Pyroprocess

CLAY CALCINER

Clinker production is a particularly carbon intensive process. Reducing the clinker content of cement is therefore considered a key part in lowering the industry’s climate impact. It is a job that calcined clay is well suited to. It has similar cementitious properties but, unlike clinker, emits no carbon during calcination, while energy and fuel requirements are also lower.

Pyrotop® mixing chamber

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High-efficiency cyclones

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Separator

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Hammer mill

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Clay Calciner Components

We developed our new clay calciner from proven components for best possible energy efficiency and quality control. Read here what’s part of the clay calciner.

Clay Calciner Components

It’s hammer (mill) time: raw material preparation

Clay is not the easiest material to handle. Picture a potter’s wheel and you will appreciate the challenge. Throwing a bowl or vase from an unformed lump of clay is the job of an expert. And while you don’t need to be as delicate when preparing clay for calcination, being an expert in the process – that is always a benefit.

We start with an impact hammer mill – our robust and proven solution for crushing, deagglomerating and drying wet and lumpy materials. In fact, our mills can easily handle very moist materials (up to 30 %). And for added efficiency, heat from the pyroprocess is recovered and used to dry the raw meal.

Clay Calciner Components

Separator

Depending on your raw materials, a separator may or may not be needed. For example, for soft clays a separator will probably not be required. Our process experts will always check the physical properties of your raw materials to determine the best process design for your unique circumstances.

When a separator is required, our clay calciner comes equipped with our reliable LS static separator. With low power consumption and almost no maintenance, the LS separator is our go-to choice for efficient separation in raw material grinding applications.

Clay Calciner Components

Preheating: high-efficiency cyclones

It is time to turn the heat up. Dry clay powder is preheated by counter-flowing hot gas in high-efficiency cyclones, before moving into a tube calciner, where it is calcined – or dehydroxilated if you prefer the technical term.

Our cyclones provide best-in-class heat transfer and pressure drop, all while reducing weight, footprint and volume. We have also made maintenance a relatively easy prospect. Our cyclone cone features a 70° incline and extended distance between dip tube and cone tip – both features that prevent build-up without needing a vortex breaker.

A further innovation is that prestressed cyclone ceiling, which limits wear and improves operational safety, as proper compensation for thermal stress is always guaranteed. In contrast, standard expansion joints require repeated and time-consuming maintenance.

Clay Calciner Components

Pyrotop® mixing chamber

Proper mixing of material and gas brings a number of benefits from complete burn-out of CO to allowing higher use of alternative fuels. Fitted to all KHD calciners, the Pyrotop mixing chamber delivers those benefits. It does so while achieving lowest possible pressure loss. In other words, it is a useful box of tricks to sit atop your calciner.

Key Benefits

Calcined clay may be a big step on the road to climate-neutral cement. But our clay calcination system also offers some specific operational advantages.

Key Benefits

High performance, low maintenance

Our clay calcination system is a quintessential KHD solution. It combines proven equipment with process engineering excellence to offer simple, reliable operation and low maintenance needs. And because its components are adapted versions of existing parts of the clinker production line, your operators and engineers will already be familiar with them.

Key Benefits

Reduce energy and emissions

Like clinker production, clay calcination requires heat. But there is a huge different in scale. In the cement kiln, temperatures reach over 1500 °C; clay is calcined at 700-850 °C.

In fact, calcined clay production consumes less than half of the specific thermal energy of clinker production. Which is a big deal. Fuel and energy consumption are significantly lowered, resulting in much reduced OPEX. It all equates to lower production costs and emissions per ton of cement.

Key Benefits

Same color and performance as ordinary Portland cement

One of the problems of calcined clay in the past has been an unwanted reddish hue that required aftertreatment to remove. But no more! Thanks to intelligent process control, our clay calciner produces material that is the same colour as OPC – without additional processes. The result is a more credible clinker substitute – at lower cost.

On top of that, thanks to intensive testing and optimization, our clay calcination technology produces a cement with close to the same performance as ordinary Portland cement in terms of binding strength and setting time.

Key Benefits

Significantly reduce the carbon intensity of cement

We mentioned at the very top of the page the fact that calcined clay emits significantly less carbon during production. And we all know that carbon reduction is an important pillar of sustainable development goals. But lowering your CO2 footprint also has real business benefits.

For example, reducing your carbon intensity insulates you against the risk of future regulatory tightening. It could also help open up access to capital from sustainability-minded financial institutions. And it demonstrates responsible practice to your local communities and stakeholders, supporting your social licence to operate.

Performance Data

Is the clay calciner for you? Check out the performance data below. Or contact us to talk to an expert.

Production Capacities

250 tpd up to 5000 tpd

Adjustable Temperature Range

650 °C up to 1000 °C

Feed Moisture

up to 30 %

How it works

Raw clay is dried and crushed, then calcined at 700-850 °C to produce a supplementary cementitious material that can replace clinker in cement.

Combustion gases from calcination process

Hot combustion air from product cooler

Reheated gases for raw material drying

Fresh Air

Gas with suspended material in flash dryer

Waste gas and recirculated gas to impact hammer mill

  1. Waste gas to stack
  2. Fan
  3. Filter
  4. Material – dry and pulverized
  5. Flash calciner
  6. Cyclone preheater
  7. Fuel feed
  8. Seperator for dried feed material
  9. Flash dryer
  10. Material – oversized particles
  11. Hot gas generator
  12. Cyclone cooler for finished product
  13. Impact hammer mill for feed preparation
  14. Material – Final product
  15. Material – Fresh feed

References

The calcination of clay is still a very young topic in the cement industry. Let’s tackle a first project together. Reach out today!

Contact

Interested in our solutions? Get in touch! We are happy to help.

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