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Sulphuric acid reclamation

Summary

A significant volume of sulphuric acid used in industrial processes generates contaminated acid streams which face increasingly stringent regulations on disposal.

Abstract

In the processing of bulk minerals such as phosphates, and copper, nickel and uranium ores, sulphuric acid is used as a reagent, but in many industrial and chemical processes, the acid acts either as a catalyst (such as in alkylation in refineries) or reaction medium, or (such as in titanium dioxide manufacture) as a temporary complexing agent, and does not form part of the final product. Nevertheless, there is a build-up of contaminant in the acid, and so to prevent too large a build-up of contaminant, ‘spent’ acid containing the contaminants is withdrawn in a constant stream and topped up with new ‘fresh’ acid. In this way, many of these processes generate large quantities of waste, dilute acid, which may also be contaminated with organic or inorganic compounds. Keywords: REGENERATION, CONENTRATION, MECS, OUTOTEC, AKER CHEMETICS, TOPSOE

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Sulphur from oil sands

Summary

The run of high oil prices has encouraged the development of unconventional oil resources in many parts of the world, including the heavy oil sands of Canada and Venezuela. But how will production from these high sulphur sources fare now that oil prices have come back to earth?

Abstract

The oil sands of Venezuela and Canada represent two of the largest concentrations of hydrocarbons in the world, on a par with Saudi Arabian crude reserves. The heavy, bituminous oil is trapped in a sandy lay close to (or occasionally on) the surface. It is viscous (completely solid in northern Canada) and high in sulphur, and so requires extensive processing to make it usable. This raises the cost of production, but the run of high oil prices ensured that the economic incentive was there to exploit them. Keywords: VENEZUELA, FAJA, CANADA, KEYSTONE, UPGRADER, BITUMEN, DILBIT, SYNCRUDE

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HIGHSULF PLUS makes its debut

Summary

HIGHSULF PLUS™, a recent addition to the HIGHSULF™ processes, brings a new dimension to acid gas removal and enrichment. In addition to increasing the H2S concentration of the SRU feed, this technology allows the amine unit (including TGTU) to control the H2S concentration in the acid gas feed to the SRU. T. K. Khanmamedov of TKK Company and J. M. Lawrence of Lexington Group International, Inc. compare and discuss some FEED data for an AGE unit based on the HIGHSULF PLUS process and present simulation and design numbers for a commercial unit in the FSU.

Abstract

Many natural gas streams contain small concentrations of H2S (between 10 to 40%), or contain high CO2 to H2S ratios. These streams can pose challenges to the designer and the operator because the acid gas produced by processing in a typical unit is sub-quality for Claus sulphur plant feed; however, it cannot be vented or incinerated because of the sulphurous compounds. Even in plants with a moderate CO2:H2S ratio of say 4:1, if complete acid gas removal is necessary (LNG for example), using a single contactor will necessarily produce an acid gas stream containing about 20% H2S on a wet basis. In other situations where total removal of the CO2 is not required, the resulting acid gas may be too dilute for a Claus sulphur recovery unit with straight through configuration. Keywords: acid gas enrichment, AGE, tail gas treating, HIGHSULF, dilute acid gas.

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Maintaining your sulphuric acid plant

Summary

Corrosion problems are a common cause of downtimes in sulphuric acid plants. New developments in corrosion resistant materials have led to fewer and shorter downtimes helping to minimise loss of production capacity. M. Salehi and A. Hopp of Steuler-KCH GmbH discuss the importance of engineering, top-quality products and careful installation by highly qualified expert personnel for planning production capacities over the long term.

Abstract

Despite the continuous developments in corrosion protection materials, the aggressive operating conditions in sulphuric acid plants lead to regular downtimes. During these downtimes the full gamut of corrosion protection work is carried out, from repairs to floors and ditches, to partial replacement of masonry in absorption towers, heat exchangers and pump tanks, to the switching out of complete components of the plant. Keywords: materials of construction, acid plant maintenance, corrosion protection, masonry, lining, refractory, potassium silica cement, carbon steel.

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Polymers in sulphuric acid service

Summary

In this article we report on fluorinated thermoplastic linings for sulphuric acid services, a unique and innovative approach to the design and inspection of FRP for fabricators and end users as well as recent and ongoing research into plastic materials for sulphuric acid services.

Abstract

Fluorinated thermoplastic linings The production and handling of sulphuric acid of various concentrations can lead to severe corrosion problems, unless adequate measures are taken to protect the equipment. For this, linings made from fluorinated thermoplastics (fluoropolymers) can be used. Fluoropolymers are very resistant to sulphuric acid, in particular fully fluorinated materials, which are not usually degraded by sulphuric acid at high or low concentrations. Hence, fluoropolymers are very good base materials for long-term resistance against corrosion in sulphuric acid containing environments without any measurable material loss. Keywords: fluorinated thermoplastic linings, FRP, predictive maintenance, fluoropolymers, rubber, HDPE, PVC, CPVC, PVDF, ECTFE.

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Making sulphur safer

Summary

At best, undegassed Claus sulphur results in nuisance odours, adversely impacts sulphur grinding and increases friability of formed solids. At worst, it results in fatalities and explosions. Although still not mandated in many countries, including the US, degassing to <10 ppmw total H2S is generally recognised by the industry as a best practice. Recent improvements to sulphur degassing processes are reported, including the first in-situ sulphur degassing technology for refineries and gas plants.

Abstract

Claus sulphur typically contains 300 ppmw H2S, nominally ranging from 600 ppmw in the waste heat boiler rundown to 10 ppmw in the final condenser. The liquid sulphur removed from the process gas stream in each condenser will contain dissolved H2S in the form of hydrogen polysulphides (H2SX) and H2S in equilibrium with the process gas. If this dissolved H2S is not removed, it will evolve from the sulphur product during storage and/or transport creating potentially hazardous conditions. Degassing the sulphur to reduce the H2S content considerably reduces the potential hazards. Keywords: liquid sulphur degassing, vent gases, gas scrubbing, sulphur pit, ICOn

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