PP washing tower

A PP scrubber (also known as a PP water scrubber) is an exhaust gas purification device primarily made of polypropylene (PP). It is primarily used to treat dust, acidic and alkaline gases, and organic waste gases in industrial waste gases. Its operating principle and structure are as follows:

I. Operating Principle
The PP scrubber operates on the principle of gas-liquid contact absorption, purifying waste gas through a physical or chemical reaction between a liquid (absorbent) and pollutants in the waste gas. The specific process is as follows:

1. Exhaust Gas Intake: Pollutant-laden exhaust gas enters the tower through the lower air inlet, driven by a fan, and flows upward along the tower's internal channels.

2. Absorbent Spraying: The spray system at the top of the tower (consisting of a water pump, piping, and nozzles) pressurizes the absorbent (selected based on the properties of the pollutant, such as clean water, alkaline solution, or acidic solution). The pressurized absorbent is then atomized into fine droplets through the nozzles and evenly sprayed downward, forming a "liquid curtain." 3. Gas-Liquid Contact Reaction: Rising exhaust gas fully contacts the descending atomized droplets, resulting in purification.
- Physical Reaction: Dust particles are adsorbed by the droplets and settle with the liquid; water-soluble gases (such as ammonia) are directly absorbed.
- Chemical Reaction: Acidic and alkaline gases are neutralized by their corresponding absorbents (such as sulfur dioxide reacting with sodium hydroxide solution to form salt).
4. Gas-Liquid Separation: The purified gas rises to the top of the tower, where it passes through a demister (such as a baffle or mesh) to remove entrained droplets, preventing secondary contamination. It is finally discharged through the outlet in a standard manner.
5. Waste Liquid Treatment: The waste liquid that has absorbed pollutants is collected in a sump at the bottom of the tower and can be recycled (with the addition of absorbent) or discharged after treatment.

II. Structural Description
The PP scrubber is primarily constructed of PP (acid- and alkali-resistant, lightweight) and consists of the following components:

1. Tower Body: A cylindrical or square, sealed container, serving as the core space for the reaction between exhaust gas and absorbent. It is typically equipped with a packing layer (such as Pall rings, hollow balls, or Raschig rings) to increase the gas-liquid contact area.

2. Air Inlet and Outlet: The air inlet is located at the bottom of the tower body and connects to the exhaust gas delivery pipeline; the air outlet is located at the top of the tower and connects to the exhaust pipe.

3. Spray System: This includes a circulating water pump, spray piping, and atomizing nozzles (such as spiral nozzles and fan nozzles) responsible for evenly distributing the absorbent.

4. Packing Layer: Located in the middle of the tower body, this layer consists of inert fillers that extend gas-liquid contact time and improve purification efficiency.

5. Demister: Installed at the top of the tower, before the air outlet, it separates liquid droplets from the gas to prevent loss and environmental contamination. 6. Liquid Collection Tank: Located at the bottom of the tower, it collects waste liquid after spraying and is typically equipped with a level gauge and a drain outlet.
7. Circulation Pipe and Valve: Connects the liquid collection tank to the spray system, enabling the recycling of absorbent. Some systems also have a reagent addition port.

The PP scrubber has a simple structure and is easy to operate, making it suitable for treating low- and medium-concentration waste gases in industries such as chemical processing, electroplating, printing and dyeing, and coating.