Batch Reactor Optical High Precision Components by Hellma in the European Columbus Space Laboratory The batch reactor is used for researching crystal growth in weightless conditions. In this environment, the structure and function of biological macromolecules (Proteins) can be investigated particularly well. In order to guarantee perfect measurements the batch reactor is manufactured using synthetic quartz glass. High-grade polished components were connected to a monolithic quartz component using thermal bonding technology without using additional components. The demands made on technology, precision and tolerances are extremely high. In order to improve signal yield during the measuring process the surfaces were high-quality and nonreflective. The results of the experiments are directly channelled into biological and medical research to improve understanding of protein synthesis as well as gaining an important insight into fighting infections and other illnesses. The batch reactors form part of a so-called Protein Crystallisation Diagnostics Facility (PCDF) and were taken on 7th February 2008 to the International Space Station ISS on the 24th launch of the NASA Space Shuttle Atlantis.
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Batch Reactor
Optical High Precision Components by Hellma in the European Columbus Space Laboratory
The batch reactor is used for researching crystal growth in weightless conditions. In this environment, the
structure and function of biological macromolecules (Proteins) can be investigated particularly well. In order
to guarantee perfect measurements the batch reactor is manufactured using synthetic quartz glass. High-
grade polished components were connected to a monolithic quartz component using thermal bonding
technology without using additional components. The demands made on technology, precision and
tolerances are extremely high. In order to improve signal yield during the measuring process the surfaces
were high-quality and nonreflective. The results of the experiments are directly channelled into biological
and medical research to improve understanding of protein synthesis as well as gaining an important insight
into fighting infections and other illnesses. The batch reactors form part of a so-called Protein Crystallisation
Diagnostics Facility (PCDF) and were taken on 7th February 2008 to the International Space Station ISS on
the 24th launch of the NASA Space Shuttle Atlantis.
Batch Reactors
Type of Reactor Characteristics
Simple Batch Reactor is charged via two holes in the top of the tank; while reaction is carried out, nothing else is put in or taken out until the reaction is done; tank easily heated or cooled by jacket
Kinds of Phases Present
Usage Advantages Disadvantages
1. Gas phase
2. Liquid phase
3. Liquid Solid
1. Small scale production
2. Intermediate or one shot production
3. Pharmaceutical
4. Fermentation
1. High conversion per unit volume for one pass
2. Flexibility of operation-same reactor can produce one product one time and a different product the
1. High operating cost
2. Product quality more variable than with continuous operation
The plug flow reactor (PFR) model is used to describe chemical reactions in continuous, flowing
systems. The PFR model is used to predict the behaviour of chemical reactors, so that key reactor
variables, such as the dimensions of the reactor, can be estimated. PFR's are also sometimes called
Continuous Tubular Reactors (CTR's).
Schematic diagram of a Plug Flow Reactor (PFR)
Fluid going through a PFR may be modeled as flowing through the reactor as a series of infinitely thin
coherent "plugs", each with a uniform composition, traveling in the axial direction of the reactor, with each
plug having a different composition from the ones before and after it. The key assumption is that as a plug
flows through a PFR, the fluid is perfectly mixed in the radial direction but not in the axial direction
(forwards or backwards). Each plug of differential volume is considered as a separate entity, effectively an
infinitesimally small batch reactor, limiting to zero volume. As it flows down the tubular PFR, the residence time (τ) of the plug is a function of its position in the reactor. In the ideal PFR, the residence time
distribution is therefore a Dirac delta function with a value equal to τ.
PFR modeling
PFR are frequently referred to as piston flow reactors, or sometimes as continuous tubular reactors. They
are governed by ordinary differential equations, the solution for which can be calculated providing that
appropriate boundary conditions are known.
The PFR model works well for many fluids: liquids, gases, and slurries. Although turbulent flow and axial
diffusion cause a degree of mixing in the axial direction in real reactors, the PFR model is appropriate
when these effects are sufficiently small that they can be ignored.
When linear velocity, u, and molar flow rate relationships, Fi, and ,
are applied to Equation 1 the mass balance on i becomes
2. . [1]
When like terms are canceled and the limit dx → 0 is applied to Equation 2 the mass balance on
species i becomes
3. , [1]
where Ci(x) is the molar concentration of species i at position x, At the cross-sectional area of the tubular reactor, dx the differential thickness of fluid plug, and νi stoichiometric coefficient. The reaction rate, r, can
be figured by using the Arrhenius temperature dependence. Generally, as the temperature increases so does the rate at which the reaction occurs. Residence time, τ, is the average amount of time a discrete
A fluidized-bed reactor is a combination of the two most common, packed-bed and stirred tank, continuous flow reactors. It is very important to chemical engineering because of its excellent heat and mass transfer characteristics. The fluidized-bed reactor can be seen below:
In a fluidized-bed reactor, the substrate is passed upward through the immobilized enzyme bed at a high enough velocity to lift the particles. However, the velocity must not be so high that the enzymes are swept away from the reactor entirely. This causes some mixing, more than the piston-flow model in the packed-bed reactor, but complete mixing as in the CSTR model. This type of reactor is ideal for highly exothermic reactions because it eliminates local hot-spots, due to its mass and heat transfer characteristics mentioned before. It is most often applied in immobilized-enzyme catalysis where viscous, particulate substrates are to be handled.
Semibatch Reactors
Semibatch Reactors
The reactant that starts in the reactor is always the limiting reactant.
Three Forms of the Mole Balance Applied to Semibatch Reactors:
V = Vo + vo*t V = Vo + vo*t V = Vo + vo*tVo = 100 Vo = 100 Vo = 100vo = 2 vo = 2 vo = 2Nao = 100 Fbo = 5 Fbo = 5Fbo = 5 Nao = 100 Ca = Na/VNbi = 0 Cbo = Fbo/vo Cb = Nb/Vk = 0.1 k = 0.01 k = 0.01
Na = Ca*V
X = (Nao-Na)/Nao
Semi batch reactors or fed batch reactors
The semi batch reactor is similar to the batch reactor but has the additional feature of
continuous addition or removal of one or more components / streams. In addition to better
yields and selectivity, gradual addition or removal assists in controlling temperature
particularly when the net reaction is highly exothermic. Thus, use of a semi batch reactor
intrinsically permits more stable and safer operation than in a batch operation. Fed batch
reactors are rarely used in waste water treatment units.