Device for recovering chlorine-alkali chemical emptying hydrogen and applying chlorine-alkali chemical emptying hydrogen to caustic soda flake production combustion furnace

Abstract

The utility model relates to a chlor-alkali chemical emptying hydrogen recovery and caustic soda flake production combustion furnace device which comprises a gas furnace connected with a hydrogen buffer tank through a hydrogen pipeline. The hydrogen buffer tank is connected with the hydrogen control combination valve through a pipeline; the hydrogen control combination valve is connected in parallel with the hydrogen distribution table and the hydrogen flame arrester through pipelines; an igniter for igniting natural gas or hydrogen and a pipeline connected with the discharge port are arranged on the gas furnace; and the hydrogen buffer tank is connected with a nitrogen header pipe through a nitrogen pipeline. According to the utility model, the hydrogen emptying pipeline is modified, and the gas furnace is connected with the hydrogen buffer tank through the hydrogen pipeline, so that the byproduct hydrogen in a chlor-alkali chemical device is fully utilized as a combustion medium and is used for the low-nitrogen oxygen combustor for co-combustion of natural gas and hydrogen, and various combustion modes such as single combustion of natural gas or hydrogen and the like are formed; and the emission of nitrogen oxides in the tail gas is reduced.

Description

Technical Field

[0001] This invention belongs to the field of chlor-alkali chemical technology, specifically relating to a device for recovering vented hydrogen in chlor-alkali chemical processes and for use in a combustion furnace for caustic soda production. Background Technology

[0002] Sodium hydroxide flakes, also known as caustic soda, are an important inorganic chemical raw material and a major product of the chlor-alkali chemical industry. Its production involves electrolyzing brine to generate sodium hydroxide, along with byproducts chlorine and hydrogen. Finally, caustic soda flakes are obtained through evaporation and solid alkali calcination processes.

[0003] The hydrogen produced during the production of caustic soda flakes at the inventor's workplace is typically treated by venting, which is both wasteful and uneconomical. Furthermore, the solid caustic soda calcination process, which involves evaporating water from sodium hydroxide, requires a gas-fired furnace as a heat source. This furnace usually uses natural gas as fuel. After the natural gas is ignited, the resulting exhaust gas needs to be emitted, and the nitrogen oxide content must comply with the national standard "Emission Standard of Pollutants for Caustic Soda and Polyvinyl Chloride Industry (GB15581-2016)". Therefore, there is a practical need to reduce nitrogen oxide emissions. Summary of the Invention

[0004] In accordance with the problems mentioned in the background art, the present invention provides an apparatus for recovering vented hydrogen in chlor-alkali chemical industry and for use in a combustion furnace for caustic soda production. The apparatus includes a gas-fired furnace, which is connected to a hydrogen buffer tank via a hydrogen pipeline. The hydrogen buffer tank is connected to a hydrogen control combination valve via a pipeline, and the hydrogen control combination valve is connected to a hydrogen distribution platform via a pipeline. The gas-fired furnace is equipped with an igniter for igniting natural gas or hydrogen, and a pipeline connected to an exhaust port is also provided on the furnace. The hydrogen control combination valve is connected to a hydrogen flame arrester via a pipeline.

[0005] Preferably, the hydrogen buffer tank is connected to the nitrogen main pipe via a nitrogen pipeline.

[0006] Furthermore, the hydrogen buffer tank is equipped with a nitrogen inlet connection and a cleaning exhaust gas connection. Nitrogen is introduced from the nitrogen main pipe in the caustic soda flakes in the caustic soda unit, and is connected to the nitrogen inlet connection through nitrogen pipelines N-1 and N-11. A combination valve is installed on pipeline N-11. The cleaning exhaust gas is discharged through pipeline VT-1, and a combination valve is installed on pipeline VT-1.

[0007] Furthermore, the hydrogen buffer tank is equipped with a hydrogen inlet connection terminal. Hydrogen is introduced from pipeline H-1 where the hydrogen distribution station is located, and is introduced to the hydrogen inlet connection terminal through hydrogen control combination valve and hydrogen pipeline H-2.

[0008] Preferably, a combination valve gauge is installed near the end of pipeline H-2 where the hydrogen buffer tank is located.

[0009] Furthermore, the hydrogen buffer tank is provided with a hydrogen exhaust connection end, which is connected to the gas furnace through a hydrogen pipeline H-21, and a check valve is provided on the hydrogen pipeline H-21.

[0010] Furthermore, a pipeline N-12 is connected to the nitrogen pipeline N-1.

[0011] Furthermore, the exhaust port of the gas furnace is connected to pipe VT-2, a radiator is installed on pipe VT-2, the ends of pipe VT-1 and pipe VT-2 are connected to the exhaust port, and another heat exchanger is provided at the exhaust port.

[0012] Preferably, the gas furnace is a low-NOx burner suitable for co-firing natural gas and hydrogen.

[0013] Preferably, the end of the discharge outlet is located on the roof of the building; the heat exchanger installed at the discharge outlet is 3m above the roof of the building, and the roof of the building is about 8m above the ground.

[0014] Beneficial effects:

[0015] This invention improves the equipment used in the caustic soda flake process. By modifying the hydrogen venting pipeline, the gas-fired furnace is connected to a hydrogen buffer tank via a hydrogen pipeline. This fully utilizes hydrogen, a byproduct of the chlor-alkali chemical plant, as a combustion medium. The use of a low-NOx burner for co-firing natural gas and hydrogen creates multiple combustion modes, allowing for either natural gas or hydrogen combustion alone, or co-firing of natural gas and hydrogen. This significantly reduces nitrogen oxide emissions in the exhaust gas, far below the special emission limit of 120 mg / m³ in GB15581-2016 "Emission Standard for Pollutants from Caustic Soda and Polyvinyl Chloride Industries". 3 This meets the requirements, achieves the goal of comprehensive resource utilization, and improves economic and environmental benefits. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a structural block diagram of the device proposed in this invention;

[0018] Figure 2 This is a schematic diagram of the equipment process layout of the device proposed in this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The inventor's workplace's "300,000 tons / year chlor-alkali chemical plant" production project generates approximately 500-900 Nm³ of excess hydrogen as a byproduct of the hydrogen electrolysis process. 3 / h, venting would result in resource waste. The inventor's unit uses a gas-fired furnace, a common type of caustic soda flakes production equipment in China, as auxiliary equipment for caustic soda flakes production, with a designed nitrogen oxide content of 200mg / m³ in the tail gas emission. 3 However, the actual nitrogen oxide emissions during operation are 160-180 mg / m³. 3 The exhaust emissions were tested and found to meet the standards stipulated in the national standard "Emission Standard of Pollutants for Caustic Soda and Polyvinyl Chloride Industry (GB15581-2016)". To further improve the existing production process and reduce nitrogen oxide emissions, the byproduct hydrogen was used in the production process to replace natural gas, which would further reduce nitrogen oxide emissions.

[0021] Example 1: Addressing the issue of hydrogen venting as a byproduct and the current practice of using natural gas-fired furnaces in caustic soda production, this invention provides a device for recovering vented hydrogen in chlor-alkali chemical plants and its application in a combustion furnace for caustic soda production. Please refer to the attached document. Figure 1 The system includes a gas-fired furnace, which serves as the heat source for the evaporation and solid caustic soda calcination process to produce caustic soda flakes. An igniter is installed on the gas-fired furnace to ignite the natural gas or hydrogen entering the furnace. The exhaust gas produced by the combustion reaction is discharged through a pipeline via an exhaust port. The gas-fired furnace is connected to a hydrogen buffer tank via a hydrogen pipeline. The hydrogen buffer tank is connected to a hydrogen control combination valve via a pipeline and is used to temporarily store hydrogen supplied from the hydrogen distribution station. A small amount of byproduct hydrogen is vented by a hydrogen flame arrester connected to the hydrogen control combination valve. The hydrogen buffer tank is connected to a nitrogen main pipeline via a pipeline, and nitrogen is used as the process gas for purging the hydrogen buffer tank.

[0022] The aforementioned device uses the hydrogen produced by electrolyzing brine as fuel for a gas-fired furnace. On the one hand, it provides a heat source for the solid alkali calcination process. On the other hand, the main component of the exhaust gas after combustion is H2O, which will not cause environmental pollution when it is released to the outside. This fully recycles hydrogen resources and directly reduces the amount of nitrogen oxides emitted in the exhaust gas when using natural gas as fuel.

[0023] Example 2: Please refer to the appendix Figure 2 A more specific implementation method in the above embodiments, wherein:

[0024] The hydrogen buffer tank is equipped with a nitrogen inlet connection and a cleaning tail gas exhaust connection. Nitrogen is introduced from the nitrogen main pipe of the caustic soda flakes in the caustic soda unit, and is connected to the nitrogen inlet connection through nitrogen pipelines N-1 and N-11. A combination valve is installed on pipeline N-11 to control the flow of nitrogen and prevent backflow. Nitrogen is introduced into the hydrogen buffer tank for cleaning. After cleaning and exhausting the cleaning tail gas in the hydrogen buffer tank, by-product hydrogen is introduced. The cleaning tail gas is discharged through pipeline VT-1, which is equipped with a combination valve for depressurization and discharge of the cleaning tail gas.

[0025] The hydrogen buffer tank is equipped with a hydrogen inlet connection. Hydrogen enters from pipeline H-1, where the hydrogen distribution station is located, passes through a hydrogen control combination valve, and then through hydrogen pipeline H-2 to the hydrogen inlet connection. The hydrogen control combination valve controls the flow of hydrogen and regulates pressure to maintain the pressure inside the hydrogen buffer tank at a specified value. When the hydrogen buffer tank can be filled with hydrogen, the hydrogen control combination valve controls the flow of hydrogen through pipeline H-2 to the hydrogen buffer tank. When the hydrogen buffer tank is full, a small amount of byproduct hydrogen is vented through pipeline H-1 and a hydrogen flame arrester under the control of the hydrogen control combination valve. Preferably, a combination valve can be further installed near pipeline H-2 where the hydrogen buffer tank is located. During maintenance and repair operations, this valve is used to control the venting of temporarily stored hydrogen in the hydrogen buffer tank. In this case, the hydrogen flows in the reverse direction through pipeline H-2, passes through the hydrogen control combination valve, and finally passes through the hydrogen flame arrester before being vented.

[0026] The hydrogen buffer tank is equipped with a hydrogen exhaust connection terminal, which is connected to the gas furnace through hydrogen pipeline H-21. A check valve is installed on hydrogen pipeline H-21 to prevent the reverse flow of hydrogen.

[0027] A nitrogen line N-12 is connected to the nitrogen line N-1. When cleaning and maintaining the gas furnace, nitrogen flows into the gas furnace through the nitrogen line N-12.

[0028] The exhaust port of the gas furnace is connected to pipe VT-2. A radiator is installed on pipe VT-2. The ends of pipes VT-1 and VT-2 are connected to the exhaust port. Another heat exchanger is installed at the exhaust port. The exhaust gas after the reaction is treated by the two-stage heat exchangers before being released into the atmosphere.

[0029] The end of the discharge outlet is located on the roof of the building, the heat exchanger is 3m above the roof of the building, and the roof of the building is about 8m above the ground.

[0030] The gas-fired furnace uses a low-NOx burner suitable for co-firing natural gas and hydrogen.

[0031] The aforementioned device recovers excess hydrogen produced as a byproduct of the hydrogen electrolysis process in a chlor-alkali chemical plant. It then uses a low-NOx burner suitable for co-firing natural gas and hydrogen to co-fire the gas. This combustion method, where hydrogen combustion is the primary fuel and natural gas is used as a supplement, allows for multiple combustion modes, including single combustion of natural gas or hydrogen, and co-firing of both. Consequently, the nitrogen oxide emissions from the exhaust gas are significantly lower than the special emission limit of 120 mg / m³ specified in GB15581-2016 "Emission Standard for Pollutants from Caustic Soda and Polyvinyl Chloride Industries". 3 In accordance with the requirements, and with a sufficient supply of byproduct hydrogen, the goal of zero emissions was achieved.

[0032] Based on the conversion of calorific values ​​between hydrogen and natural gas: at 101.325 kPa and 273.15 K, the higher heating value of methane is 39829 kJ / m³. 3 The lower heating value is 35807 kJ / m³. 3 The higher heating value of hydrogen is 12789 kJ / m³. 3 The lower heating value is 10779 kJ / m³. 3 For the same volume, its calorific value is approximately 3.3 times that of natural gas. Therefore, the amount of natural gas saved is:

[0033] 736Nm 3 / h / 3.3=223.03Nm 3 / h.

[0034] It is evident that this invention effectively utilizes vented hydrogen to replace part of the natural gas, thereby reducing the production cost of caustic soda flakes in chlor-alkali chemical plants.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for recovering vented hydrogen in chlor-alkali chemical industry and using it in a combustion furnace for caustic soda production, characterized in that, The system includes a gas-fired furnace, which is connected to a hydrogen buffer tank via a hydrogen pipeline; the hydrogen buffer tank is connected to a hydrogen control combination valve via a pipeline; the hydrogen control combination valve is connected in parallel with a hydrogen distribution platform and a hydrogen flame arrester via a pipeline; the gas-fired furnace is equipped with an igniter for igniting natural gas or hydrogen, and a pipeline connected to an exhaust port; the hydrogen buffer tank is connected to a nitrogen main pipeline via a nitrogen pipeline.

2. The apparatus for recovering hydrogen from venting in chlor-alkali chemical industry and for use in a combustion furnace for caustic soda production, as described in claim 1, is characterized in that... The hydrogen buffer tank is equipped with a nitrogen inlet connection and a cleaning exhaust gas connection. Nitrogen is introduced from the nitrogen main pipe in the caustic soda flakes in the caustic soda unit, and is connected to the nitrogen inlet connection through nitrogen pipelines N-1 and N-11. A combination valve is installed on pipeline N-11. The cleaning exhaust gas is discharged through pipeline VT-1, and a combination valve is installed on pipeline VT-1.

3. The apparatus for recovering vented hydrogen in chlor-alkali chemical industry and using it in a combustion furnace for caustic soda production, as described in claim 1, is characterized in that... The hydrogen buffer tank is equipped with a hydrogen inlet connection terminal. Hydrogen is introduced from pipeline H-1 where the hydrogen distribution station is located, and then introduced to the hydrogen inlet connection terminal through hydrogen pipeline H-2 via hydrogen control combination valve.

4. The apparatus for recovering hydrogen from venting in chlor-alkali chemical processes and for use in a combustion furnace for caustic soda production, as described in claim 3, is characterized in that... A combination valve gauge is installed near the end of pipeline H-2 where the hydrogen buffer tank is located.

5. The apparatus for recovering hydrogen from venting in chlor-alkali chemical processes and for use in a combustion furnace for caustic soda production, as described in claim 4, is characterized in that... The hydrogen buffer tank is equipped with a hydrogen exhaust connection end, which is connected to the gas furnace through a hydrogen pipeline H-21. A check valve is installed on the hydrogen pipeline H-21.

6. The apparatus for recovering hydrogen from venting gas in chlor-alkali chemical industry and using it in a combustion furnace for caustic soda production, as described in claim 2, is characterized in that... The nitrogen pipeline N-1 is connected to pipeline N-12.

7. The apparatus for recovering hydrogen from venting gas in chlor-alkali chemical industry and using it in a combustion furnace for caustic soda production, as described in claim 6, is characterized in that... The exhaust port of the gas furnace is connected to pipe VT-2. A radiator is installed on pipe VT-2. The ends of pipes VT-1 and VT-2 are connected to the exhaust port. Another heat exchanger is installed at the exhaust port.

8. The apparatus for recovering hydrogen from venting in chlor-alkali chemical processes and for use in a combustion furnace for caustic soda production, as described in claim 7, is characterized in that... The end of the discharge outlet is located on the roof of the building; the heat exchanger installed at the discharge outlet is 3m above the roof of the building, and the roof of the building is about 8m above the ground.

9. The apparatus for recovering hydrogen from venting gas in chlor-alkali chemical industry and using it in a combustion furnace for caustic soda production, as described in claim 8, is characterized in that... The gas furnace is equipped with a low-NOx burner suitable for co-firing natural gas and hydrogen.

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