Mercury: a pervasive toxic contaminant
Fact: Removal of 1 kilogram of mercury from industrial flue gas results in more than 20 tons of contaminated solids.
Whether we like it or not, the world’s current industrial and energy production infrastructure still depends to a large degree on combustion that emits mercury. Mercury is a lethal pollutant, highly toxic to humans, and as we know from seafood health warnings, continues to contaminate the aquatic food chain that is a food source for billions. The Minamata Mercury Convention, a treaty formulated after the mass poisoning in Minamata Bay, Japan, was agreed on 61 years ago.
Mercury in coal, ores, and other raw materials is released to flue gases during combustion or smelting in boilers, kilns or furnaces. While much of the mercury comes from coal-fired power plants, a large amount also comes from coal-fired industrial boilers, natural gas plants, cement production facilities, and smelting processes used in the production of non-ferrous metals (lead, zinc, copper and industrial gold). Waste incineration facilities, which are growing rapidly, are also on the list due to heavy metal content in the waste stream.
The global international awareness of the problem and the risks of mercury have led environmental protection agencies worldwide to introduce stringent regulations and standards limiting mercury emissions. Emitting industries and processes are mandated to reduce or eliminate emissions entirely.
Current solutions: inefficient, and tons of contaminated waste
However, today the most commonly applied mercury control technologies suffer from very significant drawbacks. Typically based on combinations of activated carbon injection (ACI), filters and chemical additives, these techniques only remove 60-90 percent of the mercury, and they require large capital and operational expenditures as well as disposal of tons of contaminated byproducts.
At best, these methods simply redistribute mercury from one place to another, and the contaminated solids are often left onsite in large waste heaps.
New methods: 95% removal, no waste
A new solution from start-up Mercuremoval in Netanya, Israel, shows high promise, with a 95% mercury removal rate regardless of the amount of mercury in the flue gas stream. The company has a patented, cost-effective absorption material and separation technique that for every 1 kilogram of mercury removed yields just 1 kilogram of elemental mercury suitable for recycling into other products such as instrumentation and lighting. The separation technique allows the absorbent material to be reused in the same system.
The system has been deployed in a standard wet scrubber at trials at the Rutenberg Power Plant in Ashkelon, Israel, with the cooperation of the Israel Electric Corporation. The flue gas stream enters the scrubber in which a complex of ionic liquid and oxidizing agent is circulated. The mercury is oxidized and forms a stable complex in the liquid. The liquid is then regenerated through a simple process in which the metallic mercury swiftly precipitates from the solution and can be quantitatively separated and collected, while the absorbent liquid is regenerated and reused in the process.
The system removes all mercury forms, including elemental mercury, using a simple regeneration and mercury separation process. According to the company, the system can be can also be custom-developed and installed as a retrofit. It offers scalability and is applicable to a variety of industries, plants, and mercury-emitting processes.
The technology was developed by Professor Yoel Sasson and Dr. Zach Barnea, both from the Casali Institute of Applied Chemistry of the Hebrew University of Jerusalem. It was licensed under an exclusive worldwide agreement from Yissum, the technology transfer company of the Hebrew University.