rotary kiln temperature measurement

temperature scanning of rotary kiln shell | fluke process instruments

temperature scanning of rotary kiln shell | fluke process instruments

When analysing any cement manufacturing process, it is evident that one of the most critical steps takes place in the rotary kiln. When it comes to extending the life of this piece of equipment, as well as preventing any disastrous failures, it is imperative that operators understand the condition of the refractory material coating it. Since it is impossible to measure the inside of the kiln, looking at the outer surface is the only way to determine refractory condition. This can be accomplished with infrared technology and specially developed kiln scanning systems.

During the operation of the rotary kiln, flames can reach temperatures as high as 1900C (3452F) in order to heat raw materials to roughly 1500C (2732F). As a result, these materials become partially molten and undergo a series of physical and chemical reactions to become the primary constituent of cement. At the lower end of a kiln, the raw materials emerge as red-hot particles, called clinker. Rotary kilns are traditionally large steel pipes, several meters in diameter and up to 100 m in length (in larger facilities, however, kiln lengths of over 100 m are not uncommon). To protect the steel from intense heat, however, each kiln is lined with bricks composed of refractory material, which is typically a blend of various ceramic compounds.

These refractory bricks have been compounded specifically for cement processing applications, and while they have impressive temperature and wear-resistance characteristics, exposure to intense heat and the abrasive qualities of cement inevitably leads to material degradation. This wear causes bricks to become thinner over time, severely impacting their ability to shield the steel surface of the kiln. In order to maintain adequate levels of protection, the kiln must be stopped at some point to replace the bricks.

Additionally, if a single brick, or a small section of bricks, becomes loose and falls, the steel kiln shell will suddenly be exposed to extreme heat. If action is not taken quickly, permanent damage to the kiln may result, costing facilities large amounts of money for repair or replacement costs, as well as countless hours of lost production time. By monitoring the entire length of the kiln shell, operators can easily determine the effectiveness of the refractory material. With infrared technology, any fallen bricks can be quickly detected, and appropriate action may even be taken to prevent further damage. Plus, by combining infrared temperature measurement with a database of historical images, operators can examine temperature trends and predict when refractory materials will reach unsafe operating conditions.

As a result, operators can schedule maintenance and plan when to replace the refractory material with minimal downtime. Continuous infrared temperature monitoring also allows the operator to see the overall effect of the process on the refractory, as settings can be optimised to maintain the best possible combination of maximum throughput and extended refractory life.

Today, there are multiple temperature scanning systems for cement kilns available on the market, each with a variety of specifications and features; however, all of these systems utilise infrared scanning technology in order to gather temperature data.

To understand these scanning systems, operators need to know the basics of infrared technology. All objects emit infrared radiation; the intensity of this increases as the temperature of an object rises. Infrared temperature sensors used in industrial applications contain a detector that will generate a current when it is exposed to energy of a specific infrared wavelength. As the intensity increases, so does the current, allowing the temperature of the object to be determined.

When monitoring rotary kilns, one or more linescanners (one of the more popular scanning systems available) often work in parallel to gather data along a kilns axis. As the kiln rotates, a new line of data is generated, allowing for the entire surface of the kiln to be mapped. The data is then transferred to application-specific software, which then converts raw data into a two-dimensional thermal image of the kilns surface.

In addition to a two-dimensional image of the kiln, the software also displays each successive thermal image. This image is a false colour representation of the kilns surface temperature; it is normal for cooler areas to be highlighted by darker colours and hotter areas to be showcased as bright red or white. Normally images are displayed in real-time for the operator, allowing for any significant changes to be seen quickly.

Images are also periodically saved to a history file for later analysis, meaning operators can use this data to predict the lifetime of refractory material and schedule replacements that keep downtime to a minimum.

It is no secret that infrared technology has been widely embraced by the cement industry for more than 20 years; while all infrared rotary kiln systems offer the basic capabilities highlighted above, newer systems developed in the last decade feature some of the latest technology in the industry and offer expanded functionality to support operator needs.

Some top-tier functionalities, for example, address the concern of shadowed areas that stretch along the length of the kiln. With a wide field-of-view scanner, it can be common to have several obstructions, such as buildings, power poles, and other equipment, which essentially prevent the scanner from seeing the entire kiln shell. Several of the top systems available today, for instance the CS210 System from Fluke Process Instruments, incorporate single point sensors, also known as pyrometers, that are located in such a way that they can see the areas shadowed from the linescanner.

Up to 32 pyrometers can be installed and set up to utilise multi-drop communication, meaning only one connection is necessary for communication back to a PC. Because the software integrates data from multiple sensors into one single image, a dirty lens warning can be added. This feature compares each data point with its adjacent points and, if the difference exceeds the defined limits, operators are alerted that the sensor may be partially blocked by a dirty lens or other obstruction.

Additionally, top-tier scanning systems typically read frequencies between 3.5 and 4 . This range enables infrared linescanners to see directly through dust and moisture in order to determine the temperature of the kilns surface. In higher micron ranges, such as 8 to 14 , infrared systems tend to pick up reflections caused by dust and moisture in the air, meaning these solutions can only be used in more controlled facilities. As a result, linescanner systems are the ideal solution for cement manufacture in outdoor, rugged environments.

Other functionalities include monitoring clinker temperatures at the hot end of the process inside the kiln. In this application, an infrared sensor looks into the hot part of the kiln end through a viewing port and monitors clinker temperature. The data is displayed on the same screen as the kiln shell imagery, allowing operators to monitor both steps of the process simultaneously.

Some systems, such as the CS210 System, also offer advanced capabilities that will monitor the condition of the brick and report on refractory wear. These software features also include a module database that can store and analyse all necessary data from (at least) the last year to indicate refractory wear during use, enabling engineers to schedule refractory repairs.

While these systems are useful, it is critical that the data entered into the programme by operators is accurate. Because all installations are inherently different, wear rates will also differ; therefore, making generalised predictions on the wear rate of any given material will inevitably lead to installations where the brick simply will not last as long as the system predicts.

One additional development in improving kiln life still utilises kiln monitoring systems, but not temperature measurement. Typically, kilns are driven from one end which, due to their extensive size and mass, makes homogenous rotation extremely challenging. During this process, and particularly during speed changes, there is a tendency for some of the rotational energy to cause the kilns live-rings (or tire slips) to torque (or twist) instead of rotate.

A small amount of torque is not necessarily a problem for the live-rings, however, too much will cause damage to the fragile refractory material. In typical kiln monitoring systems, pyrometers are used to measure each live-ring rotation and trigger the display of each subsequent image of the kiln.

If multiple sensors are installed, the rotational speed of several points along the length of the kiln can be monitored and if the rotational speed varies along the length, this can be indicative that a twist is occurring, allowing engineers to make corrections before serious damage occurs.

The purpose of monitoring kiln shells with an infrared scanning system is to monitor and report on the overall condition of the refractory materials lining the kiln. Most programmes available today offer some degree of refractory management and viewing this information alongside temperature data provides the information operators need to determine how to modify kiln settings to maximise refractory life or when to schedule downtime to replace bricks.

Infrared temperature scanning systems have shown their usefulness in cement plants across the globe and modern systems are adding even more functionality, making them an essential part of any cement professionals toolkit.

Dr. Martin Budweg is a Senior Product Marketing Manager at Fluke Process Instruments, where he is responsible for designing and developing IR temperature measurement products for a variety of industrial applications. Prior to joining Fluke, he worked in the chipset technology industry as a Project and Product Manager. Dr. Budweg studied Geophysics and Astrophysics and holds a PhD in Geophysics and Seismology.

rotary kilns - williamson ir

rotary kilns - williamson ir

Industrial Rotary Kilns are primarily used in cement, lime, and iron ore processing. These furnaces use direct flame-fired heating methods to remove volatile compounds, instigate chemical reactions, and fuse powder into pellets. The material is rotated as it moves through the kiln, in order to evenly heat said material without relying on conduction.

There are six relevant temperature measurements throughout the Rotary Kiln. These six measurement areas are the Shell & Under Tyre, Product Entry, Mid-Zone, Flame Temperature, Product Discharge, and Conveyor Belt Protection.

Inaccurate heat measurements in any one of these areas can result in major equipment damage, product irregularities, production lags, and toxic fume build-up. Rotary Kilns present several temperature measurement challenges including harsh optical obstructions, varying measurement sizes, and hostile operating conditions.

Using carefully selected narrowband wavelengths to view through smoke, flames, dust, and moisture, Williamson pyrometers provide unequalled accuracy and repeatably across all crucial Rotary Kiln temperature measurements.

If the refractory material lining the Rotary Kiln overheats or is damaged in any way, then hot spots appear on the kilns outer shell. Detecting these hot spots is crucial in maintaining the kilns structural integrity, protecting human health & safety, and preventing costly downtime. Infrared pyrometers are often used to monitor shell temperature and identify hot spots before they become a problem. Rotary Kilns also have cylindrical steel castings, known as tyres, attached to the shell, which obstruct the shell monitoring system. If a hot spot forms under a tyre, then the instrument will not detect it. Consequently, a local hot spot monitor should be installed at each tyre.

Williamson short-wavelength pyrometers are optimized to identify hot spots by providing positional information while viewing a relatively large area. Pyrometers installed for local hot spot detection at each tyre, compensate for the hard to reach measurement area. This infrared system has proven to be a highly effective lower-cost alternative to line scanning systems.

Aggregate Materials are preheated using hot process gases that flow through the kiln and into the preheat zone. Aggregate material temperature at the Product Entry is used as a critical process parameter for overall heat balance throughout the Rotary Kiln. This important measurement often presents heavy dust and fluctuating air pressure. Williamsons Short-Wavelength pyrometers provide unequalled accuracy and repeatability at the Rotary Kiln Product Entry.

Peak aggregate material temperature is reached at the end of the kiln, known as product discharge. Peak temperature or peak product temperature is the primary Rotary Kiln process control parameter. Inaccurate or widely varying peak temperatures at product discharge can lead to production inefficiencies, lowered product quality & yield, fuel waste, and equipment damage. There are, however, several challenges associated with this temperature measurement area including heavy dust, flames, and sight path obstructions.These challenges combined with hostile operating conditions demand the use of Williamsons infrared technology and protective cooling system.

Williamsons Short-Wavelength (SW) and Two-Color (TC) pyrometers use carefully selected narrowband wavelength set(s) to view through severe optical obstructions, while the protective cooling jacket prevents pyrometer damage. Williamson pyrometers make continuous peak temperature measurements with unequalled accuracy and repeatability at product discharge.

Aggregate Material temperature in the middle of the Rotary Kiln provides important process efficiency and heat supply feedback. Underheated materials can compromise product quality, while overheated materials indicate fuel waste and potential equipment damage. Precise temperature control in the mid-zone improves production efficiency, increases consistent product quality, and decreases input costs by minimizing fuel waste.

Because Rotary Kilns are extremely long, it is often difficult to obtain accurate mid-zone temperature measurements from the ends of the kiln. Instead, measurements are taken from the side of the kiln using a closed-ended viewing tube. This measurement should also be made once per rotation. Williamsons Short-Wavelength (SW) pyrometers use high resolution optics and temperature-based peak hold settings to produce highly accurate mid-zone temperature measurements with each rotation.

Flame-fired processes inside the Rotary Kiln are fueled primarily by natural gas that is frequently combined with oxygen, oil, pulverized coal, or CO2 gas. Precise control over the fuel-to-air ratio within the kiln reduces fuel waste, heat loss, and dangerous nitrogen oxide accumulation. Flame or combustion temperature is a key indicator of the fuel-to-air ratio, and as a result, accurate and continuous flame temperature measurement is essential in optimizing Rotary Kiln operations. Traditional thermocouples used for this measurement must be frequently replaced, resulting in increased maintenance costs and production lags.

Williamsons Specialty-Wavelength (SP) pyrometers use a unique wavelength selection to accurately monitor Rotary Kiln Flame temperature from difficult angles and through severe interferences. While the protective cooling jacket enables the pyrometer to withstand hostile operating conditions.

As the material exits the kiln, it is pushed onto a conveyor where it finishes cooling. Some products tend to form heat retaining clumps that can easily exceed the rubber conveyor belts upper temperature limits. When this occurs, the material can cause significant equipment damage and even present thermal safety hazards.

Temperature measurement along the conveyor belt presents several challenges. The measurement area is relatively large (the entire conveyor belt,) temperature across said measurement area can vary significantly, and steam, water, and dust are common optical interferences.

Williamsons Short-Wavelength conveyor belt pyrometer monitors a large measurement area, uses a rate of change algorithm to identify hot spots regardless of bulk temperature, views through heavy obstructions without interference, and triggers an alarm when hot spots are detected.

temperature distribution within the moving bed of rotary kilns: measurement and analysis - sciencedirect

temperature distribution within the moving bed of rotary kilns: measurement and analysis - sciencedirect

Inadequacies in the temperature measurement within the moving bed have hindered a thorough understanding of the processes occurring within rotary kilns. A new measuring system, consisting of thermocouple arrays, a radio-transmitter, a radio-receiver and a computer monitor is introduced in this paper. With it, the 3D temperatures within the moving bed, as well as the temperatures of the freeboard gas and the kiln wall, can be measured and saved automatically. Experiments with sand on a co-current pilot kiln demonstrated that, in the passive layer of the moving bed, the temperatures were approximately constant in the circumferential direction. In the radial direction, however, large temperature difference was observed within the bed near the feed end of the kiln, and the difference became smaller as the bed went progressed through the kiln. This temperature measuring system can be used to obtain data over a wide range of operating conditions for use in engineering design. The obtained results may give new thoughts in theoretical modeling of heat transfer within the moving bed of rotary kilns.

kiln application solutions - thermo kinetics

kiln application solutions - thermo kinetics

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.

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.

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.

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.

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.

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.

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.

temperature measurement and control for cement & lime kilns | process sensors corp - nir and ir measurement

temperature measurement and control for cement & lime kilns | process sensors corp - nir and ir measurement

Hobbyists know a kiln as a small, high-temperature oven used to bake ceramics. But an industrial kiln is a massive oven or furnace known as a rotary kiln designed for the continuous processing of a material.

Rotary kilns are cylindrical furnaces constructed of a steel shell and a refractory lining that rotates along the long axis. The axis of rotation is tilted so that gravity continuously moves a product like limestone from the high end, down the furnace toward a burner at the low end where the product is discharged into the clinker cooler. Rotary kilns are used in a variety of processes, though primarily in the production of lime, dolomite and cement.

Non-contact infrared (IR) pyrometers have been used in cement plants for over forty years. Prior to that, contact thermocouples were the only technology available and required frequent replacement due to mechanical damage or corrosion caused by process gases.

Temperature monitoring at a number of kiln locations is essential to ensure product quality, optimize throughput, minimize emissions, and to prevent damage to the kiln shell and material handling conveyors. Critical monitoring areas are process material preheat, mid-kiln, burning zone, kiln shell and clinker cooler.

To improve efficiency and reduce emissions, exhaust gases from the kiln are used to preheat the rawmix feed material before it entersthe kiln. Inadequate preheating can signal problems in the heat exchanger that will increase fuel consumption costs. Process Sensors Corporation (PSC) 1-color pyrometers can be installed to sight on free-falling preheat material or preheater feed tower wall to alert when temperature falls below a preset level. 2-color sensor models are effective for measuring feed material that is hotter than the vertical tower walls as they can disregard colder temperatures often present in their sight path.

Most modern kilns have a 4 to 5 inch inside diameter by 4 to 5 foot long target tube in the sidewall of the kiln where monitoring mid-kiln temperature is critical to ensure kiln integrity. A PSC Non-Contact Infrared (IR) Pyrometer is recommended for measurement reading during each rotation of the kiln. A variety of fixed focus optics are available where users may choose to integrate laser-aiming light to determine exact alignment to the bottom of the target tube.

The burning zone is the last stage before the material exits the kiln. A single burner fires toward the approaching material, and precise temperature measurement is important to control the firing of the burner. A PSC 2-color pyrometer is effective for monitoring the burner zone as they compensate for dust that can obscure the sight path. Alternatively, a PSC Thermal Imaging Camera is recommended to understand the thermal profile inside of the kiln. Non-Contact Infrared (IR) Pyrometers should not be sighted through the flame, but along the axis or below the flame.

Uneven heating of the kiln shell distorts the metal skin and the cylinder can become banana shaped, damaging the bearings, causing a process shutdown. A PSC thermal imaging camera detects uneven kiln shell heating with real time thermal images so damage and unwanted shutdowns can be avoided. The thermal imaging camera can also be switched into line-scan mode, enabling the customer to easily and quickly replace an old line scanner camera.

Hot process material exiting the kiln (clinker) is conveyed under cooling water sprays. Failure to cool the clinker thoroughly can result in fires at inaccessible locations along the conveyor, or in ball mills. Installation of PSC pyrometers and/or thermal imaging cameras can detect an inadequately cooled clinker to protect against fire.

The PSC-42 Series of simple, 2-wire loop powered sensors offer on-board emissivity adjustment, multiple wavelength options and wide temperature ranges. Ideal for industrial and OEM machine building applications with wide temperature range of -40C to 2500C.

The PSC-40 Series is a two-wired, loop-powered sensor which provides accurate temperature measurement from -40 to 2500C. Also available in fiber optic. Industrial applications including induction heating, steel making, glass, kilns, food, dryers, ovens, furnaces, medical apparatus and R&D.

The Process Sensors Surveyor camera series offers a comprehensive range of imaging and line scanning camera systems to continuously monitor and control industrial processes. Measures temperatures starting from -20 to 1800C

kiln burning zone temperature measurement - accurate sensors technologies

kiln burning zone temperature measurement - accurate sensors technologies

Pyroprocessing is a process in which materials are subjected to high temperatures (typically over 800 C) in order to bring about a chemical or physical change. It consists of three stages: Preheater, Kiln & Cooler.

Preheaters are used in industrial dry kiln cement production plants to heat the raw mix and drive off carbon dioxide and water before it is fed into the kiln. Temperature typically used from 100C to 300C

The Kiln is the heart of the plant what an entire cement plant is dimensioned around, and where most of the final chemical reactions take place. The kilns play a key role in ensuring optimal quality clinker. The rotary kiln consists of a tube made from a mild steel plate and slowly rotates on its axis. Rawmix is fed in at the upper end, and the rotation of the kiln causes it to gradually move downhill to the other end of the kiln. Kiln size & Dia is dependent on the capacity of the production of the plant.

There are many different types of refractory brick and they have to withstand not only the high temperatures in the kiln but reactions with the meal and gases in the kiln, abrasion and mechanical stresses induced by deformation of the kiln shell as it rotates. The range of kiln temperature is between 700C to 1800C.

The burning zones are in a more aggressive environment and So, different parts of the kiln are lined with different types of bricks in the refractory. Severe changes in the temperature may damage the refractory lining. The cost of refractories is a major expense in operating a cement plant, kiln stoppages are avoided as far as possible.

AST A450C Two color pyrometer is most recommended for cement industry environments like dusty which measure accurate temperature of the KILN BURNING ZONE. 2 color pyrometers overcome the obstacles like dust & fumes and focus on the target for reading.

The Pyrometer measures the temperature of an object by calculating the ratio of the energies at two different wavelength bands. A wide band detector with spectral range from 0.7 to 1.15 m is used in A450C+

A 450C+ has real time color video for data monitoring in a burning zone measuring temperature and emissivity is displayed on the television screen. Pyrometer offers RS 485 interface, Analog output 0..20mA & 4..20 mA

The Clinker Cooler is used to cool the clinker. After cement is dried by being put through a rotary kiln and converted to a clinker, it needs to be cooled. The rate of cooling tunnels are used to reduce the temperature of the clinker from over 1250C to a workable 100C. These tunnels typically use forced draft fans to push the cooled air through the clinker. It is essential to monitor the clinker for rogue hot inclusions before it reaches the conveyor belt and causes damage.

EL50 is an economic digital IR Pyrometer from E series with extended sensing head in 4 wire technology for non-contact temperature measurement between 0C to 800C. The pyrometer comes with wide angle optics to cover more area, fast response time within milliseconds and PC software for remote parameterization.

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