Equipment for directly preparing phosphoric acid from high-purity phosphorus steam

Abstract

The invention discloses equipment for directly preparing phosphoric acid from high-purity phosphorus steam, which comprises a combustion tower, a hydration tower and a dilute acid tower, the combustion tower is connected with a high-purity phosphorus steam pipeline and a compressed air pipeline, and the top of the combustion tower is connected with the top of the hydration tower through a phosphorus pentoxide gas conduit. The bottom of the hydration tower is connected with the top of the dilute acid tower through a pipeline; high-purity phosphorus steam and compressed air enter the combustion tower to be fully combusted, phosphorus pentoxide gas is obtained and enters the hydration tower, the advantages of good atomization performance and good spraying effect of a spiral spraying head are fully fused, the phosphorus pentoxide gas is dissolved in pure water to form phosphoric acid to the maximum extent, the recycling effect is good, and the recycling effect is good. And the equipment is simple in structure and small in occupied area.

Description

Technical Field

[0001] The invention relates to the field of acid production from phosphorus vapor, in particular to a device for directly preparing phosphoric acid from high-purity phosphorus vapor. Background Art

[0002] Phosphoric acid is an important chemical intermediate and a common raw material for synthesizing most phosphorus-containing compounds such as phosphates and some phosphate esters. It is widely used in food, medicine, electronics, petroleum, metallurgy, chemical and other industries.

[0003] Phosphoric acid can be produced from two sources, wet-process phosphoric acid and thermal-process phosphoric acid, depending on the production process. Wet-process nitric acid involves a double decomposition reaction between a strong acid—usually sulfuric acid, but also nitric acid, hydrochloric acid, and fluorosilicic acid—and phosphate rock to produce crude phosphoric acid with a high concentration of impurities. This is typically used in fertilizers. Purification yields food-grade phosphoric acid. Thermal-process phosphoric acid involves the reduction of phosphate rock with carbon at high temperatures to produce yellow phosphorus. In actual production, yellow phosphorus is burned in a furnace to produce phosphorus pentoxide gas, which is then piped to an absorption tower and sprayed with water mist. Upon contact with water, the phosphorus pentoxide converts to phosphoric acid. However, due to the lack of filtration in the pipelines, unburned yellow phosphorus or impurities in the yellow phosphorus can enter the absorption tower along with the gas. This results in low-purity phosphoric acid containing impurities that are difficult to remove, reducing product quality. Before the widespread adoption of wet-process phosphoric acid purification technology, it was virtually the only raw material for fine phosphate production. From the perspective of process flow, compared with thermal phosphoric acid, the process flow of wet phosphoric acid is long and complicated, with more unit operations and supporting facilities. However, economically, wet phosphoric acid has obvious advantages over thermal phosphoric acid. An important reason for the high cost of thermal phosphoric acid is the high energy consumption in production and the extensive salt content of the traditional thermal phosphoric acid production process. Summary of the Invention

[0004] The object of the present invention is to provide an apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: Disclosed is an apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor, comprising a combustion tower, a hydration tower, and a dilute acid tower. The combustion tower is connected to a high-purity phosphorus vapor pipeline and a compressed air pipeline. The combustion tower and the top of the hydration tower are connected via a phosphorus pentoxide gas conduit. The bottom of the hydration tower is connected to the top of the dilute acid tower via a pipeline.

[0006] A high-purity phosphorus vapor inlet pipe and a compressed air inlet pipe are fixedly provided at the outer end of the combustion tower, and the two are connected to the lower part of the combustion tower, and a fixed thermometer b is provided at the connection; a cooling water tank is provided at the top of the combustion tower, and a cooling water interlayer is provided around it, and the cooling water tank supplies water to the cooling water interlayer; a fixed thermometer a is provided on the connecting pipe between the combustion tower and the hydration tower, and a circulating water outlet and a sewage outlet are provided at the bottom of the combustion tower.

[0007] As a further solution of the present invention: a demister is fixedly provided on the top of the hydration tower, and three layers of mesh are inside the demister; an acid inlet, an overflow weir acid inlet and an acid spray port are fixedly provided on the top of the hydration tower, and a spiral spray head is fixedly provided on the acid spray port; an upper cooling water outlet is provided on the top of the hydration tower, an upper cooling water inlet and a lower cooling water outlet are provided in the middle part, and a circulating acid outlet, a lower cooling water inlet and a sewage outlet are provided at the bottom.

[0008] As a further solution of the present invention: the top of the dilute acid tower is fixedly provided with a gas outlet, and the top is fixedly provided with a pure water inlet, a dilute acid inlet and a pressure measuring point b, and a pressure measuring point b; a connecting pipe is provided in the dilute acid tower, which extends from the top of the dilute acid tower to the bottom, a Venturi scrubber is fixedly provided in the middle, connected to the DN dilute acid pipe, and a gas inlet is fixedly provided at the tail; the bottom of the dilute acid tower is fixedly provided with a dilute acid outlet and a liquid level gauge port.

[0009] As a further solution of the present invention: the range of the thermometer b is 0-2000℃, and the range of the thermometer a is 0-1000℃ As a further solution of the present invention: the pressure measuring point b is detected by a U-shaped pressure gauge with a measuring range of ±3kPa and a length of 2 meters.

[0010] As a further solution of the present invention: the spray angle of the acid spray port is ≥60° As a further solution of the present invention: a phosphorus burning nozzle is fixedly provided at the bottom of the combustion tower, and a swirl guide leaf is provided inside the phosphorus burning nozzle. The swirl guide leaf is composed of four, all distributed on the gas nozzle, and the swirl guide leaf is spiral; the radial spiral angle of each swirl guide leaf is degrees; the length of the swirl guide leaf along the axial direction of the gas nozzle is 200 mm, and the air entering the burner is in a tangential swirl shape, and the spiral direction of the swirl guide leaf is consistent with the rotation direction of the air.

[0011] As a further embodiment of the present invention, the Venturi scrubber includes a contracting section, the inlet of the contracting section of the Venturi scrubber being sealably welded to the connecting pipe at the bottom of the hydration tower, and the outlet of the Venturi scrubber being sealably welded to the gas inlet at the top of the dilute acid tower. One end of the dilute acid pipe is connected to the dilute acid injection port at the throat of the Venturi scrubber, and the other end is connected to the dilute acid inlet of the dilute acid tower. A method for directly preparing phosphoric acid from high-purity phosphorus vapor using the above-mentioned device comprises the following steps: introducing high-purity phosphorus vapor and compressed air into a combustion tower through an air inlet pipe at the bottom of the combustion tower, fully burning them in the combustion tower to generate phosphorus pentoxide gas, and monitoring the temperature in the combustion tower with a thermometer during the combustion process; The generated phosphorus pentoxide gas enters the hydration tower through the connecting pipe at the top of the combustion tower and the hydration tower. The spiral spray head at the top of the hydration tower sprays the acid liquid into atomized form, which fully contacts the phosphorus pentoxide gas, causing the phosphorus pentoxide gas to dissolve in water to form phosphoric acid. At the same time, the temperature in the hydration tower is controlled by the cooling water inlet and outlet. The phosphoric acid solution at the bottom of the hydration tower enters the dilute acid tower through a pipeline. In the dilute acid tower, it is further treated by a venturi scrubber connected to the middle of the pipeline. At the same time, pure water and dilute acid are introduced into the top of the dilute acid tower to wash and absorb the gas. Finally, the phosphoric acid product is obtained from the dilute acid outlet at the bottom of the dilute acid tower, and the gas is discharged from the gas outlet.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention allows high-purity phosphorus vapor and compressed air to enter the combustion tower for full combustion to obtain phosphorus pentoxide gas, which then enters the hydration tower and fully integrates the advantages of the spiral spray head with good atomization and good spraying effect, so that the phosphorus pentoxide gas is dissolved in pure water to the greatest extent to form phosphoric acid, with good recovery effect. In addition, the equipment has a simple structure and occupies a small area.

[0013] 2. The phosphorus vapor of the present invention has high purity during the recovery process, is almost free of CO, dust, sulfur gas and mud phosphorus, and does not require dust removal and desulfurization equipment, which is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 The figure is a schematic diagram of the structure of an apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor.

[0016] Figure 2 The diagram shows the structure of a phosphorus burning nozzle in a device for directly preparing phosphoric acid from high-purity phosphorus vapor.

[0017] Figure 3 Schematic diagram of the structure of AA in a device for directly preparing phosphoric acid from high-purity phosphorus vapor.

[0018] Figure 4 This is a schematic diagram of the main structure after installation of a single-piece swirl guide vane in a device for directly preparing phosphoric acid from high-purity phosphorus vapor. Figure 5 This is a schematic diagram of the top view of the structure after installation of a single-piece swirl guide vane in a device for directly preparing phosphoric acid from high-purity phosphorus vapor.

[0019] Figure 6 This is a schematic diagram of the structure of a device for directly preparing phosphoric acid from high-purity phosphorus vapor.

[0020] Figure: 1, combustion tower; 2, hydration tower; 3, dilute acid tower; 4, cooling water tank; 5, demister; 6, venturi scrubber; 7, connecting pipe a; 8, connecting pipe b; 9, phosphorus burning nozzle; 10, swirl guide vane; 11, contraction section of venturi scrubber; 12, throat of venturi scrubber; 13, diffusion section of venturi scrubber; 101, circulating water outlet; 102, sewage outlet; 201, circulating acid outlet; 202, acid inlet; 203, acid injection port; 204, lower cooling water inlet; 205 , lower section cooling water outlet; 206, upper section cooling water inlet; 207, upper section cooling water outlet; 208, overflow weir acid inlet; 209, sewage outlet; 301, pure water inlet; 302, dilute acid inlet; 303, dilute acid outlet; 304, gas inlet; 305, gas outlet; 306 liquid level gauge port; 401, cold water layer; 501, high-purity phosphorus vapor inlet; 502, compressed air inlet; 801, thermometer a; 802, thermometer b; 901, pressure measuring point a; 902, pressure measuring point b. DETAILED DESCRIPTION

[0021] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0022] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "disposed" should be understood in a broad sense. For example, they may refer to fixed connection or disposition, detachable connection or disposition, or integral connection or disposition. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] See also Figures 1 to 3 In an embodiment of the present invention, an apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor includes a combustion tower 1, a hydration tower 2, and a dilute acid tower 3. A high-purity phosphorus vapor pipeline inlet 501 is fixedly provided at the bottom of the combustion tower 1. A compressed air pipeline inlet 502 is fixedly provided at the bottom of the combustion tower 1. The high-purity phosphorus vapor and compressed air enter the combustion tower 1, mix and burn fully to form phosphorus pentoxide gas. A thermometer b802 is fixedly provided at the bottom of the combustion tower 1. The thermometer detects the temperature inside the combustion tower 1. The combustion tower 1 and the hydration tower 2 are connected by a connecting pipe 7. The connecting pipe 7 is fixedly provided with a thermometer a801. The thermometer a801 detects the temperature of the connecting pipe, and the temperature must reach above 400°C. It should be further explained in the present invention that a cooling water tank 4 is fixedly provided on the top of the combustion tower 1, and a cooling water layer 401 is fixedly provided around the combustion tower 1. The cooling water tank 4 supplies water to the cooling water layer 401, and the cooling water layer 401 cools the combustion tower 1; a circulating water outlet 101 is fixedly provided at the bottom of the combustion tower 1, and the circulating water outlet 101 is externally connected to a circulating water tank; It should be further explained in the present invention that the phosphorus pentoxide gas formed in the combustion tower 1 enters from the top of the hydration tower 2 through the connecting pipe 7, the top of the hydration tower 2 is fixedly provided with an acid inlet 209, the top of the hydration tower 2 is fixedly provided with an overflow weir acid inlet 208, the top of the hydration tower 2 is fixedly provided with an acid spray port 203, the top of the acid spray port 203 is a spiral spray head, the top of the hydration tower 2 is fixedly provided with an upper cooling water outlet 207, the middle of the hydration tower 2 is fixedly provided with an upper cooling water inlet 206, the middle of the hydration tower 2 is fixedly provided with a lower cooling water outlet 205, the bottom of the hydration tower 2 is fixedly provided with a circulating acid outlet 201, and the bottom of the hydration tower 2 is fixedly provided with a lower cooling water inlet 204; It should be further explained in the present invention that a demister 5 is fixedly provided at the top of the hydration tower 2, and the bottom of the hydration tower 2 and the top of the dilute acid tower 3 are connected by a connecting pipe 8, and the connecting pipe 8 enters the dilute acid tower 3 from the top of the dilute acid tower 3 and extends to the bottom of the dilute acid tower 3, the connecting pipe 8 is fixedly provided with a pressure measuring point a901, a venturi scrubber 6 is fixedly provided in the middle of the connecting pipe 8, a gas inlet 304 is fixedly provided at the bottom of the connecting pipe 8, a gas outlet 305 is fixedly provided at the top of the dilute acid tower 3, and the gas outlet 305 is connected to the demister 5, a pure water inlet 301 is fixedly provided at the top of the dilute acid tower 3, a dilute acid inlet 302 is fixedly provided at the top of the dilute acid tower 3, a pressure measuring point b902 is fixedly provided at the top of the dilute acid tower 3, and the pressure measuring point is detected by a U-type pressure gauge, a liquid level gauge port 306 is fixedly provided at the bottom of the dilute acid tower 3, and a dilute acid outlet 303 is fixedly provided at the bottom of the dilute acid tower.

[0025] It should be further explained in the present invention that a phosphorus burning nozzle 9 is fixedly provided at the bottom of the combustion tower 1, and a swirl guide blade 10 is provided inside the phosphorus burning nozzle 9. The swirl guide blade 10 is composed of four and is distributed on the gas nozzle. The swirl guide blade 10 is spiral; the radial spiral angle of each swirl guide blade 10 is 120 degrees; the length of the swirl guide blade 10 along the axial direction of the gas nozzle is 200 mm, and the air entering the burner is in a tangential swirl shape, and the spiral direction of the swirl guide blade 10 is consistent with the rotation direction of the air.

[0026] It should be further explained in the present invention that the venturi scrubber 6 includes a contraction section 11 of the venturi scrubber, the inlet of the contraction section 11 of the venturi scrubber is sealed and welded to the connecting pipe 8 at the bottom of the hydration tower 2, and the outlet of the venturi scrubber is sealed and welded to the gas inlet 304 at the top of the dilute acid tower 3; one end of the dilute acid pipe is connected to the dilute acid injection interface 4 of the throat 12 of the venturi scrubber, and the other end is connected to the dilute acid inlet 302 of the dilute acid tower 3; when the gas enters the venturi scrubber, it is accelerated in the contraction section, forming a negative pressure in the throat, sucking in the dilute acid and forming high-speed atomized droplets, which are fully mixed with the gas and then enter the diffusion section to decelerate, thereby achieving efficient capture of impurities.

[0027] To prepare phosphoric acid, high-purity phosphorus vapor and compressed air are first introduced into combustion tower 1 in a predetermined ratio through the air inlet pipe at the bottom of combustion tower 1. Within combustion tower 1, phosphorus pentoxide gas is fully combusted to form. During the combustion process, the temperature is monitored in real time using thermometer b802 to ensure complete combustion. The generated phosphorus pentoxide gas enters hydration tower 2 via connecting pipe 7. Simultaneously, acid is added through acid inlet 202 and overflow weir acid inlet 208 at the top of hydration tower 2. The acid is atomized and sprayed through a spiral spray nozzle at acid spray port 203, where it fully contacts the phosphorus pentoxide gas. The phosphorus pentoxide gas dissolves in water to form phosphoric acid. During this process, the temperature within hydration tower 2 is controlled via upper cooling water inlet 206, upper cooling water outlet 207, lower cooling water inlet 204, and lower cooling water outlet 205 to maintain the reaction at the optimal temperature. The generated phosphoric acid solution is discharged from circulating acid outlet 201 at the bottom of hydration tower 2 and enters dilute acid tower 3 via connecting pipe 8. Within dilute acid tower 3, pure water and dilute acid are introduced through pure water inlet 301 and dilute acid inlet 302, respectively, to further scrub and absorb the gas. A Venturi scrubber 6 connected to the middle of pipeline 8 enhances the scrubbing effect. Finally, the phosphoric acid product is discharged from dilute acid outlet 303 at the bottom of dilute acid tower 3, while the gas is discharged through gas outlet 305 and further processed through demister 5.

[0028] It should be noted that the present invention is an apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor. All components are universal standard parts or components known to those skilled in the art. The structure and principles thereof are known to those skilled in the art through technical manuals or routine experimental methods. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims, not the above description, and is intended to encompass all variations within the meaning and scope of the equivalents of the claims. Any reference numerals in the claims should not be construed as limiting the claims to which they relate. Furthermore, it should be understood that although this specification describes embodiments, not each embodiment contains only one independent technical solution. This narrative format is intended for clarity only, and those skilled in the art should consider the specification as a whole. The technical solutions in the various embodiments may also be appropriately combined to form other embodiments that are understandable to those skilled in the art.

Claims

1. An apparatus for directly preparing phosphoric acid from high-purity phosphorus vapor, characterized in that: The invention comprises a combustion tower (1), a hydration tower (2) and a dilute acid tower (3), wherein the combustion tower (1) is connected to a high-purity phosphorus vapor pipeline and a compressed air pipeline, the tops of the combustion tower (1) and the hydration tower (2) are connected via a phosphorus pentoxide gas conduit, and the bottom of the hydration tower (2) is connected to the top of the dilute acid tower (3) via a pipeline.

2. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 1, characterized in that: A high-purity phosphorus vapor inlet pipe (501) and a compressed air inlet pipe (502) are fixedly provided at the outer end of the combustion tower (1), and the two are connected to the lower part of the combustion tower (1), and a fixed thermometer b (802) is provided at the connection point; a cooling water tank (4) is provided at the top of the combustion tower (1), and a cooling water interlayer (401) is provided around it, and the cooling water tank (4) supplies water to the cooling water interlayer (401); a fixed thermometer a (801) is provided on the connecting pipe (7) between the combustion tower (1) and the hydration tower (2), and a circulating water outlet (101) and a sewage outlet (102) are provided at the bottom of the combustion tower (1).

3. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 1, characterized in that: The top of the hydration tower (2) is fixedly provided with a demister (5), and the demister (5) has three layers of mesh; the top of the hydration tower (2) is fixedly provided with an acid inlet (202), an overflow weir acid inlet (208) and an acid spray port (203), and the acid spray port (203) is fixedly provided with a spiral spray head; the top of the hydration tower (2) is provided with an upper cooling water outlet (207), the middle is provided with an upper cooling water inlet (206) and a lower cooling water outlet (205), and the bottom is provided with a circulating acid outlet (201), a lower cooling water inlet (204) and a sewage outlet (209).

4. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 1, characterized in that: The top of the dilute acid tower (3) is fixedly provided with a gas outlet (305), a pure water inlet (301), a dilute acid inlet (302) and a pressure measuring point b (902). The pressure measuring point b (902) is fixedly provided with a connecting pipe (8) in the dilute acid tower (3), and the connecting pipe (8) extends from the top to the bottom of the dilute acid tower (3). A venturi scrubber (6) is fixedly provided in the middle, connected to a DN25 dilute acid pipe, and a gas inlet (304) is fixedly provided at the tail. The bottom of the dilute acid tower (3) is fixedly provided with a dilute acid outlet (303) and a liquid level gauge port (306).

5. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 2, characterized in that: The range of the thermometer b (802) is 0-2000°C, and the range of the thermometer a (801) is 0-1000°C. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 4 is characterized in that the pressure measuring point b (902) is detected by a U-type pressure gauge with a measuring range of ±3 kPa and a pressure gauge length of 2 meters.

6. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 3, characterized in that: The spray angle of the acid spray port (203) is ≥60°.

7. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 1, characterized in that: A phosphorus burning nozzle (9) is fixedly provided at the bottom of the combustion tower (1), and a swirl guide leaf (10) is provided inside the phosphorus burning nozzle (9). The swirl guide leaf (10) is composed of four and is distributed on the gas nozzle. The swirl guide leaf (10) is spiral-shaped; the radial spiral angle of each swirl guide leaf (10) is (120) degrees; the length of the swirl guide leaf (10) along the axial direction of the gas nozzle is 200 mm, and the air enters the burner in a tangential swirl shape, and the spiral direction of the swirl guide leaf (10) is consistent with the rotation direction of the air.

8. The device for directly preparing phosphoric acid from high-purity phosphorus vapor according to claim 4, characterized in that: The venturi scrubber (6) comprises a contraction section (11) of the venturi scrubber, the inlet of the contraction section (11) of the venturi scrubber is sealed and welded to the connecting pipe (8) at the bottom of the hydration tower (2), and the outlet of the venturi scrubber is sealed and welded to the gas inlet (304) at the top of the dilute acid tower (3); one end of the dilute acid pipe is connected to the dilute acid injection interface (4) of the throat (12) of the venturi scrubber, and the other end is connected to the dilute acid inlet (302) of the dilute acid tower (3).

9. A method for directly preparing phosphoric acid using the apparatus according to any one of claims 1 to 9, characterized in that: The following steps are involved: High-purity phosphorus vapor and compressed air are introduced into the combustion tower through the air inlet pipe at the bottom of the combustion tower, and are fully burned in the combustion tower to generate phosphorus pentoxide gas. During the combustion process, the temperature in the combustion tower is monitored by a thermometer; The generated phosphorus pentoxide gas enters the hydration tower through the connecting pipe at the top of the combustion tower and the hydration tower. The spiral spray head at the top of the hydration tower sprays the acid liquid into atomized form, which fully contacts the phosphorus pentoxide gas, causing the phosphorus pentoxide gas to dissolve in water to form phosphoric acid. At the same time, the temperature in the hydration tower is controlled by the cooling water inlet and outlet. The phosphoric acid solution at the bottom of the hydration tower enters the dilute acid tower through a pipeline. In the dilute acid tower, it is further treated by a venturi scrubber connected to the middle of the pipeline. At the same time, pure water and dilute acid are introduced into the top of the dilute acid tower to wash and absorb the gas. Finally, the phosphoric acid product is obtained from the dilute acid outlet at the bottom of the dilute acid tower, and the gas is discharged from the gas outlet.

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