Process integration in chemical manufacturing & engineering

A popular myth most people aware of Process Integration is that they compare it with the design of heat exchanger networks. As a fact, the design of heat exchanger networks is a part of Process Integration, the entire spectrum of process integration is however far wider.

The sole objective of Process Integration is the design & optimization of integrated chemical manufacturing systems. The execution of Process Integration initiates with the selection of series of processing steps & their interconnection to produce a streamlined manufacturing system which transforms raw materials into desired products.

Process Integration does not stop with the synthesis of process flow sheets for individual processes. Individual processes typically operate as part of an integrated manufacturing unit consisting of a number of processes controlled by a common utility system. Linking processes to the common utility system creates interactions between the different processes through the utility system. If understood properly, these interactions can be used to maximize the performance of the site as a whole. Moreover, to enhance & ensure that maximum efficiency is utilized, the steps taken by individual processes on a site to exchange materials can be customized.

Chemical processing industry is growing alarmingly & is becoming an adherent part of sustainable industrial activity. This means making use of raw materials as efficiently & as economical and practical in order to:

  • Prevent the production of waste than can be harmful to environment
  • Preserve the source of raw materials as much as possible

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Chemical processing tips:

  • Energy should be used efficiently, not only to reduce costs, but to prevent the buildup of carbon dioxide in the atmosphere from burning fossil fuels and to preserve the reserves of fossil fuels.
  • Water should be consumed in sustainable quantities that does not cause any deterioration in the quality of the water source or the long-term quantity of the reserves.
  • Aqueous and atmospheric emissions must not be environmental harmful and solid waste to land film must be avoided.
  • Finally, all aspects of industrial activity must feature good health and safety practices.

Process integration is more than just pinch technology & design of heat exchanger networks. It has far wider scope and touches every area of process design. Switched-on industries are making more money from their raw materials & capital assets while becoming cleaner & more sustainable.

Trends in process integration:

Current methods still attempt wherever possible to use a 2-step approach to design. Initially, performance targets are set to scope & screen options. Once these important options have been screened, a design method is used to achieve targets.

In the future, there’s a high probability that the boundary between targets & design will be blurred & these will be based on more structural data regarding process networks.

It is also more likely that we get to see a wider range of applications being used for process integration. There is still immense work to be carried out in the area of separation; not only in complex distillation systems, but also in mixed type of separation systems. The use of process integration techniques for reactor design has seen rapid progress, but still there’s plenty to discover. There’s also a huge demand for process integration being applied to process operations keeping in mind safety & control.

The next trend of software tools for process integration is going to be a big wave in the chemical processing industry. While simulation tools are becoming quite mature & well developed, process integration software so far is just in its infancy stage. Developments in software leading to open-architecture will allow process integration software to interact online with simulation software to access physical property data & simulation models.

Distillation column design & optimization

Distillation is a process that separates two or more components into an overhead distillate and bottoms. The bottom product is almost exclusively liquid, while the distillate may be liquid or a vapor or both.

The separation process requires three things.

  • First, a second phase must be formed so that both liquid and vapor phases are present and can contact each other on each stage within a separation column.
  • Secondly, the components have different volatilities so that they will partition between the two phases to different extent.
  • Lastly, the two phases can be separated by gravity or other mechanical means.

Distillation differs from absorption and stripping in that the second phase is created by thermal means

Distillation Flow:

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The distillation column consists of:

  • 1 feed stream – which consistsof a mole percent of the light component, Zf.
  • 2 product streams – exiting the topwhich has a composition of Xd of the light component. The product stream leaving the bottomcontains a composition of Xb of the light component.

The column is broken in two sections:

  • The top section referred to as the rectifying section – which passes through a total condenser to condense all of the vapor distillate to liquid.
  • The bottom section isknown as the stripping section – which uses a partial reboiler to allow for the input of energy into our column.

Applications of Distillation:

  • Distillation is the least expensive means of separating mixtures of liquids.
  • If relative volatilities of components is less than 1.1, distillation becomes very expensive & extraction or reactive distillation should be considered.

What do successful distillation scale-up projects have in common? Project managers

Distillation column designmust understand and determine five key design elements for project success. Cost, chemical interactions and equipment needs change in a non-linear fashion as increased output is required.

STEPS INVOLVED IN COLUMN DESIGN:

  • SECTION 1:

    Graphical Determination of a Distillation Column Design

    Step 1. Determine Process Operation Variables
    Step 2. Determine the Minimum Reflux Ratio
    Step 3. Choose Actual Reflux Ratio
    Step 4. Determine the Minimum Number of Trays
    Step 5. Determine Actual Number of Trays
    Step 6. Principal Dimensions of the Column (Diameter/Height)

  • SECTION 2:

    Analytically determining the specifications for a distillation column

    Step 1. Determine Process Operation Variables
    Step 2. Determine the Minimum Reflux Ratio
    Step 3. Choose Theoretical Reflux Ratio
    Step 4. Determine Theoretical Number of Trays
    Step 5. Determine Actual Number of Trays
    Step 6. Principal Dimensions of the Column (Diameter/Height)

  • Section 3:

    Determining the Cost of Column and Components

    Step 1. Cost of Column
    Step 2. Cost of the Reboiler
    Step 3. Cost of Condenser
    Step 4. Total Cost of Column

Qualified engineers should consider the following critical steps for distillation column design:

  • Vapor-Liquid Equilibrium
  • Column Operating Objectives
  • Operating Pressure
  • R/Dmin and Nminand Feed stage estimation
  • Diameter and Height of the Column

Vapor-Liquid Equilibrium:

The starting point upon of all column design is on the basis of accurately determining the relative volatility of the key components to be separated. Using a mass and energy balance simulation program, the user must set up the basis of the simulation by selecting an appropriate fluid package and the components present in the feed.

Activity coefficients, estimated by the program or provided by the user, are used to relate non-ideal component interactions.

Column operating objectives:

Column operating objectives are defined by a primary product composition and an optimal recovery of the product from the waste, recycle or less important by-product stream. These specifications should be in terms of the heavy key impurity in the top stream and the light key impurity in the bottom stream.

Operating Pressure:

Once the top and bottom stream compositions are specified, the dew point of the top stream and the boiling point of the bottom stream may be determined at various pressures. An operating pressure should be selected that allows acceptable temperature differences between available utilities because the overhead vapor must be condensed and the bottom liquid reboiled.

If possible, atmospheric or pressure operation of the column is preferred to avoid requiring a vacuum system. Another consideration is also to use component heat sensitivity, which may require lower pressure operation to avoid fouling, product discoloration or decomposition. Often, the relative volatility is also improved at lower pressures.

R/Dmin&Nmin and Feed Stage Estimation:

Using the simulation program, shortcut procedures based upon total reflux operation allow the minimum reflux ratio (R/Dmin) and minimum number of ideal separation stages (Nmin) to be determined.

Using an actual reflux ratio of 1.2 times the minimum reflux ratio will allow an optimal number of stages to be estimated as well as an appropriate feed stage.

Diameter & Height of the column:

At this point, the distillation process is well defined, leaving the column diameter and height to be determined.

The column diameter is chosen to provide an acceptable superficial vapor velocity, or “Fs factor”. This is defined as vapor velocity (ft/sec) times square root of vapor density (lb/ft3), and liquid loading defined as volumetric flow rate (gal/min), divided by the cross sectional area of the column (ft2).

The column internals can be chosen as either trays or packing. Trayed columns must avoid flooding, weeping and down comer backup. Packed columns must avoid flooding, minimum surface wetting and mal-distribution. Table 1 provides a range of typical parameter values for various types of trays.

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Detailed engineering for piping systems

Detailed engineering are studies which creates a full defined scope of work for every aspect of project development. It is a multi-step process which includes conceptualization, research, feasibility analogy, establishing design requirements, preliminary design plans, detailed designing, production planning and tool design and finally moving towards actual production. Detail engineering studies are a key component for every project development across Mining, Infrastructure, energy, oil&gas sectors.

Detailed engineering companies have the best technical experts & a wide range of experience across various industries to carry out the tasks of project management at the maximum precision level.
Piping engineering is a specialised branch of detailed engineering dealing with design & layouts of piping network along with the Equipments in a process plant.

The images shown form a fully fledged blue print of a plant & are used for plant construction at site. The most important factors to be considered are:

  • Process requirements
  • Process safety
  • Operability
  • Maintenance
  • Compliance with statutory requirements & economy

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Piping detailed engineering process:

‘Piping’ includes the utility of components such as pipe, valves and fittings. A piping designer or a piping engineering company should be thoroughly acquainted with the equipment, instrumentation and related disciplines. A team of piping detailed engineering consists of Engineers, designers and construction personnel who get together to develop and design piping and instrumentation diagrams also known as P&ID (Process & Instrumentation Diagrams).

However, the process doesn’t stop there, they also make equipment plot plans, define the piping arrangements and make fabrication drawings.
A piping engineering company performs the following processes:

  1. Preparation of plot plan, equipment layouts piping studies, piping specification
  2. Review of process package
  3. Giving inputs to civil, vessel, electrical / instrumentation groups for various purposes

A piping engineering company ideally goes through the following plan of action to initiate the project:

  • Preparation of piping layouts, isometrics, support Drawings
  • Stress analysis
  • Procurement assistance
  • Preparation of drawings for statutory approvals
  • Preview of vendor drawings
  • Coordination with various engineering groups & site

And finally ends with completion & commissioning of plant.

Detail piping engineering: What does it involve?

Detail piping engineering consists of an engineering report for the use of various types of pipes and pumps with pressure drop calculations. It also consists of:

  • Pipes and pumps specifications
  • equipment selection and size
  • instrumentation and process control
  • other piping components such as valves, fittings, piping hangers and supports

Detail piping engineering : How helpful it is to you?

Detail piping engineering focuses on 3 primary pointers:

  • how your piping systems should work;
  • what materials must be used to make the piping structure for the engineering project;
  • select the type of material to be used for certain pipes and piping components

Detailed engineering helps in drafting fabrication and construction specifications. It also helps piping consulting engineers to execute a thermal analysis, vibrating analysis and stress analysis for sound piping layout and implementation.