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CFM - Coal Flow Measurement
Pulverized Coal Injection (PCI) systems should assure small line-to-line deviations in order to maintain a ‘healthy furnace’. Reality is often different; consequently optimal injection rates are not reached. The CFM flow meters are the first step towards optimal injection rates: measure the flow, control it, increase it to the optimum.
Application 
Technology
Technical data
Publications
Application
Coal injection (PCI) into the blast furnace meets the need for cost reducing and minimizing the environmental impact of steel production.
While pursuing the benefits of replacing expensive coke by cheaper injection coal the blast furnace stability and overall productivity must be sustained. The limitation of coal injection is the necessity of a complete combustion of the coal particles. Unburned char remains are the result of overloading individual tuyeres beyond the ideal calculated replacement ratio of coke by injected coal.
PCI into the raceway of a blast furnace
Only by strictly avoiding unburned char particles a high permeability and a reduction of gas consumption can be achieved. This is mandatory for the blast furnace stability and productivity.
Tests at existing PCI installations using static distribution show large deviations between individual lines. Overloading individual tuyeres with negative effects on the permeability is unavoidable in this case.
Therefore, a reliable uniform distribution of injected coal is the top priority.
A well designed pneumatic layout of the PCI installation is the precondition but due to ever changing pneumatic conditions during operation only an individual closed loop control for each tuyere makes it possible to achieve a truly uniform distribution.
Controlled injection with CFM
The CFM is the flow meter of choice in this application – the reliable, self recalibrating measurement equipment fulfills all requirements for perfect control of injection in all different plant layouts.
Integration of CFM control in different plant layouts
Today over 1000 CFM units are in operation. Examples of customer results:
- Reduction of deviations from over +/-20 % to less than 2 %
- Increased PCI rate by 55 kg per THM (ton of hot metal)
Technology
For the CFM, a capacitive measuring method is being used, taking advantage of the different dielectric characteristics of coal powder (εR) and of the conveying gas (ε0).
Each CFM sensor consists of two different sets of electrodes. The first set measures capacitively the powder coal concentration present in the injection line. The second set of electrodes is needed to measure the velocity of the particles, using a
capacitive-correlative method. A microprocessor, integrated in each CFM device, calculates the actual flow rate from the product of these two values, the geometric property of the conveyor line and the material dependent calibration factors.
Some features making the sensor unique:
- Independence of the coal distribution in the conveying pipe through the helix-design of the electrodes
- Immunity against pressure peaks by using non-ceramic tubes
- Easy parameter setting and documentation via a bus communication between all sensors
Technical data
Measuring tube
- Fiber reinforced Epoxy or ceramics
- Pipe diameter DN15 to DN 150
Electronics
- Self contained inside flow meter
- No further installation of electronics in electrical room necessary
- Optional integrated PID controller for direct valve control
Mechanical construction
- Steel pressure body
- Cast aluminum electronics case
- Cable glands or system connectors for electrical wiring
Ambient conditions
- Suitable for outside installation (IP67 rating)
- Temperature -20 °C – +40 °C (-4 °F – 104 °F)
- Extended temperature range up to +70 °C (158 °F) available
Media conditions
- Pressure-less to more than 50 bar (725 psi)
- Media temperature up to 90 °C (194 °F)
- Extended temperature range up to 450 °C (842 °F) available
Parameterization
- Centralized via CAN-Bus
- Automatic recalibration option
Flexible signal inputs/outputs
- Digital-Link protocol converter for various fieldbus standards like Profibus, Profinet, Melsec
- 4-20mA current loops for analog interfacing
- Optional interface for direct valve control
Power supply
- 24V DC +/- 20%, max. 20 W
Installation options
- Flanges according to several standards (DIN/EN, ASME, JIS) or customer specific
Conventional wiring or tailored EasyWiring system with system connectors
Classification
- ATEX Ex II 3D EEx T5 / exproof ATEX Ex II 2G EEx d IIC T6 (EC/94/9)
- Pressure equipment directive (97/23/EC) or ASME Code
Publications
-
Weiser, R.; Braune, I.; Matthes, P.: „Control Blast Furnace Pulverized Coal Injection to Increase PCI Rates”. AISTEC Conference, 2006, Cleveland, Ohio, USA Download