Integrating heat recovery from milk powder spray dryer exhausts in the dairy industry

Abstract

Heat recovery from milk powder spray dryer exhausts has proven challenging due to both economic and thermodynamic constraints. Integrating the dryer with the rest of the process (e.g. evaporation stages) can increase the viability of exhaust recovery. Several potential integration schemes for a milk powder plant have been investigated. Indirect heat transfer via a coupled loop between the spray dryer exhaust and various heat sinks were modeled and the practical heat recovery potential determined. Hot utility use was reduced by as much as 21% if suitable heat sinks are selected. Due to high particle loading and operating temperatures in the particle sticky regime, powder deposition in the exhaust heat exchanger is perhaps the greatest obstacle for implementing heat recovery schemes on spray dryers. Adequate cleaning systems are needed to ensure continuous dyer operation.

Effect of process parameters on energy performance of spray drying with exhaust air heat recovery for production of high value particles

“…The relative droplet velocity and the total air velocity are specified by Eqs. (12) and (13). The droplet position in the radial direction of the chamber is given by Eq.…”

“…Recently, several methods have been proposed for minimization of energy consumption in spray drying, such as combination of spray dryer with a fluid bed dryer [13] and recovery of exhaust air energy [14]. Various configurations of the system of exhaust air heat recovery have been suggested for the spray drying process, including deployment of run-around loop, cross-flow air-to-air heat exchangers, or exhaust air recycle [15].…”

Opportunities for low-grade heat recovery in the UK food processing industry

“…For example, spray dryers are used to produce powdered products such as instant coffee and tray dryers are used to dry/preserve fruit products. All dryers have an exhaust providing a low-grade gas/water vapour heat source, typically in the range of up to 160 C. Common utilisation of this heat source includes preheating of the dryer air inlet [15]. In the case of spray dryers, the exhaust gas can often be heavily fouled meaning extra consideration must be taken when designing heat recovery equipment.…”

Simulation of exhaust gas heat recovery from a spray dryer

“…The rising energy cost and growing concerns over greenhouse gas emissions urge companies to utilize the energy improving measures. Various approaches to energy conservation in spray drying have been reported in the literature including optimization of process parameters [4], utilization of exhaust air energy in a heat recovery system [5] and use of an exhaust air recirculation system [6].…”