Innovative sulfuric acid production
A known production method gets a makeover

Since the company was founded, Bayer has been using sulfuric acid in a number of processes during production of synthetic dyes. Sulfuric acid is a basic substance in the chemical industry, and this has not changed for the past century. This article shows that it takes a lot of know-how during the planning, engineering and implementation phases to build a sulfuric acid production line.

The Bayer Group, from the early days of its existence, has used sulfuric acid in a variety of processes, starting with the manufacture of synthetic dyes. As early as 1925, Bayer had the largest sulfuric acid capacity on the European continent.
In the early 60s, Bayer was turning out nearly 1 million tons of H2SO4, equivalent to one-third of total production in the Federal Republic of Germany, or 2 % of global production.
Despite seemingly insurmountable difficulties in the initial phases of development, Bayer never gave up on its attempts to improve the method. Accordingly, it not only became a major manufacturer, but was also highly advanced in terms of mastering and fine-tuning the entire process.

The highpoint of these efforts was its development of the Double Contact Process.
Bayer submitted a patent application for its “Double Catalysis Process” in 1960. The first plant went into operation in 1964. Thanks to intermediate SO3 absorption, the improved contact process made it possible to significantly increase final SO2 conversion and thus considerably reduce SO2 emissions. More stringent environmental regulations enacted in the 70s resulted in the technology becoming widely used the world over. The plant was optimized in subsequent years, but in 1999, after over 35 years of continuous operation, a contract was awarded to Bayer Technology Services GmbH (BTS), a Bayer Group company, to engineer a new sulfuric acid production plant. Prior to winning the contract, BTS had assisted the plant operator, Lanxess (a company spun off from Bayer's chemical business and segments of its polymer business), in making the classical make-or-buy decision. Studies were conducted together with the operator to compare the costs and evaluate the advantages and disadvantages of individual options, such as repairing the old plant, entirely buying in the required products or building a new production plant.
At the same time, well-known engineering firms in the marketplace were invited to submit turnkey bids. However, the deciding factor for giving the contract to BTS was the expertise and experience it has gained over the last several decades working on collaborative projects.
Target: minimize total costs
After drawing up a mass and energy balance using a process calculation program, key parameters were defined early in the basic engineering phase, the aim being to minimize total cost for the operator over the entire life cycle of the plant. In addition to the actual investment costs, which are naturally the focus of any such project, consideration was also given to the expected future maintenance costs. Each and every detailed solution was analyzed and evaluated on the basis of these business aspects. Examples include:
-Low-NOx two-stage sulfur combustion
-No brick lining anywhere in the plant
-Maximization of oleum production
-Improved energy recovery
-Air cooling instead of water cooling
-Optimized safety concepts, e.g. emergency collection tanks for all acid- and oleum-conveying apparatus; water detectors downstream of steam-conveying apparatus
Optimizing the process in the sulfuric acid plant was a joint effort by experts from BTS’s specialist departments and Lanxess, who have many years of experience in the operation of the individual units. For example, in cooperation with combustion experts, a sulfur combustion process was designed and implemented that incorporates two stages with intermediate cooling. It enables a low combustion temperature and prevents the generation of thermal NOx in anything but very small quantities. At the same time, however, the process delivers the SO2 concentration required for four catalyst beds with greater than 99.8 % conversion. The following diagram illustrates the sulfur burner designed as a water-tube boiler.
Selection of material
Another example of the efficient support provided by BTS specialists is the design and dimensioning of all absorption towers, from the air dryer to the final absorber. Following thorough analysis, the specialist departments collaborated with the project team to define optimal components for each absorber. Selection of appropriate materials was based on recommendations from the Materials Department, which has extensive expertise in choosing materials for various corrosive media. Conclusion of the basic engineering phase was followed by detail engineering, where the project team focused on the completion of the P&I diagrams, the final specifications, procurement of primary equipment and full implementation of measurement and process control requirements.
As this example illustrates, the products and services of Bayer Technology Services are based on many years of innovative research and development work. A wide range of unique products and technologies has given the company its reputation as an effective problem-solver and reliable process supplier.