Performance of limestone‐based sorbent for sorption‐enhanced gasification in dual interconnected fluidised bed reactors

Fluidised-bed steam dryers have been in use for industrial-scale drying of pressed beet pulp for more than 20 years. This highly energy-efficient process can be considered to be state of the art in the industry. Scientific laboratory and pilot-plant testing have provided the basis for a detailed description of the principles of fluidisation and drying in superheated water vapour. Advances in production data acquisition, in particular regarding the options for the real-time presentation and evaluation of high-resolution operating data (Industry 4.0), have opened up new potentials for optimisation of the drying process in fluidised-bed steam dryers. By analysing and interpreting sequences of events, or simultaneous events, it is now possible to analyse process behaviour in great depth. This allows malfunctions to be avoided by improved design or, assisted by suitable measuring and control systems, to be detected at an early stage. Failures can then be prevented altogether by initiating automated countermeasures. On the basis of more recent insights gained from the analysis of faults and disruptions using modern operating data acquisition, BMA’s fluidised-bed steam dryer (WVT) has been subjected to fundamental technological and technical improvements, so it now meets today’s demands for efficiency and reliability. Modifications include the product inlet, the distribution plate and several other parts, in addition to the known and patented PPS (Plug Protection System; EP 2457649 B1), and the patented rotary weir (EP 2146167 B1).

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Production of fuels on the basis of sewage sludge through conditioning using high calorific value fractions

Water Practice & Technology ◽

10.2166/wpt.2008.011 ◽

2008 ◽

Vol 3 (1) ◽

Author(s):

Karl-Georg Schmelz ◽

Anja Reipa ◽

Hartmut Meyer

Keyword(s):

Sewage Sludge ◽

Wastewater Treatment Plants ◽

Treatment Plant ◽

Calorific Value ◽

Fluidised Bed ◽

Sludge Treatment ◽

Heating Value ◽

Fine Coal ◽

Used Cars ◽

Plastic Components

Emschergenossenschaft and Lippeverband operate 59 wastewater treatment plants which produce approx. 100,000 Mg TS of sewage sludge each year. Using sludge pressure pipelines, about 60 % of this sludge are transported to the central sludge treatment plant in Bottrop. The digested sludges are conditioned using fine coal and polymers and are dewatered using membrane filters. By adding coal, the heating value of the sludge is raised which enables autothermal combustion of the dewatered sludges in fluidised bed furnaces at the central sludge treatment plant. In order to replace coal, a fossil fuel, as conditioning agent, experiments were conducted using alternative materials with high heating values. The addition of shredder fluff agglomerates proved to be particularly successful. Shredder fluff agglomerates are a residue from the recycling of used cars and are generated in a multistage process (e.g. Volkswagen-SiCon Process) by separating the light shredder fraction (plastic components etc.) from the total shredder fluff. The fibrous material is outstandingly suitable for improving the dewaterability and for sufficiently raising the heating value of the dewatered sludge in order to enable autothermal combustion. Since first experiments showed very positive results, a full-scale long-term test-run will take place in 2007.

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Gasification as an optimum alternative for the sludge management

Water Practice & Technology ◽

10.2166/wpt.2011.0080 ◽

2011 ◽

Vol 6 (4) ◽

Cited By ~ 2

Author(s):

C. Peregrina ◽

J. M. Audic ◽

P. Dauthuille

Keyword(s):

Power Generation ◽

Anaerobic Digestion ◽

Sewage Sludge ◽

Combined Heat And Power ◽

Gas Production ◽

Waste Reduction ◽

Fluidised Bed ◽

Sludge Management ◽

Gas Cleaning ◽

Cleaning System

Assimilate sludge to a fuel is not new. Sludge incineration and Combined Heat and Power (CHP) engines powered with sludge-derived anaerobic digestion gas (ADG) are operations widely used. However, they have a room of improvement to reach simultaneously a positive net power generation and a significant level of waste reduction and stabilization. Gasification has been used in other realms for the conversion of any negative-value carbon-based materials, that would otherwise be disposed as waste, to a gaseous product with a usable heating value for power generation . In fact, the produced gas, the so-called synthetic gas (or syngas), could be suitable for combined heat and power motors. Within this framework gasification could be seen as an optimum alternative for the sludge management that would allow the highest waste reduction yield (similar to incineration) with a high power generation. Although gasification remains a promising route for sewage sludge valorisation, campaigns of measurements show that is not a simple operation and there are still several technical issues to resolve before that gasification was considered to be fully applied in the sludge management. Fluidised bed was chosen by certain technology developers because it is an easy and well known process for solid combustion, and very suitable for non-conventional fuels. However, our tests showed a poor reliable process for gasification of sludge giving a low quality gas production with a significant amount of tars to be treated. The cleaning system that was proposed shows a very limited removal performance and difficulties to be operated. Within the sizes of more common WWTP, an alternative solution to the fluidised bed reactor would be the downdraft bed gasifier that was also audited. Most relevant data of this audit suggest that the technology is more adapted to the idea of sludge gasification presented in the beginning of this paper where a maximum waste reduction is achieved with a great electricity generation thanks to the use of a “good” quality syngas in a CHP engine. Audit show also that there is still some work to do in order to push sludge gasification to a more industrial stage. Regardless what solution would be preferred, the resulting gasification system would involve a more complex scenario compared to Anaerobic Digestion and Incineration, characterised by a thermal dryer and gasifier with a complete gas cleaning system. At the end, economics, reliability and mass and energy yields should be carefully analysed in order to set the place that gasification would play in the forthcoming processing of sewage sludge.

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Pilot-scale neutralisation of underground mine water

Water Science & Technology ◽

10.2166/wst.1996.0250 ◽

1996 ◽

Vol 34 (10) ◽

pp. 141-149 ◽

Cited By ~ 2

Author(s):

J. P. Maree ◽

G. J. van Tonder ◽

P. Millard ◽

T. C. Erasmus

Keyword(s):

Mine Water ◽

Contact Time ◽

Pilot Scale ◽

Underground Water ◽

Underground Mine ◽

Economic Feasibility ◽

Fluidised Bed ◽

Chemical Composition Of Water ◽

Before And After ◽

Time Required

Traditionally acid mine water is neutralised with lime (Ca(OH)2). Limestone (CaCO3) is a cheaper alternative for such applications. This paper describes an investigation aimed at demonstrating that underground mine water can be neutralised with limestone in a fluidised-bed. The contact time required between the limestone and the acid water, chemical composition of water before and after treatment, and economic feasibility of the fluidised bed neutralisation process are determined. A pilot plant with a capacity of 10k1/h was operated continuously underground in a gold mine. The underground water could be neutralised effectively using the limestone process. The pH of the water was increased from less than 3 to more than 7, the alkalinity of the treated water was greater than 120 mg/l (as CaCO3) and the contact time required between mine water and limestone was less than 10 min (the exact contact time depends on the limestone surface area). Chemical savings of 56.4% can be achieved compared to neutralisation with lime.

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