To produce coke

Compared to Li Zhi, who gained both fame and fortune, Li Tai could be said to have suffered a great loss. His long-running furniture workshop had not only failed to bring him profit, but in order to silence the gossip of the people of Chang’an, he had been forced to kill Dou Xin in a fit of painful necessity. Thus, the newly appointed steward became Li Tai’s scapegoat.

After Li Zhi took over Li Tai’s workshop, he did not use the “Linde” brand for this establishment. Instead, he named it “Xianheng,” meaning a smooth and prosperous business with abundant wealth. He specially designed a collection of furniture styles suitable for ordinary merchants and common folk, entrusting their production entirely to this workshop.

Although the individual purchasing power of commoners was not high, their numbers were vast. Thus, once these pieces of furniture entered the market, they were quickly embraced. Other woodworking shops sought out Pei Mingli to purchase the rights to use these furniture designs, which allowed Li Zhi to make another handsome profit.

However, at this point, Li Zhi no longer paid much attention to such matters. Apart from fulfilling his daily studies and his task of revising legal codes, his greatest pleasure each day was to retreat into his own “treasure chamber.”

Ever since he had instructed Liu An to collect curiosities for him, Liu An would often use his trips outside the palace to see Pei Mingli as an opportunity to scour the markets and districts of Chang’an for rare finds. By now, he had already gathered quite a collection for Li Zhi. Among them were not only precious pearls and gemstones, but also rare minerals, as well as various plants, flowers, and seeds. Of these, the only items Li Zhi could immediately identify, apart from the jewels, were coal, cotton, and some common ores.

Li Zhi merely glanced appreciatively at the jewels before giving them, without hesitation, to Empress Zhangsun, the other consorts of the harem, and to his sisters such as Li Lizhi. The concubines in the harem could not help but sigh that their kindness to Li Zhi in his childhood had not been in vain.

What Li Zhi truly cared about was the coal, the cotton, and those seeds he had yet to recognize. With autumn deepening and winter fast approaching, the matter of heating would soon become a pressing concern for the people of Chang’an. Charcoal, which was the most commonly used fuel, was far too expensive for most ordinary people. Each winter, people could only burn firewood to keep warm for brief periods during the night.

It was true that some people had begun experimenting with coal, but due to the improper use of it, fatalities were not uncommon. Thus, coal had never become widely adopted.

Yet none of this posed any difficulty for Li Zhi, who came from a later age. In just a few days, he effortlessly produced coke. There was a reason why Li Zhi chose to make coke: the steel production of the Tang dynasty was still quite low, and even supplying the military’s needs was a struggle. The idea of ordinary people using large quantities of iron tools was simply unrealistic. By producing coke, Li Zhi aimed to present it to Emperor Taizong, so that it could be used to improve the fuel for iron smelting. Because coke has a higher thermal efficiency than charcoal, it could greatly increase the efficiency of iron production.

Li Zhi planned to use this opportunity to gradually involve himself in the iron industry of the Tang dynasty, so that he could use his knowledge to continuously improve its technology. Once steel production increased, further industrial development could proceed much faster, and the people of Tang would have access to cheap steel to improve their lives and work.

While addressing the fuel issue in iron smelting, Li Zhi also planned to have Liu An collect more cotton seeds. He intended to experiment with planting them the following year, and then look for an opportunity to develop cotton thread. In this way, the Tang dynasty would gain a new kind of fabric and a new material for warmth.

When Li Zhi presented the coke to Emperor Taizong, the emperor was both delighted and astonished. He found himself increasingly unable to understand his son, who always seemed able to create things that no one else had ever imagined. It was hard to fathom how one so young could possess such a brilliant mind.

Emperor Taizong examined the coke for a long time, unable to suppress his curiosity. At last, he asked, “Zhinu, tell your father—how did you come up with the idea of using coal to make coke?”

Li Zhi replied, “Father, winter is coming, and your son noticed that in the palace, charcoal was never used in large quantities in previous years. So I wanted to find a cheaper material for heating.”

Hearing this, Emperor Taizong’s face showed a hint of shame. But Li Zhi did not give him time to dwell on it, and continued, “I heard that coal is inexpensive and already used among the people, so I thought I’d give it a try.”

He paused, a look of contemplation on his face, then said, “Father, when I burned coal, I found that, like firewood, it produced thick smoke and a strange odor.” Here, he deliberately wrinkled his nose and complained, “The smell is terrible.”

Li Zhi continued, “Liu An told me that burning coal for warmth easily results in death, which piqued my interest and made me want to study it further.”

Emperor Taizong asked, “So that led you to think of making coke?”

Li Zhi replied, “Yes, Father. I thought, since firewood can be turned into charcoal, could coal not also be made into coke?”

Emperor Taizong, surprised, asked, “And you succeeded so easily?”

Li Zhi feigned indignation and said, “How could it be so easy? I had to try many times!”

Emperor Taizong laughed heartily, saying, “Not easy, indeed not easy. My son has accomplished yet another feat unknown to the ancients.”

He laughed several more times in delight before finally asking, “How does this coke compare to charcoal?”

Li Zhi answered, “Coke is much better than charcoal; it burns longer, is less likely to go out, but is more troublesome to make.”

Upon hearing this, Emperor Taizong’s interest was immediately piqued. He quickly ordered a brazier to be prepared and began testing the coke outside the Taiji Hall. The results came quickly: except for being a bit harder to ignite, coke surpassed charcoal in every respect.

Li Zhi then explained the method for producing coke. When Emperor Taizong learned that cheap coal could be directly used to make coke, his eyes lit up. Just as Li Zhi had anticipated, the emperor soon realized the potential of using coke to replace charcoal in iron smelting and immediately set things in motion.

Emperor Taizong was becoming increasingly fond of Li Zhi. Even disregarding everything else, the surprises his son had brought him in just the past few months were more than enough. At this moment, Emperor Taizong had secretly decided that during the next round of collective ennoblements, he would prepare a grand surprise for Li Zhi.