Fixed proportion methanol air mixture device

Abstract

The application belongs to the technical field of gas mixing devices, and particularly relates to a fixed-proportion methanol mixed air-gas mixing device, which comprises a mixing pipe body with a contraction section, a throat section and an expansion section sequentially communicated along the airflow direction, an air inlet of the contraction section, a mixed gas outlet of the expansion section, a methanol vapor introduction pipe in communication with the side wall of the throat section and used for introducing methanol vapor into the throat section to mix with air, and a predetermined relationship between the flow area of the throat section, the flow area of the methanol vapor introduction pipe and the design pressure of the inlet of the mixing pipe body, so that the dew point temperature of the mixed gas output by the device is not higher than-3.5 DEG C under the standard atmospheric pressure, and the problems of pipeline condensation and mixed precision drift of the existing device and high maintenance cost are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of gas mixing equipment, specifically a fixed-ratio methanol-air gas mixing device. Background Technology

[0002] Methanol-air-gas mixtures are an important alternative to clean residential gas, and the accuracy of their mixing directly determines the reliability of the gas supply system. Existing methanol-air-gas mixing devices mostly employ adjustable structures, relying on manual or automatic adjustment of the methanol vapor-air mixing ratio, which has the following core drawbacks:

[0003] 1. In existing equipment, when the methanol concentration is too high, the dew point temperature of the mixed gas increases, and methanol condensation is likely to occur during normal temperature transportation, causing pipeline blockage and gas supply interruption, which seriously affects the user's use.

[0004] 2. During long-term operation, the adjustable components are prone to wear and aging, which can cause the mixture ratio to drift, affecting the combustion effect and posing a risk of condensation. At the same time, the adjustable components require regular calibration and maintenance, resulting in high operation and maintenance costs.

[0005] Therefore, the present invention provides a fixed-ratio methanol-air-gas mixing device. Summary of the Invention

[0006] In order to overcome the shortcomings of existing technologies and solve the problems of pipeline condensation, mixing accuracy drift, and high maintenance costs in existing equipment.

[0007] The technical solution adopted by this invention to solve its technical problem is: a fixed-ratio methanol-air-gas mixing device according to this invention, comprising:

[0008] The mixing tube has a constriction section, a throat section, and an expansion section connected sequentially along the airflow direction. The inlet of the constriction section is an air inlet, and the outlet of the expansion section is a mixed gas outlet.

[0009] A methanol vapor inlet pipe is connected to the side wall of the throat section and is used to introduce methanol vapor into the throat section to mix with air.

[0010] The flow area of ​​the throat section, the flow area of ​​the methanol vapor inlet pipe, and the inlet design pressure of the mixing pipe are fixedly configured according to a predetermined relationship, so that the dew point temperature of the mixed gas output by the device is not higher than -3.5℃ under standard atmospheric pressure.

[0011] No adjustable components are installed inside the mixing tube.

[0012] Preferably, the volume concentration of methanol vapor in the mixed gas is less than 6.0%.

[0013] Preferably, the volume concentration of methanol vapor in the mixed gas is 4.5% to 5.5%.

[0014] Preferably, the end of the methanol vapor inlet pipe is provided with a one-way flow guiding structure, which allows methanol vapor to flow from the methanol vapor inlet pipe to the throat section and prevents the gas from flowing in reverse.

[0015] The unidirectional flow guiding structure is a multi-layer physical locking structure, including at least one or a combination of the following: an elastic duckbill valve, a gravity ball check valve, and a spring return baffle.

[0016] Preferably, the unidirectional flow-guiding structure is a three-layer physical locking structure, which includes, in sequence along the methanol vapor flow direction, an elastic duckbill valve, a gravity ball check valve, and a spring reset baffle.

[0017] Preferably, the inner diameter of the throat section is 3.5-5.0 mm, the orifice diameter of the methanol vapor inlet pipe is 1.5-2.2 mm, and the inlet design pressure is 8-12 kPa.

[0018] Preferably, the air inlet is provided with an inlet pressure stabilizing chamber.

[0019] Preferably, a static mixing core is provided at the outlet of the mixed gas.

[0020] Preferably, the device is integrally formed by precision casting or CNC machining.

[0021] Preferably, the unidirectional flow guidance structure further includes a flame arrester disposed at the inlet end of the methanol vapor inlet pipe.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This system precisely controls the dew point temperature of the output mixed gas to below -3.5℃ by fixing geometric parameters, ensuring that methanol never condenses during normal temperature transportation, thus completely solving the problems of pipeline blockage and gas supply interruption.

[0024] 2. With no adjustable parts, it eliminates human error and parameter drift. After 30 days of continuous operation, the methanol concentration drift is less than 0.5%, which is far superior to the 3.2% drift of existing adjustable mixers.

[0025] 3. With no easily damaged adjustable parts, no need for regular calibration and maintenance, and an average annual failure rate of less than 0.1 times, the operation and maintenance costs are greatly reduced. Attached Figure Description

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] Figure 1 This is a structural cross-sectional view of the present invention.

[0028] In the diagram: 1. Mixing pipe; 11. Contraction section; 12. Throat section; 13. Expansion section; 14. Air inlet; 15. Mixed gas outlet; 2. Methanol vapor inlet pipe; 3. One-way flow guide structure; 31. Elastic duckbill valve; 32. Gravity ball check valve; 33. Spring return baffle. Detailed Implementation

[0029] I. Core Design Principles

[0030] The core of this invention lies in: by fixing the flow area of ​​the throat section, the flow area of ​​the methanol vapor inlet pipe, and the inlet design pressure, the methanol concentration of the output mixed gas is locked at a specific value, and then the dew point temperature is precisely controlled not to exceed -3.5℃ by the Antoine equation.

[0031] The design process is as follows:

[0032] Determine the target dew point temperature (≤-3.5℃) → Calculate the target methanol concentration (4.76%) using the Antoine equation → Calculate the throat section inner diameter, methanol pipe orifice diameter, and inlet pressure using the Venturi tube flow formula → Fixed parameters, no adjustment required.

[0033] II. Parameter Design Derivation Process

[0034] Step 1: Determine the methanol concentration based on the target dew point temperature;

[0035] Antoine's equation is expressed as: lgP = A - B / (T + C);

[0036] in:

[0037] P is the partial pressure of methanol vapor (mmHg);

[0038] T is the dew point temperature (°C);

[0039] A = 7.87863, B = 1473.11, C = 230.0 (Antoine constant for methanol).

[0040] At standard atmospheric pressure, the total pressure is 760 mmHg.

[0041] Assuming the target dew point temperature is T = -3.5℃, substituting this into the Antoine equation:

[0042] lgP = 7.87863 - 1473.11 / (-3.5 + 230.0) = 7.87863 - 1473.11 / 226.5 =7.87863 - 6.5038 = 1.37483;

[0043] Therefore, P = 10^1.37483 ≈ 36.2 mmHg;

[0044] The volume concentration of methanol, C_meoh, is calculated as: P / 760 × 100% = 36.2 / 760 × 100% = 4.76%.

[0045] Therefore, it is determined that in order to achieve a dew point temperature ≤ -3.5℃, the methanol volume concentration must be controlled below 4.76%, preferably corresponding to an air to methanol vapor volume dilution ratio of 20:1.

[0046] Step 2: Determine the geometric parameters based on the Venturi principle.

[0047] The formula for the flow velocity at the throat of a Venturi tube is: v = √(2ΔP / ρ);

[0048] in:

[0049] v is the throat velocity (m / s);

[0050] ΔP is the pressure difference (Pa) between the throat and the inlet;

[0051] ρ is the air density (taken as 1.205 kg / m³ at 20℃).

[0052] Airflow formula: Q1 = A1 × v;

[0053] in:

[0054] A1 is the flow area of ​​the throat section (m²).

[0055] Q1 is the air volume flow rate (m³ / s).

[0056] Methanol vapor flow rate formula: Q2 = A2 × √(2ΔP' / ρ');

[0057] in:

[0058] A2 is the flow area of ​​the methanol vapor inlet pipe (m²).

[0059] ΔP' is the pressure difference (Pa) between the two ends of the methanol vapor inlet pipe;

[0060] ρ' is the density of methanol vapor (1.17 kg / m³ at 20℃).

[0061] To achieve a dilution ratio of 20:1, the following condition must be met: Q1 / Q2 = 20;

[0062] That is: A1 × √(2ΔP / ρ) / [A2 × √(2ΔP' / ρ')] = 20;

[0063] Under the condition of a fixed inlet design pressure P_in, ΔP and ΔP' are determined by the system. By adjusting the ratio of A1 and A2, the above equation can be made true.

[0064] Step 3: Determining the parameter range

[0065] Based on the above theoretical derivation and considering the heat load requirements of different gas supply scales (500 households, 1000 households, and 2000 households), the following parameter ranges are calculated:

[0066] Throat section inner diameter <![CDATA[D1= √(4A1 / π)]]> 4.2mm 3.5-5.0mm Methanol tube aperture <![CDATA[D2= √(4A2 / π)]]> 1.8mm 1.5-2.2mm Entrance design pressure P_in 10kPa 8-12kPa

[0067] The basis for determining the parameter boundaries is: the lower limit of the throat section inner diameter is 3.5mm: when the inner diameter is less than 3.5mm, the flow area is too small and the air flow is insufficient to meet the minimum heat load requirements of 500 households; at the same time, the throat velocity is too high, the pressure loss increases, and the system efficiency decreases.

[0068] Upper limit of throat inner diameter 5.0mm: When the inner diameter is greater than 5.0mm, the flow velocity in the throat decreases, the generated negative pressure is insufficient to fully introduce methanol vapor, the mixing ratio deviates from the target value, and the dew point temperature rises to above -3.5℃.

[0069] The lower limit of methanol pipe orifice diameter is 1.5 mm: When the orifice diameter is less than 1.5 mm, the methanol vapor flow rate is insufficient, the mixed gas concentration is less than 4.5%, and the calorific value of combustion is insufficient.

[0070] The upper limit of the methanol pipe orifice diameter is 2.2 mm: When the orifice diameter is greater than 2.2 mm, the methanol vapor flow rate is too high, the mixed gas concentration is higher than 5.5%, the dew point temperature rises to above -3.5℃, and there is a risk of condensation.

[0071] Lower limit of inlet pressure: 8 kPa. When the pressure is too low, the negative pressure at the throat is insufficient, the ejection capacity decreases, and the mixing ratio becomes unstable.

[0072] The upper limit of the inlet pressure is 12 kPa: When the pressure is too high, the requirements for the upstream fan will increase, and the excessive flow velocity in the throat may generate noise and vibration.

[0073] III. Examples

[0074] Example 1 (1000 households, preferred solution)

[0075] This embodiment provides a fixed-ratio methanol-air-gas mixing device, suitable for centralized gas supply stations serving 1000 households. Specific parameters are as follows:

[0076] The throat section 12 has an inner diameter Φ = 4.2 mm (flow area approximately 13.85 mm²) and a length of 12.6 mm (3 times the inner diameter of the throat). The methanol vapor inlet pipe 2 has an orifice diameter of 1.8 mm (flow area approximately 2.54 mm²) and is perpendicularly connected to the side wall of the throat section 12. The inlet design pressure is 10 kPa (gauge pressure).

[0077] By fixing the ratio between the three components, a volume dilution ratio of air to methanol vapor of 20:1 is achieved, resulting in a methanol volume concentration of 4.76% in the output mixture. Based on the Antoine equation, the dew point temperature at standard atmospheric pressure is -3.5℃, and there is no condensation during normal temperature transport.

[0078] The rated methanol steam processing capacity of this embodiment is 150 kg / h. After 30 days of continuous operation, the methanol concentration drift was 0.3% and the gas mixture non-uniformity was 2.8%, all of which are superior to the existing technology.

[0079] Example 2 (500 households)

[0080] The difference between this embodiment and Embodiment 1 is as follows: the inner diameter of the throat section Φ = 3.8 mm (flow area approximately 11.34 mm²), the orifice diameter of the methanol vapor inlet pipe = 1.5 mm (flow area approximately 1.77 mm²), and the inlet design pressure is 8 kPa. The rated methanol vapor processing capacity is 75 kg / h. The methanol volume concentration of the output mixed gas is 4.8%, and the dew point temperature calculated using the Antoine equation is -3.2℃. The remaining structure is the same as in Embodiment 1.

[0081] Example 3 (2000 households)

[0082] The difference between this embodiment and Embodiment 1 is as follows: the inner diameter of the throat section Φ = 5.0 mm (flow area approximately 19.63 mm²), the orifice diameter of the methanol vapor inlet pipe = 2.2 mm (flow area approximately 3.80 mm²), and the inlet design pressure is 12 kPa. The rated methanol vapor processing capacity is 300 kg / h. The methanol volume concentration of the output mixed gas is 4.7%, and the dew point temperature calculated using the Antoine equation is -3.6℃. The remaining structure is the same as in Embodiment 1.

[0083] Example 4 (Economy Model)

[0084] The difference between this embodiment and Embodiment 1 is that the methanol vapor inlet pipe (2) has a one-way flow guide structure (3) at its end, which is a single-layer gravity ball check valve. The rest of the structure is the same as in Embodiment 1. The dew point temperature of the output mixed gas is still -3.5℃.

[0085] Example 5 (Enhanced)

[0086] The difference between this embodiment and Embodiment 1 is that the methanol vapor inlet pipe (2) is provided with a one-way flow guide structure (3) at its end. This one-way flow guide structure is a three-layer physical locking structure, which includes, in sequence along the methanol vapor flow direction, an elastic duckbill valve (31), a gravity ball check valve (32), and a spring return baffle (33). The rest of the structure is the same as in Embodiment 1. The dew point temperature of the output mixed gas is still -3.5℃.

[0087] Comparative Example 1 (Condensation caused by parameter deviation)

[0088] The difference between Comparative Example 1 and Example 1 is that the throat section inner diameter Φ = 6.0 mm, the methanol vapor inlet pipe orifice diameter = 2.5 mm, and the inlet design pressure is 15 kPa. The methanol volume concentration of the output mixed gas is 13%, and according to the Antoine equation, the dew point temperature under standard atmospheric pressure is 21°C, which is higher than -3.5°C. Experiments show that at a normal temperature of 20°C, obvious methanol condensate appears on the inner wall of the pipe, and the pipe becomes blocked after 24 hours of operation, resulting in gas supply interruption.

[0089] Comparative Example 2 (Parameter deviation leading to excessive concentration)

[0090] The difference between Comparative Example 2 and Example 1 is that the inner diameter of the throat section Φ = 3.0 mm, the orifice diameter of the methanol vapor inlet pipe = 1.0 mm, and the inlet design pressure is 6 kPa. The methanol volume concentration of the output mixed gas is 3.8%, which is lower than 4.5%, resulting in insufficient calorific value and affecting user operation.

[0091] The above comparative examples demonstrate that when the parameters deviate from the range defined in this invention, either the dew point temperature increases, leading to condensation in the pipeline, or the methanol concentration is too low, resulting in insufficient calorific value. Therefore, the parameter range defined in this invention is the key technical boundary for solving the above problems.

[0092] IV. Additional Technical Features

[0093] 1. Inlet pressure regulating chamber;

[0094] As a preferred embodiment, an inlet pressure stabilizing chamber is provided at air inlet 14, with a volume 50-100 times that of the throat section 12. The function of the inlet pressure stabilizing chamber is to stabilize air pressure and eliminate the impact of upstream fan pulsation on mixing accuracy. The inner wall can be lined with sound-absorbing material to reduce airflow noise.

[0095] 2. Static mixing core;

[0096] As a preferred option, a static mixing core is provided at the mixed gas outlet (15). The static mixing core consists of multiple layers of corrugated plates arranged in a cross pattern, with the angle between the corrugation directions of adjacent layers of corrugated plates being 60°-90°. Its function is to repeatedly separate, reverse, and mix methanol vapor and air as they flow through the corrugated plates, thereby improving the mixing uniformity. Experimental data show that after adding the static mixing core, the non-uniformity of the mixed gas decreased from 5.2% to 2.8%.

[0097] 3. One-piece molding and precision control;

[0098] As a preferred option, the entire device is integrally formed by precision casting or CNC machining. The inner diameter tolerance of the throat section (12) is controlled within ±0.02mm. High-precision manufacturing ensures the long-term stability of fixed parameters and avoids the mixing ratio deviating from the design value due to manufacturing errors.

[0099] 4. Flame arrester;

[0100] As a preferred option, the unidirectional flow structure (3) also includes a flame arrester installed at the inlet end of the methanol vapor inlet pipe. The flame arrester core is a corrugated stainless steel flame arrester core, which is used to prevent flame propagation and improve explosion-proof performance.

[0101] V. Verification of Beneficial Effects

[0102] To verify the beneficial effects of the present invention, the following comparative experiments were conducted:

[0103] Long-term methanol concentration drift (after 30 days of continuous operation) ＜0.5% 3.2% Output gas mixture dew point temperature stability Fluctuation <0.5℃ Fluctuation >3℃ Condensation in pipes at room temperature (20℃) No condensation If not properly adjusted, condensation may occur. Average annual failure rate <0.1 times 3.2 times

[0104] Experimental data show that the present invention is significantly superior to existing technologies in terms of mixing accuracy stability, dew point temperature control, pipeline condensation protection, and maintenance costs.

Claims

1. A fixed-ratio methanol-air mixture device, characterized by comprising: include: The mixing tube (1) has a constriction section (11), a throat section (12) and an expansion section (13) connected sequentially along the airflow direction. The inlet of the constriction section (11) is an air inlet (14), and the outlet of the expansion section (13) is a mixed gas outlet (15). A methanol vapor inlet pipe (2) is connected to the side wall of the throat section (12) for introducing methanol vapor into the throat section (12) to mix with air; The flow area of ​​the throat section (12), the flow area of ​​the methanol vapor inlet pipe (2), and the inlet design pressure of the mixing pipe (1) are fixedly configured according to a predetermined relationship so that the dew point temperature of the mixed gas output by the device is not higher than -3.5℃ under standard atmospheric pressure. No adjustable components are installed inside the mixing tube (1).

2. The fixed-ratio methanol air mixture gas mixing device according to claim 1, characterized in that: The volume concentration of methanol vapor in the mixed gas is less than 6.0%.

3. The fixed-ratio methanol-air-gas mixing device according to claim 2, characterized in that: The volume concentration of methanol vapor in the mixed gas is 4.5% to 5.5%.

4. The fixed-ratio methanol-air-gas mixing device according to claim 1, characterized in that: The methanol vapor inlet pipe (2) is provided with a one-way flow guide structure (3) at the end. The one-way flow guide structure (3) allows methanol vapor to flow from the methanol vapor inlet pipe (2) to the throat section (12) and prevents the gas from flowing in the opposite direction. The unidirectional flow structure (3) is a multi-layer physical locking structure, including at least one of the following or a combination thereof: elastic duckbill valve (31), gravity ball check valve (32), and spring return baffle (33).

5. The fixed-ratio methanol-air-gas mixing device according to claim 4, characterized in that: The unidirectional flow structure (3) is a three-layer physical locking structure, which includes an elastic duckbill valve (31), a gravity ball check valve (32) and a spring reset baffle (33) in sequence along the methanol vapor flow direction.

6. The fixed-ratio methanol-air-gas mixing device according to claim 1, characterized in that: The inner diameter of the throat section (12) is 3.5-5.0 mm, the orifice diameter of the methanol vapor inlet pipe (2) is 1.5-2.2 mm, and the inlet design pressure is 8-12 kPa.

7. The fixed-ratio methanol-air-gas mixing device according to claim 1, characterized in that: An inlet pressure stabilizing chamber is provided at the air inlet (14).

8. The fixed-ratio methanol-air-gas mixing device according to claim 1, characterized in that: A static mixing core is provided at the gas outlet (15).

9. The fixed-ratio methanol-air-gas mixing device according to claim 1, characterized in that: The device is integrally formed by precision casting or CNC machining.

10. The fixed-ratio methanol-air-gas mixing device according to claim 4, characterized in that: The unidirectional flow structure (3) also includes a flame arrester installed at the inlet end of the methanol vapor inlet pipe (2).

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