A method and system for reducing ethylene hydrogenation loss

Abstract

The present application provides a system for reducing ethylene loss in an ethylene production process from cracking gas, and a method for reducing ethylene loss in an ethylene production process from cracking gas. The system comprises, in sequence along a feed direction: a dryer for drying cracking gas; a first heat exchanger; a first hydrogenation reactor; a second heat exchanger; a second hydrogenation reactor; a third heat exchanger; a third hydrogenation reactor; and a fourth heat exchanger; and a controller for controlling the flow rate of a fluid for heat exchange of the first heat exchanger so as to control the temperature of the material entering the inlet end of the first hydrogenation reactor, thereby further controlling the temperature rise range between the outlet end of the first hydrogenation reactor and the inlet end of the first hydrogenation reactor by affecting the reaction degree of the hydrogenation reaction to be between T 升 -1 and T 升 .

Description

Technical Field

[0001] This invention relates to the field of ethylene production by cracking, and more specifically, to a method for reducing ethylene hydrogenation loss during the ethylene production by cracking process. Background Technology

[0002] Currently, most ethylene plants employ a pre-hydrogenation scheme, where the feed to the C2 hydrogenation reactor is preheated using LS in the feed preheater. The reactor feed temperature is controlled in stages: by controlling the flow rate of the reactor feed preheater and its bypass flow rate, the inlet temperature of the reactor can be controlled according to its operating cycle and the catalyst activity under ideal conditions. Hydrogenation is exothermic; therefore, the cracked gas from the first-stage reactor is cooled by heat exchange with circulating water in the first-stage intercooler of the hydrogenation reactor before entering the second-stage reactor. The cracked gas from the second-stage reactor is cooled by heat exchange with circulating water in the second-stage intercooler of the hydrogenation reactor before entering the third-stage reactor. The cracked gas from the third-stage reactor is cooled by heat exchange with circulating water in the C2 hydrogenation aftercooler. The inlet temperature conditions of the reactor must be carefully controlled to ensure complete conversion of acetylene while preventing excessive bed temperature leading to ethylene loss (over-hydrogenation).

[0003] Because the adsorption capacity on palladium-based catalysts is:

[0004] H2S > C2H2 > CO > Butadiene > MAPD > Ethylene / propylene > Carbon dioxide

[0005] The energy released by the hydrogenation of acetylene is:

[0006] C2H2 + H2 → C2H4 - 175.7 KJ / mol

[0007] C2H4 + H2 → C2H6 - 138.1 KJ / mol

[0008] Wanhua Chemical's ethylene plant is designed to produce 1 million tons of ethylene per year, with 8,000 operating hours annually. It employs high- and low-pressure propane removal and acetylene staged hydrogenation technology. The C2 hydrogenation system is located at the outlet of the fifth stage of the cracked gas compressor. The overhead gas phase from the high-pressure propane removal tower is compressed in the fifth stage of the cracked gas compressor, cooled by cooling water, and subjected to arsenic removal in the arsenic removal bed before entering the C2 hydrogenation feed heater. It is then heated with low-pressure steam before entering the reactor. The feed temperature is regulated by controlling the heating flow rate and bypass. The inlet temperature is adjusted based on the reactor's operating time and catalyst activity to ensure optimal reaction temperature. The hydrogenation reaction is adiabatic. The hydrogenation system consists of three reactors connected in series, with the reactants cooled by an intercooler and a post-cooler for the third reactor.

[0009] By adjusting the reactor feed temperature, the conversion rate and selectivity of acetylene can be controlled to avoid ethylene product loss under superhydrogenation conditions. No backup reactor is required. If unplanned regeneration of the first-stage reactor bed is needed, the second-stage reactor bed can meet the requirements and produce qualified ethylene without reducing the unit load, but some hydrogenation selectivity will be lost. Summary of the Invention

[0010] The present invention aims to provide a method and system for reducing ethylene loss in the process of producing ethylene from cracked gas, thereby reducing ethylene loss during the hydrogenation of cracked gas and improving economic efficiency.

[0011] According to a first aspect of the present invention, a system for reducing ethylene loss in a process for producing ethylene from cracked gas is provided, comprising: sequentially connected along the feed direction:

[0012] Dryer, used to dry pyrolysis gas;

[0013] The first heat exchanger is used to regulate the temperature of the material entering the first hydrogenation reactor;

[0014] First hydrogenation reactor;

[0015] The second heat exchanger is used to regulate the temperature of the material entering the second hydrogenation reactor;

[0016] Second hydrogenation reactor;

[0017] The third heat exchanger is used to regulate the temperature of the material entering the third hydrogenation reactor;

[0018] The third hydrogenation reactor; and

[0019] The fourth heat exchanger is used to recover heat from the material exiting the third hydrogenation reactor;

[0020] The first hydrogenation reactor is equipped with a material analyzer, a flow meter, and a temperature sensor at its inlet. A temperature sensor is also installed at its outlet. Temperature sensors and flow meters are installed at the inlets of the second and third hydrogenation reactors, respectively, and temperature sensors are installed at their outlets. All three reactors are adiabatic.

[0021] It also includes a controller, which controls the temperature of the material entering the inlet of the first hydrogenation reactor by controlling the flow rate of the fluid used for heat exchange in the first heat exchanger, and further controls the temperature rise of the material at the outlet and inlet of the first hydrogenation reactor within a range of T. 升 -1 to T 升 between,

[0022] T 升 =T 乙炔 *Q1 / X,

[0023] Among them, T 乙炔 Theoretically, this is the temperature at which the heat from the complete conversion of acetylene in the cracked gas into ethylene causes the temperature of the reaction system to rise.

[0024] Q1 is the percentage of acetylene that participates in the hydrogenation reaction in the first hydrogenation reactor;

[0025] X represents the reaction selectivity of the acetylene hydrogenation reaction to convert ethylene.

[0026] Preferably, Q1 is 70% to 90%.

[0027] Preferably, T 乙炔 =qm' 乙炔 / qm 乙炔 *T 总 ,

[0028] Among them, T 总 The sum of the temperature rises of the second and third hydrogenation reactors before the temperature rise range between the outlet and inlet of the first hydrogenation reactor (i.e., the temperature rise of the first hydrogenation reactor) is adjusted.

[0029] Assuming the temperature rise in the reaction system is entirely due to the hydrogenation of acetylene to ethylene, i.e., qm 乙炔 According to T 总 Calculate the theoretical mass flow rate of acetylene;

[0030] qm 乙炔 =Flux*T 总 *Cp / ΔH 乙炔 *Molar mass of acetylene

[0031] Where Flux is the average mass flow rate in the first, second, and third hydrogenation reactors.

[0032] Cp is the specific heat of the cracked gas.

[0033] ΔH 乙炔 The heat of reaction for the hydrogenation of acetylene to form ethylene.

[0034] The molar mass of acetylene is 26 g / mol;

[0035] qm' 乙炔 This is the acetylene mass flow rate calculated based on the actual measured flow rate and content.

[0036] qm' 乙炔 =Flux*ω乙炔 ,

[0037] ω 乙炔 This represents the mass percentage of acetylene in the feed at the inlet of the first hydrogenation reactor.

[0038] Preferably, the first hydrogenation reactor is an adiabatic fixed-bed reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst; more preferably, the catalyst may be selected from Clariant's Olemax 252-3 or Chevron Phillips' E-Series. TM One or more of FE-EDC3-2 or CRI KL7741B-R6.

[0039] Preferably, the second hydrogenation reactor is an adiabatic fixed-bed reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst; more preferably, the catalyst can be selected from Clariant's Olemax 252-3 or Chevron Phillips' E-Series. TM One or more of FE-EDC3-2 or CRI KL7741B-R6.

[0040] Preferably, the third hydrogenation reactor is an adiabatic fixed-bed reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst; more preferably, the catalyst can be selected from Clariant's Olemax 252-3 or Chevron Phillips' E-Series. TM One or more of FE-EDC3-2 or CRI KL7741B-R6.

[0041] Preferably, the first heat exchanger is a shell-and-tube type heat exchanger heated by low-pressure steam, wherein the fluid used for heat exchange is water or steam.

[0042] Preferably, the second heat exchanger is a shell-and-tube heat exchanger cooled by circulating water.

[0043] Preferably, the third heat exchanger is a shell-and-tube heat exchanger cooled by circulating water.

[0044] Preferably, the fourth heat exchanger is a shell-and-tube heat exchanger cooled by circulating water.

[0045] Preferably, a first straight-through pipe is provided between the first hydrogenation reactor and the second hydrogenation reactor, and is connected in parallel with the second heat exchanger. The temperature of the material entering the second hydrogenation reactor is controlled by controlling the flow ratio between the first straight-through pipe and the second heat exchanger.

[0046] Preferably, a second straight-through pipe is provided between the second and third hydrogenation reactors, and is connected in parallel with the third heat exchanger. The temperature of the material entering the second hydrogenation reactor is controlled by controlling the flow ratio between the straight-through pipe and the third heat exchanger.

[0047] According to a second aspect of the present invention, a method for reducing ethylene loss in a cracked gas ethylene production process is provided, comprising performing the following steps after the cracked gas ethylene production process has reached a stable operating state:

[0048] The flow rate of the fluid used for heat exchange in the first heat exchanger is controlled by a controller, so that the temperature rise in the first hydrogenation reactor is within a range of T. 升 -1 to T 升 between,

[0049] T 升 =T 乙炔 *Q1 / X, where,

[0050] T 乙炔 The temperature at which the heat required for all acetylene in the cracked gas to be converted into ethylene theoretically leads to an increase in the temperature of the reaction system.

[0051] Q1 is the percentage of acetylene that participates in the hydrogenation reaction in the first hydrogenation reactor;

[0052] X represents the reaction selectivity of the acetylene hydrogenation reaction to convert ethylene.

[0053] Preferably, T 乙炔 =qm' 乙炔 / qm 乙炔 *T 总 ,

[0054] Among them, T 总 The sum of the temperature rises of the second and third hydrogenation reactors is used to regulate the temperature rise range of the material before the first hydrogenation reaction at the outlet and inlet of the first hydrogenation reactor.

[0055] Assuming the temperature rise in the reaction system is entirely due to the hydrogenation of acetylene to ethylene, i.e., qm 乙炔 According to T 总 Calculated theoretical mass flow rate of acetylene:

[0056] qm 乙炔 =Flux*T 总 *Cp / ΔH 乙炔 *Molar mass of acetylene

[0057] Where Flux is the average mass flow rate in the first, second, and third hydrogenation reactors.

[0058] Cp is the specific heat of the cracked gas.

[0059] ΔH 乙炔 The heat of reaction for the hydrogenation of acetylene to form ethylene.

[0060] The molar mass of acetylene is 26 g / mol;

[0061] qm' 乙炔 This is the acetylene mass flow rate calculated based on the actual measured flow rate and content.

[0062] qm' 乙炔 =Flux*ω 乙炔 ,

[0063] ω 乙炔 This represents the mass percentage of acetylene in the feed at the inlet of the first hydrogenation reactor.

[0064] Preferably, Q1 is 70% to 90%.

[0065] It should be noted that in this invention, the degree of reaction in the first hydrogenation reactor is indirectly adjusted by regulating the temperature of the cracked gas entering the first hydrogenation reaction, thereby achieving regulation of the temperature rise range in the first hydrogenation reactor. For example, when the temperature of the reactants entering the first hydrogenation reactor is high, the reaction is vigorous, the heat generated is large, and the temperature rise of the hydrogenation reaction is relatively high. Conversely, when the temperature of the reactants entering the first hydrogenation reactor is low, the reaction is less vigorous, the heat generated is relatively low, and the temperature rise of the hydrogenation reaction is relatively low.

[0066] The reaction equations and energy releases for the hydrogenation of acetylene to form ethylene and the hydrogenation of ethylene to form ethane are as follows:

[0067] C2H2 + H2 → C2H4 - 175.7 KJ / mol, that is, the enthalpy change of acetylene to ethylene is ΔH. 乙炔 = -175.7 kJ / mol,

[0068] C2H4 + H2 → C2H6 - 138.1 KJ / mol, that is, the enthalpy change (ΔH) of the hydrogenation of ethylene to form ethane. 乙烯 = -138.1 KJ / mol.

[0069] Preferably, before adjusting the temperature rise range between the outlet and inlet of the first hydrogenation reactor, the ethylene production process from cracked gas is operated smoothly under the following set operating conditions:

[0070] The pressure of the first hydrogenation reactor is 3-4 MPa, preferably 3.5-4 MPa; the inlet temperature is 60-70°C, preferably 63-70°C.

[0071] The pressure of the second hydrogenation reactor is 3-4 MPa, preferably 3.5-4 MPa; the inlet temperature is 65-75°C, preferably 70-75°C.

[0072] The flow rate of the third hydrogenation reactor is 3-4 MPa, preferably 3.5-4 MPa; the inlet temperature is 65-75℃, preferably 70-75℃.

[0073] Preferably, the temperature of the cracked gas at the inlet of the first hydrogenation reactor is controlled by adjusting only the flow rate of the heat exchange fluid in the first heat exchanger, thereby controlling the temperature rise in the first hydrogenation reactor to be within the range of T. 升 -1 to T 升 between.

[0074] Preferably, the flow rates of the fluids used for heat exchange in the second and third heat exchangers are not adjusted, allowing the second hydrogenation reaction and the third hydrogenation reactor to self-adaptively adjust.

[0075] The method for reducing ethylene loss in the pyrolysis gas to ethylene production process according to the present invention reduces ethylene loss by controlling the temperature rise range in the first hydrogenation reactor within a specific range, thereby achieving significant economic benefits. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of a system for reducing ethylene loss in a pyrolysis gas ethylene production process according to an embodiment of the present invention. Detailed Implementation

[0077] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the application scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0078] Example 1

[0079] like Figure 1 As shown, the system for reducing ethylene hydrogenation losses according to the present invention, along the direction of cracked gas flow, sequentially comprises: a dryer D1 (not shown) for drying cracked gas; a first heat exchanger E-1382; a first hydrogenation reactor R-1385-1; a second heat exchanger E-1384; a second hydrogenation reactor R-1385-2; a third heat exchanger E-1385; a third hydrogenation reactor R-1385-3; and a fourth heat exchanger E-1386.

[0080] Before entering the dryer, the cracked gas has already passed through high and low pressure depropane removal, and then been cooled by cooling water and dearsenic removal bed.

[0081] The treated pyrolysis gas enters dryer D1 for drying. The dried pyrolysis gas then enters the first heat exchanger E-1382, where its temperature is raised. After passing through the first heat exchanger E-1382, the pyrolysis gas then sequentially enters the first hydrogenation reactor R-1385-1, the second heat exchanger E-1384, the second hydrogenation reactor R-1385-2, the third heat exchanger E-1385, the third hydrogenation reactor R-1385-3, and the fourth heat exchanger E-1386.

[0082] Before adjusting the flow rate of the fluid used for heat exchange to control the temperature rise range between the outlet and inlet of the first hydrogenation reactor, the stable operating conditions of the reaction system are as follows:

[0083] The pressure of the first hydrogenation reactor R-1385-1 is 3.78 MPa, and the inlet temperature is 65℃.

[0084] Pressure of the second hydrogenation reactor R-1385-2: 3.78 MPa; Inlet temperature: 72℃.

[0085] Pressure of the third hydrogenation reactor R-1385-3: 3.78 MPa; Inlet temperature: 72℃.

[0086] A gas chromatograph (Yokogawa DC8000) was installed at the inlet of the first hydrogenation reactor R-1385-1 to analyze the composition of the cracked gas entering the first hydrogenation reactor R-1385-1. The results are shown in Table 1.

[0087] The first hydrogenation reactor, R-1385-1, is a fixed-bed adiabatic reactor, and the catalyst used is Chevron Phillips E-Series™ FE-EDC3-2.

[0088] The second hydrogenation reactor, R-1385-2, is a fixed-bed adiabatic reactor, and the catalyst used is Chevron Phillips E-Series™ FE-EDC3-2.

[0089] The third hydrogenation reactor, R-1385-3, is a fixed-bed adiabatic reactor, and the catalyst used is Chevron Phillips E-Series™ FE-EDC3-2.

[0090] The fourth heat exchanger, E-1386, ensures that the temperature of the material exiting the fourth heat exchanger is 40°C in order to recover heat.

[0091] Table 1: Percentage of each gas at the inlet of the first hydrogenation reactor R-1385-1

[0092]

[0093]

[0094] *Propylene MAPT is CH2=CH2=CH2

[0095] 1. Calculate the heat generated by the hydrogenation reaction in the cracked gas.

[0096] The temperature of the material at the inlet of the first hydrogenation reactor R-1385-1 was measured to be 65℃ using a temperature sensor, and the temperature at the outlet of the material in the first hydrogenation reactor R-1385-1 was measured to be 76.2℃. The temperature rise T1 = 11.2℃ was calculated.

[0097] The material temperature at the inlet of the second hydrogenation reactor R-1385-2 was measured to be 72℃ using a temperature sensor, and the material temperature at the outlet of the second hydrogenation reactor R-1385-2 was measured to be 75.5℃. The temperature rise T2 was calculated to be 3.5℃.

[0098] The material temperature at the inlet of the third hydrogenation reactor R-1385-3 was measured to be 72℃, and the material temperature at the outlet of the third hydrogenation reactor R-1385-3 was measured to be 74.5℃. The temperature rise T3 = 2.5℃ was calculated.

[0099] The material exiting the third hydrogenation reactor R-1385-3 enters the fourth heat exchanger E-1386 and is cooled to 40°C.

[0100] The flow rate of the reactor is the average of the flow rates Flux1 of the first hydrogenation reactor, Flux2 of the second hydrogenation reactor, and Flux3 of the third hydrogenation reactor, that is,

[0101] Among them, Flux1, Flux2 and Flux3 were measured to be 375t / h, 370t / h and 365t / h respectively. The calculated Flux = (Flux1 + Flux2 + Flux3) / 3 = 370 (t / h) = 370000 (kg / h);

[0102] Average molecular mass: M = 26*A + 28*B + 28*C + 40*D + 40*E + 42*F + 30*G + 40*H + 2*I + 16*J + 50*K. Based on the percentages of each gas measured in Table 1, the average weight is calculated to be M = 24.5497 (kg / kmol).

[0103] Calculate the total temperature rise caused by the hydrogenation reaction: T 总 =T1+T2+T3=11.2+3.5+2.5=17.2(℃);

[0104] The specific heat of the cracked gas containing the components in Table 1 is Cp, which is 2.3012 kJ / (kg·℃).

[0105] The actual heat generated in the hydrogenation reaction is calculated based on the flow rate, specific heat, and temperature rise:

[0106] Heat = Flux * T 总 *Cp=370000(kg / h)*17.2(℃)*2.3012(kJ / (kg.℃))=14630836(kJ / h).

[0107] 2. Calculate the amount lost during the hydrogenation of ethylene to ethane.

[0108] Calculate the average molecular mass based on the molar concentration and molecular weight number, and then calculate the mass percentage of acetylene: ω 乙炔 =26*A / (26*A+28*B+28*C+40*D+40*E+42*F+30*G+40*H+2*I+16*J+50*K), calculate ω based on the measurement results in Table 1. 乙炔 =0.34957wt%.

[0109] The reaction equations and energy releases for the hydrogenation of acetylene and ethylene are as follows:

[0110] C2H2 + H2 → C2H4 - 175.7 KJ / mol, that is, the enthalpy change of acetylene to ethylene is ΔH. 乙炔 =175.7 kJ / mol,

[0111] C2H4 + H2 → C2H6 - 138.1 KJ / mol, that is, the enthalpy change (ΔH) of the hydrogenation of ethylene to form ethane. 乙烯 =138.1 kJ / mol,

[0112] Assuming the temperature rise in the reaction system is entirely due to the hydrogenation of acetylene to ethylene, calculate the theoretical molar flow rate of acetylene:

[0113] M 乙炔 =Heat / ΔH 乙炔 =14630836(kJ / h) / 175.7(kJ / mol)=83271.7(mol / h)

[0114] Mass flow rate converted to acetylene: qm 乙炔 =M 乙炔 * Acetylene molecular weight = 83271.7 (mol / h) * 28 (g / mol) = 2331607.6 (g / h) = 2.33161 (t / h);

[0115] ω of acetylene at the inlet 乙炔=0.34957%, with an average flow rate of 370 t / h;

[0116] The actual acetylene mass flow rate is qm' 乙炔 =Flux*ω 乙炔 =370(t / h)*0.34957%=1.29341(t / h).

[0117] The remaining heat is generated from the hydrogenation of ethylene into ethane, therefore the flow rate of hydrogenated ethylene is:

[0118] qm 乙烯 =(qm 乙炔 -qm' 乙炔 )*(ΔH 乙炔 / ΔH 乙烯 )=(2.33161(t / h)-1.29341(t / h))

[0119] *[(-175.7(KJ / mol)) / (-138.1(KJ / mol))]=1.03820(t / h)*1.27227=1.32087(t / h).

[0120] In other words, even if acetylene is completely converted into ethylene, 1.32087 (t / h) of ethylene will be converted into ethane, resulting in a loss of ethylene.

[0121] 3. Temperature control

[0122] In the first hydrogenation reactor R-1385-1, assuming all acetylene is hydrogenated to ethylene, the resulting temperature increase would be:

[0123] T 乙炔 =qm' 乙炔 / qm 乙炔 *T 总 =1.29341(t / h) / 2.33161(t / h)*17.2(℃)=9.54132

[0124] (°C)

[0125] That is, the temperature rise caused by the hydrogenation reaction of acetylene in the cracked gas to ethylene is 9.54132℃; that is, when the temperature rise of the first hydrogenation reactor is greater than 9.54132℃, the acetylene reaction is assumed to be complete.

[0126] Temperature control can be achieved by adjusting the ratio of bypass valves to valves in the pipes entering the heat exchanger.

[0127] In the first hydrogenation reactor, approximately 80% of the acetylene hydrogenation reaction is set to ethylene, i.e., Q1 = 80%. Considering selectivity, assuming a selectivity of X = 0.75, the temperature rise T in the first hydrogenation reactor is... 升 =T 乙炔 *(1 / X)*80%=9.54125(℃)*1 / 0.75*80%=10.17733(℃)

[0128] When the temperature of the first hydrogenation reactor R-1385-1 rises above T 升 When this happens, the flow rate of the circulating water in the first heat exchanger E-1382 is adjusted to reduce the temperature of the cracked gas entering the first hydrogenation reactor R-1385-1 until the temperature rise of the reaction system in the first hydrogenation reactor R-1385-1 reaches T. 升 -1 to T 升 Between 9.17733 and 10.17733 (°C).

[0129] In this invention, it is only necessary to adjust the temperature at the inlet end of the first hydrogenation reactor R-1385-1 to regulate the temperature difference between the inlet and outlet ends of the first hydrogenation reactor R-1385-1 within a specific range. The other heat exchangers, the second hydrogenation reactor, and the third hydrogenation reactor maintain their original conditions and continue to operate in a self-balancing manner.

[0130] Analysis of the material at the outlet of the third hydrogenation reactor yielded the following data:

[0131] Table 2: Percentage of each gas at the outlet of the third hydrogenation reactor R-1385-3

[0132] materials Concentration (V / V)% Concentration (m / m)% Acetylene 0 0 propane 13.13860759 23.7512 propylene 9.944454494 17.15986 Propylene 0.015313677 0.025167 Propylene 0.080254354 0.13189 Ethane 4.960671552 6.114279 ethylene 30.49502293 35.08088 methane 24.75019228 16.2698 carbon monoxide <![CDATA[270.9242062*10 -7 ]]> 0.000312 hydrogen 16.73814568 1.375374 C4 0.044419082 0.091248

[0133] The mass of acetylene consumed = flow rate * mass concentration difference before and after the reaction = 370 (t / h) * (0.34956% - 0%) = 1.29337 (t / h);

[0134] When all of it is converted into ethylene, the corresponding increase in the mass of ethylene is 1.29337 (t / h) * (28 / 26) = 1.39286 (t / h).

[0135] The theoretical ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 = 370 (t / h) * 34.76860% + 1.39286 (t / h) = 130.03668 (t / h).

[0136] The mass of ethylene lost = theoretical ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 - actual ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 = 130.03668 (t / h) - 370 (t / h) * 35.08088% = 0.23742 (t / h).

[0137] Comparative Example 1

[0138] The reactor was operated in its original state as described in Example 1 without any adjustments. The percentages of each gas at the inlet of the first hydrogenation reactor and the outlet of the third hydrogenation reactor were measured, and the results are shown in Tables 3 and 4.

[0139] Table 3: Percentage of each gas at the inlet of the first hydrogenation reactor R-1385-1

[0140] Concentration (V / V)% Concentration (m / m)% Acetylene 0.361205406 0.378177 carbon monoxide <![CDATA[275.7119884*10 -7 ]]> 0.000311 ethylene 30.41458822 34.29314 Propylene 0.134399385 0.216483 Propylene 0.094291069 0.151879 propylene 10.78226015 18.23587 Ethane 4.206911446 5.082202 propane 13.71237523 24.29588 hydrogen 17.23689665 1.388214 methane 24.65987418 15.88833 C4 0.034521296 0.069506

[0141] Table 4: Percentage of each gas at the outlet of the third hydrogenation reactor R-1385-3

[0142] Concentration (V / V)% Concentration (m / m)% Acetylene 0 0 propane 13.73884605 23.9047 propylene 12.24326624 20.33419 Propylene 0.018221082 0.028821 Propylene 0.080675878 0.12761 Ethane 4.140319386 4.911741 ethylene 30.46999268 33.73733 methane 24.50292111 15.50309 carbon monoxide <![CDATA[242.3195902*10 -7 ]]> 0.000268 hydrogen 16.93967741 1.339724 C4 0.056900539 0.112504

[0143] The mass of acetylene consumed = flow rate * mass concentration difference before and after the reaction = 370 (t / h) * (0.37818% - 0%) = 1.39927 (t / h);

[0144] When all of it is converted into ethylene, the corresponding increase in the mass of ethylene is 1.39927 (t / h) * (28 / 26) = 1.50690 (t / h).

[0145] The theoretical ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 = 370 (t / h) * 34.29314% + 1.50690 (t / h) = 128.39152 (t / h).

[0146] The mass of ethylene lost = theoretical ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 - actual ethylene mass at the outlet of the third hydrogenation reactor R-1385-3 = 128.39152 (t / h) - 370 (t / h) * 33.73733% = 3.56340 (t / h).

[0147] Comparing Example 1 and Comparative Example 1, it can be seen that using the method according to the present invention can reduce ethylene loss by 3.56340 t / h, resulting in significant economic benefits.

Claims

1. A system for reducing ethylene loss in a process for producing ethylene from cracked gas, comprising: connected sequentially along the feed direction: Dryer, used to dry pyrolysis gas; The first heat exchanger is used to regulate the temperature of the material entering the first hydrogenation reactor; First hydrogenation reactor; The second heat exchanger is used to regulate the temperature of the material entering the second hydrogenation reactor; Second hydrogenation reactor; The third heat exchanger is used to regulate the temperature of the material entering the third hydrogenation reactor; Third hydrogenation reactor; and The fourth heat exchanger is used to recover heat from the material exiting the third hydrogenation reactor; The first hydrogenation reactor is equipped with a material analyzer, a flow meter, and a temperature sensor at its inlet. A temperature sensor is also installed at its outlet. Temperature sensors and flow meters are installed at the inlets of the second and third hydrogenation reactors, respectively, and temperature sensors are installed at their outlets. All three reactors are adiabatic. It also includes a controller for controlling the flow rate of the fluid used for heat exchange in the first heat exchanger, thereby controlling the temperature of the material entering the inlet of the first hydrogenation reactor. Furthermore, the temperature of the material affects the degree of hydrogenation reaction, thus controlling the temperature rise of the reactants within a range of T between the outlet and inlet of the first hydrogenation reactor. 升 -1 to T 升 between, T 升 =T 乙炔 *Q1 / X, Among them, T 乙炔 Theoretically, this is the temperature at which the heat from the complete conversion of acetylene in the cracked gas into ethylene causes the temperature of the reaction system to rise. Q1 is the percentage of acetylene that participates in the hydrogenation reaction in the first hydrogenation reactor; X represents the reaction selectivity of the acetylene hydrogenation reaction to convert ethylene.

2. The system for reducing ethylene loss in the ethylene production process from cracked gas according to claim 1, wherein, Q1 is 70%~90%.

3. The system for reducing ethylene loss in the ethylene production process from cracked gas according to claim 1, wherein, T 乙炔 = qm’ 乙炔 / qm 乙炔 *T 总 , Among them, T 总 The sum of the temperature rises of the second and third hydrogenation reactors before the temperature rise range of the material at the outlet and inlet of the first hydrogenation reactor is adjusted. Assuming the temperature rise in the reaction system is entirely due to the hydrogenation of acetylene to ethylene, i.e., qm 乙炔 According to T 总 Calculated theoretical mass flow rate of acetylene: qm 乙炔 = Flux*T 总 *Cp / ΔH 乙炔 *Molar mass of acetylene Where Flux is the average mass flow rate in the first, second, and third hydrogenation reactors. Cp is the specific heat of the cracked gas. ΔH 乙炔 The heat of reaction for the hydrogenation of acetylene to form ethylene. The molar mass of acetylene is 26 g / mol; qm' 乙炔 This is the acetylene mass flow rate calculated based on the actual measured flow rate and content. qm' 乙炔 =Flux*ω 乙炔 , ω 乙炔 This represents the mass percentage of acetylene in the feed at the inlet of the first hydrogenation reactor.

4. A system for reducing ethylene loss in a process for producing ethylene from cracked gas according to any one of claims 1 to 3, wherein, The first hydrogenation reactor is a fixed-bed adiabatic reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst; and / or The second hydrogenation reactor is a fixed-bed adiabatic reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst; and / or The third hydrogenation reactor is a fixed-bed adiabatic reactor, wherein the catalyst is a Pd-based catalyst or a Ni-based catalyst.

5. The system for reducing ethylene loss in the ethylene production process from cracked gas according to claim 4, wherein, The catalyst for the first hydrogenation reactor is Olemax 252-3 from Clariant and E-Series from Chevron Phillips. TM One or more of FE-EDC3-2 or CRI KL7741B-R6; and / or, The catalyst for the second hydrogenation reactor is Olemax 252-3 from Clariant and E-Series from Chevron Phillips. TM One or more of FE-EDC3-2 or CRI KL7741B-R6; and / or, The catalyst for the third hydrogenation reactor is Olemax 252-3 from Clariant and E-Series from Chevron Phillips. TM One or more of FE-EDC3-2 or CRI KL7741B-R6.

6. A system for reducing ethylene loss in a process for producing ethylene from cracked gas according to any one of claims 1 to 3, wherein, The first heat exchanger is a shell-and-tube type heat exchanger heated by low-pressure steam, wherein the fluid used for heat exchange is water or steam; and / or The second heat exchanger is a shell-and-tube heat exchanger cooled by circulating water; and / or The third heat exchanger is a shell-and-tube heat exchanger cooled by circulating water; and / or The fourth heat exchanger is a shell-and-tube heat exchanger cooled by circulating water.

7. A system for reducing ethylene loss in a process for producing ethylene from cracked gas according to any one of claims 1 to 3, wherein, A first straight-through pipe is provided between the first hydrogenation reactor and the second hydrogenation reactor, and is connected in parallel with the second heat exchanger. The temperature of the material entering the second hydrogenation reactor is controlled by controlling the flow ratio between the first straight-through pipe and the second heat exchanger; and / or A second straight-through pipe is installed between the second and third hydrogenation reactors and in parallel with the third heat exchanger. The temperature of the material entering the second hydrogenation reactor is controlled by controlling the flow ratio between the straight-through pipe and the third heat exchanger.

8. A method for reducing ethylene loss in a cracked gas ethylene production process, comprising the following steps after the cracked gas ethylene production process has reached stable operation: The flow rate of the fluid used for heat exchange in the first heat exchanger is controlled by a controller, so that the temperature rise in the first hydrogenation reactor is within a range of T. 升 -1 to T 升 between, T 升 =T 乙炔 *Q1 / X, where, T 乙炔 The temperature at which the heat required for all acetylene in the cracked gas to be converted into ethylene theoretically leads to an increase in the temperature of the reaction system. Q1 is the percentage of acetylene that participates in the hydrogenation reaction in the first hydrogenation reactor; X represents the reaction selectivity of the acetylene hydrogenation reaction to ethylene; Among them, T 总 The sum of the temperature rises of the second and third hydrogenation reactors is used to regulate the temperature rise range of the material before the first hydrogenation reaction at the outlet and inlet of the first hydrogenation reactor. Assuming the temperature rise in the reaction system is entirely due to the hydrogenation of acetylene to ethylene, i.e., qm 乙炔 According to T 总 Calculated theoretical mass flow rate of acetylene: qm 乙炔 = Flux*T 总 *Cp / ΔH 乙炔 *Molar mass of acetylene Where Flux is the average mass flow rate in the first, second, and third hydrogenation reactors. Cp is the specific heat of the cracked gas. ΔH 乙炔 The heat of reaction for the hydrogenation of acetylene to form ethylene. The molar mass of acetylene is 26 g / mol; qm' 乙炔 This is the acetylene mass flow rate calculated based on the actual measured flow rate and content. qm' 乙炔 =Flux*ω 乙炔 , ω 乙炔 This represents the mass percentage of acetylene in the feed at the inlet of the first hydrogenation reactor. The reactor consists of a first heat exchanger, a first hydrogenation reactor, a second heat exchanger, a second hydrogenation reactor, a third heat exchanger, and a third hydrogenation reactor, connected sequentially along the feed direction.

9. The method for reducing ethylene loss in the ethylene production process from cracked gas according to claim 8, wherein, T 乙炔 = qm’ 乙炔 / qm 乙炔 *T 总 。 10. The method for reducing ethylene loss in the ethylene production process from cracked gas according to claim 8, wherein, Q1 is 70% to 90%.

11. The method for reducing ethylene loss in the ethylene production process from cracked gas according to claim 8, wherein, Before adjusting the temperature rise range between the outlet and inlet of the first hydrogenation reactor, the ethylene production process from cracked gas is operated smoothly under the following conditions: The pressure of the first hydrogenation reactor is 3-4 MPa; the inlet temperature is 60-70°C. o C; The pressure of the second hydrogenation reactor is 3~4 MPa; the inlet temperature is 65~75℃. o C; The flow rate of the third hydrogenation reactor is 3-4 MPa; the inlet temperature is 65-75°C. o C.

12. The method for reducing ethylene loss in the ethylene production process from cracked gas according to claim 11, wherein, The pressure of the first hydrogenation reactor is 3.5~4 MPa; the inlet temperature is 63~70℃. o C; The pressure of the second hydrogenation reactor is 3.5~4 MPa; the inlet temperature is 70~75℃. o C; The flow rate of the third hydrogenation reactor is 3.5~4 MPa; the inlet temperature is 70~75℃. o C.

13. The method for reducing ethylene loss in a process for producing ethylene from cracked gas according to any one of claims 8 to 12, wherein, The temperature of the cracked gas at the inlet of the first hydrogenation reactor is controlled by adjusting the flow rate of the fluid used for heat exchange in the first heat exchanger, thereby controlling the range within which the temperature in the first hydrogenation reactor rises to within T. 升 -1 to T 升 Between; without adjusting the flow rates of the heat exchange fluids in the second and third heat exchangers, the second hydrogenation reaction and the third hydrogenation reactor are adaptively regulated.

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