FLSmidth’s Kiln Calculation Program celebrates 50 years

October 9, 2017 Keld Hjortshøj

Since 1967, continuous updates and improvements have ensured that FLSmidth’s kiln calculation program has continued to be a valuable tool for designing and maintaining kilns.

The heart of any cement plant, the rotary kiln, has always demanded a high level of expertise. Specifically, this requires complex mechanical calculations to ensure a mechanically sound and reliable kiln that can produce the highest quality clinker over a long lifetime. These calculations consist of thousands of engineering formulas which provide the necessary output for experienced kiln engineers to assess whether all parameters are within acceptable design limits. If done manually, the process may take several weeks, if not more.

The kiln calculation program began to take shape in the 1960s, when promising young mechanical engineer Knud T Andersen began sketching out ideas for automating many of the calculations required when designing or inspecting a kiln. Recognising that manual calculations were neither efficient or future-focussed, he discussed his ideas with the manager of the engineering department, Halvor Meedom, and together they developed the first iterations of the FLSmidth Kiln Calculation Program.

In doing so, they created probably the oldest engineering computer program in FLSmidth – which has now been used for 50 years – and has revolutionised the mechanical calculation of FLSmidth kilns. Today, the program is used to design new rotary kilns and mechanically diagnose and analyse FLSmidth kilns in operation as well as those produced by other manufacturers.

Mechanical foundation
Prior to the program’s creation, kiln design was a lengthy and time-consuming project, involving a huge amount of manual calculations. FLSmidth’s Department Manager of Pyro, Keld Hjortshøj, describes the kiln calculation program as the mechanical foundation for kiln engineers:

“Our program is the ‘father’ of approximately 1000-1500 kilns throughout the world and is also used by our customer service department to assess the mechanical condition of older rotary kilns.  Our continual investment in the program will ensure it remains relevant and ready for future technological developments in kilns.” - Keld Hjortshøj, Department Manager of Pyro Technology at FLSmidth

A lasting theoretical basis
Fifty years ago, rotary cement kilns were likely to have five to seven supports, a diameter of between four and six metres, and a production capacity of no more than 2000 tons per day. Today, the picture is quite different. As technology has developed, kilns have become shorter with only two or three supports, but with significantly increased production due to preheaters and calciners. The kiln calculation program has had to be flexible and robust enough to keep up with these developments.

The program involves several modules that derive the loads on the kiln shell and the kiln supports as a static indetermine beam. It can calculate kilns with up to eight supports and calculates the ovality of the kiln shell and live rings. This is done using:

  • Newton’s rules
  • Clapeyron's equation
  • Kiln ovality theory

Continual development
Still following these principles, the kiln calculation program has been continually developed and improved throughout the past 50 years to meet current needs. Its theoretical foundation has proven to be robust enough to handle vastly different rotary kilns.

In 1967, prior to the invention of the PC, punch cards were used to input the program with the output printed on paper.

Since its inception, the program has been continually reviewed by FLSmidth engineers ensuring its relevancy with technological advances. In 1988, Mechanical Engineer Henning Jacobsen was made responsible for keeping the kiln program up to date. He still works with it today:

“In 2000, we decided to move the kiln calculation program onto a new platform based on a Microsoft Excel interface with Visual Basic calculations. This meant we could make great improvements to the user interface, which was an important step in its development. Apart from this, however, the fundamental mathematics of the program has not changed over the years.” - Henning Jacobsen, Mechanical Engineer, Pyro Technology, FLSmidth

Continuous development of the program includes modifying the dimension formulas and adjusting data based on experience and input from kiln engineers in the field. The program is a valuable tool in designing new kilns, as well as reviewing older kilns and their components, such as kiln supports and kiln drive station.

Henning is now working on a manual that will allow other programmers to continue the maintenance of the program to ensure the program remains as a solid mechanical foundation for FLSmidth’s kiln engineers for at least another 50 years.

Keld Hjortshøj

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