Chapter 294 Dome Kiln

In Adhania, the bricks would be fired in small batches of ten to hundred pieces in tiny furnaces.

This was because the rulers of his country never bothered to industrialize brick production.

One, because it was a somewhat capital-intensive process, and two, more importantly, because they were rich enough to afford stone.

Hence bricks were relegated to the sidelines, only produced by poor individuals who usually produced them for their personal kilns using small homemade furnaces.

Alexander let these micro kilns operate for the first few weeks to get the workers used to the brick-making process and also because he needed the initial building material.

But he had little idea the production rate would be so abysmal, and hence decided not to wait any longer and chose the commencement of the dome kiln.

His current design of the kiln was capable of producing 20,000 pieces of bricks a day, and according to his calculations, these bricks would be far cheaper than stone.

He came to this conclusion by first estimating that the kiln would have a fuel consumption rate of 500kg of firewood per ton of brick.

Alexander could get this theoretical value because he had a rough idea of the energy used to make a ton of bricks and the energy density of dry firewood.

Hence, given such consumption, and knowing 10kg of firewood went for 1 ropal, that came to 50 ropals per ton in fuel cost.

And then after taking into account all other costs, ranging from the raw materials to manpower to the kiln construction cost, Alexander got the cost of one ton of brick at around a nice whole 80 ropals.

Which was quite cheap, about one-fifth the cost of stone, which sold for 350 - 400 ropals a ton.

The reason for such a high price of stone was because a miner had to be paid a minimum of 6 ropals a day and could only extract 20-25 kgs of stone a day.

And if one used slave labor, excluding the cost of buying the slave, his master would also have to at least spend 3 ropals a day feeding the man to enable him to do such physically tiring work.

Thus the dome kiln was a huge step forward in the branch of civil engineering.

Though it could be argued Alexander's choice for this particular brick kiln was not the most optimum one.

A far better alternative kiln existed called the Hoffman's ring kiln, which was in many ways better- being faster, more fuel efficient, and one which did not need its entrance to be smashed open every time.

But Alexander had skipped on that for the time being due to the complexity of its design, and its much greater requirement for time and construction materials, both of which Alexander was short of.

And though the dome kiln was inferior to the ring kiln, it was still not a bad kiln and certainly adequate for his current needs.

In fact, given the simple operating procedure of the dome kiln, the reverse argument that it was in fact the superior choice could be made.

And the operation of the kiln was indeed very simple.

The way the kiln worked was at first, the brick would be placed in stacks inside the kiln.

This stack would not be just bricks placed parallelly atop each other, but in a perpendicular way, with some gap between adjacent bricks.

Such a method was needed to allow the hot gases inside the kiln to properly come into contact with all the sides of the bricks and cook them evenly.

In fact, the reason why bricks would have holes in them was exactly for such, to permit the passage of air through them and enable them to be cooked more quickly and evenly.

Once the bricks were properly stacked, the entrance would be sealed, and the stoves fired, slowly bringing up the kiln to firing temperature in this preliminary stage called the preheating phase.

This phase, even with all six stoves running, would take approximately ten to fifteen hours (10-15 hrs) as the area inside the furnace was huge, thus slowly bringing up the temperature up to the appropriate range.

And this time would not be wasted as within this time period, the green bricks would dry and relieve themselves of a large portion of the moisture.

pαпdα Йᴏνê|,сòМ After this, much more firewood, sawdust, or even coal would be added to alleviate and keep the temperature at a much higher level, and the bricks would be burned for thirty to forty hours (30-40 hrs) at around 700 to 900 degrees Celsius at this stage.

This would complete the firing, and the stoves would be turned off, after which the bricks would be allowed in the kiln slowly for an additional one to two days.

Throughout this entire process, the sealed dome would be provided with fresh oxygen through a network of pipes connected to a chimney on the outer walls of the dome, the pipes themselves connected to the six stoves which would draw in air by a natural draught.

And this natural draught would be created because there would be a tunnel right below the dome that connected to another large chimney some distance away through which all the hot, pent-up flue gases would escape to the outside, thus creating a low pressure inside the dome which would suck in fresh, cold air from the outside.

This additional chimney performed another critical job, as without it letting all the gases escape, the dome would become one giant sealed pressure cooker, thus turning it into a giant time bomb.

And one last keynote here would be that unlike in the cement kilns, there would be no need to use blowers here as such application would raise the kiln temperature too much and overcook the outer surface while keeping the insides raw, destroying the bricks.

This would be because blowers could raise the temperatures to almost 1600 hundred degrees Celsius, whereas the optimum temperature for brick burning, i.e- the temperature along which vitrification or the reactions that turn clay into bricks takes place in the range of 700 to 900 degrees Celsius.

Receiving Alexander's direction, Krishok got down to knowing about the details.

"My lord, how many men will I have? And how fast do you want me to finish it?" Krishok asked.

"I have ordered the five thousand miners in the quarries to switch to other jobs. You can employ a part of them," Alexander spoke, adding, "By my estimate, the dome will need 100 tons of materials and can be constructed by a hundred men in a few days."

His voice then turned casual and breezily, a clear indication he was about to say something absurd, "So, you will choose a thousand men for now and simultaneously build ten of these within the next week."

"...." Krishok went silent for a while as Alexander certainly delivered on his promise of being absurd.

'There he goes again with these ludicrous deadlines,' Krishok lampooned at his demanding master.

This new master of his was perfect in every way- generous, pleasant, courteous, and supremely competent.

Well almost perfect as his one flaw was that he drove those under him like slaves, setting absurd goals and expecting all others to comply.

Krishok thus tried to squirm some more time for himself, "Your Grace, I also have the cement kilns and experimental armors to make. So..."

But he did not get to finish his request as Alexander curtly interjected, "If you are too busy like Jazum, just say so. I will find someone else."

Alexander's brusque tone and damn care attitude made Krishok feel that Alexander could easily choose another over him if he failed to deliver on time and so he immediately changed his tone, making a complete u-turn as Krishok hastily replied, "No, no, milord. It's alright, it's alright, I will get started on the kilns as soon as possible."

"Mmmn, good," Alexander approved with a nod and a light smile, advising, "Diaogosis will not need the stones anytime soon. So, use those to make the kilns."

Alexander planned to build the initial kilns using stone and then switch to bricks once they became more readily available.

"As you command." Krishok this time obediently replied, and then cleverly asked, "Is there anything else?"

"Yes, in fact there is." Alexander gave a light smirk that made Krishok involuntarily shiver.

"One is the number of brick kilns," He began,

"As I said before I want to have the capability to make one million brick pieces a day. You must build enough kilns to get me that capacity. I estimate it would be around 50 kilns."

The confirmation of Alexander's desire turned Krishok a little pale, as it would mean the processing of 2,000 tons of clay and 1,000 tons of firewood.

Never an easy task.

And Alexander certainly noticed this, and so decided to soothe the man with some easy maths,

"One million bricks might sound like a lot, but even a decent brick maker can mold 6 bricks a minute. Experts can even do 9-10. And that means a minimum of 3,500 bricks can be made by each worker per day,"

"So, you will need only 300 brickmakers to make a million bricks."

"And then comes the diggers. Given that they can dig close to 2 tons of dirt a day, let's say another 1,700 will be needed to do everything else, from the digging to cleaning the clay to running the kilns."

"So, don't get scared by the large numbers. It will be very easy." Alexander helped alleviate Krihsok's fear by patting the man's shoulders repeatedly, to which the man agreed with a weak, anemic nod.