**4. Path forward**

Nowadays integration is moving away from unit operations and focuses on phenomena; like reaction, heat and mass transfer that occur within a single piece of equipment. Future systematic techniques for process integration will not only explore for integration between units but also integration within units.

Process sites produce useful products in one or more process units and use a centralized utility system to satisfy the heat and power demands of the process

units. Improvements in process technology, heat recovery philosophy and enhanced throughput are a number of the various reasons why the process changes must be implemented in an exceedingly site. Because of the interactions that exist between the various subsystems (e.g. processes, heat exchanger networks and utility systems), a change in one has a knock-on effect on the other subsystems. Many of the concepts and methods developed within the past for grassroots design, operational management, retrofit and debottlenecking scenarios, have focused on utility systems and process units independently. A clear strategy and systematic approach therefore must be developed to integrate all processes and utility systems and determine the synergies among them. Developing an efficient design of energy systems (utility system) requires an honest understanding of every subsystem in compass different processes. An effective design method is one that integrates the various subsystems within the site and captures the advantages instituted on interactions between them. Another element which needs attention is that the energy available finally after all integration i.e. energy which could not be employed in the present form and will be utilized through energy recovery technologies to the form energy which is required within the site. Physical insights and graphical methods of research is accustomed to study these interactions between the various parameters within the site and estimate the impact of process changes on site targets. However, as they do not consider the prevailing constraints within the site, they are less rigorous compared to mathematical programming techniques.

The approach (**Figure 7**) are going to be very effective in achieving energy efficient facility design because it will unify all processes, utilities, heat recovery and waste energy utilization to come up with targets and lay the inspiration to capture direct/indirect/hybrid integration among the plants. The resultant designs are going to be optimized for the full facility as even the plot plan is going to be optimized from direct and indirect integration perspective. Moreover, the retrofit-ability aspects of the design are going to be also covered within the approach, the resultant design will not only energy efficient today but easily modified as per trade-off to stay energy

#### **Figure 7.**

*Approach to facility design via integrated process-recovery-utility systems.*

### *Sustainable Energy Efficient Industrial Facility Design DOI: http://dx.doi.org/10.5772/intechopen.108829*

efficient throughout its life cycle. Because it is extension to the Pinch approach it has all its benefits and further improvement by unifying all facility design, low-grade energy recovery and utility synthesis. It's very difficult to magically establish such a global solution to figure from scratch. First, there should be the fundamental ingredients in situ, namely the desire of site-wide plants to participate and second proper tools and insights to conduct the analysis. These basic ingredients can then be enhanced and improved upon, with correct support structure in situ. The key to developing a successful sustainable energy efficient design is to determine the best integration among different plants and its utility system. Specifically, it's the material and energy flows relationship among the various plants which allow establishing optimal linkage to method a fruitful inter-dynamic structure. The other element is that it also looks to the application of energy technologies to the facility which starts with the quantification of the available waste energy that will not be utilized for integration during its life-time.

The method should be consisting of the holistic approach for total site targeting supported on the pinch technology accompanied by mathematical programming techniques, which is that the most generally used, where it allows waste heat from processes to be used as a source of heat in other processes. The waste heat sources are converted to steam, and then passed to processes that are in an exceedingly heat deficit condition via steam system infrastructure. To spot the external heating and cooling requirements of a group of individual plants from the central utility system, the temperature/enthalpy data from individual plants are first required to be extracted from the plant after the thermal integration of its hot streams to be cooled and cold streams to be heated using individual plant' grand composite curve. These grand composite curves define each plant' thermal heat deficiency and thermal heat surplus after intra-plant heat integration. The collection of grand composite curves of the whole site are then accustomed graphically add all thermal deficiencies to draw the entire site heating demand curve, and add all thermal surpluses to draw the entire site cooling demand curves. Such two curves are superimposed on one graph with the present and/or suggested steam generation levels and steam supplying levels to search out the minimum total site external energy utilities requirement and naturally best indirect inter-plants thermal integration, using the site steam system. During this method, intra-integration is completed first, which implies only waste heat of one plant is shared with other plants' members (which is not proactive form of cooperation). In this method the direct integration among adjacent plants, even using steam as a buffer, is not systematically addressed, where plant A, for example, with a surplus heat shall generate steam from its hot streams after its integration with its cold streams and send it first to the central utility and then the central utility sends it back to plant B leading to energy quality degradation and potential for mismatch between supply and demand. In this method, the mismatch within the number of steam levels required by the site users' generation and utilization leads to energy loss with very high possibility [12, 13].

The worldwide commercial software for transitioning industrial complexes to integrated-processes-utility-energy recovery facility does not exist and even the software for planning synthesis/design of the new ones for energy efficiency optimization do not seems to be much. The current state-of-art methods focus only on indirect integration using steam, after all for obvious reasons.

In brief, a mathematical programming formulation-based software is solved successively to enumerate all possible combinations of solutions ranked from best objective function value to least for every "user-selection" type of plants' integration

#### **Figure 8.**

*Future methodology to achieve energy efficient facility design.*

(membership in an alliance to avoid wasting energy) to spot the plants for inter-plants integration and also the ones for intra-only integration together with waste energy utilization technologies as shown in **Figure 8**. This may give an energy efficient design for a given economic trade-off and also has capability to optimize facility plot-plan for better integration opportunities but nevertheless it must be developed to be capable of life-time retrofit-ability. This needs solutions to be generated for all future economic trade-off supported on capital and energy costs forecasts, these solutions shall be compiled together to urge a design which can be modified from initial to final design with none hindrance. Provisions shall be provided for all the longer-term future modifications within the current design to form it a "Sustainable Energy Efficient Facility Design". The end result of the analysis is going to be highly integrated design as shown in **Figure 9** which is retrofit-able throughout its lifecycle and incorporated waste energy utilization technologies.
