Transcript
Did you know the foundation of your house once looked like this? Well, this is a 300 million year old piece of limestone, and today, we're gonna go onto this plant and show you how you take this piece of limestone and turn it into cement. They've been producing cement on this hillside near Santa Cruz, California for more than 90 years. The plant that's in operation today is owned and operated by RMC Lonestar, the world's largest producer of ready-mix concrete. And it uses the most high-tech and environmentally sensitive processes available in modern cement making. In operation 24 hours a day, seven days a week, this plant produces nearly one million tons of Portland grade cement each year. The view of the Pacific Ocean is breathtaking from the observation deck of the plant's 300-foot tall tower. That's where we met up with General Manager, Chris Crouch. Well Chris, it looks like some of these buildings have been around here for a while. This looks like a pretty historic site here. Tell me a little bit about the history of this plant.
The original plant was put together in 1906 and it was put together to supply the Panama Canal and the construction of the Panama Canal, but as you recall, in 1906 there was another little event that happened in San Francisco, and it was the great earthquake. And so, what ended up happening is the plant, the original plant that was constructed, most of the cement went to go rebuild San Francisco and subsequent structures, Golden Gate Bridge, the Bay Bridge and other buildings. In this location since the 1906, there have been three separate plants. The first plant had 24 kilns, these rotary kilns. And the next plant, which was built in the, in the early 50's, was built with three kilns that actually produced more than the 24 smaller kilns.
And the kilns are what they do to fire the cement, isn't it?
That's the rotary oven and the tubes that we'll be looking at further on our tour. Subsequently in 1980, '81, we opened the operation that you're gonna see today.
The first step in cement making is the mining of the raw materials. This quarry is located three miles from the plant where they harvest limestone and shale. Huge boulders of limestone and shale, some as large as a piano, and weight several tons, are dumped into a machine called an impact crusher. After the limestone and shale are pulverized, they're transported to the plant through a long series of conveyor belts. The limestone and shale, along with small amounts of iron ore and clay are loaded into this huge rotary kiln. It's 185 feet long and 13 feet in diameter. Temperatures inside the kiln soar to nearly 3,000 degrees. This causes a chemical reaction in the raw materials as they slowly begin transforming into cement. So this feels really hot.
How hot does this get? Well, steel starts to deform at about 1,100 degrees and, and actually melts at about 2,000 degrees, approximately 2,000 degrees. And so what we do to keep this core, this shell from, from melting on us and deforming on us, is we line the kiln with refractory brick. The brick, the steel is on the outside and the actual thickness of the brick, in this case nine inches, is the whole diameter all the way around. These bricks are put in interlocking with, with one another. There's no mortar in between these bricks and they're built up around the shell all the way up to the top where you slide in the keystone. And just through the sheer interlocking they hold themselves together.
And so this brick actually insulates that steel from the intense heat of the kiln.
Let's go take a look and see how hot it gets.
At this point in the process, the cement compound is called clinker. Tell me what's going on here. I see the kiln rotating and I see material falling out of it.
What you're looking at is the absolute back end of the kiln. The flame is shooting into the kiln and that material right there is, is the fully processed material just falling out of the rotary kiln and down into the clinker cooler where we'll subsequently cool it off and then reprocess.
So then, to get a fire this hot you have to use this uh, atomizer ground-up coal right, shot into it, into a burner?
We take our coal; grind it into a fine, fine powder. That way it, it first of all ignites faster as well as it generates the maximum amount of heat that we can.
The firing process is closely monitored inside the plant's state-of-the-art control center. Television screens allow the technicians to actually see inside the kiln and monitor the amount of heat that's being generated.
Steve, we're at the bottom of the clinker cooler. That molten material you saw coming out of the kiln has gone through several grates that...with cool air blowing up underneath it to cool the material. Obviously you can see that some of this material has yet to fully cool. It's still relatively hot. I have some extra material here for you to take a look at, but this is clinker.