Getting up a full head of steam

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The boiler makeup water sector has been simmering along of late. It’s about to come to the boil, says Gord Cope.

Love, says the poet, makes the world go round. But steam, says the engineer, illuminates it. Over 80% of the electricity produced on Earth is generated using a boiler to create steam, which in turn generates watts of power. Boilers aren’t used solely in power plants, of course; in addition to heating homes and offices, refineries use them to distil volatile fractions out of crude, chemical plants rely on them to crack and fuse molecules, and pulp and paper mills boil wood chips to make paper.

But power generation is the largest market. The US Energy Information Administration (EIA) estimates that there are approximately 3,700GW of generating power in the world and plant operators need a lot of chemicals and pure water equipment to keep boilers running. Freedonia Group, a consultancy, places the water filtration, clarification and chemical conditioning market for power plants at $5.4 billion in 2007.

The McIlvaine Company, meanwhile, estimates the worldwide power plant market for pure water hardware to be approximately $700 million, pushing the total value of the market to more than $6 billion.

Make-up artists
Suppliers of pure water services are a mix of regional and multinational players. In Europe, Veolia (through Elga Process Water), Suez and Christ Kennicott Water Technology are prominent. “The drive for reduced CO2 emissions is fuelling the development of supercritical power stations and ‘clean coal’ technologies,” says Chris Burleigh, international sales manager for Christ Kennicott.

“This translates into either new-build or the replacement of older boiler technology with modern, up-to-date super-/ultracritical once-through boilers. Higher pressure boilers demand ultrapure water, so we are seeing growth in the area of boiler water treatment and condensate polishing.”

In North America, Ecodyne and Aquatech are two significant suppliers of original equipment. “We’ve been extremely busy, mostly in power,” says Paul Kitchen, sales manager for Ecodyne. “We serve the large industrial market, 1,000-5,000 gpm (380-1,900m3/d). We do 50-60 new projects each year; it’s all custom-designed systems, in the $1.5 million range.”

Two major companies operate worldwide in a broad range of water services: GE Water & Process Technologies, and Siemens Water Technologies. “We’re the leader,” says Rod McNelly, director of sales for Siemens Water Technologies’ industrial capital group, which earns about $2 billion annually from water-related services. “We have hundreds of build, own, operate, maintain (BOOM) projects, and several thousand installations. We have thousands of customers worldwide.”

Thanks to overbuild of natural gas power plants in the US and other developed countries, new-build for pure water facilities has been relatively flat recently, holding the growth of the sector at less than 5%.

For the past few years, the boiler water market has had to rely on replacement of equipment. “In a lot of industrial plants, pre-treatment systems are getting old,” says Chuck McCloskey, mobile business
development manager for Siemens Water Technologies. “They’re starting to show their age; they were getting more costly to operate and maintain. Many were put in during the 50s and 60s and have old, analog controls.”

But electrical generation is in high demand in other regions of the world. Globally, the EIA foresees the need for almost 3,000GW of new generation capacity over the next 20 years, equating to approximately 6,000 new plants.

Most of this growth will be in emerging markets such as China and India, where economies are expanding at rates of 8-10% annually, placing huge strains on current capacity. Aquatech, based in Pennsylvania, is already seeing international action: in the last year, over half their power projects have been outside of North America. “Power is a very important market for us, both for original and replacement parts,” says spokesperson Amy Bloom. “The Middle East is very hot these days, as is the Caribbean.”

Western Europe, Japan and the US are considered mature markets, but even in developed countries, demand for electrical energy is soaking up excess capacity, and talk of greenfield energy projects is once again heating up. “There are 154 coal-fired electrical generation plants planned for the next three years in the US,” says McNelly. “That’s 93GW, worth $137 billion. And there’s even more further out.”

Light my fire
The concept of the steam boiler has been around for several thousand years, but it wasn’t until the 18th century that James Watt and others harnessed the power of expanding water vapour to produce mechanical energy. The two most common types of boilers are water-tube boilers (where the heat source is outside the tubes and the water to be heated is inside) and fire-tube boilers (where the heat source is inside the tubes and the water to be heated is outside). Both heat the water until it boils at 100˚C and expands to 1,600 times its volume. Because steam contains a tiny proportion of water, it is then generally passed through steam-purifying equipment, which removes remnant boiler water.

In some cases the steam is heated to a supercritical stage (over 3,200 psi), then introduced into a turbine, which rotates a generator to produce electricity. Spent steam is then sent through a cooling tower to condense and is pumped back to the boiler.

Since power plants use so much water (a UK Department of Trade & Industry study reckoned that, in developed countries, 40-50% of water abstracted is used in electrical generation), every effort is made to condense and recycle it. Some is lost, however, usually due to leaks in the system. Total dissolved solids (TDS) within the boiler water begin to concentrate, and quickly rise to levels above 5,000 ppm. High TDS and alkalinity in boiler water can decrease the efficiency of steam-purifying equipment to the point where the water levels become too high for efficient use of the steam.

Excessively high levels of TDS in boiler water can also lead to serious contamination complications. The steam that enters a turbine can contain a limited proportion of boiler water without doing any harm (up to 3%, or approximately 150 ppm, when boiler water is at 5,000 ppm TDS).

Higher levels, however, can cause several problems. Steam contaminants can form deposits in superheaters, control valves and turbines. These deposits can cause overheating failures. Deposits in the turbine can also reduce its efficiency and capacity. Further down the line, in condensate systems, caustic contamination can cause lines to corrode and burst. Rising TDS levels in boiler water are controlled through the use of blowdowns, where boiler water is periodically drained. In some systems, blowdown and leakage can account for 10% of the system volume. Replacement, or makeup water is drawn from three major sources: surface water, groundwater and seawater.

Seawater is high in TDS, around 35,000 ppm. Groundwater TDS levels are much lower, but this source can contain significant levels of iron, silicon and manganese. Rivers and lakes are the preferred sources as they contain the lowest levels of TDS, although they still have worrisome levels of suspended solids and dissolved organic matter.

Typical makeup water quality requirements are strict: specific conductivity must be less than .2 microSiemens/cm (μS/cm). Sodium and potassium levels must be less than 10 μg/kg (10 parts per billion), silica less than 20 μg/kg, iron less than 20 μg/kg, copper less than 3 μg/kg and carbon less than 200 μg/kg.

The two main types of water purification system for large industrial use are IX and RO. Ion exchange (IX) is the most common water makeup treatment system, purifying water by filtering it through plastic beads that are chemically treated to adsorb positively charged cations (such as sodium) or negatively charged anions (such as chlorine). When the beads have reached their capacity, they are recycled at special regeneration facilities. RO (reverse osmosis) produces pure water by forcing it under high pressure through a semi-permeable membrane. Impurities are confined to one side, while pure water passes through to the other side of the membrane.

Both systems have their advantages and disadvantages. Reverse osmosis is good for higher TDS loads. “As a rule of thumb, if you have over 500 ppm TDS, you go RO,” says McNelly. RO removes the high ion load, as well as dissolved organic matter and colloidal silica.

Removing the latter two in particular is critical in systems that inject boiler feedwater for steam attemperation or desuperheating. RO cannot remove more than 99% of foreign material, however, even with a double pass system, and it requires microfiltration and chemical pretreatment, including acids to reduce carbonate scaling, oxidizing biocides to reduce bacteria fouling, and dechlorination with sodium bisulphate.

Ion exchange is the preferred and economical choice for low TDS. Capital and operating costs are generally lower and a two-pass system reliably produces high quality water. Drawbacks include handling and neutralising the acidic and caustic solutions needed to regenerate the cation/anion exchange resins. IX systems can also lose effectiveness if raw water TDS levels fluctuate seasonally, or increase permanently.

As the price of RO has come down, primarily through research and economies of scale, operators have moved towards mixed solutions. “New generation systems include pre-treatment, then RO, then either IX for polishing or second pass RO,” says McCloskey.

Pretreatment with coagulants and granular filters is being supplanted by polymeric membrane systems, which remove virtually all suspended solids and some colloidal matter. Reverse osmosis then removes 97-98% of TDS, which is good for low pressure boilers.

“You need a second pass RO or IX polishing for high pressure boilers, which reduces the water to less than one microSiemen conductivity and 10-20 ppb silica,” says McCloskey. The combined process reduces energy, space and chemical needs, while enhancing versatility and water quality. A microfiltration pretreatment, RO plant and IX polishing system capable of treating 2,400m3/d costs approximately $3-5 million installed. Operating costs, excluding power, can range from $3.60- 7.20m3/d.

Much current research and development is being directed at improving water purification equipment. The robustness of membrane microfiltration, used in pretreatment, is being increased to handle greater load variability. RO membrane technology is moving toward lower fouling composite membranes with higher salt rejection rates, which lowers pressure and energy requirements.

A relatively recent advance in ion exchange systems is significantly reducing the required amount of regenerants, the acids and bases used to restore the cation and anion resins used in demineralization.
Continuous Deionization (CDI) is an IX membrane technology in which cation and anion resins are impregnated into a membrane. A small amount of electrical charge is then applied across the membrane.

TDS ions are taken to the reject stream and discharged continuously. In combination with RO, CEDI produces high quality water, with several benefits. “It has a smaller footprint and doesn’t use chemicals
to regenerate,” says McNelly. “Capital costs are higher, but operation is lower because you don’t replace the resins and you don’t have chemicals.”

Full steam ahead
As the price of energy and other operating costs rise, boiler owners are seeking out various ways to control costs and increase efficiency. “People are tightening up their systems, fixing leaks so there’s less steam loss, and ensuring there’s more condensate return,” says McCloskey. Several more trends are emerging:

• Aging water purification systems are being updated. “They are going to the next generation,” says McCloskey. “Generally, that means RO is replacing ion exchange.”

• The general quality of boilers is increasing. “When Enron and Calpine were around, they built plants (cheaply) and sold them off,” says Kitchen. “Power customers are now more quality-focused and specification-driven.”

• Operating costs are being reduced through less frequent blowdowns. “Blowdown water contains a significant amount of energy,” says McCloskey. “The less blowdown water, the less energy needed.”

• Operators are using higher quality makeup water. “This is due to higher pressure boilers and higher efficiency power plants, which reduce CO2 output,” says Burleigh.

• Water purification plants are getting smaller. “New plants are being put in at a higher rate, but it’s tempered by the fact that people are making higher quality make up water, so you need less,” says McCloskey.

• The ubiquity of acid and alkali regenerants will gradually decrease as combination systems become more common. According to a study by GE, RO pretreatment ahead of IX reduces ionic load and regenerant levels by 90-95%.

• Clients are moving towards one service provider. “Customers with wastewater, reuse, recycle, reclaim needs want to consolidate their processes and decrease the amount of vendors,” says McNelly. “We are present in these areas, so we have a bit of a leg-up.”

But perhaps the most significant trend in the boiler makeup water sector is away from permanent facilities toward mobile units. Two companies, GE and Siemens, operate a combined fleet of over 1,400 mobile water purification units that can be driven or towed to virtually any part of North America and Europe within a day. “We can reach 90-95% of North America within two hours,” says McNelly.

The units themselves come in two forms: trailers that can be towed down highways by semi-trucks, and skids, which are built into standard cargo container units and can be transported to site on ships, trains and lorries. The two most common systems are RO and IX. Typically, units are built to process 200 gpm (45m3/h), although 400gpm (90m3/h) units are not uncommon, and some very large filtration trailers can process 1,600 gpm (360m3/h). Most mobile business is now in the power industry, where temporary systems are used to test new or re-conditioned boilers before they are brought online, to back up permanent facilities while they undergo refurbishment, or when an emergency arises from breakdown or unexpected changes in raw water quality.

Currently, the fleet is growing by about 7-8% annually, primarily to service North America and Europe. As the power sector deregulates, however, utility operators are increasingly moving towards reliance on mobile units where capital versus rental costs are favourable. New regions are also being considered. “Any place that has a large industrial base: refineries and power plants, there’s an opportunity,” says McCloskey.

While the power sector is currently giving make-up water a much-needed boost, the sustainable fuel movement, designed to protect the environment, hovers on the distant horizon like a cloud. “No one knows the impact of the trend to limit greenhouse gases and fossil fuel use,” says McCloskey. “Wind farms and solar (electrical) panels have no need for water.” On the other hand, biologically generated fuel is an area of sustainable energy that is already providing a bright spot.

“Three main areas for us are food & beverage, power and general industry,” says McNelly. “Food & beverage is big because of ethanol and biodiesel production.”

In the meantime, pure water suppliers are focusing on quality and service. “Our customers are looking for energy efficiency, reliability, and low operating costs,” says Ecodyne’s Paul Kitchen. Delivering what they want appears to be the key to success. “We’re seeing 10% growth.”

Make-up water: facts and trends
• Over 80% of the electricity produced on Earth is generated using steam boilers. Other large commercial boiler uses include refineries, petrochemical plants, pulp and paper mills.

• The water filtration, clarification and chemical conditioning market for power plants amounts to $5.4 billion. The worldwide power plant market for pure water hardware is approximately $700 million. Growth has averaged around 5% for the last few years, primarily due to replacement requirements.

• Electricity demand, especially in developing countries, is forecast to expand worldwide capacity from 3,700GW to 6,400GW in the next 20 years. This is expected to accelerate growth in the makeup water market to 8-10%. Other sectors with high growth potential include oilsands, as well as ethanol and biodiesel production.

• Operators are moving towards higher- quality boilers to reduce energy and operating costs and to increase reliability and efficiency.

• Operators are moving toward mixed systems, such as RO/IX and RO/CDI, to produce higher quality makeup water. A combined microfiltration pretreatment, RO/IX system capable of treating 100m3/h costs approximately $3-5 million. Operating costs, excluding power, can range from $0.15-0.30 m3/h.

• Operators are moving towards mobile water treatment systems to reduce capital costs and increase flexibility of water supply.