and challenges of Biogas in China

Transcription

1 state-of-the-art the art research progress and challenges of Biogas in China Guanyi ichen School of Environmental Science and Technology Tianjin University November, 2011 Presentation Outline 目录 Significance ifi and necessity Biogas resource properties and potential analysis Biogas technology progress Bottlenecks and Challenges Works done at TJU Concluding remarks 2

2 Significance and necessity 3 Significance and necessity Tradi tional en nergy Shortage? Renewable energy Environmental problem 4

3 Significance and necessity Solar energy Renew wable energy Wind energy Water energy physical py Limited by district Difficult to store Bioenergy Chemical Easy to store Unlimited by district Produce chemicals 5 Significance and necessity There are 0.7 billion tones/a straws production in China 6

4 Significance and necessity Bioethanol High values High cost straw gasification Burning to produce electricity Low efficiency Biogas Low cost Easy to Industrialization 7 Significance and necessity High C:N(40-50:1)of straw is not suitable for biogas production Municipal waste sludge has high organic matter content with low C:N (13-15:1) It is good idea to combining i straw and municipal i waste sludge together to produce biogas 8

5 Biogas resource properties and potential analysis 9 Biogas technology progress 10

6 Bottlenecks and Challenges Waste activated sludge Poor operational stability Slow hydrolysis rate Low C/N Biogas including H 2 S Mesophilic anaerobic digestion Not widely applied Large tank volume Green energy Low biogas production Equipment and pipeline corrosion 11 Bottlenecks and Challenges Straw Anaerobic digestion Green energy C/N=40-50 Acidification Lignocellulosic biomass Biogas slurry and residue Pretreatment N and P removal Biogas including H 2 S Equipment and 12 pipeline corrosion

7 Works done at TJU Ultrasonic sludge disintegration i ti to improve anaerobic digestion efficiency 13 Works done at TJU Waste activated sludge Sludge pretreatment: ultrasonic Slow hydrolysis rate 14

8 Works done at TJU 1. Factors affecting ultrasonic sludge disintegration ultrasonic density ( W/mL) disintegration time (min) sludge concentration (TS) SCOD release rat tio(%) W/ml 0.384W/ml 0.72W/ml 1.44W/ml / Time Time(min) COD increse(mg/l) SC Trend of SCOD release with disintegration time increase Changing of SCOD release ratio with disintegration time (solid content of sludge was 1%) SCOD+(mg /L) TS 1% TS 0.5% Disintegration time(min) SCOD+ change at ultrasonic density of 1.44W/ml for 2 different solid contents

9 Works done at TJU 2. Components in the released liquid of ultrasonic sludge disintegration Protein Polysaccharide DNA Works done at TJU 3. Improvement of Mesophilic Anaerobic Digestion Efficiency of Waste Activated Sludge by Ultrasonic Pretreatment Ultrasonic sludge disintegration before anaerobic digestion will increase biogas production, organic matters removal efficiency, decrease sludge quantity and dhrt of anaerobic digestion.

10 Biogas productions of anaerobic digestion increased greatly with disintegration time increased 400 Sludge disintegrated for 15min biogas pr roduction(m ml/d) Sludge disintegrated for 10 min Sludge disintegrated for 5 min Raw sludge anaerobic digesting time(d) 19 dilution rate 12.5% HRT=8d HRT=10d dilution rate 10% HRT=20d dilution rate 5% HRT=12.5d dilution rate 8% It was interested that specific biogas productions did not reduce with sludge digestion time decreasing, and it increased greatly, which was different from traditionalanaerobicdigestiontheory. anaerobic digestion theory. 20

11 Works done at TJU Enhancement of sludge thermophilic anaerobic digestion by ultrasonic pretreatment 21 Works done at TJU Biogas production under different HRTs HRT(d) Daily biogas production(ml/d) Specific biogas production(l/gvs) Raw sludge Disintegrated sludge(90min) Raw sludge Disintegrated sludge(90min) Under all conditions, anaerobic digestion of pretreated sludge, specific biogas production is more than one of control group. Except for HRT=4d, when sludge is disintegrated before anaerobic digestion, specific biogas production will increase with HRT decreasing, which indicates that ultrasonic sludge disintegration before anaerobic digestion can shorten HRT and will not influence specific methane production. 22

12 Works done at TJU Co-digestion of waste activated sludge and corn straw to improve anaerobic digestion efficiency 23 Works done at TJU Co-digestion of waste activated sludge and corn straw Nutrient balance Mesophilic anaerobic digestion 24

13 Works done at TJU Changes of main components of corn straw after pretreatment Cellulose (%) Hemicellulose (%) Lignin (%) Raw corn straw NaOH pretreatment Water Immersion As far as cellulose growth rate and lignin decrease rate, the water immersion pretreatment was less effective than the NaOH pretreatment. 25 Works done at TJU It is found that co-digestion of WAS and corn straw can raise biogas yield and initial biogas production time is 3-6 days before one of pure WAS. Biogas production lasts for 27 days and cumulative yield is 7 times of AD of pure WAS. 26

14 Works done at TJU Biogas purification 27 Works done at TJU Coolding device Dehumidi fier Purified gas Adsorption tower Vacuum tower Degass ing tower Compressor Air Effluent Biogas Buffer tank Water recycling Pump Flow chart of biogas production 28

15 Works done at TJU Advantages High pressure water adsorption method can remove CO 2 and H 2 S at the same time, and process is simple, investment is low; After biogas is purified, CH 4 content can be more than 97%, which will meet Grade 1 standard of natural gas. Comparison to PSA method, the investment and operation cost of the method is lower, and comparison to amine fluid adsorption method, the energy consumption is lower. Desorption method is simple, energy consumption is low and cost is low. Concluding remarks Anaerobic digestion technology will play a major role in renewable energy and addressing environmental concerns; Adapting AD technology to the biorefinery concept offers new opportunities; AD technologies can be further improved by employing new development in science and biotechnologies; Biogas slurry and residue are main by products from AD system, N and P recovery technology is demanded. 30

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