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COOL EXPERIENCE: SUCCESSFUL CROSS-BAR® COOLER UPGRADES

Jacob Ryttergaard, K.P.Sathish Kumar

FLSmidth A/S, DK and FLSmidth Private Limited, India.

ABSTRACT The FLSmidth® Cross-Bar® cooler is well-proven in the market to handle a variety of kiln operating conditions, from small clinker production units up to the largest plants today in operation. SF Cross-Bar (SFC) cooler since introduction in 1997 has revolutionized the way in which clinker coolers were installed, operated and maintained. Most of the cement plants use coal as the primary fuel, however, the use of alternate fuels is now common and increasing. Cement producers worldwide are striving to lower their production costs by making use of alternative fuels and are using petcoke due to its lower costs. When changing to petcoke operation, special precautions to be taken to handle operational problems (due to low volatile, high sulphur and nitrogen) like reduced stability in the kiln operations, dustier clinker and risk of snow men. 1.0 Introduction: This paper will focus on the cooler-performance, flexibility observed on Cross-Bar coolers including how to change the air distribution in the cooler, how to avoid dust build up and what some good operating procedures are. Since the introduction of the Cross-Bar cooler more than 300 customers have harvested the unique benefits provided:

Consistently high thermal efficiency High reliability / availability Fast, low cost installation Low, predictable maintenance

Consistently high thermal efficiency Crossbars effectively convey, mix and shear the clinker. Wear of crossbars has no effect on thermal efficiency of cooler.

Self-adjusting mechanical flow regulators (MFRs) maintains constant airflow through air distribution plate and clinker bed, results in stable cooler operation and high thermal efficiency.

Figure-1 Stationary- grate line inlet

Figure-2 Self-adjusting MFR

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When the clinker is finer, risk of fluidizing the clinker bed is high, causing dust recirculation into kiln, where they ‘steal’ heat and bring it back to cooler that results lower cooler reliability and higher heat consumption in kiln. If fluidization problem cannot be fixed by fuel or rawmix, can be controlled by having different MFR pattern. In the recuperation zone, fluidization can be controlled by reducing the airflow and still achieve clinker temperature due to higher surface area of fine clinker, alternatively increase airflow after recuperation zone. In many other coolers in the market, a reduction in the specific air load in the hot end results in poor air distribution in grates causing heat damages. High reliability / availability ABC™ Inlet effectively eliminates snowmen and ensures a good distribution of clinker across the width of the cooler. MFR technology controls the process air and in grate air blasting grouped in zones for flexible and effective removal of snowmen and agglomerates.

A stationary, sealed grate line in FLSmidth® Cross-Bar® cooler ensures no fall through, no requirement of undergrate clinker conveying system and no gap management of grates. A static layer of clinker protects the air distribution plates against heat and wear. Crossbars are used to convey clinker. Preventing red rivers is possible by shaping the clinker bed that is achieved by reducing the stroke length of the end drives, ditches are prevented where hot dust can run. Refer Figure 6. Hammer-Crusher or Heavy-duty Roll Breaker (HRB) is positioned at the end or in the middle of the cooler for clinker crushing, The HRB is a sturdy slow moving machine with very little wear and can crush even very large lumps without stopping kiln.

Figure 3: ABC™ fixed inlet

Figure 4: With multiple drives across the width clinker bed can be shape the clinker bed to avoid hot dust rivers in the sides.

Figure 5: HRB MF Figure 6: The FLSmidth® Cross-Bar® cooler can be supplied as new or can be retrofitted into existing cooler casing.

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Important interlocks and good operation procedures: Interlocks help the operator to handle the cooler safely during upset conditions. A shallow clinker bed or fluidization of the clinker bed or airflow being blocked by Coating piece generates high grate temperature alarm. By slowing down the cooler drive, clinker bed can be increased and assess whether the airflow needs to be increased (coating pieces/agglomeration is seen) or decreased (bed is fluidized). The latest changes by FLSmidth incorporating thermocouple in each drive ensures FLSmidth Cross-bar cooler can operate with one or more drives stopped thereby reducing the risk of tripping an upset kiln due to high grate temperatures. Fast, low cost installation With the highly modular design the FLSmidth Cross-Bar cooler is designed not only for completely new coolers, but also as upgrades inside any existing cooler casing. See Figure 6. A low total installed cost is achieved by horizontal construction due to the efficient clinker transport achieved by the bars, Cross-Bar cooler and HRB modules arrive pre-assembled in containers and are quickly lifted into place and No hoppers and under grate spillage transport system is required due to the effective seal design SF Cross-Bar™ Cooler upgrade: Upgrade of an existing SF™ cooler, requires removal of all the existing cross bars and replaced with new movable cross bar. Together with some minor hydraulic system and PLC programming changes, the upgrade is quickly carried out in about 2-3 weeks, depending on the cooler size. Potential benefits are greater throughput/capacity with the same grate area, good cooler control under heavily loaded conditions, fewer cast parts for low, easy, predictable maintenance, longer lifetime of wear parts, improvements in thermal efficiency and power consumption, fast, simple installation and attractive investment level.

Low, easy and predictable maintenance The FLSmidth Cross-Bar cooler has few wear parts. The bars and U-profiles are held in place by wedges and pins. During operation, a protective layer of clinker is maintained between the grate plates and the Cross-Bars, which ensures a long lifetime for the grate plates. Experience has shown that the cooler maintenance is predictable and simple to perform. Conclusion: The modular FLSmidth® Cross-Bar® cooler reduces installation time and costs, is manufactured to a high quality standard and ensures attractive equipment delivery times. With the intelligent and flexible design it is well suited for whatever operating condition it may be put in front – including dramatic changes clinker granulometry.

Figure 7: SF™ Cross-Bar® Cooler upgrade.