Energy-saving sewage purification system combining heat supply network and raw water treatment system

Abstract

The utility model relates to the field of sewage purification, and provides an energy-saving sewage purification system combining a heat supply network and a raw water treatment system, which comprises a heat mass generation tower, a heat mass absorption tower, a heat exchange unit, a first cooling unit, a second cooling unit, the raw water treatment system and a heating water heating system, a gas outlet in the top of the heat mass generation tower is communicated with a gas inlet in the bottom of the heat mass absorption tower; a gas outlet in the top of the heat mass absorption tower is communicated with a gas inlet in the bottom of the heat mass generation tower; a liquid outlet in the bottom of the heat and mass generation tower is sequentially communicated with a heat exchange unit, a first circulating liquid pipe and a liquid inlet in the top of the heat and mass generation tower; a liquid outlet in the bottom of the heat mass absorption tower is sequentially communicated with a liquid inlet in the top of the heat mass absorption tower and second circulating liquid pipes of the heat exchange unit, the first cooling unit and the second cooling unit; the first cooling unit is communicated with the heating water heating system; and the second cooling unit is communicated with the raw water treatment system. According to the system, waste heat can be fully utilized, and the purpose of saving energy consumption is achieved.

Description

Technical Field

[0001] The utility model relates to the field of sewage purification, and more specifically, to an energy-saving sewage purification system integrating a combined heat network and a raw water treatment system. Background Technique

[0002] In the field of high-salt sewage purification, at present, multi-effect evaporation or MVR or an integrated sewage purification system of open evaporation and absorption is mostly used for concentration reduction, and then evaporation crystallization or drying and solidification methods are used to achieve zero discharge; at present, there is a problem that low-grade heat sources cannot be effectively utilized in this process.

[0003] In view of this, the present utility model is specifically proposed. Content of the Utility Model

[0004] The purpose of the present utility model is to provide an energy-saving sewage purification system integrating a combined heat network and a raw water treatment system, which can effectively utilize low-grade heat sources.

[0005] The embodiments of the present utility model are implemented as follows:

[0006] In a first aspect, the present utility model provides an energy-saving sewage purification system integrating a combined heat network and a raw water treatment system, including:

[0007] A heat and mass generation tower, a heat and mass absorption tower, a heat exchange unit, a first cooling unit, a second cooling unit, a raw water treatment system, and a heating water heating system;

[0008] The air outlet at the top of the heat and mass generation tower is communicated with the air inlet at the bottom of the heat and mass absorption tower through a first circulation air pipe, and the air outlet at the top of the heat and mass absorption tower is communicated with the air inlet at the bottom of the heat and mass generation tower through a second circulation air pipe. At least one of the first circulation air pipe and the second circulation air pipe is provided with a fan;

[0009] The liquid outlet at the bottom of the heat and mass generation tower is communicated with the liquid inlet at the top of the heat and mass generation tower through a first circulation liquid pipe of the cold source channel of the path heat exchange unit. The bottom of the heat and mass generation tower is also connected with a concentrated sewage discharge pipe, and a fresh sewage inlet pipe is connected to the first circulation liquid pipe;

[0010] The liquid outlet at the bottom of the heat and mass absorption tower is communicated with the liquid inlet at the top of the heat and mass absorption tower through a second circulation liquid pipe of the heat source channel of the path heat exchange unit, the first cooling unit, and the second cooling unit. A purified water discharge pipe is connected to the second circulation liquid pipe;

[0011] One end of the cold source channel of the first cooling unit is communicated with the heat network circulating water pipe, and the other end of the cold source channel of the first cooling unit is communicated with the heating water heating system;

[0012] One end of the cold source channel of the second cooling unit is communicated with the raw water inlet pipe, and the other end of the cold source channel of the second cooling unit is communicated with the raw water treatment system.

[0013] In an alternative embodiment, the sewage purification system further includes a heating unit, which is arranged on the pipeline of the first circulating liquid pipe, between the heat exchange unit and the liquid inlet of the heat and mass generation tower;

[0014] The heat source channel of the heating unit is communicated with the high-temperature heat source pipe, and the heat source channel of the heating unit is communicated with the first circulating liquid pipe. The high-temperature heat source pipe is a high-temperature steam pipe, a high-temperature flue gas pipe or a high-temperature hot water pipe.

[0015] In an alternative embodiment, the connection point between the fresh sewage inlet pipe and the first circulating liquid pipe is located between the heat exchange unit and the heating unit.

[0016] In an alternative embodiment, the connection point between the purified water discharge pipe and the second circulating liquid pipe is located between the heat exchange unit and the first cooling unit.

[0017] In an alternative embodiment, the raw water treatment system includes a ultrafiltration device, a reverse osmosis device and a mixed bed demineralization device arranged in sequence; the cold source channel of the second cooling unit is communicated with the ultrafiltration device.

[0018] In an alternative embodiment, the heating water heating system includes an electrode boiler and a heating water heating unit;

[0019] The heat source output by the electrode boiler is communicated with the heat source channel of the heating water heating unit. One end of the cold source channel of the heating water heating unit is communicated with the cold source channel of the first cooling unit, and the other end of the cold source channel of the heating water heating unit is communicated with the heat user pipeline.

[0020] In an alternative embodiment, the heating water heating system further includes a generator, and the generator is electrically connected to the electrode boiler through a surplus power output circuit during peak shaving.

[0021] In an alternative embodiment, a fan is arranged on the first circulating gas pipe.

[0022] The beneficial effects of the embodiments of the present utility model are:

[0023] The energy-saving sewage purification system of the combined heat network and the raw water treatment system provided by the present utility model can realize the coordinated coupling of the heating water system, the raw water treatment system and the sewage purification system; it can realize the cascade utilization of energy and fully realize the recovery and utilization of waste heat. Description of the Drawings

[0024] To more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present utility model, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of the sewage purification system provided by the embodiment of the present utility model.

[0026] Icon: 100 - sewage purification system; 101 - heat and mass generation tower; 102 - heat and mass absorption tower; 103 - heat exchange unit; 104 - first cooling unit; 105 - second cooling unit; 106 - fan; 107 - heating unit; 111 - first circulating gas pipe; 112 - second circulating gas pipe; 113 - first circulating liquid pipe; 114 - second circulating liquid pipe; 115 - fresh sewage inlet pipe; 116 - concentrated sewage discharge pipe; 117 - purified water discharge pipe; 118 - heat network circulating water pipe; 119 - raw water inlet pipe; 120 - high-temperature heat source pipe; 131 - ultrafiltration device; 132 - reverse osmosis device; 133 - mixed bed desalination device; 141 - electrode boiler; 142 - heating water heating unit; 143 - generator; 144 - heat user end; 151 - water pump. Specific embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the present utility model claimed, but merely represents the selected embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present utility model.

[0029] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0030] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present utility model is usually placed during use. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present utility model. In addition, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0031] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0032] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0033] As Figure 1 shown, an energy-saving sewage purification system 100 integrating a combined heat network and a raw water treatment system is provided in an embodiment of the present utility model.

[0034] A heat mass generation tower 101, a heat mass absorption tower, a heat exchange unit 103, a first cooling unit 104, a second cooling unit 105, a raw water treatment system, and a heating water heating system.

[0035] The air outlet at the top of the heat mass generation tower 101 is communicated with the air inlet at the bottom of the heat mass absorption tower through a first circulation air pipe 111, and the air outlet at the top of the heat mass absorption tower is communicated with the air inlet at the bottom of the heat mass generation tower 101 through a second circulation air pipe 112. At least one of the first circulation air pipe 111 and the second circulation air pipe 112 is provided with a fan 106.

[0036] Spraying mechanisms are provided at the tops of both the heat and mass generation tower 101 and the heat and mass absorption tower. Low-temperature and low-humidity air enters the heat and mass generation tower 101, contacts the high-temperature sewage sprayed from the top, and transfers mass and heat. The low-temperature and low-humidity air is transformed into high-temperature and high-humidity air and enters the bottom of the heat and mass absorption tower through the first circulation air pipe 111. The high-temperature and high-humidity air contacts the low-temperature water sprayed from the top in the heat and mass absorption tower, and the heat and moisture of the high-temperature and high-humidity air enter the sprayed water. After the temperature and humidity are reduced, it enters the bottom of the heat and mass generation tower 101 through the second circulation air pipe 112 for circulation.

[0037] The fan 106 provides power for the air to circulate between the heat and mass generation tower 101 and the heat and mass absorption tower. Specifically, the number of fans 106 is set to 1, and it is arranged on the first circulation air pipe 111. It should be noted that in other embodiments of the present invention, the installation position of the fan 106 can also be arranged on the second circulation air pipe 112; or the number of fans is set to 2, and one is arranged on each of the first circulation air pipe 111 and the second circulation air pipe 112.

[0038] Before starting up, first fill the gas circulation system composed of the heat and mass generation tower 101, the heat and mass absorption tower, the first circulation air pipe 111, and the second circulation air pipe 112 with air. After being filled, there is no need to inflate again subsequently.

[0039] The liquid outlet at the bottom of the heat and mass generation tower 101 is connected to the first circulation liquid pipe 113 of the cold source channel of the path heat exchange unit 103 and is communicated with the liquid inlet at the top of the heat and mass generation tower 101. A concentrated sewage discharge pipe 116 is also connected to the bottom of the heat and mass generation tower 101, and a fresh sewage inlet pipe 115 is connected to the first circulation liquid pipe 113.

[0040] After the high-temperature sewage transfers mass and heat with the low-temperature and low-humidity air, the moisture in it is taken away, and the high-temperature sewage is concentrated. The concentrated high-temperature sewage accumulates at the bottom of the heat and mass generation tower 101, enters the top of the heat and mass generation tower 101 through the first circulation liquid pipe 113 and is reheated by the heat exchange unit 103 for spraying again. Since the heat and mass sewage circulates continuously, in order to maintain the stability of the position system and ensure the continuity of sewage purification, it is necessary to continuously introduce fresh sewage into the system through the fresh sewage inlet pipe and discharge the concentrated sewage through the concentrated sewage discharge pipe 116.

[0041] Optionally, the sewage purification system 100 further includes a heating unit 107, which is arranged on the pipeline of the first circulation liquid pipe 113, between the heat exchange unit 103 and the liquid inlet of the heat and mass generation tower 101.

[0042] The temperature of the sewage after heat exchange by the heat exchange unit 103 is relatively low, and directly entering the heat and mass generation tower 101 for heat and mass transfer with air has relatively poor effects. Therefore, a heating unit 107 is provided to further heat the sewage heated by the heat exchange unit 103 to ensure better sewage concentration effects.

[0043] The heat source channel of the heating unit 107 is connected to the high-temperature heat source pipe 120, and the heat source channel of the heating unit 107 is connected to the first circulating liquid pipe 113. The high-temperature heat source pipe 120 is a high-temperature steam pipe, a high-temperature flue gas pipe, or a high-temperature hot water pipe. The high-temperature heat source of the heating unit 107 comes from externally connected high-temperature steam, high-temperature flue gas, or high-temperature water. It should be noted that in addition to using the above heat sources as heating energy, the heating unit 107 can also use electric energy or gas to heat the passing sewage.

[0044] Optionally, the connection point of the fresh sewage inlet pipe 115 and the first circulating liquid pipe 113 is located between the heat exchange unit 103 and the heating unit 107. After the fresh sewage enters the system, it is first heated by the heating unit 107 and then enters the heat and mass generation tower 101.

[0045] The liquid outlet at the bottom of the heat and mass absorption tower is connected to the liquid inlet at the top of the heat and mass absorption tower through the heat source channel of the heat exchange unit 103, the first cooling unit 104, and the second circulating liquid pipe 114 of the second cooling unit 105. A purified water discharge pipe 117 is connected to the second circulating liquid pipe 114.

[0046] After the low-temperature spray water contacts the high-temperature and high-humidity air, it absorbs the moisture and heat in the air and accumulates at the bottom of the heat and mass absorption tower. Through the second circulating liquid pipe 114, it is heated successively by the heat exchange unit 103, the first cooling unit 104, and the second cooling unit 105 and then returns to the top of the heat and mass absorption tower for circulation as spray water. Since the spray water absorbs the moisture in the air, its quantity is continuously increasing. Therefore, in order to maintain the system stability, it is necessary to continuously discharge the spray water through the purified water discharge pipe 117.

[0047] One end of the cold source channel of the first cooling unit 104 is connected to the heat network circulating water pipe 118, and the other end of the cold source channel of the first cooling unit 104 is connected to the heating water heating system.

[0048] The spray water at the bottom of the heat and mass absorption tower has a relatively high temperature, and after heating the circulating sewage by the heat exchange unit 103, the heat it carries is still relatively high. Therefore, it can heat the heat network circulating water through the first cooling unit 104. After the heated heat network circulating water is heated again by the heating water heating system, it reaches the heat user end 144 for use. By connecting the heat network circulating water pipe 118 to this system, the full utilization of waste heat can be realized, and the purpose of better energy conservation can be achieved.

[0049] Optionally, the heating water heating system includes an electrode boiler 141 and a heating water heating unit 142; the heat source output by the electrode boiler 141 is communicated with the heat source channel of the heating water heating unit 142, and one end of the cold source channel of the heating water heating unit 142 is communicated with the cold source channel of the first cooling unit 104, and the other end of the cold source channel of the heating water heating unit 142 is communicated with the heat user pipeline.

[0050] The electrode boiler 141 uses electric energy to heat the water therein and outputs hot water to the heating water heating unit 142 to reheat the heat network circulating water.

[0051] Optionally, the heating water heating system further includes a generator 143, and the generator 143 is electrically connected to the electrode boiler 141 through a surplus power output circuit during peak shaving.

[0052] The surplus power output by the generator 143 during peak shaving can be input into the electrode boiler 141 through the surplus power output circuit during peak shaving to provide electric energy for heating water. In this way, the full utilization of energy can be realized.

[0053] One end of the cold source channel of the second cooling unit 105 is communicated with the raw water inlet pipe 119, and the other end of the cold source channel of the second cooling unit 105 is communicated with the raw water treatment system.

[0054] The spray water at the bottom of the heat mass absorption tower has a relatively high temperature, and after being cooled by the heat exchange unit 103 and the first cooling unit 104, the heat is still relatively high. Therefore, the second cooling unit 105 can be used to heat the raw water, and the heated raw water is then input into the raw water treatment system for treatment. In this way, the full utilization of energy can be further realized.

[0055] Optionally, the raw water treatment system includes a ultrafiltration device 131, a reverse osmosis device 132 and a mixed bed demineralization device 133 arranged in sequence; the cold source channel of the second cooling unit 105 is communicated with the ultrafiltration device 131.

[0056] The raw water can be tap water, river water or reclaimed water. The ultrafiltration device 131, the reverse osmosis device 132 and the mixed bed demineralization device 133 are currently conventional raw water deep treatment devices, and will not be elaborated here. By introducing the raw water into this system to utilize the waste heat for heating and then inputting it into the backend treatment, the present invention can make full use of energy and reduce production costs.

[0057] Optionally, water pumps 151 are arranged on the first circulating liquid pipe 113, the second circulating liquid pipe 114, the heat network circulating water pipe 118, the raw water inlet pipe 119 and the pipeline connecting the electrode boiler 141 and the heating water heating unit 142.

[0058] Optionally, the heat exchange unit 103, the first cooling unit 104, the second cooling unit 105, the heating unit 107, and the heating water heating unit 142 can all be heat exchangers, and the heat exchanger can be a highly efficient anti-corrosion plate heat exchanger.

[0059] The specific process of the present invention will be further introduced below:

[0060] Sewage process:

[0061] Sewage is replenished into the first circulating liquid pipe 113, and after being heated by the heat recovery unit and the heating unit 107, it undergoes heat and mass transfer with the air spray in the heat and mass generation tower 101. The sewage is concentrated, and the purified water is carried out by the air and enters the heat and mass absorption tower. The concentrated sewage can be discharged from the bottom of the tower.

[0062] Purified water process:

[0063] The purified water is cooled by the heat exchange unit 103, the first cooling unit 104, and the second cooling unit 105, and then enters the heat and mass absorption tower, where it undergoes heat and mass transfer with the high-temperature and high-humidity air spray. The moisture in the air is condensed and precipitated; the purified water is discharged after the heat exchange unit 103.

[0064] Heat source process:

[0065] The heat source of the heating unit 107 is steam, high-temperature flue gas, gas, electric energy, high-temperature hot water, etc.

[0066] Hot network water process:

[0067] The return water of the hot network is pressurized by the water pump 151, enters the first cooling unit 104 for preheating, and then enters the heating water heating unit 142 to be heated to the target temperature and supplied to the hot user end 144.

[0068] Raw water process:

[0069] The raw water is pressurized by the water pump 151, enters the second cooling unit 105 for preheating, and then successively enters the ultrafiltration device 131, the reverse osmosis device 132, and the mixed bed demineralization device 133, and finally produces demineralized water.

[0070] Electrode boiler 141 process:

[0071] During the peak shaving period, the excess electricity is output from the generator 143 through the surplus electricity output circuit during peak shaving, and after passing through the transformer, it enters the electrode boiler 141. The heat of the electrode boiler 141 is carried to the heating water heating unit 142 by the intermediate water system.

[0072] The following will be described in combination with actual application examples:

[0073] The concentrated brine or desulfurized wastewater in the water treatment workshop, the sewage temperature at the bottom of the heat and mass generation tower 101 is 45 - 55 °C, the sewage temperature sprayed at the top of the heat and mass generation tower 101 is 80 - 95 °C, and the air temperature entering the bottom of the heat and mass generation tower 101 is 40 - 55 °C; the air temperature entering the bottom of the heat and mass absorption tower is 75 - 93 °C, and the purified water temperature at the bottom of the heat and mass absorption tower is 72 - 90 °C; the temperature of the raw water before entering the second cooling unit 105 is 5 - 10 °C, and the temperature after heating is 25 - 30 °C; the temperature of the heat network circulating water before entering the second cooling unit 105 is 35 - 45 °C, and the temperature after heating is 48 - 58 °C.

[0074] In summary, the energy-saving sewage purification system 100 for the combined heat network and raw water treatment system provided by the present utility model has the following characteristics:

[0075] ① It realizes the organic combination of the heating water system, the raw water treatment system, and the sewage purification system 100, realizes the use of high-quality energy for sewage purification, low-quality energy for preheating raw water and heating water, and realizes zero energy consumption of the sewage purification system 100.

[0076] ② It realizes the preheating of raw water and effectively improves the production efficiency of demineralized water;

[0077] ③ It realizes the preheating of heating water and reduces the cost of heating water.

[0078] Therefore, the energy-saving sewage purification system 100 for the combined heat network and raw water treatment system provided by the present utility model can realize the coordinated coupling of the heating water system, the raw water treatment system, and the sewage purification system 100; it can realize the cascade utilization of energy, fully realize the recovery and utilization of waste heat, and effectively reduce the production cost.

[0079] The above is only the preferred embodiment of the present utility model and is not used to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. An energy-saving sewage purification system combining a heat network and a raw water treatment system, characterized in that: include: Heat and mass generating tower, heat and mass absorbing tower, heat exchange unit, first cooling unit, second cooling unit, raw water treatment system and heating water heating system; The air outlet at the top of the heat and mass generating tower is connected to the air inlet at the bottom of the heat and mass absorbing tower through a first circulating air pipe, and the air outlet at the top of the heat and mass absorbing tower is connected to the air inlet at the bottom of the heat and mass generating tower through a second circulating air pipe, and at least one of the first circulating air pipe and the second circulating air pipe is provided with a fan; The liquid outlet at the bottom of the heat and mass generating tower is connected to the liquid inlet at the top of the heat and mass generating tower through the first circulating liquid pipe of the cold source channel of the heat exchange unit. The bottom of the heat and mass generating tower is also connected to a concentrated sewage discharge pipe, and the first circulating liquid pipe is connected to a fresh sewage inlet pipe. The liquid outlet at the bottom of the heat and mass absorption tower is connected to the liquid inlet at the top of the heat and mass absorption tower through the heat source channel of the heat exchange unit, the first cooling unit, and the second circulating liquid pipe of the second cooling unit in sequence, and the second circulating liquid pipe is connected to a clean water discharge pipe; One end of the cold source channel of the first cooling unit is connected to the heat network circulating water pipe, and the other end of the cold source channel of the first cooling unit is connected to the heating water heating system; One end of the cold source channel of the second cooling unit is communicated with the raw water inlet pipe, and the other end of the cold source channel of the second cooling unit is communicated with the raw water treatment system.

2. The sewage purification system according to claim 1, characterized in that: The sewage purification system further comprises a heating unit, which is arranged on the pipeline of the first circulating liquid pipe and located between the heat exchange unit and the liquid inlet of the heat and mass generating tower; The heat source channel of the heating unit is connected to the high-temperature heat source pipe, and the heat source channel of the heating unit is connected to the first circulating liquid pipe. The high-temperature heat source pipe is a high-temperature steam pipe, a high-temperature flue gas pipe or a high-temperature hot water pipe.

3. The sewage purification system according to claim 2, characterized in that: The connection point between the fresh sewage inlet pipe and the first circulating liquid pipe is located between the heat exchange unit and the heating unit.

4. The sewage purification system according to claim 1, characterized in that: The connection point between the purified water discharge pipe and the second circulating liquid pipe is located between the heat exchange unit and the first cooling unit.

5. The sewage purification system according to claim 1, characterized in that: The raw water treatment system comprises an ultrafiltration device, a reverse osmosis device and a mixed bed desalination device which are arranged in sequence; the cold source channel of the second cooling unit is connected to the ultrafiltration device.

6. The sewage purification system according to claim 1, characterized in that: The heating water heating system comprises an electrode boiler and a heating water heating unit; The heat source output by the electrode boiler is connected to the heat source channel of the heating water heating unit, one end of the cold source channel of the heating water heating unit is connected to the cold source channel of the first cooling unit, and the other end of the cold source channel of the heating water heating unit is connected to the heat user pipeline.

7. The sewage purification system according to claim 6, characterized in that: The heating water heating system also includes a generator, which is electrically connected to the electrode boiler via a surplus power output circuit during peak load regulation.

8. The sewage purification system according to claim 1, characterized in that: The fan is arranged on the first circulation air pipe.

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