Industrial scrubbers

Flue gas scrubbers

Emission limit values

All thermal treatment systems for waste processing produce flue gas emissions that contain concentrations of hazardous pollutants. The objective of a flue gas treatment system is to drastically reduce the emissions of substances harmful to human health and the environment, before liberation into the air. Flue gas scrubbers form an integral part of DIs’ engineering and industrial incinerator installations. Our scrubber designs certainly exceed the emission limit values and monitoring requirements for pollutants to air/soil/water, set and published by the EU, EPA and WHO. Accordingly, our incinerator facilities are in full compliance with the European Waste Incineration Directive 2000/76/EC and with the US EPA Clean Air Act and Air Pollution.

Emissions from well managed modern incinerators have been significantly reduced during the past 25 years and are no longer a major concern for the environment and our health.
Dry and wet industrial scrubbers are two of the most efficient pollution removal technologies to effectively cleanse flue gases produced by waste incineration.

Dry scrubber — DFGT

Removal of harmful contaminants in the flue gas is done in three steps: gas cooling, reagent injection and filtering. The scrubbing system include a dosing mechanism for additive(s), reaction and residence chamber and a bag filter for final dust removal.

Advantages
  • Positive environmental impact. Dry scrubbers produces comparatively little waste material.
  • The flue gas leaves the system at temperatures above dew point of water and most common acidic components in the flue gas. This reduces or eliminates the visible water-vapour plume on the stack.
  • Dry scrubbing reduces or eliminates corrosion issues.
  • The implementation of a bag filter results in the lowest emission of dust. They are typically lesser than 5 mg/m3.
  • Aerosol emmisions,  such as “white smoke” are effectively captured in a bag filter.
  • No make-up water required.
  • No associated cost like removing, transporting and storing wastewater from wet scrubbers.
  • DI dry scrubbers are 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.
Disadvantages
  • Dry scrubbers generally have a higher capital investment cost.
  • The residual waste powder (fly ash) is highly toxic and must be safely disposed at a secured hazardous waste landfill site, or sent to a specialist treatment plant.
  • Dry scrubbers cannot remove 100% contaminants from the flue gas.

Wet scrubber — WFGT

Flue gas is funneled through an area and sprayed with a wet substance. Water is used as circulation fluid when dust and particulate matter is to be removed, but chemicals can be added for heavier pollutants. As flue gases pass through the cleaning mist, contaminants are attracted to the mist and pulled out from the flue gases and attach to the liquid, because of its chemical composition.

Advantages
  • Capability to achieve very low emission concentrations on acidic flue gas compounds, with relative simple technology.
  • Capable to absorb wide and fast fluctuations in acidic flue gas component supply.
  • Can achieve reasonably low dust emission concentrations, typically below 50 mg/m3 corrected (as a single step solution, it’s not low enough to meet EU regulations).
  • Wet scrubbers can tolerate a wide range of temperatures, making them ideal for operation in almost any environment.
  • Relative low investment costs.
  • Quite simple to operate and control.
Disadvantages
  • Water from industrial quality needs to be available in sufficient amounts.
  • Water treatment is required. Smaller wastewater quantities could be treated via the incineration process.
  • Maintaining PH within certain margins to avoid corrosion.
  • A wet scrubbing process adds significant amounts of vapour to the exhaust, which causes the release of a “white vapour plume” when vented through the smokestack.

Combination DFGT + WFGT

A combination of dry and wet flue gas treatment might be the best choice in specific cases. It results in the most optimum emission reduction solution, as the advantages and disadvantages of each option will be balanced and optimized.

Additives

The choice of which additive to use, depends on the type of waste and contaminants to be removed. Operating costs could be considered as well.

We apply the following additives

Dry scrubbing
  • Dry scrubbing based on sodium bicarbonate (NaHCO3). This relative new technology can achieve higher emission reduction efficiencies, resulting in lower operating costs. It’s our preferred option compared to conventional lime (calcium) based technologies.
  • Addition to dry scrubbing of activated carbon to capture dioxins and heavy metals.
Wet scrubbing
  • Wet scrubbing based on caustic (NaOH), present in a diluted form.

Filter bags

Catalytic FABRIC filter BAGS FOR DRY FLUE GAS TREATMENT.

 

A catalytic fabric filter bag consists of different fabric layers, whereas each layer contains a unique long life catalyst to decompose and remove multiple gaseous compounds.

In one single step and without injection of activated carbon, the catalytic fabric filter converts up to 99% of total dioxins and furans into harmless gaseous species (primarily CO2 and H2O), allowing them to be discharged safely through the smokestack. The catalytic performance for removing dioxins and furans and intercepting dust passes the strictest emission regulations.

Emission monitoring — CEMS

Flue gas emissions should be monitored on a continuous basis to ensure that final emissions constantly comply with the applicable regulations. A Continuous Emission Monitoring System (CEMS) permanently measures typical emission parameters e.g. SO2, HCl, NOx, HF, CO, O2, H2O, CO2, TOC, particulate matter, opacity and more components. Emission results are represented in the central control room and stored in a database for reporting to authorities. Dry and wet scrubbing require different monitoring devices.

Dry scrubber — DFGT

Dry scrubber — DFGT

Removal of harmful contaminants in the flue gas is done in three steps: gas cooling, reagent injection and filtering. The scrubbing system include a dosing mechanism for additive(s), reaction and residence chamber and a bag filter for final dust removal.

Advantages
  • Positive environmental impact. Dry scrubbers produces comparatively little waste material.
  • The flue gas leaves the system at temperatures above dew point of water and most common acidic components in the flue gas. This reduces or eliminates the visible water-vapour plume on the stack.
  • Dry scrubbing reduces or eliminates corrosion issues.
  • The implementation of a bag filter results in the lowest emission of dust. They are typically lesser than 5 mg/m3.
  • Aerosol emmisions,  such as “white smoke” are effectively captured in a bag filter.
  • No make-up water required.
  • No associated cost like removing, transporting and storing wastewater from wet scrubbers.
  • DI dry scrubbers are 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.
Disadvantages
  • Dry scrubbers generally have a higher capital investment cost.
  • The residual waste powder (fly ash) is highly toxic and must be safely disposed at a secured hazardous waste landfill site, or sent to a specialist treatment plant.
  • Dry scrubbers cannot remove 100% contaminants from the flue gas.
Wet scrubber — WFGT

Wet scrubber — WFGT

Flue gas is funneled through an area and sprayed with a wet substance. Water is used as circulation fluid when dust and particulate matter is to be removed, but chemicals can be added for heavier pollutants. As flue gases pass through the cleaning mist, contaminants are attracted to the mist and pulled out from the flue gases and attach to the liquid, because of its chemical composition.

Advantages
  • Capability to achieve very low emission concentrations on acidic flue gas compounds, with relative simple technology.
  • Capable to absorb wide and fast fluctuations in acidic flue gas component supply.
  • Can achieve reasonably low dust emission concentrations, typically below 50 mg/m3 corrected (as a single step solution, it’s not low enough to meet EU regulations).
  • Wet scrubbers can tolerate a wide range of temperatures, making them ideal for operation in almost any environment.
  • Relative low investment costs.
  • Quite simple to operate and control.
Disadvantages
  • Water from industrial quality needs to be available in sufficient amounts.
  • Water treatment is required. Smaller wastewater quantities could be treated via the incineration process.
  • Maintaining PH within certain margins to avoid corrosion.
  • A wet scrubbing process adds significant amounts of vapour to the exhaust, which causes the release of a “white vapour plume” when vented through the smokestack.

Combination DFGT + WFGT

Combination DFGT + WFGT

A combination of dry and wet flue gas treatment might be the best choice in specific cases. It results in the most optimum emission reduction solution, as the advantages and disadvantages of each option will be balanced and optimized.

Additives

Additives

The choice of which additive to use, depends on the type of waste and contaminants to be removed. Operating costs could be considered as well.

We apply the following additives

Dry scrubbing
  • Dry scrubbing based on sodium bicarbonate (NaHCO3). This relative new technology can achieve higher emission reduction efficiencies, resulting in lower operating costs. It’s our preferred option compared to conventional lime (calcium) based technologies.
  • Addition to dry scrubbing of activated carbon to capture dioxins and heavy metals.
Wet scrubbing
  • Wet scrubbing based on caustic (NaOH), present in a diluted form.
Filter bags

Filter bags

Catalytic FABRIC filter BAGS FOR DRY FLUE GAS TREATMENT.

 

A catalytic fabric filter bag consists of different fabric layers, whereas each layer contains a unique long life catalyst to decompose and remove multiple gaseous compounds.

In one single step and without injection of activated carbon, the catalytic fabric filter converts up to 99% of total dioxins and furans into harmless gaseous species (primarily CO2 and H2O), allowing them to be discharged safely through the smokestack. The catalytic performance for removing dioxins and furans and intercepting dust passes the strictest emission regulations.

Emission monitoring (CEMS)

Emission monitoring — CEMS

Flue gas emissions should be monitored on a continuous basis to ensure that final emissions constantly comply with the applicable regulations. A Continuous Emission Monitoring System (CEMS) permanently measures typical emission parameters e.g. SO2, HCl, NOx, HF, CO, O2, H2O, CO2, TOC, particulate matter, opacity and more components. Emission results are represented in the central control room and stored in a database for reporting to authorities. Dry and wet scrubbing require different monitoring devices.

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