Flue Gas Treatment Systems

Product Description

Clean Air Thanks to Interdisciplinary Expertise

Flue gas produced by energy-from-waste contains pollutants and must be cleaned before being discharged into the environment. These pollutants introduced into the process by the waste include oxidized combustion products such as SOx and NOx products, as well as substances such as chlorine, fluorine, heavy metals, dioxins and furans. The choice of flue gas cleaning concept is mainly governed by regulatory air pollution limits. Depending on the requirements, a variety of processes are at hand to be used individually or in combination.

Xerosorp

Dry scrubbing – for efficiency and small amounts of residues

The Xerosorp process removes acidic gases by adsorption with sodium bicarbonate. Due to the very high reactivity of sodium bicarbonate, only little overdosing is required which minimizes reagent consumption and residue generation. In addition, activated carbon or coke can be injected for removal of volatile organics and metals. The process is nearly independent of temperature and thus allows optimizing the total process to maximize energy recovery

Key advantages of the XEROSORP process:

• Low emissions with a high flexibility relative to changes of load or flue gas contaminant concentrations
• Minimized sorbent use and residue generation
• High availability and low O&M cost due to simple design and operation

Xerosorp+

The Xerosorp+ Process Combines the Advantages of the Dry Scrubbing Process and Low Temperature SCR-DeNOx System

The Xerosorp+ process is the optimized combination of the Xerosorp and the low temperature SCR-DeNOx processes. If highest removal efficiencies are required for ash, acid gas and NOx, the Xerosorp+ process is the solution with lowest reagent consumtion, lowest residue generation, highest energy efficiency and most compact design. Both the dry scrubbing and the SCR DeNOx processes operate at the same temperature avoiding energy and head losses for flue gas conditioning. Maximum heat can be recovered prior to and after the Xerosorp+ process.

Key Advantages of the XEROSORP+ Process:

• Low emissions and high flexibility relative to load or flue gas contaminant changes
• Minimized use of sorbent and reagent both for dry scrubbing and DeNOx
• Minimized residue generation
• Highest energy efficiency of combined dry scrubbing and SCR DeNOx
• High availability and low O&M cost due to simple design and operation
• Lowest space requirements due to most compact design of the combined process

HZI SemiDry

Putting the Emphasis on Economics and Reliability

The HZI SemiDry process employs the principle of the circulating fluidized bed for efficient removal of acid gases by adsorption with hydrated lime. Recirculation of reagent maximizes reagent use and provides excess reagent to capture contaminat peaks. In addition, activated carbon or coke can be injected for removal of volatile organics and metals.

Key Advantages of the HZI SemiDry Process:

• Low emissions with a high flexibility relative to load or flue gas contaminant changes
• Minimized use of lime as widely-used low-cost reagent
• High energy efficiency compared to lime-slurry based systems
• High availability and low O&M cost due to simple design and operation
• Proven technology with long industry record of success

HZI Wet Scrubber

Wet scrubbing – Pollutant-Free, Step-by-Step

Wet scrubbing is the most effective method for removing acid gases from even heavily burdened flue gases and achieving lowest emission levels. It also assures excellent removal of fine particulates and aerosols. Consumable usage rates and residue quantities are minimised. The contaminants are captured by providing intensive contact between the flue gases and water. Depending on the specific functions of each scrubber stage this may be by injecting the water in small droplets or by providing large contact surfaces through special scrubber packings, this may be co- or countercurrent at small or high velocities and this may be by using plain water or by adjusting the pH through addition of reagents. The reaction products are extracted with the scrubber blowdown which is sent to the effluent treatment before final discharge. 

Key Advantages of the HZI Wet Scrubber Process:

• Lowest acid gas emissions with a high flexibility relative to load or flue gas contaminant changes
• Lowest residue generation from acid gas removal
• Highest availability and lowest O&M cost due to simple design and operation
• Proven technology with long industry record of success

HZI Condensing Scrubber

Wet scrubbing –  Multiple Stages to Zero Contaminants

In addition to the advantages of the Inova Wet Scrubber, the Condensing Scrubber allows additional heat recovery by means of condensation of the water vapour contained in the flue gas. This allows overall EfW plant energy efficiencies of up to 100% or more (on a Lower Heat Value basis). Energy recovered from the condensing scrubber is at a moderate temperature level and may best be used for district heating or in connection with heat pumps. Depending on the design or seasonal heat requirements, the amount of condensing can be adjusted or the condensing scrubber can be operated in non-condensing mode.

Additional Advantages of the HZI Condensing Scrubber Process:

• Allows highest overall EfW plant energy efficiencies