Chemical Processing-August 2008

Worth its salt One abundant but underutilized source of water is the sea. So, it’s little wonder that interest in desalination plants and technologies is strong. Dow, for one, is targeting desalination, both of seawater and brackish water (as well as water reuse applications and small, distributed systems for local use). “In general, the cost of desalinated water has fallen dramatically — by more than half — in the last 15 years,” says Chuck Martz, global marketing director for Dow Water Solutions in Edina. “So demand for the reverse osmosis (RO) and nanofiltration (NF) membranes we manufacture for use in desalination is growing rapidly on a global basis. Desalination will have double-digit growth for the foreseeable future,” he adds. In mid-June Dow announced an $88-million expansion at the Edina facility — the third investment there in eight years. It will lead to greater output of advanced technologies such as RO and NF membranes and automated production of 16-in.-diameter elements. Dow expects to launch these larger elements at the Aquatech Amsterdam exhibition that starts at the end of September. “These are important because they cut the capital cost of a desalination system by 10–20%,” notes Martz. Dow, on July 10, announced plans to build a $15-million Water Technology Development Center at its Tarragona facility by the Mediterranean Sea in Spain. Due to open next year and employ 25 researchers, it will have ready access to seawater and will be able to obtain brackish water, industrial wastewater and treated river water. The idea is that the center will help Dow understand how to achieve the best performance and lowest operating costs for treating different water types. At the same time, the company has launched two new seawater RO elements. The first boasts better rejection of boron, a trace contaminant that causes a variety of different problems. The World Health Organization also warns against raised levels of boron in potable water. The second targets energy use, which is the biggest cost associated with desalination. Energy savings realized depend on temperature, water salinity, design flux, fouling tendency, efficiency of pumps and motors, and use and efficiency of energy recovery devices. In a typical seawater system, the savings are roughly 0.3 kWh/m3 and energy consumption of the membrane stage could be brought down from roughly 2–2.5 kWh/m3 to 1.7–2.2 kWh/m3. In selected scenarios (low temperature, higher fouling tendency, inefficient pumps, no energy recovery), the saving is more in the range of 0.6 kWh/m3. With an energy cost August 2008 chemicAlprocessing.com 28 of 5–10¢/m3, this is a savings of 1–4¢/m3. “The tradeoff is slightly elevated permeate salinity. In many cases the salinity will still be within WHO expectations.” And this highlights the desalination crux: “We are always trying to make the membrane more permeable in RO, but at the same time reject unwanted salts. So we are always looking for new chemistries. What industry wants is to meet the required specification, whether for potable water or ultrapure water. Once you can meet this, you then look at the cost of water production. So we work with companies such as Siemens, Veolia and many others to try and find solutions that optimize the cost of the water coming out of the system,” says Martz. targeting industry Pall, East Hills, N.Y., also sees industrial water treatment as a growing business. “In the last year we have set up a dedicated engineering applications group within our industrial water section. So we’re definitely gearing up for it,” says Thomas H. Wines, senior marketing manager. In particular, Wines points to growing interest in the company’s Integrated Membrane System (IMS) technology. “The point here is that a technology originally developed for municipal drinking water has moved into the industrial water sector and is a growing business,” he explains. Origin Energy, one of the leading energy providers in Australia, New Zealand and the Pacific, is an early IMS beneficiary. One of the company’s main products, coal seam methane (CSM), is expected to produce 90% of the total gas required in Queensland, Australia. To recover the gas, however, requires water to be pumped from the coal seams to reduce the pressure and allow large volumes of gas to flow. This water traditionally has been difficult to treat with membrane technologies because of its wide variety of contaminants. To add to the challenge, the company’s Spring Gully development near Roma in central Queensland is in a drought-affected region of Australia where water management is especially critical. So Pall was asked to develop and trial an IMS that utilizes microfiltration (MF) and RO systems specially designed to deal with CSM water. Following success with this, Origin early in 2007 contracted Pall to supply a full-scale IMS facility at Spring Gully. This IMS comprises four MF racks, each containing 56 0.1-µ Microza modules, an RO system, a prestrainer, chemical dosing, compressed air systems, plus interconnecting pipework and motor control centers. Although implementation was complicated by http://chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing-August 2008

Chemical Processing- August 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Protect your Plant What’s on Tap for Water? Keep Operations Safe Polystyrene Plant Gains Extra Output and More Process Puzzler Plant InSites Equipment & Services Adlits Product Spotlight/Classifieds Ad Index End Point

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