Energy saving potential of emerging technologies in milk powder production

Background: The food industry has a large potential for energy reduction which, with an eye on the future, has to be exploited. Milk powder production consists of many thermal processes and is responsible for 15% of the total energy use in the dairy industry. A reduction in energy consumption can be realized by using innovative technologies instead of realizing incremental process modifications. Scope and approach: In this work first the current practice in milk powder production is described and analyzed with respect to energy consumption. Then the potential of emerging technologies for milk processing like membrane distillation, monodisperse-droplet drying, air dehumidification, radio frequency heating, combined with renewable energy sources as solar thermal systems, are investigated. Finally the energy consumption of the emerging technologies is compared to that of the current technologies, new production chains are proposed and evaluated with respect to their total energy consumption. Key findings and conclusions: In this review we show that the combination of emerging technologies is able to reduce the operational energy consumption for milk powder production up to 60%, i.e. from 10 MJ/kg powder in current production to 4-5 MJ/kg powder. The implementation of these technologies and development of new production chains is essential to meet the future demand on energy efficient processing

Energy saving potential of emerging technologies in milk powder production

Background: The food industry has a large potential for energy reduction which, with an eye on the future, has to be exploited. Milk powder production consists of many thermal processes and is responsible for 15% of the total energy use in the dairy industry. A reduction in energy consumption can be realized by using innovative technologies instead of realizing incremental process modifications. Scope and approach: In this work first the current practice in milk powder production is described and analyzed with respect to energy consumption. Then the potential of emerging technologies for milk processing like membrane distillation, monodisperse-droplet drying, air dehumidification, radio frequency heating, combined with renewable energy sources as solar thermal systems, are investigated. Finally the energy consumption of the emerging technologies is compared to that of the current technologies, new production chains are proposed and evaluated with respect to their total energy consumption. Key findings and conclusions: In this review we show that the combination of emerging technologies is able to reduce the operational energy consumption for milk powder production up to 60%, i.e. from 10 MJ/kg powder in current production to 4-5 MJ/kg powder. The implementation of these technologies and development of new production chains is essential to meet the future demand on energy efficient processing

Energy efficient powder production by closed-loop spray drying

Closed-loop dryers are able to reduce the energy consumption in milk powder production up to 60% compared to current practice. Application of monodisperse droplet atomizers eliminates the presence of fines in the exhaust air of spray dryers. It allows the recirculation of the exhaust air over the dryer and the recovery of latent heat. For recirculation, the air is dehumidified with a membrane contactor using saturated salt solutions, or a zeolite system. During dehumidification heat is released while energy is needed for regeneration of the adsorber. By heat integration of the adsorber-regenerator system with the dryer or a related process, a significant improvement of energy efficiency can be achieved. In this work we present four configurations for closed-loop spray drying. For each system simultaneous optimization of the operational conditions and the heat exchanger network is applied for optimal energy recovery. The results for milk powder production showed that, compared to the current practice, simultaneous optimization for closed-loop dryer system results in a reduction of energy consumption from 38% up to 62%

Closed-loop spray drying solutions for energy efficient powder production

This paper introduces a closed-loop dryer system to reduce the energy consumption for milk powder production. The system is based on a monodisperse droplet atomizer which reduces the amount of fines in the exhaust air, and allows dehumidification and recirculation of the air over the dryer. In this way the latent and sensible heat from the dryer exhaust are recovered. Two adsorbent systems for dehumidification are discussed; a membrane contactor with a liquid desiccant, and a zeolite sorption wheel. Four configurations for closed-loop spray drying are simulated and optimized. By heat integration of the adsorber-regenerator system with the dryer and preceding concentration step, the energy consumption is significantly reduced to 4.9 MJ heat per kg milk powder. The final heat integration solutions were obtained by simultaneous optimization of the operational conditions and the heat exchanger network based on pinch analysis. Industrial relevance: Drying is an energy intensive operation in processing. To comply with the upcoming regulations that arise from the EU goals for sustainable development, the energy consumption of drying processes should be reduced drastically. Emerging technologies are the key for the next step in energy efficiency improvement. A closed-loop spray drying system for milk powder production is simulated and optimized in this work. The proposed technologies are: monodisperse droplet drying, membrane contactor and a zeolite wheel. By applying air dehumidification and heat integration the latent and sensible heat are recovered from the exhaust air. The energy consumption for milk concentration and spray drying has the potential to be lowered from 8.4 to 4.9 MJ heat per kg milk powder. Although milk powder has been considered, the proposed system is also applicable to other food products, as well as in the (bio)chemical, pharmaceutical and paper industry

Assessment of air gap membrane distillation for milk concentration

Multi-effect evaporation is the state of the art for concentration of liquid food products to high solid content. Membrane technology with reverse-osmosis and membrane distillation offer an alternative. For the concentration of milk, a reverse osmosis and air-gap membrane distillation network was modelled and optimized. Fouling dynamics and scheduling are taken into account. Reverse osmosis is favourable until its maximum achievable concentration. Air gap membrane distillation is, despite the low operational temperatures, energy intensive for the concentration of milk. A large recirculation flow to keep sufficient cross flow has to be heated and cooled, and the costs for heating and cooling dominate the total costs for product concentration. Moreover, fouling increases the energy requirements. The optimal system for air gap membrane distillation has only one stage operating at a high concentration and relative low flux. Applying multiple stages reduces the investment costs due to smaller units, but the heating and cooling costs increase. Major opportunities to improve the performance of air gap membrane distillation for concentration of milk are: 1) increase the cold and hot side temperatures to their maximum acceptable values, 2) develop spacers that allow lower linear flow velocities in the system and thus lower recirculation rates, and 3) make use of available waste heat

Closed-loop spray drying solutions for energy efficient powder production

This paper introduces a closed-loop dryer system to reduce the energy consumption for milk powder production. The system is based on a monodisperse droplet atomizer which reduces the amount of fines in the exhaust air, and allows dehumidification and recirculation of the air over the dryer. In this way the latent and sensible heat from the dryer exhaust are recovered. Two adsorbent systems for dehumidification are discussed; a membrane contactor with a liquid desiccant, and a zeolite sorption wheel. Four configurations for closed-loop spray drying are simulated and optimized. By heat integration of the adsorber-regenerator system with the dryer and preceding concentration step, the energy consumption is significantly reduced to 4.9 MJ heat per kg milk powder. The final heat integration solutions were obtained by simultaneous optimization of the operational conditions and the heat exchanger network based on pinch analysis. Industrial relevance: Drying is an energy intensive operation in processing. To comply with the upcoming regulations that arise from the EU goals for sustainable development, the energy consumption of drying processes should be reduced drastically. Emerging technologies are the key for the next step in energy efficiency improvement. A closed-loop spray drying system for milk powder production is simulated and optimized in this work. The proposed technologies are: monodisperse droplet drying, membrane contactor and a zeolite wheel. By applying air dehumidification and heat integration the latent and sensible heat are recovered from the exhaust air. The energy consumption for milk concentration and spray drying has the potential to be lowered from 8.4 to 4.9 MJ heat per kg milk powder. Although milk powder has been considered, the proposed system is also applicable to other food products, as well as in the (bio)chemical, pharmaceutical and paper industry

Exergetic comparison of food waste valorization in industrial bread production

This study compares the thermodynamic performance of three industrial bread production chains: one that generates food waste, one that avoids food waste generation, and one that reworks food waste to produce new bread. The chemical exergy flows were found to be much larger than the physical exergy consumed in all the industrial bread chains studied. The par-baked brown bun production chain had the best thermodynamic performance because of the highest rational exergetic efficiency (71.2%), the lowest specific exergy losses (5.4 MJ/kg brown bun), and the almost lowest cumulative exergy losses (4768 MJ/1000 kg of dough processed). However, recycling of bread waste is also exergetically efficient when the total fermented surplus is utilizable. Clearly, preventing material losses (i.e. utilizing raw materials maximally) improves the exergetic efficiency of industrial bread chains. In addition, most of the physical (non-material related) exergy losses occurred at the baking, cooling and freezing steps. Consequently, any additional improvement in industrial bread production should focus on the design of thermodynamically efficient baking and cooling processes, and on the use of technologies throughout the chain that consume the lowest possible physical exergy

Exergetic comparison of food waste valorization in industrial bread production

This study compares the thermodynamic performance of three industrial bread production chains: one that generates food waste, one that avoids food waste generation, and one that reworks food waste to produce new bread. The chemical exergy flows were found to be much larger than the physical exergy consumed in all the industrial bread chains studied. The par-baked brown bun production chain had the best thermodynamic performance because of the highest rational exergetic efficiency (71.2%), the lowest specific exergy losses (5.4 MJ/kg brown bun), and the almost lowest cumulative exergy losses (4768 MJ/1000 kg of dough processed). However, recycling of bread waste is also exergetically efficient when the total fermented surplus is utilizable. Clearly, preventing material losses (i.e. utilizing raw materials maximally) improves the exergetic efficiency of industrial bread chains. In addition, most of the physical (non-material related) exergy losses occurred at the baking, cooling and freezing steps. Consequently, any additional improvement in industrial bread production should focus on the design of thermodynamically efficient baking and cooling processes, and on the use of technologies throughout the chain that consume the lowest possible physical exergy

Membrane distillation for milk concentration

Membrane distillation is an emerging technology to concentrate liquid products while producing high quality water as permeate. Application for desalination has been studied extensively the past years, but membrane distillation has also potential to produce concentrated food products like concentrated milk. Water vapour migrates from the milk feed side to the permeate side by the vapour pressure difference between the two sides of a hydrophobic membrane. Unlike pressure driven membrane filtration high solid concentrations are achievable.Experimental results show that concentrations of 50% total solids can be achieved for milk, which makes membrane distillation a competitor to evaporation. In experiments for skimmed milk, ranging from 40 to 60°C, the flux was found to increase with higher feed temperatures. For skimmed milk with 25% total solids, at 60°C an initial flux of around 16 kg/m2 per hour was achieved. Due to gradual fouling built the flux declined to 8 kg/m2 per hour after 15 hours. At concentrations of 50% total solids the flux declined to 3 kg/m2 per hour.Confocal laser scanning microscopy (CLSM) was used to investigate the size and morphology of the fouling layer. Images indicated homogeneous fouling layers with a thickness depending on the process temperature; lower temperature resulted in thinner fouling layer. Most plausible reason is the lower driving force and transmembrane flux. These lab scale experiments showed promising fluxes, which still can be improved, that are a good starting point for the development of large scale production units