May 23, 2017

Thermal check-up to prevent kiln fevers

 Cement kiln 1 - Pyroscan camera

GILDAS CHAUVEL, the Communications Manager of HGH Infrared Systems, France, underlines the significant benefits which the application of infrared line scanner and pyrometric cameras has brought to noncontact temperature monitoring of the pyro process of cement kilns.

As the search for better clinker quality, higher fuel efficiency and lower pollution is getting more and more intense, efficient supervising systems have been developed. Noncontact temperature monitoring of the pyro process of cement manufacturing is one of them. It includes Infrared line scanner for kiln shell temperature monitoring and Kiln hood pyrometric camera.

However, although all these devices have been on the market for many years, their advantages are not always well grasped mainly due to the fact they cannot be related directly to cost saving. Hence we will try to give here an objective picture of the situation.

Kiln Shell Temperature Monitoring

Line scanners have been on the market for some 30 years and although their advantages have been slow to be recognised, their use has now become widespread. With such an instrument, it is possible to detect hot spots at an early stage, evaluate in real time brick lining wear, coating thickness and even kiln axis warp.

However, for clear and reliable kiln system evaluation, it is advisable to select a high performance instrument with enhanced spatial and thermal resolution i.e. spot size on kiln must be small enough to detect fall of a single brick and the infrared detector’s signal noise must be as little as possible to monitor positively small changes in temperature. Unfortunately, there are still many systems on the market which although attractive price wise, do not meet these basic criterion.

The HGH’s kiln software

Effective products such as HGH’s kiln software meet the abovementioned basic requirements.  The HGH’s kiln software gives valuable information such as early stage hot spot detection, real time brick lining wear and coating thickness, kiln tyre slip monitoring. The main features of HGH’s kiln scanner software are:

Thermal warp calculation

This displays the kiln axis distortion due to shell uneven temperature distribution along the kiln. It enables the operator to evaluate and reduce the risks due to mechanical stress.

3 D display

HGH software enables to visualise the kiln rotating in 3 dimensions. The operator can also check the brick and coating thickness and visualise the kiln from inside thus getting a good estimate of the coating situation anywhere along and round the kiln.

Cement Kilns 1 - HGH KilnScan 3D display 1

OPC server

All data processed by HGH system can be converted and exported via an OPC connection for display on the main monitor of plant control system.

Kiln scanner system

In addition, HGH’s kiln scanner system can be adapted to the customer’s needs to suit specific plant layouts, as in the scenarios below:

  • HGH has supplied 3 kiln scanner systems in Algeria to monitor 3 long wet kilns with limited free space. With wide angle scanners (140°FOV), HGH were able to cover the total length of each kiln with one single scanner thus reducing equipment and installation cost.
  • HGH has supplied a dual scanner system to Lafarge/Italia to monitor a short dry kiln with very tight field space. By positioning the 2 scanners judiciously and merging their respective images, it was possible to eliminate the shadows generated by several posts obstructing the field of view.
  • HGH have installed a 3-scanner system to monitor a long wet kiln in England. The 145m kiln is inside a building thus limiting considerably the scanner to kiln distance. Pasting of the 3 images obtained enables display of the hot zone, i.e. half of the total kiln shell.

Cement kin 1 - HGH KilnScan 3D display-2

With reliable and complete measurement of kiln shell condition, risk of unexpected breakdowns and failures can be cut. This results in enhancing equipment lifetime, and with the process optimisation, in reducing operation costs. Compared with losses induced by unscheduled shutdowns, the return on the investment in a thermal scanner is really short.

Pyroscan camera: Kiln Firing Zone Monitoring

 For a long time now, kiln hoods have been equipped with a video camera, to view the flame, and a separate pyrometer was used to measure the clinker zone temperature. The Pyroscan is a combination of these two instruments.

The Pyroscan is a High Dynamic Range (HDR) pyrometric camera with a high image resolution of 1.2 megapixels. It has been designed to provide accurate temperature monitoring in extreme environments, with temperatures from 700 °C to 1800 °C. It provides at the same time a HD visualization of the flame pattern, and an accurate temperature measurement, for every pixel within the image, using HDR imagery processing.

 

Thanks to robust dust filter algorithms, Pyroscan is able to operate through the challenging, cluttered burning zone environment. It comes with its own dedicated software, which enables a user to remotely control the Pyroscan (extraction and insertion into the kiln) and provides the user with temperature measurements. Multiple measurement areas can be defined and alarms can be set on those areas. The software supports flame shape monitoring with user defined analyzing lines. The software also includes an OPC client option to share data on the plant network as well as a video streaming over IP. The temperature of the zones can be stored into a database and reviewed for further analysis.

Providing reliable temperature reading with minimal effect of dusty atmosphere, the Pyroscan helps operator to stabilise the burning process, to homogenize and increase the clinker quality. It brings an efficient monitoring of any changes in flame pattern and heat transfer to the product. It is a comprehensive tool for burner adjustment, particularly for firing alternative fuels, assisting the operator in adjusting burner to changing conditions, in monitoring air/fuel ratio, and in maintaining flame properties.

Beyond controlling combustion conditions, the Pyroscan can also be used for cooler monitoring to view the clinker fall, to measure the clinker temperatures on this area and to detect snowmen and red rivers.

Making headway

In conclusion, it is now obvious that non-contact temperature monitoring is making a headway into the cement manufacturing process and that users understand the need of it. The equipment available varies a lot as far performances are concerned and differences should be weighed carefully in order to get the full benefit of the system.

As maintaining high profit margin is synonymous with maintaining equipment efficiency and long-term reliability, no concessions on performance of thermal monitoring systems should apply. Thus far, HGH provides high-end instruments to cement plant staff, of course to help them in reducing risk of unexpected shutdowns, but more than that, to reduce operating costs, save energy, improve the burning process, and increase production rates.

 

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