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Combustion equipment for SRUs

Summary

New developments in combustion equipment for sulphur recovery are meeting the demands of today's stringent performance and environmental requirements. In this article we discuss improved burner designs and handling options for processing ammonia.

Abstract

More stringent regulatory standards for air emissions, coupled with the long-term trend towards the processing of higher proportions of heavy sour crude feed, have created economic challenges for refiners. In addition, there is a trend towards an increase in the amount of ammonia that is being processed in modern sulphur recovery units (SRUs). Although it is technically feasible to process very high concentrations of ammonia in the main reaction furnace of a SRU, the economic impact is significant. The main economical consideration is due to the increased hydraulic load of the SRU and tail gas treating unit (TGTU), owing to the additional amounts of nitrogen and water that are processed. The source of this nitrogen and water is a combination of the additional combustion air required for oxidising the ammonia, as well as nitrogen and water being the reaction products of this oxidation reaction. Keywords: Keywords: oxygen enrichment, gasification, acid gas burner, CFD, mega burners, high intensity burner, reaction furnace, reducing gas generator, thermal oxidiser, ammonia processing, stoichiometry-controlled oxidation, SCO.

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Acid towers and their replacement

Summary

The 37th Annual International Phosphate and Sulphuric Acid Technology Conference of the Central Florida Section of the American Institute of Chemical Engineers (AIChE) at Clearwater on 7-8 June fulfilled the organisers' and participants' expectations, with well-attended sessions and lively discussions of the issues on the agenda.

Abstract

This year, two sessions were held on the opening Friday afternoon of 7 June. One was the usual sulphuric acid and technology session, chaired with customary aplomb by Rick Davies and Jim Dougherty, addressing the theme of Acid Towers and their Replacement. The Sulphuric Acid Workshop focused on the design, operation and maintenance of acid towers, also assessing the factors involved in their replacement. C. Guy Cooper of Noram Engineering & Constructors outlined The Design of Brick-Lined Towers in Sulphuric Acid Service. Noram Engineering has formed a marketing alliance with Tenova Mining & Minerals to supply a full range of proprietary equipment for sulphuric acid plant design and construction. The respective merits of brick-lined and alloy towers were assessed: Noram Engineering supplies both. The company can also supply SX alloy towers for retro-fitting. Keywords: brick-lined towers, alloy towers, acid leaks, PTFE lining, mist eliminator, ZeCor, reskinning.

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SOxClean: an alternative to burning sulphur in air

Summary

The unique capability of Calabrian's SOx submerged combustion technology to provide in-situ, on-demand pure SO2 and SO3 in a safe and reliable manner is creating new opportunities for the use of these critical reagents. Jeff Hammerstrom of Calabrian Corporation discusses the key features of the technology and its benefits when applied in a variety of applications, including in-situ production of sulphur trioxide (SO3), debottlenecking sulphur recovery units (SRUs), and solution mining.

Abstract

Sulphur has been burned since antiquity. In ‘The Odyssey’, Odysseus asked for sulphur to purify his house; and the expression “fire and brimstone” goes back to biblical times. So what in the name of fire and brimstone can possibly be new about burning sulphur or manufacturing sulphur dioxide and sulphur trioxide? For years, processes requiring sulphur dioxide or sulphur trioxide utilised a conventional air-sulphur burner as the starting point. However, there is an alternative that provides superior economics, operational advantages/flexibility, and improved reliability, namely submerged combustion of pure oxygen in sulphur. Submerged combustion is a safe, environmentally superior and permit friendly way to produce SOx. The good news is that it’s not new; it’s been in commercial operation for over 20 years. SO2Clean is a proven, commercial, and proprietary technology developed by Calabrian Corporation to produce high purity SO2 via submerged combustion. Above is a photo of the Calabrian Corporation SO2Clean sulphur dioxide plant at Port Neches, Texas. It consists of two parallel, independently run 50 t/d trains that occupy a 9.1 m x 21.3 m footprint. The Port Neches, Texas plant has been operating for over 20 years. Keywords: sulphur dioxide, sulphur trioxide, submerged combustion, oleum, sulphuric acid, solution mining, metal leaching.

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Advanced WESP designs assure superior gas cleaning performance

Summary

Nowadays, many industries are facing formidable environmental challenges and there is a growing need for effective, economical gas cleaning and air pollution control equipment. Michael Beltran of Beltran Technologies, Inc. reports on a renewed interest in high-efficiency wet electrostatic precipitators (WESPs) and discusses their importance for controlling sulphuric acid mists and other pollutants in a wide range of industries including mining, metallurgical and power generation.

Abstract

The global economic recovery continues to be sporadic among most of the world’s economies, with many industries experiencing persistent volatility in profits, prices, markets and capital investments. Yet, some financial analysts are predicting an eventual resumption of long-term growth trends in such basic industries as mining and metallurgy, petroleum refining, and fossil-fuelled (primarily coal) electric power generation. Experts anticipate that global demand for mined resources, transportation fuels and energy, in both developed and developing nations, will be driven by relentless population growth, increasing urbanisation, rising incomes, and expectations of higher living standards among populations exposed to an array of digital communications technologies and social media. While by no means a boom, these trends, coupled with a growing worldwide concern over environmental issues, portend a continuing and perhaps sharper focus on the formidable environmental challenges facing these and other industries, and the growing need for effective, economical gas cleaning and air pollution control equipment. Keywords: wet electrostatic precipitator, roasters, smelters, particulate matter, sulphur dioxide, heavy metals, air pollution.

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SRU shutdown systems - Part 1: History and basics

Summary

This is the first of a two part article on SRU shutdowns. In Part 1, Jim Hampsten of Principal Technology, Inc. provides basic information for the design, specification, and installation of an SRU shutdown system. All SRU shutdown systems are not created equally. Frequently designers and operators are unclear about the intended functions of the system components and the associated interlocks. Background associated with the historical use of SRU shutdown systems and their components is presented. An overview of shutdown initiators, their implementation, and purpose for each are provided. Special considerations and interlocks between units are also noted along with a brief discussion of the shutdown devices.

Abstract

Since sulphur recovery units (SRUs) were first built they have had some sort of “shutdown system”. These systems have also been known as interlock systems, safety systems, and other less technically descriptive names. It has always been recognised that an operating SRU has the potential for equipment failure that could release toxic and flammable gas to the atmosphere; therefore instruments and systems to monitor unsafe conditions have generally always been included. The current state of the industry with increasing dependence on reliable sulphur unit uptime, process safety, environmental compliance, and multiple unit interactions makes this a critically important aspect of unit design and operation. History Until the early to mid-1990s most plants considered the SRU shutdown system to be a source of operational aggravation due to the system’s propensity to cause unwanted shutdowns of the SRU. Further, the built-in functions of the systems frequently prevented straightforward start-up of a unit after a shutdown. In order to get the units started and keep them operating the shutdown systems were often partially or completely bypassed. While this kept the units online, long term reliability and safety were compromised. Keywords: sensors, shutdown devices, interlock systems, shutdown initiators, emergency shutdown, Safety Integrity Level.

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A non-sulphur route to phosphoric acid

Summary

Most sulphuric acid is used for the treatment of phosphate rock to produce phosphoric acid, for fertilizer, animal feed and other uses. However, there are other techniques for producing phosphoric acid, and one of them, the Improved Hard Process, claims to offer the advantage of lower cost and the ability to use lower grade rocks compared to the conventional wet acid process, with potential consequences for sulphur and sulphuric acid markets.

Abstract

Phosphoric acid has traditionally been made either from reacting phosphate rock with sulphuric acid (the Wet Acid Process – WAP) or via a high temperature electric furnace carbon reduction (the Electric Furnace Process). In the middle years of the 20th century, almost half of all phosphoric acid was produced via the electric furnace process, as optimised by the Tennessee Valley Authority in the early years of the 20th century. Over the second half of the 20th century, however, rising electricity prices and falling prices for sulphur and sulphuric acid meant that the wet acid process began to achieve a clear economic advantage, and so it has come dominate world phosphate production. The effect on sulphuric acid consumption has been dramatic; today about half of all sulphuric acid is used in the production of phosphates via the wet acid process. But what if there was an economic alternative? Experiments in the 1960s showed that it was possible to replace expensive electrical energy in the furnace process via heat energy in a rotary kiln, but it was not until 1981 that Dr Robert Hard of Occidental Research (a subsidiary of Occidental Petroleum) overcame issues with the kiln charge melting. Further work on improving the process was however cut short by the demise of the Occidental Research company in 1984 in a corporate reorganisation. Development continued sporadically under Hard’s former colleague Dr Joseph Megy, who formed his own company, JDC Phosphate Inc, to work on improving the Hard Process. However, it was not until 2003 that work began in earnest on what is now the Improved Hard Process. Since 2007 JDC Phosphate has been working on commercialising this new process, and this July its 12,000 t/a demonstrator plant was commissioned in Florida. Keywords: PHOSPHOGYPSUM, DIHYDRATE, HEMIHYDRATE, AGRIFOS, WONARAH, MINEMAKERS

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The changing oil industry

Summary

Tight oil from shales has become as much of a 'game changer' in the US oil industry as shale gas has in power and chemical production, and for similar reasons. But the oil industry is also facing many other structural changes which will alter the direction and amount of sulphur production from refiners in the future.

Abstract

Tight oil from shales has become as much of a ‘game changer’ in the US oil industry as shale gas has in power and chemical production, and for similar reasons. But the oil industry is also facing many other structural changes which will alter the direction and amount of sulphur production from refiners in the future. For the first decade of the 21st century, rapidly declining production from some of the larger, more mature oil fields in production and a lack of new fields coming on-line, coupled with forecasts of steadily increasing demand, especially from industrialising Asia, led some to speculate that we had reached a global peak in oil production, and faced rapidly increasing prices as production dropped, in much the same way that the US had during the 1980s and 90s. The so-called ‘Hubbert Curve’, named after the geologist who theorised it in the 1950s, was due to apply to global oil stocks, it seemed. Keywords: OPEC, fracking, tight oil, Asia, NOC

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China's sulphur and sulphuric acid industries

Summary

China dominates many sectors of the sulphur industry and has been the largest elemental sulphur importer for some years, but new refineries, smelters and sour gas projects are changing the country's sulphur balance.

Abstract

China’s industrialisation has come to be the major factor in pretty much every commodity market over the past two decades, from coal, oil, copper and steel to fertilizers. Given the reach of sulphuric acid into so many industrial areas, both its consumption and production, and the relationship of sulphur production to oil and gas processing, it is of no surprise that China has also come to dominate the sulphur and sulphuric acid markets. Chinese moves to self sufficiency in metal and fertilizer production have on the one hand generated large volumes of smelter acid, and on the other been an outlet for this acid into the country’s burgeoning phosphate industry. But while both of these continue to grow, it is China’s rapidly expanding natural gas industry, both sweet and sour, conventional and unconventional, which is beginning to shape the picture for the years to come. Unconventional gas China is an energy hungry nation, and most of this is supplied by coal. While globally gas consumption represents almost 25% of energy demand, in China this is only 4.7%. However, the government is committed to increasing the share of the national energy mix played by gas in an attempt to wean it off polluting coal. China’s 12th five-year plan calls for natural gas to provide 8% of China’s energy mix in 2015 and 10% in 2020. Gas production has been rising rapidly, from just 27 bcm in 2000 to 107 bcm in 2012, but there are plans for this to rise more rapidly still, and unconventional gas is particularly slated for a rapid rise. Last year China’s combined unconventional gas production, from shale, tight gas and coalbed methane, totalled 44.5 billion cubic metres, according to the China National Petroleum Corp, or about one third of national output, but this is projected to almost triple to 120 bcm by 2020, representing 52% of domestic supply by that time, according to the China Academy of Engineering. China is aiming at 80 bcm of tight gas production by that time, 30 bcm of coalbed methane, and 10 bcm of shale gas. Keywords: unconventional, tight gas, coalbed methane, sour gas, refining, Puguang, Chuandongbei, smelter, DAP

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