环境工程原理全英论文

1、Investigation of Measures of Decreasing the Influence of Bubble in Fluidized BedName: Zhang YunaMajor : Environmental Science Student ID : 1314116010Supervisor : RomaHenan Agricultural University December, 2015ContentsContents1Abstract21 Introduction32 Fast Fluidization43 Add inner-loop62.1 baffle i

2、nner-loop62.2 filler inner-loop72.3 Grille Inner-loop72.4 Vertical Sieve Tray inner-loop84 Conclusion9Abstractthe fluidized bed reactor had more extensive application field. In accordan with the issue of the inpact of bubble in fluidized bed, two approaches were summarized to improve the negative im

3、pact that one was improving the fluidization gas velocity, the fluidized bed operation to the development of fast fluidization and anther was adding inner loop within the fluidized bed to improve gas-solid transfer efficiency by restrain or eliminate bubble.Key words: Fluidized bed; Inner-loop; Fast

4、 fluidization 1 IntroductionThe fluidized bed reactor is suitable for catalytic and non-catalytic gas-solid, liquid-solid and liquid-solid reaction system, is a reactor on a wide range of industrial applications.The reaction temperature has stabilized, heat strong and continuous catalyst recycling,

5、etc., it is widely used industrial areas, especially the petrochemical industry.Because ordinary bubble bubbling bed in the generation of the bubble phase and emulsion phase to produce low contact efficiency, the impact of mass transfer. andGenerate and grow the bubble was caused by slugging, channe

6、ling irregularities occurred. Bubbles in the fluidized bed against the adverse effects of fluidized bed some improvements can be divided into: improve the flow of the gas velocity, the fast fluidized development; added in the fluidized bed inside the inner-loop.2 Fast FluidizationIn recent years, th

7、e operation of the fluidized bed to the moving fluidized turbulent, fast and dilute phase conveying fluidized state high velocity state development. Compared with the low-speed fluidized, fast fluidized exhibit significantly different and good operating characteristics. When the fluid through the gr

8、owth speed of the device, the fluid and the relative velocity of solids will also increase. The more obvious advantages of high gas velocities in the downstream solid system. Therefore, a wide range of fluid velocities, the bed can maintain a higher concentration of the powder, no bubbles exist, eli

9、minating the irregularities caused by bubbles, thereby strengthening the powder between the fluid and the heat and mass quality. With operations increase the flow rate of fluid and particle structure of two-phase flow and flow pattern will undergo significant changes, a corresponding change in the s

10、tudy of two-phase flow structure under different flow rates has become an important research fluidized system of one.Widely used in industrial gas - solid circulating fluidized bed is mainly carried out in the fast fluidization. And wherein the gas-solid flow upward fast circulating fluidized bed ri

11、ser is now widely used in fluid catalytic cracking unit, and achieved certain economic benefits. Using riser reactor fluidized bed process compared with traditional gas-solid back-mixing can be reduced, to a certain extent, to avoid a reaction to the oil and gas back mixing and further down the dept

12、h of cracked gas and coke occur. Gas-solid flow upstream flow conditions and provide for good fluidization gas-solid contacting and heat and mass transfer conditions, but due to a serious degree of back-mixing gases and particles, is not conducive to improve the conversion rate and selectivity.Gas-s

13、olid flow lines and movement along the gravitational field of gas-solid with good transmission characteristics can effectively reduce the axial back mixing and gas-solid particle residence time. Anhui Huainan Chemical Group Co., Ltd. Construction of 30kt · a-1 industrial test equipment using te

14、chnology developed by Tsinghua University in FMTP.Using gas-solid flow line and the contact reactor ultrashort. The test results showed that: 99 per pass conversion of methanol Chang 5 percent, to reach 67.3% propylene selectivity. Gas-solid contact time within a downer very short, and therefore nee

15、d to quickly achieve uniform particles and gases and mixed at the entrance, rapid gas-solid separation in exports. Catalyst inlet means Wei Fei, who invented, simple structure, flexible operation, low pressure drop, and equipment and other small particles in the advantages of wear. Luoyang Petrochem

16、ical EngineeringGas-solid inlet device designed Cheng Co., an effective solution to the current gas-solid inlet means the existence of complex structure, easy to plug and maintenance difficulties and other problems. Tsinghua utilizing the Coanda effect gas-solid two-phase flow in different inertial

17、force and particle motion, the development of new gas-solid separation device with a cutting board for achieving rapid gas-solid separation, you can strict control of gas-solid contact time, reducing unnecessary depth cracking, improve product yield, but also can reduce catalyst loss at the cyclone,

18、 can significantly improve the separation efficiency of up to 97%, significantly shortening the gas-solid contact time.3 Add inner-loopadd inner-loop may affect the flow of the gas-solid state in fluidized bed,The inner inner-loop can be suppressed and the bubbles break, improve gas in the bed of th

19、e residence time distribution, reducing the gas phase backmixing, to reduce the particle out. It can be increased by strengthening the gas-solid contact with the chemical reaction conversion rate, improve the selectivity and yield. So join the inner-loop will help to improve hydrodynamic properties

20、and mass transfer efficiency within the fluidized bed. Currently the inner-loop common horizontal inner-loop, vertical members and solid fillers. Its structure and setting different way in the bed, so they are not the same operating performance.3.1 Baffle inner-loopIn the fluidized bed can be added

21、to the horizontal flap bed divided into several regions, the gas passes through the baffle can be re-distributed, effectively reducing the residence time distribution of the gas-solid phase, while crushing large bubble suppression slugging bed phenomenon, reduce the amount of solid particles with, r

22、educing the diffusion resistance, effectively improve the mass and heat transfer between the gas-solid. Because of the baffle reduces the strength of solid particles in the circulating fluidized bed, the presence of solid particles of very dilute low-density area at the bottom of each baffle affect

23、the uniformity of the reactor heat transfer and temperature; the bed elutriation effect of fine particles affect the flow of mass destruction and other negative factors fluidized bed operation.The original disc-shaped annular baffle and baffle people do not speak, the separation effect is poor, whil

24、e enabling the fluidized bed to reduce the available space, the gas-solid flow is uneven, prone to flooding and partial loss of fluidized flow and so on. Through continuous improvement of domestic and foreign researchers.The opening bezel, installing solid particles flow conduit and other methods to

25、 improve the gas-solid contacting effect, a more stable fluidized state, and can inhibit reversion broken bubble mix. But it remains solid particles prone to channeling phenomenon in the process of movement, limiting further enhance the mass transfer effects. To solve this problem to make further im

26、provements, plus baffles located between the guide plate and a separator to improve the efficiency of the mass transfer, but because of the strength of the bezel so that the flow of solid particles greatly weakened, it will affect the temperature of Evenly distributed.3.2 Filler inner-loopIn order t

27、o increase the contact area of the gas and liquid to enhance mass transfer efficiency, often in the tower add fillers, such as Raschig rings or Pall ring. Because different filler loading mode can be divided into bulk packing and structured packing.Because bulk packing structured packing than easy t

28、o install, low cost, bulk randomness location, but also the direction of the flow of solid particles is more flexible, improve the chances of gas-solid contact, and therefore more suitable for the production of bulk filler than structured packing. Applications in the FCC stripper within the bulk fil

29、ler inner-loop, as compared with the conventional stripper stripping efficiency increases, effectively reducing the extent of mixing of gas-solid in the back. Current research on bulk packing continues, but rather to study for fluidized bed remains to be further studied.3.3 Grille inner-loopTo solve

30、 the gas-solid back-mixing, bubbles merge and air contacts the catalyst becomes uneven ambassador and other issues, Luoyang Petrochemical Engineering Corporation developed a lattice within inner-loop fluidized bed, even it can be divided into several units bed, gas-solid after the exchange in which

31、to effectively reduce the extent of gas-solid back-mixing, to improve contact efficiency of gas-solid, effective control of the bubble and the installation of two lattice inner-loop in the regenerator dense phase region, bubbles significantly reduced, greatly reduced fluidized dead zone at the wall,

32、 and significantly improve the regeneration of the regenerator.Adding inner baffle inner-loop to reduce solids entrainment, inhibition slugging phenomenon; inner grill inner-loop can enhance the ability to break the bubble; while the inner filler inner-loop can increase its processing capacity and i

33、mprove the mass transfer efficiency. So the researchers combined these three inner-loop, has developed a modular inner fender filler inner-loop.Adding inner baffle inner-loop to reduce solids entrainment, inhibition slugging phenomenon; inner grill inner-loop can enhance the ability to break the bub

34、ble; while the inner filler inner-loop can increase its processing capacity and improve the mass transfer efficiency. So the researchers combined these three inner-loop, has developed a modular inner fender filler inner-loop.3.4 Vertical Sieve Tray inner-loopVertical Sieve Tray has obvious advantage

35、s received the attention of domestic and foreign experts, to carry out the research and development of vertical sieve. The new Vertical Sieve Tray has its processing capability, high mass transfer efficiency, there is a small voltage drop across it, and load capability, easy operation and many other advantages.It is due to the action of the cap, so in recent years for novel improved Vertical Sieve Tray almost all focused on improving the cap cover, the cap main types are S, C-type, rectangular, rectangular, etc. ladders. Vertical Sieve Tray Re