Developments in the Thermal Drying of Sewage Sludge

Löwe, Paul

doi:10.1111/j.1747-6593.1995.tb00944.x

Cited by 58 publications

(30 citation statements)

References 5 publications

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“…Nevertheless, during the application of this sort of process, the product passes through three distinguish able phases or zones as reported by Lowe [8] and illustrated in Fig. 18.…”

Section: Conductive Drying Of Wastewater Sludgementioning

confidence: 61%

“…Representative examples of the industrial dryers are highlighted in Fig. 2 [8]. The specific energy consumption changes from one dryer to another and vary from 700 kW h to 1400 kW h per ton of evaporated water.…”

Section: Parametermentioning

confidence: 99%

“…Several studies [1,8,18] have shown a typical sludge drying curve which can be divided mainly into two parts, the constant drying rate and the falling drying rate, as illustrated in Fig. 5.…”

Section: Convective Drying Of Wastewater Sludgementioning

confidence: 99%

See 2 more Smart Citations

Review on fundamental aspect of application of drying process to wastewater sludge

Bennamoun

Arlabosse

Léonard

2013

Renewable and Sustainable Energy Reviews

198

103

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a b s t r a c tThe objective of this work is to give the fundamental information that should be known about wastewater sludge drying. Three methods are mainly applied: convective drying, conductive drying and solar drying, each one presenting different characteristics. When applying convective drying three phases are distin guished: adaptation phase, constant drying rate phase and falling drying rate phase. Experimental works show that several parameters influence the drying kinetic during this process, such as the origin of the sludge and operating conditions. Imaging techniques allow observing three phenomena that happen during convective drying: shrinkage, cracks and skin formation. When applying conductive drying and considering the torque variations, the product passes through: pasty phase, lumpy phase and granular phase. The results show no regular shape of the drying kinetic with high values of the drying rate and the heat transfer coefficient during the first phase. A special focus is given into the sticky phase which reduces performances of the dryer. The third applied drying method is solar drying, which depends wholly on climatic conditions, such solar radiations and air temperature. Besides, for this method no regular shape of the drying kinetic can be observed, with high drying rate values during favorable conditions and low drying rate values during unfavorable conditions. The presented studies dealing with solar drying of wastewater sludge are limited to the variations of the different air temperatures registered inside and outside the drying chamber with the product temperature and their humidity with study of the pathogen reduction. Finally, some innovative developed methods are exposed in this review, such as the use of frying and super heated steam.

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“…Nevertheless, during the application of this sort of process, the product passes through three distinguish able phases or zones as reported by Lowe [8] and illustrated in Fig. 18.…”

Section: Conductive Drying Of Wastewater Sludgementioning

confidence: 61%

Section: Parametermentioning

confidence: 99%

See 1 more Smart Citation

Review on fundamental aspect of application of drying process to wastewater sludge

Bennamoun

Arlabosse

Léonard

2013

Renewable and Sustainable Energy Reviews

198

103

View full text Add to dashboard Cite

show abstract

“…Water exists in four states in a complex water matrix: free water, capillary-held water, surface water, and chemically bound water. 10,11 Free water is defined as the water removed during the constant drying-rate period. The final TS concentration achieved by removing this water fraction varies from waste to waste, and it is estimated to be between 200 and 250 g/kg for livestock wastes.…”

Section: Semi-continuous Evaporation Testsmentioning

confidence: 99%

Pig Slurry Concentration by Vacuum Evaporation: Influence of Previous Mesophilic Anaerobic Digestion Process

Blasi

Flotats

2003

Journal of the Air & Waste Management Association

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Water can be removed from pig slurry by evaporation, through the application of wasted heat from a power plant or from other processes. Apart from obtaining a concentrate with an obviously higher nutrient concentration than the original slurry, another objective of water removal is to obtain water as condensate, which could be reused. The objective of this work was to study the vacuum evaporation of pig slurry liquid fraction and to evaluate condensate composition as a function of both pH (4, 5, and 6) and pig slurry type (fresh slurry and anaerobically digested slurry). Batch experiments showed that condensate characteristics, total ammonia nitrogen (NH 3 -N), volatile fatty acids (VFA), and chemical oxygen demand were strongly dependent on initial slurry pH. In addition to producing part of the required thermal energy, previous anaerobic digestion presented several other clear advantages. The consumption of VFA and other volatile organic compounds during anaerobic digestion reduced the volatilization of organic matter in the evaporation treatment and, consequently, provided a higher quality condensate.

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“…Meanwhile, the time consuming for sludge drying to the moisture of 20 % decreases from 482 min (120°C) to 200 min (180°C). The drying process of sewage sludge normally undergoes a heating period with a constant rate period followed by two falling rate period [10]. The heating period is commonly short, generally not be considered.…”

Section: Resultsmentioning

confidence: 99%

Study on optimal energy efficiency of a sludge drying-incineration combined system

Wang

Chi

et al. 2014

J Mater Cycles Waste Manag

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Thermal drying is a frequently used technology to further remove the water in dewatered sludge. However, it is an expensive solution due to its highly energy consumption. The combination of sludge drying and incineration system, in which, the energy generated from sludge incineration is reused to sludge drying, can largely save the energy consumption of sludge treatment facilities. A bench-scale paddle sludge dryer was built to study the drying characteristics of sludge. Results show that, a significant fluctuation of sludge drying rate and stirring power emerges at the moisture content of 55-65 %. An energy model was established based on a sludge drying and incineration project. The most reasonable dryness of sludge outlet from sludge dryer and input to sludge incinerator was analyzed, in the purpose of achieving optimal energy efficiency. The mono-incineration of dry sludge can be achieved at 850°C combustion temperature, when sludge lower heating value (LHV) is about 11213 kJ/kg and moisture content is about 60 % w/w. The effect of operation conditions, including sludge moisture content, LHV, and operation load were analyzed based on the energy model. This energy model could be applied for the improvement of energy efficiency of sludge drying and incineration combined system.

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Developments in the Thermal Drying of Sewage Sludge

Cited by 58 publications

References 5 publications

Review on fundamental aspect of application of drying process to wastewater sludge

Review on fundamental aspect of application of drying process to wastewater sludge

Pig Slurry Concentration by Vacuum Evaporation: Influence of Previous Mesophilic Anaerobic Digestion Process

Study on optimal energy efficiency of a sludge drying-incineration combined system

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