RU2095337C1 - Method of controlling cyclic dehydrogenation process - Google Patents

Abstract

FIELD: industrial catalytic processes. SUBSTANCE: invention relates to reaction processes involving periodic regeneration of catalyst and consists in controlling furnace temperature by varying feeding gas into furnace, controlling temperature of mixture at reactor inlet, feeding raw material and steam into furnace, feeding air into reactor, varying temperature at reactor outlet, raising temperature of mixture at reactor inlet during each contacting cycle according to selected program, lowering feeding raw material according to selected program, and correcting feeding steam in proportion to feeding raw material. In each regeneration cycle, feeding steam is corrected in dependence on feeding raw material and temperature of mixture at reactor inlet in preceding contacting cycle, and feeding air is corrected in dependence on temperature at reactor inlet and outlet and feeding steam. EFFECT: automated reaction process. 1 dwg

Description

 The present invention relates to the field of automation of reaction processes involving periodic regeneration of a catalyst, in particular, the process of dehydrogenation of n-butylenes to divinyl, and can be used in the chemical and petrochemical industries.

 A known method of controlling the cyclic process of dehydrogenation of hydrocarbons by controlling the flow of raw materials and steam into the furnace, air into the reactor, steam temperature at the furnace outlet with a correction for the contact temperature and adjusting the supply of fuel gas to the furnace in proportion to its composition and the product of the pressure drop in the catalyst layer and the consumption of raw materials , as well as adjusting the air flow in proportion to the catalyst run time.

 The disadvantage of this method is the relatively low yield of the target product due to inefficient control of the temperature regime of contacting and regeneration.

 Closest to the technical nature of the present invention is a method for controlling the cyclic process of dehydrogenation of n-butylene in contact and regeneration modes, including controlling the temperature of the furnace by changing the supply of fuel gas to the furnace, the temperature of the mixture at the inlet of the reactor by changing the supply of saturated steam to the reactor, regulating the supply of raw materials into the furnace with correction for the concentration of divinyl in the contact gas, regulation of the water supply for irrigation of the scrubber with correction for the supply of raw materials, coding the temperature of the mixture at the inlet of the reactor is inversely proportional to the concentration of divinyl in the contact gas, regulating the air supply in the regeneration interval depending on the temperature profile in the reactor and its rate of change.

The disadvantage of this method is the relatively inefficient control mode of contacting and regeneration, since:
the steam supply is not taken into account (it is 3 4 times the feed rate), which largely determines the temperature conditions in the reactor;
no adjustment is made to the steam supply in the contacting and regeneration intervals.

 In addition, the measurement of the current concentration of divinyl in the contact gas is used in several control channels, which is practically not feasible with acceptable reliability, taking into account existing industrial analyzers.

 These factors reduce the yield of the target product on the skipped and decomposed raw materials and ultimately increase the specific consumption of raw materials and energy.

 The aim of the invention is to increase the yields of the target product on the missed and decomposed raw materials.

 This goal is achieved by the fact that in the known method of controlling the cyclic process of dehydrogenation of n-butylenes in contact and regeneration modes, including controlling the temperature of the furnace by changing the supply of fuel gas to the furnace, controlling the temperature of the mixture at the inlet of the reactor, regulating the supply of raw materials and steam to the furnace, air to reactor, additionally measure the temperature at the outlet of the reactor, in each contacting interval, increase the temperature of the mixture at the inlet of the reactor according to the program set by influencing those the furnace temperature, the feed rate is reduced according to the set program and the steam supply is adjusted proportionally to the feed rate, and in each regeneration interval, the steam supply is adjusted depending on the feed rate and the temperature of the mixture at the reactor inlet in the previous contact interval, and the air supply is adjusted depending on the temperature by reactor inlet and outlet and steam supply. The combination of new methods and control parameters in combination with the known ones gives the proposed method new properties, providing an increase in the yields of the target product due to the effective control of the contacting and regeneration modes.

 The essence of the invention is illustrated by an example and a drawing, which shows a schematic diagram of a system for automatically controlling the process of dehydrogenation of n-butylenes in the production of divinyl, which implements the proposed method.

 The dehydrogenation process is carried out in reactor 1 with a fixed catalyst bed, and the contact intervals (dehydrogenation proper) are alternated with regeneration intervals (burning coke from the pores of the catalyst) by periodically switching the valves 2 using a command device 3. Raw materials (n-butylene) after overheating in furnace 4 is fed into the reactor in a mixture of 1 3 1 4 with steam, which serves as a coolant. From the reactor, the vapor-gas mixture is either discharged into the atmosphere (in the regeneration interval) or is sent for purification (in the contact interval) to isolate the target product.

 The process control system includes temperature sensors 5 7, respectively, in the furnace 4 and at the inlet and outlet of the reactor 1, sensors 8 10 consumption, respectively, of raw materials, steam and air. The diagram also shows the functional blocks implemented in the microprocessor controller 11: the regulators 12 16, the program settings 17 and 18, the correction blocks 19-20 and the timer 21.

 The method is as follows.

 Using the command apparatus 3 by periodically closing-opening the valves 2, the reactor 1 is switched from contacting to regeneration and vice versa. Using the regulators 12-14, implemented in the microprocessor controller 11, according to the measurement from the sensors 8-10, regulate the supply of raw materials, steam and air, respectively. Using the controller 15, according to the measurement from the sensor 5, the temperature of the furnace 4 is controlled 4. Using the controller 16, according to the measurement from the sensor 6, the temperature of the mixture at the inlet of the reactor 1 is controlled by acting on the task of the controller 15 (cascade control).

 Using a programmer 17, implemented in the microprocessor controller 11, by acting on the controller 16, the temperature at the inlet of the reactor 1 is smoothly increased in the contact interval, thereby compensating for the decrease in catalyst activity caused by coking of the pores. Using a software setter 13, by acting on the controller 12, the feed rate in the contact interval is smoothly reduced while increasing the contact time in the reactor to compensate for the drop in catalyst activity.

G_n значение подачи пара, измеряемое с помощью датчика 9,
t_вх, t_вых значения температуры на входе и выходе реактора, измеряемые с помощью датчиков соответственно 6 и 7,
t_пр предельно допустимое значение температуры выхода.Using block 19 adjust the air supply in the regeneration interval by acting on the task of the regulator 14, for example, according to the following law:
G $\genfrac{}{}{0ex}{}{\text{ass}}{\text{in}}$ = G $\genfrac{}{}{0ex}{}{\text{about}}{\text{in}}$ + G $\genfrac{}{}{0ex}{}{\text{core}}{\text{in}}$ ,
Where

G _{n the} value of the steam supply, measured using the sensor 9,
t _in , t _out the temperature at the inlet and outlet of the reactor, measured using sensors 6 and 7, respectively
t _{pr the} maximum permissible output temperature.

Using block 20 adjust the steam supply:
in the contact interval, for example, according to a linear law:
G $\genfrac{}{}{0ex}{}{\text{pfl}}{\text{n}}$ = K ₄ + K ₅ G _c
Where
G _{with the} value of the feed, measured using the sensor 8;
in the regeneration interval, for example, according to the following law:
G $\genfrac{}{}{0ex}{}{\text{ass}}{\text{n}}$ = K ₆ + K ₇ G _c + K ₈ t _in ,
Where
G, t are the values measured in the middle of the previous contact interval.

The coefficients K ₁ K _{8 are} selected depending on the size of the reactor, the batch of the catalyst and other technological conditions for the functioning of the dehydrogenation process.

 Using the timer 21 synchronize the operation of the functional blocks implemented in the controller 11, with the cycles of the dehydrogenation reactor.

 An increase in the dehydrogenation temperature and a decrease in the supply of raw materials according to a given program, as well as maintaining the degree of dilution of the raw materials with steam, make it possible to optimally maintain the ratio of the rates of the main reaction (dehydrogenation) and side reactions taking into account the changing process conditions (coking of the catalyst, non-stationarity). The regulation of the steam supply, taking into account the supply of raw materials and the temperature of the mixture, and the regulation of the air supply, taking into account the temperature at the inlet-outlet of the reactor and the steam supply, make it possible to optimally restore the catalyst activity during regeneration. All these factors increase the yields of the target product (divinyl) on the passed and decomposed raw materials.

 An experimental verification of the proposed method in an industrial environment, conducted in January 1996 at the Sterlitamak JSC "Rubber", showed the effectiveness and usefulness of the method. The implementation of the control system that implements the proposed method based on the Remicont 130 microprocessor controllers is scheduled for the 2nd quarter of 1996. Due to the introduction of the method, it is expected to increase the yield on skipped raw materials by 0.3-0.4% and on decomposed raw materials by 0.5-0.6%

Claims (1)

 A method for controlling the cyclic process of dehydrogenation of n-butylene in contact and regeneration modes, including controlling the temperature of the furnace by changing the supply of fuel gas to the furnace, controlling the temperature of the mixture at the inlet of the reactor, regulating the supply of raw materials and steam to the furnace, and air to the reactor, characterized in that, In order to increase the yields of the target product for the passed and decomposed raw materials, the temperature at the outlet of the reactor is additionally measured, in each contacting interval the temperature of the mixture at the inlet p is increased According to the set program, the factors affect the furnace temperature, the feed rate is reduced according to the set program and the steam supply is adjusted proportionally to the feed rate, and in each regeneration interval, the steam supply is adjusted depending on the feed rate and the temperature of the mixture at the reactor inlet in the previous contacting interval and the air supply is adjusted depending on the temperature at the inlet and outlet of the reactor and steam supply.