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Fabrizio Sarghini » 1.Introductory concepts about batch and continuous precess

Process classification

The food industry relied on large-scale continuous processes for a long period.

Initially, due to reduced investment costs, the production facility for a new product used to be either a batch process or a laboratory process produced on a larger scale.

As the economy of scale became a key factor, process engineering in general and food process industries focused on designing and developing continuous processes, at least for mass production goods.

Sauces, pasta, extrusion cooking products are some examples of this type of processing.

However, market and product diversification and specialty products, with an increased emphasis on and customer requirements for high quality and food security and traceability requirements, means that equal focus has switched to batch processing, and today, almost half of the processes in the food industry are batch processes.

Process classification (cont’d)

Industrial processes can be classified depending on the output of the process as:

  • Continuous processes.
  • Discrete processes.
  • Batch processes.

Continuous processes

In a continuous process, as suggested by the name, the flow of material or product is continuous.

Processing the materials in different equipment produces the products.

Each machine operates in a single steady state and performs a specific processing function.

Some examples of continuous processes are pasta production, tomato sauce and juice production, ice cream production, mayonnaise production, etc .

Continuous process (cont’d)

Continuous transformation of mass, energy and momentum.

The target is a product which is uniform in time.

The process is stopped only for maintenance (scheduled or not), cleaning, irregular working.

Continuous processes have the following advantages over a batch process:

  • Production of a narrow specification product, i.e., higher and consistent product quality.
  • Reduced manufacturing cost.
  • Improved asset utilization.
  • Reduced waste .

Discrete processes

In a discrete process, the output of the process appears one-by-one or in discrete quantities.

The products are produced in lots based on common raw materials and production history.

In a discrete process, a specified quantity of products moves as a unit or group of parts between workstations.

Some examples of discrete processes are assembly processes.

Process classification: batch process

Economic and technical factors could suggest that batch processes in some cases are more favorable than continuous processes:

  • Simple processing units like mixers and stirrers versus complex production systems.
  • Multipurpose units which may be used for several processing phases of the batch and could support multi-product manufacturing within the facility.
  • Batch manufacturing plants are comparatively more robust than a continuous plant.
  • Batch process manufacturing facility is easier to scale up depending on market demand and requirements.
  • Better control of process of a confined step.

Batch processes

Definition of Batch Processes

A batch is defined as:

  • The material that is produced by a single execution of a batch process, or
  • an entity that represents the production of a single material at any point of time in the process.
  • The term ‘batch’ means both the material produced by and during the process, and also an entity that represents the production of that material.
  • The term ‘batch’ can be considered a shortcut for “the production of a batch”.

Batch processes (cont’d)

Definition of Batch Process

A process is considered to be a batch process if the process consists of a sequence of one or more steps that must be performed in a defined order.

At the end of the sequence of steps, a finite quantity of the finished product is produced. The sequence is repeated to produce another batch of the product.

As a general definition, a batch process is a process that leads to the production of finite quantities of material by subjecting quantities of input raw materials to an ordered set of processing activities over a finite period of time using one or more pices of equipment.

Batch processes (cont’d)

Discrete quantities of raw materials or products are processed, and easier tracking of these discrete quantities of materials or products is allowed.

More than one type of product can be processed simultaneously, as long as the products are separated by the equipment layout.

Movement of discrete products from different processing areas.

Batch processes (cont’d)

Recipes (or processing instructions) associated with each load of raw material can be processed into product.

On the other hand ,a more complex logic associated with processing than in continuous processes is required.

Process layout must include normal steps that can fail, and thus in the event of a failure process must include special steps to be taken.

Batch processes (cont’d)

In a batch process, the output of the process appears in quantities of materials or lots.

Batch processes are neither continuous nor discrete, but have the characteristics of both.

Batch processes are usually performed in a sequential way.

Batch processes define a sub-class of sequential processes.

Batch processes generate a product but the sequential processes need not necessarily generate a product.

Some examples of batch processes are beverage processing, biotech products manufacturing, dairy processing, food processing, pharmaceutical formulations.

Batch processes (cont’d)

The nature of each step can be simple or complex, consisting of one or more unit operations, and generally a step is started when the previous one is completed.

There is frequent provision for non-normal exits to be taken because of operator intervention, equipment failure or the detection of hazardous conditions.

Depending on the recipe for the product being processed, a step may be bypassed for some products.

Quality control is sometimes required by automatic or operator approval before leaving one step and starting the next.

The processing operations for each step are generally under recipe control, but may be modified by operator override action.

Batch processes (cont’d)

Process structure

  • Single-path batch process.
  • Multi-path batch process.
  • Network batch process.

Batch processes (cont’d)

Process complexity
The matrix indicates the degree of complexity involved in automation of various combinations. The more complex a process, the more it requires allocation, arbitration and batch management solutions.

The higher the number of products manufactured by a process, the greater is the need for recipe management and batch management solutions.

A single-product, single-path batch plant is simple, while a multiproduct, network structured is the most complex combination.

Batch vs Continuous Processes

Batch vs Continuous Processes (cont’d)

Batch vs Continuous Processes (cont’d)

Batch vs Continuous Processes (cont’d)

Batch vs Continuous Processes (cont’d)

Batch vs Continuous Processes (cont’d)

Batch Process

Batch Process

I materiali di supporto della lezione

Mike Barker ,Jawahar Rawtani Practical Batch Process Management, ELSEVIER 2005

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