China Agricultural University (CAU) jingyuan@cau.edu.cn Naxos, June - - PowerPoint PPT Presentation

Jing Yuan

China Agricultural University (CAU) jingyuan@cau.edu.cn Naxos, June 13, 2018

Effects of the aeration pattern, aeration rate and turning frequency on municipal solid waste biodrying performance

Outline

• Background
• Objectives
• Materials and Methods
• Results and Discussion
• Conclusions

Background

203,6 20 40 60 80 100 60 120 180 240 MSW collection Rate of harmless disposal

MSW collection (millon t /a) Rate of harmless disposal (%)

• High proportion of kitchen waste

Organic matter 70~80% Water content 70~80%

• High proportion of high heat value

substance

Plastic, paper, fabric and woody waste ＞30% The HHV of MSW increase.

Huge potential energy sources

The amount of municipal solid waste (MSW) produced in China and the rate of harmless disposal (%)

6 5 % 1 3 % 1 2 % 3 % 3 % 2 % 0 % 0 % 2 % kitchen waste plastics paper fabric woody waste glass rubber metal Ash

4

Disposal way of MSW and biodrying technology

200 400 600 800 1000 Landfill Composting Incineration

• thers

Disposal plant of MSW

 The main factors restricting the recycling of MSW

W ater recovery

High m oisture Biodrying, a pretreatment method targeting incineration, which aims at removing water from bio-wastes with high water content (Zhang et al., 2009). Besides having a high water-removal rate, this approach is expected to constrain

• rganic degradation, thereby preserving

energy for subsequent utilization, e.g., as residue-derived fuels (RDF) (Velis etal., 2009).

Heat cycle

Combustion

Effect of aeration rate on biodrying

High aeration rate Low aeration rate

Lower matrix temperatures Less evaporated water Lower water carry capacity less evaporated water will be removed

Balance

Temperature aeration

Optimum aeration pattern and rate

The main objective

To study the interactive influences of the aeration pattern, aeration rate, and turning frequency on biodrying performance of municipal solid waste (MSW).



Water-removal rate



Biodrying index



Mass balance



Heat balance

Materials

7

Materials MSW Cornstalks Mixes of MSW and cornstalks

Moisture (%)a

71.47 4.67 60.39

Bulk density (kg·m−3)a

694.97 168.14 513.13

Free air space (FAS) (%)b

30.85 84.23 51.01

Total carbon (TC) (%)b

35.97 42.72 39.48

Total nitrogen (TN) (%)b

1.82 1.11 1.47

C/N

19.76 38.49 26.86

Volatile solids (VS) (%)b

72.64 89.3 80.91

Lower heat value (LHV) (kJ·kg−1)a

• 366

14664 2422

Cornstalks 1 0 % MSW 9 0 %

8

C-LGX

Biodrying vessel（60L）

condensate Condensate collection Refrigerator 50 mm

9

Design of the experiment

Treatment Aeration method Aeration rate (L kg−1 DMmin−1) Turning frequency Total aeration volume (m3)a I1

Intermittent (Aerate 10 min and stop 20 min during Days 0–6) + Continuous (Days 5–18) 0.35 (average 0.3) 3 days 90

I2

Intermittent (Aerate 30min, stop 30 min) 0.6 (average 0.3) 3 days 98

C1

Continuous 0.2 3 days 55

C2

Continuous 0.3 3 days 91

C3

Continuous 0.4 3 days 128

C4

Continuous 0.5 3 days 163

C5

Continuous 0.6 3 days 195

T0

Continuous 0.3 Non 90

T2

Continuous 0.3 2 days 93

T6

Continuous 0.6 6 days 198

Actual total aeration volume during the biodrying process.

Results and discussion

20 40 60 80 100 3 6 9 12 15 18 C1 C2 C3 C4 C5 ambient

Time (days)

20 40 60 80 100 3 6 9 12 15 18 T0 T2 C2 T6 ambient

Time (days)

20 40 60 80 100 3 6 9 12 15 18 C2 I1 I2 C5 ambient

Time (days)

Temperature ()

 Temperature

 No significant differences were found between the 10 treatments overall.  The temperature was affected little by increasing the aeration rate above that required to satisfy the oxygen demand of the microorganisms. Treatment I1 I2 C1 C2 C3 C4 C5 T0 T2 T6 TI () 756 733 737 759 695 681 701 761 688 644 TI: the temperature integration index

0,0 0,5 1,0 1,5 2,0 3 6 9 12 15 18 T0 T2 C2 T6

Time (days)

0,0 0,5 1,0 1,5 2,0 3 6 9 12 15 18 C1 C2 C3 C4 C5

Time (days)

0,0 0,5 1,0 1,5 2,0 3 6 9 12 15 18 C2 I1 I2 C5

Time (days) Water removal rate (kg d-1)

 Water-removal rate during biodrying

 In all the treatments, water loss mainly occurred in the thermophilic phase (days 7~12), accounting for 50%~68%.  Air volume and water evaporation significantly positively correlated between days 1~9.  Water loss mainly depended on the total aeration volume, different aeration patterns and turning frequency affecting water loss little at a constant total aeration volume.  C4 (0.5 L·kg−1 DM·min−1) is the optimum aeration rate, biodrying performance decreasing at aeration rates higher than the optimum.

 Water and volatile solid (VS) losses

Treatments Water removal rate (%) VS loss rate (%) Biodrying index （I） Heat utilization rate （%） I1 51.53 39.02 2.86 50.6 I2 49.74 39.69 2.72 52.0 C1 31.23 36.51 1.7 42.3 C2 48.87 40.39 2.45 53.3 C3 56.76 38.8 3.17 59.8 C4 66.01 34.72 4.12 68.3 C5 62.39 34.47 3.81 65.8 T0 41.91 35.31 2.32 43.8 T2 49.87 41.45 2.49 51.2 T6 59.44 35.38 3.63 60.1 Biodrying index （I）= water loss /VS loss Heat utilization rate （%）=The heat used by evaporation/Generated heat by VS degradation

 Characteristics of the final biodrying product

Treatments I1 I2 C1 C2 C3 C4 C5 T0 T2 T6 Moisture (%)a

45.8 46.2 54.04 47.47 41.35 33.25 37.33 51.89 45.34 42.43

Bulk density (kg·m−3)a

369.5 359.2 470.35 396.32 320.94 290.89 315.76 482.94 316.29 328.13

FAS (%)b

67.10 68.3 57.63 64.82 71.84 74.81 72.29 57.12 71.86 70.92

TC (%)b

33.5 32.2 31.33 30.64 31.04 31.99 31.33 31.49 32.6 33.01

TN (%)b

1.9 1.9 1.74 1.86 2.07 1.93 2.08 1.96 1.93 1.94

C/N

18.0 17.0 18.01 16.47 15.00 16.58 14.58 16.07 16.89 17.02

VS (%)b

66.2 63.3 64.08 63.48 65.17 66.57 67.40 66.19 61.40 67.1

LHV (kJ·kg−1)a

4435 4569 3717 4499 7177 9440 8678 3165 4348 5333

The initial moisture content was 60.39%, treatment C4 gave the lowest final moisture content (33.25%) and the highest LHVs 9440 kJ kg-1.

Conclusions

• Biodrying performance was most affected by aeration volume.
• Biodrying performance decreased above the optimum aeration rate.
• An aeration rate of 0.5 L·kg−1 dry matter min−1 and one turn each 3 d

were optimum.

• The optimum results were 66% water removal and 68.3% of heat

used for evaporation.

Acknowledgment

The National Key Research and Development Program of China (No.2017YFNC060039).

Thanks for your attention! Questions?