Waste accepted at the site is deposited on the tip floor. The waste is screened for unacceptable >materials and stacked. A front-end loader feeds the waste into the incinerators.
The tip floor can store approximately 2,250 tonnes of waste. This translates into approximately 4 days of feedstock for the incinerators.
There are 5 identical Consumat gasifiers. Each gasifier has a lower and an upper chamber. The waste is fed into the lower chamber where it is heated for approximately about 6 hours at 850° C in a low-oxygen atmosphere (50% air-to-fuel mixture).
The combustible portion of the waste is converted into gas rich in combustible compounds. The gas is drawn into the upper chamber where it is combusted into an oxygen rich atmosphere (200% air-to-fuel mixture). The temperature in the upper chamber reaches 1000° C.
Controlled Air Concept
Type: 2-stage gasifier/combustion module
Number of Units: 5
Approved Operation Range:
90 to 120 tonnes/day
Design Heating Value of MSW:
5,500 Btu/lb (12,764 kj/kg)
Operation Temperature Range:
1000°C – 1100°C (Upper chamber)
Combustion Gas Residence Time:
Minimum 1 second at 1000°
Each gasifier has a dedicated boiler. Each boiler extracts heat from the flue gas and transfers it to boiler feedwater which turns into superheated steam.
Type: Heat Recovery Steam Generator
Number of Units: 5
Rated Capacity: 12,250 kg/hr (27,000 lb/hr)
Steam Pressure: 600 psig (4,238 kpa)
Steam Temperature: 343° C (650° F)
STEAM TURBINE GENERATOR
Steam from the boilers is sent to a steam turbine which powers an electric generator. Electricity from the generator powers the facility with the remainder being exported to the grid.
Model: Westinghouse EM-25 multi-stage steam.
Number of Units: 1
Rated output: 9.31 MW-enough electricity to power over 6,000 homes.
Output Voltage: 4,160 VAC, three phase 60 Hz.
AIR POLLUTION CONTROL SYSTEM (APC)
The flue gas from the boilers is collected in a common duct and directed to the air pollution control system. The flue gas is split into two identical treatment trains consisting of an evaporative cooling tower, venture reactor, baghouse and induced draft fan. The flue gas is then re-combined into one duct and sent to the Selective Catalytic Reduction System and ultimately emitted through the main stack.
EVAPORATIVE COOLING TOWER
The evaporative cooling tower consists of a vertical vessel where water is sprayed into the gas stream. The water humidifies the gas stream and decreases the gas temperature to 185° C. The reduced gas temperature, combined with the elevated humidity facilitates the operation of the venturi reactor.
Activated Carbon and Dry-lime (CaO) are added to the flue gas stream in the venturi reactor. The dry-lime combines with acid gases in the flue gas stream to form calcium compounds. Activated carbon is injected into the flue gas stream to absorb mercury and other heavy metals. The particulate-laden flue gas pass through the reactor to the baghouse.
In the baghouse the flue gas is filtered to remove the particulate matter. The particulate includes unreacted lime, calcium compounds, activated carbon and uncombusted materials. Unreacted lime collects on the surface of the filter bags serving to further remove any acid gases from the flue stream. The baghouse contains over 3,900 m2 of filter bags.
SELECTIVE CATALYTIC REDUCTION
The Selective Catalytic Reduction System removes nitrogen oxides, a key component of smog, from the flue gas. Nitrogen oxides are converted to nitrogen and water using heat and ammonia in the presence of a catalyst. The SCR process also oxidizes dioxins and furans lingering in the flue gas to form HCl, CO2 and water vapour.