JP2000233116A - Method and apparatus for recovering ammonia from waste gas of wastewater stripper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover ammonia which does not contain hydrogen sulfide by fixing hydrogen sulfide gas in water by allowing aqueous ammonia to react by neutralization with hydrogen sulfide in the waste gas by a method wherein water is injected into a gas coming out from an ammonia scrubber tower crest, and the aqueous ammonia to be generated is refluxed to the scrubber. SOLUTION: Waste gas exhausted from an ammonia stripper B is continuously forcibly sent to an ammonia scrubber 2 via piping 1. Then, a BFW pipe 4 is connected on the way of an airpipe 3 arranged to a tower crest of the scrubber 2, BFW(boiler feed water) are injected into a waste gas, and the mixture is sent into a reflux drum 6 from the airpipe 3 via an indirect cooler 5. Besides, the whole amount of a liquid remaining in the reflux drum 6 is refluxed to the scrubber 2, aqueous ammonia is allowed to react with hydrogen sulfide in the waste gas to generate ammonia salt, and the hydrogen flufide is fixed in the liquid. Further, a liquid containing an ammonia salt is extracted from a liquid feed pipe 9, and the liquid is returned to a hydrogen fulfide stripper A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recovering ammonia from a waste gas containing ammonia and hydrogen sulfide discharged from a wastewater treatment device of a petroleum refinery.

[0002]

2. Description of the Related Art Waste gas containing ammonia and hydrogen sulfide discharged from a wastewater treatment system of a petroleum refinery is subjected to a combustion treatment by pumping it to a heating furnace for oil refining or a boiler,
Alternatively, it is processed by pumping into a Claus method reactor of a sulfur recovery unit. In the latter treatment method, hydrogen sulfide is turned into a resource by converting hydrogen sulfide to elemental sulfur as compared with the former treatment method. Oxidized into substances and released into the atmosphere. This nitrogen oxide is one of the pollutants causing environmental pollution, and is particularly responsible for the generation of photochemical smog.

[0003]

In the above conventional treatment method, the ammonia contained in the waste gas from the wastewater treatment device of the petroleum refinery is burned, and a part of the ammonia is released into the atmosphere as nitrogen oxides. . Therefore, there is a problem in that ammonia is not turned into a resource, but causes the generation of substances that pollute the environment.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an ammonia scrubber by refluxing ammonia water produced by injecting water into a gas discharged from the top of the ammonia scrubber. The ammonia water flowing down in the scrubber and the hydrogen stream contained in the waste gas undergo a neutralization reaction to fix the hydrogen sulfide gas as ammonium salt in the water, whereby ammonia containing no hydrogen sulfide is removed from the scrubber tower. Can be collected from the top. Although this recovered ammonia contains some water, it can be used as the ammonia to be injected into the denitration apparatus. Further, the ammonia water in the reflux drum can be used as anticorrosion ammonia water in a petroleum refinery.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 shows an embodiment in which a wastewater treatment apparatus is a two-column system comprising a hydrogen sulfide stripper A and an ammonia stripper B. FIG. 2 shows an embodiment in which the wastewater treatment apparatus is a single-tower type with only a wastewater stripper C. In both drawings, the portion of the ammonia recovery apparatus according to the present invention is surrounded by a dotted line.

The embodiment shown in FIG. 1 is an embodiment in which the weight ratio of hydrogen sulfide to ammonia contained in the waste gas from the ammonia stripper B of the wastewater treatment apparatus is 0.5 or less. Hydrogen sulfide and waste gas containing a little more water are continuously pumped through a pipe 1 to an ammonia scrubber 2 filled with a commonly used packing. The pressure of the ammonia scrubber 2 is adjusted to normal pressure.

A BFW pipe 4 is connected in the middle of an air supply pipe 3 provided at the top of the scrubber 2, and the BFW at normal temperature is adjusted in the injection amount in accordance with the concentration of hydrogen sulfide in the waste gas.
(Boiler feed water) is injected at a rate of 50 to 200% based on the weight of ammonia, and the mixture is supplied from the air supply pipe 3 to a shell tube type or plate type indirect cooler 5 which is generally used at room temperature. After cooling, the mixture is sent to the reflux drum 6. The ammonia gas separated by the reflux drum 6 contains some water. While maintaining the pressure of the reflux drum 6 at normal pressure, excess ammonia gas is extracted from the pipe 7 and fed to a denitration device (omitted in the drawing). Further, a part of the ammonia water separated from the liquid feed pipe 8 provided below the reflux drum 6 is extracted as anticorrosive ammonia water as required, and the entire amount of the liquid remaining in the reflux drum 6 is returned to the ammonia scrubber 2. .

[0008] Ammonia water flowing down in the ammonia scrubber 2 reacts with hydrogen sulfide in the raw material gas to produce an ammonium salt and fixes the hydrogen sulfide in the liquid. And a liquid feed pipe 9 disposed at the bottom of the ammonia scrubber 2.
From the solution containing the ammonium sulfide salt of hydrogen sulfide,
It is returned to the hydrogen sulfide stripper A of the wastewater treatment equipment. By returning the same liquid, the ammonia contained in the liquid will be recycled inside the system, and as a result, the ammonia contained in the wastewater can be recovered as high-purity ammonia gas in high yield. become.

The embodiment shown in FIG. 2 is an embodiment in which the wastewater treatment apparatus comprises only the wastewater stripper C and the content of hydrogen sulfide contained in the waste gas discharged from the stripper C is high. Waste gas containing hydrogen sulfide in addition to ammonia and a little more water is continuously pumped through a pipe 1 to an ammonia scrubber 2 filled with a generally used filler. This ammonia scrubber 2
Is adjusted to normal pressure.

A BFW pipe 4 is connected to the middle of an air supply pipe 3 provided at the top of the ammonia scrubber 2, and the BFW at normal temperature, whose injection amount is adjusted according to the concentration of hydrogen sulfide in the waste gas, is converted into ammonia. The mixture is injected at a ratio of 50 to 200% by weight, and the mixture is cooled to room temperature by the indirect cooler 5 as described above and sent to the reflux drum 6. Reflux drum 6
The ammonia gas separated in the step contains some water. While maintaining the pressure of the reflux drum 6 at normal pressure, excess ammonia gas is extracted from the pipe 7 and fed to a denitration device (omitted in the drawing). Further, a part of the ammonia water separated from the liquid feed pipe 8 provided below the reflux drum 6 is extracted as anticorrosive ammonia water as required, and the entire amount of the liquid remaining in the reflux drum 6 is returned to the ammonia scrubber 2. .

Ammonia water flowing down in the ammonia scrubber 2 reacts with hydrogen sulfide in the raw material gas to form an ammonium salt, and fixes the hydrogen sulfide in the liquid. Then, a liquid containing an ammonium salt of hydrogen sulfide is withdrawn from a liquid feed pipe 9 provided at the bottom of the ammonia scrubber 2 and is diluted with wastewater that has been inserted into a wastewater stripper C, so that sulfuric acid contained in the liquid is removed. Reduce the concentration of hydrogen and ammonia to one-hundredth or less, and use the same solution for hydrogen sulfide separator 1
Attach to 0.

[0012] The hydrogen sulfide separator 10 is a facility that has been already practiced in the past to produce water of high purity by treating water containing hydrogen sulfide and ammonia. The separator 10 incorporates a commonly used packing or tray, the upper part of the tower is a concentration section for increasing the concentration of hydrogen sulfide by injecting BFW from the pipe 4a, and the lower part is a reboiler. 1
1 is a stripping section with 1; Hydrogen sulfide gas is extracted from a gas pipe 12 provided at the top of the separator 10 and sent to a Claus process reactor (not shown).

On the other hand, a liquid containing ammonia and a small amount of hydrogen sulfide is withdrawn from a liquid feed pipe 13 provided at the bottom of the separator 10 and is put into a wastewater stripper C. Ammonia contained in the liquid is recycled through the system by filling the liquid into the wastewater stripper C. As a result, the ratio of hydrogen sulfide to ammonia contained in the waste gas of the wastewater stripper C is as follows: It is much smaller than the ratio of hydrogen sulfide to ammonia in wastewater. By recycling the bottom liquid of the ammonia scrubber 2 to the wastewater stripper C via the hydrogen sulfide separator 10, the concentration of hydrogen sulfide in the gas supplied to the ammonia scrubber 2 is reduced, and the ammonia contained in the wastewater is ultimately reduced. Thus, it becomes possible to recover the ammonia gas with high purity in high yield.

[0014]

According to the present invention, as described above, in the conventional method, ammonia, which has been released to the atmosphere after oxidation by combustion, is recovered and recycled, so that its economic effect is very large. In addition, the emission of nitrogen oxides, which is one of the causes of environmental pollution, to the atmosphere can be prevented. In particular, in the method for recovering ammonia according to the present invention, since no alkaline chemicals containing ammonia are used from outside the system, the cost is low and there is no risk of by-producing waste. Further, since the neutralization reaction at normal temperature and normal pressure is employed without using distillation and stripping methods, the method is an economical method that consumes very little energy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment in a case where a wastewater treatment apparatus is a two-column system including a hydrogen sulfide stripper and an ammonia stripper.

FIG. 2 is an explanatory diagram showing an embodiment in a case where the wastewater treatment apparatus is a single-tower type with only a wastewater stripper.

[Explanation of symbols]

 Reference Signs List A hydrogen sulfide stripper B ammonia stripper C wastewater stripper 1 pipe 2 ammonia scrubber 3 air supply pipe 4 BFW pipe 5 indirect cooler 6 reflux drum 7 pipe 8 liquid feed pipe 9 liquid feed pipe 10 hydrogen sulfide separator 11 reboiler 12 gas pipe 13 liquid feed tube

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[Procedure amendment]

[Submission date] March 17, 2000 (2003.
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D002 AA03 AA13 AB02 AC10 BA02 BA13 BA15 CA07 CA13 DA35 EA02 FA06 GA02 GA03 GB02 GB04 GB06 GB11 HA04 HA08 4D037 AA11 AA15 AB04 AB12 AB13 BA23 BB02 BB06

Claims (2)

[Claims] 1. A waste gas discharged from a petroleum refinery is discharged from a stripper for processing, and a waste gas containing ammonia and hydrogen sulfide is continuously pumped to an ammonia scrubber.
Pure water is injected into the gas exiting the ammonia scrubber tower, the gas-liquid mixture is indirectly cooled with cooling water, etc., and the generated gas-liquid mixed fluid is sent to the reflux drum to separate it into gas and liquid. Recycling the separated liquid to the ammonia scrubber and extracting the separated ammonia gas as ammonia for a denitration device. A method for recovering ammonia from waste gas discharged from a wastewater treatment device. 2. An ammonia scrubber for continuously treating waste gas discharged from a stripper for treating wastewater containing ammonia, hydrogenated hydrogen, etc., is provided in an air supply pipe provided at the top of the ammonia scrubber tower. A pipe for injecting pure water is connected, and the end of the air supply pipe is connected to a reflux drum via an indirect cooler, and separated into gas and liquid by the reflux drum, and the separated liquid is supplied to an ammonia scrubber. A device for recovering ammonia from waste gas discharged from a wastewater treatment device, wherein the ammonia is refluxed and ammonia gas is extracted as ammonia for a denitration device.