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Publication > Issue > Articles

Desulphurising Biogas

Summary

Biomethane is a sustainable energy carrier that can be used as a substitute for natural gas, but an essential step in biomethane production is biogas desulphurisation. Onkar Dixit and Norbert Mollekopf of TU Dresden compare several desulphurisation processes and recommend those suitable to remove H2S from biogas.

Abstract

Biomethane is methane derived from biological sources and constitutes a sustainable energy carrier whose chemical composition is identical to natural gas. The biomethane industry is booming due to the on-going transformation of the energy system from fossil fuel-based to sustainable fuel-based. Up to 2020, investment of up to e12 billion is expected in the biomethane industry in Germany alone1. Biomethane is obtained after purifying biogas or landfill gas, which in turn is produced by the bacterial, anaerobic digestion (fermentation) of biomass. Biogas composition is shown in Table 1, and the biogas-treatment scheme is depicted in Figure 1. As Table 1 shows, sulphur mainly occurs as hydrogen sulphide (H2S) in biogas in concentrations from 100 to 30,000 ppm (0.01 – 3% v/v). The exact concentration depends on the substrate used during fermentation and on the process conditions prevalent in the fermenter. Keywords: LO-CAT, THIOPAQ, SULFATREAT, BIOSX, SULFACHECK, ELIMINATOR

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The outlook for sulphur

Summary

Several delayed sour gas projects and a lull in metallurgical demand for sulphuric acid now seem to be about to – finally – deliver the long-awaited global surplus of sulphur, but investment in the phosphate sector continues to drive healthy demand for sulphur and sulphuric acid.

Abstract

Production of sulphur in all forms reached approximately 88 million t/a in 2013. Elemental sulphur (‘brimstone’) production continues to represent the lion’s share of this, at just under two thirds (about 56 million t/a in 2013). The remaining one third comes from metallurgical acid production from metal smelting. Of the 56 million tonnes of elemental sulphur production, almost all is accounted for by sulphur extraction from oil and gas, and while in the past these two segments have been roughly even, the proportion accounted for by sour gas processing is starting to edge ahead. Metallurgical acid and recovered sulphur from oil and gas production are all involuntary sources of sulphur, making the supply side of the equation dependent very much upon the markets for oil, gas and metals, particularly copper. Sulphur production from mines continues to be at a very low level, with the re-start of the Mishraq sulphur mine in Iraq now dependent on the security situation in the north of the country being stabilised. Likewise acid production from pyrite roasting remains a minority pursuit, mostly happening in China and gradually declining as metallurgical and sulphur-burning acid capacity come to dominate there. Keywords: REFINERY, SOUR GAS, SMELTING, LEACHING, PHOSPHATE

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Sulphur and Sulphuric Acid in South America

Summary

The combination of copper mining, oil and agriculture make the South American continent especially important to the sulphur industry, and the region has had a decade-long boom, driven by high commodity prices and low interest rates. However, the signs are that this is coming to an end, as Brazil slips into recession and Venezuela's internal turmoil continues.

Abstract

South America is a large and diverse region, home to 380 million people, and its industries cover many of the diverse facets of the modern sulphur industry. There is major metal mining and smelting, in Chile and Peru, with associated sulphuric acid production and consumption, considerable oil production and refining capacity in Venezuela and Brazil, and large-scale phosphate use and fertilizer demand – particularly in Brazil. The past few years have seen expansions in all of these industries as the world’s need for commodities of all kind has led to increasing investment, but the economic horizon looks less certain now for the continent. Oil refining An uprating of Venezuela’s oil reserves, taking into account the potential of the heavy oil belt of the Faja de Orinoco, has lifted South America’s share of global oil reserves from around 10% a few years ago to just under 20% in 2013, according to BP’s figures. This huge uprating of Venezuela’s reserves, from 77 billion barrels in 2003 to 300 billion barrels today, means that Venezuela now dwarfs the reserves of other oil producing countries in the region, like Brazil and Colombia, and in theory possesses the largest oil reserves in the world, ahead of Saudi Arabia at 265 billion barrels, and Canada at 175 billion barrels (again much of it down to oil sands), and most of it has a very high sulphur content. Keywords: OIL SANDS, TAR SANDS, VENEZUELA, BRAZIL, CHILE, PERU, SMELTING, LEACHING, PHOSPHATE

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State-of-the-art acid gas treatment

Summary

The requirement to meet ever more stringent emission regulations for sulphur compounds when processing sour gas can present many challenges. In this article, KT – Kinetics Technology discusses problems associated with the presence of COS and CS2, Jacobs provides case studies demonstrating how the acid gas removal unit and sulphur recovery unit can be optimised and Prosernat reports on the SmartSulf™ process for the desulphurisation of low H2S content gas streams.

Abstract

Sour gas processing to remove hydrogen sulphide from gases is required for environmental reasons, to limit the emission of sulphur compounds to the atmosphere. With emission limits becoming tighter and the hunger for energy growing, energy sources previously regarded as too expensive or difficult to be processed due to the low quality of the raw materials are now attracting the attention of companies and governments for reasons of convenience or the desire to be self sufficient in energy. The main fields of application for H2S removal are: l natural gas and associated gas sweetening; l refinery gas sweetening; l syngas treatment; l SRU tail gas treatment (without acid gas enrichment) l SRU tail gas treatment (with acid gas enrichment) Keywords: gas sweetening, IGCC, AGE, tail gas treatment, Sulfinol-M, coal gasification, lean H2S gas, SmartSulf™

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Hydrogen explosions on the rise

Summary

While the phenomenon of hydrogen formation in sulphuric acid plants is well known, the growing number of hydrogen incidents has been the driving force for an industry wide review of such events. This article summarises the work done by the Hydrogen Safety Committee to develop awareness of the key considerations to mitigate such events.

Abstract

The formation of hydrogen in sulphuric acid plants is a known phenomenon and is a result of the corrosion of metallic materials at specific conditions. Those conditions are strongly dependent on acid strength and temperature. As a result, an explosive mixture of hydrogen and oxygen containing process gas can occur with the potential risk of a hydrogen explosion. Over the last couple of years several incidents related to this have been reported. The majority of the reported hydrogen events took place in intermediate absorption systems, in converters or heat recovery systems. In general the incidents occurred during maintenance or after stopping the gas flow through the plant. In all cases water ingress, resulting in low acid concentration, caused the formation of the hydrogen; in most of the cases the water ingress was ignored or not noted and mitigation measures weren’t in place. As a result, severe damage in different items of equipment of the plant took place. Keywords: hydrogen explosion limits, hydrogen formation, acid concentration, hydrogen accumulation, acid coolers, economisers, absorption towers

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Solid sulphur handling at sulphuric acid plants

Summary

K.H. Daum, S. Bräuner, and H. Storch of Outotec provide an update on solid sulphur handling in sulphuric acid plants, looking into the history, showing the developments over the last decades, and presenting the latest state of the art, particularly with regard to melting.

Abstract

Where the supply of liquid sulphur, mostly originating from refineries, is not available due to lack of infrastructure, solid sulphur has increasingly become a dominant source of supply for acid plants. This is particularly the case at remote locations where the acid production is located close to a metallurgical operation, e.g. nickel leach processing, or a fertilizer manufacturing where the acid plant would be close to the phosphate mine. Fundamentals The energy demand of a sulphur melting unit comprises a number of individual items as presented in Table 1. Typical figures for steam demand vary in practice between 100 and 130 kg steam per tonne of sulphur. The latter would include the steam required to keep all other vessels in the section at the desired temperature, i.e. compensate for the heat losses. Keywords: sulphur melting, sulphur impurities, explosion hazards, sulphur filtration, sulphur storage, sulphur handling

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