energy and aqueous carryover to meet treatment specifications
Refining India
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