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Home , Hot blast, Tuyere

STOVE DOME AND MAIN

The quality and composition of produced in the blast furnace is directly related to the hearth temperature. This, in turn, is dependent on the temperature of the hot blast delivered from the blast furnace stoves. To maximise the efficiency of the stoves, they are operated at high temperatures, close to the safe working limit of the refractories. This makes it critical to carefully monitor the stove temperature. BLAST FURNACES AND STOVES

Blast furnaces heat to a period of accumulation, flow is produce the iron required as a reversed, and the hot stove is used raw material for -making. For to preheat the incoming air. efficient operation, the air is heated Stoves are alternated, storing heat before being sent into the furnace. and dissipating heat on a regular This ‘hot blast’ technique – flow reversal plan. Many blast preheating air blown into the furnaces are serviced by three or blast furnace – dates back to the more stoves, so that while two are , and was being heated, the air blast can pass developed to permit higher through the regenerative chamber furnace temperatures, increasing of the third stove on its way to the the furnace capacity. furnace. Preheating the air intensifies and Accurate monitoring of the stove accelerates the burning of the temperature supports efficient . A blast furnace fed with operation – higher temperatures air preheated to between 900- are more efficient and, by reducing 1250oC (1652-2282oF) can generate coke consumption, are more cost- temperatures of about effective. However, temperatures 1650oC (3002oF), which significantly that exceed the working limit of reduces the consumption of coke the refractory will damage the per ton of iron produced. brickwork and shorten the lifespan of the stove. A typical hot blast stove consists of a vertical steel cylinder lined with This important measurement is firebrick, with the interior divided ideally taken by measuring into two chambers. The combustion the temperature at the dome chamber burns gases from the blast underside, but can also be effective furnace and from other sources if taken from the brick checkerwork such as the coking plant. The In addition, continuous monitoring regenerative chamber is filled with of the hot blast main provides a checkerwork of refractory brick, the data required to optimise the heated by the burned gas. efficiency of the blast furnace The stoves act to store heat from operation. the blast furnace waste gases. After

02 Blast furnace stove dome and hot blast main application note USING THERMOCOUPLES IN FURNACE MEASUREMENTS TRADITIONALLY, IMMERSION THERMOCOUPLES WERE USED TO MEASURE TEMPERATURES IN THIS APPLICATION.

However, the harsh environment caused by high temperatures and high pressures significantly reduces the lifetime of these thermocouples, due to contamination and migration of the tip materials The metal sheaths used to protect conventional thermocouples are not viable above 1200 oC (2192 oF). Alternative sheaths are easily broken or damaged by the expansion and contraction of the ceramic brickwork during the heating cycle. In addition, sudden pressure relief (or ‘snorting’) can cause a drop in the temperature reading of between 20-30 oC for about 30 seconds. This makes the thermocouple signal unsuitable for use in automatic stove reversal control systems.

The Blast Furnace

RECOMMENDED SPOT R100 FO with Stove Dome Assembly RECOMMENDED SPOT R100 FO

RECOMMENDED Hot Blast Main SPOT R100 or NIR CAMERA

Iron Stream

Waste gas produced by the blast furnace is enriched with natural gas or coke oven gas and used as in other areas of the steel works.

WWW.AMETEK-LAND.COM 03 NON-CONTACT MEASUREMENT SYSTEMS

CORRECTLY INSTALLED, AN INFRARED PYROMETER SYSTEM WILL PROVIDE ACCURATE TEMPERATURE MEASUREMENTS FOR THIS APPLICATION WHILE OVERCOMING MANY OF THE PROBLEMS ENCOUNTERED SPOT FIBRE-OPTIC BY THERMOCOUPLES. PYROMETER

A short-wavelength pyrometer is Depending on the mounting position, Any significant deviation between this required for this measurement, as this specific components may be required. pyrometer and either of the two in will ‘see’ through the gases produced For example, if alignment is important, continuous use would indicate a need by combustion. it may be necessary to use bellows or to inspect the system. alternative methods to provide sealing The non-contact infrared It is also important to fit an isolation and permit sighting adjustments. measurement technique ensures valve, allowing access to the system maintenance-free operation for A gas-purged window assembly is components if this inspection many years. However, the pyrometer essential to provide optical sighting becomes necessary, and for electronics can be affected by the for the pyrometer and to protect it maintenance or replacement of parts. harsh environment, so correct from the high stove pressures. installation is critical to ensure For most widely used stove designs, effective operation. two measuring systems are mandatory A specialised mounting arrangement to meet operating specifications. will provide isolation and protection However, a third system may also A blast furnace may run from the heat and pressures. be installed to ‘police’ the other two. continuously for up to ten years with only occasional short stops for planned maintenance.

04 Blast furnace stove dome and hot blast main application note AMETEK LAND’S STOVE DOME SOLUTION AMETEK Land recommends the SPOT measurement location – or to sight Some blast furnaces monitor R100 FO fibre-optic infrared pyrometer down onto the checkerwork. temperatures looking along the axis of for this application, installed as part of a (the nozzle through which air The SPOT R100 has a very rapid the specifically developed Stove Dome is blown). The AMETEK Land SPOT R100 millisecond response speed and, unlike system. fibre optic pyrometer is perfect for this a thermocouple, operates effectively for measurement. For the hot blast main, the SPOT many years. R100 FO views a hollowed refractory In addition, the temperature of the iron As a ratio pyrometer it uses two brick in the main that attains the gas detectors, with one at 1 µm and the that is tapped is an indication of desired temperature rapidly. other at 1.2 µm. These wavelengths are quality and blast furnace conditions. In the furnace stove, it can be installed short enough to ignore interference Continuous non-contact temperature to either look up at the stove dome from combustion gases and accurately measurement can also be achieved – generally the most desirable target the refractory brick. using the SPOT R100 pyrometer.

RECOMMENDED SPOT R100 FO STOVE DOME ASSEMBLY

Stove refractory surface temperature measurement is critical for long life and efficiency AMETEK Land SPOT R100 Fibre-optic and Stove Dome assembly are recommended

RECOMMENDED SPOT R100 FO with Stove Dome Assembly

for NON-cONtact temperATure measurement SPOT R100 PYROMETER

Single-spot, non-contact infrared pyrometers, optimised for a wide span of temperature ranges and process requirements. FIXED SPOT PYROMETERS

WWW.AMETEK-LAND.COM 05 THE SPOT PYROMETER An infrared ratio pyrometer with fibre- pyrometer range offers a flexible operator, contained within a single optic attachment, the SPOT R100 FO selection designed to match specific device. Signal processing is performed supports optimisation of the blast process challenges. within the sensor, so no separate device stove process, helping to protect is needed. It is available in a variety of operating the stove interior from overly high wavelengths and temperature ranges By integrating sophisticated automatic temperatures. for different process requirements, beam alignment technologies that The fibre-optic design provides the with monochromatic and ratio precisely focus the advanced infrared accurate, reliable readings required versions, plus hybrid models that optics, the SPOT range delivers for efficient stove operation, while switch detectors according to the accurate stable measurements quickly, ensuring the sensitive electronics of temperature levels. reducing maintenance time and the pyrometer are located away from enabling faster process adjustments. Ethernet, Modbus TCP, analogue hostile conditions. outputs, alarm outputs and image Easy to install and position, the SPOT streaming are all available to the

FEATURES BENEFITS

Self-contained single-sensor solution Faster, more accurate measurements Range of digital and analogue communications Quick optimum focus using LED target sight Local and remote motorised focus control Fibre-optic version ideal for inaccessible locations Easy plug-and-play installation On-board processing - separate processor not required Powerful software support Long-life, scratch resistant sapphire protection window

SPOT PYROMETER WITH FIBRE-OPTIC ATTACHMENT

SPOT PYROMETER

06 Blast furnace stove dome and hot blast main application note THE STOVE DOME SYSTEM AMETEK Land’s Stove Dome system is no need for the regular replacement combustion products and ensure an application-specific solution which of expensive equipment, or to use process efficiency. uses advanced infrared radiation multiple instruments to counter the By measuring the refractory surface pyrometer technology to monitor high loss rate. temperature rather than the gases, refractory temperatures around the the Stove Dome system avoids the stove dome or hot blast main. Utilising a highly accurate, high- pressure-rated sighting assembly, problems caused by pressure relief that Delivering an innovative non-contact the pyrometer is installed on top or affect thermocouples. This makes the measurement, the Stove Dome system at the side of the stove. This allows it system far more suited for automatic avoids the maintenance problems and to focus onto the internal refractory change-over control. slow response associated with using checker or bridge brickwork, using a thermocouples. This ensures there is selected short wavelength to ignore

FEATURES BENEFITS

Application-specific mounting Accurate, rapid-response measurements Non-contact measurement solution Long service life; lowers plant operating costs Shut-off valve for easy removal Minimal maintenance requirements Short-wavelength infrared measurement Measurement unaffected by combustion gases

STOVE DOME ASSEMBLY AUTO SHUT-OFF VALVE ACTUATOR TWIN SYSTEM FOR HARSH ENVIRONMENTS

WWW.AMETEK-LAND.COM 07 SUMMARY

Accurate measurement of the stove infrared pyrometer system is AMETEK Land offers an application- refractory surface temperature recommended, using short- specific solution for the stove is critical to ensure the efficient wavelength detectors. dome, designed to overcome operation of the stove without the challenges of temperature The blast furnace environment is causing damage to the ceramics in measurement in this location. In hostile to standard pyrometers, the regeneration section. addition, this system can also be so a specialised installation, using utilised to monitor the hot blast To overcome the difficulties caused fibre-optics, is ideal to protect main, providing a comprehensive by combustion gases, and to the instrument from damage solution for this critical stage of the significantly reduce maintenance and deliver reliable, continuous steel-making process. requirements, a non-contact monitoring.

AMETEK LAND PRODUCT SOLUTIONS FOR THE BLAST FURNACE:

SPOT Pyrometers Blast Furnace Stove Fully-featured, high-performance Dome System pyrometers for fixed, non-contact Application-specific infrared SPOT infrared spot temperature pyrometer system designed to HIGH PRECISION PYROMETERS

A PRODUCT OF THE SYSTEM 5 FAMILY measurements and a range of accurately monitor refractory WWW.SPOTTHERMOMETER.COM

process requirements. temperatures around the stove i 50 to 1800 °C / 122 to 3272 °F dome or hot blast main.

FIXED SPOT FIXED SPOT QUALITY CUSTOMER SOLUTIONS PYROMETERS PYROMETERS

DOWNLOAD THE BROCHURE AT: WWW.AMETEK-LAND.COM

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