Le Havre plant-France, Case study

1. International Symposium SIDISA 2012
AIR AND SOLID LOW POLLUTION EMISSION IN A SPECIFIC BIOLOGICAL
SLUDGE THERMAL TREATMENT PLANT– HIGH TEMPERATURE
FLUIDIZED BED LE HAVRE CASE STUDY
PEDRAZZI Luca*§; DANGTRAN Ky**; LEBONNOIS Damien*
* Degremont Italia S.p.A.; 57 B. Crespi – Milan, 20159 - Italy.
** Infilco Degremont Inc.; 8007 Discovery Drive –Richmond, 23229, VA - USA
§ corresponding author e-mail: luca.pedrazzi@degremont.com
Key words: sludge fluid bed incineration, flue gas analysis, energy recovery
Abstract
Le Havre is a port city in Northwestern of France, located on the right bank of the mouth of the
river Seine on the English Channel. In 2011 a new wastewater treatment plant was built and put in
service to serve a population of 415, 000 inhabitants. The sludge treatment is mainly by dewatering
with filter press followed by fluid bed incinerator Thermylis™. Le Havre incineration system
consists of a high temperature fluidized bed equipped with a two-stage thermal energy recovery,
with air preheating to maintain autogenous combustion and hot water production for building heat.
Combustion gas is treated by a two-stage air pollution control system equipped with cyclone
followed by chemical injection and bag-filter.
Fluidized bed incineration has been gaining more acceptance over the last few years as
municipalities focus on green and sustainable technology with maximum energy recovery, and
minimisation of the WWTP waste evacuation. One of the major barrier to incineration is the
NIMBY (not in my backyard) syndrome. With Le Havre fluid bed system in full operation since
June 2011, flue gas pollutants, ash and spent chemicals analysis is presented in this paper, with the
ultimate goal of providing a case study of emissions for most important air pollutants from sludge
fluidized bed incineration plant. This paper will be a useful tool for a novel approach to social
evaluations of the new installation. Energy consumption figures recorded at the plant in comparison
with drying plant are also presented in this paper.
Le Havre incineration plant was designed to treat 1.2 tons of dry matter per hour, or 3.75 tons of
wet cake per hour at 32% dryness and 55% of volatile matter. At design condition, the system shall
not use any fossil fuel and shall produce 0.442 t/h of ash and 0.165 t/h of spent chemicals Chemical
consumption was designed for 68 kg/h of sodium bicarbonate and 3 kg/h of activated carbon, in
order to respect European environmental limits. The guarantee on the electrical consumption was
362 kW el / h.
During the first four months of operation, the design capacity of 1.2 ton per day was met and kept
constant even with a sludge dryness of only 25%, much lower than design condition (32%). With an
ash production close to design, chemical consumption and the by-product spent chemicals was
lower than design. Emissions of all gas pollutants including TOC, NOx, SO2, dust, dioxins and
furans are lower than the daily admissible limits (by at least 2 to 10 times). Combustion is complete
with an unburned carbon in the ash of less than 0.01%. Heavy metal concentrations in the ash and
spent chemicals are close to the detection limits. For the first four months of operation, with a cake
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2. International Symposium SIDISA 2012
dryness of only 25% (design = 32%), fossil fuel usage was 700 kWh/ dry ton or five times the
design value (143 kWh/dry ton), even though much lower than the estimated fuel consumption at
drying plant (3000 kWh/dry ton).
During the last month of commissioning, with the optimization of the sludge dewatering equipment,
a much dryer cake was obtained (30%), natural gas consumption was reduced to lower than 50
kWh/dry ton. Ash from Le Havre plant passes all leachability tests for heavy metals, and can be
reused, while spent chemicals are treated for salts recovery.
The successful operation at the Le Havre WWTP has shown the modern fluid bed incineration
system to be an economical, environmentally acceptable sludge disposal method satisfactory to the
Authority, the permitting agencies and the general public.
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