TWI473644B - A method of recovering ammonia gas in an exhaust gas containing an organometallic or dust - Google Patents

Description

Method for recovering ammonia gas in exhaust gas containing organic metal or dust

The invention relates to a method for recovering ammonia gas in an exhaust gas containing organic metal or dust, in particular to recovering ammonia gas in an exhaust gas containing organic metal or dust by separating ammonia gas from organic metal or dust by an alkali washing program. The method.

In industries such as optoelectronic semiconductors or solar cells, the process of growing a semiconductor thin film on a substrate is mostly performed by Metal-Organic Chemical Vapor Deposition (MOCVD) or plasma-assisted chemical vapor deposition (Plasma-Enhanced). Chemical Vapor Deposition; PECVD) or Chemical Vapor Deposition (CVD), which produces organic metals in organometallic chemical vapor deposition or plasma-assisted chemical vapor deposition or chemical vapor deposition processes. Or dusty ammonia-containing exhaust gas, these ammonia-containing exhaust gases containing organic metals and dust can only be treated by pickling or wet washing, and the treated wastewater becomes metal oxide or metal hydroxide and has Acidic or alkaline ammonia-containing wastewater will have an impact on the environment.

In view of the above, an object of the present invention is to provide a method for recovering ammonia gas in an exhaust gas containing organic metals or dust to provide separation of ammonia gas from organic metal or dust by an alkali washing process to recover organic metal or dust. The method of ammonia gas in the exhaust gas solves the problem that the conventional technology fails to solve the problem that the treated waste water contains organic metal and dust The problem.

According to an object of the present invention, a method for recovering ammonia gas in an exhaust gas containing organic metal or dust is provided, which comprises the steps of: A. guiding an exhaust gas containing organic metal or dust and ammonia into a first space; B. applying a circulating alkali washing procedure to the alkali washing solution in the first space; C. separating the ammonia gas in the exhaust gas from the organic metal or dust in the exhaust gas in the circulating alkali washing procedure; D. collecting the above The ammonia gas separated in step C.

Wherein, the circulating alkali washing process first controls the pH value of the alkali washing solution to reach an alkaline preset value, and then performs a circulating alkali washing. The alkaline preset value of the circulating alkali washing solution is preferably pH 7 to pH 14, and the alkaline preset value of the circulating alkali washing solution is preferably pH 11 to pH 14.

The above C step controls the pH of the cyclic caustic washing process so that the ammonia gas is more easily separated as the pH value increases.

Wherein, the method for recovering ammonia gas in the exhaust gas containing organic metal or dust of the present invention further comprises an absorption step of the E step: absorbing the ammonia gas collected in the step D with any one of water, phosphoric acid and sulfuric acid .

The above-mentioned circulating caustic washing process is carried out at least once to improve the alkali washing efficiency.

The above absorption procedure is performed at least once to improve the absorption efficiency.

If the above absorption procedure is two or more times, the last absorption procedure A water washing or pickling process is further added to pickle the water mist derived from the absorption process or to remove the residual ammonia gas, thereby further reducing the content of the chemical substance in the treated exhaust gas.

Between the above-mentioned circulating caustic washing process and the absorption process, a water mist removing process is additionally performed to filter water droplets or water mist in the exhaust gas.

The circulating alkali washing process comprises a filtration process for filtering a metal oxide or a metal hydroxide solid produced by reacting an organic metal separated from a liquid with water, and a solid formed by dust in contact with water.

As described above, the method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention has the following effects:

(1) The method for recovering ammonia gas in an exhaust gas containing an organic metal or dust according to the present invention, the effect of separating ammonia gas and organic metal or dust is achieved by an alkali washing procedure.

(2) The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention, by controlling the pH value of the alkali washing solution to achieve the effect of controlling the degree of separation of ammonia gas from organic metal or dust.

(3) The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention, wherein the ammonia gas collected in step D is reacted with any one of water, phosphoric acid, and sulfuric acid to achieve reuse efficiency .

(4) The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention, which can reduce the solid form by adding a filtering device to the alkali washing process to achieve the effect of filtering out metal oxides or metal hydroxides and dust Blockage problems that may be caused by the alkaline washing process.

(5) A water mist removal procedure is additionally performed between the circulating caustic washing process and the absorption process, which can reduce the metal oxide or metal hydroxide and dust of the self-circulating alkaline washing process through the water mist or water droplets into the absorption process. The solids produced.

(6) The cyclic alkaline washing procedure can be carried out in more than one group of circulating alkaline washing equipment, for example, one, two or three groups, and the alkali washing efficiency can be improved by a plurality of circulating alkali washing procedures.

(7) The absorption procedure can be carried out in at least one or more of the absorption devices, for example, one, two, three or four groups, and the absorption efficiency can be improved by multiple absorption procedures.

(8) When performing multiple absorption procedures, a water washing or pickling procedure may be added to the last absorption program to pickle the water mist derived from the absorption process or pick up the residual ammonia gas. The chemical content in the treated exhaust gas is further reduced.

(21) ‧‧‧Organic metal chemical vapor deposition or plasma-assisted chemical vapor deposition

(22) ‧‧‧ pump unit

(23) ‧‧‧ Alkaline Wash Tower

(24)‧‧‧ absorption tower

(25) ‧ ‧ water wash tower or pickling tower

(31)‧‧‧ gas inlet

(32) ‧ ‧ alkaline washing solution

(33)‧‧‧

(34)‧‧‧Solid filter unit

(35) ‧ ‧ sprinkler head

(36)‧‧‧Reaction chamber

(37)‧‧‧Rasi ring

(38) ‧‧‧Water mist removal device

(39) ‧ ‧ gas exports

The first figure is a flow chart of an embodiment of the method of recovering ammonia gas in an exhaust gas containing organic metals or dust according to the present invention.

The second drawing is a diagram of an exhaust gas treatment procedure for a method of recovering ammonia gas in an exhaust gas containing an organic metal or dust according to the present invention.

The third figure is a schematic diagram of a recovery apparatus for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention.

The fourth figure is a flow chart of the first embodiment of the method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention.

Figure 5 is a flow chart showing a second embodiment of the method for recovering ammonia gas in an organic metal or dust-containing exhaust gas according to the present invention.

Please refer to the first figure, which is a flow chart of an embodiment of the method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention; the method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention comprises The following steps: A. directing the exhaust gas containing organic metal or dust and ammonia into the first space; B. applying the alkaline washing process to the alkali washing solution in the first space; C. making the ammonia gas in the exhaust gas In the circulating caustic washing process, it is separated from the organic metal or dust in the exhaust gas; D. collecting the ammonia gas separated in the above step C; E. reacting the ammonia gas collected in step D with any one of water, phosphoric acid and sulfuric acid. The substance undergoes an absorption reaction.

In the semiconductor process, a metal-organic chemical Vapor Deposition (MOCVD) or a Plasma-Enhanced Chemical Vapor Deposition (PECVD) process produces organic metals or dust and The exhaust gas of ammonia gas must be separated from the organic metal or dust and ammonia gas in advance to recover the exhaust gas, so that the exhaust gas containing organic metal or dust and ammonia gas is introduced into the first space of the reaction chamber.

The alkali washing solution is contained in the first space, and the alkali washing solution of the present invention is prepared by adding sodium hydroxide (NaOH) solution or calcium hydroxide (Ca(OH) ₂ ) to water, and the pH value of the alkali washing solution of the present invention is Between 7 and 14, preferably the pH is between 11 and 14.

The above-mentioned circulating alkaline washing procedure can also utilize the amount of ammonia gas in the exhaust gas to make the pH of the alkaline washing procedure between pH 7 and pH 14.

In the first space, the alkali-washing solution is used for circulating alkali washing of the exhaust gas containing organic metal or dust and ammonia gas, and the alkaline solution separates the hydroxide ion (OH ^- ion), thereby causing the following formula (1) The equilibrium of the reaction shifts to the left, the ammonia gas dissolved in the alkali washing solution is extremely small, and the organic metal or dust reacts with the alkali washing solution to produce a solid metal oxide or metal hydroxide or solid, thereby causing an alkali washing procedure. Organic metals or dust and ammonia are effectively separated.

NH _3(g) +H ₂ O ₍₁₎ →NH ₄ ⁺ _(aq) +OH ^- _(aq) Kb=1.8 x 10 ^-5 . (1)

After collecting the ammonia gas separated by the above cycle program, the ammonia gas is introduced into the second space (ie, the absorption space), and a reaction solvent is provided in the second space to combine with the ammonia gas to perform an absorption process, and the reaction solvent is water, Phosphoric acid and sulfuric acid are used, and the reaction is as shown in the following formulas (2), (3), and (4), and the produced ammonia water, ammonium sulfate, ammonium phosphate, and derivatives thereof can be used for other purposes. The ammonium sulfate produced by the method for recovering ammonia gas in the exhaust gas containing organic metal or dust according to the present invention can be used as a leather treatment agent, a water treatment agent, an adhesion promoter, a plating solution, and a chemical fertilizer.

NH _3(g) +H ₂ O _(aq) →NH ₄ OH _(aq) ......(2)

2NH ₄ OH _(aq) +H ₂ SO _4(aq) →(NH ₄ ) ₂ SO _4(aq) +2H ₂ O _(aq) ......(3)

1NH _3(g) +H ₃ PO _4(aq) →NH ₄ H ₂ PO _4(aq) ......(4)

The above absorption procedure can be carried out in one, two or three sets of absorption spaces in order to increase its absorption efficiency.

When there is more than one absorption space, the last absorption program can be added one more time. A water washing or pickling process to pickle the water mist derived from the absorption process or to remove the residual ammonia gas, thereby further reducing the chemical content of the treated exhaust gas.

Please refer to the second figure, which is a diagram of an exhaust gas treatment system for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention; an organometallic chemical vapor deposition method or a plasma assisted chemical vapor deposition unit (21) The generated exhaust gas containing organic metal or dust and ammonia gas is sent to the caustic scrubber (23) by the pump unit (22), where the separation process is performed, and the alkali washing solution is used to contain organic metals or dust and The ammonia exhaust gas is subjected to circulating alkali washing, and the organic metal or dust reacts with the alkali washing solution to produce a solid metal oxide or metal hydroxide, and the ammonia gas has low solubility in the alkaline solution, thereby circulating the alkaline washing program, organic Metal or dust and ammonia are effectively separated. The ammonia gas insoluble in the alkali washing solution is sent to the absorption tower (24) where it is combined with the reaction solvent, and the liquid obtained by the reaction such as ammonia water, ammonium sulfate, ammonium phosphate and derivatives thereof is a reusable product, and is absorbed. The water mist or the incompletely treated ammonia gas in the process enters the water washing tower or the pickling tower (25) for washing or pickling, thereby further reducing the chemical content in the treated exhaust gas.

Please refer to the third figure, which is a schematic diagram of a recovery device for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention; in the figure, the recovery device comprises a gas inlet (31) and an alkali washing solution (32). , pump (33), solid filter device (34), sprinkler head (35), reaction chamber (36), Raschig ring (37), water mist removal device (38), gas outlet (39). The organic metal or dust-containing exhaust gas produced by the organometallic chemical vapor deposition method or the plasma-assisted chemical vapor deposition method is introduced into the reaction chamber (36) from the gas inlet (31) and sprinkled with the shower head (35). The alkali washing solution (32) reacts, and the Raschig ring (37) disposed in the reaction chamber (36) can increase the connection of the alkali washing solution (32) with the exhaust gas. The contact area increases the reaction efficiency of the organometallic or dust with the caustic wash solution (32), and the organometallic or dust reacts with the alkali wash solution (32) to produce a solid metal oxide or metal hydroxide, such solid metal oxide or The metal hydroxide is retained in the alkali washing solution (32), and the alkali washing solution (32) is pressurized by the pump (33) and passed through the solid filtering device (34) so that the solid metal oxide or metal hydroxide is After filtration, the alkali washing solution (32) is sprayed on the spray head (35) by the solid filter device (34) to react with the exhaust gas newly entering the reaction chamber (36) to constitute a circulating alkali washing program. The ammonia gas in the exhaust gas which is not reacted with the alkali washing solution (32) is removed from the metal oxide or metal hydroxide which may be entrained in the water mist via the water mist removing device (38), and then sent to the absorption tower through the gas outlet (39). ) for subsequent processing.

In the above embodiments, the cyclic caustic washing procedure can be carried out in one, two or three sets of circulating caustic washing equipment to thereby increase the alkali washing efficiency.

Please refer to the fourth figure, which is a flow chart of a first embodiment of a method for recovering ammonia gas in an organic metal or dust-containing exhaust gas according to the present invention; an organometallic chemical vapor deposition method or a plasma assisted chemistry in the semiconductor industry The exhaust gas containing organic metal or dust generated by the vapor deposition process is firstly washed by the pump in the first alkali washing tower, and the second alkali washing is performed in the second alkali washing tower, in the third alkali The washing tower carries out the third alkaline washing, and the alkali washing efficiency is improved by three cycles of alkali washing to make the ammonia and the organic metal or dust have better separation efficiency, and the alkali can also be controlled by controlling the pH of the alkali washing solution. The washing efficiency is better. The exhaust gas after the completion of the circulating alkali washing process can first remove the water mist to reduce the metal oxide or metal hydroxide which enters the absorption process by the state of water mist or water droplets and the solid matter generated by the dust in contact with water. The exhaust gas is sent to the absorption tower and the reaction solvent for absorption reaction, and the liquid obtained by the reaction, such as ammonia water, ammonium sulfate, ammonium phosphate and derivatives thereof, is a reusable product, and the water mist derived from the absorption process is not completely treated. The gas is discharged by washing or pickling again to lower the content of the chemical substance in the treated exhaust gas.

Please refer to the fifth figure, which is a flow chart of a second embodiment of a method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to the present invention; an organometallic chemical vapor deposition method or a plasma assisted chemistry in the semiconductor industry The exhaust gas containing organic metal or dust generated by the vapor deposition process is firstly washed by the pump in the first alkali washing tower, and the second alkali washing is performed in the second alkali washing tower, in the third alkali The washing tower carries out the third alkaline washing, and the alkali washing efficiency is improved by three cycles of alkali washing to make the ammonia and the organic metal or dust have better separation efficiency, and the alkali can also be controlled by controlling the pH of the alkali washing solution. The washing efficiency is better. The exhaust gas after the completion of the circulating alkali washing process can first remove the water mist to reduce the metal oxide or metal hydroxide which enters the absorption process by the state of water mist or water droplets and the solid matter generated by the dust in contact with water. The exhaust gas is sent to the first absorption tower and the reaction solvent for the first absorption reaction, the second absorption column and the reaction solvent are subjected to the second absorption reaction, and the third absorption column and the reaction solvent are subjected to the third absorption reaction, and the third absorption reaction is carried out. Receiving the program, the ammonia gas contained in the exhaust gas is sufficiently reacted with the reaction solvent to obtain recyclable products such as ammonia water, ammonium sulfate, ammonium phosphate and derivatives thereof, and water mist derived from the multiple absorption process or not completely treated. The ammonia gas is discharged by washing or pickling again to lower the content of the chemical substance in the treated exhaust gas.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

Claims (10)

A method for recovering ammonia gas in an exhaust gas containing organic metal or dust, comprising the steps of: A. guiding an exhaust gas containing organic metal or dust and ammonia into a first space; B. in the first space Applying a caustic washing process to a caustic washing solution; C. separating the ammonia gas in the exhaust gas from the organic metal or dust in the exhaust gas in the circulating alkali washing process; D. collecting the ammonia gas separated by the above step C E. Absorption procedure: the ammonia gas collected in step D is subjected to absorption reaction with any of water, phosphoric acid and sulfuric acid; when the absorption procedure is more than two times, the last absorption procedure is further washed with water or acid. The washing process is performed by pickling the water mist derived from the absorption process or pickling the residual ammonia gas, thereby further reducing the content of the chemical substance in the treated exhaust gas. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to claim 1, wherein the circulating alkali washing program first controls the pH of the solution of the alkali washing solution to reach an alkaline preset value. Then carry out circulating alkali washing. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust as described in claim 2, wherein the alkaline pretreatment value of the circulating alkali washing solution is pH 7 to pH 14. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust as described in claim 2, wherein the alkaline pretreatment value of the circulating alkali washing solution is pH 11 to pH 14. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust as described in claim 1, wherein the C step controls the pH of the circulating alkali washing process, so that ammonia gas is more easily increased with the pH value. Is separated. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust as described in claim 1, wherein the cyclic caustic washing process is performed at least once to improve the alkali washing efficiency. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to claim 1, wherein the circulating alkali washing program and the absorption program comprise a water mist removing program for filtering out the exhaust gas. Water mist or water droplets. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to claim 1, wherein the circulating alkali washing step in the step B is to introduce NaOH or Ca(OH) ₂ as a reactant to make the cycle. The pH of the caustic wash solution is between pH 7 and pH 14. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to claim 1, wherein the circulating alkali washing procedure in step B uses the amount of ammonia gas in the exhaust gas to make the pH value of the alkali washing program From pH 7 to pH 14. The method for recovering ammonia gas in an exhaust gas containing organic metal or dust according to claim 1, wherein the circulating alkali washing program comprises a filtering program for filtering the organic metal and water separated from the exhaust gas. The metal oxide or metal hydroxide solid produced by the reaction, and the solid produced by the dust and the alkali washing solution.