Wally Schaefer, Jorvic Vital and Melissa Callejo, Nalco Water, USA, explain the importance of heat exchanger monitoring data in enabling the ammonia plants of the future.
For almost 100 years, the nitrogen processing industry has utilised data to help optimise production. Data continues to drive investments and process efficiency as decision makers work with engineers to troubleshoot problems and maximise production. What differentiates the past from today is how fast plants can leverage data to drive positive outcomes.
‘Plant of the future’ solutions include a comprehensive view on how operations are utilising real-time, online tools to predict the performance of critical heat exchangers, prevent unscheduled downtime and prolong asset life and production runtime, ultimately delivering a step-change in reliability and profitably in the new digital world.
Under design conditions, heat exchangers should provide reliable duty and a long service life with little or no maintenance. However, plants commonly run over operating design and cooling systems come with numerous mechanical, operational and chemical challenges depending on the water source, configuration of the system and type of heat exchanger.
Corrosion, whether velocity-induced or under-deposit pitting, shortens asset life or, in the worst case, can result in unexpected loss of production. Biofouling creates an insulating layer, resulting in a loss of heat transfer efficiency. The loss of heat transfer efficiency means that somewhere else in the system, additional energy is required to make up for the shortfall.
There are many root causes of heat exchanger problems and most are preventable if detected early, so corrective action may be taken. Providing a holistic, data-driven, performance management programme for critical heat exchangers can quickly activate a response required to optimise reliability, asset protection, and total operating costs.
OMNI™ Total Heat Exchanger Performance combines in-depth system audits, 24/7 monitoring, unique diagnostic tools, and consultative service that optimises heat transfer and guarantees reliability. OMNI provides new insight into process performance and can help deliver reliability and profitability.
ResultsThe following case studies illustrate how OMNI proactively utilises data and provides bottom-line savings by early detection and proactive response to declining heat transfer performance.
Case study 1
A real-time heat exchanger key performance indicator (KPI) showed a steady decline in U-Value, a loss in heat transfer efficiency. A quick investigation started with examining factors contributing to this event.
Water chemistry data was quickly correlated and showed very low chlorine residuals in the cooling water return and a rise in microbiological counts. This signalled that the amount of bleach being added was not meeting system demand. After consulting with plant operators, it was agreed to slowly increase the bleach dosage by increasing the oxidation reduction potential (ORP) set point to improve microbiological control and eliminate the biofilm layer in the heat exchanger.
Biofilms are much more heat insulating than typical mineral scales. In fact, biofilms can be four times more heat insulating than a calcium carbonate scale of similar thickness. The reason biofilms reduce heat transfer so much is microorganisms and the extracellular products they secrete are largely made up of water, which has a very high heat capacity.
As shown in Figure 1, the impact of an effective and quick correlation of performance data with microbiological treatment indicators was clearly demonstrated as U-Values quickly improved. By restoring and maintaining U-Value performance, the plant avoided a projected cleaning date and will be able to extend its production run until the scheduled maintenance turnaround.The avoided cost of an unexpected five-day outage to clean this critical heat exchanger is US$2.4 million (US$1.5 million in energy and US$0.9 million in gross margin production opportunity).
Read the article online at: https://www.worldfertilizer.com/special-reports/17102018/key-to-the-future/
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