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Metallic phosphoric acid heaters in place of graphite

block heaters

SYMPHOS 2013 in AGADIR Morocco

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Summary

Requested heater in 54% Phosphoric acid concentration

Actual Situation SANICRO 28 Metallic Heater Graphite blocks heaters replaced by metallic

heaters Typical operating conditions Financial cost Conclusion

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Requested heater in 54% phosphoric acid concentration

Heater

VacuumEvaporator

Steam

P2O5

28-30%

P2O5 54%

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Actual Situation

Old units use graphite block heaters and it has shown that blocks :

• are easily plugged• break, crack• are involved in production shutdown• have an average lifetime of 2-3 years• are involved in the very high and unreasonable maintenance costs

Breaks

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Actual Situation

So, the more recent units have evolved, and now are using graphite tubular heaters. Unfortunately, these heaters cannot solve all the block heaters problems :Graphite tubes stay very brittle and remain under the threat of a tube which can break , stopping the production.

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Actual Situation

Conclusion :Graphite heaters, despite their evolution, are far away to give a full satisfaction.If units are more secure with tubular graphite heaters, it stay under the threat of a tube which can break, stopping the production.And, older units using graphite block heaters stay extremely expensive in terms of maintenance costs.

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Why tubular graphite heaters haven’t replace graphite block heaters ?

- Because different design parameters of graphite block heaters cannot be transferred to the tubular graphite heaters, important design characteristics wouldn’t be respected.

- The change cannot be done without heavy plant modifications.

- Without these heavy modifications, the power of a tubular graphite heater which can be put in place of a block heater will be much more lower.

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However, there is another solution now well known and improved in a lot of Phosphoric acid plant all over the world.

The SANICRO 28 metallic heater

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SANICRO 28 Metallic Heaters

The SANICRO 28 stainless steel has been developed for phosphoric acid services. Metallic heaters in SANICRO 28 are especially adapted for 54% phosphoric acid concentration.

There is a lot of advantages :• Excellent robustness of heaters

Tubes cannot break• 10 years service life minimum• Extremely low maintenance costs• No production shutdown• All advantages of a metallic solution• …

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SANICRO 28 Metallic Heaters

But, there is another advantage,

If you haven’t forgotten the slide 7, you remember that the old units are using graphite block heaters which are extremely expensive in maintenance costs and which cannot be replaced by tubular graphite heaters.A large range of tube diameters can be used in the metallic heaters and with the correct parameters taken from our know how, we can design a metallic heater in the place of a graphite heater.

METALLIC TUBULAR HEATERS CAN REPLACE GRAPHITE BLOCK HEATERS WITHOUT HEAVY PLANT MODIFICATION.

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Graphite block heaters replaced by metallic heaters

• The same heating power• The same process pipes• The same recirculating pump• The same support structure

Only the steam piping needs to be adapted

With the SANICRO 28 metallic heaters, you will keep in your plant :

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Typical operating conditions

Graphite heaters Metallic heaters

P2O5 pressure 2 to 3 bara 2 to 3 baraP2O5 temperatures 76 to 84°C 76 to 84°CSteam pressure 2,5 to 5 bara 2 to 2,5 baraSteam temperatures 130 to 150°C 120 to 128°C

Note : the lower steam temperature for the metallic solution is easily compensated by an extra exchange surface.

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Typical operating conditions

Regular cycles of cleaning for metallic heaters are the same than graphite block heaters.

- Make a cleaning as often as possible by recirculation of industrial water or sea water.

- 3 or 4 times per year, a mechanical and high pressure cleaning of the bundle.The goal of the cleaning is to remove deposit to keep the thermal exchange and avoid the corrosion under deposit.

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Financial cost

The cost of a metallic heater is approximately the same than the cost of a graphite heater. But, The lifetime of the metallic heater is much more longer than the lifetime of the graphite heater.The maintenance costs of the metallic heater are insignificant.The maintenance costs of the graphite blocks are unreasonable.The purchase budget of the metallic heater can easily be taken on the budget of the block spare parts.

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Conclusion

SANICRO 28 metallic heaters are the solution to :

-Stop the production shutdown of the phosphoric plants.-Decrease the maintenance costs of the phosphoric plants.-Increase the production and the profit of the phosphoric plants.