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Willebroek, Belgium

De Greef J.,Keppel Seghers Belgium NV | De Proft R.,Keppel Seghers Belgium NV | Villani K.,Keppel Seghers Belgium NV | Lopez M.A.,Keppel Seghers
18th Annual North American Waste-to-Energy Conference, NAWTEC18 | Year: 2010

In March 2008, Keppel Seghers started the engineering, supply, construction and commissioning of a Combined Heat and Power (CHP) Waste-to-Energy (WtE) plant in Åmotfors (Sweden). When completed in 2010 the plant will process close to 74,000 tons per year of household waste (average LHV = 10.5 MJ/kg) and limited quantities of (demolition) wood resulting in a yearly production of about 108,700 MWh of steam, 12,100 MWh of heat and 13,400 MWh of electricity. Herewith, the Åmotfors WtE-CHP is sized to meet the joined energy needs of the local paper production, neighboring industries and buildings at an overall net plant efficiency of almost 65%. The WtE-CHP will offer state-of-the-art combustion and energy recovering technology, featuring Keppel Seghers' proprietary Air-Cooled Grate, SIGMA combustion control and integrated boiler. Waste is fed into the combustion line with an automatic crane system. To surpass the stringent EU emission requirements, a semi-dry flue gas cleaning system equipped with Keppel Seghers' Rotary Atomizer was selected as economic type of process for purifying the combustion gas from the given waste mixture. Furthermore a low NOx-emission of 135 mg/Nm 3 (11%O2,dry) as imposed by Swedish law is achieved by SNCR. The plant engineering is described with a focus on the overall energy recovery. As stable steam supply to the paper mill and the district heating system needs to be assured under all conditions the design includes for supporting process measures such as combustion air preheating, steam accumulation, turbine bypassing, buffering of the main condenser and back-up energy supply from an auxiliary fuel boiler. Additionally, external conditions can trigger distinct plant operation modes. A selected number of them are elaborated featuring the WtE-plant's capability to conciliate a strong fluctuating steam demand with the typical intrinsic inertia of a waste-fired boiler. With prices for fossil fuels increasing over the years, the cost for generating process steam and heat has become dominant and for paper mills even makes the overall difference in viability. As will be documented in this paper, the decision to build the Åmotfors WtE-CHP was taken by Nordic Paper after a quest for significant cost-cutting in the production of process energy. Moreover, the use of industrial and household waste as fuel brings along the advantage of becoming largely independent from evolutions on the international oil and gas markets. By opening up the possibility for a long-term secured local (waste) fuel supply at fixed rates, WtE-technology offers a reliable alternative to maintain locally based industrial production sites. The Nordic Paper mills in Åmotfors are therefore now the first in Sweden to include a waste-fired CHP on a paper production site. © 2010 by ASME.


Van den Broeck R.,Catholic University of Leuven | Van Dierdonck J.,Catholic University of Leuven | Nijskens P.,Keppel Seghers | Dotremont C.,Keppel Seghers | And 5 more authors.
Journal of Membrane Science | Year: 2012

Membrane fouling remains a significant drawback for membrane bioreactors (MBRs). The solids retention time (SRT) has been widely acknowledged to be an important factor influencing membrane fouling. In general, lower membrane fouling rates are observed at elevated SRTs, however, the direct mechanisms through which a high SRT alleviates fouling are unclear. Since it has also been reported that activated sludge bioflocculation is an important factor in membrane fouling, this paper studies the impact of SRT on bioflocculation with respect to membrane fouling. A pilot-scale MBR was operated for more than two years at three different SRTs during which bioflocculation was closely monitored by means of an automated image analysis procedure while the fouling rate was recorded on-line for different fluxes and different filtration/relaxation cycles. In addition, the Delft filtration characterization method (DFC m) was employed to assess the activated sludge fouling propensity. Based on these data, it is shown that stable operation of a membrane bioreactor requires a good activated sludge condition and that bioflocculation is a crucial factor within that context. In the tested SRT range (10-30-50 days), a higher SRT contributes to better activated sludge bioflocculation and as a consequence, to lower fouling rates. © 2012 Elsevier B.V.


Van den Broeck R.,Catholic University of Leuven | Van Dierdonck J.,Catholic University of Leuven | Caerts B.,Catholic University of Leuven | Bisson I.,Catholic University of Leuven | And 5 more authors.
Separation and Purification Technology | Year: 2010

Membrane bioreactors (MBRs) have proven to be a valuable alternative for conventional activated sludge plants. Membrane fouling remains, however, a significant drawback. Stable operation of a membrane bioreactor requires a good sludge condition. In this paper it is evidenced that bioflocculation is a crucial factor within that context. By changing the ratio of monovalent over polyvalent cations ([M/P]) in the influent, a deflocculation-reflocculation event was induced during which the impact of bioflocculation on fouling in membrane bioreactors could be studied. In a first phase, a high [M/P] influent was fed to the MBR which resulted in severe sludge deflocculation and worsened filtration characteristics. A low [M/P] influent was subsequently fed to the MBR. Within 3 weeks, the activated sludge reflocculated and filtration characteristics improved significantly. Monitoring of bioflocculation in MBRs is thus of extreme importance to start possible remediation as quickly as possible. Fragment surface proved to be a valuable parameter in that respect. In contrast, no clear relation between EPS and filtration characteristics could be found. This work substantiates the hypothesis that a well functioning dynamic secondary membrane, built up by robust activated sludge flocs, can prevent severe (irreversible) fouling in MBRs. © 2009 Elsevier B.V. All rights reserved.


Logist F.,Catholic University of Leuven | Van Dierdonck J.,Catholic University of Leuven | Van Den Broeck R.,Catholic University of Leuven | Dotremont C.,Keppel Seghers | And 4 more authors.
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

The current paper presents a geometrically inspired approach for the optimization and control of low pressure filtration units for (waste)water treatment. The optimization aims at minimizing the operational costs, encompassing both energy and chemical cleaning costs (and, hence, accounting for reversible as well as irreversible fouling), while ensuring a minimum required nett water flux. Advantage has been taken of the process' cyclic nature. In each cycle the transmembrane pressure increases during the forward flow phase due to fouling and decreases again due to backflushing. Assuming linear increases/decreases allows the use of simple geometric approaches for computing analytical cost and constraint expressions. Relating both slopes to operational parameters as forward flux and filtration time, provides the handles for the actual control and optimization. However, due to the discrete nature of the number of cycles in one operation run, a relaxation strategy is employed for solving the optimization problem. Simulation results are presented for a preliminary filtration model inferred from a microfiltration plant for secondary effluent upgrading in the context of a research project with the Keppel Seghers company. © 2011 IFAC.

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