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  • 1.
    Anbalagan, Anbarasan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Influence of light intensity and phosphorous on microalgae activated sludge in phosphate precipitated conditionManuscript (preprint) (Other academic)
  • 2.
    Anbalagan, Anbarasan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Influence of hydraulic retention time on indigenous microalgae and activated sludge process2016In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 91, p. 277-284Article in journal (Refereed)
    Abstract [en]

    Integration of the microalgae and activated sludge (MAAS) process in municipal wastewater treatment and biogas production from recovered MAAS was investigated by studying the hydraulic retention time (HRT) of semi-continuous photo-bioreactors. An average total nitrogen (TN) removal efficiency (RE) of maximum 81.5 ± 5.1 and 64.6 ± 16.2% was achieved at 6 and 4 days HRT. RE of total phosphorous (TP) increased slightly at 6 days (80 ± 12%) HRT and stabilized at 4 days (56 ± 5%) and 2 days (55.5 ± 5.5%) HRT due to the fluctuations in COD and N/P mass ratio of the periodic wastewater. COD and organic carbon were removed efficiently and a rapidly settleable MAAS with a sludge volume index (SVI_10) of less than 117 mL g-1 was observed at all HRTs. The anaerobic digestion of the untreated MAAS showed a higher biogas yield of 349 ± 10 mL g VS-1 with 2 days HRT due to a low solids retention time (SRT). Thermal pretreatment of the MAAS (120 °C, 120 min) did not show any improvement with biogas production at 6 days (269 ± 3 (untreated) and 266 ± 16 (treated) mL gVS-1), 4 days (258 ± 11(untreated) and 263 ± 10 (treated) mL gVS-1) and 2 days (308 ± 19 mL (treated) gVS-1) HRT. Hence, the biogas potential tests showed that the untreated MAAS was a feasible substrate for biogas production. Results from this proof of concept support the application of MAAS in wastewater treatment for Swedish conditions to reduce aeration, precipitation chemicals and CO2 emissions. 

  • 3.
    Anbalagan, Anbarasan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Continuous microalgae-activated sludge flocs for remediation of municipal wastewater under low temperature2017In: / [ed] Peter Van der Steen, 2017, p. 1-8Conference paper (Refereed)
    Abstract [en]

    The operational performance of indigenous microalgae-activated sludge was evaluated regarding the nutrient removal efficiency using raw wastewater collected from Västerås wastewater treatment plant, Sweden at limited artificial surface lighting (290 μmol m-1 sec-1) and Nordic wastewater conditions (13°C). Additionally, the oxygen production and consumption, biomass concentration and its settling was evaluated during the symbiotic algal-bacterial interaction. The results confirmed oxygenic organic compound removal (COD removal of 65-94%) at higher (31-45 d) and lower (13-18 d) sludge retention time (SRT). Also, a complete removal of ammonium throughout the process and partial nitrite-nitrate removal at all SRTs (total nitrogen removal of 41- 62%) were observed. Likewise, a partial phosphorus (P)removal was observed in the effluent which provides an opportunity to capture free P fromthe effluent for recovery as fertiliser. Further, the microalgal growth was slower due to lightor inorganic carbon limitation or ammonium repression caused by higher internal recirculationas observed from ammonium and nitrite-nitrate levels in the PBR. Most importantly, effectivePBR biomass concentration based nutrient removal and relative sludge recirculation have tobe considered in the PBR design to avoid light limitation and activate symbiosis.

  • 4.
    Anbalagan, Anbarasan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Influence of iron precipitated condition and light intensity on microalgae activated sludge based wastewater remediation2017In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, p. 1523-1530Article in journal (Refereed)
    Abstract [en]

    The indigenous microalgae-activated sludge (MAAS) process during remediation of municipal wastewater was investigated by studying the influence of iron flocculation step and light intensity. In addition, availability of total phosphorous (P) and photosynthetic activity was examined in fed-batch and batch mode under northern climatic conditions and limited lighting. This was followed by a semi-continuous operation with 4 d of hydraulic retention time and mean cell residence time of 6.75 d in a photo-bioreactor (PBR) with varying P availability. The fed-batch condition showed that P concentrations of 3–4 mg L−1 were effective for photosynthetic chl. a development in iron flocculated conditions. In the PBR, the oxygen evolution rate increased with increase in the concentration of MAAS (from 258 to 573 mg TSS L−1) at higher surface photosynthetic active radiation (250 and 500 μmol m−2 s−1). Additionally, the rate approached a saturation phase at low MAAS (110 mg L−1) with higher light intensities. Semi-continuous operation with luxury P uptake and effective P condition showed stable average total nitrogen removal of 88 and 92% respectively, with residual concentrations of 3.77 and 2.21 mg L−1. The corresponding average P removal was 68 and 59% with residual concentrations of 2.32 and 1.75 mg L−1. The semi-continuous operation produced a rapidly settleable MAAS under iron flocculated condition with a settling velocity of 92–106 m h−1 and sludge volume index of 31–43 ml g−1 in the studied cases.

  • 5.
    Bhutani, Naveen
    et al.
    ABB Corporate Research Center, Bangalore, India .
    Lindberg, Carl-Fredrik
    ABB AB Corporate Research, Sweden .
    Starr, Kevin
    ABB Process Automation Services, United States.
    Horton, Robert
    ABB Process Automation Services, United States.
    Energy assessment of Paper Machines2012In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 14, p. 955-963Article in journal (Refereed)
    Abstract [en]

    There is a large value in making Pulp and Paper mills more energy efficient. ABB has developed an energy assessment service where opportunities to save energy in the paper machine are identified. The energy assessment is done by quantifying energy flows, benchmarking energy users, data mining and steam sensitivity analysis and by experiments and additional measurements at the paper machine. Energy quantification helped in identifying main energy consumer, benchmarking was useful to assess the gap between operating performance and best performance whereas data mining and steam sensitivity analysis helped in studying the impact of key operating variables on performance of paper machines. After the assessment an action plan was presented to the mill for energy efficiency improvement together with a return on investment.

  • 6.
    Hermansson, K.
    et al.
    Sigholm Konsult, Västerås, Sweden.
    Kos, C.
    Flowocean AB, Västerås, Sweden.
    Starfelt, F.
    Vattenfall AB, Uppsala, Sweden.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Corporate Research, Västerås, Sweden.
    Zimmerman, Nathan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    An Automated Approach to Building and Simulating Dynamic District Heating Networks2018In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 51, no 2, p. 855-860Article in journal (Refereed)
    Abstract [en]

    In Nordic countries, district heating accounts for a large share of the consumers’  heat demand. In Sweden, roughly 50% of the total heat demand is attributed to district heating. Which, over the past few years, is equivalent to around 50 TWh, and imposes a difficult balance between supply and demand for the suppliers of district heating. For large networks the propagation of heat from supplier to end-user can vary several hours. Further complexities of large networks, which can consist of multiple overlapping rings, is that during transient conditions the flow can actually change direction. A dynamic modeling library has been developed in Modelica using OpenModelica for district heating networks. Methods for modeling, handling data, simulating and the visualization of results has been developed using Matlab. The model has been validated using data from Mälarenergi  AB, a local provider of district heating in Västerås, Sweden. The model provides to an acceptable degree in predicting the heat propagation and temperature distribution in a localized case study. Adding a higher level of robustness, the model has the capacity to handle bi-directional and reversing flows in complex ring structures. Through this work, the combination of OpenModelica and Matlab, a framework for automating the building and simulation of district heating networks is obtainable. The implications of automating network modeling from computer-aided design drawings allows for a quick robust overview of how the network is working and how prospective additions to the network could impact the end-users. Furthermore, incorporating visual aspects for heat propagation in a network contributes to a higher understanding of complex network structures. 

  • 7.
    Lindberg, Carl-Fredrik
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Corporate Research, Sweden.
    Bhutani, Naveen
    ABB Corporate Research, Bangalore, India.
    Starr, Kevin
    ABB Inc., Westerville, OH, USA.
    Horton, Robert
    ABB Inc., Westerville, OH, USA.
    Energy Conservation in Industry: Steam Energy Fingerprint of Paper Machine2015In: Handbook of Clean Energy Systems / [ed] Jinyue Yan, Chichester, West Sussex, UK: John Wiley & Sons, 2015, p. 2175-2181Chapter in book (Refereed)
    Abstract [en]

    There is a large value in making the industry more energy efficient. The benefit is not only energy savings and reduction of CO2 emissions, the industry also becomes more competitive due to lower costs for energy, and often also improved production rate and product quality due to positive side effects when processes are made more efficient. Several factors influence efficiency, the most important ones are presented, as well as advices for an assessment and actions for improvements.

    As an example a steam energy fingerprint of a paper machine is given. In the assessment energy flows are quantified, energy users in the paper machine are benchmarked and actions for improving efficiency are suggested.

  • 8.
    Lindberg, Carl-Fredrik
    et al.
    ABB Corporate Research Västerås, Sweden.
    Bhuthani, Naveen
    ABB Corporate Research Bangalore, India.
    Starr, Kevin
    ABB Process Automation Services Westerville, OH, United States.
    Horton, Robert
    ABB Optimization Service Atlanta, GA, United States.
    Conservation of energy: A paper machine fingerprint cuts energy usage2013In: ABB review, ISSN 1013-3119, no 1, p. 58-63Article in journal (Other academic)
    Abstract [en]

    Entering the papermaking machine, the raw material that goes into a single A4 sheet of paper would look like a bucket of slightly dirty water. In fact, the stock furnished to a paper machine contains over 99 percent water and less than 1 percent actual paper fiber. Although most of the dewatering in papermaking is performed mechanically, a significant amount is done thermally – resulting in colossal energy usage and making paper production one of the most energy-hungry processes in industry. But where such large consumptions are in play, there also exist opportunities for significant savings. This is why ABB offers a paper machine energy fingerprint. This assessment quantifies energy flows and benchmarks energy use in the paper machine, enabling energy-saving opportunities to be identified.

  • 9.
    Lindberg, Carl-Fredrik
    et al.
    ABB Corporate Research, Sweden.
    Isaksson, Alf
    ABB Corporate Research, Sweden.
    Comparison of different sampling schemes for wireless control subject to packet losses2015In: First International Conference on Event-Based Control, Communication, and Signal Processing, 2015Conference paper (Refereed)
    Abstract [en]

    Three different approaches to reduce the amount of communication in wireless control subject to packet losses have been evaluated in an extensive simulation study. The sampling approaches are: slow periodic, event-based and self-triggered sampling. They are ranked based on their integrated absolute error (IAE) control performance and also compared with fast periodic sampling. The three approaches have surprisingly equal control performance in the nominal case (without packet losses) for a wide range of test scenarios (process models, controller tunings etc.). With packet losses the importance of re-transmissions becomes evident.

  • 10.
    Lindberg, Carl-Fredrik
    et al.
    ABB Corporate Research, Sweden.
    Starr, Kevin
    ABB Process Automation Services, US.
    Horton, Robert
    ABB Process Automation Services, US.
    Bhuthani, Naveen
    ABB Corporate Research Center, India.
    Paper Machine Energy Fingerprint2010In: Control Systems 2010, 2010, p. 208-213Conference paper (Refereed)
    Abstract [en]

    There is a large value in making the Pulp & Paper mills more energy efficient. ABB has developed an energy assessment service where opportunities to save energy in the paper machine are identified.

    The assessment is done by both quantifying energy flows and benchmarking energy users in the paper machine. After the assessment is done an action plan is presented to the mill of what could be done to improve energy efficiency together with a return on investment.

  • 11.
    Lindberg, Carl-Fredrik
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Corp Res, Västerås, Sweden..
    Tan, SieTing
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Univ Teknol Malaysia, Johor, Malaysia.
    Yan, JinYue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Starfelt, Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. MälarEnergi, Västerås, Sweden.
    Key performance indicators improve industrial performance2015In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 75, p. 1785-1790Article in journal (Refereed)
    Abstract [en]

    Key Performance Indicators (KPIs) are important for monitoring the performance in the industry. They can be used to identify poor performance and the improvement potential. KPIs can be defined for individual equipment, sub-processes, and whole plants. Different types of performances can be measured by KPIs, for example energy, raw-material, control & operation, maintenance, etc. Benchmarking KPIs with KPIs from similar equipment and plants is one method of identifying poor performing areas and estimating improvement potential. Actions for performance improvements can then be developed, prioritized and implemented based on the KPIs and the benchmarking results. An alternative to benchmarking, which is described in this paper, is to identify the process signals that are strongest correlated with the KPI and then change these process signals in the direction that improves the KPI. This method has been applied to data from a combined heat and power plant and a suggestion are given on how to improve boiler efficiency. 

  • 12.
    Lindberg, Carl-Fredrik
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zahedian, Kourosh
    ABB AB, Västerås, Sweden.
    Solgi, Maryam
    ABB AB, Västerås, Sweden.
    Lindkvist, Rickard
    ABB AB, Västerås, Sweden.
    Potential and limitations for industrial demand side management2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 61, p. 415-418Article in journal (Refereed)
    Abstract [en]

    The growing share of variable renewable power such as wind and solar photovoltaic (PV) emphasize the importance of demand side management. In a couple of years consumers have to adapt their consumption more to available generated power in order to maintain grid stability and to reduce their electricity costs. In this study the potential and limitations for demand side management in about 15 different companies in Sweden has been investigated. A brief description of some of the company’s production process is given, with focus on electrical consumption. Suggestions on different demand side management possibilities are presented as well as limitations. The suggestions are given for different time horizons, from load shifting between hours, to weeks and years. Potential savings achieved with demand side management have also been evaluated based on historical electricity prices from different countries.

  • 13.
    Schwede, Sebastian
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anbalagan, Anbarasan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Krustok, Ivo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB Corporate Research, Västerås, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Evaluation of the microalgae-based activated sludge (MAAS) process for municipal wastewater treatment on pilot scale2016Conference paper (Refereed)
    Abstract [en]

    The microalgae-based activated sludge (MAAS) process was evaluated regarding the removal efficiency of organic matter and nitrogen from physiochemically pretreated municipal wastewater at different hydraulic retention time (HRT) on pilot scale. Additionally, the interplay between the algal and bacterial consortium was evaluated regarding the ability of the algal consortium to provide oxygen for bacterial oxidation processes. The results showed in general high organic matter (COD removal 75-90%) and total nitrogen (40-50%) removal at all HRTs (6, 4 and 2 days). The dissolved oxygen (DO) concentration was maintained stable at 6 days (6.04±0.47 mg L-1) and 4 days (4.24±0.62 mg L-1) HRT. However, the DO significantly declined at 2 days HRT due to loss of biomass at the high influent flow in the sedimentation unit. Nevertheless, the MAAS process functioned as a symbiotic algal-bacterial system with bacterial organic matter oxidation and nitrification and algal nutrient removal.

  • 14.
    Tiberi, Ubaldo
    et al.
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Lindberg, Carl-Fredrik
    ABB Corporate Research, Västerås, Sweden.
    Isaksson, Alf J.
    ABB Corporate Research, Västerås, Sweden.
    Dead-band self-triggered PI control for processes with dead-time2012In: 2nd IFAC Conference on Advances in PID Control, 2012: Location: University of Brescia, Brescia, Italy / [ed] Vilanova, Ramon, Visioli, Antonio, 2012, p. 442-447Conference paper (Refereed)
    Abstract [en]

    Current implementations of digital controllers assume that sensing, control and actuationare performed in a periodic fashion. In classic control schemes, where sensors and controllers aredirectly connected, periodicity does not provide particular drawbacks, but, in the case of wireless sensornetworks, such a choice may be questionable. One of the driving constraints in the design of wirelesssensor networks is represented by its energy efficiency, and it has been shown that the main cause ofenergy consumption is due to the radio activities of the sensor nodes. By using periodic implementations,the sensor nodes are enforced to keep on transmitting measurements to the controller even if it is notreally needed, thus wasting energy. To cope with these problems, self-triggered control was recentlyintroduced. This technique aims at reducing the conservativeness of periodic implementations providingan adaption of the inter-sampling intervals based on the current output of the system. Existing workon self-triggered control considers linear systems controlled by state feedback controllers under theassumption of small time-delays. In this paper the problem of designing a self-triggered control schemethat applies to first-order processes with large dead-times controlled by PI controllers is addressed.Moreover, the proposed self-triggered scheme is robust with respect to set-point changes and externaldisturbances, which are typical in process industry. The results are validated by simulations.

  • 15.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Force Measurement, Västerås, Sweden.
    Achieving lower district heating network temperatures using feed-forward MPC2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 15, article id 2465Article in journal (Refereed)
    Abstract [en]

    The focus of this work is to present the feasibility of lowering the supply and return temperatures of district heating networks in order to achieve energy savings through the implementation of feed-forward model predictive control. The current level of district heating technology dictates a need for higher supply temperatures, which is not the case when considering the future outlook. In part, this can be attributed to the fact that current networks are being controlled by operator experience and outdoor temperatures. The prospects of reducing network temperatures can be evaluated by developing a dynamic model of the process which can then be used for control purposes. Two scenarios are presented in this work, to not only evaluate a controller's performance in supplying lower network temperatures, but to also assess the boundaries of the return temperature. In Scenario 1, the historical load is used as a feed-forward signal to the controller, and in Scenario 2, a load prediction model is used as the feed-forward signal. The findings for both scenarios suggest that the new control approach can lead to a load reduction of 12.5% and 13.7% respectively for the heat being supplied to the network. With the inclusion of predictions with increased accuracy on end-user demand and feed-back, the return temperature values can be better sustained, and can lead to a decrease in supply temperatures and an increase in energy savings on the production side.

  • 16.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Corporate Research .
    Agglomeration Detection in Circulating Fluidized Bed Boilers Using Refuse Derived Fuels2016In: 2016 9th EUROSIM Congress on Modelling and Simulation, IEEE Computer Society, 2016, p. 123-128Conference paper (Refereed)
    Abstract [en]

    The formation of agglomerates in a refuse derived fuel (RDF) fired circulating fluidized bed (CFB) boiler has been investigated by implementing a dynamic model of the combustion process. The nature of refuse derived fuel, which is complex in composition, leads to an increased tendency for agglomerate formation. Notwithstanding the fact that a robust control scheme is essential in preventing the decrease in boiler efficiency from accelerated agglomerate formation. Therefore, a mechanism for detecting agglomeration through a physical model by looking at the minimum fluidization is presented. As agglomerates form between the fuel ash and bed sand the average diameter of the sand will increase and therefore the minimum fluidization velocity. Samples of bed material have been sieved and measured from a 150MW circulating fluidized bed boiler fired with refuse derived fuel to determine bed material size distribution. The findings have been correlated and match an increase in the minimum fluidization velocity during a seven day sampling period where the bed material size distribution increases above the average sand diameter.

  • 17.
    Zimmerman, Nathan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB Force Measurement, Västerås, Sweden.
    Waste fuel combustion: Dynamic modeling and control2018In: Processes, ISSN 2227-9717, Vol. 6, no 11, article id 222Article in journal (Refereed)
    Abstract [en]

    The focus of this study is to present the adherent transients that accompany the combustion of waste derived fuels. This is accomplished, in large, by developing a dynamic model of the process, which can then be used for control purposes. Traditional control measures typically applied in the heat and power industry, i.e., PI (proportional-integral) controllers, might not be robust enough to handle the the accompanied transients associated with new fuels. Therefore, model predictive control is introduced as a means to achieve better combustion stability under transient conditions. The transient behavior of refuse derived fuel is addressed by developing a dynamic modeling library. Within the library, there are two models. The first is for assessing the performance of the heat exchangers to provide operational assistance for maintenance scheduling. The second model is of a circulating fluidized bed block, which includes combustion and steam (thermal) networks. The library has been validated using data from a 160 MW industrial installation located in Västerås, Sweden. The model can predict, with satisfactory accuracy, the boiler bed and riser temperatures, live steam temperature, and boiler load. This has been achieved by using process sensors for the feed-in streams. Based on this model three different control schemes are presented: a PI control scheme, model predictive control with feedforward, and model predictive control without feedforward. The model predictive control with feedforward has proven to give the best performance as it can maintain stable temperature profiles throughout the process when a measured disturbance is initiated. Furthermore, the implemented control incorporates the introduction of a soft-sensor for measuring the minimum fluidization velocity to maintain a consistent level of fluidization in the boiler for deterring bed material agglomeration.

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