Thermal drying of wastewater sludge with crack formation

An innovative technology for sewage treatment systems is proposed. A mixture of sewage sludge and char particle is subjected to drying in the progress of composting in an updraft column. Exothermic heat generated during composting is utilized for energy of sludge drying. The char particle in the mixture contributes to enhancement of composting and drying rate. This study presents drying and composting behaviors of sludge to examine the effect of char addition. A fundamental drying experiment was carried out by hot-air heating of the sample in a small vessel. The drying characteristic curve for a mixture of sludge and char was greater than the sample of only sludge over a whole period if the drying rates were compared with the same moisture content. The drying behavior could be analyzed with a reasonable agreement by the water front receding model. The enhancement effect of drying and composting of sludge by char addition was confirmed by examination using a pilot scale of the updraft column whose volume was 50 m 3 . Sludge with 400% dry base (80% wet base) in moisture content could be dried successfully to lower moisture content than 67% dry base (40% wet base) only by exothermic heat during composting without supplying any auxiliary energy from the outside, and the treatment time was reduced by mixing char in sludge. The behavior was analyzed with a satisfactory agreement by a theoretical model employing moisture diffusion parameters determined from the drying characteristic curve.

Section: Please Scroll Down For Articlementioning

confidence: 99%

Drying of Sewage Sludge During Composting in an Updraft Dryer with the Concept of Using Self-Energy Generated Within the System

Itaya

Kobayashi

et al. 2014

“…A hard and relatively impermeable crust is formed at its exterior surface, which is accompanied with appearance of 3 shrinkage [17,18] and cracks [19] . According to statement of Tao [20] , it is found that the peak drying rate of sludge cake with cracks would be higher than that of the sludge cake without cracks, being attributable to additional surface yielded by artificial cracks, and the drying rate of sludge cake with fully developed cracks could be higher than that from a saturated sand bed under identical drying conditions by 40% [21] . Via further work, Tao [22,23] investigated how crusts and cracks formed and developed on sludge cake on the premise that there were or were not artificial cracks.…”

Section: Introductionmentioning

confidence: 99%

Drying Kinetics and Characteristics of Sewage Sludge/Rice Straw Mixture

Cai

Xiao

et al. 2015

This study aimed at investigating thin-layer drying characteristics of the sludge mixed with different rice straw contents (1% wet basis (wb), 2% wb, 3% wb and 5% wb). The experimental results showed that adding 1%wb, 2%wb and 3%wb rice straw to sludge is helpful for improvement in drying rate of sludge as the surface area and cracks increase but the drying rate of the sludge mixed with 5%wb rice straw decreasing with reduction in thermal conductivity. When the content of rice straw is 2%wb, the increase amplitude of drying rate is the highest, it increased by 14.6%, 14.8%, 16.0% and 17.6% at 100°C, 120°C, 140°C and 160°C, respectively. The model proposed by this study gave better prediction compared with the other models and satisfactorily described drying characteristics of sludge/rice straw mixture as well, and is applicable under the given experimental conditions. The values of R 2 , RMSE and 2 χ varied from 0.99935 to 0.99992, 0.00295 to 0.00830 and 0.00001 to 0.00007, respectively.

“…Thermal drying is often needed to achieve intense dewatering of materials. [13][14][15][16][17] Regardless of the process adopted, energy is utilized to drive moisture out and overcome the reversible and irreversible losses.…”

Section: Introductionmentioning

confidence: 99%

Unified Analysis of Dewatering and Drying of Sludge Cake

Hsu

Mujumdar

et al. 2010

To remove water from a suspension one needs to break down the binding energy between the adjacent water and the solid surface and to convey this water out of the suspension system. Using the binding energy between water and solids and the disrupting energy provided by mechanical and thermal means, this work presents a unified analysis on the dewatering of wet materials using binding energy as a clarification index. The binding energy versus residual water content plot for a wastewater sludge estimated the extent of dewatering each stage and the corresponding energy requirement.