Flue gases containing CO 2 are flowed through the absorber countercurrent to the flow direction of absorbent solution. Inside absorber tower, the absorbent solution reacts chemically with the carbon dioxide in the flue gases. The treated gases are vented to the atmosphere and CO 2 -rich solution leaves the bottom stage of absorber.
What is flue gas treatment?
flue gas treatment | technology | Britannica flue gas treatment, a process designed to reduce the amount of pollutants emitted from the burning of fossil fuels at an industrial facility, a power plant, or another source.
What is flue gas and how does it work?
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator.
What is the dry process for flue gases?
Particle size distribution of dust issued from incineration flue gases from three typical sludges Unlike wet treatment, the dry process treats flue gases as they emerge from the energy recycling system by ensuring that their temperature is compatible with the technologies applied. This supposes the inclusion of a cooling control system.
How do you cool down a flue gas?
It also results in reduced volumetric flow rates, and therefore, it lowers demands on the flue gas cleaning system. Cooling of flue gases may be achieved simply by passing them through a large chamber, which is fitted with cooling water sprays.
What is flue gas cleaning?
Flue-gas scrubbing is a process for removing oxides of sulfur and nitrogen from the waste gases emitted by various industrial processes. Since the oxides of sulfur and nitrogen have been implicated in a number of health and environmental problems, controlling them is an important issue.
What is the process of flue gas desulphurisation?
SNOX Flue gas desulfurization removes sulfur dioxide, nitrogen oxides and particulates from flue gases; Dry sorbent injection systems that introduce powdered hydrated lime (or other sorbent material) into exhaust ducts to eliminate SO2 and SO3 from process emissions.
What is the use of flue gas?
9.4 Flue gas Combustion is used primarily for heat by changing the potential chemical energy of the fuel to thermal energy. This occurs in a fossil fuel-fired power plant, a home furnace, or an automobile engine. Combustion is also used as a means of destruction for our unwanted materials.
Is flue gas harmful for the environment?
Some of these - nitrogen, oxygen, carbon dioxide and water vapour - are not directly harmful to humans, although the impact on the environment is certainly clear. But flue gas also includes pollutants, which need to be removed before they exit the stack itself.
How is sulphur dioxide removed from flue gas?
For the removal of SO2 from flue gas, a wet process using calcium carbonate as an absorbent is most commonly adopted in commercial plants. The wet process shows a high efficiency but needs a large amount of water. SO2 is fixed in the form of calcium sulfate.
Why is FGD required?
FGD is a system which reduces the SOx in flue gas through chemical treatment and converting the captured SOx into a by-product such as Gypsum or Calcium Sulphate or Sulphuric Acid depending upon the type of mechanism used. Dry scrubbing.
What is the pressure of flue gas?
After WGS, the Co2 concentration in the flue gas is relatively high, which is in the range of 15–60% (dry basis) at a total pressure of 2–7 MPa (Gazzani et al., 2013a; Gazzani et al., 2013b), thus physical solvents such as Selexol and Rectisol rather than chemical solvents are commonly used for pre-combustion capture.
How is Co2 removed from flue gas?
Experimental results obtained in this study demonstrate that removal of flue-gas CO2 can be achieved via formation of solid NH4HCO3 through ammonia carbonation in the gas phase. Removal of CO2 is quantified by monitoring CO2 concentrations at the entrance and exit of the reactor column.
What is the temperature of flue gas?
Currently, the minimum flue gas temperature for boilers is equal to 120-130 °C. in this temperature of leaving gases eliminates the condensation in the flues and smoke stacks, natural draught increases. However, in many boilers the actual temperature of the flue gas is equal to 180 – 200 °C.
What does flue gas smell like?
The gas itself is odourless, but when it escapes through an appliance like a boiler, then it can be detected by your nose. This will often come in the form of an unpleasant rotten eggs smell. You might also notice black stains around the area the boiler is situated in, which could be an indicator there is a leak.
Why is it called flue gas?
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator.
Is flue gas flammable?
Since ambient air contains about 79 volume percent gaseous nitrogen (N2), which is essentially non-combustible, the largest part of the flue gas from most fossil fuel combustion is unburnt nitrogen.
What is flue gas treatment?
Flue gas treatment technologies are post-combustion processes to convert NOx to molecular nitrogen or nitrates. The two primary strategies that have been developed for post-combustion control and are commercially available are selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). Additional concepts are under development, including combining SCR and SNCR technologies (known as hybrid SCR/SNCR) and rich reagent injection; however, these are not extensively used at this time. Of these technologies, SCR is being identified by utilities as the strategy to meet stringent NO x requirements. These technologies are discussed in the following sections, with an emphasis on SCR.
How is acid gas neutralized?
The acid gas is neutralized by injection of a basic reagent. The drum containing ceramic spheres improves the agglomeration of particles. Electrical energy is consumed. An electric heater regulates the filter temperature in order to avoid any condensation. Sign in to download full-size image.
How does FBC reduce NOx?
Techniques currently used for FBC systems include reducing the peak temperature by flue gas recirculation, natural gas reburning, overfire air/air staging, fuel reburning, low excess air, and reduced air preheat. Postcombustion control is also used, including selective noncatalytic reduction (SNCR) and selective catalytic reduction (SCR), which achieve 35 to 90 percent NO x reductions. Air staging, SNCR, and SCR will be briefly discussed here but are presented in more detail in Chapter 9.
Where is bottom ash discharged in a furnace?
In the case of a continuous moving grate furnace, bottom ash is discharged at the bottom of the combustion chamber directly into a container, onto suitable conveyors, or into water for quenching. After cooling, some iron recovery can be attempted, since the ash usually contains 6–9% iron by weight.
Is flue gas treatment profitable?
Economics of flue gas treatment (general case of boilers) Investment in flue gas treatment can be profitable if the price difference between the substituted fuel and waste oil is high enough and if the boiler (or furnace) throughput is sufficiently large.
Can SNCR be combined with a gas burner?
SNCR can be combined with low-NO x burners or gas reburn. SNCR and gas reburn have comparable economics at the same level of NO x reduction; however, combining the two technologies considerably lowers cost while achieving a slightly higher NO x reduction. An example of annual costs, reported by Wu [ 30 ], are about $1,140, $1,120, and $730 per short ton NO x removed, respectively, for urea SNCR, gas reburn, and urea SNCR/gas reburn.
What is flue gas?
Flue gases are a mixture of combustion products including water vapor, carbon dioxide, particulates, heavy metals, and acidic gases generated from direct (incineration) or indirect (gasification and pyrolysis) oxidation of RDF or intermediate syngas.
How does flue gas affect water recovery?
With the increase of flue gas flow in a certain range, the water recovery volume increases, but the water recovery efficiency decreases. When the flue gas flow exceeds a certain value, all the membrane tubes in the membrane assembly are close to full load, and the water recovery tends to be stable. As the temperature of the flue gas increases, the temperature difference between the flue gas and the condensed water increases, the heat exchange is enhanced, and more water vapor in the flue gas condenses into water and is recycled, so the amount of water recycling increases and the recovery rate increases. The influence of temperature on water recovery decreases with the increase of flue gas flow.
How is flue gas composition affected by combustion?
Flue gas composition is significantly affected by the combustion conditions . Concentration of gaseous species upon firing 1.7% S coal (chemical composition is given in Table 1) was calculated at 1300 °C, assuming thermal equilibrium, and presented in Figure 2 as a function of air–fuel ratio. In this chapter, air–fuel ratio is defined by the ratio of their weights; air–fuel ratio of 10 represents combustion of 100 g fuel with 1000 g air. Where combustion takes place in complete or in air-excess conditions such as for the air–fuel ratio of more than 10, oxidizing gas species such as O 2, SO 2, and NO prevail. Complete combustion is termed here when carbon and hydrogen in fuel is totally oxidized to carbon dioxide and water vapor, and no additional oxygen is present in the flue gases. This corresponds to air–fuel ratio of 10 in Figure 2. In contrast, when combustion reactions proceed in air-deficient conditions where air–fuel ratio is less than 10, reducing gas species such as CO, H 2, and H 2 S replace the oxidizing gas species of O 2, SO 2, and NO. This is termed the partial combustion. Concentration of CO 2 and H 2 O is not significantly affected by the air–fuel ratio. Carbon dioxide and water vapor can coexist with oxidizing gas species of O 2 and SO 2 and reducing gas species of CO and H 2. Normally, from the point of combustion efficiency, fuel is fired in slightly air-excess conditions. Therefore, except at locations where equilibrium is not established, flue gas generally oxidizes the metal components. Partial combustion is encountered for gasification process of coal and residual oil. For these cases, flue gas, called synthetic gas (syngas) in some cases, is generally reducing, and contains gaseous H 2 S, resulting from sulfur in fuel. For some industrial boilers, slightly air-deficient combustion is favored at their furnaces, in order to minimize formation of gaseous nitrogen oxides. Gaseous H 2 S exists in the flue gases locally. Oxygen and sulfur partial pressures of these combustion gases are calculated as a function of air–fuel ratio at 1300 °C and presented in Table 3. As expected, low PO2 -high PS2 gas atmospheres are indicated upon combustion at low air–fuel ratio, whereas high PO2 –low PS2 gas atmospheres are characterized for combustion at high air–fuel ratio. Therefore, from the equilibrium point of view, corrosion environments for air-excess combustion are categorized as ‘oxidizing,’ while that for partial combustion as ‘sulfidizing’ when fuel contains considerable amounts of sulfur. The effect of temperature on flue gas composition upon combusting 1.7% S coal is basically minor for conditions of air-excess combustion ( Table 4 for air–fuel ratio of 12), but slight changes are noticed for conditions of partial combustion ( Table 5 for air–fuel ratio of 6).
What are the components of a flue gas?
Flue gases are a mixture of combustion products and include water vapour, carbon dioxide, particulates, heavy metals and acidic gases. Carbon monoxide and volatile organic compounds (VOCs) are also products of combustion, but they are indicators of incomplete combustion and can be easily monitored and rectified through process control ( Ares & Bolton, 2002). The main flue gas components are as follows:
What is the reaction of the absorbent solution in the flue gases?
Inside absorber tower, the absorbent solution reacts chemically with the carbon dioxide in the flue gases. The treated gases are vented to the atmosphere and CO 2 -rich solution leaves the bottom stage of absorber. The CO 2 -rich solution is entered into regeneration tower and is heated in a reboiler.
Why is it important to cool flue gases?
Shock cooling the flue gases limits the formation of dioxins/furans by so-called de novo synthesis. It also results in reduced volumetric flow rates , and therefore, it lowers demands on the flue gas cleaning system .
How are NOx emissions accelerated?
Starting from the combustion chamber, NOx emissions are accelerated by high-flame temperatures (e.g., by air preheat) and high excess air. 43 The NO x emissions can be reduced by:
What is the purpose of flue gas iso-enthalpic expansion?
This process is based on the flue gas iso-enthalpic expansion in order to bring these fumes into the presence of water at saturated conditions. Under these conditions, the cooled and saturated flue gases will be subjected to a series of treatments designed to transfer the pollution agents from the gas to the liquid phase. The purified gas phase might be discharged in accordance with regulations; the liquid phase must be treated either specifically or by returning the liquid phase to the plant inlet provided that this is an acceptable option.
How much reduction in NOx in a fluidised bed?
When the nature of the sludge or the operating conditions do not allow this limitation to be met, feedback has demonstrated that it is reasonable to expect a 50% reduction in NOx levels. When a 50% reduction is not enough for complying with statutory thresholds, an SCR solution must be implemented.
What are the neutralization reagents used in halogen and sulphur pollution?
Bicarbonate and lime are neutralisation reagents used on halogen and sulphur pollution; the powder adsorbant adsorbs volatile heavy metals, dioxins and furans. Given the dry reaction principle and the gas medium with short contact times, provisions must be made for extra reagents over and above the stoichiometry.
How is dust processed?
Dust is mainly processed by trapping it in water droplets that are violently agitated as the result of the venturi quench head loss. This head loss must follow the particle size curve for the duct concerned (figure 41 defines their typical domain). This curve defines a wash water flow obtained by internally recycling approximately 10 times the theoretical saturation flow rate (represented by the OC segment in figure 39).
Does ammonia remove nitrogen oxide?
Regardless of the systems described above, they will not remove pollution linked to nitrogen oxide (NOx). For this purpose, all processes use an ammonia solution that reacts with NOx according to the following general reaction :
Can purified gas be discharged?
The purified gas phase might be discharged in accordance with regulations; the liquid phase must be treated either specifically or by returning the liquid phase to the plant inlet provided that this is an acceptable option. Its operating principle is based on the wet air diagram (figure 39).
Do flue gases need to be cooled before going into the treatment line?
the flue gases have to be cooled before going into the treatment line; this cooling requirement is particularly stringent when bag filters are used; the excess reaction stoichiometry characteristic of the dry system represents a significant running cost.
How is flue gas treated?
At power plants, flue gas is often treated with a series of chemical processes and scrubbers, which remove pollutants. Electrostatic precipitators or fabric filters remove particulate matter and flue-gas desulfurization captures the sulfur dioxide produced by burning fossil fuels, particularly coal. Nitrogen oxides are treated either by ...
What is the largest part of the flue gas from fossil fuel combustion?
Since ambient air contains about 79 volume percent gaseous nitrogen (N 2 ), which is essentially non-combustible, the largest part of the flue gas from most fossil-fuel combustion is uncombusted nitrogen.
What is the smoke from a flue gas stack?
Much of the 'smoke' seen pouring from flue gas stacks is this water vapor forming a cloud as it contacts cool air. A typical flue gas from the combustion of fossil fuels contains very small amounts of nitrogen oxides (NOx), sulfur dioxide (SO 2) and particulate matter. The nitrogen oxides are derived from the nitrogen in ...
How are nitrogen oxides treated?
Nitrogen oxides are treated either by modifications to the combustion process to prevent their formation, or by high temperature or catalytic reaction with ammonia or urea. In either case, the aim is to produce nitrogen gas, rather than nitrogen oxides.
What is the gas that exits the atmosphere?
Flue gas. Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced at power plants.
Is coal flue gas higher than natural gas?
The total amount of wet flue gas generated by coal combustion is only 10 percent higher than the flue gas generated by natural-gas combustion (the ratio for dry flue gas is higher).
What Is Flue Gas ?
- As mentioned, flue gas is a by-product of burning fossil fuels. This gas exits the fireplace, furnace, boiler, or steam generator, via a pipe called a flue, entering the atmosphere. The composition of flue gas depends on the specific fuel that’s being burnt, but the main components include nitrogen dioxide, water vapor, carbon dioxide, and particul...
The Three Types of Flue Gas Treatment
- There are many industries with large industrial plants which need flue gas treatment. Due to the different nature of these industries and other such specifics, it’s important to pick the correct type of flue gas treatment. Changing times have brought about diversified and improved methods of treating flue gas. The following are the three main types of flue gas treatment, in which Sodimat…
Chemicals Used by Sodimate For Differents polluants
- As there are different processes that can be used to treat flue gas, there are also different chemicals that may be used. These include sodium sulphate , trona, lime, calcium carbonate, urea, sodium bicarbonate, and activated carbon. The specific chemicals to be used will depend on the process that is picked as well as the pollutants that need to be removed from the flue gas. It’s i…
General Equipment Used by Sodimate For Flue Gas Treatment
- The general equipment used for flue gas treatment by Sodimate is the dry sorbent injection flue gas cleaning system, PAC bulk bag discharger, Storage silo, Pneumatic conveying system. This leaves an easily disposable by-product that can be packed and transported safely and efficiently away from the site of incineration, leaving the environment that much cleaner. Contact Sodimat…
What Is Flue Gas?
The Three Types of Flue Gas Treatment
- There are many industries with large industrial plants which need flue gas treatment. Due to the different nature of these industries and other such specifics, it’s important to pick the correct type of flue gas treatment. Changing times have brought about diversified and improved methods of treating flue gas. The following are the three main types of flue gas treatment, in which Sodimat…
Chemicals Used by Sodimate For Different Pollutants
- As there are different processes that can be used to treat flue gas, there are also different chemicals that may be used. These include sodium sulphate , trona, lime, calcium carbonate, urea, sodium bicarbonate, and activated carbon. The specific chemicals to be used will depend on the process that is picked as well as the pollutants that need to b...
General Equipment Used by Sodimate For Flue Gas Treatment
- The general equipment used for flue gas treatment by Sodimate is the dry sorbent injection flue gas cleaning system, PAC bulk bag discharger, Storage silo, Pneumatic conveying system. This leaves an easily disposable by-product that can be packed and transported safely and efficiently away from the site of incineration, leaving the environment that much cleaner. Contact Sodimat…