Scrubbing liquid is a solution that reacts with the contaminants so as to neutralize its effects. The scrubbing liquid used differs based on the applications. Usually the scrubbing liquid used is water.
Wet scrubbers are effective air pollution control devices for removing particles and/or gases from industrial exhaust streams. A wet scrubber operates by introducing the dirty gas stream with a scrubbing liquid typically water. Particulate or gases are collected in the scrubbing liquid.
Scrubbing system are designed to protect environment from the harmful chemical gases that are released from the industrial process. Magnetic drive pumps are used in the scrubbing system to circulate the gas-liquid through the recycling process and treatment system.
Centrifugal magnetic drive pumps are more suitable for industrial chemical recirculation and chemical transfer. Efficient Scrubber pumps can generate a maximum flow of 200 CFM per minute.
This is a cross-flow design with scrubbing liquid flowing vertically downwards while the gas passes horizontally through the packing section. Horizontal Packed Bed Scrubber is used when limited headroom is an issue at a customer’s facility or when low profile is desired for roof-top applications. Multiple stages can be easily provided in one housing with separate sumps and pumps if required.
Chemical scrubbers are a common odor control technology. Chemical scrubbers can remove up to 99.5% of hydrogen sulfide and ammonia, even at high concentrations.
Usually chemicals such as sodium hypochlorite and sodium hydroxide is used in the solution to oxidize hydrogen sulfide. The oxidation reactions are dependent on pH, with the optimum scrubber solution pH being in the 9.5 – 10.5 range.
Smokestack scrubbers are used as air pollution control devices that remove harmful particles, gases, or chemical byproducts from industrial exhaust streams. These emissions control devices use liquid or chemicals to remove particulate matter or gases from industrial exhaust and flue gases. Atomized liquid (generally water) catches and entrains pollutant gases and harmful particles, turning them into slurry waste streams which will then need to be recycled or disposed of.
These units have the ability to remove gases, mists, and solids simultaneously. They can act as a cooling mechanism for the exhaust stream.
An alkaline limestone slurry reacts with acidic sulfur dioxide. As flue gas passes through the scrubber and is contacted by the limestone slurry sprays, sulfur dioxide absorbs into the liquid. When SO2 is introduced to water, a pH depression occurs.
First the gas enters into the vessel and reaches the bottom and the scrubbing liquid is sprayed upward in the scrubber. The gas collides with the liquid flow. When the momentum of the liquid and the gas gets balanced it falls back into the vessel. The gas that moves out pass though series of internal packing where the remaining liquid droplets gets removed and the purified air exits the tower.
Tail gas scrubbing includes a quench and a stack for processing gases from sulfuric acid plant. Usually the tail gas scrubbing system is used for the processing of fumes from sulfuric acid plants. Caustic acid is used for scrubbing. Double Alkali regeneration system is used for the regeneration of caustic that is used for scrubbing.
Pollutant is a substance which causes pollution to the environment. Pollutants are also referred to as contaminants. Pollutants can be broadly classified into liquid, solid & gaseous pollutants.
Liquid Pollutants includes Oil spills, Liquid Pesticides, Detergents, Petroleum products such as gasoline, diesel, kerosene and Chemical wastes such as acids, bases etc.
The function of fuel gas scrubber is to remove 99% of liquid and to entrain liquid droplets of size 10 microns and larger.
The dust laden air flows through the filter media. This filter media helps in removing solid wastes. The remaining liquid is passed through the high efficient mist eliminator. The liquids from the mist eliminator are collected and removed from the gas stream.
Quench Scrubber is a wet packed bed scrubber that can be considered as an low cost alternative to incineration scrubber.
It consists of a quench section and a scrubbing section. This is designed so as to avoid the condensation of water that is quenched from the flue gas in the scrubbing section. The scrubbing agent used in the packing helps in removing SOX, NOX etc.
Scrubber Packing Material
Scrubber packing material is made from heat resistant and chemical corrosion resistant plastics, including polyethylene (PE), polypropylene (PP), reinforced polypropylene (RPP), polyvinyl chloride (PVC), chloridized polyvinyl chloride and polyvinylidene fluoride (PVDF).
Packings have features such as high void ratio, low pressure drop, low mass-transfer unit height, high flooding point, uniform gas-liquid contact, high mass transfer efficiency. The application temperature in media ranges from 60º C to 150º C. Because of these reasons it is widely used in the packing towers in petroleum industry, chemical industry, coal gas industry and environmental protection, etc.
It is a widely-practiced chemical process and is also known as amine gas treating, gas sweetening and acid gas removal. It is a commonly used in oil refineries, natural gas processing plants and other natural gas producing regions.
Amine scrubbing refers to a number of commercial technologies that use various alkanolamines to remove acidic components such as hydrogen sulfide and from gas streams.
Exhaust gas purification systems can reduce harmful exhaust gases by up to 95%. The exhaust gas purification system consists of three consecutive stages
- The soot filter
- The selective catalytic reduction process for reducing the oxides of nitrogen (NOx)
- The oxidation catalyst process for catalytic combustion of CO and un-burnt hydrocarbons.
Vent Gas Scrubber System is a compact, light-weight and easy-to-install unit designed for economical and effective control of pollution from low volume sources. Vent Gas Scrubber System is compact and provides efficient scrubbing solution for small gas flows from lab hoods, storage tanks, and small industrial pilot plant equipment.
Gas Scrubbing is used to remove the liquid droplets from the gas stream. This is designed to handle light liquid loads. They are effectively designed to remove the gas pollutants and chemicals such as sulfur, ammonia or chlorine.
Jet Venturi Scrubber is designed to entrain and scrub gases without the use of complicated baffles or moving parts.
The scrubbing fluid used is usually water. It leaves the nozzle in a hollow cone spray. This creates a draft which draws the gases and vapors into the moving stream. Here they are continuously scrubbed so as to meet the required efficiency.
Principles of Operation
It uses a well atomized scrubbing liquid stream to entrain contaminated gas stream.
High Liquid/Gas ratio and surface area provided by the atomized liquid provides effective absorption of toxic gases.
Large number of small droplets provides efficient capture of particulate upto 2 micron size.
Typical Operating Parameters
Liquid/Gas Ratio = 40 – 100 gpm/1000 cfm
Spray Nozzle Pressure Drop = 15 – 100 psi
Suction Draft = 0 – 3” w.c.
Scrubber Water Treatment
Scrubber Wastewater cannot be simply flushed down the drain. This waste water may contain salts such as sulfates, chlorides and carbonates. Less volume of waste water can be handled by using evaporator drums and large volumes of water can be handled by using thermal evaporator.
Rotary Scrubbers are used to wash crushed rock, ore, sand, gravel, construction aggregates and oil sands. They are high-capacity, high-retention machines that can accept large-sized feed material and are used primarily to remove water soluble clays, deleterious materials and coatings from a wide variety of hard rock and ore.
Industrial Fume Scrubber System is used for the removal of harmful acidic fumes and dust from the exhaust of various industrial process. Fume scrubbing system are used in industries such as chemical production, semiconductor manufacturing, metal finishing and other processes that involves in the emission of fumes and dust. The materials used for the construction of the scrubber is MS , SS or FRP/.
- Chrome Plating
- Zinc Plating
Natural Gas Scrubber are specially designed to remove the suspended liquids and dirt from the pipelines in natural gas extraction process. Compressed natural gas scrubber are used for high pressure dispenser applications such as coalescing liquid from natural gas.
- Removes 0.01 micron sized oil, water, and dirt particles with 99.99% efficiency.
- Continuously trap and drain liquids and removes all trace oil vapor with carbon adsorbent cartridges.
- Flow ranges upto 70,000 CFM.
The water supply is sprayed from the nozzles with the help of the pump onto the packed bed. The water droplets gets atomized and so the intake of the contaminant increases. The droplet size increases due to inertia. The exhaust air is passed through another packed bed thereby reducing the contaminants further more. In the last process the remaining contaminants gets washed out completely and the Apzem’s Exhaust Air scrubber works with 99.99% efficiency.
Dry Scrubber system utilizes dry adsorption techniques to separate pollutant acid gases from exhaust air stream. These scrubbers are mainly used to remove acid gases from combustion sources. This removal of acid gases is done by using a series of dry reactants that on reaction exhausts gas at high speeds and thus neutralizing the pollutants in the gas.
Wet scrubbers relay on the liquid spray to remove dust particles from the gas stream. It is also for the fume absorption and so very useful in fume extraction systems. It removes air pollutants by inertia of diffusion impaction, reaction with absorbent or reagent slurry or absorption into a liquid solvent. The inlet gas stream usually enters the bottom of the tower and moves upward, while liquid is sprayed downward from one or more levels.