Dutch Incinerators - Flue Gas Emission Reduction Process System
The Flue gas emission reduction process of the Rotary Kiln Incinerator reduces the concentration of contaminants as present in the flue gasses to levels below the applicable emission standards. Typically, Dutch Incinerators designs comply with EU regulations in this regard, the most strict on the planet. Several systems and options are available to meet the applicable emission standards.
Dry scrubbing emission control systems
These scrubbing systems are characterized by the fact that the flue gas is treated without complete saturation of the flue gas stream with water (with other words, without completely quenching the flue gas stream with water). Typically they include a dosing mechanism for additive(s), reaction and residence chamber and a bag filter for final dust removal. The choice of additive depends upon the types of contaminants to be removed and financial considerations, mainly operating costs. Dutch Incinerators can provide the following technologies:
- Dry scrubbing based on dry lime injection (Calcium based).
- Semi dry scrubbing based on lime slurry injection with complete evaporation (Calcium based).
- Dry scrubbing based on sodium bicarbonate. Higher emission reduction efficiencies can be achieved with this relative new technology also resulting in lower operating costs overall. Generally the preferred option comparing with conventional lime based technologies.
- Activated carbon addition to capture dioxins, heavy metals.
Dry scrubbing systems have the following advantages and disadvantages compared with wet scrubbing:
- The flue gas leaves the system at temperatures above the dew point of water and most common acidic components in the flue gas.
- This reduces or eliminates the visible water vapor plume on the stack.
- This reduces or eliminates corrosion issues, quite common with improper designed or operated wet scrubber systems.
- The implementation of a bag filter results in the lowest emission of dust (PM, particulate matter or TSP, total suspended particles), typically lower than 5 mg/m3, corrected.
- Aerosols, such as “white smoke” are effectively captured in a bag filter.
- No make-up water required.
- No waste water treatment required.
- Is capable to achieve emission levels within EU regulations as a single step solution, depending upon the type of additive used, design of the system, acidic gas loads and dosing capacities.
- Generally higher initial investment costs, due to the bag filter, optional sodium bicarbonate grinder, lime make up systems, additive storage systems and reaction and residence time ducting.
Wet scrubbing emission control systems
Wet scrubbing systems are based on the reaction of acidic flue gas contaminants with caustic (NaOH), present in a diluted form in the wet scrubber circulation fluid.
Wet scrubbing systems have the following advantages and disadvantages compared with dry scrubbing:
- Capable to achieve very low emission concentrations on acidic flue gas compounds with relative simple technology.
- Capable to achieve reasonably low dust emission concentrations, typically below 50 mg/m3 corrected (but apart from specific cases not low enough to meet EU regulations if applied as a single step solution).
- Relative low investment costs.
- Relative simple to operate and control.
- Capable to absorb wide and fast fluctuations in acidic flue gas component supply, as the scrubber water and sodium based chemistry acts as a fast acting buffer to absorb these contaminants.
- A wet scrubber consumes water. This needs to be available in sufficient quantities.
- A wet scrubber produces waste water. This needs to be treated. Smaller quantities can be treated in the incineration process itself, but generally speaking some means of water treatment is required.
- Corrosion might me a problem, although more an operational problem for a properly designed system (not maintaining pH within certain margins).
- Wet scrubbers have more problems to reduce aerosols emissions, such as “white smoke” as produced by a hazardous waste incinerator depending upon waste input. Specific measures are available to reduce this problem, but efficiency is lower than a dry scrubbing based system.
Combination of dry- and wet scrubbing systems.
A combination of a dry- and wet scrubbing system might be the optimum choice in specific cases, considering the above, resulting in the most optimum emission reduction solution for the total facility as the advantages and disadvantages of each option can be balanced and optimized.