Case Study: Water Conservation Efforts Pay Off

Multifaceted worldwide initiative significantly reduces consumption.

By Julie O’Brien, Air Products

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The old adage what gets measured gets managed is a concept that is particularly true for water consumption at Air Products, Allentown, Pa.

Air Products consumes approximately 15 billion gallons of water each year at our facilities worldwide. We annually survey plants on water use as well as other environmental measures, and compare the results year-on-year to our environmental sustainability goals. The water data include intakes by source, discharges by destination, production volumes and contaminants (where collected). We then calculate consumption as intakes less discharges to the same source. For example, water that comes from and returns to a specific water body is not counted as consumption. This is particularly relevant to Air Products because much of the water we use is for plant cooling and goes back to the original source.

To evaluate performance against the company’s water goal, we subtract from the consumption the water required as a reactant or exported; this value is normalized by production so the results can be compared on an intensity basis.

In 2009, when Air Products engineers began centrally collecting water consumption data for more than 200 of our global facilities, opportunities to reduce water use quickly came to light. For example, by comparing expected and actual water use per unit production, we discovered leaking pipes at some older facilities; these were promptly repaired.

That same year, the company set a goal to cut consumption of controllable water — which excludes water used as a reactant or exported to customers as steam or water — on an indexed basis by 10% by 2015. Through plant efficiency improvements, facility-level assessments and use of recycled water, we met this water reduction goal four years ahead of schedule.

Improving Process Efficiency

The manufacture of hydrogen via steam methane reforming (SMR) accounts for more than half the water Air Products consumes each year. In the SMR process, water is used in two steps: to reform the methane to carbon monoxide and hydrogen, and then to shift the carbon monoxide to carbon dioxide. On a stoichiometric basis, 0.55 gallons of water are needed to make each pound of hydrogen.

Because the SMR reaction is exothermic, water also is required for cooling. The cooling towers at our plants have varying levels of efficiency and water loss as well as different discharge requirements. Overall water consumption for hydrogen production through SMR, including water used for in-plant cooling, is approximately 4.1–5.5 gallons per pound of hydrogen produced, based on data from the U.S. Dept. of Energy’s Lawrence Livermore National Laboratory [1].

SMR exemplifies the “water-energy nexus”— water is required to make hydrogen, which in turn is used to remove sulfur from crude oil to produce cleaner-burning fuels. Air Products’ energy efficiency, greenhouse gas emissions and water goals are all related through this nexus. Using a 2007 baseline, the company has set goals to both increase energy efficiency and reduce greenhouse gas emissions by 7% on an intensity basis at hydrogen/syngas (HyCO) and air separation facilities by 2015. By improving energy efficiency, our water consumption and greenhouse gas emissions will decrease on an intensity basis. We have made progress on all these goals, including cutting the amount of energy consumed per unit production at hydrogen facilities, resulting in lower water consumption on an intensity basis.

Another significant portion of the water consumed by Air Products each year goes for cooling air separation units (ASUs). In these facilities, air is compressed so cryogenic distillation then can fractionate nitrogen, oxygen and argon; in many cases, additional compression is used to liquefy products. This compression generates a significant amount of heat that is removed through water-cooled heat exchangers, necessitating cooling towers at each ASU. As at the hydrogen facilities, our engineers have improved the energy efficiency of the ASUs and brought new, more-efficient plants online, thus decreasing the company’s water consumption.

We also have initiated a series of plant-level water use reviews at representative facilities around the world. Done in conjunction with GE Water, these “water assessments” bring personnel from the two companies together to evaluate plant operations to identify opportunities to save water and reduce costs. During the assessment process, the team tours the plant, confirms piping and water flows, and pinpoints specific projects that can cut water consumption. By the end of the assessment, the team has come up with a list of recommended projects along with their estimated costs and benefits so Air Products can determine the next steps and develop action plans.

Through this program we have assessed most of our major HyCO and ASU facilities, including plants in the U.S., Canada, Brazil, the United Kingdom, Poland, Spain, the Netherlands, China, Korea and Taiwan. The assessment teams have identified ways to save on average 5–10% of the water being used at these plants. Recommendations for reducing water consumption typically include increasing cooling tower cycles, optimizing water pretreatment systems, capturing condensates and reject water from treatment processes, and recycling water. We share the results of these assessments company-wide through our plant process engineering organization so similar facilities can benefit from the opportunities identified.

Our work with GE Water builds on the two companies’ long-standing efforts to decrease costs associated with water use and treatment. For many years, GE Water has been our primary provider of water treatment services and chemicals and has had annual incentives to reduce consumption and costs. Through process improvement projects identified and implemented jointly by the companies, Air Products has saved millions of gallons of water and millions of dollars in associated water and treatment costs.

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