We were asked to provide our expertise and recommendation for the temperature measurement of Lithium in a rotary kiln calcinator.  We recommended the BASF’s Exactus®  high accuracy pyrometers.

• BASF’s Exactus® instruments added value by expanding the capabilities of the calcination process to include reliable and accurate non-contact temperature measurements. The energy and fuel savings realized by tightly controlling the calcination process justified the investment.  Higher throughputs and lower cycle times was achieved by controlling the furnace to the most critical variable, product bed and outlet temperature. The improvement in product quality by controlling the product temperature was yet another benefit, which also justified this project.

Technical Design Conditions

• Lithium calcination is a critical step in processing a mineral with a rapidly growing global demand.  The processing of Lithium is a key stop in manufacturing to supply to a myriad of other industries.  The controls accuracy of the calcination furnaces directly leads to product quality.  As in any furnace process, temperature is the most critical variable.
• Rotary kilns for calcination processes can be costly and difficult to operate and control.  To maximize profit, the temperature must be controlled extremely well.  Cavity and burner temperatures have traditionally been monitored for indirectly controlling the process.
• The product temperature has been inferred from the approximate air temperature in the cavity.

Technology

Exactus® optical temperature sensors provide many advantages to measuring and controlling temperatures for preheating processes.  Two unique solutions have been designed for measuring product temperatures inside the kiln for furnace controls.  The proposed measurement processes were non-contact, reliable, and durable.

Technical Description

There are two systems for measuring the calcination of product temperature in the kiln and in the chute.  Both systems use Exactus® optical sensors outfitted with optics capable of focusing on the surface of the product or on the closed-end penetrating tube.

Product Temperature

Product Bed

The system included an Exactus optical sensor outfitted with fixed optics capable of focusing on the product bed inside the calcination furnace.  The sensor was enclosed in an Industrial Purge Housing for protection from the environment.  Figure 1 shows a conceptual sketch.

Figure 1 – Product Temperature Measurement Sketch

A sight tube protrudes into the kiln environment through an existing port.  The infrared radiation from the surface of the product bed is collected by the probe optics, which are fixed to the sensor.

Chute Temperature

The system included an Exactus optical sensor outfitted with fixed optics capable of focusing on the product inside the exit chute of the furnace.  The sensor was enclosed in an Industrial Purge Housing for protection from the environment.  Figure 2 shows a conceptual sketch.

Figure 2 – Product Temperature Measurement Sketch

A sight tube protrudes into the chute through a flange port.  The infrared radiation from the surface of the product is collected by the probe optics, which are fixed to the sensor.  Peak-picking software inside the sensor microprocessor will output only the temperature of the product.

Mid Zone Temperature

The system included an Exactus® optical sensor outfitted with optics capable of focusing on the surface of an inserted closed-end tube.  Figure 3 shows a conceptual sketch.

Figure 3 – Mid Zone Temperature Measurement Sketch

A closed-ended pipe tube protrudes into the product through the wall and refractory of the kiln.  The infrared radiation from the surface of the closed-end pipe is collected by the probe optics.  The light signal is then transferred to the electronics by an optical fiber.  The reading is taken once every rotation of the kiln.  Peak-picking software in the sensor microprocessor will output only the temperature inside the well.

Software

TemperaSure® software was included with the purchase.  The software is intuitive and user-friendly.  It is easily installed onto any PC with a Microsoft® Windows® operating system.  TemperaSure® communicates to the probe through the IFD module via an RS232 or RS422 connection.

The user can easily plot temperature data or configure the probe output parameters, including averaging, peak-picking, data interpolation, and much more.

Key Advantages

The Exactus® measurement solution has several advantages over the existing technology for measuring calcination product temperatures.

• The measurement drift of the sensor is 0.1 °C per year.  This ensures an extremely stable measurement over the lifetime of the sensor.
• As a non-contact measurement, the system is not directly exposed to the harsh environment inside the furnace.  For this reason, the lifetime of the system is unmatched.
• The direct optical measurement method of the product bed temperature enables controlling the furnace to a desired product temperature.
• The response time of the optical measurement method is significantly shorter than a thermocouple.  Large changes in temperature can be measured rapidly, detecting process changes and alarm conditions quickly.