Standard Operation Procedure (SOP) Gas production in small scale anaerobic wetdigestion batch reactors with manual pressure measurement

Transcription

1 Standard Operation Procedure (SOP) Gas production in small scale anaerobic wetdigestion batch reactors with manual pressure measurement : 2 Pages: 5 Author: Lucien Biolley Date: Approved: Valid from: Changed: File: SOP_AnaerobicDigestion_BatchReactorMan_140916

2 1 Application area This description provides a general view over the material and the methods used to determine the gas production of individual liquefied substrates in small scale anaerobic batch reactors. 2 Materials 2.1 Equipment Object Scale Rubber plug (1) Anaerobic digestion flask Screw cap (3) Cannula (inside the rubber plug 1) Multiple-way cock (2) Barometer, digital (5) Swivel (4) Vacuum pump Incubator Magnetic stirrer (optional) Specification Accuracy 10 mg Ø bottom 29 mm, Ø top 35 mm, height 30 mm Glass bottle coated, without lid Soda-Fresh Schweiz AG Screw cap for infusion flask 0.8 x 40 mm, Luer female Luerlock male / Luerlock female Type Leo2 from Keller Druckmesstechnik, Winterthur From Bar, with Swivel connection Male / male, nitrile sealing Water-jet vacuum pump Thermostatic adjustable App. 3cm magnets Figure 1: Equipment for BMP experiment with manual pressure measurement Seite 2 von 5

3 2.2 Consumable Supplies Nitrogen Cellulose powder Water Inoculum Substrates From pressure vessel Artificially manufactured Tab quality From the digester of an existing biogas plant To be defined during the lessons Seite 3 von 5

4 3 Procedure 3.1 Preparation Experimental set-up for substrate digestion tests: A) Inoculum + water self-activity of the inoculum, control B) Inoculum + water + 1g cellulose test for sufficient activity of the inoculum, reference C) Inoculum + Probe + eventually water, depending on the dilution digestion of the substrate sample If B A results in an activity of > 400 standard liters of Gas per kg cellulose, then the activity of the inoculum is sufficient. C - A results in the biogas potential of the substrate. Every sample should be conducted at least in a replication of three Analytical work Depending on the objectives of the experiment several analyses should be conducted. The measurements can be divided in the two groups of application. Hence the measurements for mass balance studies and the measurements for process control. - Mass balance parameter: TS, ots, TOC - Process control parameter: ph, alkalinity, determination of volatile fatty acids, analysis of gas volume and quality Reactor preparation The total volume of the reactor bottles is to be determined. Therefore the bottle is filled with water and weighed. Together with the specific density of water in dependency of the temperature the volume can be calculated. From this the volume of the rubber plug, which takes away some of the space, has to be subtracted (usually 14.5 ml). In order to keep track on the single reactors they have to be labeled if they have not been already Test for sufficient activity of the inoculum To make sure the inoculum in use for the digestion tests is sufficiently active, it has to undergo a separate experiment. The inoculum has to be able to digest 1g of cellulose within 21 days into at least 400 standard liters of Gas per kg cellulose. Seite 4 von 5

5 3.2 Set up a reaction 1. Set temperature for the incubator at 38 C. 2. Check the reactor bottles for cracks and other damages. 3. Fill inoculum, substrate/cellulose and water into the reactors according to the experimental set-up. Shake the bottle gently to prevent clumping. 4. Control the ph-value, recommended values are between 7.5 and (Optional) If using magnetic steering add a magnet. 6. Close the bottle using the rubber plug (with attached cannula) and the screw cap. Use a drop of glycerin on the rubber plug to simplify the procedure and connect the multiple-way cock with Swivel. 7. The reactor flasks are put under vacuum app. 0.7 bar. Close the cock and control the stability of the vacuum (pressure tightness) using the manometer. If the vacuum is stable continue with step 7 otherwise seek and exchange broken parts and restart at step Connect the nitrogen pressure bottle to the reactor and let nitrogen flow with a maximum of 0.5 bar discharge pressure. Open the cock at the reactor and compensate the vacuum inside with nitrogen. 9. The reactor will receive a small over pressure of nitrogen, which will be discharged just by disconnecting the cock from the nitrogen pressure bottle while the cock stays opened. 10. Place the reactors into the incubator. Control temperature and steering/shaking. 11. After 1-2 h the temperature in the reactors will have adjusted so that the cock can be closed now. Any changes of pressure afterwards can be regarded as due to the fermentation process. 12. Measure the pressure on the reactors every day or as often as possible (wear safety goggles!) by connecting the manometer on top of the reactor and opening the cock. Set the manometer to zero before (atmospheric). Also make sure to conduct a fast measurement, so the gas inside the reactor cannot cool down to lose volume. 13. Pressures inside the reactors should not exceed 1 bar over atmospheric due to security reasons. If the measured pressure approaches this value the gas has to be discharged, use these opportunities to measure the gas qualit. 14. Also determine other parameters like the Alkalinity, ph and fatty acids during the experimental period at your own discretion. 15. Discharge the gas left inside after the experiment period, remove the screw lid and the rubber plug (let the cannula remaining inside the rubber plug) and rinse everything with water. Seite 5 von 5