FUME EXTRACTION SYSTEM
Wet Scrubbing System
Effective Fume Extraction Systems for Industrial Processes
Before air pollution regulations mandated control of toxic gas emissions, industries recognized the need to manage acidic gas emissions from their operations. Wet scrubbers emerged as crucial devices for capturing acidic gases by absorbing them into a liquid solution, typically water or a water-based mixture. This process significantly reduces the residual acidic gas in the emitted stream, mitigating environmental risks.
The scrubbing liquid contains reactive agents that neutralize absorbed acids, making the liquid effluent from the scrubber easier to manage in wastewater treatment facilities. Preventing these emissions is crucial to averting environmental and health hazards. Corrosive acidic gases can cause severe damage to infrastructure and pose immediate health risks upon contact with humans.
Caramet Technologies designs advanced wet scrubbing systems that effectively treat acidic and alkaline gases from various industrial processes. Our proven techniques ensure compliance with environmental standards while safeguarding surrounding communities and ecosystems.
Key Benefits of Caramet’s Wet Scrubbing Systems:
- Efficient Acidic Gas Removal: Captures and neutralizes acidic gases effectively.
- Environmental Compliance: Meets stringent regulatory requirements for emissions control.
- Community Safety: Minimizes health risks associated with harmful gas exposure.
- Versatile Applications: Suitable for diverse industrial and process applications.
Contact Caramet Technologies today to learn more about our innovative wet scrubbing solutions for your industrial needs.
Industrial Application of Scrubbing System
By far the most common non-sulphurous acid gas emitted by industry is hydrogen chloride (HCl). As with many acidic gases, sources of HCl vary widely. A common source is the exhaust during the filling or “breathing” of holding or storage tanks. These tanks generally contain up to 35% to 36% aqueous HCl solution. Many chemical processes emit HCl, and the emissions may be with or without other toxic gases and at different concentrations. In addition, combustion processes in which chlorinated substances are thermally oxidized emit HCl. Under many circumstances, HCl is scrubbed using an ejector Venturi gas scrubber. An ejector venturi gas scrubber is an “eductor”-type design. It makes use of the scrubbing liquid as the motive fluid to pull the gas stream into and through it without the need of another device, such as a fan, to move the gas. The liquid and gas streams thoroughly mix, and the HCl transfers from the gas phase to the scrubbing liquid phase. A single-stage ejector venturi gas scrubber can typically achieve 95 percent HCl removal. A counter current packed tower is used to achieve even higher HCl removal efficiencies, up to and exceeding 99.9 percent, if necessary. This device is a vertical tower in which the scrubbing liquid flows downward counter current to the upward gas flow over a bed of packing pieces that function primarily to provide a surface area on which the two streams come into contact.
To neutralize the HCl, it is very common to use an aqueous sodium hydroxide (NaOH) solution as the scrubbing fluid. The reaction between NaOH and HCl produces sodium chloride (NaCl), otherwise known as ordinary table salt. On the other hand, if the HCl is relatively concentrated in the gas stream, it may be practical to recover most of the HCl in aqueous solution, which can then be reused or sold. To accomplish this, a multiple stage system is usually required, consisting of one or more ejector venturi gas scrubbers and a packed tower as the final stage. HCl solution is re circulated as the scrubbing fluid in the initial stages, typically absorbing and recovering more than 90 percent of the HCl. The final stage may then utilize aqueous NaOH to meet low-ppm discharge concentrations exiting the packed tower. This arrangement not only saves most of the cost of the NaOH, but also may generate a salable product.
Generally speaking, the methods described above for scrubbing HCl would also apply to hydrogen fluoride (HF). However, because of HF’s vapor pressure characteristics, the probability of recovering it in a usable or salable form is lower than that for HCl.
While NaOH solution can also be used to scrub and neutralize HF, the product of HF and NaOH is sodium fluoride (NaF), which has limited solubility in water. Therefore, it is usually more practical to neutralize HF with potassium hydroxide (KOH) solution. In that case, the product of its reaction with water is potassium fluoride (KF), which is very soluble in water. Hydrogen bromide and hydrogen iodide Again the methods just described for scrubbing HCl would apply to the acidic gases hydrogen bromide (HBr) and hydrogen iodide (HI). However, their chemical properties make them somewhat more difficult to scrub than HCl or HF. Although scrubbing these gases can be very effective, knowledge of their mass transfer characteristics and the chemistry of their neutralization is important for successful design of treatment equipment. Also, the recovery of these acidic gases in a usable or salable aqueous form is very unlikely.
Chlorine (Cl2) is scrubbed in a counter current packed tower using aqueous NaOH solution. The resulting products are NaCl and sodium hypochlorite (NaOCl), which is a bleaching agent. NaOCl is stabilized in the scrubbing solution by being maintained at relatively high alkalinity. When the presence of NaOCl is undesirable, chemical additives can be used in the scrubbing solution. Scrubbing with water alone is impractical because of the very limited solubility of Cl2 in water. An ejector venturi gas scrubber may be useful for Cl2 scrubbing in cases of high Cl2 gas concentrations. But a single-stage ejector venturi gas scrubber is seldom used because its performance is limited.
Counter current packed tower designs are generally used for scrubbing bromine (Br2) and fluorine (F2) using aqueous alkali solutions to achieve optimum removal efficiencies. As with other acidic gases, if the concentrations of Br2 or F2 are high, an ejector venturi scrubber may be used as a first stage to absorb the bulk of the acid gas, with a packed tower polishing stage to follow. Specifically for F2 scrubbing, it is very important to maintain adequate levels of excess alkali (typically NaOH or KOH) to eliminate the generation of certain undesirable by-products. As with HF scrubbing, KOH is the preferred scrubbing reagent because the product of neutralization is considerably more soluble in water than when NaOH is used.
Hydrogen cyanide (HCN) is usually scrubbed with an aqueous solution of NaOH. The methods used are similar to those described for HCl scrubbing. Recovery as a usable by-product is not practical. Also, in some cases, the addition of NaOCl to the scrubbing solution is used to increase removal performance or to produce more desirable reaction products
Scrubbing nitric acid (HNO3 ) is very similar to scrubbing HCl. Not only are the methods the same, but there is also good potential for recovering aqueous HNO3 in a usable form in those applications in which high concentrations exist in the gas stream and other contaminants are not present that might contaminate the product. However, in some processes that produce HNO3 , nitrogen oxides (NOx ) are also produced. The effective scrubbing of NOx is much more complicated than acid gas scrubbing. It depends greatly upon which species is present, if mixed species are present (which often occurs), at what absolute levels they exist, and at what relative levels they exist. Nonconventional and special proprietary methods of scrubbing are often required.
NOx is produced in a variety of different processes, including combustion equipment, gas turbines, incinerators, kilns and power plants. NOx also is emitted as by product from many metal treatment processes where nitric acid is used as an oxidant. Plating or catalyst recovery involves the reaction of nitric acid and transition metals also forming NOx. Substantial amounts of NOx also can be generated in the specialty chemical industry when nitric acid is used as a reagent.
Essentially, NOx contains nitric oxide and nitrogen dioxide in varying proportions. This fluctuating ratio, and the fact that these compounds exhibit quite different properties when contacted with water (as would occur in a wet scrubber) complicate the treatment of NOx. NO2 gas has fairly high solubility and reactivity to water and in aqueous solutions or alkalis as compared with NO, and can be removed by wet scrubbing. On the other hand, gaseous NO is only slightly soluble in water and is not very reactive with typical aqueous solutions.
We use counter current type Packed bed scrubber to scrub the NOx fumes emitting from Various scources.
Hydrogen sulfide (H2S) is a corrosive gas that can corrode and damage, even in trace quantities. The produced H2S can react with water vapor present in the biogas producing hydrosulfuric acid that can be further oxidized to sulfuric acid, which can cause corrosion. Hydrogen sulfide is also toxic to living organisms under certain concentrations and can result in range of adverse health effects. The US Occupational Safety and Health Administration (OSHA) lists the acceptable ceiling concentration for human exposure to H2S to be 20 ppm for an 8-h duration. In some industrial sectors, the total weighted average exposure limit is 10 ppm over 8 h. The acceptable peak concentration above the ceiling concentration is 50 ppm, but for a maximum time limit of 10 min. Concentrations exceeding 500 ppm in a closed environment can lead to death within 30–60 min, while concentrations exceeding 1000 ppm is instantly fatal. Combustion of H2S also leads to SOx emissions, which has harmful environmental effects.
Caramet has designed an effective Scrubbing system for Hydrogen Sulfide Gas emitting from different industries.
Sulfur dioxide (SO2) is a corrosive gas that is created by the oxidation of sulfur-bearing materials such as coals, oil, and natural gas. While it has long been deemed desirable to limit the concentration of SO2 in combustion gases that are released to the atmosphere. SO2 emission is a particularly acute problem in the electric power-generating industry where large quantities of coal are burnt.
We design a sodium-based scrubbing solutions, such as sodium hydroxide in water, have a great affinity for SO2.
Seawater is a source of natural alkalinity that can be used economically to arrest SO2 from flue gas without the use of any other supplemental reagents. Seawater contains significant concentrations of alkaline ions including sodium, magnesium, potassium, calcium, carbonates, and bicarbonates. It also contains significant concentrations of chloride and sulphite ions. Desulfurization is accomplished by seawater scrubbing, and 90% SO2 removal efficiency could be achieved by adopting this process.
Caramet has designed an effective Scrubbing system for SOx gas.
Various scrubbing processes have been proposed to remove CO2 from the flue gases. Caramet has designed Scrubbing processes based on sodium hydroxide. The CO2 is absorbed into solution, transferred to lime via a process called causticization. Several minerals and mineral-like materials reversibly bind CO2. Most often, these minerals are oxides or hydroxides, and often the CO2 is bound as carbonate. Carbon dioxide reacts with quicklime (calcium oxide) to form limestone (calcium carbonate), in a process called carbonate looping. Other minerals include serpentinite, magnesium silicate hydroxide, and olivine.
Ammonia (NH3) is easily scrubbed using Venturi, Packed Bed Scrubbers. Although ammonia is highly soluble in water, recirculating an aqueous NH3 solution cannot generally be used for scrubbing. Aqueous NH3 solutions are characterized by relatively high NH3 vapor pressures that prevent the mass transfer of NH3 from gas to liquid phase. Commonly NH3 is scrubbed with an aqueous acid solution. Sulfuric acid or phosphoric acid is often chosen because of their own relatively low vapor pressure. However, nitric acid can also be used and does generate a potentially usable product for agricultural use. Amines are also scrubbed with aqueous acids. However, amines tend to be more difficult to scrub then ammonia. The characteristics of the particular amine (solubility in water, reactivity with acid, etc.) determine how successful or difficult the scrubbing will be.
Caramet has designed an effective Scrubbing systems for Ammonia and amines for different industries.