Launched in 1996, VK69 is more relevant than ever

In 1996, we launched a ground-breaking cesium-promoted catalyst, the VK69, to help sulfuric acid producers cut the SO₂ emissions of their plants. VK69 was quickly adopted across the industry, and plants all over the world reached astoundingly low, two-digit emission levels, which had previously seemed impossible. 

A benchmark catalyst that improves profit margins

Today, some 30 years after its introduction, VK69 still remains the benchmark for cesium-promoted catalysts and is more relevant than ever. And while VK69 is still key to helping producers comply with ever tighter SO₂ emissions legislation, Topsoe and the industry have also found the catalyst highly useful for a number of other reasons: VK69 has proven very versatile in maximizing the profit margin of sulfuric acid plants by allowing them to boost their achievable capacity, reduce downtime, cut energy consumption, and reduce scrubber-related costs. As an additional advantage to cutting energy consumption and reducing scrubber-related costs, VK69 can also help reduce the carbon footprint of sulfuric acid plants and avoid the generation of scrubbing by-products that need to be disposed of. 

New shape and support material significantly improved activity

VK69 is a cesium-promoted catalyst specifically designed to deal with lean SO₂ gases typically found in the lower passes of the converter in double absorption plants. Today, with more than 175 installations successfully running, VK69 has proven to be an unmatched solution for reducing SO₂ emissions and increasing production rates.

Upon the introduction of the VK69 catalyst, it was already established that the use of cesium as a promoter could enhance catalyst performance in the low-temperature region by keeping soluble V-complexes in solution and thereby active in catalytic cycles. However, Topsoe understood that the performance of the catalyst in the lower passes of the converter was restricted not only by low temperatures but also by the lean SO₂ gases, where diffusion was the limiting factor. 

To address this limitation, Topsoe designed the VK69 catalyst with a new and unique 9 mm daisy shape, a revised support material, and an optimized melt composition. The result was a high-vanadium cesium-promoted catalyst that combined a very low ignition temperature with a significant activity advantage in the entire operating temperature range.

VK69 cuts emissions, improves plant performance

Initially envisioned as a cost-effective solution to help producers cut stack emissions, the catalyst has proven very effective in helping to address a number of other, new and eternal, key concerns as well. +9% in specific steam production, +7% higher acid production, double-digit SO₂ emissions, or slashing emissions by half, are all examples of what customers have achieved by installing VK69. 

Today, VK69 is installed in more than 175 sulfuric acid units worldwide and has successfully helped operators achieve:

• Increased acid and steam production rates by using a higher SO₂ strength, without increasing the plant’s pressure drop.
  
• Improved energy efficiency of the unit and reduction of the carbon footprint.
  
• Reduction of up to 50% in SO₂ emissions when used in the last bed of double absorption plants.
• Reduction or avoidance of scrubber chemical consumption and disposal costs of byproducts.
• Reduction of SO₂ emissions during startups.
• Flexibility to handle upsets in the plant, resulting in savings in fuel and less downtime.

As shown in Figure 1 depending on the application and the case, VK69 can be used in a full bed or as an ignition layer in the lower passes.

This catalyst is uniquely suited to help sulfuric acid plant operators address many of the new or stricter requirements placed upon the industry today, such as improving energy efficiency, reducing waste, or achieving ultra-low SO₂ emissions without reducing production rates.

A futureproof combination: VK69 and VK38+

As operators face more demanding conditions, they may be wondering what the next step is to maintain low emission levels without compromising productivity. In 2020, we launched the VK38+, a new non-cesium catalyst that offers a higher activity than any other potassium-promoted catalyst in the market. This catalyst can be combined with the VK69 to achieve even lower emissions levels. Operators can also utilize the flexibility that the extra activity of the combination VK38+/VK69 delivers to target specific bottlenecks.

Figure 3 demonstrates how the new VK38+/VK69 scheme can achieve improved emissions levels compared to the previous VK38/VK48/VK69 design. The example is based on a S-burner unit with feed gas of 11% SO₂ and 1000 MTPD capacity. If the unit is already using VK38/VK48 and VK69 catalysts and has a full converter with an emission level of 120 ppm, the unit can easily cut the emissions by 20% and achieve levels below 100 ppm simply by changing the catalyst from VK38/VK48 to VK38+ and adjusting the inlet temperatures by ±10°C.

A history as strong as its future

Since 1996, VK69 has helped operators not only to cope with every tightening SO₂ emission legislation, but also to boost their acid production, maximize energy efficiency, and have cleaner and faster startups. In addition to this, solving these challenges through the implementation of VK69 has proved to be very cost-effective, since upgrading the catalyst loading does not require any additional chemicals, does not generate any waste, and does not require any costly and extensive revamp.  

Finally, for plants that now have even more demanding requirements for emissions or production capacity, and have already installed VK69, there is a new option available, namely the combination of VK38+/VK69. This combination will allow sulfuric operators to achieve even higher conversion levels or to deal with specific bottlenecks that can be solved with extra activity. With the decarbonization and clean air trend of the present day, VK69 is indeed more relevant than ever.

A whitepaper containing real-life industry examples that show how operators have successfully used the VK69 catalyst to secure compliance, reduce costs, and increase their profitability and efficiency is also available by following the link on this page.

Explore the whitepaper here.