BIOCONSERVACION S.A.U.– C/ Vapor 12. P.I. El Regàs 08850 Gavà (Barcelona), Spain
Tel: +34 93 662 32 54 | info@bioconservacion.com
Biogas is a mixture of gases, the main components of which are methane and carbon dioxide, produced as a result of the fermentation of organic matter in the absence of air by the action of a microbial consortium (anaerobic digestion). The composition of the biogas depends entirely on the nature of the waste used and the conditions under which anaerobic digestion is carried out. Generally, the biogas is used for energy recovery, which is determined by the methane concentration. However, a purification of certain contaminants with abrasive and corrosive character, such as siloxanes and H2S, is necessary to ensure a correct operation of the cogeneration engines. The Mapocho-Trebal wastewater treatment plant (WWTP), located in Santiago de Chile, treats 30% of the town's water and is a benchmark facility. The facility uses biogas energy by means of three cogeneration engines, each with a power of 1,000 kW. Normally two of these are in operation, while the third is reserved for maintenance stops. The strict legislation of the trans-Andean country regarding emissions of volatile organic compounds (VOCs) and nitrogen oxides, and the need to obtain an effluent free of mainly siloxanes and H2S for a correct use of the purified biogas, led those responsible for the WWTP to contact BION. Our technical department studied the case in depth and proposed to implement a competitive alternative both in economic and technical terms. Plant data The biogas purification system consists of two parallel analogous lines composed of three filters in series. Biogas flow rate: 3600 m3/h. H2S concentration: H2S concentrations, due to biogas pre-treatment, range from 40 to 60 ppmv. In specific cases where the pre-treatment does not work properly, peaks of up to 500 ppmv have been measured. The objective is to reduce these values to concentrations below 1 ppmv. Siloxanes: An exhaustive characterization of the siloxanes present in the biogas stream revealed significant concentrations of cyclic siloxanes type D3, D4 and D5 among others. Values of up to 10 mg/m3 were measured for the D5 type. Others: in addition to the compounds, significant concentrations of mercaptans, cycloalkanes, chlorinated compounds and aromatic hydrocarbons were measured. Solution After a thorough characterization of the biogas to be treated and an assessment of the working conditions, the solution proposed by BION was as follows: High quality Active Carbon for the removal of high molecular weight VOCs and siloxanes. High quality Bion KOH to improve the removal of H2S, certain VOCs and mercaptans. The solution proposed by BIOCONSERVACION was successful, generating biogas with H2S levels below 1 ppm. BION's collaboration continues once the solution has been implemented and the results have been verified, since it has the possibility of carrying out an analysis of the condition of the socks prior to their replacement. By evaluating the remaining capacity of the media, it is able to optimize the process to achieve maximum utilization of the potential of each installation.
READ MORE »Bioconservacion's technology was the successful bidder in the public tender launched in 2015 for the design, execution and construction of a biogas desulfurization unit at the wastewater treatment plant in Chania, Greece. With a population of more than 100,000, Chania is the second largest municipality on the Greek island of Crete. Its wastewater treatment plant consists of primary and secondary clarifiers, two biological reactors and four anaerobic digesters to produce biogas. This wastewater treatment plant has been designed to optimize energy integration by using the combustion of the biogas produced in a cogeneration engine (heat and electricity). The heat produced by the engine is used both to preheat the sludge in the digesters and to dry the output digestate. These measures ensure maximum energy efficiency, but require adequate purification of the biogas to protect the internal combustion engines. Specifically, the concentration of H2S needs to be reduced from 2000 ppm to practically zero to protect the metal parts from corrosion, and thus maximize the lifetime of the engine. The solution designed by BION was proposed in collaboration with the Greek engineering firm DIMTECH and was chosen by the management of the Chania WWTP due to its advantages over other biogas desulfurization equipment currently available, in particular: Very high H2S adsorption capacity: 45% by weight (10 cycles). Extremely low pressure drop through the fixed beds. Excellent performance even in the absence of O2. Moderate amounts of volatile organic compounds and CO2 do not affect the optimal performance of the product. Easily regenerated up to 10 times by simply circulating ambient air through the beds. Extremely low maintenance requirements. The unit consists of two fixed beds mounted in parallel and configured to work with the highly efficient BION Sigma filter media in a completely autonomous and safe way. A machine PLC integrated in the control cabinets, which handles more than 30 input/output control signals, allows fully automatic operation in all working modes (operation, inerting, regeneration and stop/bypass). Setpoint input is done from a 10" touch screen and supervision can also be done remotely, from a PC in the office or even thousands of miles away, thanks to an Internet port built into the PLC. This feature was widely used by Bioconservacion engineers during the evaluation period. The plant started operations from 2016 and the performance evaluation tests lasted 6 months. At the end of this time, a delegation of BION technical staff performed the final commissioning and the plant was officially commissioned and successfully handed over to the customer. With the same technology and commissioning method, excellent results can be obtained in any application requiring biogas purification (landfill biogas combustion and/or anaerobic digestion, cogeneration, biogas concentration and bio-methane injection into the grid), guaranteeing the final performance of the system.
READ MORE »Desulfurization and reduction of siloxanes in biogas. Case Study: MCFC Project at CETAGUA (Mataró - Spain) Reducing the carbon footprint of our society is essential. This can be achieved by capturing and confining anthropogenic CO2 emissions, as well as by replacing fossil fuels with renewable fuels. MCFCs (Molten Carbonate Fuel Cells) are the only ones capable of doing both. Thanks to their principle of operation, CO2 can be extracted from a gas stream on the cathode side and fuels such as biogas can be converted into electricity on the anode side. However, the degradation caused by the pollutants present in these gases must be addressed. In this sense the project "MCFC catalyst and stack component degradation and lifetime: Fuel Gas Contaminant effects and Extraction strategies" aims to tackle this problem from two sides: 1) the investigation of the mechanisms of poisoning caused by fuels and to determine precisely the MCFC tolerance limits for long-term endurance; 2) optimization of fuel and gas cleaning to achieve adapted degrees of purification according to the operating conditions and MCFC tolerance. CETaqua (Centro Tecnológico del Agua), a company belonging to the Suez group was involved in the project, where one of its main objectives was to test on a pilot scale, alternative adsorbent materials to activated carbons that were being conventionally used in most wastewater treatment plants (WWTP). Fig 1: Biogas purification system located at the Mataró WWTP. To this end, CETaqua contacted BION and a biogas purification project was carried out at the Mataró wastewater treatment plant (Barcelona), a project that was carried out in a two-stage system. The system consists of two identical lines composed of a first vessel filled with 3 mm BION SIGMA (formerly BION Fe) to remove H2S and a second step with a vessel filled with 4 mm BION AC for VOCs and extraction siloxanes (Figure 1). The tests last about half a year and the results were evaluated at a rate of 10Nm3 / h, and the contaminant concentrations were in a range between 700-2000 ppmv and 4-5 mg/m3 for H2S and siloxanes, respectively. Project results In reference to H2S removal, the average results are summarized in Figure 2. As can be seen, H2S was successfully removed in both lines and only during certain episodes, where peaks were measured, significant amounts of H2S were detected at the outlet of the first stage, but always maintaining removal efficiency values of more than 95% (Figures 2). Either way, the second vessel filled with BION AC, not only removes siloxanes and VOCs, but acted as a polishing stage that resulted in negligible H2S concentrations after the overall purification system. Figure 3 clearly shows that BION SIGMA was depleted, as both colors can be distinguished before and after use. Figure 3. DS B filled with BION SIGMA (a b). BION SIGMA in DS B (c). DS A filled with BION SIGMA (d). BION SIGMA in DS B (top). As for siloxanes, BION AC achieves removal efficiency values of about 30%, a value that might seem low, but there is a wide variety of siloxanes and not all of them are effectively removed with the same carbon quality. Therefore, depending on the siloxane to be removed, we could suggest one or another type of carbon. Taking into account that no characterization of siloxanes had been done before, the results obtained must be considered satisfactory. In summary, biogas purification system was successfully carried out and the biogas could be employed in fuel cells.
READ MORE »Bioconservacion, together with the Greek engineering company DIMTECH, is carrying out a biogas desulfurization project that aims to promote the use of energy from sludge digestion at the Chania WWTP, a wastewater treatment plant in a semi-arid area of the island of Crete, located near residential areas. The plant will be commissioned soon and will use BION Fe filter media as the active material for the main biogas desulfurization equipment. For biogas desulfurization, the Chania WWTP managers carried out a screening of the different alternatives available on the market and finally contacted Bioconservacion. The good results obtained in other similar facilities in countries such as Portugal or England with BION-Fe, led the WWTP managers to choose Bioconservacion. There are many advantages to working with BION-Fe, both technically and economically, including the following: High H2S adsorption capacity: 45% by weight (in 10 cycles). Low load loss in the equipment due to its pelletized format compared to other media such as iron filings or granular materials. No minimum O2 level required. Moderate amounts of volatile organic compounds and CO2 do not affect the optimum performance of the product. Easy regeneration with ambient air. Thus, Bioconservacion/DIMTECH made a proposal for a biogas treatment system using two parallel lines with two fiberglass reactors with a capacity of 4,500 kg of BION Fe. This configuration allows biogas purification without the need to interrupt the process at any time, achieving the maximum possible energy utilization. In order to guarantee the results, an exhaustive monitoring of the results of the purification system will be carried out during the first 5 cycles of operation. After 6 months, an in-situ check of the efficiency of the treatment and an overall evaluation of the process and its optimization, if necessary, will be carried out. A close collaboration between all the participating companies makes possible the exchange of information and an exhaustive follow-up of results, thus assuring an excellent advice and an agile resolution of incidences in case of occurrence.
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