In response to the staggering environmental and energy problems associated with manufacturing facilities, the chemical and allied process industries have dedicated much attention and many resources to mitigating the detrimental impact on the environment, conserving resources, and reducing the intensity of energy usage. These efforts have gradually shifted from a unit‐based approach to a systems‐level paradigm. The past decade has seen significant industrial and academic efforts devoted to the development of holistic process design methodologies that target energy conservation and waste reduction from a system’s perspective. Implicit in the holistic approach, however, is the need to realize that changes in a unit or a stream often propagate throughout the process and can have significant effects on the operability and profitability of the process. Furthermore, the various process objectives (e.g. technical, economic, environmental, and safety) must be integrated and reconciled. These challenges call for the development and application of a systematic approach that transcends the specific circumstances of a process and views the environmental, energy, and resource‐conservation problems from a holistic perspective. This approach is called process integration (Parthasarathy and Dunn 2005; Smith 2016). It emphasizes the unity of the process and it is broadly divisible into the categories of mass integration and energy integration. Parthasarathy and Dunn (2005) provide an energy and heat exchange networks with a mini‐case‐study on heat exchange network, mass integration is briefly introduced, and the concept of mass integration is explored in detail.
9.6.1 Process Integration Technique Has Few Possible Applications
- A holistic approach to process design which emphasizes the unity of the process and considers the interactions between different unit operations from the outset, rather than optimizing them separately. This can also be called integrated process design or process synthesis (Smith 2016) describe the approach well. An important first step is often product design which develops the specification for the product to fulfill its required purpose.
- Pinch analysis, a technique for designing a process to minimize energy consumption and maximize heat recovery, also known as heat integration, energy integration, or pinch technology. The technique calculates thermodynamically attainable energy targets for a given process and identifies how to achieve them. A key insight is the pinch temperature, which is the most constrained point in the process. A detailed explanation of the techniques is given by Parthasarathy and Dunn (2005). This definition reflects the fact that the first major success for process integration was the thermal pinch analysis addressing energy problems. Other pinch analyses were developed for several applications such as mass‐exchange networks, water minimization, and material recycle. A very successful extension was “Hydrogen Pinch,” which was applied to refinery hydrogen management. This allowed refiners to minimize the capital and operating costs of hydrogen supply to meet ever stricter environmental regulations and also increase hydrotreater yields (Hallale 2001).
In the context of chemical engineering, process integration can be defined as a holistic approach to process design and optimization, which exploits the interactions between different units in order to employ resources effectively and minimize costs. Process integration is not limited to the design of new plants, but it also covers retrofit design (e.g. new units to be installed in an old plant) and the operation of existing systems. Hallale (2001) explains that with process integration, industries are making more money from their raw materials and capital assets while becoming cleaner and more sustainable.
The main advantage of process integration is to consider a system as a whole (i.e. integrated or holistic approach) in order to improve their design and/or operation. In contrast, an analytical approach would attempt to improve or optimize process units separately without necessarily taking advantage of potential interactions among them.
For instance, by using process integration techniques it might be possible to identify that a process can use the heat rejected by another unit and reduce the overall energy consumption, even if the units are not running at optimum conditions on their own. Such an opportunity would be missed with an analytical approach, as it would seek to optimize each unit, and thereafter it wouldn’t be possible to reuse the heat internally.
Typically, process integration techniques are employed at the beginning of a project (e.g. a new plant or the improvement of an existing one) to screen out promising options to optimize the design and/or operation of a process plant. Also it is often employed, in conjunction with simulation and mathematical optimization tools to identify opportunities in order to better integrate a system (new or existing) and reduce capital and/or operating costs.
Most process integration techniques employ Pinch analysis or Pinch tools to evaluate several processes as a whole system. Therefore, strictly speaking, both concepts are not the same, even if in certain contexts they are used interchangeably. The review by Hallale (2001) explains that in the future, several trends are to be expected in the field. In the future, it seems probable that the boundary between targets and design will be blurred and that these will be based on more structural information regarding the process network. Second, it is likely that we will see a much wider range of applications of process integration. There is still much work to be carried out in the area of separation, not only in complex distillation systems but also in mixed types of separation systems. This includes processes involving solids, such as flotation and crystallization. The use of process integration techniques for reactor design has seen rapid progress, but it is still in its early stages. Third, a new generation of software tools is expected. The emergence of commercial software for process integration is fundamental to its wider application in process design.
Leave a Reply