Conservation: Water Wins Wider Attention

Chemical makers strive to cut consumption and improve treatment

By Seán Ottewell, Editor at Large

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A combination of tougher regulations and the need to manufacture in water-stressed parts of the world is spurring chemical companies to focus as never before on their water usage strategies. One effect of this is that water optimization technologies originally developed for the power industry increasingly are gaining traction in the chemical industry. At the same time, chemical manufacturers such as Bayer, BP and Dow are developing their own, sometimes nonconventional, approaches.

GE Power & Water, for one, is finding growing interest outside the utility industry for its technology — vertical-tube falling-film brine concentrators and evaporators (Figure 1) that can recycle wastewater into a high purity distillate suitable for boiler and cooling tower makeup, flue-gas desulfurization blowdown, NOx control and process use. According to the Trevose, Pa., firm, 15 to 20 years ago, 80 to 90% of demand for this kind of technology came from the power sector. Today, that figure is around 10% as demand rises in non-conventional oil and gas development, chemicals and other sectors.


“We’ve seen increasing demand from the chemical sector, particularly in the face of regulatory changes covering water use and wastewater discharge. Demand is strongest from companies located in areas where there is high population density and water stress — so, for example, much of the current demand is from companies in India and China in the chemical processing and coal-to-chemicals industries,” says Bill Heins, general manager, thermal systems — water and process technologies, GE.

He cites the example of a new Lanxess chemicals and intermediates plant in India. That site also uses GE’s zero-liquid-discharge crystallizer technology to reduce the brine concentrate to a dry solid.

The increasing popularity of evaporation for wastewater treatment is a sure sign of changing times, Heins believes. With certain notable exceptions such as steam-assisted gravity drainage heavy oil recovery, you typically wouldn’t put in an evaporation system solely for economic reasons, he explains.

“Reverse osmosis (RO) is less expensive per m3 of water treated, unless you have a highly saline, contaminated wastewater stream where RO is not technically viable. In the chemical industry, we are typically seeing waste streams from processes that are very hard to treat due to highly scaling constituents and high levels of organics and total dissolved solids. We can recover and recycle the water from these,” Heins notes.

An added advantage is that GE can treat mixed wastewater streams from different processes such as boiler blowdown, demineralizer regeneration waste, RO reject and chemical processes. Such integrated solutions often include wastewater preconcentration with membranes prior to thermal treatment.

The company currently is working with two clients to develop the next generation of thermal technology. It particularly is focusing on optimizing the integration of evaporation technology with different waste-treatment methods such as membrane separation, electrocoagulation, and physical-chemical treatment. “Our focus is on lowering their capital cost, reducing their power needs, maximizing reliability and reducing wastewater volumes as much as possible. Even a small change in water recovery results in a large impact in waste volume. For example, increasing from 98 to 99% water recovery at the tail end of the process means cutting the amount of water discharged in half. So from the user’s perspective, it means better water quality and better, more-efficient waste recovery,” notes Heins.

Another innovation is the introduction of a mobile evaporation unit. Originally designed for use by the unconventional gas industry, it now is finding wider applications — including with chemical companies that have waste ponds that need processing or that have filled more rapidly than expected due to high rainfall. GE is considering expanding its fleet in the face of growing demand.

MODULAR CONCEPT
Meanwhile, Bayer, Leverkusen, Germany, has developed a systematic and comprehensive process analysis called Resource Efficiency Check to uncover potential reductions in resource consumption, emissions and waste.

This modular concept enables the company to focus on specific issues relevant to production plants, for example raw materials’ use, packaging waste and water consumption. It also helps to identify possibilities for process-oriented optimization in boosting yields, recycling, utilizing byproducts and treating wastewater or waste air, so that these potential savings can be fully exploited.

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