Agitated Reactors are most widely used reactors in our Chemical Process Industries. We can operate this reactor in batch, semi-batch and continuous mode. When we use this reactor in continuous mode is also know as CSTR or continuous stirred tank reactor. However, we use these reactors mostly in batch & semi-batch operations for the production of fine chemicals, APIs, specialty chemicals, etc.
Moreover, agitated reactors are most suitable for small scale production capacities and provide flexibility to produce multiple products in same setup. Apart from reaction operation we use agitated reactors for crystallization, evaporation, mixing, etc.
In this article we will go through the Process Data Sheet of Agitated Reactor or Vessel. We will try to understand various components of this PDS. So that you are able to provide correct and complete specifications for the vendor.
We can divide agitated reactor process data sheet in two sections, first is jacketed vessel specification and second agitator specification. So, to understand first section let us go through the below process data sheet format.
Table of Contents
Jacketed Vessel Specification
So, we can see in below data sheet, here we have provided all required specifications for the fabrication of a jacket vessel.
Top Header
Here you should put the logo and name of your organization. Vessel description, tag number and project name are very important during erection work. As, this helps the people at site for easy and errorfree identification of that vessel. Also, mention the type of vessel whether it is flanged or monobloc type.
Other details are document number, revision number which are important from documentation point of view. Apart from this, details of maker, checker and approver are important to trace the engineers involved in this project. Also, the information for which this PDS we are issuing is important like, it can be “Issued for Inquiry” or “Issued for Comments” etc.
Operating & Mechanical Data
In this section you need to mention operating and design data for the vessel and jacket/Limpet Coil. This information includes like, fluid details (i.e., composition), fluid density, operating pressure & temperature, design pressure & temperature. Apart from this we need to mention equivalent hydrotest or pneumatic test pressure for the vessel and jacket/Limpet Coil side. Moreover, we need to provide numbers of baffles required and its dimensions. As we need baffles to create better turbulency inside the vessel during agitation.
Other process parameter includes vessel diameter and TL-TL height or length. Here TL means tangent line point of the dish end. Provide the total volume and working volume for the vessel. As a thumb rule, we consider 80% working volume of the total vessel volume. Also, we should mention details for jacket/limpet coil dimension as well.
Various mechanical data comprises, corrosion allowance (around 1.6mm for MS and Nil for SS), insulation thickness & type. You need to mention thickness for shell, jacket and dish ends; however, fabricator can also calculate this based on your operating data.
Other mechanical data includes, empty and filled weight for the agitated reactor.
Other Codes and Standards
You need to mention the vessel design code like, ASME or GEP (Good Engineering Practices). Other than this you need to mention stress reliving requirement codes, if required. Also, details of joint efficiency and radiography should be provided. Joint efficiency for critical equipment should be 100%, while for other moderate and non-critical services it can be 85% and 70% respectively. Among these 70% is the lowest joint efficiency and in this case vessel thickness is minimum. This joint efficiency we consider for non-critical services.
Sketch of the Agitated Reactor
You should provide schematic drawing of the jacketed vessel. This information helps user to understand the geometry and installation details. The various information we provide in sketch includes vessel type, Jacked or limpet coiled, nozzles with location, support type, agitator type, etc.
Material of Construction (MOC)
In this section we provide the information regarding MOC of various part of the vessel. As you can see in sketch a vessel can be divided in different parts like Main Shell, Dish Ends, Nozzle Flanges, Nozzle Pipes, Support, Nuts & Bolts, Gaskets, etc.
Material of construction depends on the fluid corrosive properties, erosive nature for handling slurries & solid catalyst suspension, operating temperature and pressure. In chemical process industries you can find vessel MOC of Mild Steel, Stainless Steel, Inconel, Hastelloy etc. In case of non-metal construction MOC can be MS-Glass lined, rubber lined, PP/HDPE lined, out of this glass lined reactor most widely used in our industries.
We use material compatibility chart to find the suitable metallurgy for our vessel. Moreover, in special material situation we need to conduct coupon test, to find best compatible material.
Nozzle Schedule
Here we provide details for all the nozzles required in agitated reactor or vessel. Commonly in every agitated reactor we require, Inlet Nozzle, Outlet Nozzle, Vent Nozzle, Manhole (in case of large diameter vessel > 1.50 m), Dip pipe, Handhole, Drain point, thermowell nozzles, safety valve nozzle and pressure indicator nozzles. For jacket side there are utility inlet/outlet nozzles.
Other than this we require light glass & sight glass nozzles to see inside the reactor during operation. In nozzle details we provide the standards to follow (i.e., ASME/ANSI or BIS) for flange dimensions.
Moreover, we need to mention nozzle pipe schedule & thickness with flange ratings. Also, nozzle tag number and quantity of nozzles is there in the table.
Remarks
In this section we can provide miscellaneous information, which are common. You can see in above format there are sample comments for your reference. Based on your specific requirements this information can be customized. Whole purpose here is to provide all the general clarification to the fabricator or user.
So far, we discussed about jacketed reactor/vessel part. Now, let us look into the agitator part which is very important for the performance of the agitated reactor. In an agitated reactor, agitation creates turbulency and enhance mixing, mass transfer and heat transfer coefficients. Based on the process requirements we can select the type of agitator.
For glass lined reactors, you can float the inquires to following vendors.
Agitator types and their Utility
As we discussed agitator role is to provide turbulency inside the agitated reactor. Therefore, type of agitator selection depends on process requirement and viscosity of the fluid. Apart from this presence of suspended solid catalyst and gas feed also crucial for the agitator selection.
The agitator provides two types of mixing inside the vessel as below.
Radial Mixing – This type of mixing enhances the heat transfer coefficient for the reactor. We use this type of agitators, where we are looking for evaporation or cooling operation. In other words, we can say wherever better heat transfer coefficient is important for the process. To achieve this type of mixing pattern we can use straight blade turbines or anchor agitators.
Axial Mixing – To enhance mixing inside the reactor we use this type of agitators. This type of mixing patterns is good to increase mass transfer coefficients. Basically, this works just like a pump impeller inside the vessel. The examples of this type of agitators are pitched blade turbine, propellers, ribbon blade turbine, helix, etc.
Flow Patterns in the Agitated Reactor
To understand the flow pattern in agitated reactor you can refer below figure.
Data Required for Agitator Design
So, to design an efficient agitator we need to provide all the data in below specification sheet. However, below are the main required data for your reference.
Tank dimensions with dished end details – for this we have already discussed above in PDS of Jacketed Vessel. There all this information is available.
Process Specification – Specific gravity and viscosity of all reactants.
Mechanical Specification – You need to provide the mechanical details of vessel and agitator
Mixing requirement – Here you need to mention what we are mixing and why we are mixing? Like is it liquid-liquid, liquid-gas, liquid-solid or liquid-solid-gas system?
Brief description of Process – You need to provide brief description of the process, explaining critical for the efficient & safe operation of the equipment. This can include like heat of reaction, whether reaction is fast or slow, importance of the solid catalyst suspension, any polymerization possibility, scaling tendency of the fluid, etc.
Scale Of mixing – What level of mixing you looking for? At 1 to 10 scale turbine performance criteria for dynamic response, we can divide mixing into 4 levels. These are Low level, Medium Level, Medium High (Vigorous) and High (Violent).
For more information you can go through the below specification sheet for agitator.
Conclusion
Finally, I am sure this article will help a process engineers to prepare data sheet for the agitated reactor. This is a very important document to float the inquires for equipment fabrication.
As a good process engineer you should focus on the correctness and completeness of the process data sheet. This will eliminate the error in procurement and fabrication. Moreover, this PDS will ensure to meet designed performance and capacity of the plant.
Thanks for reading and looking for your feedback.