Objective
The project aims at demonstrating the reliability of a fixed-film fluidized bed using innovative mineral carrier (biolite R 280) for the mesophilic anaerobic treatment of pulp-mill (250 tons/day cardboard production) waste water. Daily preheated 1500 m3 (4500 kg COD) will be treated in a methane fluidized bed of 130 m3 working volume (space loading rate : 35 kg COD m-3 d-1) and postdecanted. Biogas will be used for producing steam : expected conversion: 85 % on BOD, 75 % on COD.
The methanisation plant is operational since March 1989. It has proven its ability to treat the pollution generated by the pulp-mill effluent with a COD removal efficiency of 75-80%. The load of 35 kg of COD/m3/day, sensibly higher than with more conventional processes, has been reached without affecting the pollution abatment yield, which shows that this space loading is not a limiting factor in thsi range of operation. The process is very efficient when the factory production parameters are very stable; it is also flexible because the results remain satisfactory under irregular operation parameters. The net energy balance of methanisation is almost equal to zero : 264 TOE/year of biogas are produced, of which 211.6 are consumed to heat the effluent before digestion. 52.4 TOE/year of biogas remain available for steam production in the factory, but their energy content is counterbalanced by the auto-consumption in electricity, expressed in primary energy.
However, when compared toa conventional aerobic purification plant, the project leads to electricity savings which correspond to 133 TOE/year in primary energy and to a monetary saving in operating costs amounting to 62 850 ECU/year.
This process is applicable, not only in the papaer production sector, but more generally for effluents with a COD content higher than 2.5 g/l, i.e. also for effluents from agrofood, chemical and pharmaceutical industries.
- Present discharge to the river:
. flowrate: 1500 m3/day
. temperature: 20 to 30 deg. C
. suspended solids: 40 mg/l
. BOD 5: 1500 mg/l
. COD: 3700 mg/l
. pH: 5.4 to 5.6
- Maximum authorized discharge figures (after treatment):
. BOD 5: 250 mg/l
. COD: 833 mg/l
- Plant:
. equalization tank, 1500 m3 volume, with mechanical mixer, pH adjustment, chemicals metering units, collection pumps.
. effluent heating through two platular exchangers working in series: the first one recovers heat from the treated effluent, the second stage uses steam produced in a boiler from biogas.
. methanization in an insulated fluidized bed reactor of which the main characteristics are:
. diameter: 4 m
. total height: 17.2 m
. active zone volume: 130 m3
. applied space loading: 35 kg COD/m3/d-1
. expected COD removal efficiency: 80 %
This reactor is equipped with recirculation pumps and a device to control the amount of biomass in the fluidized bed.
- Clarification in a scraped settling tank, diameter : 10m.
- Temporary storage of biogas (production: 60 to 80 m3/hr) in a 40 m3 flexible gas holder.
- Production of steam in a boiler fed with biogas:
. nominal power: 465 kW
. nominal capacity: 690 kg/hr
. maximal pressure: 15 bar.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
92508 RUEIL-MALMAISON
France