Experimental and theoretical research on agitated contact drying of sewage sludge in a continuous paddle dryer

Salman

et al. 2020

Energ. Ecol. Environ.

Handling sludge through thermal conversion is environmentally friendly, which, however, requires sludge drying. This work proposed to use the waste heat of flue gas (FG) to dry sludge. The integration of sludge drying in biomass fueled combined heat and power (CHP) plants can clearly affect the performance of downstream processes in FG cleaning, such as flue gas quench (FGQ) and flue gas condenser, and further affect the energy efficiency of CHP. In order to understand the influence, a mathematical model and an Aspen PLUS model were developed to simulate the drying process and the CHP, respectively. Based on simulations, it is found that the increase of feeding rate of sludge and the moisture content of sludge after drying can decrease the water evaporation in FGQ. An increase in the feeding rate of sludge in combination with a drop of moisture content of sludge after drying can decrease the heat recovery from FG. When using dried sludge to replace biomass, the amount of saving could be influenced by the moisture content after drying and the flow rate of sludge. Simulation results show that drying sludge to a moisture content of 40% leads to the maximum biomass saving.

Section: Clean Water External Watermentioning

confidence: 82%

Section: Mathematical Model Of Sludge Dryingmentioning

confidence: 99%

Integrating sludge drying in biomass fueled CHP plants

Salman

et al. 2020

Energ. Ecol. Environ.

“…A previous study performed by Chen et al. [9] indicated that the total drying rate of the dryer could increase to 1.5 times with a 15% increase in the dryer wall temperature. In addition, it is very difficult to enhance the heat transfer on the external side of the paddle since the sludge was directly contacted and the operation environment is harsh.…”

Section: Introductionmentioning

confidence: 97%

“…However, improving the condensation heat transfer coefficient inside the paddle also has a great impact on the drying performance of the paddle dryer because the paddle temperature can be increased. A previous study performed by Chen et al [9] indicated that the total drying rate of the dryer could increase to 1.5 times with a 15% increase in the dryer wall temperature. In addition, it is very difficult to enhance the heat transfer on the external side of the paddle since the sludge was directly contacted and the operation environment is harsh.…”

Section: Introductionmentioning

confidence: 97%

Numerical Investigation of the Effect of Surface Wettability and Rotation on Condensation Heat Transfer in a Sludge Dryer Vertical Paddle

et al. 2023

In this paper, the applicability of advanced heat transfer enhancement technology to a paddle dryer was discussed. A computational fluid dynamics (CFD) method was used to simulate condensation heat transfer on the inner surface of a dryer paddle. The effect of surface wettability and rotation on condensation heat transfer and droplet behavior was studied. The results showed that the present CFD model could properly simulate the condensation process on a vertical surface. With a decrease in the contact angle, the filmwise condensation turned into a dropwise condensation, which resulted in a significant increase in heat transfer coefficient and provided an approximately 5% increase in evaporation rate for the paddle dryer by changing the wettability of the inner surface of the paddle. Additionally, with a change in rotational angular velocity, heat transfer performance was almost unchanged under the filmwise condensation condition. However, rotational motion might cause a decrease in wall temperature and the equivalent evaporation rate under the dropwise condensation condition. Only a 2.4% increase in the equivalent evaporation rate was found in dropwise condensation with rotation, which indicated that changing the wettability inside the paddle could not be an effective means to enhance the heat transfer and drying efficiency of a rotating paddle dryer.

Proceedings of the 2nd 2016 International Conference on Sustainable Development (ICSD 2016)

“…Currently, researches have done a lot of works on sludge drying process [6][7]. Qian [8] did the isothermal drying experiments about the thickness of different sludge layers and species by using the air blowing oven at 40~160 and ℃ modeled the drying dynamics of sludge.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study on Drying Characteristics of Sewage Sludge in Two Kinds of Indirect Heat Drying Equipment

Chen¹,

Deng²,

Chen³

et al. 2017

Self Cite

Abstract-Sludge samples are taken from Qige Waste Water Treatment Plant in Hangzhou. The drying characteristics of sludge are determined by self-made small batch type drying machine. The paddle dryer and disc dryer are used in the drying tests to explore the effect of blade form on the sludge drying viscosity zone. Different heat source temperature and drying machine speed are set up for the same kind of drying machine to research on the effect of working conditions on the drying characteristics of sewage sludge. It is discovered that the paddle dryer has a better ability to overcome the sludge viscosity zone. High speed and drying temperature can speed up the sludge drying and improve the dry deterioration in the sludge viscosity zone. But it is necessary to consider the factors of equipment stability and safe operation at the same time.