Loading...

Wednesday, January 15, 2020

Adding Limestone is One Way to Reduce SOx Emission From Coal Combustion

Abstract

If we are using higher sulfur content fuel, i.e. Coal then we requires to mix the higher amount of Lime Stone to reduce the SOx. It depends upon the requirement for desulfurization. If we are mixing higher amount of Limestone then we get high amount of Calcium Oxides (CaO). It will help to desulfurize higher Sulfur or Sulfur dioxides (SO₂). So it is most important to know the amount of Calcium Oxides (CaO) present in the lime stone that we are using. Lower the Calcium Oxides (CaO) will increases the Lime stone consumption.

1. INTRODUCTION

SOx emission control is most essential requirement in today scenario because High concentrations of sulfur dioxide (SO₂) can result in breathing problems with asthmatic children and adults who are active outdoors.

Apart from health hazard it is very harmful for environment because Sulfur dioxide and nitrogen oxides are the major precursors of acid rain, which has acidified soils, lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility.

Sources of SOx emission from combustion of fuel containing sulfur -- mostly coal and oil and also produced during metal smelting and other industrial processes.

So control in SOx emission is most essential for Environmental aspect & also as per Govt. Pollution control board rules & regulation it must not exceed 100 PPM. To control the same it need to Desulphurises the Sulphur present in Fuel which is used in various Industries basically at Thermal Power plant in Boiler as a combustible material.

2. STATEMENT OF PROBLEM

Health Effects: High concentrations of sulfur dioxide (SO₂) can result in breathing problems with asthmatic children and adults who are active outdoors. Short-term exposure has been linked to wheezing, chest tightness and shortness of breath. Other effects associated with longer-term exposure to sulfur dioxide, in conjunction with high levels of particulate soot, include respiratory illness, alterations in the lungs' defenses and aggravation of existing cardiovascular disease.

Environmental Effects: Sulfur dioxide and nitrogen oxides are the major precursors of acid rain, which has acidified soils, lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility. Sulfur dioxide also is a major precursor of fine particulate soot, which poses a signifi- cant health threat.

Sources: Combustion of fuel containing sulfur -- mostly coal and oil. It is also produced during metal smelting and other industrial processes.

So control in SOx emission is most essential for Environmental aspect & also as per Govt. Pollution control board rules & regulation it must not exceed 100 PPM.

3. DEFINITION OF TERMS

3.1 Sulphur (S)

Sulphur is a constituents of fuel found from its ultimate analysis about 1% to 8% as per quality of fuel. Basically Pet coke having higher sulfur percentage which is a byproduct of Pe- troleum refinery. Sulfur reacts with oxygen to produce sulfur dioxide (SO₂) & sulfur trioxide (SO₃).

Molar mass: 32.065 gm/mol
Formula: S
Melting point: 115.2°C

3.2 Sulfur dioxide (SO₂)

Sulfur dioxide is the chemical compound with the formula SO₂. It is a toxic gas with a pungent, irritating smell that is re- leased by volcanoes and in various industrial processes.

Molar mass: 64.066 gm/mol
Formula: SO₂ Density: 2.63 kg/m³
Boiling point: -10 °C
Melting point: -72 °C

3.3 Sulfur Trioxide (SO₃)

Sulfur trioxide is the chemical compound with the formula SO₃. In the gaseous form, this species is a significant pollutant, being the primary agent in acid rain. It is prepared on massive scales as a precursor to sulfuric acid.

Formula: SO₃
Molar mass: 80.066 gm/mol
Density: 1.92 gm/cm³
Melting point: 16.9 °C

3.4 Sulfuric Acid (H₂SO₄)

Sulfuric acid is a highly corrosive strong mineral acid with the molecular formula H₂SO₄. It is a pungent-ethereal, colorless to slightly yellow viscous liquid which is soluble in water at all concentrations.

Formula: H₂SO₄
Density: 1.84 gm/cm³
Molar mass: 98.079 gm/mol
Melting point: 10 °C
Boiling point: 337 °C
IUPAC ID: Sulfuric acid

3.5 Calcinations Process

The process of heating a substance to a high temperature but below the melting or fusing point, causing loss of moisture, reduction or oxidation, and dissociation into simpler sub- stances. The term was originally applied to the method of driving off carbon dioxide from limestone to obtain lime (calcium oxide). Calcinations is also used to extract metals from ores.

3.6 Desulfurization Process

It the process of removing sulfur from flue gas by using wet process, Semi-dry process or Dry process.The reaction be- tween the SO₂ and the alkali can take place either in bulk solu- tion (‘wet’ FGD processes) or at the wetted surface of the solid alkali (‘dry’ and ‘semi-dry’ FGD processes).

4. THEORY INVOLVED

For proper Desulfurization process the desulfurising agent (lime stone) is required as per the sulfur content in the fuel used.

5. CALCULATION

Input data sheet

5.1 Sulfur percentage in Coal

The below mentioned data is taken from analysis of coal in laboratory:


5.2 Limestone parameter

The below mentioned data is taken from analysis of coal in laboratory:


5.3 Molecular weight of some Molecules


5.4 Calculation Sheet

The reaction of Sulfur with Lime stone for desulfurization is occurs after the calcinations process as:

5.4.1 Calcinations reaction @ 600 °C to 750°C temperature


5.4.2 Desulfurization reaction @ 700 °C to 850 °C temperature


From above reaction we can get how many grams of CaO &  O₂ are required to desulfurization of sulfur.

We get 0.875gms of CaO & 0.25gms of O₂ required to desulfu- rization of 1gm of sulfur Dioxide (SO₂) and produce 2.125gms of CaSO₄.

5.5 Output Sheet

From above reaction it is found that 1 gm of Sulfur dioxide (SO₂) required 0.875 gms of CaO and therefore 1 gm of Sul- fur(S) required 1.75 gram of CaO.

On the same way we can find out the requirement of desulfu- rization agent are as mentioned below:


On the same we calculated the requirement of Desulfurization agent for different type of fuel, i.e. Coal:


From above table we found if sulfur content in coal is higher than we have to mix higher ratio of lime stone to reduce the SOx level.

6. CONCLUSION

From the above calculation we found that if we are using higher sulfur content fuel, i.e. Coal then we requires to mix the higher amount of Lime Stone to reduce the SOx. It depends upon the requirement for desulfurization.

If we are mixing higher amount of Limestone then we get high amount of Calcium Oxides (CaO). It will help to desulfurize higher Sulfur or Sulfur dioxides (SO₂).

So it is most important to know the amount of Calcium Oxides (CaO) present in the lime stone that we are using.

Lower the Calcium Oxides (CaO) will increases the Lime stone consumption.

Source: Sudam Padhan, Ritesh Kumar

Advertisement

The 10 largest coal producers and exporters in Indonesia:

  1. Bumi Resouces
  2. Adaro Energy
  3. Indo Tambangraya Megah
  4. Bukit Asam
  5. Baramulti Sukses Sarana
  6. Harum Energy
  7. Mitrabara Adiperdana 
  8. Samindo Resources
  9. United Tractors
  10. Berau Coal

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...