The Enigmatic Shadows of Panzhou: A Coal Preparation Plant  Adventure of Two Female College Students (1)

1. Prologue

In the city of Pan County, Liupanshui, Guizhou, there is a coal preparation plant hidden deep within the mountains—the Jichangping Coal Preparation Plant. Here, far from the clamor of the city, the mountains rise and fall, shrouded in mist, as if time itself has slowed to a halt within the embrace of nature. Yet, behind this tranquility, undercurrents stir. Two female college students, armed with their dreams and knowledge, have arrived at this secluded factory for an internship, ready to tackle the challenging issues faced by the coal slurry system.

Gu Xiaotong, a junior majoring in Mineral Processing Engineering at China University of Mining and Technology (Beijing), is intelligent and full of curiosity. Accompanying her is her best friend and academic partner, Li Xiaoning, a mechanically inclined engineering student. Though they know little about the coal industry, they are brimming with passion and determination to make their mark. However, the reality is far more complex than they had imagined.

2. First Steps into the Mining Area

The morning sunlight filtered through the thick clouds, casting a golden glow over the mountains of Pan County. Gu Xiaotong and Li Xiaoning stood at the entrance of the Jichangping Coal Preparation Plant, feeling a deep sense of awe as they took in the scale of the industrial facility before them.

"Xiaotong, do you really think we can make a difference here?" Li Xiaoning asked nervously.

Gu Xiaotong took a deep breath and nodded firmly. "We can do it. As long as we're not afraid of challenges, these machines and processes are just things that take time to learn."

As they stepped into the plant, they were met by Director Wang Zhiqiang, a stern-looking man in his late forties. His eyes reflected the steadiness of someone who had weathered many storms, but beneath his strict exterior was a heart willing to give young people a chance.

"I hear you're here to solve the coal slurry system problems," Director Wang said in a deep voice. "Our system has needed an upgrade for a while now, but be prepared—this won't be easy."

3. A Rough Start

Within just a few days of getting into the swing of work, Gu Xiaotong and Li Xiaoning encountered challenges they had never faced during their university studies. Their first experience with dense medium coal preparation left them almost at a loss. The proper ratio of dense medium, the efficiency of slurry separation, the operating parameters of the settling tank—these were once mere textbook concepts but now presented daily challenges.

"I honestly don’t know where to start," Li Xiaoning said, scratching her head as she stared at the complex control system display in front of her.

"Don’t get discouraged," said an older worker, Master Chen, who had worked at Jichangping for over thirty years. Despite never having received formal higher education, his wealth of practical experience had made him the plant’s "living encyclopedia."

"Seeing you two young ladies working so hard, I’m happy to teach you a thing or two," Master Chen said with a smile as he pointed to the equipment. "The most important things here are attention to detail and experience. Just stick with me, and take it slow."

4. Rising to the Challenge

Under Master Chen’s guidance, Gu Xiaotong and Li Xiaoning gradually adapted to the production rhythm of the coal preparation plant. But soon, they discovered a more serious issue—the coal slurry system was operating beyond its designed capacity. During peak production times, the surge in secondary coal slurry production nearly crippled the entire system. They knew this was more than just a matter of production efficiency. As the discharge of coal slurry water increased, so did the environmental pressure.

To solve the problems plaguing the coal slurry system at Jichangping Coal Preparation Plant, Gu Xiaotong and Li Xiaoning began by thoroughly researching the plant’s coal slurry treatment process, operating parameters, equipment performance, and maintenance history. They delved into the operational principles of the coal slurry system, including the basic structure of the coal slurry treatment in the plant, the roles of the subsystems, and their interrelationships. They also carefully reviewed the system’s operating reports and the original design documents of the coal preparation plant.

The coal slurry system at Jichangping Coal Preparation Plant consisted of several critical processing units, including dense medium cyclones, centrifuges, thickening tanks, filters, and dosing systems. The primary goal of the coal slurry system was to separate the coal slurry from the water while ensuring the recovery of the separated coal particles. They discovered that the current system, having been in operation for many years, suffered from issues such as aging equipment, low separation efficiency, and slow settling rates. These problems were particularly severe in the treatment of coal slurry produced during wet coal preparation, where the processing capacity was nearing saturation.

Coal Slurry Treatment Process

Dense Medium Cyclone: This equipment is primarily used to separate coal from the dense medium. However, due to the complex coal quality at the Jichangping Coal Preparation Plant, the separation effect is often unsatisfactory. Many fine coal particles are not discharged in time, leading to increased load on the subsequent equipment.

Centrifuge: The centrifuge is used to accelerate the separation of fine coal particles. However, the centrifuge at the plant operates inefficiently and frequently experiences blockages.

Thickening Tank: This tank is used to separate solid particles from the coal slurry by sedimentation. The main issue with the thickening tank is the slow settling speed, especially when the fine coal particles are very small, making it difficult to achieve the desired sedimentation effect.

Filter Press: The filter press is one of the final treatment devices, responsible for separating the solid and liquid in the thickened coal slurry to obtain relatively clean supernatant water for recycling. However, due to a long period of inadequate maintenance, the filtration efficiency of the equipment has significantly decreased.

Dosing System: This is a critical step in improving the treatment effectiveness of the coal slurry. The type of chemical agents used, the dosage, and the injection points directly affect the treatment outcome of the coal slurry.

The aging and uncoordinated operation of these devices have led to frequent issues in the coal slurry system at the Jichangping Coal Preparation Plant. During a crucial production improvement effort, Gu Xiaotong and Li Xiaoning discovered that the existing dosing system had significant flaws. The dosage of chemicals was either excessive or insufficient, directly affecting the efficiency of the thickening tank.

More importantly, they found that the original design of the coal preparation plant underestimated the complexity of coal in Guizhou Province, particularly the degree of fines generation and secondary fines formation. The design phase of the coal slurry system had simply copied parameters from northern coal preparation plants or followed standard design codes without considering the specific coal characteristics of the region. For instance, the equipment selection considered an imbalance coefficient KKK of 1.25, based on standard design norms. However, after analyzing the onsite data, Xiaotong and Xiaoning calculated that the minimum imbalance coefficient needed for the smooth operation of the coal slurry system at Jichangping should be 1.8, and this figure did not even account for the additional complexities introduced by washing external coal.

5. The Legend of Guizhou

Through their tireless efforts alongside the workers, Gu Xiaotong and Li Xiaoning redesigned the control program of the dosing system, implementing more precise automated equipment capable of adjusting the chemical dosage based on the concentration of the coal slurry. They also utilized computer simulations to optimize the design of the thickening tanks, improving the sedimentation of particles. These improvements significantly enhanced the efficiency of the coal slurry system, dramatically reducing its failure rate.

During this time, the two young women also stumbled upon some ancient legends in the mountains of Pan County. According to local lore, deep within these mountains, there once lived a mysterious figure known as "General Pangu." He was said to have led miners in extracting precious minerals from the mountains while also serving as the guardian of the land. Many of the elderly locals spoke of him with a sense of deep reverence.

"Do these legends have anything to do with our work?" Li Xiaoning asked while chatting with an elderly local.

6. Night Shift Horror

In the quiet of the night, Gu Xiaotong and Li Xiaoning were on their first night shift alone in the coal preparation plant's control room. The factory, usually bustling during the day, was now eerily silent, with the occasional low hum of machines echoing through the darkness, creating an oppressive atmosphere. The lights in the filter press workshop flickered ominously, as if forewarning something unsettling.

"Xiaoning, why are those lights flickering over there?" Gu Xiaotong asked with a hint of unease in her voice as she stared at the monitor. The lights in the filter press workshop blinked erratically, almost as if malfunctioning. Suddenly, a shadow swiftly darted across the screen.

"Oh my god! What was that?" Gu Xiaotong screamed, jerking back in her seat, nearly dropping her water cup.

Li Xiaoning quickly leaned over to the monitor, her heart pounding as she saw the shadow as well. "Could it be...a ghost?" Her voice trembled.

Gu Xiaotong’s heart raced, and the once calm factory now felt shrouded in an inexplicable chill. The only sounds around them were the hum of the machines, with the darkness seeming to swallow everything else.

As they tried to steady their nerves, the door of the control room suddenly burst open with a loud bang, the doorframe rattling and producing an eerie creak. The two girls exchanged fearful glances, with Gu Xiaotong feeling an icy shiver run down her spine. They no longer cared about the monitors; all they wanted was to escape the room.

Just then, "Old Worker" Uncle Li, who was on patrol, passed by and noticed their pale faces. He frowned, "What are you two up to? Why do you look so scared?"

"Uncle Li, there’s something in the workshop!" Gu Xiaotong pointed at the monitor, her voice trembling. "The lights were flickering, and we saw a shadow...we don't know what it was!

......

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