Conventional plug flow reactor The fact that the tank inlet is operating under high load limits the growth of most of the filamentous bacteria and enhances the sludge’s settle ability, providing that sufficient dissolved oxygen is maintained. step feed
Full Answer
How does a plug flow reactor work?
In a plug flow reactor, nutrients (and sometimes organisms) are introduced to the reactor continuously and move through the reactor as a “plug”. The system may be either contained (as in a water main, oil pipeline, or blood vessel) or open (as in a shower curtain, stream, or canyon seep).
Can plug-flow reactors be used for biological treatment of water demanding cells?
Despite offering a high rate of substrate conversion, plug-flow reactors are seldom suggested for biological treatment of water demanding cell growth because of inherent difficulties in providing continuous inoculum of cells as well as in maintaining desired pH and oxygen supply along the length of the reactor.
What are the practical applications of the plug flow model?
The plug flow model has many practical applications. One example is in the design of chemical reactors. Essentially no back mixing is assumed with "plugs" of fluid passing through the reactor. This results in differential equations that need to be integrated to find the reactor conversion and outlet temperatures.
What is plug flow reactor (PFR)?
The third general type of reactor is the Plug Flow Reactor (PFR). In a plug flow reactor, nutrients (and sometimes organisms) are introduced to the reactor continuously and move through the reactor as a “plug”.
Why do we use plug flow reactor?
Currently, plug flow reactors are used in the production of biodiesel and other biofuels with a recycle system [9]. The plug flow reactor is mostly preferred for bioenergy production because of its steady-state operation. In addition, the plug flow reactor does not require any agitation or baffling.
What is plug flow reactor in wastewater treatment?
A type of flow that occurs in tanks, basins, or reactors when a slug of water or wastewater moves through a tank without dispersing or mixing with the rest of the water or wastewater flowing through the tank.
Why is a PFR better than a CSTR?
At high fractional conversion values, the volume required for a CSTR increases rapidly compared the the volume of a PFR. If reactor volume is the only criterion for deciding the type of reactor to use, clearly PFRs are the optimal choice.
Which reactors are used for waste water treatment?
Types of Reactors in Wastewater TreatmentThe Activated Sludge Process. ... The Membrane Bioreactor (MBR) Process. ... The Biodiscs Sewage Treatment. ... Wastewater Treatment Biofilters. ... Trickling Filters in Wastewater Treatment. ... Moving Bed Biofilm Reactor (MBBR)
What is the difference between MFR and PFR?
PFR is the continuous type reactor and their is no axial mixing and it is segment of many batch reactor. MFR it is the reactor which has agitator feted and it also a continuous type. Batch reactor has input fed then the reaction occur and after o/p.
Where are plug flow reactors used in industry?
Plug flow reactors have a wide variety of applications in either gas or liquid phase systems. Common industrial uses of tubular reactors are in gasoline production, oil cracking, synthesis of ammonia from its elements, and the oxidation of sulfur dioxide to sulfur trioxide.
Why is PFR more efficient?
PFR always preferred here because of heterogeneous reactions, variable density systems , capacity to handle huge volumes , gas phases , higher conversion at the same throughput n space time and no moving part inside that makes high availability factor.
What is the difference between CSTR and plug flow reactor?
A PFR has a higher theoretical efficiency than a CSTR of the same volume. That is, given the same space-time (or residence time), a reaction will proceed to a higher percentage completion in a PFR than in a CSTR. This is not always true for reversible reactions.
What is the difference between plug and mixed flow reactor?
In plug flow, the concentration of reactant decreases progressively through the system; in mixed flow, the concentration drops immediately to a low value.
What are the advantages of SBR?
Advantages of SBRs are that equalization, primary clarification, biological treatment, and secondary clarification can be achieved in a single reactor vessel. These advantages can reduce the treatment area and cost.
What is meant by activated sludge?
The activated sludge is a process with high concentration of microorganisms, basically bacteria, protozoa and fungi, which are present as loose clumped mass of fine particles that are kept in suspension by stirring, with the aim of removing organic matter from wastewater.
What is SBR type STP?
Sequencing batch reactors (SBR) or sequential batch reactors are a type of activated sludge process for the treatment of wastewater. SBR reactors treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches.
What is a plug flow reactor?
In a plug flow reactor, nutrients (and sometimes organisms) are introduced to the reactor continuously and move through the reactor as a “plug”. The system may be either contained (as in a water main, oil pipeline, or blood vessel) or open (as in a shower curtain, stream, ...
Why do the constituents of a reactor change as the medium flows along the long axis?
Due to the metabolic activity of the organisms in the biofilm, constituents of the reactor will change as medium flows along the long axis due to consumption of nutrients and elimination of waste products. The nutritional conditions at any given point along this long axis should, however, remain constant in a stable reactor.
What is flow cell?
The flow cell has provision for introducing additional organisms, biocides, nutrients or dyes while the cell is in operation. If one wishes to observe biofilms growing in as close to a natural environment as possible, this is the exercise for you.
What is the process of liquid passing through a porous matrix called?
Sometimes liquid passes in a plug flow mode through a porous matrix such as soil, sand or porous rock. Biofilms initiated in such a matrix can be used to slow the rate of flow of contaminants through the matrix in what is called a biobarrier.
Why do we use distillation in a chemical reactor?
For this reason a separation process, such as distillation, often follows a chemical reactor in order to separate any remaining reagents or byproducts from the desired product. These reagents may sometimes be reused at the beginning of the process, such as in the Haber process.
What happens to the rate of reaction as the reactants are consumed?
The rate of reaction decreases as the reactants are consumed until the point where the system reaches dynamic equilibrium (no net reaction, or change in chemical species occurs). The equilibrium point for most systems is less than 100% complete.
Is PFR higher than CSTR?
A PFR has a higher theoretical efficiency than a CSTR of the same volume. That is, given the same space-time (or residence time), a reaction will proceed to a higher percentage completion in a PFR than in a CSTR. This is not always true for reversible reactions.
Can a chemical engineer separate partially reacted mixtures?
In some cases, very large reactors would be necessary to approach equilibrium, and chemical engineers may choose to separate the partially reacted mixture and recycle the leftover reactants. Under laminar flow conditions, the assumption of plug flow is highly inaccurate, as the fluid traveling through the center of the tube moves much faster ...
Does PFR have axial mixing?
· The idealized PFR model assumes no axial mixing: any element of fluid traveling through the reactor doesn't mix with fluid upstream or downstream from it, as implied by the term "plug flow".
PFR modeling
The stationary PFR is governed by ordinary differential equations, the solution for which can be calculated providing that appropriate boundary conditions are known.
Operation and uses
PFRs are used to model the chemical transformation of compounds as they are transported in systems resembling "pipes". The "pipe" can represent a variety of engineered or natural conduits through which liquids or gases flow. (e.g. rivers, pipelines, regions between two mountains, etc.)
Residence-time distribution
The residence-time distribution (RTD) of a reactor is a characteristic of the mixing that occurs in the chemical reactor. There is no axial mixing in a plug-flow reactor, and this omission is reflected in the RTD which is exhibited by this class of reactors.
What is plug flow analysis?
The plug flow analysis demonstrates the potential advantage of running product-inhibited systems with patterns. More importantly, it validates the value of the novel layered patterns proposed in this work. One concern with this analysis is that it assumes a discontinuous θ profile in going from one layer to the next. Since this is an unrealistic idealization, it is necessary to assess the extent to which the layered pattern's advantages are compromised by the smoothing of the θ profile by axial heat dispersion. This is done by conducting simulations based on a mixing cell model containing a specific mechanism for the backflow of heat between cells. The model equations and information about the solution strategy are presented in an earlier paper [1 ].
What is the usual configuration of a reactor?
The usual configuration is an essentially constant temperature of the heat transfer medium down the length of the reactor. In systems requiring cooling at fairly high temperatures, steam is generated on the shell side of the reactor to remove heat. The steam temperature is the same at any axial position.
Why does heat transfer medium flow through jacket?
The heat transfer medium must flow through the jacket in excess to keep its temperature unaffected by the heat of reaction. Plug flow is an idealized flow of fluids in which all particles in a given cross-section have identical velocity and direction of motion.
Can a tubular reactor be empty?
The tubular reactor can be an empty vessel if no catalyst is used. Where a solid catalyst is required, the vessel is packed with catalyst either in a bed or inside tubes. In this instance, the dynamic behavior is significantly affected by the presence of catalyst inside the reactor.
What is biofiltration in water treatment?
Biofiltration is a wastewater treatment process to purify water from sewage. The biofilters contain a medium grain filter through sand or carbon. The biofilter breaks down nitrogen, phosphorus compounds and nutrients in waste. This method of purification also captures other contaminants in the sewage and organic carbon molecules.
What is activated sludge treatment?
The activated sludge treatment process involves an aeration tank with air injected into the liquid, a settling tank that supports the sedimentation of water by separating the sludge from clear water treated in this manner, and a treatment of nitrogenous matter or a phosphate to ensure there is no dissolved oxygen remaining.
What is MBR in wastewater treatment?
The Membrane Bioreactor (MBR) Process. Types of reactors in wastewater treatment , such as with the MBR, may produce higher quality water that urban communities may reclaim for irrigation purposes. This bioreactor may also help a city upgrade an older treatment plant that cannot use outdated equipment. The MBR may work in conjunction ...
Continuous-Flow Stirred Tank Reactor (CFSTR) or Completely-Mix Reactor
The reactants entering the reactor (which are dispersed immediately) and the products flowing out from the reactor are considered as continuous.
Completely Mix Batch Reactor
in a closed system where no flow is added or allowed to leave during the design detention tim
Plug Flow Reactor or Tubular-Flow
Fluid particles pass through the tank and are discharge in the same sequence in which they enter.
Fluidized Bed Reactor
is filled with the packing material that expands and gets fluidized when wastewater moves upward in the reactor.
