1. Organic waste management by a small- scale innovative automated system of anaerobic digestion Supported by the European Commission under the research for SME associations theme of the 7th Framework Programme for Research and Technological Development 1 st August 2012 to 31 st July 2015

2. Energy management module The energy management system is responsible for : biogas valorisation (small, certified biogas boiler) heating of the biological process (heat exchanger for hot water bath) COMBUSTIONHEAT RECOVERY

3. System requirements 1) Biogas valorisation CH4 concentration related to the type of feedstock used and digester operation Use of natural gas during start- up, or transient digester operation H2S content up to 2-3% by vol water vapour, even more so due to the higher operating temperature H 2 S levels should be reduced below 50 ppm and biogas should be dried 2) Heating of the biological process “Thermophillic” mode requires an operating temperature of 57 oC ± 2 oC 3) Cost effectiveness and H&S approval Adjust the mixture of air and fuel 4) Safe and User friendly system

4. Design answers 12 kW natural gas boiler (to cope with start up) + 6 kW thermal output modified natural gas boiler running only on steady state biogas stream (approximately 60/40 % vol of CH4/ CO2) small natural gas assisted flare to deal with poor quality intermittent biogas for Environmental and H&S reasons Simple PLC, Relays and Switches for Automation (gas and water circuits) Detectors for CO, HC & Temperature Linked to Warning/Cut Off Systems HAZOP undertaken to maximise safety 12 kW natural gas boiler (to cope with start up) + 6 kW thermal output modified natural gas boiler running only on steady state biogas stream (approximately 60/40 % vol of CH4/ CO2) small natural gas assisted flare to deal with poor quality intermittent biogas for Environmental and H&S reasons Simple PLC, Relays and Switches for Automation (gas and water circuits) Detectors for CO, HC & Temperature Linked to Warning/Cut Off Systems HAZOP undertaken to maximise safety

5. Burner head: cylindrical multi-hole premixed burner Hundreds of the identical holes producing premixed laminar lean flames The panel controls both of the flowrate of the incoming fuel and regulation of the water circuits. Direct modification to this panel is difficult. Minimum modification should be considered for lower cost, H&S approval and straightforward service by any gas engineer in the future Modified biogas boiler

6. System front view

7. System back view

8. Components Biogas solenoid valve Biogas particulates filter Biogas spill valve to control and maintain the pressure Drain pots to collect possible condensate in the gas both before and after the biogas blower (to be checked and emptied on a daily basis) Biogas blower Biogas solenoid valve Biogas particulates filter Biogas spill valve to control and maintain the pressure Drain pots to collect possible condensate in the gas both before and after the biogas blower (to be checked and emptied on a daily basis) Biogas blower Secondary circuit drain Secondary circuit pump Temperature sensors show temperature after biogas boiler and after natural gas boiler Secondary circuit drain Secondary circuit pump Temperature sensors show temperature after biogas boiler and after natural gas boiler Biogas pressure sensor Fire and heat sensor Carbon monoxide sensor Methane sensor LPG sensor (if used) Electricity meter Fire and gas panel Canopy ventilation fan Relays timers for the coordination of the combustion process and subsequently hot water production and regulation. Biogas pressure sensor Fire and heat sensor Carbon monoxide sensor Methane sensor LPG sensor (if used) Electricity meter Fire and gas panel Canopy ventilation fan Relays timers for the coordination of the combustion process and subsequently hot water production and regulation. Flare spill valve Natural Gas Assisted Flare to burn off the low quality biogas produced during transient periods (Large Bunsen Burner) for environmental and H&S reasons Flare spill valve Natural Gas Assisted Flare to burn off the low quality biogas produced during transient periods (Large Bunsen Burner) for environmental and H&S reasons Primary air bleeds Primary circuit pump Primary circuit drain Primary water over pressure vent Temperature sensor to monitor flow/return Heat exchanger (HE) 3 way valve to control heat supply from HE Heat meter to record the amount of heat supplied by the BB. It has an internal display and a pulsed output available. Biogas boiler (BB) Natural gas boiler (NGB) Primary circuit expansion pressure tank + fill point and pressure gauge on top Primary air bleeds Primary circuit pump Primary circuit drain Primary water over pressure vent Temperature sensor to monitor flow/return Heat exchanger (HE) 3 way valve to control heat supply from HE Heat meter to record the amount of heat supplied by the BB. It has an internal display and a pulsed output available. Biogas boiler (BB) Natural gas boiler (NGB) Primary circuit expansion pressure tank + fill point and pressure gauge on top NG solenoid valve NG meter NG condensation drain NG solenoid valve NG meter NG condensation drain Blow off valve Blow off vent Blow off valve Blow off vent

9. Exterior connections: physical connections between the combustion module and water feed, main support fuel, biogas etc. Condensation Pots for Biogas Moisture: To remove moisture in the biogas in order to improve the quality of combustion including a filter for particulates. Spill Valves for Flare, Emergency Blow Off: biogas control. Heat Energy Meter: records the amount of heat supplied by the biogas Components

10. WATER LOOP Digester calls for Heat (thermocouple – settings can be changed) Heat is supplied by a secondary circuit fed by a primary circuit thru’ a heat exchanger Reason to achieve the required accuracy on temperature control (55 °C ± 2°C) FUEL (NG or Biogas) LOOPS Priority is to draw/burn biogas off the digester IF NO gas OR NO flame (poor quality = unsuccessful (15 “sparking clicks”) = use FLARE!) TURN ON the NG boiler Repeat cycle (draw biogas) every 30 minutes Sequence of Operation (Summary)

11. Water Loop

12. The AD digester calls for heat using (temperature sensor T4) and switches on the two circulating pumps. Temperature sensor T1 indicates temperature of the secondary circuit, and should this reading fall below for example 70 oC then the biogas boiler is fired up. If temperature sensor T2 does not make the required temperature in a define set time (say 1 min.) then the natural gas boiler fires up in support, and its output is modulated to deliver a set temperature at T3. An option is to use a mixing valve in the secondary circuit to limit AD feed-water temperature for example to prevent digester overheating. Water Loop

13. Fuel Loop

14. Biogas from the AD digester is expected at 5 mbar, but can be boosted using a fan to provide a high enough supply pressure to the modified biogas boiler. If there is no biogas take off and pressure limit reaches in the AD digester, the pressure maintaining valve lifts to combust gas in the flare (which has a support gas pilot light). If everything fails the Pressure Relieve Device (valve) releases gas to atmosphere for safety

15. Water Loop Biogas LoopNatural gas Loop Water, biogas and natural gas loops

16. Biogas is piped from the biogas reactor via gas treatment to the biogas inlet on boiler system. Biogas fed to the boiler must be clean and dry. The biogas feed splits: one way goes to the flare and the emergency blow off valve and the other to the biogas solenoid. Biogas reactor Gas treatment Boiler system Emergency and blow off valve Biogas solenoid Biogas inlet

17. Heat is required biogas pressure rising above approx. 10 mbar IF the solenoid is opened the biogas blower starts raising biogas pressure to 19 mbar to feed the biogas boiler the boiler is started IF the pressure of the reactor and system drops the biogas boiler turns off the biogas blower stops the solenoid closes Automatic functioning IF Not running the solenoid is closed biogas over 25 mbar is vented to the flare via the vent spill regulator. IF Pressure rises above 35 mbar emergency blow off valve releases biogas pressure via the emergency biogas blow off outlet

18. Pressure sensor > 20 mbar? Pressure drops < 8 mbar? relay 1 high blower on biogas heat demand high (thermostat input) biogas solenoid open biogas boiler will start. relay 1 low blower off biogas heat demand low biogas solenoid close biogas boiler will stop. Automatic functioning

19. The NG boiler is set to heat the primary water to a temperature below that of the BB so the NG boiler should only fully fire when biogas is not available. The BB temperature should be set slight higher than the NG boiler to allow it to use available biogas in preference to using natural gas. If there is no biogas take off and the lower pressure limit reached in the AD digester, then the support fuel will be called upon to provide the required heat. biogas available signal low (relay 1? adjustable value of setting) Boilers are set up to 82°C (relay 1? This value of setting is adjustable) and will both reach and regulate to this Natural gas heat demand signal high or constant primary circuit pump on controlled by output from natural gas boiler Natural gas heat demand signal low Primary circuit pump off (controlled by natural gas boiler) Biogas boiler relay 1 inhibited Excess gas will vent to flare via flare spill valve. Biogas boiler Natural gas boiler Automatic functioning

20. Power on and E-stop in run position, the following will be in operation: Extractor fan on Biogas boiler power on constant Natural gas boiler power on constant Secondary circuit pump on constant 24v power supply on constant Pressure sensor on constant (24v) PID* controller on constant (24v) 3 way valve on constant (24v) Display gauges on constant (USB power supply) Power on and E-stop in run position, the following will be in operation: Extractor fan on Biogas boiler power on constant Natural gas boiler power on constant Secondary circuit pump on constant 24v power supply on constant Pressure sensor on constant (24v) PID* controller on constant (24v) 3 way valve on constant (24v) Display gauges on constant (USB power supply) Standard operation *A proportional-integral-derivative controller (PID controller) is a control loop feedback mechanism (controller) widely used in industrial control systems. A PID controller calculates an error value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process through use of a manipulated variable.

21. The temperature in the primary is set by the individual boiler temperature controls. The temperature setting for the bioreactor is set on the PID controller on the front panel of the cabinet. The PID controller monitors the temperature in the bioreactor and controls a 3 way valve in the secondary circuit to supply sufficient heat from a heat exchanger with the primary circuit. Over time this should achieve accurate control of the temperature in the bioreactor. Settings

22. Control panel information 4-20mA out put on OUT2 contacts 3 and 4 The PID controller CB100FK07-8*AN5N1 has an RS 485 data output The heat meter has a pulsed output. RKCCB100FK07-8*AN5N1 Control actionFPID action with autotuning (reverse action) Input rangeK07K type temperature sensor 0 to 1372 degree C OUT18Current 4 to 20mA Alarm1/2ANDeviation high1No Alarm2 Comms5RS-485 Water proofNNo

23. The safety system monitors for methane, CO, LPG (if used) and fire and heat. If methane CO or LGP are detected the system shuts down and leaves the extractor fan running. If fire or heat is detected the system including the extractor fan shuts down and an external fire alarm output is available. Alarms: Security Methane or LPG or CO alarm ONbeacon sounder on everything but extractor fan off Heat / fire alarm ONall off External output Power cycle to reset alarm? Power off or E-stop offall off

24. Connections into left side of boiler cabinet – dimensions to follow Biogas in½” BSP female Natural gas in½” BSP female Biogas to flare½” BSP male or compression Biogas to emergency vent½” BSP female Water flow35mm compression Water return35mm compression Mains electricity1 phase mains electricity Fire alarm signal Outputs out of back of unit Connections

25. Biogas boiler exhaustcondensing boiler inlet and exhaust Natural gas boiler exhaustcondensing boiler inlet and exhaust Biogas boiler condensation drain½” plastic Natural gas boiler condensation drain½” plastic Primary water over pressure vent12mm copper Cabinet air ventilation outlet 4” steel pipe Condensate drain 1 internal¾” BSP female Condensate drain 2 internal¾” BSP female Primary drain point internal12mm compression Secondary drain point internal35mm compression Connections

26. The boiler unit must be installed in a weather proof container or building. Level and securely mounted to the wall of the container or building. Operating temperature between 0°C and 40°C. The exhausts of the boilers must pass through an air tight seal in the wall of the container or building and vent outside at an appropriate position. This position must be away from any window or door or ventilation intake as described in the boiler flue installation instructions. The ventilation fan exhaust must pass through an airtight seal in the wall of the container or building to vent outside to an appropriate place. The boiler condensate drains must discharge to an appropriate drainage point. The blow off vent and the vent should be appropriately piped and located according to SR25 zone 2 safe zone. The boiler cabinet must be appropriately earthed to an earthing rod. The container or building must have appropriate ventilation, to allow the unit to ventilate itself. Installation

27. The boiler unit should be wired into the container or buildings gas and fire alarm. The boiler unit should be wired to the container or buildings electricity supply so that it is also isolated in the event of the container or buildings emergency stop being operated or the electrical supply to the container or building being isolated. The boiler cabinet must not be exposed to water or excessive moisture. The biogas condensate pots must be checked and drained of water daily. Need to check/service the combustion module every 6 months. Installation

28. May you have any questions, please contact: sandra.estevez@southwales.ac.uk alex.chong@southwales.ac.uk Thanks for the attention!