TECHNICAL FIELD

The present invention relates to the technical field of tank reactors, and specifically to a slurry-bed tank reactor and a method of using the tank reactor, wherein materials are continuously fed into and discharged from the tank reactor.

BACKGROUND

A tank reactor is widely applied in industry. On the basis of operation mode, the tank reactor may be classified as a batch tank reactor, a semibatch tank reactor and a continuous tank reactor. In the continuous tank reactor, materials are continuously fed and discharged to achieve continuous operations and high efficiency. However, it is still a challenge to continuously operate a heterogeneous reaction in a tank reactor. Chinese Patent Application No. 2016105989527 provides a continuous operation method, but in the running process, solid powders are often adhered to tubular separation membranes, and hence, affecting the continuity of running, and the reflection of long catalytic life of a catalyst.

SUMMARY

To solve technical problems occurred in continuously operating a heterogeneous reaction in a tank reactor and to fully make use of the long catalytic life of a catalyst, one or more embodiments of the present invention provides a continuous slurry-bed tank reactor and a method of using it. One or more embodiments of the present invention provides a slurry-bed tank reactor in which a nanomaterial-based catalyst and reactants are directly separated. One or more embodiments of the present invention is applicable to catalysts with small particle sizes, even raw molecular sieve powder catalysts. Liquid materials and a catalyst are uniform slurries in the reactor, and reactants are fed into and discharged from the reactor in an uninterrupted and continuous operation manner.

One or more embodiments of the present invention is achieved by the following.

A continuous slurry-bed tank reactor comprises a tank reactor body, an agitator and tubular separation membranes.

The tank reactor body is equipped with a thermocouple for measuring the temperature of reaction mixture inside the tank reactor body, a liquid level gauge for measuring the liquid level inside the tank reactor body, a third pressure gauge for measuring the pressure inside the tank reactor body, and a gas flow controller for measuring the gas flow rate into the tank reactor body.

The agitator comprises an agitation motor, an agitation shaft and an agitation impeller. The agitation motor is located at the center over the tank reactor body. The rotor of the agitation motor is vertically downwards set up. One end of the agitation shaft is fixedly connected with the rotor of the agitation motor, and the other end thereof penetrates through the upper cap of the tank reactor body and extends to the bottom of the tank reactor body. The agitation impeller is installed at the bottom of the agitation shaft.

The tubular separation membranes comprise A and B tubular separation membranes, which are respectively vertically downwards set up on the two sides of the agitation shaft. The first and the second openings of the continuous slurry-bed tank reactor are respectively communicated with two transversely symmetrical ports of a four-way valve. The A and the B tubular separation membranes are respectively communicated with two longitudinally symmetrical ports of the four-way valve. The liquid was not simultaneously fed or discharged from the first and the second openings. A liquid feed pump is set up at the first opening and connected with the first counterbalance valve in parallel. The first pressure gauge is installed at the first counterbalance valve. The second counterbalance valve is positioned at the second opening, and in a pipeline connecting second counterbalance valve and the upper port of the four-way valve, a second pressure gauge is installed.

In addition, at least two auxiliary material spargers are installed at the lower portion of the side wall of the tank reactor body, and each one extends into the tank reactor body, is set up at a different position in the tank reactor body, and is communicated with an auxiliary material feed pump through another pipeline.

A method of using the continuous slurry-bed tank reactor comprises the following steps:

S1: adding a catalyst into the tank reactor body, and filling nitrogen gas in the tank reactor body by a gas flow controller until all air in the tank reactor body is replaced with nitrogen gas, wherein the gas flow controller measures and controls the flow rate of the nitrogen gas filled in the tank reactor body;

S2: feeding reactants into the tank reactor body sequentially through the liquid feed pump, the four-way valve and the A tubular separation membrane; using a liquid level gauge to measure the liquid level of the fed reactants and ensure that a distance between the liquid level of the reactants and the top cap of the tank reactor body is in the range of 5-80 cm; presetting the opening pressure of the first counterbalance valve to a value lower than the designed pressure of the tank reactor body by 0.3-0.5 MPa;

S3: when the liquid level of the reactants reaches the preset lower limit, stopping feeding the reactants; opening a heating system in the tank reactor body to raise the internal temperature of the tank reactor body to the preset temperature; opening the agitation system; determining the internal pressure of the tank reactor body at this moment as the initial pressure, and setting the opening pressure of the second counterbalance valve to be 0.3-0.8 MPa higher than the initial pressure; maintaining the temperature for 1-3 hours after the internal temperature of the tank reactor body is elevated to the preset temperature; turning on the liquid feed pump again to start continuously feeding the reactants;

S4: setting the four-way valve to switch flow paths once every 4-8 hours for altering the directions of reaction mixture flowing through the tubular separation membranes; resetting the four-way valve to switch the flow paths and recalculating the flow path switching time when the internal pressure of the tank reactor body is higher than the initial pressure by 0.8-1.0 MPa; stopping feeding the reactants when the time interval for switching the flow path is shorter than 2 hours because of the increase in the internal pressure of the tank reactor body.

Further, in step S2, at least two auxiliary material spargers are installed at the lower portion of the side wall of the tank reactor body. The auxiliary material feed pump adds reactants with poor miscibility in the tank reactor body through the auxiliary material spargers.

Further, in step S3, when the liquid feed pump starts to continuously feed the reactants, the gas flow controller is turned on. At the beginning, a small flow of nitrogen gas is filled. Afterwards, the flow rate of nitrogen gas is dynamically adjusted in terms of the changes of the liquid level. When the liquid level of the reaction mixture is close to the liquid level upper limit, the flow rate of nitrogen gas is increased. On the contrary, while the liquid level of the reaction mixture is approaching to the liquid level lower limit, the flow rate of nitrogen gas is reduced. When the liquid level of the reaction mixture exceeds the liquid level upper limit, the four-way valve is triggered to switch the flow paths. If the flow path switching time interval of the four-way valve is shorter than 2 hours due to the increase of the internal pressure of the tank reactor body, the filling of nitrogen gas would be stopped by closing the gas flow controller.

Further, the feeding amount of the liquid feed pump is determined to be 0.3-50 h−1of the weight hourly space velocity on the basis of the reactant conversion and the product selectivity.

When the flow path switching time interval of the four-way valve is decreased due to the increase of the internal pressure or the change of the liquid level, the feeding amount of the reaction mixture is reduced until the catalytic performance of the catalyst or the permeability of the tubular separation membranes cannot meet the demands.

One or more embodiments of the present invention have the following beneficial effects:

1, a slurry-bed reactor can allow a molecular sieve catalyst with small particle size fully show its excellent catalytic performance as a result of significantly weakening, and even eliminating the internal diffusion effect, thereby realizing high conversion of raw materials and high selectivity to products;

2, a conventional solid-liquid separation process is omitted by utilizing tubular separation membranes that the reactants and the catalyst are directly separated in the tank reactor so as to improve the working efficiency;

3, in a dual-mode time division countercurrent flow mode, adhesion of the solid catalyst to the tubular separation membranes is surmounted, the time of continuous and stable operation is prolonged, and the long catalytic life of the catalyst can be effectively reflected.

