Foul condensate preheating before stripping
In a heat-recovery arrangement, hot stripped condensate transfers heat to cooler foul condensate entering the stripping system. The streams remain separated by the welded plates. Raising feed temperature reduces the additional heat required to reach the downstream process condition, while cooling the outgoing condensate. Recovery depends on temperature levels, flow balance and the condition of the heat-transfer surfaces.
Bleach plant heat recovery
Warm bleach plant filtrate can provide heat for a colder chlorine dioxide solution. The exchanger recovers sensible heat across corrosion-resistant plates, reducing the separate heating needed for the solution. Material selection must reflect the full chemistry, temperature and concentration on both sides. Fibre content and particle size must also be matched to the available channel geometry.
Why use a block exchanger in these positions?
A compact plate pack can provide heat-transfer area where a large tubular exchanger is difficult to accommodate. Suitable channel velocities and plate geometry can help limit deposition while maintaining heat transfer. In designs with removable side panels, access to both fluid sides supports inspection and mechanical cleaning when chemical cleaning is insufficient. The value is the combination of heat recovery and maintainability under the actual mill conditions.
Managing fouling and pressure drop
High turbulence does not make an exchanger immune to plugging. Fibre agglomeration, deposits and suspended solids can restrict a passage even when initial thermal performance is good. Specify normal and upset solids loading, particle dimensions and the cleaning method. Track outlet temperatures and pressure drop during operation so that cleaning is planned around measured deterioration rather than a fixed performance assumption.
When a block design needs further evaluation
Heavy slurry, large fibres and strongly scaling streams may require a different channel geometry or exchanger technology. Do not extend a condensate application automatically to concentrated black liquor. Selection should include stream chemistry, solids behaviour, flow variation, pressure-drop allowance and access needed to remove deposits.
Frequently Asked Questions
What is a foul condensate preheater?
It is a heat exchanger that raises the temperature of foul condensate before further processing. In a recovery arrangement, hot stripped condensate provides the heat.
Can a block exchanger handle fibres?
Some duties with limited fibre carryover can be suitable. Channel spacing, fibre size, concentration and the possibility of agglomeration must be checked; suitability cannot be inferred from the industry name alone.
How does material selection affect bleach plant service?
Corrosive chemistry can differ on the two sides. Select the plates and wetted components for both streams, including concentration, temperature and possible upset conditions.