Casale: The art of building a nitric acid plant

For the past 3 years, Yuriy Idrisov, Deputy Director of Casale’s permanent establishment in Uzbekistan, has been part of a comprehensive team of designers, planners, construction workers and engineers building a large-capacity, ultramodern nitric acid plant in the city of Navoiy. “One of the distinctive features is our use of an extended absorption column design, incorporating a closed chilled-water circuit to help us reduce ammonia slippage”, said Idrisov. “It wasn’t just a challenge from the technical side – we had to be organisationally prepared for anything related to both the COVID-19 pandemic and the plant itself.”

Modernising industry in the Uzbek steppes

This is the fourth large-capacity nitric acid plant built by the Swiss company Casale SA using its NA2000 dual pressure technology which is “designed for energy efficiency and low emissions”, according to Idrisov.

Casale was awarded the EPC lump sum turnkey project by the Uzbekistan chemical company JSC Navoiyazot. Early-work construction began in 2018, and thanks to a creative approach to commissioning during a national COVID-19 lockdown, the plant has been operating steadily since June 2020.

JSC Navoiyazot’s main product is mineral fertilizers based on ammonia, nitrogen-phosphorus or nitric acid. The company employs around 10 000 people.

The new plant, which cost US$216.6 million and produces 500 000 tpy of nitric acid, has created over 120 new jobs, and local specialists and resources were used during construction, with around 50% of the team coming from Uzbekistan itself. The project is part of a larger modernisation drive to increase production and reduce the environmental impact of the country’s chemical industry, a cornerstone of the Uzbek economy.

Designed for efficiency and environment

The plant’s centrepiece is a four-part compressor train installed by MAN Energy Solutions, concealed in an easy-to-spot bright blue building that looks like a toy cube in a mesh of pipes and cables. The train allows for higher rotational speeds while reducing the energy footprint – a major factor in the plant’s profitability. “Another distinctive technical feature”, added Idrisov, “is the use of a single ammonia oxidation burner, which simplifies the layout with an easier gauze management.” The company also used a simplified layout of secondary and tertiary catalysts to improve the plant’s abatement function.

“Our focus was on reducing the amount of ammonia required to produce one ton of the product and increase the steam export”, Idrisov explained. “So, we chose the dual pressure technology as a solution to ensure a low specific consumption of ammonia with the lowest possible emissions and to promote safe operation of the plant.”

The plant’s design specific consumption of ammonia is 283 kg/t. “At the moment, we’re better than this indicator because we’re consuming less than 280 kg/t… We’re equally better in terms of emissions. The requirement was to have less than 50 ppm emissions of NO_X gases and N₂O gases while remaining below 3 ppm for ammonia. The actual figures are 30 and 20 respectfully, with less than 1 ppm for ammonia”, said Idrisov.

The reduction in emissions is made possible by Casale's NA2000 dual pressure technology. Based on 50 years of development experience, the technology offers low operating costs with regard to specific ammonia consumption (as NH₃/MT HNO) and precious metals losses, while ensuring high specific steam/energy export. The successful completion of the nitric acid process in the Navoiy plant is of particular interest as the COVID-19 pandemic continues to delay or even halt construction projects around the world.

Read the article online at: https://www.worldfertilizer.com/nitrogen/12012021/casale-the-art-of-building-a-nitric-acid-plant/