The Middle East has seen a significant increase in the frequency and intensity of sand and dust storms in the past 15 years, according to a report by the World Metrology Organization.1 It claims the main source of sand and dust storms in the region is Iraq, where the flow of rivers has decreased because of a race in dam construction in upstream countries. This has led to the disappearance of marshes and drying up of lakes both in Iraq and Iran, with the sediments left behind creating the dust and sand.
A sandstorm consists of a massive amount of particulate in the air and has a significant effect on a person’s health, including serious respiratory problems. Industry operating in these conditions suffer as well. Cooling systems used by a manufacturing process of any type use air and water to transfer generated heat. Airborne contaminants get drawn into the cooling system and effectively block its “arteries,” resulting in, at the very least, inefficiencies in operation or, at worst, complete failure of processes.
“Contamination by smaller particulate and fine dust has seen a comprehensive review of filtration technology techniques for industries operating across the Middle East,” said Andy Evans, UK and Ireland manager for Amiad Water Systems.
“The problem has been that finer filtration brings with it limited available open surface area on the filter media,” he explained. It is this “open area” (i.e., holes or porosity) within the filter media that determines the dirt-holding capacity and the frequency of cleaning required.
The table below demonstrates the effect of finer filtration on the open surface area of a typical filter screen and shows the impact on dirt-holding capability. There are a few anomalies in the values as these will vary from manufacturer to manufacturer and as wire diameters change, but this is a general guide.
“To combat the problem, we have developed multi-layer screens,” said Evans. “Effectively, by multi-layering we are providing a significantly larger open area.” However, he explained, even with this inherent solids-holding capability, when cooling systems are subjected to the conditions of sandstorms, filters can still become compromised. “Typically under sandstorm conditions, filter systems will be isolated or become overwhelmed. Therefore the actual design of a filtration plant must take into account the effect of a smaller open filter area.” The result of which, he added, can seem to the inexperienced a considerably oversized plant for relatively small flows.
“Putting our design to the test, we have recently been commissioned by a Middle East producer of industrial gases to design and build a 6-off, complete skid-mounted, two-stage filtration plant with a removal capability of 20 microns, manufactured to meet rigorous ASME compliance,” he said.
The plant will be designed to filter a 10 percent stream of the cooling process associated with the gas production. It will be located outside in order to be in close proximity to the process and enable it to directly couple to an existing pipework system.
“On the plus side, the plant will be shaded from the high ambient temperatures experienced in this region,” said Evans, “but otherwise it will be subjected to all the elements that this environment delivers whilst still operating 24 hours a day, 365 days a year.”
It’s a considerable challenge to meet, he noted, considering construction, compliance and a 20-bar pressure design.
Evans explained that elevated pressures bring backwashing complications as high pressures are discharged to atmospheric pressure during the backwash process. “Analysis has shown that if we target 20 microns, this will remove the majority of the sand that we expect will be collected,” he said, “and a continual recirculation will produce a filter cake that will further improve removal performance.”
The filtration technology will combine a two-stage approach: a 20-micron screen system incorporating a special spring-loaded nozzle cleaning system designed to remove organic material and very fine sand; and a high-efficiency hydrocyclone, which serves as a pre-filter during normal operation and acts as a primary filter during periods of significant solids, such as those expected during a sandstorm.
As sandstorms can happen without much warning, an integrated control system will monitor solids loading on the 20-micron screen and automatically remove and insert it from the system during extreme conditions. This process is all automatic with the telemetry of the system continuously reporting system status back to the engineers. This bespoke filtration technology is expected to be operational by the end of 2016.
About the Company: Amiad Water Systems UK Ltd. is based in Swansea, Wales, and is a subsidiary of Amiad Water Systems Ltd., a leading global producer of water treatment and filtration solutions. Amiad Water Systems UK provides premier filtration expertise for commercial, industrial, manufacturing and municipal water systems throughout the UK. For more information, visit www.amiaduk.com.
References
1. Khadka, Navin Singh. "Middle East worst hit by rise in sand and dust storms," BBC News, June 17, 2016, http://www.bbc.com/news/world-middle-east-36553594.
