Sulfuric acid alkylation unit system and method with reduced caustic consumption

Abstract

The present application relates to a kind of alkali consumption reduction sulphur alkylization device system and method, is in the traditional sulphur alkylization process basis, in the front of waste acid cracking furnace, an acid gas buffer tank is set, the acid gas containing a small amount of SO2 in refrigerant tank top, a small amount of SO2 containing gas phase isobutane in reflux tank top, a small amount of acid containing light hydrocarbon volatilized in waste acid storage tank top and gas phase light hydrocarbon removed in top of light hydrocarbon removal column are collected;The waste acid degassing tank is associated with compressor system, and the gas phase light hydrocarbon volatilized in waste acid degassing tank is recovered in the inlet of compressor system first stage.The present application not only handles acid-containing gas, but also saves the natural gas required for cracking waste acid, no longer uses the alkali washing step of traditional process, reduces the energy consumption of device, reduces the alkali consumption and processing loss rate of device, with good economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sulfur alkylation technology, and more particularly to a sulfur alkylation device system and method for reducing caustic consumption. BACKGROUND

[0002] Low carbon olefin alkylation technology is an important technology for producing clean gasoline. Alkylation gasoline produced by the reaction of isobutane and low carbon olefins under the action of a strong acid catalyst (usually sulfuric acid or hydrofluoric acid) has the advantages of high octane number, low volatility, no olefins and aromatics, low sulfur content, and improved anti-knock performance, and is an ideal clean gasoline blending component for vehicles.

[0003] Because sulfuric acid is safer than hydrofluoric acid, most of the newly built alkylation devices in the world use the sulfuric acid method, and currently sulfur alkylation has become the mainstream alkylation technology in modern refineries.

[0004] In the production process of a traditional sulfur alkylation device, the reaction effluent needs to go through acid washing, alkali washing, and water washing processes, which will produce a large amount of waste caustic. After neutralization by sulfuric acid, a large amount of salt-containing wastewater will be produced. With the increasing strictness of environmental protection, wastewater, waste gas, and solid waste produced in the process of petroleum chemical production are not allowed to be directly discharged.

[0005] The waste acid discharged in the alkylation production process needs to go through the processes of waste acid dehydrocarbonization and degassing first. The removed acid-containing gas is washed by an alkali washing tower and then discharged into the gas system (some small production enterprises directly discharge it into the flare system for combustion). CN204768629U discloses a dilute sulfuric acid oil and gas recovery device. By setting a preheating device composed of a preheater and a heat exchanger and a reaction heating kettle, the dilute sulfuric acid is preheated, and a reversible reaction of sulfuric acid ester decomposition into olefins and sulfuric acid occurs in the reaction heating kettle, effectively reducing the content of sulfuric acid ester in the dilute sulfuric acid, increasing the concentration of sulfuric acid from 90% to 93% to 95%, and recycling the sulfuric acid. The dissolved oil and gas in the dilute sulfuric acid is volatilized by decompression and temperature rise for recycling. The recovery device recovers by oil and gas mixed heating reaction, and the process is complex. The dilute sulfuric acid needs to be heated to 50-60℃, which increases the corrosion of the equipment. Some alkylation device compressor systems also discharge SO2-containing light hydrocarbon gas from the top of the refrigerant tank and the reflux tank of the deisobutane column. These acidic gases also need to be washed by an alkali washing tower and then discharged into the gas system. Therefore, caustic is consumed in these processes.

[0006] In the alkylation production process, a small amount of N2-containing acidic and light hydrocarbon gas released from the top of the waste acid storage tank also needs to be washed by an alkali washing tank and then discharged into the atmosphere at a high altitude. With the requirement of the refinery for VOC treatment of the device, this part of the gas also needs to be treated, and caustic is consumed in this process.

[0007] In addition, the light hydrocarbon removed by the light hydrocarbon removal tower of the alkylation device generally enters the gas system. CN105698197A discloses a system utilization and a recycling method for recovering non-condensable gas from a light removal tower. However, the non-condensable gas recovery method has a complex control system.

[0008] The conventional alkylation production process is complex and includes a reaction unit, a reaction effluent coalescing refining unit, a fractionation unit, a refrigeration cycle unit, and a waste acid treatment unit. There are many generation of acid gases in the process: for example, acid gases are generated in the dehydrocarbon and degassing processes of the waste acid discharged after the reaction, a small amount of N2-containing acid gas and light hydrocarbon gas is released from the top of the waste acid storage tank of the waste acid treatment unit, and SO2-containing light hydrocarbon gas is discharged from the top of the refrigerant tank of the refrigeration unit in the compressor system and the reflux tank of the deisobutane column in the fractionation unit. In response to the environmental protection requirements of the refinery on VOC treatment of the device, these gases need to be washed with alkali before being discharged into the atmosphere or the gas system (some small production enterprises directly discharge them into the flare system for combustion). The alkali washing process not only consumes a large amount of alkali, but also generates a large amount of salt-containing wastewater, and the process is complex and not environmentally friendly.

[0009] Technical scheme

[0010] The purpose of the present application is to solve the problems of the existing sulfur alkylation technology, and to provide a sulfur alkylation device system and method based on the existing sulfur alkylation process technology, which can greatly reduce the consumption of alkali.

[0011] In order to achieve the purpose of the present application, the first aspect of the present application provides a sulfur alkylation device system, which comprises a light hydrocarbon removal tower, an alkylation reaction system, a compressor system, a refrigerant tank, an effluent coalescing refining unit, a deisobutane column, a reflux tank, a waste acid dehydrocarbon tank, a waste acid degassing tank, a waste acid storage tank, and a waste acid cracking furnace, characterized in that an acid gas buffer tank is arranged before the waste acid cracking furnace, the refrigerant tank, the reflux tank, the waste acid storage tank, and the light hydrocarbon removal tower are connected with the acid gas buffer tank, and the acid gas containing a small amount of SO2 from the top of the refrigerant tank, the small amount of gaseous isobutane containing SO2 from the top of the reflux tank, the small amount of light hydrocarbon containing acid volatilized from the top of the waste acid storage tank, and the gaseous light hydrocarbon removed from the top of the light hydrocarbon removal tower are collected; the waste acid degassing tank is connected with the compressor system, and the gaseous light hydrocarbon volatilized from the waste acid degassing tank is recovered at the inlet of the first stage of the compressor system.

[0012] To achieve the objectives of this invention, a second aspect of the invention provides a sulfuric acid alkylation method, characterized by employing the apparatus system provided in the first aspect for the alkylation reaction, comprising: alkylation feedstock entering a light hydrocarbon removal tower; gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower entering an acidic gas buffer tank; material from the bottom outlet of the light hydrocarbon removal tower entering an alkylation reaction system; sulfuric acid catalyst reacting with the alkylation feedstock at low temperature; the reaction gas phase, mainly composed of vaporized light hydrocarbons, entering a compressor system and then a refrigerant tank; a small amount of acidic gas from the top of the refrigerant tank entering the acidic gas buffer tank; and the remaining material, as a refrigerant for the reaction system, mixing with the alkylation feedstock and continuing into the reaction cycle; the reaction effluent entering an effluent coalescence purification system to remove sulfuric acid and sulfate esters, and then entering an isobutane removal tower; a reflux tank being provided at the top of the isobutane removal tower; and the reflux... Part of the isobutane liquid in the tank is refluxed back to the isobutane removal tower, and a small amount of SO2-containing gaseous isobutane enters the acidic gas buffer tank. The waste acid discharged from the alkylation reaction system enters the waste acid dehydrocarbonization tank to remove free hydrocarbons and is depressurized to about 0.05 MPa before entering the waste acid degassing tank. The gaseous light hydrocarbons in the waste acid degassing tank enter the first inlet of the compressor system. The acid phase at the bottom of the waste acid degassing tank enters the waste acid storage tank. A small amount of acid-containing light hydrocarbons in the waste acid storage tank enters the acidic gas buffer tank. The waste acid in the waste acid storage tank and the gaseous product collected in the acidic gas buffer tank are both sent to the waste acid pyrolysis furnace. In the waste acid pyrolysis furnace, sulfuric acid is decomposed into SO2 at an environment of 1000-1300℃, and organic matter is oxidized into CO2. The gaseous light hydrocarbons volatilized from the waste acid degassing tank are introduced into the first inlet of the compressor system for recovery.

[0013] The sulfuric acid alkylation apparatus system and method provided by the present invention have the following advantages:

[0014] 1. Significantly reduces alkali consumption in the alkylation unit; under normal production conditions, alkali consumption is almost nonexistent. Acidic gases are incinerated in the waste acid cracking furnace, which not only treats the acidic gases but also saves the natural gas required for cracking waste acid, reducing the energy consumption of the waste acid cracking unit and resulting in good economic benefits.

[0015] 2. The light hydrocarbons volatilized from the waste acid degassing tank do not need to be fed into the alkali washing tower. Instead, they are recovered at the inlet of the first stage of the compressor system. The inlet pressure of the first stage of the compressor system is about 0.01MPa. This method is more thorough than the existing technology for recovering light hydrocarbons. It not only reduces the consumption of alkali in the unit, but also reduces the processing loss rate of the unit.

[0016] 3. The sulfuric acid alkylation device system provided by the present invention has a wide range of applications, requires less modification to the original alkaline washing process, reduces equipment investment, and is simple to operate. Attached Figure Description

[0017] Figure 1 This is a flowchart of existing technology.

[0018] Figure 2 This is a flowchart comparing the device system of the present invention with existing technologies.

[0019] Figure 3 A flowchart of the device system provided by the present invention. Detailed Implementation

[0020] The technical solutions in 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.

[0021] Figure 1 This is a flowchart of an existing sulfuric acid alkylation system.

[0022] The sulfuric acid alkylation system includes an alkylation reaction unit, a reaction effluent coalescence and purification unit, a fractionation unit, a refrigeration cycle unit, and the aforementioned waste acid treatment unit. The waste acid treatment unit includes sections for waste acid storage, dehydrocarbonization, degassing, buffering, pyrolysis, and alkaline washing. The equipment used includes a light hydrocarbon removal tower, an alkylation reaction system, a compressor system, a refrigerant tank, an effluent coalescence and purification unit, an isobutane removal tower, a reflux tank, a waste acid light hydrocarbon removal tank, a waste acid degassing tank, an alkaline washing tower, an alkaline washing tank, a waste acid storage tank, and a waste acid pyrolysis furnace. These treatment units and equipment are well known in the art.

[0023] like Figure 1 As shown, in the prior art, the inlet end of the light hydrocarbon removal tower is connected to the alkylation feed gas pipeline, the material from the outlet of the bottom pipeline of the light hydrocarbon removal tower enters the alkylation reaction system, and the gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower enter the gas system; in the alkylation reaction system, the alkylation feed gas reacts with the sulfuric acid catalyst at -3 to 10°C, and the reaction effluent enters the effluent coalescence purification system to remove the small amount of sulfuric acid and sulfuric acid esters carried in the hydrocarbon phase; the vaporized light hydrocarbons in the alkylation reaction system enter the compressor system, and the discharged waste acid enters the waste acid dehydrocarbonization tank.

[0024] The material from the compressor system outlet enters the refrigerant tank, and the refrigerant in the refrigerant tank is returned to the raw material pipeline of the alkylation reaction system to cool the alkylation raw material. A small amount of acidic gas containing SO2 at the top of the refrigerant tank enters the alkaline scrubbing tower.

[0025] The effluent from the effluent coalescence purification system enters the isobutane removal tower. The gas phase from the isobutane removal tower enters the reflux tank, and some of the isobutane liquid is returned to the isobutane removal tower for reflux. A small amount of SO2-containing gaseous isobutane from the top of the reflux tank is discharged into the alkaline washing tower.

[0026] The waste acid, after being depressurized to approximately 0.05 MPa in the waste acid dehydrocarbonization tank, enters the waste acid degassing tank. The removed gaseous light hydrocarbons are then washed in an alkaline scrubbing tower before being discharged into the gas system. The acid phase at the bottom of the waste acid degassing tank enters the waste acid storage tank, while the small amount of acid-containing light hydrocarbons volatilized from the top of the waste acid storage tank are washed in an alkaline scrubbing tank before being discharged into the atmosphere at high altitude.

[0027] The waste acid in the waste acid storage tank enters the waste acid pyrolysis furnace, where it is heated to a high temperature of 1000–1300°C under the combustion of fuel gas for pyrolysis. At this temperature, sulfuric acid is decomposed into SO2, and all organic matter is decomposed and oxidized into CO2. The heat required for the high-temperature pyrolysis of the waste acid is provided by the heat released from the combustion of fuel gas. After purification, SO2 to SO3 conversion, and dilute acid absorption, the pyrolysis gas is regenerated into 98.0%–99.2% concentrated sulfuric acid, which is then returned to the alkylation reaction system for reuse.

[0028] The principle of waste acid pyrolysis reaction is as follows:

[0029] H₂SO₄ → SO₂ + H₂O + 1 / 2O₂

[0030] CxHy+(X+Y / 4)O2→XCO2+Y / 2H2O

[0031] Figure 2 This is a flowchart comparing the device system of the present invention with the prior art.

[0032] Figure 3 This is a flowchart of the device system of the present invention.

[0033] from Figure 2 The process comparison diagram shows the process changes in this invention compared to the prior art, where the alkaline washing tower and alkaline washing tank that consume alkaline solution are replaced. These changes include the addition of new processing units and changes in pipeline direction and function.

[0034] This invention provides a sulfuric acid alkylation apparatus system, comprising a light hydrocarbon removal tower, an alkylation reaction system, a compressor system, a refrigerant tank, an effluent coalescence purification system, an isobutane removal tower, a reflux tank, a waste acid dehydrocarbonization tank, a waste acid degassing tank, a waste acid storage tank, and a waste acid pyrolysis furnace. The system is characterized by an acidic gas buffer tank installed before the waste acid pyrolysis furnace. The refrigerant tank, reflux tank, waste acid storage tank, and light hydrocarbon removal tower are connected to the acidic gas buffer tank, collecting acidic gas containing a small amount of SO2 from the top of the refrigerant tank, a small amount of SO2-containing gaseous isobutane from the top of the reflux tank, a small amount of acidic light hydrocarbons volatilized from the top of the waste acid storage tank, and gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower. The waste acid degassing tank is connected to the compressor system, and gaseous light hydrocarbons volatilized from the waste acid degassing tank are recovered at a section inlet of the compressor system.

[0035] Compared to Figure 1The present invention adds an acidic gas buffer tank before the waste acid pyrolysis furnace, in contrast to the existing technology. This buffer tank collects the acidic gas containing a small amount of SO2 from the top of the refrigerant tank of the original alkaline scrubbing tower, the small amount of SO2-containing gaseous isobutane from the top of the isobutane removal tower reflux tank, the small amount of acidic light hydrocarbons volatilized from the top of the waste acid storage tank, and the gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower. These gases are then incinerated in the waste acid pyrolysis furnace. More importantly, the gaseous light hydrocarbons volatilized from the waste acid degassing tank do not enter the alkaline scrubbing tower but are instead recovered through the first inlet of the compressor. The first inlet pressure of the compressor system is approximately 0.01 MPa, resulting in more thorough recovery of light hydrocarbons than existing technologies. This not only reduces alkali consumption but also reduces the processing loss rate of the unit. Using the technical solution of this invention, the alkali consumption of the alkylation unit is significantly reduced (almost no alkali consumption is observed under normal production conditions).

[0036] This invention also provides a sulfuric acid alkylation method, characterized by using the apparatus system provided in the first aspect for the alkylation reaction. The specific implementation process includes: the alkylation feedstock enters a light hydrocarbon removal tower; the gaseous light hydrocarbons removed at the top of the light hydrocarbon removal tower enter an acidic gas buffer tank; the material exiting the bottom of the light hydrocarbon removal tower enters the alkylation reaction system; the sulfuric acid catalyst reacts with the alkylation feedstock at low temperature; the reaction gas phase, mainly composed of vaporized light hydrocarbons, enters a compressor system and then a refrigerant tank; a small amount of acidic gas at the top of the refrigerant tank enters the acidic gas buffer tank; the remaining material, as a refrigerant for the reaction system, mixes with the alkylation feedstock and continues into the reaction cycle; the reaction effluent enters an effluent coalescence purification system to remove sulfuric acid and sulfate esters, and then enters an isobutane removal tower, the top of which is equipped with... A reflux tank is placed in which a portion of the isobutane liquid is refluxed back to the isobutane removal tower, and a small amount of SO2-containing gaseous isobutane enters the acidic gas buffer tank. The waste acid discharged from the alkylation reaction system enters the waste acid dehydrocarbonization tank to remove free hydrocarbons and is depressurized to about 0.05 MPa before entering the waste acid degassing tank. The gaseous light hydrocarbons in the waste acid degassing tank enter the first inlet of the compressor system, and the acid phase at the bottom of the waste acid degassing tank enters the waste acid storage tank. A small amount of acid-containing light hydrocarbons in the waste acid storage tank enters the acidic gas buffer tank. The waste acid in the waste acid storage tank and the gaseous product collected in the acidic gas buffer tank are both sent to the waste acid pyrolysis furnace. In the waste acid pyrolysis furnace, sulfuric acid is decomposed into SO2 at an environment of 1000-1300℃, and organic matter is oxidized into CO2.

[0037] We can... Figure 2The process flow comparison diagram illustrates why this invention reduces alkali consumption. The method provided by this invention, by adding an acidic gas buffer tank to collect the gaseous components that need to be alkaline washed or discharged into the gas system, can effectively reduce alkaline washing operations (eliminating the corresponding alkaline washing tower and tank), thereby simplifying the process and reducing alkali consumption, significantly reducing the discharge of neutralized wastewater. Furthermore, the gaseous components that were originally discharged into the gas system enter the pyrolysis furnace to provide energy for the combustion and pyrolysis of waste acid, which can effectively reduce fuel gas consumption.

[0038] The sulfuric acid alkylation apparatus system and method provided by this invention are preferably applied to the processing of isoalkanes and olefins under strong acid catalysis to produce fractions with octane numbers higher than the feedstock and boiling ranges in the gasoline range. The sulfuric acid alkylation involved in this invention is generally a reaction of isobutane with C3-C5 olefin fractions, and is particularly suitable for the reaction of isobutane with C4 olefins.

Claims

1. A sulfuric acid alkylation unit system, comprising a light hydrocarbon removal tower, an alkylation reaction system, a compressor system, a refrigerant tank, an effluent coalescence purification system, an isobutane removal tower, a reflux tank, a waste acid dehydrocarbonization tank, a waste acid degassing tank, a waste acid storage tank, and a waste acid cracking furnace, characterized in that... An acidic gas buffer tank is installed in front of the waste acid cracking furnace. The refrigerant tank, reflux tank, waste acid storage tank, and light hydrocarbon removal tower are connected to the acidic gas buffer tank. The acidic gas buffer tank collects acidic gas containing a small amount of SO2 from the top of the refrigerant tank, a small amount of SO2-containing gaseous isobutane from the top of the reflux tank, a small amount of acidic light hydrocarbons volatilized from the top of the waste acid storage tank, and gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower. The waste acid degassing tank is connected to the compressor system, and gaseous light hydrocarbons volatilized from the waste acid degassing tank are recovered at a section inlet of the compressor system.

2. The apparatus system according to claim 1, characterized in that, The system does not have an alkaline scrubbing tower after the waste acid degassing tank, nor an alkaline scrubbing tank after the waste acid storage tank.

3. A method for alkylating sulfuric acid, characterized in that, The alkylation reaction using the apparatus system described in claim 1 includes: alkylation feedstock entering a light hydrocarbon removal tower; gaseous light hydrocarbons removed from the top of the light hydrocarbon removal tower entering an acidic gas buffer tank; and the material exiting the bottom of the light hydrocarbon removal tower entering the alkylation reaction system. A sulfuric acid catalyst reacts with the alkylation feedstock at low temperature, with the reaction gas phase, mainly composed of vaporized light hydrocarbons, entering a compressor system and then a refrigerant tank. A small amount of acidic gas from the top of the refrigerant tank enters the acidic gas buffer tank, and the remaining material is used as a refrigerant in the reaction system, mixed with the alkylation feedstock, and continues in the reaction cycle. The reaction effluent enters an effluent coalescence purification system to remove sulfuric acid and sulfate esters, and then enters an isobutane removal tower. A reflux tank is installed at the top of the isobutane removal tower, in which a portion of the isobutane liquid is refluxed back to the isobutane removal tower, and a small amount of SO2-containing gaseous isobutane enters the acidic gas buffer tank. The waste acid discharged from the alkylation reaction system enters a waste acid dehydrocarbonization tank to remove free hydrocarbons and reduce the pressure to 0.05%. The waste acid enters the degassing tank at approximately MPa. The gaseous light hydrocarbons volatilized from the waste acid degassing tank are introduced into the first inlet of the compressor system for recovery. The acid phase at the bottom of the waste acid degassing tank enters the waste acid storage tank. A small amount of acid-containing light hydrocarbons from the waste acid storage tank enters the acidic gas buffer tank. The waste acid in the waste acid storage tank and the gaseous products collected in the acidic gas buffer tank are both sent to the waste acid pyrolysis furnace. In the waste acid pyrolysis furnace, sulfuric acid is decomposed into SO2, and organic matter is oxidized into CO2.

4. The method according to claim 3, characterized in that, The sulfuric acid catalyst reacts with the alkylation feedstock at -3 to 10°C.

5. The method according to claim 3, characterized in that, In the waste acid pyrolysis furnace, the pyrolysis temperature is between 1000 and 1300°C.

6. The method according to claim 3, characterized in that, The inlet pressure of the compressor system is 0.01 MPa.

7. The method according to claim 3, characterized in that, The sulfuric acid alkylation is a reaction between isobutane and C3-C5 olefin fractions.

8. The method according to claim 3, characterized in that, The sulfuric acid alkylation is a reaction between isobutane and a C4 olefin.

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