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Category: Outlook & Reviews

A new focus

At the time of writing this editorial, the World Economic Forum was having its usual annual meeting in the Swiss resort of Davos. Prior to this year’s meeting, as usual the WEF had produced its annual Global Risks Report to serve as a talking point for the meeting. While some of the risks were as usual political and economic, from proliferation of weapons of mass destruction and the “retreat from multilateralism” to growing inequalities of wealth in the developed world and “domestic political polarisation”, for the first time in the organisation’s history, the top five global risks in the report ranked by likeliness – which looks at potential global pitfalls over the next 10 years – were environmental. Perhaps with the pictures of Australia’s bush fire season fresh in their minds, the 750 experts ranked extreme weather events as the most likely, but climate change, biodiversity loss and sustainability in agriculture all ranked highly.

Problem No. 58: Should liquid ammonia be drained to the ammonia water tank or vent stack?

Liquid ammonia is one of the feeds to the urea plant. It typically comes from the ammonia plant at a pressure of about 20 bar. In the urea plant this liquid ammonia is further pumped up to synthesis pressure conditions, sometimes after passing through a buffer tank, a heater and/or a filter. According to the ammonia phase diagram, when liquid ammonia flashes to atmospheric pressure temperatures can drop to as low as -33°C under worst case conditions. In case one or more of the above mentioned items of equipment needs to be drained for maintenance, a decision needs to be made where to drain this liquid ammonia. In a urea plant the options are the ammonia water tank or the vent stack, but which is best option?