With the increasingly stringent requirements of environmental protection regulations, the process based on the baking soda dry deacidification principle developed by Perlman in conjunction with advanced European and American processes has been increasingly used. Various pollutants contained in flue gas are removed by dry adsorption using sodium bicarbonate as adsorbent. Its purification effect is comparable to other known methods, such as the spray adsorption method using lime milk as the adsorbent. Dry flue gas purification can not only be used in coal power plants, hazardous waste treatment, municipal waste or alternative fuel incineration plants, but can also be widely used in industrial furnaces in glass, cement, metallurgy and other industries. Dry flue gas purification can economically remove gases containing acidic substances, such as SO2, HCI, etc., and meet the national flue gas emission standards.

Flue gas contains a large amount of acidic gases. After a large amount of data and experiments, it has been found that only when sodium bicarbonate (baking soda, NaHCO3) is small enough to a certain extent, can it react with the acidic components in the flue gas with maximum efficiency. It removes acidic pollutants in flue gas through chemical adsorption, and can also remove some inorganic and organic trace substances through physical adsorption. This process sprays sodium bicarbonate fine powder directly into high-temperature flue gas. At high temperatures, sodium bicarbonate decomposes to produce sodium carbonate Na2CO3, H2O and CO2.

Typically, with flue gas temperatures between 140 and 250 °C, a slight excess of sodium bicarbonate (stoichiometric factor between 1.1 and 1.3) is usually sufficient due to the high activity of the sodium bicarbonate adsorbent.

The particle requirements are related to the components in the flue gas. For the removal of SO2 and HCl, the required particle sizes will be different. Due to transportation and storage reasons, sodium bicarbonate raw materials are usually coarse particles (d50 value is about 200 microns). To achieve higher reactivity, the adsorbent must have a larger specific surface area. Therefore, sodium bicarbonate must be ground to a certain fineness before being injected into the flue gas pipeline. For example, to remove SO2, the fineness of sodium bicarbonate must reach d90 < 20 μm. The removal of HCl only requires d90 < 35 μm. If the system is operated correctly, more than 95% of SO2 can be removed; the HCl removal rate can even reach 99%. In order to maintain the required fineness of sodium bicarbonate in long-term operation, after grinding with an air grinder, the adsorbent is usually transported by gas transportation and directly introduced into the flue gas pipeline through multiple nozzles to ensure that it is evenly dispersed within the pipeline. . This equipment has a simple and durable design, and its investment and operating costs are lower than other flue gas purification methods.

The sodium bicarbonate grinding process will be the core process of this technology.

CAM-H negative pressure air grinder

In this process, sodium bicarbonate is quantitatively supplied from the raw material bin to the downstream CAM-H series air grinder through a variable frequency screw conveyor. The amount of adsorbent required can be calculated from the pollutant concentration trend curve before and after desulfurization. Install a rotary valve between the screw conveyor and the grinder to isolate the air flow to prevent the air flow from affecting the quantitative feeding of the screw conveyor. After sodium bicarbonate is ground in a classifying mill, the fine powder is transported to the flue gas pipeline by a material conveying fan.

working principle

Sodium bicarbonate enters the CAM air classifying mill through a weightless spiral feeding scale and is fed quantitatively and uniformly. The high-speed rotating grinding block collides with the ring gear and is crushed under various forces such as friction and shearing. After being crushed, it enters the classification area with the air flow. Qualified materials enter the flue through the classification wheel for reaction, and the coarse materials fall into the crushing area to continue crushing. The size of the particles can be obtained by adjusting the size of the classification wheel.