ANNA 2019

CONFERENCE REVIEW

ANNA 2019

Highlights of papers presented at the recent Ammonium Nitrate/Nitric Acid (ANNA) Conference, held in September in Vienna.

Borealis was the host for this year’s Ammonium Nitrate/Nitric Acid conference, and so the venue was Austria’s picturesque capital Vienna, with an excursion to Borealis’ production site at Linz, 180 km to the west.

AN production from renewables

Production of ammonia and downstream products using renewable energy is a subject gaining increasing interest these days, and Stamicarbon looked at how this might be used to generate nitrates based on renewables. Joey Dobree of Stamicarbon took a 250-500 t/d calcium ammonium nitrate (CAN) plant as his baseline assumption, using ammonia produced from hydrogen generated by electrolysis and nitrogen from an air separation unit (ASU). The economic feasibility of such a project depends upon the cost of generating the hydrogen – and the costs of electrolysis continue to fall – and the availability of competitively priced alternatives. He showed that for a remote inland area, for example in Africa, the cost of transportation of fertilizers such as CAN from overseas can make local prices over $460/t, giving a plant based on renewables a 10-15% rate of return. It is also possible to produce ‘hybrid’ designs in regions where gas prices are high. Although these applications remain relatively niche for now, carbon taxes, falling electrolysis costs and economies of scale could start to make such plants economical outside niche cases.

AN safety

Safety remains very much at the forefront of AN production, and was the topic of several papers presented at the conference. Pieter Halliday introduced explosives safety body SAFEX International, which aims to spread best practice on the manufacture and use of explosives. SAFEX maintains an incident database updated by its members which now covers 20,000 entries dating back nearly a century.

Noel Hsu of Orica reviewed the science on ammonium nitrate detonation, and the effect of voids within the material, as well as the impact of chloride and other contamination – the latter with reference to a fortunately non-fatal explosion involving an AN tanker. Queenie Kwok of the Canadian Explosives Research Laboratory added some results from her own organisation’s studies on the reaction between AN and sodium salts, frequently found in contaminants.

But these are not simply academic concerns – Jose Henrique Guimaraes of Yara reported on an incident in Brazil with a truck carrying technical AN from the Cubatao plant. Smoke was reported from the semi-trailer on the way to the customer. Water was used to stop the smoke but the transporter requested a safety check from the manufacturer before continuing. It was found that a missing cover above an unloading port coincided with a burnt patch on one of the 50kg bags of TAN. An exposed metal edge had torn the bag and allowed organic material from previous loads (grain) to mix with the TAN. Friction and microbiological heating from mould on the soya grains had then generated enough heat to begin decomposing the AN! The application of water had stopped the self-heating and decomposition of the AN. Based on the incident practices for carriage of AN bags was changed.

The use of water to tackle AN fires was the topic of Frank Wolf of Apache Nitrogen, and why it was a very good thing. Indeed, the more water the better was his message, although preventing a fire from starting, via non-combustible construction, segregated storage areas with continuous monitoring and good housekeeping to prevent contamination of course remained the best policy of all.

German sensor company Grandperspective highlighted their infra-red gas monitoring camera packages, which can alert plant and storage area operators to decomposition of AN in real time, as well as emissions of ammonia or other dangerous gases.

Of course, AN remains vulnerable to the possibility of deliberate misuse, and Michael Whited of the Pentagon’s Joint IED Defeat Organisation gave delegates an update on ongoing international efforts to combat the misuse of AN fertilizer – and urea – for improvised explosives.

Catalysis

On the nitric acid side of the conference, several of the papers looked at catalysis of the ammonia oxidation reaction. Sumit Rao of Hindustan Platinum described methods of catalyst deactivation, including blanketing with impurities or contaminants, poisoning with inhibitors that decrease reaction rates, mechanical embrittlement and chemical alteration of alloy constituents, all leading to a loss of active sites. Calcium, magnesium, iron, aluminium, carbon and silica are all known issues with precious metal nitric acid catalysts. It is therefore crucial to make sure none of these are present in the process feed. In some cases it is possible to restore reactivity of catalyst and Mr Rao gave some examples of these.

Christian Goerens of Umicore showcased work his company had performed on enhancing the efficiency of nitric acid catalysts and reducing N 2 O production, in conjunction with thyssenkrupp and the Technical University of Darmstadt, as well as data analysis company Umesoft, which had progressed from computer reaction modelling to prototyping and lab and pilot scale experiments which fed back into the computer modelling studies. Lessons learned about the importance of gauze geometry have led to a new ‘twisted’ catalyst design which increases efficiency by up to 1% and reduces N 2 O formation.

Emissions control

Because of nitrous oxide’s large CO 2 equivalent value in terms of greenhouse gas production, reducing its production from the nitric acid industry remains a key concern. One paper described the work of the Nitric Acid Climate Action Group. The World Bank now operates a nitric acid climate auctions programme (NACAP), which supports price guarantees for eligible N 2 O emission reductions from nitric acid plants with existing or new abatement projects.

John Pach of JM ran through abatement techniques – JM has so far completed 61 N 2 O abatement projects worldwide in conjunction with Yara, with reductions equivalent to a total of 90 million t/a of CO 2 equivalent. Secondary abatement systems can reduce emissions by 95% but must have good gas mixing and distribution and sufficient mechanical integrity to ensure there is no shifting and by-pass of the catalyst bed.

Naveed Sukhera of Fatima Fertilizers in Pakistan gave some operator perspective, specifically with regard to an incident which led to an unexpectedly high pressure drop across his company’s Uhde EnviNOx reactor. An ammonia gas sparger was found to be damaged during inspection having reached the end of its operating life, and a mixer plate had sheared and stuck inside the feed pipe partially blocking the flow, leading to the higher pressure drop. With assistance from thyssenkrupp, new parts were fabricated and replaced the damaged components.

Mathias Rode of Covestro (formerly Bayer Materials Science) likewise reported on issues with a demister upstream of the NOx compressor in a nitric acid plant in China. Corrosion had occurred in the compressor housing and impeller and this necessitated the installation of a new demister.

Another real world issue came from Bas Tilborghs of Yara, who described NOx emissions resulting from back flow through a secondary air line at Yara’s Sluiskil plant in the Netherlands. A spurious trip in the steam turbine led to a turbo set shutdown, but a secondary air valve did not close quickly enough. Bas encouraged other plant operators to review their own check valves and safety logic circuits.