ALTERNATIVE FUEL AND ENERGY
Case study: Memphis Biofuels goes online
- Distributed control system at home in alternative, groundbreaking application.
- Alternative energy technology will require a trillion dollars a year in capital investment by 2040.
- The key to high quality product is running in steady state without fluctuations or variability.
By John Arnold and Don Mack
When entrepreneur Ken Arnold entered the biodiesel market in mid-2006, the prices of raw feedstocks, including soybean and vegetable oils and animal fats, were low.
Investors in his startup company, Memphis Biofuels, agreed projections for biodiesel profits were solid. All signs pointed to a great future for the company as the green field project in Memphis, Tenn., got off the ground.
But in early 2007, the prices for soybean, vegetable, and animal fat feed stocks increased to a point where it was, and remains, difficult for biodiesel producers to make a profit.
"The biodiesel market is going through a challenging time right now," said President and Chief Executive Arnold, who has more than 30 years of chemical industry experience. "While I am confident the biodiesel business will move forward, many small producers relying on niche or local markets will not survive."
In addition to being one of the nation's largest capacity producers of biodiesel-50-milliongallons annually-Arnold has reason to be optimistic about the future of Memphis Biofuels. "We have a full service laboratory, direct access to the Mississippi River, and five Class-1 railroads in the United States, and a state-of-the art process control system."
Key to fast startup
In June 2006, after Memphis Biofuels found its investors, it converted a former chemical processing plant into one of the nation's largest capacity production facilities of biodiesel within 90 days.
The distributed control system (DCS) was a vital component in meeting the startup goal. Johnson City-based CCA-WESCO specified and integrated the system. The tightly integrated DCS with human machine interface (HMI) environments allow Memphis Biofuels to make configuration changes on the fly.
It would have been very hard to meet investors' expectations without the DCS. The plant would not have had enough trained people to get the plant up and running on conventional control systems.
The decision to go with the control system was also for long-range financial considerations. The features of the system will lower the total cost of ownership through all phases of the production lifecycle-including minimizing design, engineering, and installation costs, as well as lowering operational and maintenance expenses.
During the pre-commissioning phase at the plant, CCA-WESCO customized and used an advanced simulation program to train plant employees. The simulation program is indistinguishable from the plant's actual operations.
The software tool helped lower the system's total cost of ownership by providing the team with immediate feedback and helping them understand how the system would operate.
Now that the plant is operational, the simulation program works as an educational tool for new operators, as well as helping to correct operational problems at an engineering station in the plant's control room.
The flexibility of the DCS helps the plant instantaneously change the processes for maximum production, further lowering the total cost of ownership.
"When we started the design and implementation of the control system, there was a set of diagrams that implied a certain operational framework," Arnold said. "Because the control system is extremely adaptable, we could add buttons as needed to help the operators determine the flow, automatically fill the tanks, and switch the modes of the loops."
Control room in charge
During the startup, CCA-WESCO created programmed interlocks and safety functions within the DCS hardware. Operators in the control room can quickly get to the cause of an alarm or problem because faceplate and interlock information is readily available on the HMI.
"We handle highly flammable methanol and sodium methylate," Arnold said. "The DCS ensures that we can properly unload trucks without a spill. The control room is in charge. Our operators have complete visibility over the entire process- including the critical variables, levels, pumps, and motors."
From the control room, technicians oversee the entire automated biodiesel production process. The process begins when the oils feed in from rail and truck tankers to the storage tanks. The DCS monitors and controls pump and level functions, and methanol and catalyst tanks are equipped with automatic cut-off valves to enhance safety and reduce the risk of fire.
The system connects directly to level indicators with high alarm and high/high alarm functions that immediately shut off the valves during an event.
It is important the oils always be at the proper temperature in the continuous circulation loop. Operators constantly monitor temperature readings provided by temperature transmitters. The temperature transmitters also monitor steam flow through the heat exchanger.
After flash drying the oil, it feeds through flow meters into the system. The DCS controls the flow rates of the methanol and catalyst through its Profibus connection to variable frequency drive operated pumps. The oil then goes through a reactor, reaches a certain temperature, and feeds into a settling area. The biodiesel separates from the glycerin and then flows into a second stage reactor where the flow rate of the methanol and catalyst add in proportion to the flow rate of biodiesel.
After the biodiesel comes out of a second settling system, flashing the methanol again, the biodiesel goes again to washing and settling. Then it feeds into a drier. The finished product ships via truck and rail tankers to distributors throughout the U.S. as well as to international markets.
Consistency key to quality
Consistency and quality are essential in every drop of the commodity product. Every shipment of biodiesel produced at the plant sees testing in the facility's lab. Each shipment must meet ASTM 6751 standard criteria for quality, including clarity, sulfur content, particulate matter, and methylester levels.
"The key to ensuring a high quality product is running in steady state, even at 100 gallons a minute," Arnold said. "We don't have a lot of fluctuations and variability. The system is very stable and very good at maintaining set points and parameters throughout the process."
Additionally, Arnold noted the DCSs ability to monitor operational trends on the plant-operators' console screens makes maintaining fuel quality at high level possible.
"Our trend screens include all PIDs, valves, motors, tanks, and pumps," Arnold said. "The standard trending capability allows the operator to bring up a faceplate for historical data in real time. Being able to go back and see what was happening at any part of the process, and then to make adjustments, has been invaluable."
Faceplate and interlock screens allow operators to click on a symbol, including a pump, drive, valve, or PID loop, to determine quickly the status of the device and process interlocks. This helps operators anticipate problems and keep the process moving.
The system gives operators a comprehensive view of the entire plant from the control room. They can then drill down into a specific process area or to a specific device to get more information. "This holistic look at the system is a valuable troubleshooting tool," Arnold said.
"A control system consisting of a typical process control system and flow controllers would not ensure the product quality we have today," he continues. "The DCS allows us to go back to any point in time and view what was going on in the process. That is a big factor in consistently maintaining good fuel quality."
The system's engineering software allowed CCA-WESCO to create and integrate custom function blocks and corresponding faceplates. Arnold said other systems require an additional visual basic software package to customize the application.
By being able to create its own function blocks, CCA was able to optimize the system to meet the requirements of this application. "The user-created blocks are easy to build, manage, and support," Arnold said.
Additionally, the plant view function of the DCS available in the engineering toolbox facilitates remote support.
As long as a CCA engineer is at a computer, he or she can walk the operators through maintenance issues. They can quickly look at the same information on the screen. Having the configuration organized and structured in a way that reflects the process allows them to support the plant from remote locations.
While it remains unclear what direction the biodiesel industry will take, Memphis Biofuels has the flexibility, capacity, location, and control technology to head in any market direction.
Arnold has plans to eventually expand the plant to produce 100 million gallons of biodiesel annually.
"Right now we are using animal fat feed stock in the process; next month it could be soybean oil," Arnold said. "That is the beauty of this DCS. We instantaneously make changes to adjust to a changing market. That is the edge we need to lead the industry."
ABOUT THE AUTHOR
John Arnold (firstname.lastname@example.org) is an automation specialist at CCA. He has two degrees in chemical engineering (ChE) and is an adjunct professor of ChE at the University of Tennessee. Donald Mack (email@example.com) is an ISA senior member. He has an electrical engineering degree and works as the Biofuels Initiative Lead, Process Automation Systems at Siemens in Spring House, Penn.
Computers made it possible
Distributed control systems (DCSs) are control manufacturing processes that are continuous or batch-oriented, such as oil refining, petrochemicals, central station power generation, pharmaceuticals, food & beverage manufacturing, cement production, steelmaking, and papermaking.
They connect to sensors and actuators and use set point control to control the flow of material through the plant. A typical example is a control loop consisting of a pressure sensor, controller, and control valve.
Pressure or flow measurements transmit to the controller, usually through a wire. When the measured variable reaches a certain point, the controller instructs a valve or actuation device to open or close until the fluidic flow process reaches the desired set point.
Large oil refineries have many thousands of I/O points and employ very large DCSs. Processes are not limited to fluidic flow through pipes however, and can also include things like paper machines and their associated variable speed drives and motor control centers, cement kilns, mining operations, ore processing facilities, and others.
Early minicomputers were controlling industrial processes in the 1960s. The IBM 1800, for example, was an early computer that had input/output hardware to gather process signals in a plant for conversion from field contact levels (for digital points) and analog signals to the digital domain.
The DCS largely came about due to the increased availability of microcomputers and the proliferation of microprocessors in the world of process control.
IEA Chief calls for $45 trillion investment
The head of the International Energy Agency (IEA) said in June that high crude prices could see its global oil demand forecasts cut further and that billions of dollars of investments are required to boost energy efficiency and cut emissions.
The IEA's investment estimates include the cost of building 32 nuclear power plants a year globally between now and 2050, as part of the battle to cut carbon emissions.
Nuclear plants emit virtually no emissions.
The Wall Street Journal reported IEA Executive Director Nobuo Tanaka said total investments of $45 trillion, or 1.1%, of average annual global economic activity are necessary in carbon-cutting measures over the period to achieve a 50% cut in emissions by the middle of the century.
Tanaka said on an optimistic assumption of technology development, all options up to a cost of $200 a ton of CO2 would need to consideration or up to $500 a ton under less optimistic assumptions.
"I'm not surprised at the CO2 price range the IEA's shown given the kind of reductions we have to achieve," said Emmanuel Fages, carbon analyst and strategist at investment bank Societe Generale's Orbeo joint venture with Rhodia.
"This will be a revolution in the way we manufacture and generate power. The biggest challenge will be for utilities, as the power sector will have to be CO2 free by 2050 for emissions to halve."
The IEA chief said investments of $100 billion to $200 billion a year in the coming decade, and $1 trillion to $2 trillion a year in later decades, will be necessary for measures like energy efficiency and carbon capture programs and new nuclear plants to cut carbon emissions in half by 2050.
Richard Warner, head of climate change and sustainability at international consultancy Accenture, said companies would need a consistent and solid regulatory and legislative framework if they were to have the confidence to invest in the technology needed for the future.
Biofuel is a solid, liquid, or gas fuel consisting of recently dead biological material, most commonly plants. This distinguishes it from fossil fuel, which is from long-dead biological material. Biofuel can be from any (biological) carbon source. The most common by far is photosynthetic plants that capture solar energy. Many different plants and plant-derived materials go into biofuel manufacture.
Flash dry in chemical engineering-this is the rapid evaporation of moisture from a porous or granular solid by a sudden reduction in pressure or by placing the material in an updraft of warm air.
Profibus (Process Field Bus) is a type of fieldbus with more than 20 million nodes in use worldwide.
Fieldbus is an industrial network common communications protocol for controlling systems, field instruments, and for real-time distributed control.
ASTM 6751 is a specification for biodiesel as a mono alkyl esters of long chain fattyacids derived from vegetable oils or animal fats, for use in compression-ignition (diesel) engines.