Bio-drying Municipal Solid Waste in a rotary Drum Reactor. The effect of Biomass Temperature and Inoculation

Transcription

1 Strategic Waste Management Planning in SEE, Middle East and Mediterranean Region Bio-drying Municipal Solid Waste in a rotary Drum Reactor. The effect of Biomass Temperature and Inoculation Novi Sad 10 th and 11 th December, 2009 Kyriakos Hapeshis University of Cyprus Vassilico Cement Works Cyprus Research Promotion 1 Foundation

2 MSW (tones) Introduction Increase of MSW European Landfill Directive Mechanical Biological treatment Production of MSW in Cyprus Treatment of biodegradable fraction of MSW Year Compost Biogas and digestate Solid recovered fuel Stabilized residue for landfill disposal Biodrying 2

3 What is biodrying? Introduction Biodrying is the utilization of heat released during the aerobic decomposition of biodegradable solid waste in order to reduce the moisture content and partially stabilize the waste Limited information about control and optimization of biodrying of MSW Only Few studies are referred in the literature and these were conducted at laboratory scale using static systems Our study was performed in a continuously agitated semi-industrial scale rotary drum reactor 3

4 Rotary Vs Static biodrying Rotary biodrying is an alternative approach to static methods with significant advantages Increases microbial activity and heat generation at low moisture content Reduces process retention time Improves particle size reduction Improves homogeneity of the end product 4

5 Materials and Methods Semi industrial rotary drum with 1.2m diameter and 5 m length Paddles to increase the contact time between air entering and feedstock. enhance moisture removal PLC controls the process and records data 5

6 Materials and Methods Shell with a 40 mm insulation of glass wool to reduce heat losses and improve the efficiency of biodrying process Two fans to provide airflows equivalent to 30m³/h and 100m³/h Glass wool 40 mm Motor with frequency controller gear to provide rotation speed rpm integral load cell system 6

7 Experimental Design Unsorted waste were collected from 6 food outlets Add card and paper Biodried product was screened to 40 mm and was added (0%, 10% and 20%) Rotation speed 0.1 rpm Continuous airflow 30m³/h biomass temperature was controlled by a 2kw fan, at the set points (40 C, 50 C, 60 C ) 7

8 Fundamental conditions applied during the experimental trials Trial Feedstock composition Biomass temperature Rotation 1A 90 % mixed MSW/ 10 % mixed paper 40 Continuous at 0.1 rpm 1B 90 % mixed MSW/ 10 % mixed paper 50 Continuous at 0.1 rpm 1C 90 % mixed MSW/ 10 % mixed paper 60 Continuous at 0.1 rpm 2A 2B 2C 3A 3B 3C 80 % mixed MSW/ 10 % mixed paper/ 10 % recycled product 40 Continuous at 0.1 rpm 80 % mixed MSW/ 10 % mixed paper/ 10 % recycled product 50 Continuous at 0.1 rpm 80 % mixed MSW/ 10 % mixed paper/ 10 % recycled product 60 Continuous at 0.1 rpm 70 % mixed MSW/ 10 % mixed paper/ 20 % recycled product 40 Continuous at 0.1 rpm 70 % mixed MSW/ 10 % mixed paper/ 20 % recycled product 50 Continuous at 0.1 rpm 70 % mixed MSW/ 10 % mixed paper/ 20 % recycled product 60 Continuous at 0.1 rpm 8

9 Process Monitoring The temperature (inside the drum, exhaust air and ambient air) was recorded every 30 min by the PLC Net weight of material was recorded every hour Sampling on a daily basis Samples passing through a 30 mm screen Moisture determination in unsorted biodried output ph, Moisture content, Volatile solids Ash content, calorific value 9

10 Temperature ( o C) Temperature ( o C) Temperature ( o C) RESULTS Temperature profiles 0 % product recycling A 1B 1C 10% product recycling A 2B 2C 20% product recycling A 3B 3C Biomass temperature was more stable in trials with temperature control within the mesophilic range (35-40 C ) Instability observed at high process control temperature (1B, 2B, 1C, 2C) In trials with thermophilic temperature control and 0-10% product recycling temperature declined below the set point value, 1-2 days after starting the trials (indicating process inhibition related to acidification) 10

11 ph ph ph RESULTS 8 7,5 7 6,5 6 5,5 5 4,5 4 0% product recycling 1A 1B 1C ph profiles ph initially declined in all trials Acidification became more severe with increasing biomass temperature and decreasing product recycling 10% product recycling 8 7,5 7 6,5 6 5,5 5 4,5 4 2A 2B 2C 20% product recycling 8 7,5 7 6,5 6 5,5 5 4,5 4 3A 3B 3C The minimum ph values occurred in trial 1C with temperature control at 60 C and no product recycling Acidification was less severe at all temperatures with increasing product recycling 11

12 Moisture content (%) Moisture content (%) Moisture content (%) RESULTS 70 Moisture reduction (BDR) 0% product recycling A 1B 1C 10 % product recycling Biodrying rate increased with decreasing temperature and increasing product recycling The highest BDR occurred at 50 C and 20% product recycling (Trial 3B) The lowest BDR occurred at 60 C and 0% product recycling (Trial 1C) 2A 2B 2C 20% product recycling A 3B 3C 12

13 Dry solids (% of initial DS) Dry solids (% of initial DS) Dry solids (% of initial DS) RESULTS Dry solid decomposition rates profiles (DSDR) % product recycling Similarly, DSDR increased with decreasing biomass temperature and increasing product recycling 80 1A 1B 1C 10% product recycling 100 The highest DSDR occurred at 50 C and 20% product recycling (Trial 3B) A 2B 2C The lowest DSDR occurred at 60 C and 0% product recycling (Trial 1C) % product recycling A 3B 3C 13

14 Effect of thermal process control regime and product recycling rate on BDR and DSDR Trial r 2 P BDR* Regression equation constant Average DSDR (g kg -1 d -1 ) 1A 0,96 <0.01-0,248 57,59 25,71 1B 0,88 0,02-0,120 58,18 22,29 1C 0,98 <0.01-0,064 60,85 15,71 2A 0,99 <0.01-0,285 47,18 26,67 2B 0,98 <0.01-0,125 45,79 21,43 2C 0,96 <0.01-0,088 45,62 17,14 3A 0,99 <0.01-0,335 41,87 33,33 3B 0,99 <0.01-0,440 42,05 44,00 3C 0,99 <0.01-0,197 40,56 29,20 *BDR = % moisture reduction per hour BDR and DSDR increased with decreasing biomass temperature and increasing product recycling The highest BDR was 0.44% moisture reduction per hour The highest DSDR was 44g kg -1 d -1 14

15 Chemical characteristics and calorific value of SRF Trial Moisture Content (%) Volatile Solids (%) Ash content (%) Calorific Value (MJ/Kg) 1A B C A B C A B C Screened material less than 30mm accounted for about % of the biodried output Volatile solid ranged from % Ash content ranged from % Calorific Value ranged from MJ/kg 15

16 DISCUSSION AND CONCLUSIONS Optimum temperature for biodrying shifts to higher values with increasing product recycling Rotary biodrying process can operate efficiently at higher temperature when adequate biodried product is recycled.. Lower energy consumption Severe acidification and acid inhibition occurred at thermophilic biomass temperatures and no product recycling Acidification became less severe with increasing product recycling and temperature control within the mesophilic range: Due to presence of NH 3 released from protein decomposition DSDR and BDR increased with increasing product recycling irrespective of the biomass temperature because: 1. increased bio-available nitrogen 2. increased microbial concentration 3. reduced the initial moisture content 16

17 Thank for your attention!! 17