- Smooth and efficient heat transfer at low shear for sensitive products
- Low investment costs compared to dynamic heat exchangers
- Lower energy consumption compared to dynamic heat exchangers
- Dramatic reduction of equipment size through static mixer inserts
- Narrow residence time distribution
- Design can be adjusted to pressure drop requirements of existing plants
- Heating and cooling of polymer and polymer solutions
- Mixing and removal of exothermic heat during reaction
- Melt viscosity adjustment by temperature variation to obtain optimal process conditions
- Cooling polymer melts before granulation to raise the viscosity
- Cooling polymer melts before filling plants to avoid thermal damage to packaging
- Cooling polyester melts between the reactor and the fiber spinning unit
- Heating polymer solutions prior to devolatilization
Types of heat exchangers
Sulzer has extensive experience in designing and fabricating various types of mixer-heat exchangers for different applications. The SMXL mixer-heat exchanger typically divides the main product stream into sub-streams flowing through parallel tubes (multi-tube heat exchanger principle), whereas the product in SMR type heat exchangers is not split, but flows on the shell side of the apparatus, which makes this device ideal for reactions where residence time is a key factor.
SMXL static mixer-heat exchanger
The product conveying inner-tubes are filled with static mixing elements, creating a radial mixing effect. The result is a considerably increased heat transfer and a narrow residence time distribution, making it possible to achieve a short residence time in the heat exchanger. A continuous renewal of the thermal boundary layer on the piping wall prevents thermal damage of heat sensitive products.
SMR and SMR plus mixer-heat exchanger
The SMR type equipment is not only suitable for heat transfer applications, but also for reactions where simultaneous mixing and heat removal is of great importance. The static mixing elements are made from tube bundles with a geometry which creates radial mixing of the product flowing on the shell side. Within the tubes of each bundle, heat transfer medium is circulated at high throughput. The SMR can be designed as a cross, co- or counterflow heat exchanger. Due to the radial mixing over the entire cross-section of the apparatus shell, the SMR is ideally suited for reactions where good mixing, efficient heat transfer and narrow residence time distribution are important. In addition, using an SMR type cooler prevents maldistribution, which frequently occurs with multi-tube heat exchangers.
Cooling of polymer melts and solutions
Cooling a polymer melt or solution is a difficult task, as the viscosity of the product between inlet and outlet increases. In some cases, this effect may be very pronounced and can lead to maldistribution of the polymer flow between the tubes of a simple multi-tube heat exchanger. Sulzer has extensive know-how in predicting such effects by calculation and, by choosing the most appropriate equipment design, is able to find solutions for even the most difficult cooling tasks.
Cooling tasks typically comprise:
- Cooling of silicone oil and silicone rubber prior to filling
- Cooling of hot melt, adhesive solutions and thermoplastic melts
- Cooling of polyester melt prior to fiber spinning
- Adjusting the viscosity prior to a downstream process step
Heating of polymer solutions
In most cases, polymer solutions are very sensitive to excessive heating. Accordingly, heating of such a product should be carried out within a short time and with a narrow residence time distribution, in order to maintain good product quality. Furthermore, hot spots, or overheated surfaces due to film built-up within the equipment, must be avoided to prevent damaging the product.
Sulzer's SMXL heat exchangers are optimally suited to fulfill this requirement. We can design these types of heat exchangers for mixtures of 2 or more phases, which may occur upon pre-heating in combination with large pressure drops within the equipment, for example, prior to entry in a devolatilization vessel.