"There is nothing more powerful than an idea whose time has come," says Victor Hugo, the 19th-century French writer and author of Les Miserables. Fine, but it's also important not to get run over by the bandwagon you're trying to jump onto.
So while sustainability and green manufacturing are wonderfully positive forces, the question for many process engineers is how to do it in their own applications and facilities? Sure, users can make gains by finally installing more efficient motors and drives. But then what? How much of your application will have to be redesigned to use more sustainable raw materials and produce products that are greener to use?
Well, so many thousands of different users, process engineers, system integrators and suppliers are getting into the green manufacturing and sustainability act that there are bound to be many useful ideas that you can use to do it too.
For instance, Sinopec Shanghai Petrochemical Co. recently implemented Honeywell Process Solutions' Advanced Energy Solutions software to improve controls and electricity generation, while reducing coal consumption, greenhouse gas emissions and costs at its Shanghai power plant. The plant improved the efficiency of its circulating fluidized bed (CFB) combustion process, which uses crushed coal mixed with limestone that's heated up to 900 °C, to generate low-cost electricity with low emissions. Honeywell's tools helped increase process efficiency by developing a closed-loop, advanced control strategy to optimize combustion performance for the CFB boilers while following environmental regulations.
"Our control issues at the Sinopec power plant couldn't be solved by traditional PID control loops, so we looked for a new way to improve boiler efficiency and cut emissions at the same time," says Zhao Weijie, Sinopec's chief engineer. "As the first company in the world to apply advanced control application technology to CFB units, Sinopec enhanced the effectiveness and control performance of the DCS at the CFB boiler level and for the entire plant. Even more impressive, all improvements were achieved by implementing software rather than executing a major hardware refurbishment. We also saved an estimated $1 million on the supply of energy to our refinery."
Sinopec also reports that using Honeywell's software enabled its Shanghai power plant to increase boiler efficiency by 0.48% and operating steam temperature by 2.8 °C; improve stability of combustion process variables; reduce air pollutant emissions from fuel and limestone consumption to comply with environmental standards; optimize production capacity use and transient states control; extend production asset life; reduce maintenance; and reduce expected consumption of coal by more than 500 tons and coke by 1700 tons annually.
Steering to Sustainability
Not surprisingly, upgrading core process controls can improve meat-and-potatoes efficiency. However, they can also help redirect procurement, resource use, operations, products and maintenance to further reduce carbon emissions, shrink environmental footprints and provide a good example for suppliers, staff, customers and the overall community.
For example, Tata Steel's plant in Port Talbot, Wales, U.K., recently upgraded the controls on its largest steam boiler with energy-management technologies and services from Emerson Process Management. However, unlike most boiler upgrades, these new controls are enabling Tata to increase its energy efficiency, maximize use of waste fuels, cut emissions and reduce its former reliance on purchased fuels.
The Port Talbot facility is Britain's largest integrated steel mill. It produces more than 4.5 million tons per year of high-quality sheet steel for the automotive, construction and household appliance markets. It includes two blast furnaces and a basic oxygen furnace, as well as continuous casters and a strip rolling mill. So far, Emerson has upgraded controls on three of the site's seven steam boilers (Figure 1).
"The boiler upgrades are helping us make better use of ‘indigenous' waste fuels, such as blast furnace gas, BOS gas and coke-oven gas, which are byproducts of our manufacturing process," says Andrew Rees, manager of Tata Steel's upgrade project. "The improved controls are part of a comprehensive energy management project that's expected to reduce powerhouse energy consumption by 3% to 5% and help us achieve our vision of becoming energy self-sufficient."
To begin the Port Talbot upgrade, Emerson conducted a study to identify opportunities for improving powerhouse operations, and then designed and delivered the most appropriate integrated combustion-control, burner-management and energy-management solution. It included Emerson's SmartProcess Energy and SmartProcess Boiler optimization technologies, DeltaV digital automation system with model-predictive control, DeltaV SIS process safety system, Rosemount and Micro Motion measurement instruments, Fisher control valves, and Bettis and Hytork valve actuators.
In the past, the plant's boilers needed frequent attention, and had to use supplemental natural gas to compensate for varying energy content of waste fuels. Following the upgrade, operational stability was increased, and energy costs declined because more efficient use of waste fuels reduced the need for natural gas. Using more waste fuel to power the boilers instead of burning it in flares also helps reduce emissions.
Green Needs Control, Too
Naturally, after considering a few of the latest sustainability projects, it becomes clear they share a common thread with traditional process control—all are based on sensing physical properties, analyzing complex data and acting on the resulting decisions. For example, Center Ethanol Co. and its four-year-old plant in Sauget, Ill., near St. Louis, turns 19.2 million bushels of corn into 54 million gallons of ethanol, 172,000 tons of dry distiller grain and 1.5 million gallons of corn oil per year. To optimize and gain production efficiencies in its applications, Center's staff and the former Delta-T Corp. in Williamsburg, Va., installed Siemens Industry's Simatic PCS 7 process control system. The staff also built screens on PCS 7 outlining standard operating procedures for starting, stopping and shutting down equipment, and also introduced programming that instructs operators how to fix out-of-range process parameters. Faceplate and interlock screens enable operators to click on a symbol, such as a pump, drive, valve or PID loop, and quickly determine the status of the device and process interlocks. Operators also have a view of the entire plant from the control room and can drill down into process areas or devices.
"If a process goes out of parameter, an alarm alerts technicians in a central control room with four operator stations," explains Tim Kostecki, Center's operations manager. "The operators can check the equipment, or cross-check what it's saying against what the lab is telling us. This has improved temperature, pressure and many other control variables."
Center also has added programming to better control its enzyme and chemical additions, as well as front-end corn grinding and fermentation processes. "We're saving more money because we can optimize chemical additions to the process," explains Kostecki. "The new programming ensures that we start off with the right recipe for fermentation. When you control your front end and get your fermentation in a steady state, the whole plant runs more efficiently. If you're going up and down all the time—such as one fermentor is at 14% and another is at 13%—then it will swing around the distillation at the back end, so you can't get your fermentation to be the same ethanol concentration every time."
Kostecki also reports the trending capability of the plant's control system gives operators at least three months of historical data that can be loaded into an Excel spreadsheet, eliminating the need for time-consuming manual data entries.
"We use trending every day," says Kostecki. "We know if our system is running out of tank room. But rather than slowing down the plant, the guys in the control room can graphically track and manipulate tiny changes in tank levels. It also uses the trending capability to make sure dryer temperatures, pressures, flow rates and amps are at the right levels.
"When you're monitoring and logging data as part of an energy efficiency strategy, it's important to analyze power consumption data that you collect in context with other data related to that application," adds Ben Orchard, application engineer at Opto 22. "For example, if you're trying to reduce facility power consumption, you need to gather data on suspected large loads such as chillers. You then need to gather data that put that chiller load in context, such as the room temperature for rooms serviced by that chiller."
Of course, if operations can be optimized for greater sustainability in one application, then the next job is to do it at multiple sites. To monitor and alarm stack emissions, comply with legislated limits and avoid the possibility of required shutdowns, South Africa-based Eskom partnered with Bytes Systems Integration and Invensys Operations Management to optimize operations at Eskom's 13 coal-fired plants.
"Without treatment, we'd spew concentrations of 30,000 to 60,000 mg of ash per normal cubic meter (mg/Nm3) into the atmosphere," says Dr. Kristy Ross, senior consultant at Eskom. "However, by using abatement technology, such as electrostatic precipitators or fabric filter plants, more than 99% of ash is removed from the flue gas streams, providing a particulate emission concentration of usually less than 200 mg/Nm3."
In general, the plants must run below 75 mg/Nm3 about 96% of the time, and never exceed 300 mg/Nm3. However, generating capacity shortages, maintenance shutdowns, varying coal qualities and high load factors make this a difficult job, even though emissions are centrally monitored at Eskom's Integrated Generation Control Centre at Megawatt Park.
As a result, Bytes recently reorganized Eskom's existing process control infrastructure, which included Invensys' ArchestrA system platform, data historian, Active Factory historian clients and Wonderware's InTouch SCADA/HMI, Information Server and Alarm Provider software. Also, the integrator developed one KPI dashboard for each thermal power station, showing hourly emission values, their limits and length of time normal limits were exceeded. Any exemptions to the limits are also shown, so the system can adapt.
"During start-up after shutdown, a unit's emissions will be higher than during normal operation, so it's important to know when a unit is about to come on line, how long it was off and how long the higher emission level lasts," says Machiel Engelbrecht, Bytes' system engineer. "This helps us apply for the necessary exemptions. Also, the supplied information puts Megawatt Park in a good position to initiate preventive measures, and ensure optimal load distribution in the event of a shutdown due to excessive emissions."
Consequently, early warnings are raised when emission values get within 20% of acceptable limits, which helps prevent penalties and unit shutdowns. "Because of the scalability and versatility of our new software, it was possible to deliver a control system for a process that previously had to be done manually due to its complexity," adds Engelbrecht.
Sun to Steam for Oil
While parallels between sustainability and process control are growing clearer, green manufacturing's diversity is already creating some strange bedfellows, For instance, in what has to be one of the most ironic sustainability efforts, Berry Petroleum in Denver, Colo., cooperated with system integrator T.J. Cross Engineers Inc. in Bakersfield, Calif., and Glass Point Solar to use the sun's power to help produce steam for injection into oil field reservoirs, where it heats heavy crude to reduce viscosity and aid extraction. This enhanced oil recovery (EOR) process is automated by AutomationDirect's controls, which work with GlassPoint's solar steam generators to preheat water and then introduce it into Berry's natural gas-fired steam generator, which greatly reduces fuel consumption and operating costs.
"GlassPoint's solar water heating design uses greenhouses to house its entire solar concentrator mirror and water heating system," says David Llewellyn, senior engineer in T.J. Cross's process controls group. "For this project, the single 7000-sq ft greenhouse is made of galvanized steel and aluminum with a tempered 4-mm glass roof and walls. The mirrors inside are made of a reflective, anodized-aluminum material that's widely used in commercial lighting and is durable indoors, but isn't usable outdoors. These mirrors are light enough to be easily supported by the greenhouse and can be positioned using only the torque generated by eight 40-watt stepper motors and drives. The mirrors focus on GlassPoint's thermal-conversion device, which is a just a carbon steel pipe, and illuminate it with 85 times more intensity than direct sunlight."
AutomationDirect's Model Productivity3000 programmable automation controller (PAC) works with GlassPoint's proprietary controls to track the sun, secure the most power, maintain heated water temperature at about 190 °F and regulate flow. Data logging is performed by AutomationDirect's DataWorx software, which translates about 10 parameters from the PAC to a Microsoft Access database every 30 seconds. Operator interface to the PAC is provided by AutomationDirect's 12-in. C-more touchscreen (Figure 2).
"The system maintains desired flow rate and corresponding 190 °F output via a flow control loop," adds Llewellyn. "In the loop, a control valve is installed downstream of a constant speed pump. The PAC receives a 4-20-mA signal proportional to temperature from a transmitter installed at the receiver tube discharge from the greenhouse. This measured process variable is compared to the 190 °F setpoint in a PID loop control executed within the PAC. The PID loop output is a 4-20-mA signal that modulates the control valve to regulate water flow to the receiver pipes."
Deepening Green Process
So where else can sustainability spread? Well, one idea is to turn around and make green its own product and industry. In this case, Polyflow in Akron, Ohio, reports it's developed a practical, cost-effective pyrolysis process, which basically heats dirty waste plastic in a reaction vessel until it breaks down into a fluid similar to crude oil that can be refined into fuels. While pyrolysis has been possible for decades, Polyflow reports it's only been possible to tweak it well enough to handle multi-stream plastic sources for the past few years. As a result, Polyflow recently built and tested 400-pound batches in a semi-trailer-mounted prototype, and is now working with integrator South Shore Controls in Perry, Ohio, to scale it up to an 8.5-foot x 60-foot reactor cylinder that will continuously process 2.5 tons per hour (Figure 3). The plastic waste input will result in 70% liquid product, 13% char and 17% non-condensable gas, which can help run the cylinder. Also, Polyflow's process will need 1.7 million BTUs to operate, but the liquid produced reportedly will be able to produce 27 million BTUs.
Polyflow also uses a three-stage process to sort and extrude its plastic raw material, heat treat it, and then distill and refine its end products. Likewise, Polyflow is using Rockwell Automation's PowerFlex variable-frequency drives and starters, as well as ControlLogix PLCs to control I/O devices monitoring the temperature, pressure and flow of the separation equipment, reactor, distiller and refining processes. This pyrolysis process is networked via EtherNet/IP and managed by Rockwell's FactoryTalk View software platform. "The cylinder has to be made of stainless steel to withstand the mechanical and thermal stresses of this process, as well as the corrosive chemicals it produces," says Rick Stark, South Shore's president. "However, though the reactor uses natural gas to get up and running, it can use its distiller to generate its own fuel, and operate as a self-sustaining system."
Jay Shabel, Polyflow's CEO, adds that his firm's pyrolysis process can potentially divert 30% of the waste that usually goes into landfills and replace 13% of foreign oil sources. "There are seven different process parameters that are unique to this pyrolysis process, which allow it to take multiple sources of polymer waste and turn it into an aromatic-rich liquid," explains Schabel. "However, while our controls and automation already helps manage our pilot process, they'll be even more necessary when this becomes a continuous process, and we have to constantly respond to changes in feedstocks and conditions, or when market data indicates we should switch to making a different product."