By noon the following day, the coal carts stopped rolling.
Instead of the heavy, black glass-black carts laden with high-grade Black-Flame Coal—the dense, hard coal-grade spirit fuel mined from the deep underground veins of the Iron Sword Mountains—the intake depot was dumped with three dozen rattling wagons of green pine charcoal.
The pine wood was wet, light as foam-stone. Then it crackled with spitting sparks that left greasy grey ash over the flat stone slabs.
Elder Wu DeZheng stood at the edge of the smelting ramp. He grabbed his greasy hair with both hands, his official cap knocked fully askew.
“Seventy percent moisture content!” Wu shrieked, his voice echoing off the blast walls like a dying crane. “The Grand Fortune transport depot says their mountain haulage lines suffered an ‘unexpected winter landslide’! They diverted every single cart of Black-Flame Coal to the Second Ward!”
The elder grabbed Lin Ke’s grey linen sleeve, shaking him with frantic fury.
“Do you know what this means, boy? The pine charcoal can’t sustain a bed heat above nine hundred degrees! The melt threshold for grade-three spirit iron is fourteen hundred! We won’t produce an ounce of refined bloom! Our quarterly quota will fail by sixty-five percent!”
Wu dropped to his knees in the pine soot, tears of sheer office terror streaming down his flabby cheeks.
“The Central Treasury will suspend my old family pension bonus,” Wu wailed, rocking back and forth. “Four years and one month left! They’re going to forfeit my retirement plot and bury me in a common ditch!”
* * *
Lin Ke gently, firmly, pried the old elder’s trembling fingers from his sleeve.
“Elder Wu,” Lin Ke said, his voice level and steady as a granite stone base. “Stand up. Laborers are watching.”
Wu sniffled, wiping snot onto his silk cuff. It looked up at the seventeen-year-old clerk with red-rimmed, pathetic eyes. “How can I stand? We’re dead! The furnaces are dead!”
“The furnaces are running under a glitchy single-pass heat-powered stonework,” Lin Ke replied.
He reached into his leather archive satchel. Then he pulled out a large, heavy scroll of thick drafting paper. He unrolled it across the top of an overturned pine charcoal barrel, weighing down the corners with two iron chunks.
The scroll was covered in crisp, spotless building schematics drawn in black India ink.
“Look at this cross-section,” Lin Ke instructed. He tapped the top of the drawing with a charred pine splinter. “Under current operations, Kiln Nine draws cold mountain air through the lower draft gate at fifteen degrees. That cold air hits the burning bed, absorbs heat, burns the fuel, and exhausts directly out the upright chimney pipe.”
Wu blinked through his tears, squinting at the drawing. “Of... Of course it exhausts. That’s what chimneys do! They carry away the smoke!”
“They carry away forty-five percent of your total heat energy,” Lin Ke countered coldly. “The chimney pipe gases leaving Kiln Nine exit at six hundred and eighty degrees. You’re throwing half your fuel budget directly into the sky to heat clouds.”
Wu frowned, his office mind struggling to grasp the concept of heat loss. “So... So what do you propose? Cap the chimney? The smoke will suffocate the crew!”
“A recuperative waste-heat exchanger,” Lin Ke said.
He tapped the center of the blueprint.
Inside the main upright exhaust chimney pipe, Lin Ke had drafted a fine, detailed, multi-tiered maze of linked baked-clay plates—a three-pass counter-current baffle system.
“We install fireclay baffle plates inside the exhaust shaft,” Lin Ke explained in plain, physical terms. “The hot waste smoke is forced to snake through a winding upright maze before exiting. Parallel to the smoke path, we build backup air intake channels lined with heat-proof brick.”
Lin Ke traced the airflow with the pine splinter.
“The cold incoming air is drawn through these baked-clay channels before it touches the firebox. As it passes alongside the hot exhaust baffles, it absorbs radiant heat energy from the exiting smoke. By the time the intake air reaches the charcoal bed, it’s already preheated to five hundred degrees.”
Elder Wu stared at the drawing, his mouth working silently.
“Preheated air...?” Wu whispered.
“If the burning air is already at five hundred degrees, the fuel doesn’t need to waste energy heating the draft,” Lin Ke finished. “Even low-grade pine charcoal will achieve a bed heat of fifteen hundred degrees. We bypass the Black-Flame Coal monopoly entirely. And because we’re recovering waste heat, overall fuel consumption drops by twenty-two percent.”
Lin Ke flipped open an official cost-benefit analysis docket. It slid a dry horsehair brush into Wu’s hand.
“Estimated working savings: forty-two low-grade spirit stones per month. Document classification: Energy Smooth speed and Waste Reclamation Directive 19-A. If approved, it qualifies your office for an office innovation commendation from the Central Logistics Board... Which carries an extra seven-percent pension multiplier.”
The word multiplier hit Elder Wu like a bolt of divine lightning.
The old bureaucrat didn’t hesitate. He snatched the brush, jammed it into his portable inkpot. Then he signed his full office signed name across the bottom of Directive 19-A with such ferocious force that the paper nearly ripped.
“Approved!” Wu shouted, slamming his bronze seal into the wax. “By the Heavens, approved! Take every piece of heat-proof clay in the warehouse! Supply order twenty mason apprentices! Build the baffles before the Grand Fortune bastards realize what we’re doing!”
* * *
Two hours later, Lin Ke stood at the base of Kiln Nine’s main chimney.
The heavy, four-foot-wide baked-clay baffle plates had been hauled from the storage cellars, stacked neatly on the flat stone slabs. Each plate was three inches thick, cast from dense fireclay and grooved with heat-exchange channels, weighing nearly eight hundred pounds.
The master mason from the construction crew wiped sweat from his beard. He looked up into the dark, towering stone chimney with dread.
“Clerk Lin,” the mason said, shaking his head grimly. “The blueprints are genius, but we have a fatal problem.”
“Explain,” Lin Ke said.
“Kiln Nine can’t be put out,” the mason said. He gestured toward the muffled roar rumbling through the base stonework. “If we shut down the firebox fully to let the chimney cool, the heat shock will crack the four-hundred-year-old crucible lining. The fire must stay at minimum idle.”
The mason tapped one of the eight-hundred-pound baffle plates with his hammer.
“The air inside that exhaust shaft right now is four hundred degrees. A man has to climb sixty feet up the inside iron rungs, hoist this eight-hundred-pound plate into position, and drive four steel anchor bolts into the granite walls while breathing pure sulfur fumes.”
The mason spit into the soot, his eyes hollow.
“A mortal laborer would roast like a pig on a spit within forty seconds. His skin would blister, his lungs would cook. He would drop eighty feet to break his neck on the fire grates. Nobody in the Seventh Ward can carry eight hundred pounds into a four-hundred-degree oven.”
Lin Ke didn’t look at the mason.
His eyes flicked across the smelting floor, past the carts of wet pine charcoal, toward the far corner of the yard where a towering, broad-shouldered figure was silently shoveling melted rock waste with clockwork, uninterrupted rhythm.
Meng Shan.