On-line Monitoring of Critical Parameters in Anaerobic Digestion SWIG Workshop 2014

Transcription

1 On-line Monitoring of Critical Parameters in Anaerobic Digestion SWIG Workshop 2014 By: Emmanuel Coolsaet - AppliTek NV

2 Table of contents About AppliTek Introduction Anaerobic digestion and process control AnaSense Anaerobic Control Analyzer AnaSense field experiences Case Sampling preconditioning systems Conclusions

3 This is AppliTek. Established manufacturer of on-line (automatic) analyzers System integrator for several process/utility industries Revenues: +/- 10 mio USD Wholly-owned private company, non stock listed Represented by a distributor network in 100+ countries for local advice and after-sales service

4 Core technology: overview of product lines AnaSense DEDICATED SERIES process analyzers water analyzers TITRATION, ISE, COLORIMETRY SERIES OF SINGLEPARAMETER ANALYZERS SERIES OF HEAVY METAL ANALYZERS ECOTOXICITY MICROBIOLOGY ANALYZERS

5 Introduction 100 years of activated sludge in the UK The past Development of activated sludge systems for the removal of N and P by BNR 1913: patent for Wastewater aeration device based on an airlift piping system, and implemented at Davyhulme Sewage Works 1916: first actived sludge plant at city of Worcester The future Further developments of nitrogen reduction using minimal energy and no organic carbon, focus on granular sludge to reduce footprint. Importance of anaerobic digestion!

6 Anaerobic digestion and process control AD fundamental control issues Complex nonlinear and nonstationary nature of the AD process Potential feedstock disturbances and overloads Presence of toxic and inhibitory compounds Type of digester or proprietary AD technology used Lack of qualified personnel to operate the digester Although anaerobic digestion is a rather mature technology, system failures are still frequent around the world. (Labatut and Gooch, 2012)

7 Anaerobic digestion and process control Worst case scenario: process failure Feedstock characteristics Operational variables Process perturbation Digester upset System failure Time What is the price to pay in case of loss of control? New batch of inoculum (biomass) ~ 20,000 30,000 EUR = instant payback of AnaSense

8 Anaerobic digestion and process control CRITICAL process parameters in AD: Bicarbonate Saprophytic bacteria convert complex organic matter into fatty acids, volatile fatty acids (fermentation step) and CO2. Methane-producing bacteria further reduce the bicarbonate to CH4. Volatile fatty acids Non-specific parameter consisting of short-chain acids: acetic acid, butyric acid, formic acid, propionic acid Intermediate products for methane production. Alkalinity (total partial) The buffering capacity of the digester (ability to resist changes in ph, especially ph drops). When acids accumulate, the alkalinity will gradually be exhausted. Ammonia Ammonia nitrogen can be toxic to the process and is likely to slow down methanogenesis but at the same time can increase buffer capacity.

9 Anaerobic digestion and process control On-line monitoring of critical parameters allows To monitor and control the whole AD process A significantly higher loading rate (higher setpoint) To protect against failure due to VFA accumulation or incoming toxicity

10 AnaSense : Anaerobic Control Analyzer Result of the European TELEMAC R&D project Aim: Development of an efficient and reliable monitoring system for controlling anaerobic digestion.

11 AnaSense : Anaerobic Control Analyzer Research institutes using AnaSense

12 AnaSense : Anaerobic Control Analyzer Unique analysis procedure: Direct acid/base titration with adapted McGhee protocol (1968) Advantages: 1. Virtually no interference from carbonates (are stripped away without boiling) 2. Lower detection limit (lowest range: mg/l VFA) 3. Fairly linear range between ph 4 and 5 for determination of VFA calibration of ph electrode becomes less critical Or: high analytical performance! Last but not least, the highly accurate sampling technique assures high reproducibility, which is not possible with manual titration techniques

13 AnaSense : Anaerobic Control Analyzer Comparing results with reference methods Validation of the AnaSense results (parameter: VFA) with comparison to off-line gas chromatography (GC) : Graph: Testing done on a laboratory Scale UASB reactor. Results from the GC analyzer were recalculated in mol/l and converted in mg/l.

14 AnaSense : Anaerobic Control Analyzer Control strategies: the CUCEI experience We have demonstrated that if the process is managed by a control law (closed-loop) the process methane yield gets close to this value [by using the AnaSense]. Dr. H.O. Mendez, CUCEI COD as CH4, H2S, H2 COD influent COD effluent 0.35 L CH4 / 1 gr COD Theoretical AD yield COD as sludge

15 AnaSense field experiences Tembec pulp & paper plant (Canada) On-line analyzers for new (2012) UASB digester to monitor the inlet water to the wastewater treatment and the water quality after treatment On-line of supply: AnaSense + AppliCOD + EPA Sulphite

16 AnaSense field experiences Novozymes (Denmark) On-line analyzers for new (2013) EGSB digester to monitor aerobic and anaerobic waste water treatment Scope of supply: AnaSense + AppliCOD + TONI (aerobic treatment)

17 AnaSense field experiences City of Clearwater (FL USA) AnaSense was implemented in the framework of a complete rehabilitation program for the city s WWTP plants, including the old anaerobic digesters. Executed in

18 AnaSense field experiences Guy & Wright (UK) AnaSense for new (2008) CSTR-type digester for cogeneration purposes at a tomatoe growing company.

19 AnaSense field experiences Guy & Wright (UK): case AnaSense commissioned in 2008 Family owned tomato growing company Due to the small carbon footprint their tomatoes are nicknamed eco toms Proprietary anaerobic digester design (CSTR like) with mainly fruit and vegetables feedstock (1800 m3 load capacity) Company s challenges: Guy and Wright was not only interested in reduction of carbon footprint but (1) was facing ever increasing heat costs and (2) fierce competition of tomatoes from southern countries.

20 AnaSense field experiences Guy & Wright (UK): results 100% on-line efficiency 0.5 MW continuous capacity AnaSense is used at-line Important performance parameter: VFA/PA ratio (~ FOS/TAC) High COD removal: digester consumes 50 tonnes of feedstock/day Biogas is purified and heat + CO2 is pumped back in the greenhouses Further trial for true on-line operation of AnaSense with AppliTek preconditioning system

21 AnaSense field experiences Guy & Wright (UK): conclusions High capacity factor and on-line efficiency Very high process setpoint An appropriate control strategy begins with process data Hypothesis: what would happen if we stopped the AnaSense? High risk of failure due to the high process setpoint : 2 4 weeks to remediate the digester and restart the methanogenesis. Total cost estimated GBP (2 x AnaSense!). Two reasons: (1) loss of gas production (500 kw on average) and (2) cost of sludge replacement (150 tonnes of biomass)

22 Sampling preconditioning systems EZ-Size filtration EZ-Size sludge filtration Manure extraction system

23 Conclusions I What does AnaSense offer to AD operators? 1. Continuous monitoring of the AD process (almost real-time) 2. Enhances higher loading rate for maximum CH4 production 3. Prevention of digester failure due to VFA accumulation 4. Easy implementation within a dynamic control strategy 5. Easy integration into corporate networks

24 Conclusions II What can you expect from implementing AnaSense? Direct, automatic titration (no volatilization possible) Simultaneous analysis of VFA, alkalinity, bicarbonate, ph, ammonia Rapid results (10-15 min.) allow true process monitoring, protection and optimization Easy to use and inexpensive alternative to gas chromatography Analysis results correlate closely with reference methods i.e. discrete gas chromatography measurements To be combined with sample preconditioning system

25 Contact details Registered office & Contact: AppliTek NV, Venecoweg 19, 9810 Nazareth Belgium Contact us at or through our website Media Visit us at for commercial and technical information Latest news: Connect with AppliTek: