Gas Properties And Treatment Methods Of Lime Kiln

Lime kilns are important equipment in lime production, which works by breaking down limestone into quicklime and carbon dioxide through high temperatures. However, in the production process of lime kiln, there will be a lot of flue gas, which contains a lot of harmful substances, causing serious impacts on the environment and human health. Therefore, how to deal with lime kiln smoke and reduce its impact on the environment has become an important environmental protection issue.

Properties of flue gas in lime kiln production

First, we need to understand the properties of lime kiln smoke. Limekiln flue gas is mainly composed of carbon dioxide, carbon monoxide, nitrogen oxide, sulfur oxide, particulate matter, and so on. Among them, carbon dioxide and carbon monoxide are the main greenhouse gases, which have an important impact on global warming. Nitrogen oxides and sulfur oxides are the main air pollutants, which cause serious harm to human health and the environment. Particulate matter can cause air quality to deteriorate and harm the human respiratory system. In general, there are the following characteristics:

lHigh moisture content

The moisture of raw limestone and coal is about 5%, and the drying in the preheating section will produce the corresponding water steam, and the dew point will be as high as 60℃-70℃. When the flue gas temperature is lower than the dew point temperature, dew will easily occur in the pipeline and dust collector, resulting in a paste bag.

lHigh temperature

In actual production, the flue gas will be controlled within the range of 200℃, with a certain fluctuation of the feeding cycle, the temperature is too low will cause condensation, the temperature is too high will cause energy waste, and in special cases, the material will be cut off as high as 350℃.

ldusty

The type, characteristics, and degree of drying of materials are different, so the size of the dust content in the flue gas will also be different.

lSulfur dioxide present

There is sulfur dioxide in the flue gas of lime kiln production, and the humid environment will corrode the equipment and filter material. Most of the sulfur dioxide comes from burning coal with a high sulfur content.

Flue gas treatment method

1. Washing method:

The washing method is to dissolve the harmful substances in the flue gas in the water by spraying the liquid, and then remove the harmful substances dissolved in the water through precipitation, filtration, and other steps. This method can effectively remove particles and some harmful gases in the flue gas, but the treated wastewater needs to be further treated, otherwise it will cause secondary pollution to the environment.

2. Adsorption method

The adsorption method is through the use of adsorbent, the harmful substances in the flue gas are adsorbed on the adsorbent, and then through regeneration or incineration and other steps, the harmful substances adsorbent on the adsorbent are removed. This method can effectively remove nitrogen oxides and sulfur oxides from the flue gas, but the service life of the adsorbent is limited and it needs to be replaced regularly.

3. Desulfurization and denitrification technology

This is an advanced flue gas treatment technology, which can remove nitrogen oxides and sulfur oxides in the flue gas at the same time. This method mainly includes wet desulphurization and dry desulphurization, wet desulphurization is the flue gas through the desulphurization solution so that the flue gas nitrogen oxides and sulfur oxides react with the desulphurization solution to produce sulfate and nitrate; Dry desulfurization is through the catalyst, the nitrogen oxides and sulfur oxides in the flue gas react with oxygen to produce sulfur dioxide and nitrogen.

4. Electric dust removal technology

electric dust removal technology is through a high voltage electric field, so that the particles in the flue gas are charged, and then through the effect of electric field force, the charged particles are adsorbed on the electrode plate to achieve the purpose of removing particles. This method can effectively remove particles in the flue gas, but the energy consumption is high.

Because mixed-fired lime shaft kiln belongs to low-temperature combustion, under normal circumstances nitrogen oxides are within the normal range, exhaust gas treatment only needs dust removal desulfurization, dust removal is generally used cyclone dust collector and bag pulse dust collector can be, desulfurization is generally commonly used double alkali desulfurization, lime, and sodium alkali (Na2CO3 or NaOH) as desulfurization agent, The desulphurization solution is circulated outside the tower. After flue gas treatment, particulate matter ≤10mg/Nm3 and sulfur dioxide ≤50mg/Nm3 meet the standard emission standards. The desulfurized in the pool is recycled after precipitation and regeneration, and the sediment is gypsum, which is filtered by the plate and frame filter press and used as building materials