Biogas Flow Rate Research Articles

Simultaneous reduction of NOx and smoke in a dual fuel DI diesel engine

This paper presents the results of an experimental investigation conducted on a compression ignition (CI) engine, modified to run on dual fuel mode, using biogas as a primary fuel and KME (Karanja methyl ester) as a pilot fuel. The biogas was produced by anaerobic digestion of Pongamia pinnata (Karanja) seed cakes. In dual fuel mode, the biogas was inducted at four different flow rates, viz. 0.3kg/h, 0.6kg/h, 0.9kg/h and 1.2kg/h through the intake manifold of the engine. The biogas flow rate of 0.9kg/h gave a better performance and lower emissions, than those of the other flow rates. The NO and smoke emissions were found to be lower by about 34% and 14%, than those of KME operation, at full load. The ignition delay was longer by about 1–2 °CA in the dual fuel operation, than that of KME at full load. The part load performance was found to be better in dual fuel operation, with reduced emissions of NO and smoke, in comparison with KME. The ignition delay at part load in dual fuel operation was also lower than that of KME operation.

Model-based optimization of biogas production in an anaerobic biodegradation process

In this paper we consider a four-dimensional bioreactor model, describing an anaerobic digestion process of wastewater treatment and biogas production. We propose a simple and practically realizable approach for global asymptotic stabilization of the model and for maximizing the biogas flow rate; the latter is achieved by using a numerical extremum seeking algorithm.

Sequential treatment of diluted olive pomace leachate by digestion in a pilot scale UASB reactor and BDD electrochemical oxidation

The efficiency of the anaerobic treatment of olive pomace leachate (OPL) at mesophilic conditions was investigated. Daily and cumulative biogas production was measured during the operational period. The maximum biogas flowrate was 65 L/d, of which 50% was methane. In addition, the applicability of electrochemical oxidation as an advanced post-treatment method for the complete removal of chemical oxygen demand (COD) from the anaerobically treated OPL was evaluated. The diluted OPL, having a pH of 6.5 and a total COD of 5 g/L, was first treated in a 600 L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated for 71 days at mesophilic conditions (32 ± 2 °C) in a temperature-controlled environment at a hydraulic retention time of 3 days, and organic loading rates (OLR) between 0.33 and 1.67 g COD/(L.d). The UASB process led to a COD removal efficiency between 35 and 70%, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 18 A and in the presence of 0.17% NaCl as the supporting electrolyte, complete removal of COD was attained after 7 h of treatment predominantly through total oxidation reactions. During electrochemical experiments, three groups of organo-chlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs) and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, along with the residual chlorine are thought to increase the matrix ecotoxicity to Artemia salina.

Effects of Various Factors on Biogas Purification and Nano-CaCO3 Synthesis in a Membrane Reactor

Reducing CO2 content will significantly improve biogas quality. In this study, a CO2/Ca(OH)2 precipitation reaction was used to purify biogas and prepare CaCO3 nanoparticles simultaneously in a membrane reactor. Results showed that the rate of biogas purification was greater than 99%, and CaCO3 particles were successfully formed in the membrane reactor, which was detected with an average particle size between 300 and 550 nm with chemical additives. Further experiments revealed that the flow rate of biogas, temperature, and different chemical additives showed negligible effects on the biogas purification efficiency, while CaCO3 particle size decreased with the increasing flow rate and increased with the increasing temperature. The average particle sizes of the CaCO3 particles were 334, 537, 437, and 867 nm, corresponding to the addition of EDTA, ZnSO4, Na6O18P6, and the control, respectively. This method was proven to be an effective technique of simultaneously purifying biogas and synthesizing nano-CaCO3.

Study on Power Output Parameter Optimization for Biogas Engine

The optimum spark timing, biogas flow rate and excess air ratio are the important factors influencing the power output performance of ignition’s biogas engine. In this study, the biogas flow rates are set as 220, 240 and 260 L/min, respectively. Under each fixed biogas flow rate, it tests different excess air ratios, ranged from 0.8 to 1.2. The experiment results indicate that the optimal parameters are: spark timing(BTDC13), biogas supply rate(260L/min) and excess air ratio(0.95).

Water Scrubbing for Removal of Hydrogen Sulfide (H<sub>2</sub>S) Inbiogas from Hog Farms

Biogas from anaerobic digestion of biological wastes is a renewable energy resource. H2S in biogas may cause corrosion or other damage to engines if it is not removed from the gas before utilization. Because the solubility of H2S in water is higher than methane, water can be used as an adsorbent to remove H2S from biogas. A simple water scrubbing column to reduce the H2S content was designed in this study. The biogas purification process took place in the scrubbing column with water where the gas was continuously fed from the bottom of the column through the diffuser which could produce bubbles. The biogas bubbles and the water can accelerate the reaction inside the column. The water in the column was circulated by means of a pump. H2S content in raw biogas was about 6000 ppm. First, the efficiencies of H2S removal for different biogas flow rate and water level were conducted at 30 and 90 sec. Second, the efficiencies of H2S removal with water recycling system were induced. The results showed that the concentration of H2S in biogas decreased significantly with water level and increased with biogas flow rate through the water scrubbing. It was an effective technique for removing H2S in a short operation time, but absorption capability of water declined rapidly with time. To maintain high absorption rate, water scrubbing after adsorption needed to be replaced or regenerated. The water scrubbing system is a simplest and cheapest method. This work is investigated the feasibility of water scrubbing system and its application to a small hog farm.

Design of laboratory cyclone separator for biogas purification

This article deals with calculation of a cyclone separator for biogas purification using physical and chemical methods. There is presented a methodology for determination of operating dimensions of the cyclone separator and description of principal features of the cyclone separator model. Calculations have been performed for the diameter of the cylindrical part of cyclone separator 175 mm and for the biogas volume flow rate 6.9∙10−5 m3∙s−1. The calculations can be used in practice for the design of cyclone separator depending on the flow rate of biogas, size of the biogas plants respectively. The developed cyclone separator has been used for the cleaning of biogas in operating conditions at the biogas plant in Kolinany (Slovakia). The presented method of biogas purification has been used for the removing of hydrogen sulphide, particulate matter and carbon dioxide from the raw biogas at the biogas plant. Removal of these undesirable impurities from the biogas is an important step in the production of a fully valued fuel, biomethane.

Thermophilic co-digestion of pig manure and crude glycerol: Process performance and digestate stability

Anaerobic co-digestion has been widely used to enhance biogas production of digesters and, therefore, to improve the anaerobic plants economic feasibility. In the present study, glycerol, a by-product of the biodiesel industry, was used as a co-substrate for pig manure. The results showed that the thermophilic anaerobic co-digestion of pig manure supplemented with 3% of glycerol, on weight basis, was satisfactory. The specific biogas production of the co-digester was 180% higher than the one obtained by the reference digester, which was only fed with pig manure. The improvement was related to the double of the organic loading rate, the high biodegradability of the crude glycerol, the slight reduction of the free ammonia concentration and the optimisation of the carbon-to-nitrogen ratio. Moreover, the analysis of the organic matter (protein, lipids, carbohydrates and fibers) of the influent and the effluent of both digesters together with their biogas flow rates indicated that the microorganisms in the co-digester obtained large amounts of nutrients from the glycerol, whereas the microorganisms of the reference digester mainly produced biogas from the particulate matter. However, the digestate obtained from the co-digester cannot be directly applied as soil fertiliser or conditioner due to the presence of high levels of biodegradable matter, which may exert negative impacts on the plant-soil system. Thus, a longer hydraulic retention time, a reduction of the glycerol concentration and/or a post-treatment is required if the digestate is to be used as soil fertiliser or conditioner. In contrast, pig manure digestate can be directly applied on land.

A study of a pilot-scale biogas bio-filter system for utilization on pig farms

SUMMARYCombustion of biogas containing hydrogen sulphide (H2S) yields highly corrosive sulphur oxides, thereby limiting the use of biogas for heat and power generation. The current study developed and tested a pilot-scale biogas bio-filter system (BBS) to replace conventional water scrubbing systems at a commercial pig farm in Miaoli County, Taiwan. A 62·8-litre pilot-scale BBS, packed with dried aerial roots from the common tree fern (Sphaeropteris lepifera) and a mixture of dried aerial roots and plastic rings as bio-carriers and inoculated with sulphur oxidizing bacteria, was installed at a commercial pig farm. H2S concentration was 5600 mg/m3 and the biogas flow rate was 4 litres/min. The pilot-scale BBS could remove 26·9 g H2S/m3/h using a bio-filter that operated at a 7% (v/v) O2 level continuously for >200 days. It was found that most H2S was oxidized to elemental sulphur (S0) and accumulated on the surface of the dried aerial roots (0·084 g S0/g aerial root) in the BBS. The dried aerial roots and plastic Raschig ring mixture was more efficent at sulphur dioxide removal than the dried aerial roots on their own. The pH and sulphate (SO42−) concentrations of water dropping from the BBS were 1·6 ± 1·0 and 28 680 ± 8253 mg/l, respectively. However, sulphur is the dominant product of sulphur oxidizers at the 7% O2 level. Periodical flushing of the bio-filter with the effluent from the wastewater treatment system on the farm can maintain high efficiency of H2S removal.

Dedicated Observer Scheme for Fault Diagnosis and Isolation in Instruments of an Anaerobic Reactor

This paper proposes a dedicated observer scheme for fault diagnosis and isolation in instruments of an anaerobic reactor. An asymptotic observer is proposed for the estimation of the concentration of Chemical Oxygen Demand (COD), the concentration of anaerobic biomass and the produced biogas flow rate for an anaerobic reactor. The proposed observer is based on the ADM1 for applications in continuous UASB reactors and its main feature is that allows the monitoring of a dynamic balance between anabolic (biological synthesis) and catabolic (methane production) fluxes without biomass measurements in the reactor. Experimental results are shown using the ADM1 for the treatment of wastewater with high organic matter content from a brewery. Validation is carried out using real data obtained from a 2.1 L laboratory scale Up-flow Anaerobic Sludge Blanket (UASB) reactor.

Estimation of Biogas Production from Shrimp Pond Sediment Using the Artificial Intelligence

A biogas production development increases renewable energy and reduces the environmental impact which is caused by carbon dioxide. Thisis important for energy and environmental planning in Thailand. The biogas production by anaerobic digestionproduces methane that can be used as renewable energy. This research was to study biogas production from the anaerobic digestion of shrimp pond sediment by the batch reaction, an estimation of the mathematical model using theArtificial Intelligence (AI) technique and the treatment of shrimp pond sediment.The mass balance principle to create mathematical modeling and decompositions of organic matter into biogas were used to compare the experimental dataincluding, temperature, pH, biogas flow rate and biochemical properties of the shrimp pond sediment. From the results, mathematical models can estimate the dynamic response of the biogas flow rate and factors that affectedthe biogas productions. The treatment of shrimp pond sediment by anaerobic digestion process could reduce TS, TDS, TSS, TVS, BOD, COD and ECby81-89%, 52-60%, 95-99%, 80-89%, 86-95% , 85-95% and 12-22 % respectively.

Pilot-scale chemical–biological system for efficient H2S removal from biogas

A pilot-scale chemical–biological process was performed efficiently to remove corrosive H2S from biogas. Consecutive 356-d livestock biogas purification was conducted at various H2S loading rates. The average inlet H2S concentration was 3542ppm, and a removal efficiency of 95% was achieved with gas retention time of 288s. This system showed robust performance during operation with stable parameters. Purified biogas with an average of 59% CH4 was collected for power production. Moreover, 28.3kWh of power was produced by using a 30kW biogas generator under 300LPM biogas flow rate. During the 30-d shut down test, the jarosite formation resulted in pH decrease and appearance of Leptospirillum sp. and Sulfobacillus sp. in the bioreactor. However, the cell density of the inoculated Acidithiobacillus ferrooxidans was maintained above 5×107CFU/g-AC during long-term operation. Thus, given the successful H2S elimination, the chemical–biological process is a feasible system for biogas purification.

소형 가스엔진 발전기의 배기가스 폐열을 이용한 바이오가스 개질 가능성에 관한 실험적 연구

This study has been carried out the experiment for the possibility of biogas reforming using waste heat. The source of this waste heat is the exhaust gas from a small-sized gas engine generator. For recovering the waste heat, Two-stage heat exchanger is manufactured. The two-stage heat exchanger is composed of a heat exchanger for the exhaust gas and a heat exchanger for the water. This two-stage heat exchanger is used for reforming the biogas by means of on-site hydrogen production at the small-sized gas engine generator. The two-stage heat exchanger is coupled with the biogas reformer which is a kind of catalytic reformer. To confirm a heat recovery efficiency of the two-stage heat exchanger, temperature differences of inlet and outlet locations are measured. Also, the variations of syngas concentrations with various biogas flow rates are investigated. As a result using manufactured two-stage heat exchanger, the biogas can be reformed from waste heat recovery. This experiment suggests that the exhaust gas heat exchanger is available for reforming the biogas.

Application of the IPCC model to a Brazilian landfill: First results

The Intergovernmental Panel on Climate Change gave a methodology to estimate the methane emissions from Municipal Solid Wastes landfills, based on a First Order Decay (FOD) model that assumes biodegradation kinetics depending on the type of wastes. This model can be used to estimate both the National greenhouse gas emissions in the industrialized countries as well as the reductions of these emissions in the developing ones when the Clean Development Mechanism, as defined by the Kyoto Protocol, is implemented. In this paper, the FOD model has been use to evaluate the biogas flow rates emitted by a Brazilian landfill and the results have been compared to the extracted ones: some first results can be useful to evidence the weight of key parameters and do a correct use of the model.

Ammonia removal in anaerobic digestion by biogas stripping: An evaluation of process alternatives using a first order rate model based on experimental findings

The feasibility of biogas stripping to remove ammonia in the anaerobic digestion of source segregated food waste was investigated. It was found in batch experiments that ammonia could be removed from digestate and that the removal followed 1st order kinetics with respect to total ammonia nitrogen concentration. Increasing temperature, biogas flow rate and initial pH all increased removal rates. Using kinetic data gathered in these experiments allowed the integration of ammonia stripping with an anaerobic digestion plant to be modelled for different configurations. Four scenarios were identified: post digestion, in situ, side-stream and pre-digestion ammonia removal relating to where in the process the ammonia stripping was performed. The modelling showed that in situ ammonia removal may be best able to reduce in-digester ammonia concentrations over a wide range of organic loading rates whereas pre-digestion showed most promise in terms of application due to the flexibility to control each part of the process separately. Further experimental work is required into these scenarios to confirm their viability.

Hydrogen Sulfide Removal from Biogas Using Pure and Mixed Cultures of Sulfide-Oxidizing Bacteria Biofiltration

A novel biofiltration system using pure and mixed cultures of sulfide-oxidizing bacteria immobilized on granular activated carbon (GAC) to purify synthetic and real biogas from a sulfate reaction reactor of concentrated latex industry, contaminated by H2S, was studied. Complete H2S removal from synthetic biogas was found in pure and mixed culture reactors at 200 ppm initial H2S concentration, 35 l h−1 of biogas flow rate and 5.83 l h−1 of airflow rate. H2S removal using biofiltration had little effect on the methane content of synthetic biogas. Pure and mixed culture reactors at airflow rates of 0.75–5.83 l h−1 also showed complete H2S removal from real biogas. However, H2S removal efficiency at the airflow rate of 0.53 l h−1 decreased to 99%. Thus, H2S removal using biofiltration had little effect on the methane content of real biogas. The results of this study suggest the feasibility of developing using mixed culture of sulfide-oxidizing bacteria from concentrated latex wastewater for industrial application to remove H2S from biogas through biofiltration.

Increasing Biogas Production from Maize Silage by Ultrasonic Treatment

Maize silage is one of the most commonly used substrates in biogas plants all over Europe today. However, a considerable part of it is not biologically converted into biogas during anaerobic digestion process (AD). This is caused by content of materials unsuitable for AD (e.g. lignin) and substances requiring very long residence time to be decomposed under anaerobic conditions (which would be ineffective from economical point of view). In case of such complex phytomass, the rate-limiting step of AD is hydrolysis of biomacromolecules (mainly polysaccharides). Cavitation induced by ultrasonic treatment of substrate causes increase of particles’ specific area, cell lysis and sonochemical reactions, resulting in splitting of complex organic compounds due to formation of radicals. As a consequence, faster and more efficient conversion of substrate into methane is achieved. To evaluate effect of sonication on biogas production, parallel batch experiments in CSTR bioreactors were carried out. Assessment of substrate disintegration caused by sonication was based on measurements of Chemical oxygen demand (COD) in liquid phase of substrate samples. The biogas and methane CH4 yields were determined by continuous measurement of biogas flow rate and composition. The resulting biogas production enhancement was 13 29.5%, methane yield was increased by 16.9 – 29.5 %. The key evaluation of ultrasonic treatment process is the energy balance. Its results proved its suitability from the environmental point of view.

Empirical modelling and dual-performance optimisation of a hydrogen sulphide removal process for biogas treatment

This study was conducted in order to investigate the use of a simple, low-cost technology for the removal of hydrogen sulphide (H(2)S) from biogas, consisting of an anoxic biotrickling filter. Modelling and optimisation of the process was achieved by studying two independent variables (H(2)S concentration and biogas flowrate) and two simultaneous performance criteria (H(2)S removal efficiency (%) and H(2)S loading rate (g/(m(3) bed day)), which were inversely related. The experiments were carried out on a bioreactor with a 12 L packing volume. H(2)S concentration and biogas flowrate were varied in the range of 2000-4000 ppm(v) and 10-70 L/h, respectively. A model sensitivity analysis indicated the influence of the process variables on the bioreactor performance. Process optimisation was undertaken on a H(2)S removal efficiency basis, while maintaining a target H(2)S loading rate, depending on the desired quality for the biogas use and the technological requirements.

Removal of H2S from Biogas by Iron (Fe3+) Doped MgO on Ceramic Honeycomb Catalyst using Double Packed Columns System

Biogas, a clean environment fuel, is produced by anaerobic digestion of biological wastes. The presence of hydrogen sulfide (H2S) in biogas has a toxic and corrosive to most equipment such as piping, boilers, and powergenerating machine. H2S removal from biogas is of crucial importance to guarantee better performances in biogas exploitation processes, and to reduce environmental impact of gaseous emissions. Iron (Fe 3+ ) doped magnesium oxide (MgO) catalyst was synthesized using sol–gel dip coating process on foam ceramic honeycomb for removal of H2S in biogas. The synthesis catalyst was characterized by XRD and SEM techniques. Double packed columns containing absorption column and catalytic column were used to remove H2S in biogas in this paper. The absorption column using water absorbent was run with counter current mode to absorb H2S from biogas. The synthesized catalyst was packed in catalytic column to continuously degrade the H2S in water absorbent liquid and regenerated by air flow. The results showed that the double packed columns system was effectively performed in H2S removal from biogas. The L/G ratio of 0.6, biogas flow rate of 1 l/min and 10 pieces of catalyst were optimum operating condition of the double packed columns system to get the highest H2S removal efficiency of 72% without any loss of CH4 in the biogas.

Calibration and statistical analysis of a simplified model for the anaerobic digestion of solid waste

Modelling is increasingly used for optimizing environmental treatment processes such as anaerobic digestion. It allows problems such as instability of the process to be solved by predicting various scenarios. The anaerobic digestion model No. 1 (ADM1) is accepted worldwide as the standard model for the description of anaerobic digestion. However, it is sophisticated and complex, so it is not user friendly. Therefore, a mathematical method was developed that allows the calculation of the reactor pH, as well as the biogas flow rate (Q) and composition (expressed as the CO2 partial pressure, pCO2), based on a small number of widely available analyses such as chemical oxygen demand and total organic carbon. Furthermore, the ADM1 model was originally designed for anaerobic digestion of wastewater. In this work, the ADM1 model is evaluated for the first time for application in the modelling of solid waste digestion. This evaluation was performed in two steps. First, a list of experimentally available lab‐scale data (pH and Q) was grouped according to the composition and origin of the treated solid waste (e.g. manure or vegetable waste). For each group the developed model for the calculation of pH, Q and pCO2 was calibrated with this lab‐scale data. After calibration, the model was validated with additional experimental results. It could be demonstrated statistically that the model was able to predict the experimental results, although the confidence region was rather large.