Washing Tower Waste Gas Treatment Equipment

Working Principle of Waste Gas Washing Tower

Washing tower, also known as spray tower, consists of tower body, tray, reboiler and condenser. Washing towers are equipment for rough separation, so the number of trays is generally small, usually not more than 10 grades. The scrubber is suitable for the separation of mixed gases containing a small amount of dust. The components will not react, and the products are easy to liquefy, and the impurities such as dust are not easy to liquefy or solidify.

When the mixture gas enters the scrubbing tower from the middle part of the scrubbing tower, because there is liquid product component between the trays, the vaporizing part of the product component gas liquefies at the same time, while the impurities can not be liquefied or solidified, when passing through the tray with liquid component, the liquid product component will be fixed and produce washing effect. The scrubbing tower is designed and manufactured according to this principle.

The principle of scrubbing tower is to use strong acid (sulfuric acid), strong alkali (sodium hydroxide), strong oxidant (sodium hypochlorite) as washing spray solution to contact odor molecules in the gas, so that odor components in the gas phase can be transferred to the liquid phase, and odor substances can be removed by neutralization and oxidation reaction of chemical agents with odor components.

The commonly used washing equipment is packed tower. Chemical absorption liquid sprays downward from the top of the tower, exhaust gas flows upward, odor and absorption liquid are fully contacted and reacted, thus being removed. The ratio of absorbent liquid to waste gas flow (liquid/gas ratio) is generally 1-3 L/m3, the height of packing is generally 2-5 m, and the velocity of empty gas column is generally 0.5-1 m/s. The deodorization effect of the packed tower with good operation can reach more than 90%.

Chemical Absorbents Used in Waste Gas Scrubbing Towers

1) alkaline solution

Sodium hydroxide solution containing 1%~10% is commonly used in alkaline absorption solution, which has a remarkable effect on eliminating hydrogen sulfide waste gas. Other substances, such as methyl mercaptan, methyl sulfide, methyl disulfide and low-grade fatty acid, often cause odor in wastewater treatment plant, and the treatment effect is also remarkable.

2) Acidic solution

Acid washing is mainly used to eliminate the odor caused by alkaline gases such as ammonia and trimethylamine. Sulfuric acid (0.5% - 5% solution) is generally used as the washing liquid.

3) Sodium hypochlorite solution

Sodium hypochlorite is usually used with acid-base absorbent solution. For methyl sulfide which is difficult to eliminate by other methods, the control effect of sodium hypochlorite absorbent solution is very good.

When dealing with high concentration odor, the concentration of sodium hypochlorite solution (effective chlorine concentration) is about 500-2000 ppm, while when dealing with low concentration odor, the concentration of sodium hypochlorite solution is about 50-500 ppm. Sodium hypochlorite is the cheapest and most effective oxidant, so it is widely used. Sodium hypochlorite in solution exists in the form of hypochlorite (HOCl):

NaOCl+ H2O→HOCl+ NaOH

At pH=7.5, the available chlorine in hypochlorite solution exists in 50% HOCI and hypochlorite ion (OCl-).

At pH=l0, only 0.3% of available chlorine exists in HOCl.

At pH=l1 or 12, HOCl almost completely dissociates into useless hypochlorite ions, so pH control is very heavy.

 Physical drawings of spray scrubber

Performance characteristics of waste gas scrubber

1) Washing tower treatment system is cheap and simple.

2) Vertical structure is most suitable for economic space installation.

3) Suitable for gaseous and liquid pollution sources;

4) Treatment of a single source of pollution;

5) Suitable for medium and low wind volume;

 Scope of application of waste gas scrubbing tower

1) The treatment of various harmful gases such as H2S, SOx, NO x, HCI, NH3, CI2, etc.

2) Deodorization devices in waste transfer stations and sewage treatment plants;

3) Exhaust treatment of semiconductor optoelectronic industry;

4) Treatment of leachate from landfill and waste gas from storage tank;

5) Waste gas treatment from incinerators and industrial furnaces.

 Large Washing and Spraying Device

 System parameters of waste gas scrubber

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