To schoolchildren, nitric acid will be all-too-familiar as one of the principal mineral acids which is essential when conducting many chemical experiments. On an industrial scale, however, nitric acid is recognized as a key compound in the production chain of chemicals and fertilizers such as urea, nitrates and phosphates.
That global demand for fertilizer – and hence nitric acid – is set to grow is an undisputed fact, being driven as it is by changes such as population growth, dietary changes in specific emerging markets, a reduction of available arable land, and increased demand for plant-based biofuel, etc.
This explains why countries such as Uzbekistan – known for both its cotton production as well as its extensive chemical sector - are keen to see investments made in modern nitric acid plants. Hence when Uzbekistan’s largest chemical company. JSC Navoiyazot, decided that a brand-new, large-capacity nitric acid plant was required, it awarded an EPC turnkey contract to Casale in Switzerland.
For an outlay of USD 216.6 million, Navoiyazot now benefits from a facility that produces 500,000 metric tons of nitric acid annually and is characterized by low energy consumption plus low emissions. An additional knock-on benefit has been the creation of some 120 new jobs.
From 304L to 321
One of the people at Casale who was involved in the Navoiy project was Flavio Pedon, the mechanical engineer in charge of the design of proprietary and key equipment plus follow up of manufacturing from the engineering point of view.
Speaking to SSW India & ME, Mr. Pedon was first kind enough to outline some of the plant’s technical features. “This is the fourth large-capacity nitric acid plant we have built using our NA2000 Dual Pressure technology, which was developed specifically to deliver energy efficiency and low emissions. Our technology aligned perfectly with the client’s requirements for a reduction in the amount of ammonia required to produce one ton of nitric acid and higher steam export. To give some supporting numbers, the plant needs just 280 kg of ammonia to make a ton of nitric acid, which is nicely below the plant’s design specific consumption of 283 kilograms per ton. In addition to low ammonia consumption this technology has also driven down emissions of NOX , N2 O and ammonia, contributing to safer plant operation.”
Asked about materials of construction, Mr. Pedon indicates that 304L (1.4306) stainless steel is probably the most commonly-used alloy for the construction of nitric acid plants worldwide. “Hence you will find 304L has been used throughout Navoiy for components such as such as piping, ducts, pressure vessels, heat exchangers, reactors, internals, etc. The plant makes use of all product forms, such as plates, pipes, tubes, forgings, casting, etc.”
"The absorption tower (with a five-metre diameter) was made completely in stainless steel by an Indian manufacturer
In addition to 304L other alloys can also be found at Navoiy, such as grade 2 titanium, plus stainless steel 321 (1.4541), 310L NAG – (1.4335) and 304LN (1.4311). Says Mr. Pedon: “their use was dictated by the prevailing corrosion conditions in certain areas. Hence grade 2 titanium is typically used in some critical heat exchangers, although usually in the tube side only given the high corrosion environment. 321 is used in internals and pressure vessels instead of 304L whenever more strength at high temperature is required. 310L NAG is typically used in some critical heat exchangers and reactors with high corrosion environment. Finally, 304LN can be used as an alternative to 304L when additional strength is required in say large columns.”
In terms of timing, construction started at Navoiy in 2018 with the plant entering into operation in June 2020. Once the severity of the Covid-19 pandemic became apparent in early 2020, all parties involved quickly took steps to ensure that the project would be properly completed without compromising safety. Nonessential personnel were therefore removed from the construction site, with engineering teams being quickly reformed at Casale’s offices in Switzerland and the Czech Republic. “We made effective use of the internet to keep the project on track, which was quite unique for an undertaking of this scope and size. We were joined online by key vendors in countries such as Germany, Italy and Spain. I believe that it is to everyone’s credit that the Navoiy plant was safely and successfully commissioned remotely,” concludes Mr. Pedon.
*Casale experts have prepared an extensive article detailing how the Navoiy plant was successfully commissioned and started up with remote assistance during the Covid-19 pandemic. Copies can be obtained from firstname.lastname@example.org
Meet Mr. Pedon
Mr. Flavio Pedon works as Nitric Acid Mechanical Technology Manager for Casale. As such as is the company’s reference point for technology from the mechanical design point. E-mail: email@example.com LinkedIn: search for ‘Flavio Pedon’
Mr. Flavio Pedon