scholarly journals Model-Based Analysis of Feedback Control Strategies in Aerobic Biotrickling Filters for Biogas Desulfurization

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 208
Author(s):  
Luis Rafael López ◽  
Mabel Mora ◽  
Caroline Van der Heyden ◽  
Juan Antonio Baeza ◽  
Eveline Volcke ◽  
...  
Keyword(s):  
Closed Loop ◽  
Control Strategies ◽  
Biotrickling Filter ◽  
Process Performance ◽  
Control Loops ◽  
Biotrickling Filters ◽  
Model Based ◽  
Outlet Concentration ◽  
The Impact ◽  
Model Based Analysis

Biotrickling filters are one of the most widely used biological technologies to perform biogas desulfurization. Their industrial application has been hampered due to the difficulty to achieve a robust and reliable operation of this bioreactor. Specifically, biotrickling filters process performance is affected mostly by fluctuations in the hydrogen sulfide (H2S) loading rate due to changes in the gas inlet concentration or in the volumetric gas flowrate. The process can be controlled by means of the regulation of the air flowrate (AFR) to control the oxygen (O2) gas outlet concentration ([O2]out) and the trickling liquid velocity (TLV) to control the H2S gas outlet concentration ([H2S]out). In this work, efforts were placed towards the understanding and development of control strategies in biological H2S removal in a biotrickling filter under aerobic conditions. Classical proportional and proportional-integral feedback controllers were applied in a model of an aerobic biotrickling filter for biogas desulfurization. Two different control loops were studied: (i) AFR Closed-Loop based on AFR regulation to control the [O2]out, and (ii) TLV Closed-Loop based on TLV regulation to control the [H2S]out. AFR regulation span was limited to values so that corresponds to biogas dilution factors that would give a biogas mixture with a minimum methane content in air, far from those values required to obtain an explosive mixture. A minimum TLV of 5.9 m h−1 was applied to provide the nutrients and moisture to the packed bed and a maximum TLV of 28.3 m h−1 was set to prevent biotrickling filter (BTF) flooding. Control loops were evaluated with a stepwise increase from 2000 ppmv until 6000 ppmv and with changes in the biogas flowrate using stepwise increments from 61.5 L h−1 (EBRT = 118 s) to 184.5 L h−1 (EBRT = 48.4 s). Controller parameters were determined based on time-integral criteria and simple criteria such as stability and oscillatory controller response. Before implementing the control strategies, two different mass transfer correlations were evaluated to study the effect of the manipulable variables. Open-loop behavior was also studied to determine the impact of control strategies on process performance variables such as removal efficiency, sulfate and sulfur selectivity, and oxygen consumption. AFR regulation efficiently controlled [O2]out; however, the impact on process performance parameters was not as great as when TLV was regulated to control [H2S]out. This model-based analysis provided valuable information about the controllability limits of each strategy and the impact that each strategy can have on the process performance.

The impact of global change on the hydropower potential of Europe: a model-based analysis

Energy Policy ◽  
2005 ◽  
Vol 33 (7) ◽  
pp. 839-855 ◽  
Author(s):  
Bernhard Lehner ◽  
Gregor Czisch ◽  
Sara Vassolo
Keyword(s):  
Global Change ◽  
Model Based ◽  
Hydropower Potential ◽  
The Impact ◽  
Model Based Analysis

Model-based evaluation of mechanisms and benefits of mainstream shortcut nitrogen removal processes

2015 ◽  
Vol 71 (6) ◽  
pp. 840-847 ◽  
Author(s):  
Ahmed Al-Omari ◽  
Bernhard Wett ◽  
Ingmar Nopens ◽  
Haydee De Clippeleir ◽  
Mofei Han ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Control Strategies ◽  
Model Based ◽  
Main Challenge ◽  
Nitrite Oxidizing Bacteria ◽  
Shortcut Nitrogen Removal ◽  
Target Ratio ◽  
Removal Processes ◽  
Selection Mechanisms ◽  
The Impact

The main challenge in implementing shortcut nitrogen removal processes for mainstream wastewater treatment is the out-selection of nitrite oxidizing bacteria (NOB) to limit nitrate production. A model-based approach was utilized to simulate the impact of individual features of process control strategies to achieve NO−2-N shunt via NOB out-selection. Simulations were conducted using a two-step nitrogen removal model from the literature. Nitrogen shortcut removal processes from two case studies were modeled to illustrate the contribution of NOB out-selection mechanisms. The paper highlights a comparison between two control schemes; one was based on online measured ammonia and the other was based on a target ratio of 1 for ammonia vs. NOx (nitrate + nitrite) (AVN). Results indicated that the AVN controller possesses unique features to nitrify only that amount of nitrogen that can be denitrified, which promotes better management of incoming organics and bicarbonate for a more efficient NOB out-selection. Finally, the model was used in a scenario analysis, simulating hypothetical optimized performance of the pilot process. An estimated potential saving of 60% in carbon addition for nitrogen removal by implementing full-scale mainstream deammonification was predicted.

scholarly journals INVESTIGATION OF LOCAL AND MODAL BASED ACTIVE VIBRATION CONTROL STRATEGIES ON THE EXAMPLE OF AN ELASTIC SYSTEM

2019 ◽  
Vol 19 (2) ◽  
pp. 32-45 ◽  
Author(s):  
Christoph PEUKERT ◽  
Patrick PÖHLMANN ◽  
Marcel MERX ◽  
Steffen IHLENFELDT ◽  
Jens MÜLLER
Keyword(s):  
Vibration Control ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Elastic System ◽  
Control Strategies ◽  
Active Vibration Control ◽  
Modal Control ◽  
Control Approach ◽  
Control Loops ◽  
The Impact

Nowadays, feed axes are often equipped with multiple parallel-acting actuators in order to increase the dynamics of the machine tool. Also, additional actuators for active damping are widely used. Normally, the drives or actuators are controlled independently without consideration for the impact on each other. In contrast, by using the modal space control, the system can be decoupled and the modal control loops can be adjusted independently. This control approach is particularly suitable for motion systems, such as machine tools, which have more drives or actuators than degrees of freedom of movement. This paper deals with the pre-investigation of the modal-based vibration control for machine tools with additional actuators. The object of investigation is an elastic system with a movable saddle. The modal-based control is compared with a local control approach. The results obtained experimentally on the test rig are presented. The modal control is superior since, with the modal approach, each control loop corresponds to a specific vibration mode, and the control law for this loop is designed to provide the desired performance of the control system at the corresponding resonance frequency. The parameterisation of the control loops is simplified by modal control, since the modes can be controlled independently.

scholarly journals Estimation of the economic burden of COVID-19 using disability-adjusted life years (DALYs) and productivity losses in Kerala, India: a model-based analysis

BMJ Open ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. e049619
Author(s):  
Denny John ◽  
M S Narassima ◽  
Jaideep Menon ◽  
Jammy Guru Rajesh ◽  
Amitava Banerjee
Keyword(s):  
Economic Burden ◽  
Premature Mortality ◽  
Secondary Outcome ◽  
Years Of Life Lost ◽  
Disability Adjusted Life Years ◽  
Model Based ◽  
Disability Adjusted Life ◽  
Life Years ◽  
The Impact ◽  
Model Based Analysis

ObjectivesFrom the beginning of the COVID-19 pandemic, clinical practice and research globally have centred on the prevention of transmission and treatment of the disease. The pandemic has had a huge impact on the economy and stressed healthcare systems worldwide. The present study estimates disability-adjusted life years (DALYs), years of potential productive life lost (YPPLL) and cost of productivity lost (CPL) due to premature mortality and absenteeism secondary to COVID-19 in the state of Kerala, India.SettingDetails on sociodemographics, incidence, death, quarantine, recovery time, etc were derived from public sources and the Collective for Open Data Distribution-Keralam. The working proportion for 5-year age–gender cohorts and the corresponding life expectancy were obtained from the 2011 Census of India.Primary and secondary outcome measuresThe impact of the disease was computed through model-based analysis on various age–gender cohorts. Sensitivity analysis was conducted by adjusting six variables across 21 scenarios. We present two estimates, one until 15 November 2020 and later updated to 10 June 2021.ResultsSeverity of infection and mortality were higher among the older cohorts, with men being more susceptible than women in most subgroups. DALYs for males and females were 15 954.5 and 8638.4 until 15 November 2020, and 83 853.0 and 56 628.3 until 10 June 2021. The corresponding YPPLL were 1323.57 and 612.31 until 15 November 2020, and 6993.04 and 3811.57 until 10 June 2021, and the CPL (premature mortality) were 263 780 579.94 and 41 836 001.82 until 15 November 2020, and 1 419 557 903.76 and 278 275 495.29 until 10 June 2021.ConclusionsMost of the COVID-19 burden was contributed by years of life lost. Losses due to YPPLL were reduced as the impact of COVID-19 infection was lesser among the productive cohorts. The CPL values for individuals aged 40–49 years old were the highest. These estimates provide the data necessary for policymakers to work on reducing the economic burden of COVID-19 in Kerala.

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