- •G. Zayonchkovsky, V. Stadnychenko, y. Golovko «hydraulic machines and hydraulic/pneumatics equipment»
- •Introduction
- •Pump glossary
- •1.2 Pump history
- •1.3 Pump family group
- •1.3.1 Centrifugal pumps
- •1.3.2 Reciprocating pumps
- •1.3.3 Pump selection
- •2.1 Centrifugal pumps
- •2.2 Centrifugal pump characteristics
- •2.3 Performance modifications for varying pipelene applications
- •2.3.1 Cavitation
- •2.3.2 Net positive head
- •2.3.3 Net Positive Suction Head Avaible
- •2.3.4 Net Positive Suction Head Required
- •2.3.5 Correcting for Inadequate Suction Conditions
- •2.3.6 Npsha-nphsr Criteria
- •2.3.7 Viscous Liquids
- •2.3.8 Minimum Flow
- •2.3.9 Temperature Rise
- •2.3.11 Centrifugal Pump Station Piping Design
- •2.3.12 Centrifugal Pump Nozzle Loading
- •2.3.12 Pump Operational Hazards and Risk
- •3.1. Rotary
- •3.2 Types of rotary pumps
- •3.3 Reciprocating pumps
- •3.4 Piston pumps
- •4.1 Role of compression in a gas pipeline network
- •4.2 Gas pipeline hydraulics principles
- •4.3 Friction factor
- •4.4 Flow regimen profiles calculation
- •4.4 Pipeline design and optimization
- •4.4.1 Optimization Parameters
- •Optimization Process Overview
- •4.4.3 Selection of Alternative
- •4.4.4 Sensitivity Analysis
- •4.4.5 Pipeline Looping & Compression (Location & Spacing)
- •Hydraulics Simulations
- •4.4.7 Compressor Operation Costs
- •5.1. Pneumatic piping, hoses and connections
- •5.2 Flow control and pressure regulation valves
- •5.3 Relief valves dynamics
- •6.1 Linear actuators
- •6.2 Construction
- •6.3 Mounting arrangements an cylinder dynamics
- •7.1 Station piping layout
- •7.2 Scrubbers and filters
- •7.2.1 Dry scrubbers
- •7.2.1 Wet scrubbers
- •Categorization of wet scrubbers
- •Advantages and disadvantages
- •7.2.3 Filters
- •7.3 Gas coolers
- •7.4 Absorbers and regenerators
Categorization of wet scrubbers
Since wet scrubbers vary greatly in complexity and method of operation, devising categories into which all of them neatly fit is extremely difficult. Scrubbers for particle collection are usually categorized by the gas-side pressure drop of the system. Gas-side pressure drop refers to the pressure difference, or pressure drop, that occurs as the exhaust gas is pushed or pulled through the scrubber, disregarding the pressure that would be used for pumping or spraying the liquid into the scrubber.
Scrubbers may be classified by pressure drop as follows:
Low-energy scrubbers have pressure drops of less than 12.7 cm (5 in) of water.
Medium-energy scrubbers have pressure drops between 12.7 and 38.1 cm (5 and 15 in) of water.
High-energy scrubbers have pressure drops greater than 38.1 cm (15 in) of water.
However, most scrubbers operate over a wide range of pressure drops, depending on their specific application, thereby making this type of categorization difficult.
Another way to classify wet scrubbers is by their use - to primarily collect either particulates or gaseous pollutants. Again, this distinction is not always clear since scrubbers can often be used to remove both types of pollutants.
Wet scrubbers can also be categorized by the manner in which the gas and liquid phases are brought into contact. Scrubbers are designed to use power, or energy, from the gas stream or the liquid stream, or some other method to bring the pollutant gas stream into contact with the liquid. These categories are given in Table7-1.
Table 7-1.
Categories of wet collectors by energy source used for contact
Wet collector |
Energy source used for gas-liquid contact |
Gas-phase contacting Liquid-phase contacting Wet film Combination
|
Gas stream Liquid stream Liquid and gas streams Energy source:
|
Advantages and disadvantages
For particulate control, wet scrubbers (also referred to as wet collectors) are evaluated against fabric filters and electrostatic precipitators (ESPs). Some advantages of wet scrubbers over these devices are as follows:
Wet scrubbers have the ability to handle high temperatures and moisture.
In wet scrubbers, flue gases are cooled, resulting in smaller overall size of equipment.
Wet scrubbers can remove both gases and particulate matter.
Wet scrubbers can neutralize corrosive gases.
Some disadvantages of wet scrubbers include corrosion, the need for entrainment separation or mist removal to obtain high efficiencies and the need for treatment or reuse of spent liquid.
Table 7-2 summarizes these advantages and disadvantages. Wet scrubbers have been used in a variety of industries such as acid plants, fertilizer plants, steel mills, asphalt plants, and large power plants.
Table 7-2
Relative advantages and disadvantages of wet scrubbers compared to other control devices
Advantages |
Disadvantages |
Small space requirements Scrubbers reduce the temperature and volume of the unsaturated exhaust stream. Therefore, vessel sizes, including fans and ducts downstream, are smaller than those of other control devices. Smaller sizes result in lower capital costs and more flexibility in site location of the scrubber. No secondary dust sources Once particulate matter is collected, it cannot escape from hoppers or during transport. Handles high-temperature, high-humidity gas streams No temperature limits or condensation problems can occur as in baghouses or ESPs. Minimal fire and explosion hazards Various dry dusts are flammable. Using water eliminates the possibility of explosions. Ability to collect both gases and particulate matter |
Corrosion problems Water and dissolved pollutants can form highly corrosive acid solutions. Proper construction materials are very important. Also, wet-dry interface areas can result in corrosion. High power requirements High collection efficiencies for particulate matter are attainable only at high pressure drops, resulting in high operating costs. Water-disposal problems Settling ponds or sludge clarifiers may be needed to meet waste-water regulations. Difficult product recovery Dewatering and drying of scrubber sludge make recovery of any dust for reuse very expensive and difficult. |