Method for on-line treatment of crystal substances in liquefied gas desulfurization alcohol alkali liquor regeneration system

Abstract

The invention relates to a method for treating crystal substances in a liquefied gas desulfurization alcohol-alkali liquor regeneration system on line. The method comprises the following steps: mounting and electrically controlling a valve; a controller is arranged; collecting inlet and outlet pressure of the regenerated alkali liquor filter by using a pressure sensor, and collecting liquefied gas inlet pressure and liquefied gas outlet pressure of the supergravity reactor; and if overpressure is found, opening the electric control valve to inject the high-temperature demineralized water in the demineralized water pipe network into the alkali liquor conveying pipeline. The method has the advantages that the concentration of the alkali liquor can be reduced by injecting high-temperature demineralized water into the inlet of the spent alkali liquor pump under the condition that equipment is not opened, crystals are melted through the low-concentration alkali liquor, and the purposes of cleaning or melting the crystals and recovering the optimal operation state of the equipment can be achieved in a short time. The process is simple and convenient to operate and has no risk of medium channeling. The device is simple in structure, time-saving, labor-saving and maintenance cost-saving, the effect is obvious, high-temperature demineralized water can be injected in time when it is found that operation parameters just deviate during daily operation, and therefore differential pressure deviation can be eliminated in the bud.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and particularly relates to a method for online processing of crystals in a liquefied gas desulfurization alkali solution regeneration system. Background Art

[0002] In the field of petrochemicals, liquefied gas refining generally uses the "amine washing method" to remove hydrogen sulfide and the "alkaline washing method" to remove mercaptans. The former is generally more mature, and the "alkaline washing method" to remove mercaptans is the key to achieving deep desulfurization of liquefied gas. The mercaptans in the liquefied gas react with sodium hydroxide in the liquefied gas extraction tower to generate sodium mercaptides, thereby removing low molecular weight mercaptans in the liquefied gas. Then the sodium mercaptides react with oxygen in the air in the oxidation tower to generate sodium hydroxide and disulfides. The alkali solution is regenerated, and the disulfides are separated by gravity sedimentation in the disulfide separator. The commonly used liquefied gas desulfurization technology is fiber membrane technology. The fiber membrane contactor replaces the liquefied gas extraction tower to improve the mercaptan removal efficiency. The alkali solution regeneration process uses solvent oil back extraction instead of disulfide gravity sedimentation separation. The disadvantage of this technology is that it cannot avoid the large-scale discharge of alkali slag while achieving deep desulfurization of liquefied gas. In response to the above problems, China has developed a complete set of liquefied gas deep desulfurization technology (LDS), which applies ultra-gravity technology to the liquefied gas deep desulfurization alkali solution regeneration process, takes advantage of the ultra-gravity field to enhance gas-liquid mass transfer at the microscale, and uses a rotating packed bed instead of a traditional oxidation tower, which greatly improves the conversion rate of the sodium thiolate oxidation reaction and the separation rate of disulfides, and realizes the efficient regeneration of the circulating alkali solution. Figure 1 The following is a schematic diagram of a prior art liquefied gas desulfurization alkali solution regeneration system. Figure 1As shown, the alkali liquor to be produced by the liquefied gas sweetening unit enters the alkali liquor flash tank 1 by self-pressure, a small amount of light hydrocarbons entrained in the alkali liquor to be produced by flashing enters the flare system, the alkali liquor to be produced flowing out of the alkali liquor flash tank 1 is pressurized by the alkali liquor pump 2 and enters the alkali liquor heater 3, after heat exchange with the heat medium water and heating to 50°C, it is filtered by the alkali liquor filter 4 and flows into the supergravity reactor 5 from the liquefied gas inlet, and contacts with the oxidizing wind from the blower in countercurrent, under the action of the sulfonated cobalt phthalocyanine catalyst, the sodium mercaptide in the alkali liquor to be produced reacts with oxygen to form disulfide, and quickly volatilizes into gas and is discharged to the combustion furnace with the tail gas. The regenerated alkali liquid in the supergravity reactor 5 flows into the alkali liquid buffer tank 6 through the liquefied gas outlet, and then the regenerated alkali liquid is transported in two ways through the alkali liquid circulation pump 7, one part of which enters the alkali liquid heater 3 together with the alkali liquid to be produced provided by the alkali liquid pump 2, and then returns to the supergravity reactor 5; the other part goes to the packing column 8 at the top of the alkali liquid buffer tank 6 for deoxygenation, and nitrogen is introduced at the bottom of the packing column 8 to remove the dissolved oxygen in the regenerated alkali liquid. The deoxygenated regenerated alkali liquid in the alkali liquid buffer tank 6 is transported by the regeneration alkali liquid pump 9, cooled to 40°C by the regeneration alkali liquid cooler, and then filtered by the regeneration alkali liquid filter 10 and sent to the desulfurization unit mercaptan extraction reactor. Its working principle is as follows: the alkali liquid to be produced from the alkali liquid flash tank 1 is heated by the alkali liquid pump 2 together with the regenerated alkali liquid through the alkali liquid heater 3 and then injected into the alkali liquid filter 4, the impurities therein are filtered out by the circulating alkali liquid filter 4, and then flows into the supergravity reactor 5. In the supergravity reactor 5, the sodium thiolate in the alkali liquid reacts with the oxidizing air from the blower under the action of the catalyst to generate alkali liquid and disulfide. The disulfide is simultaneously stripped into the oxidizing air and then washed in the washing tower and incinerated in the boiler, so that the alkali liquid is regenerated; in the supergravity reactor 5, the carbon dioxide in the alkali liquid and the oxidizing air will generate non-regenerated sodium carbonate. However, the above-mentioned liquefied gas sweetening alcohol alkali liquor regeneration system has the following problems during daily operation: the sodium carbonate in the alkali liquor will form crystals as the alkali liquor concentration increases. When a large amount of crystals gather, the regeneration alkali liquor filter 4 and the supergravity reactor 5 will be blocked, causing the key process parameters such as the alkali liquor circulation volume, the differential pressure of the regeneration alkali liquor filter 4, and the increase in the differential pressure of the liquefied gas inlet and outlet of the supergravity reactor 5 to continue to deviate. In addition, the crystals in the supergravity reactor 5 will cause its vibration to increase, and in severe cases, the seal of the supergravity reactor 5 will be damaged. Therefore, when the crystals accumulate to a certain extent, they need to be processed, otherwise it will affect the normal operation of the liquefied gas sweetening alcohol alkali liquor regeneration system.

[0003] In the past, the method for treating crystals in the regeneration alkali solution filter 4 was to switch to a spare regeneration alkali solution filter and open the regeneration alkali solution filter 4 where crystals appeared for cleaning. However, there are the following risks in the treatment process: ① When the regeneration alkali solution filter 4 where crystals appeared is isolated during the process and the blind plate needs to be disassembled after the treatment is completed, if the upstream and downstream valves of the regeneration alkali solution filter 4 are not closed tightly, there is a risk of alkali solution injuring people. ② Before the blocked regeneration alkali solution filter 4 is disassembled to treat the crystals, the residual alkali solution inside it needs to be emptied. This process requires a temporary pipeline to be connected at the venting point of the regeneration alkali solution filter 4 to lead to the alkaline sewage floor drain. The discharge of alkali solution with a concentration of up to 12% will increase the load on subsequent sewage treatment, and the on-site discharge does not meet the environmental protection emission requirements.

[0004] One method of treating the supergravity reactor 5 is to inject deionized water into the middle and upper part of the supergravity reactor 5 to melt the crystals. Due to the position limitation of the injection point, the crystals on the top of the supergravity reactor 5 cannot be washed, so the problem of high differential pressure of the supergravity reactor 5 is still not well solved. Another treatment method is to open the supergravity reactor 5 to clean the crystals, but during the shutdown of the supergravity reactor 5, the alkali liquid inside the liquefied gas sweetening alcohol alkali liquid regeneration system cannot be effectively regenerated, the alkali liquid desulfurization effect will decrease, and a large amount of alkali residue will be discharged in the later stage. Summary of the invention

[0005] In order to solve the above problems, the object of the present invention is to provide a method for online treatment of crystals in a liquefied gas sweetening system.

[0006] In order to achieve the above object, the method for online treatment of crystals in a liquefied gas sweetening alcohol alkali solution regeneration system provided by the present invention comprises the following steps performed in sequence:

[0007] 1) Install a pressure sensor at the inlet and outlet of the regeneration alkali solution filter, and the oxidation air inlet and oxidation air outlet of the supergravity reactor respectively;

[0008] 2) Connect a desalted water delivery pipeline to the desalted water network on the alkali solution delivery pipeline at the inlet of the regeneration alkali solution pump, and install an electric control valve on the desalted water delivery pipeline;

[0009] 3) Electrically connecting the controller to the pressure sensor and the electronically controlled valve respectively;

[0010] 4) During the operation of the liquefied gas sweetening alkali solution regeneration system, under the control of the controller, the pressure sensors at the inlet and outlet of the regeneration alkali solution filter are used to respectively collect the inlet and outlet pressures of the regeneration alkali solution filter in real time, and the pressure sensors at the oxidation air inlet and oxidation air outlet of the supergravity reactor are used to respectively collect the oxidation air inlet pressure and oxidation air outlet pressure of the supergravity reactor in real time, and then transmit them to the controller;

[0011] 5) Once the controller detects that the pressure difference between the inlet and outlet of the regenerated alkali solution filter exceeds 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor exceeds 5KPa, the electronically controlled valve is immediately opened to inject the high-temperature desalted water in the desalted water network into the alkali solution delivery pipeline;

[0012] 6) The high-temperature desalted water will be mixed with the regenerated alkali solution in the alkali solution conveying pipeline to reduce the concentration of the regenerated alkali solution at the outlet of the regenerated alkali solution pump 2. When the low-concentration regenerated alkali solution flows through the regenerated alkali solution filter 4, the crystals in the regenerated alkali solution filter are gradually melted under the flushing of the low-concentration alkali solution; then the low-concentration regenerated alkali solution enters the interior of the supergravity reactor from the liquid inlet at the top of the supergravity reactor, and the crystals in the entire supergravity reactor are also gradually melted under the flushing of the low-concentration regenerated alkali solution. Then the low-concentration regenerated alkali solution with crystals flows into the alkali solution buffer tank through the liquid outlet of the supergravity reactor for recycling, until the pressure difference between the inlet and outlet of the regenerated alkali solution filter is lower than 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor is lower than 5KPa, and the electric control valve is closed to stop injecting the high-temperature desalted water.

[0013] The controller adopts a computer.

[0014] The method for online treatment of crystals in a liquefied gas sweetening system provided by the present invention has the following beneficial effects: the concentration of the alkali solution can be reduced by injecting high-temperature desalted water at the inlet of the alkali solution pump to be produced without opening the equipment, and the crystals can be melted by using low-concentration alkali solution, so that the purpose of cleaning or melting the crystals and restoring the equipment to the optimal operating state can be achieved in a short time. The process is simple, the operation is convenient, and there is no risk of medium crosstalk. It takes at least four days to open the ultra-gravity reactor to treat the interior, but this method only takes one to two hours, so it saves time, labor and maintenance costs, and the effect is obvious. In daily operation, high-temperature desalted water can be injected in time when the operating parameters are just deviated, so the differential pressure deviation can be eliminated in the bud. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a schematic diagram of the structure of a liquefied gas desulfurization alkali solution regeneration system in the prior art. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The same components as those in the prior art are given the same reference numerals, and detailed descriptions thereof are omitted.

[0017] The method for online treatment of crystals in a liquefied gas sweetening alcohol alkali solution regeneration system provided by the present invention comprises the following steps performed in sequence:

[0018] 1) A pressure sensor is installed at the inlet and outlet of the regeneration alkali solution filter 4, and the oxidation air inlet and oxidation air outlet of the supergravity reactor 5 respectively;

[0019] 2) Connecting a desalted water delivery pipeline to the desalted water network on the alkali solution delivery pipeline at the inlet of the regeneration alkali solution pump 2, and installing an electric control valve on the desalted water delivery pipeline;

[0020] 3) The controller is electrically connected to the pressure sensor and the electric control valve respectively; the controller is a computer.

[0021] 4) During the operation of the liquefied gas sweetening alkali solution regeneration system, under the control of the controller, the pressure sensors at the inlet and outlet of the regeneration alkali solution filter 4 are used to respectively collect the inlet and outlet pressures of the regeneration alkali solution filter 4 in real time, and the pressure sensors at the oxidation air inlet and oxidation air outlet of the supergravity reactor 5 are used to respectively collect the oxidation air inlet pressure and oxidation air outlet pressure of the supergravity reactor 5 in real time, and then transmit them to the controller;

[0022] 5) Once the controller detects that the pressure difference between the inlet and outlet of the regenerated alkali solution filter 4 exceeds 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor 5 exceeds 5KPa, the electronically controlled valve is immediately opened to inject the high-temperature deionized water in the deionized water network into the alkali solution delivery pipeline;

[0023] 6) The high-temperature desalted water will be mixed with the regenerated alkali solution in the alkali solution conveying pipeline, so that the concentration of the regenerated alkali solution at the outlet of the regenerated alkali solution pump 2 is reduced. When the low-concentration regenerated alkali solution flows through the regenerated alkali solution filter 4, the crystals in the regenerated alkali solution filter 4 are gradually melted under the flushing of the low-concentration alkali solution; then the low-concentration regenerated alkali solution enters the interior of the supergravity reactor 5 from the liquid inlet at the top of the supergravity reactor 5, and the crystals in the entire supergravity reactor 5 are also gradually melted under the flushing of the low-concentration regenerated alkali solution. Then the low-concentration regenerated alkali solution with crystals flows into the alkali solution buffer tank 6 through the liquid outlet of the supergravity reactor 5 for recycling, until the pressure difference between the inlet and outlet of the regenerated alkali solution filter 4 is lower than 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor 5 is lower than 5KPa, and the electric control valve is closed to stop injecting the high-temperature desalted water.

Claims

1. A method for online treatment of crystals in a liquefied gas sweetening alkali solution regeneration system, characterized in that: The method comprises the following steps performed in sequence: 1) installing a pressure sensor at the inlet and outlet of the regeneration alkali solution filter (4) and the oxidation air inlet and oxidation air outlet of the supergravity reactor (5); 2) connecting a desalted water delivery pipeline to the desalted water network on the alkali solution delivery pipeline at the inlet of the regeneration alkali solution pump (2), and installing an electric control valve on the desalted water delivery pipeline; 3) Electrically connecting the controller to the pressure sensor and the electronically controlled valve respectively; 4) During the operation of the liquefied gas desulfurization alkali solution regeneration system, under the control of the controller, the pressure sensors at the inlet and outlet of the regeneration alkali solution filter (4) are used to respectively collect the inlet and outlet pressures of the regeneration alkali solution filter (4) in real time, and the pressure sensors at the oxidation air inlet and oxidation air outlet of the supergravity reactor (5) are used to respectively collect the oxidation air inlet pressure and oxidation air outlet pressure of the supergravity reactor (5) in real time, and then transmit them to the controller; 5) Once the controller detects that the pressure difference between the inlet and outlet of the regenerated alkali solution filter (4) exceeds 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor (5) exceeds 5KPa, the electronically controlled valve is immediately opened to inject the high-temperature deionized water in the deionized water network into the alkali solution delivery pipeline; 6) The high-temperature desalted water is mixed with the regeneration alkali solution in the alkali solution delivery pipeline, so that the concentration of the regeneration alkali solution at the outlet of the regeneration alkali solution pump (2) is reduced. When the low-concentration regeneration alkali solution flows through the regeneration alkali solution filter (4), the crystals in the regeneration alkali solution filter (4) are gradually melted under the flushing of the low-concentration alkali solution; then the low-concentration regeneration alkali solution enters the interior of the supergravity reactor (5) from the liquid inlet at the top of the supergravity reactor (5), and the crystals in the entire supergravity reactor (5) are also gradually melted under the flushing of the low-concentration regeneration alkali solution. Then the low-concentration regeneration alkali solution with crystals flows into the alkali solution buffer tank (6) through the liquid outlet of the supergravity reactor (5) for recycling, until the pressure difference between the inlet and outlet of the regeneration alkali solution filter (4) is lower than 50KPa, or the pressure difference between the oxidation air inlet and the oxidation air outlet of the supergravity reactor (5) is lower than 5KPa, and the electric control valve is closed to stop injecting the high-temperature desalted water.

2. The method for online treatment of crystals in a liquefied gas sweetening alkali solution regeneration system according to claim 1, characterized in that: The controller adopts a computer.

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