Structure and Synthesis of Process Flow Diagrams

ENCH 430April 19, 2023

By: Michael Hickey

Outline

Introduction Hierarchy of Design Process Batch vs. Continuous Process Input – Output Structure of the Process Recycle Structure of the Process Energy Recovery System Conclusion

Introduction

Similar process for every path. Provide framework to generate

alternate Process Flow Diagrams (PFD)

Important decision of which chemical synthesis or route for desired product.

Hierarchy of Design Process

1. Decide whether the process will be batch or continuous.

2. Identify the input – output structure of the process.3. Identify and define the recycle structure process.4. Identify and design the general structure of

separation5. Identify and design the heat-exchanger network or

process energy recovery system.

Batch vs. Continuous Process

Semi-Batch: Operates Continuously, receives material in batch.

Batch: fixed quantity of product is produced in a given time.

Continuous: Feed is continuously fed to a series of equipment.

Advantages and disadvantages listed in Table 2.1

Input – Output Structure

Process Concept Diagram:

Input – Output Structure

Input – Output Structure of PFD:

Input – Output Structure

Generic Block Flow Process Diagram:

Input – Output Structure

Information Determined Using Input - Output Diagrams:

Basic economic analysis of profit margin. The chemical components that enter with the feed

and leave with the product. All the reactions that take place, wanted or

unwanted. Better approaches Often 2 or more different chemical paths

Recycle Structure of the Process

Efficiency of Raw Material Usage: Single – Pass Conversion = reactant consumed in

process / reactant fed to reactor

Overall Conversion = reactant consumed in process / reactant fed to the process

Yield = moles or reactant to produce desired product / moles of limiting reactant reacted

Recycle Structure of the Process

3 Ways to Recycle in Continuous Process Separate and Purify unreacted feed material from

products and recycle.

Recycle feed and product together with a purge stream.

Recycle feed and product together without a purge stream.

Energy Recovery System

Main Objective: Optimize energy that a process exchanges with utilities.

Utility usage can be decreased by exchanging energy between process streams. Ex. Heat Exchanger.