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  Method and apparatus for processing inorganic acidic gasUSPTO Application #: 20060100090Title: Method and apparatus for processing inorganic acidic gas Abstract: A method for treating waste gas containing inorganic acid is disclosed. The method includes the following steps: (a) forming a mixture of inorganic acidic gas and a nebulized alkaline solution wherein the nebulized alkaline solution can be produced continuously or periodically; (b) forcing the mixture to pass through an adsorbent bed; and (c) releasing the treated gas. An apparatus for treating the inorganic acid gas with the method illustrated above is also disclosed here. The method can regenerate poisoned adsorbents online, and save time, space and cost simultaneously. (end of abstract) Agent: Bacon & Thomas, PLLC - Alexandria, VA, US Inventors: Keh-Perng Shen, Li-Ting Wang USPTO Applicaton #: 20060100090 - Class: 502025000 (USPTO) Related Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Regenerating Or Rehabilitating Catalyst Or Sorbent, Treating With A Liquid Or Treating In A Liquid Phase, Including Dissolved Or Suspended, Using Salt Or Alkaline Substance The Patent Description & Claims data below is from USPTO Patent Application 20060100090. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention is related to one method and apparatus for processing waste gas; more particularly, one method and apparatus for processing waste gas containing inorganic acid. [0003] 2. Description of Related Art [0004] Due to a huge amount of inorganic acids (mainly hydrochloric acid, hydrofluoro acid, sulfuric acid, and nitric acid) being used in the semi-conductor industry to process wafer washing with acid or etching, the manufacturers discharge waste gas and waste water that contain inorganic acids, which cause very serious pollution of the environment. Traditionally, the packed wet scrubber is commonly used to process the removing of inorganic acidic gas. During the process of gas cleaning, a huge amount of washing solution is sprayed on the packing so as to have the effect of gas-liquid contacting and removing inorganic acidic gas. Although the packed scrubber generally includes demister for removing droplets in the tail gas, it is difficult to avoid very small droplets being carried along the airflow. Utilizing a demister may retain the droplets of the tail gas, yet the retained droplets easily accumulate on top of the demister. During long-term operation, there is still small amount of inorganic acidic gas discharged along with the tail gas due to the washing solution itself or the retained droplets reaching the vapor-liquid equilibrium. [0005] Presently, the existing devices of inorganic acidic wet scrubbers in the semi-conductor industry all have difficulty in achieving the requirement of 95% elimination rate. This environmental problem that the semiconductor industry faces is as the same as the problem needing to be solved in other high-tech industries such as the TFT-liquid crystal display industry. [0006] These kinds of exhausts containing inorganic acid are generally treated in the wet scrubber by adding alkaline solution to absorb or wash the inorganic acid. Gas phase pollutants (inorganic acidic gas) dissolved in the liquid phase quickly form ions through acid-base neutralization. Thus, resistance of mass transfer from the gas phase to liquid phase is not produced. However, due to the concentration of inorganic acidic pollutants manufactured in semi-conductors and photoelectric devices being not high, the driving force for mass transfer (difference of concentrations) in the gas phase is not significant. Thus it is not able to produce greater diffusion mass transfer through the difference of concentrations between the gas phase and gas-liquid interface. Therefore, the traditional wet scrubber designed utilizing the two-film theory in chemical engineering has a poor efficiency in processing low concentration (<10 ppmv, specifically <5 ppmv) inorganic acidic exhausts. [0007] There is no preferred method for processing the aforementioned low-concentration inorganic acidic gas, however, there have been a few techniques developed to avoid the drawbacks of the aforementioned wet scrubber. One is to utilize wet active carbon to adsorb sulfur dioxide (SO.sub.2) and hydrogen chloride (HCl) in waste gas. SO.sub.2 absorbed in the active carbon will be catalyzed and converted to sulfuric acid (H.sub.2SO.sub.4), and then washed by water. The exhausted H.sub.2SO.sub.4 solution will be concentrated and again infused into the active carbon bed. HCl absorbed in the active carbon will then replace by the concentrated H.sub.2SO.sub.4 solution. Wet scrubber and alkaline solution will then absorb and wash HCl. Another technique infuses hydroxide of alkali metal or carbonate into active carbon. Drying under high temperature (120 to 160.degree. C.) is employed to make the potassium concentration of the active carbon increase to 5.9.about.9.4%, and under such circumstances it has the ability to absorb SO.sub.2 and hydrogen cyanide (HCN). Also another technique proposes that active carbon with 20.about.30 wt % calcium can remove gas containing chlorine or sulfur. However, the above-mentioned techniques have not mentioned the processing method for low concentration (<10 ppmv, especially <5 ppmv) inorganic acidic gas, nor the regeneration method of active carbon when its absorbency has been depleted. [0008] In absorbent reuse relating techniques, there is one item of equipment for processing hydrogen sulfide gas in a wastewater treatment plant. The equipment utilizes an active carbon bed after being immersed in a sodium hydroxide solution as the adsorbent. The adsorbent bed has a thickness of 3 ft. When the adsorbability of the active carbon bed has been depleted, it requires an additional spare active carbon bed to alternatively function on-line, while the regeneration of adsorbability of active carbon bed is processed off-line. That is, the technique requires the active carbon bed to be offline for regeneration. Thus the stated equipment is not favorable for application in limited space. Moreover, the regeneration of the adsorbent bed requires five to fifteen days. In addition, the active carbon bed can only be regenerated for three to four times, resulting in short use life of the adsorbent. [0009] It is therefore in great need to provide a long-term and stable method and apparatus for processing inorganic acidic gas to solve the problems of low concentration inorganic acidic gas in photoelectric device and semiconductor manufacturing. SUMMARY OF THE INVENTION [0010] The present invention discloses a regenerative de-acid apparatus for inorganic acidic gas, comprising: a tank having an gas inlet and an exhaust outlet; at least one adsorbent bed having one adsorbent, wherein the adsorbent bed is received inside the tank; at least one alkaline solution supply unit that is placed inside the tank and providing at least one alkaline solution to the at least one adsorbent bed; and at least one washing solution supply unit, positioned inside the tank and providing a solution for washing the at least one adsorbent; wherein the alkaline solution supply unit is placed between the adsorbent bed and the gas inlet. [0011] The present invention also provides a regeneration method of adsorbent for processing inorganic acidic gas, comprising the following steps: (a) washing an adsorbent with a washing solution; and (b) spraying or immersing a nebulized alkaline solution to the adsorbent. [0012] The present invention also discloses a method for processing inorganic acidic gas, comprising the following steps: (a) forming a mixture of inorganic acidic gas and a nebulized alkaline solution wherein the nebulized alkaline solution can be produced continuously or periodically; (b) forcing the mixture to pass through an adsorbent bed, wherein the said adsorbent is washed by water, or sprayed or immersed by alkaline solution; and (c) releasing the treated gas. [0013] The present invention further discloses a regenerative de-acid system for inorganic acidic gas, comprising: a piping having plurality of branch pipe each with an opening; and a plurality of regenerative de-acid apparatuses for inorganic acidic gas. Each regenerative de-acid apparatus comprises: a tank having an gas inlet and an exhaust outlet; at least one adsorbent bed, which is received inside the tank and includes an adsorbent; at least one alkaline solution supply unit, which is received inside the tank and provides at least one alkaline solution to the at least one adsorbent bed; and at least one washing solution supply unit, which is received inside the tank and provides a solution for washing the at least one adsorbent; wherein the alkaline solution supply unit is positioned between the adsorbent bed and the gas inlet; and each gas inlet of the tank connects to an opening of the branch tubing. [0014] The applications of the regenerative de-acid system for inorganic acidic gas according to the present invention are not restricted, and can be applied in prior inorganic acidic gas processing. The piping of the present invention may connect to prior apparatus for processing inorganic acidic gas, such that the piping of the present invention may connect to the exhausting port of the inorganic acidic gas in the wet scrubber. Also, the wet scrubber of the present invention can be any prior wet scrubber, but preferably is a Venturi scrubber, packed scrubber for vapor-liquid co-current, vapor-liquid counter-current, or vapor-liquid crossflow, spray scrubber or other scrubbers with the same effect. [0015] The apparatus and method of the present invention can deal with inorganic acidic gas with any concentration, even with low concentration. The apparatus and method of the present invention preferably deal with inorganic acidic gas with a concentration lower than 5 ppmv, and the efficiency is as high as 95%. [0016] The regenerative de-acid system according to the present invention can simultaneously install multiple sets of regenerative processing apparatus for inorganic acidic gas. Thus the adsorbent bed can directly be regenerated in situ on-line, whereby the prior expense for exchanging depleted adsorbents can be therefore eliminated. Also the processing time and the space occupied for manufacturing can be reduced. Moreover, regionally spraying, showering, or immersing in clean water or hot water at set time washes and removes the salts produced in acid-base neutralization. Thus it is not required to stop production to change the depleted adsorbent. The system will be maintained quite stable for a long time and provide high efficiency for processing low concentration inorganic acidic gas, thereby solving the environmental problems of traditional wet scrubbers in photoelectric device and semiconductor industries. [0017] The alkaline solution used in the method disclosed in the present invention can be any prior alkaline solution, but preferably is potassium hydroxide solution, sodium hydroxide solution or their mixture. The concentration of the alkaline solution is not restricted, but preferably is with a weight percentage more than 5 wt %. The weight percentage more than 15 wt % is even better. The weight percentage more than 25 wt % is the second best concentration, while saturated concentration of 90% is the best choice. The diameter of the tiny droplet produced by nebulization of the alkaline solution is approximately smaller than 2 mm. The diameter of the droplet is preferably smaller than 500 .mu.m, while it is better to be smaller than 100 .mu.m. The best droplet diameter is smaller than 50 .mu.m. [0018] The adsorbent bed used in the present invention can be of any prior thickness, but a thickness ranging from 1 cm to 60 cm is good. Further, a thickness ranging from 2 cm to 45 cm is better, while a thickness ranging from 2 cm to 30 cm is the best. [0019] The present invention deals with any prior inorganic acidic gas, but preferably deals with hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or mixtures of any two of the aforementioned inorganic acidic gas. [0020] The water used to dissolve the salt crystal in the present invention can be any prior water, but preferably is de-ionized water with temperature higher than 20.degree. C., pure water processed by reverse osmosis, distilled water, tap water, or mixed solution of any two of the aforementioned waters. [0021] The adsorbent used in the present invention can be any prior adsorbent, but preferably is selected from spherical active carbon, granular active carbon, pulverized active carbon, active carbon fabric, zeolite adsorbent, or mixtures of any two of the aforementioned materials with adsorbability. [0022] The regenerative de-acid apparatus according to the present invention can further be installed with multiple functional units depending on the need to improve its function. It is preferably to install one valve, which closes when one washing solution clearis one adsorbent, on each gas inlet to prevent contamination. Continue reading... Full patent description for Method and apparatus for processing inorganic acidic gas Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for processing inorganic acidic gas patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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