Marnie Surfaceblow: Maya Bucks the Trends

Long-time POWER readers may remember Marmaduke Surfaceblow, a fictional character whose engineering escapades were brilliantly portrayed in hundreds of stories published within POWER magazine’s pages over more than 30 years beginning in 1948. Today, the fictional series continues through Marmy’s granddaughter, Marnie, who is an engineering wiz in her own right.

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Big data holds many secrets to help operate your power plant safer and more efficiently. But are you really seeing the entire landscape of your problem? Don’t miss the forest while focusing on the trees. “Daughter, after your experience with your first job, I thought you hated ammonia, but you are working with it here? Why again is this?” asked Ashok Sharma, patriarch of Maya’s family, as he grabbed an orange newly picked from his hectares of groves and began to peel it. Maya sighed as she sat by her father on their front porch and brushed her hair in the Nagpur breeze. It was going to be another scorching hot day, and already the dust from the orange groves and roadways was starting to rise. It was Sunday, but for those with the responsibility of keeping power flowing, just another workday, including for Maya. “Even a skunk may have a useful purpose,” she replied. Then, noticing the quizzical look from her father, Maya quickly added, “Sorry father, it is a saying from my boss, meaning, that which is bad may yet have a good purpose. I am working hard to keep the ash from the new biomass power station from contaminating the land around it—including your orange groves.” The elder Sharma shook his head while passing Maya an orange slice. “It is amazing to see you, now a grown woman and traveling the world to solve so many problems with that very strange … person.” “Father!” Maya interjected with unusual passion. “Please do not speak ill of Ms. Surfaceblow! She is not merely my employer, she is my mentor and friend as well. And it was her connections that gave me this work in Nagpur, also giving me this paid vacation.” Waving his hand, her father demurred. “I mean no harm, but I worry. I also worry that you are here alone to solve this problem at the power station. Do you not have any assistance?” “She does not need any,” Maya’s auntie Komal pronounced with authority, grabbing an orange as she joined the pair. “Our Maya has made the entire family proud, and we wait each week for your letters describing the work you do. Still, I wished to meet this Ms. Surfaceblow in person, as your letters describe her so vividly.” Seeing her taxi approaching, Maya shouldered her plant gear bags, stood, and waved to the driver, then smiled at her father and auntie. “Marnie is working at a nuclear power station, and since I am not a United States citizen I could not work on the project. We discuss our projects each day by video to share ideas, and all is well.” As she turned to walk to the taxi, in the distance she saw a dark cloud from a new power station stack. “At least I hope all will be well,” she added.

The New Norm: Zoom Meetings

Late Sunday evening, Marnie surprised Maya with a video call. “OK, little miss ‘I’m-in-a-warm-paradise-without-mutated-giant-fiddler-crabs,’ what is the situation with this biomass boiler?” Marnie’s voice from another continent was clear, although the video was choppy (Figure 1).

1. Marnie and Maya meet regularly when working apart using a video conferencing service to discuss projects and collaborate on solutions. Source: POWER

“Mutated crabs … ma’am?” asked Maya in disbelief. “Just a joke. You know, nuclear plants? We do have some serious biofouling in a condenser, but it hasn’t reached the ‘mutant’ stage yet,” Marnie quipped. Maya laughed lightly. “I’ve missed your sense of humor, ma’am. So, this power station was built to serve this agriculture district. It is powered from mixed plant and animal waste from local farms, and to combust this highly variable fuel, the owners chose a bubbling fluidized bed furnace co-generating electric power and steam heat. Its specification is for 230,000 kg/hr [506,000 lbm/hr] of steam at maximum capacity. The furnace is highly flexible in practice, generating power and steam with few problems. However, the power station is limited to 75% capacity on average due to continually exceeding their ash and SO₂ emissions limits. They use local limestone in the bubbling bed to remove much of the SO₂ generated, and an electrostatic precipitator [ESP] to remove ash,” Maya explained. “I knew they would regret choosing an ESP,” replied Marnie, shaking her head. “Given they’re burning a fuel with a fly ash resistivity that could span six orders of magnitude, I recommended a fabric filter baghouse. But what do I know, I’m just the smartest and most experienced power engineer in the universe,” Marnie noted, only half joking. “Do not forget being the humblest, ma’am,” Maya interjected with a smirk. Her rant derailed, Marnie glared at Maya, and growled, “Please proceed.” Maya did so. “Ma’am, I am certain you know the owners were concerned regarding unburned combustible fires in the fabric filter, and in India we have much greater experience with ESPs. They were also convinced by the OEM [original equipment manufacturer] to inject ammonia to reduce NO_x, and given that could enhance ESP ash removal, they thought it would provide a benefit. However, their ammonia injection provides exceedingly variable results, and the ESP performance is seemingly unpredictable.” The video began to fail, but Maya clearly saw surprise on Marnie’s face. “Oooooh, so it’s that old chestnut again, huh? Well, my friend, good luck, I have a date to make sense of chaotic condenser cleanliness here. Expect the unexpected!” Marnie reminded Maya exuberantly. As the video chat ended, Maya sat back in her chair and looked to the ceiling. “That saying could apply to anything!” she thought.

Burning Technology

Monday morning promised a fierce day, with the temperature accelerating towards 40C (104F). Maya was inspecting the station fuel handling system, accompanied by Station Manager Suresh Mankar, and a shockingly young lead engineer, Darsh Rao. Leaning in to comment over the din of a front-end loader, Maya asked, “You have been to university, yes, Mr. Rao?” Mr. Mankar laughed and answered for his employee, “Mr. Rao was top of his class at the Indian Institute of Technology, and while he is young, he has brought many new and good ideas to our project.” “But I can always learn from my elders, such as you ma’am,” Mr. Rao added with a smile. “Ouch, but I did deserve that,” Maya thought, then carried on the conversation. “You developed an impressive fuel tracking and analysis system, and your use of RFID [radio-frequency identification] tags mixed with each fuel delivery to track when they are burned is unique.” Mr. Rao blushed slightly, “I have always loved big data and kept faith that anything may be predicted with enough data and proper trends. Then, I read a POWER magazine article your boss, Ms. Surfaceblow, wrote on waste to energy. She pondered that technology once thought of as magic was now just trash and burned for heat. I saw RFID tags being thrown out in the trash, and thought perhaps this could help us.” “Mr. Rao’s system has done more than just help; we estimate it saves 90 lakh Rupee annually,” added Mr. Mankar, “but it has not solved this problem with the ash emissions derates.” “Indeed,” agreed Maya. “What do you and your engineers believe are the responsible factors?” “Fuel quality variability is the factor,” pronounced Mr. Rao, “although, for some reason, it resists the trends!” “To assist the government mandate to lessen the terrible smoke from burning field stubble, we receive more than 30 different types of agricultural waste from the region—including from your family’s orange groves,” added Mr. Mankar. Mr. Rao eagerly cut in, “Ma’am, each fuel has ash chemistry and properties impacting ESPs. I wish we had a fabric filter instead, but that we cannot change. Our ammonia injection system was promised to help reduce NO _x and improve ash collection, but I cannot find the trends. Sometimes, more ammonia helps the ESP collect ash, then suddenly, it worsens and almost no ammonia is best. We can increase ESP power, change rapping schedules, flush the ash hoppers more frequently, and in many cases, nothing seems to help.” Soberly, Mr. Mankar placed a hand on young Mr. Rao’s shoulder. “I know you will find it, with the help of Maharashtra’s most famous engineer ever!” he declared, nodding at Maya, while raising a questioning eyebrow. Hesitantly smiling, Maya replied, “Do not fear, we will help you find your trends.”

Fueling Speculation

“I believe this is a fuel quality problem,” Maya said in her nightly video chat with Marnie, “but equipment performance may be contributing to it.” Marnie shrugged, “Well, their ESP was designed originally for coal ash, not biomass ash.” “But ma’am, their fuels fall within the design ranges for ash, sulfur, sodium, and other ash mineral specifications,” Maya noted. “They ceased receiving proven problem fuels, like rice straw, and appear to have a good fuel tracking system.” “Courtesy of our trendy Mr. Rao fellow, and his RFID-ea,” Marnie replied. “I’m getting a better picture now, so before I go, I’ll give you this bit of wisdom. A DCS [distributed control system] with 50,000 data points still won’t tell you what the plant operators ate for breakfast.”

A Difficult Night of Operations

Tuesday morning found Maya, Mr. Mankar, Mr. Rao, and other engineers debating the cause of an overnight ash emissions derate. Mr. Rao tried creating new trends to train his neural network model, while the lead night shift engineer, Mr. Kavidass, expressed the frustration of his crew. “We increased ammonia injection to the normal level, and the ash emissions decreased,” Mr. Kavidass explained. “Ash emissions increased, so we increased ammonia to the maximum and nothing changed! Then, our ammonia alarms warned we had too much slip, so we reduced ammonia to the minimum setting. This stopped the ammonia slip alarm, but I noted ash emissions didn’t change. We increased ESP power, flushed the ash hoppers, and then I turned the ammonia system off and ash emissions increased!” Maya asked, “What changed just before the ash emissions increased? Your data shows flue gas moisture and sulfur content decreased suddenly. Then, less than 30 minutes afterward, the ESP problems began. Was there any trouble emptying ash hoppers? Was the ash sampled during the night?” “NO_x emissions were near our permitted limits,” replied Mr. Kavidass, “so we switched from the animal manure bin to the bagasse feed and turned off the ammonia. Barely five minutes later the ash emissions began rising.” Maya nodded, taking notes. “Then, you resumed injecting ammonia, but despite your attempts, the ash removal did not return to normal. Has anyone tested the ash resistivity during these events?” asked Maya. “We do not need to. I have correlations to predict ash resistivity developed from our last year of operation,” Mr. Rao said proudly. “Really?” asked Maya with disbelief. Mr. Rao crossed his arms and shook his head. “Coal relationships should apply—see? Here are the technical papers by Bickelhaupt and colleagues.” Pointing at his laptop screen, Mr. Rao showed Maya a paper she was well familiar with. “Our fuel ranges fall well within acceptable bounds for their equations, and our predictions follow established procedures.” Mr. Mankar shrugged. “Miss Sharma, ash resistivity testing is expensive, and few labs nearby offer it. Mr. Rao has saved us significant cost by his calculations, and they are backed in science,” he said. Maya sat back and crossed her arms, frowning to herself as the debating continued its cacophony around her. One nagging thing stuck in her head, something Marnie had said in one of their check-in video chats. Suddenly, it came to her, “She said, ‘It’s that old chestnut again.’ She has seen this before!”

A Path Previously Traveled

“Maya, I’ve seen it all, been everywhere, and done everything,” Marnie touted. “Done everything, ma’am?” Maya asked with a smile and raised eyebrow. “Yes,” Marnie replied curtly, “and don’t ask me questions where you may not like the answer. But back to reality, yes, I’ve seen this several times before. Life can be very surprisingly complicated—just try writing the equation for a blade of grass. Some plant problems are intuitive, some have clear trends. Well, this isn’t one of them. This is a multivariate problem requiring a combined first principles and empirical approach. I spent an entire Christmas vacation in front of my computer to find the answer.” “I have been reading a copy of your findings in our Surfaceblow intranet archives. I was amused seeing you wrote equations on Christmas cards and scanned those in,” said Maya as she smiled. “It seems a festive way to calculate, yes?” Marnie shrugged, “I was hit by inspiration, grabbed a pen, and wrote on whatever was nearby. Have you reached the conclusions yet?” Maya shook her head. “It is nearly 600 pages of technical references, equations, sketches of dragons, and goth song lyrics. I will require the night to finish,” she surmised. Marnie nodded. “It’s worth the read. I could drop hints and tease you until you worked the problem out yourself, but you have nothing to prove to me, my friend. Today’s lesson is: ‘If someone’s already blazed an academic trail through the jungle surrounding you, try that path first before making a new one.’ Read, learn, and tell me if you think that one song on page 252 is any good? The one about the vampire cat café.” The video ended. Maya pinched the bridge of her nose and shook her head. “I fear someday I must describe these things to a therapist,” she muttered to herself.

Highly Variable Conditions

It took Maya two days digesting Marnie’s ammonia magnum opus, but it paid off. She called a meeting for the following day to report her conclusions. Facing the assembled plant staff in the canteen (the coolest spot in the morning), Maya began, “I have no concise solution, for I do not believe such exists. Instead, I can tell you how to find potentially several parallel solutions, praise be to Ms. Surfaceblow and her persistent, passionate problem-solving.” She continued: “Mr. Rao, your spreadsheets, neural networks, and databases are powerful tools. With respect, you are not correctly employing them. First is the problematic assumption that coal-based empirical relationships for ash resistivity can be used for predictions with biomass. The ash mineral analysis is deceptive in this case. For example, silica in coal points to the presence of hard-rock minerals, or even clays and shales, with melting points above 1,600C. In biomass, however, silica may take on glassy, alkali-lime forms, melting below 1,100C. This is why it is not proper to attempt predicting slagging and fouling in the boiler by using coal-based indices for biomass fuels. To assist you so you need not repeat her effort, she has provided many research papers to guide you, which I e-mailed to you just before this meeting.” A minute later, Mr. Rao nodded as he found Maya’s e-mail on his laptop. “This all may be true—I will need to examine the research—but what is the reason for our varying ESP performance?” he asked. “Potentially many reasons,” Maya responded. “Here is my conclusion after studying a multivariate solution. First, there is a misperception that ammonia changes ash resistivity. Aside from some unusual cases, ammonia has the effect of combining with sulfur and forming ammonium bisulfate. This is the very sticky substance found in air heaters downstream of ammonia injection grids. But ammonium bisulfate requires sulfur to combine with, and thus, for low-sulfur fuels, ammonia’s impact can be even less.” “Then why does adding more ammonia cause the ESP performance to decrease sometimes?” asked one of the operators. “Because when your ammonia concentration is high relative to sulfur, ammonium sulfate, which is less sticky than its bisulfate auntie, begins to form,” explained Maya. “You are saying ammonia does not reduce ash resistivity. That is different than we were told,” Mr. Mankar said dubiously. “It depends on the type of ash,” Maya countered. “In most cases, no—the effect is reducing the resistivity of the flue gas, also called the space resistivity. This reduced space resistivity allows an increased effective operating voltage, giving improve charging of ash particles.” Maya paused, then said, “Humidification of the flue gas, via burning higher-moisture fuels or fuels with more hydrogen in them, will also reduce space resistivity. However, the moisture and ammonia are not additive in effect. Higher flue gas moisture has been found to reduce ammonia’s effectiveness via several methods, which depend upon the specific fuel being fired. And there’s still more impacts to consider, which can be strongly influenced by changes in the flue gas velocity, temperature, and other mineral compounds in the ash. Namely, every different fuel you burn may require a set of customized ammonia injection curves.”

2. With so many variables to consider, Mr. Rao needed Maya’s encouragement. Source: POWER

Despite having been given powerful clues to help them solve their ash emissions problem, none of the engineers seemed happy upon learning there was not a single, simple trendline to draw. “What are we to do?” cried Mr. Rao, as he sat and held his head (Figure 2). Mr. Mankar walked up and placed a hand on his shoulder, speaking reassuringly to him, the station manager said, “You will do what you have always done. You will collect the data, arrange it, and develop those ammonia injection curves.” “Mr. Rao, by using your very clever RFID fuel tracking system, I am certain you shall be able to correlate the fuel data with many other operations variables of the ESP system and find the multivariate equations to develop your own set of curves. And given your capabilities, I feel confident you can incorporate these seamlessly into the power station emissions control systems,” Maya reassured the young engineer. “May I now share with the group some outlines of the path forward I developed this morning?” she asked.

A Delightful Day, but Clouds on the Horizon

Saturday morning found Maya resting on her father’s porch, sipping orange juice with her auntie Komal. Her father joined them, and the three sat in comfortable silence, looking across the orange fields at the stack of the biomass power station in the distance. While not completely clear, the ash was already much less visible as the station operators and engineers diligently worked to find the best way to balance their emissions. It was a perfect, idyllic day. Yet, Maya frowned. She remembered Marnie’s final words at the end of their video call the previous night: “Rest well, so you’re in top form kiddo. Our next job is going to be one of the hardest ever.” Even in the heat of a Nagpur May, Maya shivered.

—Una Nowling, PE is an adjunct professor of mechanical engineering at the University of Missouri-Kansas City.