what is a Venturi washing equipment?

what is a Venturi washing equipment?

Venturi washing equipment (Venturi washer)

It belongs to high-energy wet scrubbing and dust removal equipment, commonly used for high-temperature flue gas dust removal and cooling, and can also synergistically absorb some acidic waste gases (SO ₂, HCl, etc.).

Main structure of Venturi washing equipment

The whole system is divided into four parts: Venturi tube body, gas-liquid dehydration separator (cyclone dehazing), water circulation system, and induced draft fan
Three sections of the Venturi tube body:
1. Shrinkage tube (tapered section): the flow cross-section is reduced, and the airflow is accelerated; Spray washing water into this or the throat position
2. Throat (throat, core section): with the smallest flow cross-sectional area and an airflow velocity of 50-80 m/s; High speed airflow cuts and crushes water into extremely fine water mist; Intense collision and mixing of air dust water, dust is captured and condensed by water droplets
3. Diffusion tube (gradually expanding section): The flow cross-section expands again, the airflow slows down, the static pressure rises, and small dust droplets continue to condense and grow

There are also adjustable throat types: built-in adjustable cone, changing the cross-sectional area of the throat to adapt to fluctuations in flue gas flow and maintain dust removal efficiency; The fixed throat is a simple and conventional model.
A cyclone dehydrator (cyclone dehazing) must be installed afterwards to separate the gas containing water mist into gas and water; After purification, the gas is discharged outside; Dusty wastewater enters the circulating sedimentation tank for treatment and reuse.

Working principle of Venturi washing equipment (three-step process)

1. Atomization: High temperature dusty flue gas enters the contraction section for acceleration; The washing water is sprayed into the throat and is strongly impacted and crushed by high-speed airflow, forming a large amount of fine water mist;
2. Condensation: High speed turbulence at the throat, where dust particles adhere to water mist droplets through inertial collision and interception; The flow velocity in the diffusion section decreases, and small droplets containing dust collide and condense into large droplets;
3. Dehydration and separation: The gas-liquid mixture is sent to the cyclone dehydrator; Separate dust droplets from the airflow by relying on centrifugal force; Clean flue gas is discharged, and sewage is discharged or circulated.

Main classification of Venturi washing equipment

1. Fixed throat Venturi washer: throat size is fixed; Suitable for stable flue gas flow conditions; Low cost; The efficiency decreases significantly when the air volume fluctuates.
2. Adjustable throat Venturi washer (adjustable cone): By moving the cone core through the actuator, the throat flow area can be dynamically changed; When the flue gas load changes (20-100%), maintain stable throat gas velocity and dust removal effect; Higher cost, slightly more complex maintenance, and more commonly used in metallurgical furnaces.
3. Self suction jet type Venturi scrubber: relying on high-pressure water jet to suction flue gas, without the need for induced draft fan; Suitable for small and medium air volumes; Energy consumption is concentrated on the high-pressure water pump.

Advantages of Venturi washing equipment

1. Good removal effect of fine dust: the dust removal efficiency for 0.1-5 μ m fine dust can reach 95-99%; Can handle high concentration dusty flue gas;
2. Combined with rapid cooling: High temperature flue gas can quickly cool down; The presence of Martian smoke can extinguish Mars and reduce the risk of dust explosions; Suitable for smelting furnaces and incineration flue gas;
3. Can wash and absorb acidic harmful gases simultaneously; Replacing the washing solution can achieve simple desulfurization;
4. Simple structure, no filter material consumables; The land area is relatively small; Can handle sticky dust (pay attention to preventing scaling).

Disadvantages of Venturi washing equipment

1. High pressure loss! The system pressure drop is usually 25-80 mbar (250-80mmHg ₂ O), the fan power consumption is high, and the operating electricity cost is high;
2. When producing washing wastewater, it must be accompanied by sewage treatment and sedimentation; Easy to cause scaling and wear on the inner wall; The throat area is severely eroded and worn, requiring wear-resistant lining;
3. The absorption and residence time of gaseous pollutants is very short, and their desulfurization and denitrification capabilities are limited. Generally, they are only treated and cannot be used as the main desulfurization equipment alone;
When the back-end dehydration and defogging fail, the exhaust will carry a large amount of water mist and white tail.

Typical application scenarios of Venturi washing equipment

-Steel metallurgy: purification of blast furnace gas, steelmaking converter flue gas, and dust removal and purification of electric furnace flue gas (very classic applications)
-Nonferrous smelting and refractory material kilns;
-Flue gas rapid cooling and dust removal pretreatment for incinerators and hazardous waste rotary kilns;
-Chemical waste gas treatment; Wet purification of flue gas from high-temperature kilns for some organic fertilizers and building materials;
Attention: If the backend is equipped with a desulfurization tower, the Venturi is often placed in front for rapid cooling and pre dust removal to reduce the dust load on the subsequent tower body.

Reference for Key Process Parameters of Venturi Washing Equipment (Engineering Selection)

-Throat flow velocity: 60-75 m/s (commonly used design range);
-Liquid gas ratio (water consumption): 0.7-1.5 L/m ³;
-System pressure drop: 300-700 Pa (fixed throat); Adjustable throat high-energy type can reach 700-1000 Pa;
-Material selection: ordinary carbon steel lining with wear-resistant and anti-corrosion coating; 304/316L stainless steel is selected for corrosive flue gas; Fiberglass reinforced plastic is used for strong corrosion conditions.