50 years of industrial gas treatment

The past and the future of gas processing technology.

Torsten Katz

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Article Summary

BASF is among the world’s leading companies in the field of gas treatment. This year, two anniversaries are on the agenda. The story of gas treatment began 50 years ago in 1971, when new gas treatment agents were first used to remove carbon dioxide (CO2) from synthesis gas in an industrial process in order to manufacture ammonia. The Oase brand was launched a decade ago, which BASF today uses for seven specific solutions for treating various gases, licences for advanced plant technology for gas treatment, and specific services.

This article outlines the history of gas treatment at BASF and current aspects of development. With Oase digilab, BASF developed a product that enables continuous monitoring of the treatment agent composition virtually in real time. Furthermore, the years of intensive research work in the growing field of floating liquefied natural gas (FLNG) begin to bear fruits. Even in the field of the established LNG business, the gas treatment team succeeded in winning the contract for the world’s largest LNG project. In terms of sustainability and climate protection, the possibilities for carbon capture and storage (CCS) projects are also of growing interest, with BASF aiming to improve the efficiency of its processes in terms of saving energy and minimising emissions. All of these projects underline the growing importance and considerable development potential of gas treatment, even though it is already 50 years old.

The Ammonia III complex in Ludwigshafen has made history in a number of ways. The plant covers six blocks between Acetylenstrasse and Rheinstrasse in one of the world’s largest chemical sites, which is operated by BASF on a bank of the Rhine. As the first modern large-scale plant, it heralded a new era in ammonia generation — a procedure which had been developed at BASF at the beginning of the 20th century by the German chemists Fritz Haber and Carl Bosch. The plant processes natural gas using the steam reforming process, produces 1200 metric tonnes of ammonia daily, and swallows almost 60000 cu m/h of natural gas. The methane content of natural gas reacts with water and air in the primary and secondary reformer to create a mixture of CO2, carbon monoxide, hydrogen, and nitrogen (synthesis gas). Steam is then used to convert carbon monoxide into hydrogen and CO2, and the latter is treated using an aqueous alkaline solvent. In the reactor, nitrogen and hydrogen are subjected to a temperature of 450°C and a pressure of around 300 bar to create ammonia.
Ammonia III is still in operation. The synthesis reactor including catalyst weighs 500 tonnes; the high pressure compressor has an output of 25 MW; and about 140000 cu m/h of synthesis gas are conditioned. The treatment tower for CO2 removal is more than 70 m high and is where BASF’s gas treatment activity began 50 years ago. What began as an internal process is now a global business concentrating on more than just the treatment of synthesis gas. BASF also supplies gas treatment processes for natural gas, refinery tail gas, flue gas, and biogas. It is against this backdrop that the Oase brand was established a decade ago; this covers various application areas of gas treatment with a range of gas treatment agents and technologies.

Growth in gas treatment
According to a report by market research company Reports and Data, the global market for gas treatment was valued at $3.77 billion in 2018 and is predicted to reach just under $6 billion in 2025, which corresponds to an annual growth rate of 5.7%. This development is driven by increasing demand for natural gas, stricter regulatory provisions for reducing air pollution, and continued growth in the global population. Another factor is the increased use of natural gas for generating electricity and in other industrial sectors, a factor from which the expansion of gas treatment plants is likely to benefit greatly. In 2018 for instance, natural gas was already being used to generate around 35% of electricity in the US.

In light of the market outlook, BASF is continuing to focus on research and development in gas treatment. Coinciding with the double anniversary, BASF has advanced its Oase digilab project to the extent that it will be available in 2021 (see Figure 1). The BASF start-up trinamiX and the Oase team spent the last few years developing a method for analysing the composition of the gas treatment agents for Oase processes, partially online and virtually in real time. This was previously a time-consuming process, as samples had to be taken from the process at customers’ plants all over the world and then sent to two laboratories in Ludwigshafen and in Wyandotte in the US, with each analysis taking between six and eight weeks. The new method is far quicker and more effective. It works with trinamiX’s Near-Infrared (NIR) spectroscopy solution, which combines a high-performance NIR spectrometer with sophisticated data analysis (chemometrics). By scanning the light spectrum of the sample, the components can be determined qualitatively and quantitatively on the basis of the different levels of absorption. In future, users will be able to inject samples from their plants directly into the digilab device, receiving an analysis of the components within a few seconds. Oase therefore advances quality control in gas treatment and optimises the use of treatment agents. Users of the service can continuously monitor the condition of their gas treatment process and use the optimum solvent composition.

Ammonia III also played a decisive role in the testing and evaluation process for Oase digilab. The Oase team collected the first samples and received the first results, which allowed them to develop the method. Further tests were then performed at customers’ premises. The results obtained with the NIR method closely match the values from the traditional wet chemistry procedure, which are still collected for comparative purposes. Here, measured data is recorded for water, the base amine methyl diethanolamine (MDEA), and the activator system, with all results being saved via the analytics area in the Oase connect portal. This allows each user to access its data while enabling BASF to process the data on solvent composition in order to optimise the technology further. The Oase connect platform is a planning and simulation tool that significantly improves the project planning phase for new plants while also enhancing the operations of existing plants. Initial projects have been conducted successfully. Another special feature is the use of the Cape-Open interface, which allows an Oase connect simulation to be integrated in standard commercial process simulators.

Developing FLNG
Numerous projects in the field of FLNG have been developed around the world in recent years with the aim of exploiting important gas fields under the world’s oceans. This still relatively new method of extracting natural gas, generally at great depths, requires significant modifications to the gas treatment process. Therefore, BASF has researched gas treatment under these conditions over the last few years, in particular to optimise treatment to ship or ocean movements. A large-scale project with the Italian company Eni is already under way off the coast of Mozambique at a depth of around 2000 m. The Coral field in Area 4 of the Rovuma Basin contains around 450 billion cu m of gas, to be tapped using six underwater wells and a FLNG plant. BASF is performing gas purification for this ultra deep water project. The simulation tool from Oase connect is used to design the gas treatment unit, including an additional function to take the influence of the ship’s movement into account. Commissioning of the production vessel in the Coral field is planned for 2022.

Oase technology was used in the PFLNG 2 DUA project by the Malaysian energy major Petronas, the first FLNG project with BASF technology (see Figure 2). DUA is now operating in the South China Sea and is extracting gas from the Rotan deep sea gas field. The production vessel is designed to convey 1.5 million tonnes of LNG annually, which can be extracted from depths of up to 1500 m. Petronas achieved an important milestone with its ‘first drop’ on 15 February 2021. BASF has followed this comparatively new trend and has participated in floating production storage and offloading (FPSO) activities. In this case, the corresponding production units such as ships or platforms do not liquefy the gas but instead pump it onshore following conditioning. Gas treatment is indispensable for this, as CO2 and hydrogen sulphide must be removed using as little energy as possible. BASF is to perform gas treatment for Petrobras’ Marlim 2 project which will be installed around 150 km off the Brazilian coast at a depth of 930 m and should produce up to 70 000 barrels of oil and 4 million cu m of gas daily.

World’s largest LNG project
In February 2021, Qatargas signed a letter of award for the construction of four new LNG production plants in the North Field East (NFE) project off the north east coast of the Qatar peninsula. This field is believed to hold reserves totalling around 25 trillion cu m — around 10% of the world’s gas reserves. When exploited, it will be the largest current LNG project in the world and BASF is also playing a significant role in this; in line with an agreement made in 2019, the company is providing two technologies for all four new LNG plants: The first concerns high pressure acid gas removal units, while the second is for low pressure tail gas treatment units. The two technologies are named Oase purple and Flexsorb. (ExxonMobil has been supplying technologies for selective gas treatment under the Flexsorb name since 1983.) The technical licence package also includes plant design with the Oase connect tool, which played a key role during the front-end engineering design (FEED) phase. The four additional LNG trains will increase Qatar’s capacity from 77 million t/y to 110 million t/y. In this first phase in the expansion of the NFE project, Qatar will expand its LNG production by 40%. The project should be complete by 2026. A technological team from BASF in Germany will support local experts during commissioning and the performance testing phase. The company will provide continued support to Qatargas when the plant is in operation, by supplying the treatment agent and through technical expertise on-site.

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