Electricity / Water/steam

Plants Strike Down Energy Inefficiencies

Large chemical manufacturers achieve improvements on many fronts

By Seán Ottewell, Editor at Large

Higher energy efficiency ranks as a top priority in many chemical makers’ efforts to enhance sustainability and competitiveness. As the ongoing experiences of companies such as DuPont, AkzoNobel and Eastman show, improvements can come in a hugely diverse number of ways, from process redesign to better lighting.

For example, DuPont, Wilmington, Del., made a significant process change in the Delrin Chemical Area (DCA) at its site in Dordrecht, the Netherlands (Figure 1), which is home to nine manufacturing plants where refrigerants, synthetic resins and powder coatings are produced. The DCA is the largest consumer of steam at the site. One of the main steam consumers in the DCA is a concentrator column that reworks a number of recycle formaldehyde/water steams to give a formalin solution for re-use in the Delrin (an acetal resin) process. The excess water goes to a waste treatment facility.

“To reduce the energy consumption of the concentrator column, a project was started to operate the concentrator column in a more-energy-efficient mode,” explains Eelco de Visser, operations supervisor, Delrin compounding.

A simulation prompted a proposal for a process change — to split the recycle streams of aqueous formaldehyde that were collected in a feed tank and then fed to the column. These recycle streams come from various sources and vary in formaldehyde concentration. The largest volume stream, the “extraction tails flow,” has the lowest formaldehyde concentration (1.5–2%). The remaining recycle streams have much higher formaldehyde concentrations, ranging from 10 to 20%. The revision involved feeding the low-formaldehyde-content stream separately at a new, lower feed point in the concentrator column.

The modified process has been in continuous operation for over a year now with optimization still ongoing.

The upgrade has reduced steam consumption in the concentrator column by 16,7000 tons/yr with a saving of €418,000/yr ($466,000/yr). Substantial savings also have come from the associated decrease in CO2 emissions. “The total savings overall add up to €466,000/yr [$520,000], all for an invested capital of €436,000 [$487,000],” adds de Visser.

DuPont’s Spruance plant in Richmond, Va., which has been in operation since the 1920s and today manufactures textile fibers, also has achieved substantial energy savings as part of its efforts to cut emissions. The site revitalized its energy conservation/efficiency program through participation in the certified energy auditor training program,” notes John Kane Jr., principal consultant for DuPont Engineering Technology/Energy Engineering. Energy savings are estimated to have exceeded $4 million over the last five years.

Going Beyond The Fenceline

In Grindsted, Denmark, DuPont Nutrition & Health was screening possible energy saving projects for its site when it discovered a major potential win-win situation.

Surplus heat from production was being sent to cooling towers (Figure 2). The energy team decided to make better use of this surplus heat by selling it to the Grindsted electricity and heating plant (GEV), which delivers heat and electricity to private households and other buildings for water and space heating during winter.

“District heating is common in most cities in Denmark as they are densely populated, with little sprawl. This makes it possible to produce heat efficiently at combined heat and power plants and subsequently supply this to customers through a network of insulated pipes,” explains Martin Kirstein Madsen, Grindsted site manager.

The DuPont plant now supplies an estimated 12,627 MWh to GEV, enough to power 900 homes. It also saves GEV 1.2 million Nm3/yr in natural gas use. This translates to an annual reduction of 2,700 tons in CO2 emissions at GEV and a decrease of 70 tons at the Grindsted site.

“This project shows that it is possible to find win-wins for both the economy and ecology. Furthermore, it is an example of industrial symbiosis where a byproduct initially perceived as waste in one company can be turned into a valuable resource input for another company,” adds Madsen.

Diverse Efforts

AkzoNobel, Amsterdam, the Netherlands, does not have a specific energy target but tracks energy use with a metric called the Eco Efficiency Footprint, which incorporates nine parameters, one of which is energy used per ton of product.

Peter Nieuwenhuizen, AkzoNobel’s RD&I director specialty chemicals, Utrecht, the Netherlands, cites an operational eco-efficiency program carried out at the company’s surface chemistry plant in Stenungsund, Sweden. The ethylene oxide manufactured there goes into a variety of products including detergents, asphalts and mining chemicals.

The program has focused on two of the main variable cost drivers at the plant: primary steam consumption and efficiency of raw material use.

Nieuwenhuizen explains: “We took an integrated approach involving many people across the business. Specifically, this included using simulation models and plant tests to investigate the lowest possible reflux and steam consumption on individual distillation towers at different production levels. It was essential to ensure that product quality would not be affected. We gave this new knowledge to distributed control system operators and engineers and then provided them with live — i.e., real time — numbers, which were displayed on screens showing savings per hour/year. We used visualized KPIs [key performance indicators] wherever possible in meetings to drive the transformation needed.”

The program has resulted in variable cost savings of €3.8 million ($4.3 million) and reduced CO2 emissions by 11,650 tons so far.

Meanwhile, the company’s Mons, Belgium, polymer chemistry plant is saving energy thanks to a new two-step incinerator with an extra unit to reduce NOx emissions to below the level achieved with standard units, and a wireless sensing system to monitor and control storage tank temperatures. The incinerator is expected to cut NOx emissions by 80% to 20 tons/yr while the improved control enabled by the sensors has significantly decreased steam consumption. “The accumulated energy savings from these two investments is expected to be €90,000/yr [$101,000/yr],” notes Nieuwenhuizen.

AkzoNobel also heavily focuses on the use of renewable energy. According to Nieuwenhuizen, about 60% of the company’s worldwide pulp and performance chemicals operations currently run on renewable power — a level that might rise to 80% by 2020.

In an effort to boost renewable energy use, the company has established three wind parks in Europe’s Nordic region as part of its Vindin wind energy project (Figure 3). This aims to deliver clean energy to the pulp and performance chemicals business in the region.

In the Netherlands, AkzoNobel has custom-built a 2-km pipeline to provide steam from a waste-to-energy plant to its salt packing facility in Hengelo. In the Benelux region, it has signed a long-term power purchase agreement with the biggest and most-efficient biomass plant there.

“In Brazil, we’re excited about our ‘chemical island’ concept, which enables us to run our Imperatriz plant on 100% renewable energy. By harvesting the local eucalyptus trees every seven years, the pulp producer uses waste material to generate electricity via biomass. It’s a beautiful, cost-effective business concept, with no or limited transportation of chemicals required. But taking what works in Brazil and replicating it in Europe or the U.S. is not always feasible. Our goal is that by 2020, 45% of our total energy needs will be met by renewable energy, up from 34% currently. So, despite these successes, there’s more to be done,” Nieuwenhuizen concludes.

Ambitious Program

At Eastman Chemical, Kingsport, Tenn., the goal to reduce energy intensity by 20% by 2020 from a 2008 baseline involves staff at all levels within the company. “Through the Worldwide Energy Management program, we engage employees on a variety of levels, from major manufacturing and engineering projects to awareness campaigns,” explains Sharon Nolen, program manager.

As part of the program, a dedicated worldwide energy-management team continually analyzes energy use at Eastman sites looking for new opportunities. “We have commitment and support from our executive team to drive continuous change and improvement to ensure focus on sustainable operations,” she adds.

One of the most dramatic savings was a 4% improvement achieved between 2013 and 2014 in the two most-energy-intensive processes at Kingsport; the company will not reveal details. This is only one of many recent projects that together since 2008 have helped save over $30 million in energy costs at the site (Figure 4).

Another involves the installation of a flash system that uses 600-psig condensate from columns — eliminating the need to drop steam pressure to 300 psig steam as originally required. Then there’s the azeo energy optimization project, which involves developing a process control strategy for low- and medium-pressure steam use on distillation columns to reduce energy consumption. Another initiative is the replacement of steam jets with more-efficient liquid ring vacuum pumps to eliminate the loss of steam condensate and decrease energy use.

The company’s Indian Orchard operation in Springfield, Mass., has implemented two successful projects. The first focuses on hot water recycle —cooling water previously sent to a sewer now serves as feed in a washing process. In addition, the plant has reduced dryer steam consumption by installing a new heat recovery system designed to re-use waste condensate also previously sent to the sewer.
At its Chestertown, Md., site, Eastman has replaced burners and installed a new burner management system on the primary steam boiler, improving its efficiency. This enabled the plant to retire two of its older, less-efficient thermal oil furnaces and replace them with a more-efficient unit.

In addition, Eastman has upgraded to more-efficient lighting at a Kingsport warehouse. LED lights and occupancy sensors have replaced fluorescent lamps, resulting in not only lower energy use but also improved visibility for warehouse staff. Together with a similar project in office buildings at the same site, the company has reduced this sort of energy use by 26% in the last year.

Ottewell2 Seán Ottewell is Chemical Processing's Editor at Large. You can email him at sottewell@putman.net.