CN105502289A - Separation method of hydrogen from catalytic cracking dry gas and system therefor - Google Patents

Abstract

The invention provides a method and system for separating hydrogen from catalytic cracking dry gas. The separation method includes the process of hydrating catalytic cracking dry gas and collecting hydrogen-rich gas, wherein the hydration reactor for realizing the hydration reaction has The following structure: the hydration reactor cavity has an inlet section, a throat section, and a stabilization section along the flow direction of the hydrate working fluid, and the flow area of the throat section is smaller than that of the inlet section and the stabilization section. The hydration reactor cavity corresponds to The side wall of the throat section is provided with an air inlet. The separation method of hydrogen in catalytic cracking dry gas provided by the present invention does not need the step of compressing and boosting catalytic cracking dry gas in the existing hydrate separation method to separate hydrogen in catalytic cracking dry gas, and has reliable operation and strong practical industrial application feasibility The advantages.

Description

A method and system for separating hydrogen from catalytic cracking dry gas

technical field

The invention relates to a method for separating hydrogen from catalytic cracking dry gas and a system thereof, belonging to the technical field of chemical industry.

Background technique

Since catalytic cracking dry gas contains a large amount of hydrogen and ethylene, their comprehensive utilization can save millions of tons of ethylene cracking raw materials and hydrogen production raw materials every year, and has billions of economic benefits. In recent years, many researchers have done a lot of research on the separation and recovery of hydrogen and ethylene in catalytic cracking dry gas. The existing methods for separating hydrogen and ethylene in catalytic cracking dry gas include cryogenic separation, absorption separation, membrane Separation method and hydrate separation method. However, the above methods have different defects, which restrict the recovery of hydrogen and ethylene in the catalytic cracking dry gas.

For example, although cryogenic separation technology is relatively mature, the disadvantage of high energy consumption has always restricted the popularization and application of this technology. Generally, it is only used in refineries with large processing capacity, areas with many petroleum catalytic cracking units, or oil refining- Chemical integration enterprises will consider using cryogenic separation technology to separate catalytic cracking dry gas; membrane separation method is still in the research stage for ethylene extraction, because the membrane used for separation is easily damaged by impurities, and at the same time there is membrane production cost Therefore, it has not been widely used; the absorption separation method has the advantages of simple process, common equipment and materials, mild operating conditions, low energy consumption, and high efficiency, but it can only deal with low-concentration gases and impurities removal is more difficult. The absorption separation method can be divided into physical absorption and chemical absorption according to the absorption method. Among them, the typical technology in the physical absorption method is the cold oil absorption method. This cold oil absorption method is a traditional technology for separating ethylene from catalytic cracking dry gas. It has the advantages of strong adaptability, low investment cost, and small process scale. There are defects of high energy consumption and large loss of ethylene; the chemical absorption method is also called π complex adsorption separation technology. This method has the advantages of large absorption capacity and high ethylene recovery rate, but it is rarely used in industrial applications.

The hydrate separation method is a new separation technology for separating low-boiling point mixed gases. The principle is to realize the separation of components in the mixed gas according to the difficulty of forming hydrates in different gases. Compared with the above-mentioned gas separation methods, the advantage of the hydrate separation method is that the conditions are relatively mild, and the separation and purification of mixed gases can be realized at a temperature between 0-15 °C, which has obvious advantages in terms of energy consumption and equipment investment. However, in the prior art, when using the hydrate separation method to separate hydrogen and ethylene in catalytic cracking dry gas, the catalytic cracking dry gas used as raw material gas is usually compressed and boosted, and then sent to the gas hydration reactor to be mixed with hydrate Working solution mixed. Due to limited field operation space and energy consumption of gas compressors, hydrate separation technology has not been widely used in the separation of hydrogen in catalytic cracking dry gas. Therefore, the study of a new hydrate method to separate hydrogen from catalytic cracking dry gas has always been concerned by researchers.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for separating hydrogen in catalytic cracking dry gas and its system, which does not need the existing hydrate separation method to separate hydrogen in catalytic cracking dry gas, which needs to compress catalytic cracking dry gas. The step of pressing has the advantages of reliable operation and strong feasibility of practical industrial application.

The invention provides a method for separating hydrogen from catalytic cracking dry gas, including the process of hydrating catalytic cracking dry gas and collecting hydrogen-rich gas, wherein,

The hydration reactor for realizing the hydration reaction has the following structure: the cavity of the hydration reactor has an inlet section, a throat section and a stabilizing section along the flow direction of the hydrate working fluid, and the flow area of the throat section is smaller than that of the inlet section and the stabilizing section, The hydration reactor cavity is provided with an air inlet corresponding to the side wall of the throat section;

The separation method includes: feeding the hydrate working fluid into the hydration reactor from the inlet section, making the catalytic cracking dry gas communicate with the hydration reactor through the inlet, and utilizing the hydrate working fluid generated by the hydrate working fluid flowing through the throat section The suction draws the dry gas from catalytic cracking to be separated into the hydration reactor, and causes the two to be mixed in the process of flowing to the stabilization section to undergo hydration reaction to generate hydrate slurry and hydrogen-rich gas;

The hydrate slurry and hydrogen-rich gas are sent to a hydrate separator to separate and collect the hydrogen-rich gas.

The above separation method of hydrogen in catalytic cracking dry gas mainly utilizes the principle of fluid mechanics, and utilizes the flow and pressure variation rules of the hydrate working fluid in different positions in the hydration reactor to realize the inhalation and automatic extraction of catalytic cracking dry gas. The process of pressurization and hydration separation. Specifically, when the hydrate working fluid is injected from the inlet section of the hydration reactor, when it reaches the throat section of the hydration reactor, the flow rate suddenly increases due to the sharp reduction of the cross-sectional area of the hydration reactor. The static pressure drops rapidly. Under the action of the pressure difference, the FCC dry gas is sucked into the hydration reactor and mixed with the hydrate working fluid. When the FCC dry gas and the hydrate working fluid reach the stable section of the hydration reactor, due to The expansion of the cross-sectional area of the flow increases the static pressure of the fluid, and the system pressure is higher than the pressure of the catalytic cracking dry gas entering the hydration reactor. When the static pressure of the fluid is greater than the hydrate formation pressure, the Components such as methane, ethane, ethylene, and carbon dioxide undergo hydration reactions with the hydrate working fluid to form a hydrate slurry, while a part of the gas phase of the hydrogen contained in the catalytic cracking dry gas is enriched to form a hydrogen-rich gas.

In a specific embodiment of the present invention, the hydrogen-rich gas is discharged from the top outlet of the hydrate separator to be collected, and the hydrate slurry is sent to the hydrate decomposer through the bottom outlet of the hydrate separator for decomposition , and the degassed hydrate working fluid decomposed is used for the hydration reaction cycle.

In a specific embodiment of the present invention, when the hydrate working fluid enters the hydration reactor, the temperature is 4-15° C., and the pressure is 1.0-5.1 MPa. The hydrate working fluid at this temperature and pressure is more conducive to forming a pressure difference when it flows through the throat section, thereby facilitating the cracking catalytic dry gas to be sucked into the stable section of the hydration reactor, so that it can undergo hydration reaction with the hydrate working fluid, A hydrate slurry is formed.

In a specific embodiment of the present invention, the inner diameter of the inlet section of the hydration reactor is 15-50 mm, the ratio of the inner diameter of the throat section to the inner diameter of the inlet section is 0.05-0.5, and the air inlet The ratio of the diameter to the inner diameter of the throat section is 0.2-0.5;

The ratio of the length of the inlet section to the inner diameter of the inlet section is 1-3, the ratio of the length of the throat section to the inner diameter of the throat section is 1-2.5, and the length of the stable section to the inner diameter of the inlet section The pipe inner diameter ratio is 3-5.

In a specific embodiment of the present invention, the operating temperature of the hydrate separator is 4-15° C., and the operating pressure is 1.1-5.1 MPa. Controlling the above-mentioned operating temperature and operating pressure in the hydrate separator can make the hydrogen in the hydrate slurry and catalytic cracking dry gas be separated as completely as possible, and realize the separation of gas phase and liquid phase.

In a specific embodiment of the present invention, the operating temperature of the hydrate decomposer is 8-23° C., and the operating pressure is 0.1-2.1 MPa. Controlling the above-mentioned operating temperature and pressure in the hydrate decomposer can make the hydrate slurry decompose as completely as possible to obtain hydrogen-depleted gas and hydrate working fluid, and realize the separation of hydrogen-depleted gas and hydrate working fluid.

In a specific embodiment of the present invention, the pressure before the catalytic cracking dry gas to be separated is sucked into the hydration reactor is 0.6-1.6 MPa.

The present invention also provides a system for realizing the separation method of hydrogen in the above-mentioned catalytic cracking dry gas. Pressure valve;

Among them, the hydration reactor cavity has an inlet section, a throat section, and a stabilization section along the flow direction of the hydrate working fluid, and the flow area of the throat section is smaller than that of the inlet section and the stabilization section. The hydration reactor cavity corresponds to the throat section. The side wall of the pipe section is provided with an air inlet;

The hydrate working fluid storage tank is provided with an inlet and an outlet, and the outlet of the hydrate working fluid storage tank communicates with the inlet section of the hydration reactor;

The stable section of the hydration reactor is provided with an outlet for discharging hydrate slurry and hydrogen-rich gas, which communicates with the inlet of the hydrate separator. The top of the hydrate separator is provided with a hydrogen-rich gas discharge port, and the bottom is Equipped with a hydrate slurry outlet;

The hydrate slurry outlet of the hydrate separator communicates with the inlet of the hydrate decomposer, and a heater and/or pressure relief valve is arranged between the two, and the degassed hydrate working fluid of the hydrate decomposer The outlet communicates with the inlet of the hydrate working fluid storage tank.

In the above system, the inner diameter of the inlet section of the hydration reactor is 15-50 mm, the ratio of the inner diameter of the throat section to the inner diameter of the inlet section is 0.05-0.5, and the diameter of the air inlet and the inner diameter of the inlet section are 0.05-0.5. The inner diameter ratio of the throat section is 0.2-0.5;

The ratio of the length of the inlet section to the inner diameter of the inlet section is 1-3, the ratio of the length of the throat section to the inner diameter of the throat section is 1-2.5, and the length of the stable section to the inner diameter of the inlet section The pipe inner diameter ratio is 3-5.

The method for separating hydrogen in catalytic cracking dry gas provided by the present invention adopts a structurally improved hydration reactor, and skillfully changes the flow area in the hydration reactor to provide the required hydration conditions (hydration generation pressure) for catalytic cracking dry gas, namely , after the catalytic cracking dry gas is sucked into the hydration reactor by the pressure drop (even reaching a partial vacuum) generated by the hydrate working fluid flowing through the throat section, and in the process of flowing to the stable section due to the pressure increase and the pressure driving of the two The components such as alkanes and olefins in the catalytic cracking dry gas are fully mixed under the condition of hydration as much as possible, so as to achieve the purpose of separating hydrogen. Compared with the current process for separating catalytic cracking dry gas, the separation method of the present invention does not need to compress and boost the catalytic cracking dry gas to be separated, which not only saves the investment in compression equipment, but also greatly reduces energy consumption. There is no need for an additional stirring mechanism, and the requirements for operating space and operating procedures are significantly reduced, and the separation of hydrogen from catalytic cracking dry gas is realized, which provides the possibility for the industrial application of this technology.

Description of drawings

Fig. 1 is a process flow chart of the present invention for separating hydrogen from catalytic cracking dry gas.

Fig. 2 is the hydration reactor in the hydrogen separation system of catalytic cracking dry gas in the present invention.

Reference signs:

1-Hydrate working fluid storage tank; 2-Hydration reactor; 3-Hydrate separator; 4-Hydrate decomposer; 5-High pressure pump; 6-Cooler; 7-Heater; 8-Decompression valve; 9-hydrate working liquid; 10-catalytic cracking dry gas;

01-inlet section; 02-throat section; 03-expansion section; 04-air inlet.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all Example. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The separation method of hydrogen in catalytic cracking dry gas of the present invention comprises the process of making catalytic cracking dry gas undergo hydration reaction and collecting hydrogen-rich gas, wherein,

The hydration reactor that realizes the hydration reaction is shown in Figure 2, and has the following structure: the cavity of the hydration reactor has an inlet section 01, a throat section 02, and a stabilizing section 03 along the flow direction of the hydrate working fluid, and the flow area of the throat section 02 is equal to Smaller than the flow area of the inlet section 01 and the stable section 03, the hydration reactor cavity is provided with an air inlet 04 corresponding to the side wall of the throat section 02; wherein, the inner diameter of the pipeline of the inlet section 01 of the hydration reactor is 15-50 mm, The ratio of the inner diameter of the throat section 02 to the inner diameter of the inlet section 01 is 0.05-0.5, the ratio of the diameter of the air inlet 04 to the inner diameter of the throat section 02 is 0.2-0.5; the ratio of the length of the inlet section 01 to the inner diameter of the inlet section 01 is 1-3, the ratio of the length of the throat section 02 to the inner diameter of the throat section 02 is 1-2.5, and the ratio of the length of the stabilizing section 03 to the inner diameter of the inlet section 01 is 3-5.

As shown in Figure 1, the separation method of hydrogen in catalytic cracking dry gas of the present invention comprises: after the hydrate working fluid 9 in the hydrate working fluid storage tank 1 passes through the high-pressure pump 5 and the cooler 6, it is sent from the inlet section 01 In the hydration reactor 2, when the hydrate working solution 9 enters the hydration reaction 2, the temperature is 4-15° C., and the pressure is 1.0-5.1 MPa. Make the catalytic cracking dry gas 10 communicate with the hydration reactor 2 through the air inlet 04, the pressure before the catalytic cracking dry gas 10 to be separated is sucked into the hydration reactor 2 is 0.6-1.6 MPa, and the hydrate working fluid flowing through the throat section 02 is used 9. The suction generated by the catalytic cracking dry gas 10 to be separated is drawn into the hydration reactor 2, and the two are mixed in the process of flowing to the stabilization section 03 to undergo a hydration reaction to generate hydrate slurry and hydrogen-rich gas;

The hydrate slurry and hydrogen-rich gas are sent to the hydrate separator 3. The operating temperature of the hydrate separator 3 is 4-15°C and the operating pressure is 1.1-5.1Mpa, and the hydrogen-rich gas is separated and collected.

The hydrogen-rich gas is discharged from the top outlet of the hydrate separator 3 to be collected, and the hydrate slurry is sent to the hydrate decomposer 4 through the bottom outlet of the hydrate separator 3, the heater 7 and the pressure reducing valve 8 for implementation Degassing, the operating temperature of the hydrate decomposer 4 is 8-23°C, and the operating pressure is 0.1-2.1Mpa, and the degassed hydrate working fluid produced by the decomposition is returned to the hydrate working fluid tank 1 for hydration reaction recycling.

In the present invention, the choice of the hydrate working fluid can be selected according to the concentration of each component in the catalytic cracking dry gas, it can be an aqueous solution of tetrabutylammonium bromide or tetrabutylammonium fluoride, or it can be an aqueous solution of tetrabutylammonium fluoride added Other chemical substances that can increase the rate of hydrate formation, the addition of these substances and the level of concentration will not affect the technical solution of the present invention.

Example 1

Hydrate working fluid is tetrabutylammonium bromide (English abbreviation: TBAB), and its concentration is 10wt%;

The composition of catalytic cracking dry gas is shown in Table 1 below:

Table 1 Composition of catalytic cracking dry gas

composition CH ₄ C ₂ H ₆ C ₂ H ₄ C ₃ H ₆ CO ₂ H ₂ Content, mol% 23.79 7.65 21.61 0.24 2.85 44.86

Adopt the technical process of separating hydrogen in catalytic cracking dry gas as shown in Figure 1 and the hydration reactor of Figure 2, please refer to the description of the above-mentioned separation method for its specific process, and the process parameters involved are as follows:

1) The pressure of catalytic cracking dry gas is 1.6MPa.

2) When the hydrate working fluid enters the hydration reactor, the temperature is 8°C and the pressure is 5MPa.

3) The pressure of the hydrate working fluid passing through the throat section of the hydration reactor is 1.2MPa.

4) The fluid formed by the hydrate working liquid and the hydrogen in the catalytic cracking dry gas has a pressure of 4.5 MPa in the stable section of the hydration reactor.

5) The operating temperature of the hydrate separator is 9°C and the operating pressure is 4.3MPa.

6) The operating temperature of the hydrate decomposer is 9°C and the operating pressure is 0.2MPa.

The composition of hydrogen-rich gas and hydrogen-poor gas separated by the process flow in Figure 1 is shown in Table 2 below:

Table 2 Composition of hydrogen-rich gas and hydrogen-depleted gas

composition CH ₄ C ₂ H ₆ C ₂ H ₄ C ₃ H ₆ CO ₂ H ₂ Content of hydrogen-rich gas, mol% 11.25 3.52 5.08 0.27 1.89 77.99 Content of hydrogen-poor gas, mol% 27.38 14.93 41.59 0.10 4.48 11.50

As shown in Table 2, the molar fraction of hydrogen in the hydrogen-rich gas is 77.99%, and the recovery rate of hydrogen reaches 73%. This result shows that the above-mentioned hydration separation method can effectively separate hydrogen from catalytic cracking dry gas.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (9)

1. the separation method of hydrogen in catalytic cracked dry gas, is characterized in that, comprise and make catalytic cracked dry gas generation hydration reaction, and collect the process of hydrogen-rich gas, wherein,

The hydration reactor realizing hydration reaction has following structure: hydration reactor cavity has entrance, trunnion section and stable section along hydrate working fluid flow direction, and the circulation area of trunnion section is all less than the circulation area of entrance and stable section, the sidewall that this hydration reactor cavity corresponds to trunnion section offers inlet mouth;

Described separation method comprises: send into described hydration reactor by hydrate working fluid from entrance, catalytic cracked dry gas is communicated with hydration reactor by inlet mouth, catalytic cracked dry gas to be separated is sucked hydration reactor by the suction utilizing the hydrate working fluid flowing through trunnion section to produce, and make the two flowing to mixed in stable section process, hydration reaction occur, generate hydrate slurry and hydrogen-rich gas;

Described hydrate slurry and hydrogen-rich gas are sent into hydrate separator, is separated and collects hydrogen-rich gas.

2. separation method according to claim 1, it is characterized in that, described hydrogen-rich gas is made to discharge from the top exit of hydrate separator and be collected, described hydrate slurry is sent into hydrate through the outlet at bottom of hydrate separator dissolve device and implement to dissolve, dissolve the hydrate working fluid removing gas that for hydration reaction cycle.

3. separation method according to claim 1, is characterized in that, temperature when making hydrate working fluid enter hydration reactor is 4-15 DEG C, and pressure is 1.0-5.1MPa.

4. the separation method according to claim 1 or 3, it is characterized in that, the internal diameter of the pipeline of the entrance of described hydration reactor is 15-50mm, the internal diameter of described trunnion section and the internal diameter of the pipeline ratio of described entrance are 0.05-0.5, and the diameter of described inlet mouth and the internal diameter ratio of described trunnion section are 0.2-0.5;

The length of described entrance and the internal diameter of the pipeline ratio of described entrance are 1-3, and the internal diameter ratio of described trunnion segment length and described trunnion section is 1-2.5, and the length of described stable section and the internal diameter of the pipeline ratio of described entrance are 3-5.

5. separation method according to claim 1, is characterized in that, the service temperature of described hydrate separator is 4-15 DEG C, and working pressure is 1.1-5.1MPa.

6. separation method according to claim 2, is characterized in that, the service temperature that described hydrate dissolves device is 8-23 DEG C, and working pressure is 0.1-2.1MPa.

7. the separation method according to claim 1 or 3, is characterized in that, it is 0.6-1.6MPa that catalytic cracked dry gas to be separated is inhaled into the pressure before hydration reactor.

8. realize the system of the separation method of hydrogen in the catalytic cracked dry gas described in any one of claim 1-7, it is characterized in that, described system comprises hydrate working fluid storage tank, hydration reactor, hydrate separator, hydrate dissolve device, well heater and/or reducing valve;

Wherein, hydration reactor cavity has entrance, trunnion section and stable section along hydrate working fluid flow direction, and the circulation area of trunnion section is all less than the circulation area of entrance and stable section, the sidewall that this hydration reactor cavity corresponds to trunnion section offers inlet mouth;

Described hydrate working fluid storage tank is provided with entrance and exit, and the outlet of described hydrate working fluid storage tank is communicated with the entrance of described hydration reactor;

Described hydration reactor stable section is provided with the outlet for discharging hydrate slurry and hydrogen-rich gas, and it is communicated with the entrance of described hydrate separator, and the top of described hydrate separator is provided with hydrogen-rich gas discharge outlet, and bottom is provided with hydrate slurry outlet;

The entrance that hydrate slurry outlet and the hydrate of described hydrate separator dissolve device is communicated with, and between the two, being provided with well heater and/or reducing valve, the hydrate working fluid outlet removing gas that described hydrate dissolves device is communicated with the entrance of described hydrate working fluid storage tank.

9. system according to claim 8, it is characterized in that, the internal diameter of the pipeline of the entrance of described hydration reactor is 15-50mm, the internal diameter of described trunnion section and the internal diameter of the pipeline ratio of described entrance are 0.05-0.5, and the diameter of described inlet mouth and the internal diameter ratio of described trunnion section are 0.2-0.5;

The length of described entrance and the internal diameter of the pipeline ratio of described entrance are 1-3, and the internal diameter ratio of described trunnion segment length and described trunnion section is 1-2.5, and the length of described stable section and the internal diameter of the pipeline ratio of described entrance are 3-5.