Wastewater treatment system and wastewater treatment method

Abstract

To provide a wastewater treatment system and a wastewater treatment method capable of treating exhaust gas emitted from a combustion machine that uses fuel that reacts with oxygen during combustion to form carbon dioxide and water, simultaneously, suitably neutralizing alkaline wastewater derived from cement, for example, and capable of neutralizing alkaline wastewater at a low cost.SOLUTION: A wastewater treatment system includes: a concentrator 5 for concentrating CO2 contained in air A1 containing exhaust gas exhausted from a combustion machine 2 that uses fuel that reacts with oxygen during combustion to form carbon dioxide and water; and a feeder 6 for supplying air A2 containing CO2 concentrated by the concentrator 5 to an alkaline drainage D.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wastewater treatment system and a wastewater treatment method for treating, for example, alkaline wastewater derived from cement.

Background Art

[0002] When repair or placement is performed using cement at a construction site, alkaline wastewater derived from cement is generated. And in order to discharge this alkaline wastewater into a public water area such as a general river, this alkaline wastewater must be neutralized to meet the wastewater standard value (pH 5.8 to 8.6).

[0003] Conventionally, an alkaline wastewater neutralization treatment apparatus that neutralizes alkaline wastewater derived from cement using combustion exhaust gas from a gas engine of a cogeneration system is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the alkaline wastewater neutralization treatment apparatus described in Patent Document 1, since various fuels such as natural gas, petroleum, and LP gas are generally used as fuels for the gas engine of the cogeneration system, for example, NO X , SO X and there is a risk of generating a large amount of combustion exhaust gas containing harmful substances such as CO, so there is a problem that it is not easy to treat this combustion exhaust gas, and this is the problem to be solved by the present invention.

Means for Solving the Problems

[0006] The present invention has been invented for the purpose of solving these problems in view of the above circumstances. The invention according to claim 1 is a concentration device that concentrates carbon dioxide contained in air including exhaust gas exhausted from a combustion machine using a fuel that reacts with oxygen during combustion to become carbon dioxide and water, and a supply device that supplies air containing carbon dioxide concentrated by this concentration device to alkaline wastewater. A wastewater treatment system characterized by comprising. The invention according to claim 2 is a wastewater treatment system characterized in that, in claim 1, the fuel is kerosene. The invention according to claim 3 is a wastewater treatment system characterized in that, in claim 1 or 2, the supply device aerates the wastewater with air containing carbon dioxide concentrated by the concentration device to neutralize the wastewater. The invention according to claim 4 is a wastewater treatment method characterized by comprising a concentration step of concentrating carbon dioxide contained in air including exhaust gas exhausted from a combustion machine using a fuel that reacts with oxygen during combustion to become carbon dioxide and water, and a supply step of supplying air containing the concentrated carbon dioxide to alkaline wastewater. The invention according to claim 5 is a wastewater treatment method characterized in that, in claim 4, kerosene is used as the kerosene. The invention according to claim 6 is a wastewater treatment method characterized in that, in claim 4 or 5, the supply step aerates the wastewater with air containing carbon dioxide concentrated by the concentration step to neutralize the wastewater.

Effects of the Invention

[0007] According to the invention of claim 1 or 4, the exhaust gas discharged from a combustion machine using a fuel that reacts with oxygen during combustion to form carbon dioxide and water has a very low content of harmful substances. Therefore, by concentrating the carbon dioxide contained in the air including this exhaust gas and supplying it to alkaline wastewater, the apparatus and system for concentrating the carbon dioxide contained in the air including this exhaust gas can be simplified. Thus, while treating the exhaust gas discharged from a combustion machine using kerosene as fuel, for example, alkaline wastewater derived from cement can be appropriately neutralized, and the neutralization treatment of alkaline wastewater can be performed at low cost. According to the invention of claim 2 or 4, the exhaust gas discharged from a combustion machine using kerosene as fuel is composed almost entirely of carbon dioxide and water. For this reason, the apparatus and system for concentrating the carbon dioxide contained in the air including this exhaust gas can be made very simple, and the neutralization treatment of alkaline wastewater can be performed at very low cost. According to the invention of claim 3 or 6, by aerating the air containing concentrated carbon dioxide to alkaline wastewater to neutralize this alkaline wastewater, the neutralization treatment of this alkaline wastewater can be efficiently performed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a wastewater treatment system. Specifically, this wastewater treatment system 1 is a neutralization treatment system for neutralizing, for example, alkaline wastewater D derived from cement. As shown in FIG. 1, the wastewater treatment system 1 uses exhaust gas discharged from a combustion machine 2 such as a general heating machine that uses kerosene, preferably low-sulfur A heavy oil (LSA heavy oil: a mixture of 90% light oil and a small amount of residual oil with a sulfur content of "sulfur" of 0.5% or less) as fuel to neutralize the wastewater D. Here, this combustion machine 2 is for heating installed at a construction site, etc., and specifically, a boiler for heating the mixing water of a site plant is used.

[0010] Note that as the fuel used in the combustion machine 2, a liquid fuel such as C 11 H 24 ~C 14 H 30 grade kerosene is sufficient. When burned, it reacts with oxygen to form C 11 H 24 which becomes C 12 H 24 +12O 2 →12CO 2 +12H 2 O. In addition, as the fuel, a gaseous fuel such as city gas or natural gas may be used. When burned, methane (CH 4 ) reacts with oxygen to form CH 4 +2O 2 →CO 2 +2H 2 O. Also, as the fuel, a solid fuel such as coal or coke may be used. In short, any combustion machine 2 that uses a fuel that reacts with oxygen during combustion to form CO 2 (including CO) and water can be used.

[0011] And the combustion machine 2 is provided with an exhaust port 2a for discharging exhaust gas. This exhaust port 2a discharges the atmosphere together with the exhaust gas generated by the combustion treatment of kerosene in the combustion machine 2, and high-concentration carbon dioxide (CO 2Air A1 containing 2 is discharged. And a pipe is installed at the exhaust port 2a and an exhaust duct 2b is connected. The downstream side of this exhaust duct 2b is connected to a concentrator 5 that concentrates 2 CO contained in the air A1. As this concentrator 5, a 2 CO concentrator (product name: ZeoCollect, manufactured by Daifuku Kogyo Co., Ltd.) etc. are used. Specifically, this concentrator 5 utilizes the property of ferrierite (a type of zeolite) produced within Shimane Prefecture to adsorb 2 CO. Air A1 containing 2 CO is recovered and fed into two cylindrical cartridges 5a, 5b filled with crushed ferrierite, and pressurization and depressurization are repeated to concentrate 2 the CO contained in this air A2 by 10 to 20 times and store the air A2 containing highly pure

[0012] CO in a storage tank 5c. 2 Here, as this concentrator 5, in addition to the above-mentioned 2 CO concentrator (product name: ZeoCollect, manufactured by Daifuku Kogyo Co., Ltd.), for example, a X storage supply device (product name: Agreef (registered trademark), manufactured by Futaba Sangyo Co., Ltd.) etc. can also be used. In this case, the concentrator 5 removes harmful substances such as nitrogen compounds ( X NO), sulfur compounds ( 2 SO), and carbon monoxide (CO) contained in the recovered air A1 to almost zero by exhaust gas purification and heat exchange technology, and purifies 2 the CO contained in this air A1. Then, the concentrator 5 cools and concentrates the air containing the purified 2 CO until it reaches room temperature and then recovers it, and stores the air A2 containing highly pure

[0013] CO in a storage tank 5c. 2A supply device 6 for supplying outside air A2 containing [is attached]. This supply device 6 has a supply duct 6a with its upstream side connected to the storage tank 5c, and a blower 6b such as a compressor is attached to the middle part of this supply duct 6a. Then, the downstream side of the supply duct 6a is inserted and attached into the alkaline wastewater D stored in the storage tank 7, and air A2 with a high purity of CO 2 is aerated into the wastewater D to lower the pH of this wastewater D for neutralization treatment.

[0014] Here, the alkaline wastewater D mainly comes from spraying concrete, shotcrete, etc. carried out during tunnel excavation or for repair and construction work inside the tunnel after completion, that is, mainly when repair and placement are carried out using cement at the construction site, but it can also be generated from the elution of calcium contained in some natural ground. Also, the neutralization treatment of the wastewater D stored in the storage layer 7 aims to lower the pH of this wastewater D. If possible, for example, until it reaches the wastewater discharge standard value (pH 5.8 - pH 8.6) that can be discharged into public water areas P such as general rivers, a large amount of air A2 containing high-purity CO 2 is preferably supplied for treatment. And the wastewater D that has been neutralized to this discharge standard value can be discharged by being released from the pump 8 installed in the storage tank 7 to the public water area P such as a general river through the drain pipe 9.

[0015] Next, a wastewater treatment method by the wastewater treatment system 1 according to an embodiment of the present invention will be described with reference to FIG. 2.

[0016] <Preparation step> Air A1 containing high-concentration CO 2 exhausted from the exhaust port 2a along with the driving of the combustion machine 2 is supplied to the concentrator 5 through the exhaust duct 2b (step S1).

[0017] <Concentration step> And this high-concentration CO 2Supply the air A1 containing [it] to the concentrator 5, send it into the two cartridges 5a, 5b of the concentrator 5, and repeat pressurization and depressurization, and the CO 2 contained in this air A1 is concentrated 10 to 20 times to obtain highly pure CO 2 and store it in the storage tank 5c as the air A2 containing [it] (step S2).

[0018] <Supply process> Furthermore, drive the blower 6b of the supply device 6, and aerate the air A2 stored in the storage tank 5c of the concentrator 5 into the alkaline wastewater D stored in the storage tank 7 through the supply duct 6a, and lower the pH of this wastewater D for neutralization treatment (step S3).

[0019] <Discharge process> After that, when the recovery amount of the air A2 is large and the wastewater D can be neutralized to the drainage standard value that allows the discharge of the wastewater D into the public water area P with this air A2, pump the wastewater D from the storage tank 7 through the drain pipe 9 using the pump 8, etc., and discharge it into the public water area P such as a general river (step S4).

[0020] <Function and effect> Generally, the exhaust gas discharged from the heating machine 2 such as a heater used at a construction site, using kerosene as fuel, specifically low-sulfur A heavy oil, is almost CO 2 and water (H 2 2O), and is the air A1 containing high-concentration CO 2 , so it has the feature of containing almost no harmful substances such as NO X , SO X and CO.

[0021] On the other hand, when a tunnel is being excavated or when repairs and construction work are carried out inside the tunnel after completion, the main sources of generation are cases such as when shotcrete, covering concrete, and in short, when repairs and placement are carried out using cement at the construction site. However, due to the elution of calcium contained in some natural ground, a large amount of alkaline drainage D is generated. In order to discharge this drainage D into the public water area P, it is necessary to perform neutralization treatment to the drainage standard values such as pH 5.8 to pH 8.6, for example.

[0022] Therefore, in one embodiment according to the present invention configured as described above, high-concentration CO 2 contained in the air A1 exhausted from the heating machine 2 is supplied to the concentrator 5 and concentrated to obtain high-purity CO 2 contained in the air A2. After that, this air A2 is supplied to the alkaline drainage D to lower the pH. As a result, even when construction work is being carried out using a heating machine 2 such as a boiler for kneading water heating, the CO 2 exhausted from this heating machine 2 can be reduced, and the alkaline drainage D can be efficiently neutralized using the high-concentration CO 2 contained in the air A1 exhausted from this heating machine 2. Therefore, the CO 2 exhausted from the heating machine 2 can be effectively utilized without being released to the outside air.

[0023] And, since the CO 2 exhausted from the heating machine 2 is used to neutralize, for example, the alkaline drainage D derived from cement, the neutralization treatment of the alkaline drainage D can be carried out at a lower cost compared to the conventional method of neutralizing alkaline drainage using liquefied carbon dioxide gas or dilute sulfuric acid.

[0024] In addition, the air A1 exhausted from the heating machine 2 may contain trace amounts of harmful substances such as NO X , SO X and CO depending on the operating conditions and operating environment of this heating machine 2. Therefore, before concentrating the CO 2 in the air A1 containing the exhaust gas exhausted from the heating machine 2, the NO contained in this air A1X , SO X and harmful substances such as CO can be removed by the concentrator 5 while purifying the carbon dioxide contained in this air A1. As a result, the purified CO 2 in the air A2 containing it is used to neutralize the alkaline wastewater D, so that contamination by harmful substances and the like that may occur when neutralizing the alkaline wastewater D can be appropriately prevented.

[0025] Furthermore, since the air A2 concentrated with CO 2 by the concentrator 5 is aerated into the alkaline wastewater D stored in the storage tank 7 through the supply tact 6a of the supply device 6 for neutralization treatment, the neutralization treatment of this alkaline wastewater D can be efficiently performed with a smaller supply amount of air A2. And the pH of the alkaline wastewater D can be lowered with the highly pure air A2 concentrated with this CO 2 . Therefore, depending on the supply amount (recovery amount) of this air A2, the wastewater D can be neutralized to the drainage standard value that can be discharged into the public water area P, and this neutralized wastewater D can be safely discharged into the public water area P.

[0026] As described above, one embodiment of the present invention has been described, but it goes without saying that the present invention is not limited to the above-described one embodiment. For example, the concentrator 5, the supply device 6, etc. constituting the wastewater treatment system 1 according to the present invention may have any configuration as long as the processing performed by those devices can be appropriately performed.

Explanation of symbols

[0027] 1 Wastewater treatment system 2 Combustion machine 2a Exhaust port 2b Exhaust duct 5 Concentrator 5a, 5b Cartridge 5c Storage tank 6 Supply device 6a Supply duct 6b Blower 7 Storage tank 8 Pump 9 Drain pipe D Drainage P Public water area A1 Air containing high-concentration CO 2 Air containing A2 Air containing highly pure CO 2 Air containing

Claims

1. A concentrating device that concentrates carbon dioxide contained in air including exhaust gas exhausted from a combustion machine using a fuel that reacts with oxygen during combustion to become carbon dioxide and water, and A supply device that supplies air containing carbon dioxide concentrated by this concentrating device to alkaline wastewater, A wastewater treatment system characterized by comprising the above.

2. The fuel is kerosene, The wastewater treatment system according to Claim 1, characterized by the above.

3. The supply device aerates the wastewater with air containing carbon dioxide concentrated by the concentrating device to neutralize the wastewater, The wastewater treatment system according to Claim 1 or 2, characterized by the above.

4. A concentrating step of concentrating carbon dioxide contained in air including exhaust gas exhausted from a combustion machine using a fuel that reacts with oxygen during combustion to become carbon dioxide and water, and A supply step of supplying air containing the concentrated carbon dioxide to alkaline wastewater, A wastewater treatment method characterized by comprising the above.

5. As the kerosene, kerosene is used, The wastewater treatment method according to Claim 4, characterized by the above.

6. The supply step aerates the wastewater with air containing carbon dioxide concentrated by the concentrating step to neutralize the wastewater, The wastewater treatment method according to Claim 4 or 5, characterized by the above.

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