Heat integrated processes

Linnhoff, B., and Senior, P., Energy Targets for Better Heat Integration, Process... 

Two emerging trends endorse the concept of heat-integrated processes first, the production of basic chemicals is moved close to oil and gas wells where crude oil or natural gas is processed in large stand-alone units [1]. Second, fuel cell systems require on-site and on-demand hydrogen production from primary fuels (i.e., natural gas, liquid hydrocarbons or alcohols) [2]. Net heat generation in these processes is equivalent to raw material and energy loss, and is therefore undesirable. 

While many publications in the field of heat-integrated processes focus on specific processes such as dehydrogenation of paraffins or hydrogen production [3-5], this chapter is more focused on general conceptual trends in process and apparatus design. 

The intended purpose of heat-integrated processes for endothermic reactions is illustrated by the example of methane steam reforming for hydrogen generation, which is of high practical relevance [6] and features typical characteristics of the considered process class. The reaction is given by the following stoichiometric equation ... 

Fig. 1.2. Schematic flow configurations of heat-integrated processes for coupling endothermic and exothermic reactions, (a) Countercurrent flow of process streams, (b) Cocurrent flow of the process streams in the reactor stages and heat recovery in separate circuits.

Fig. 1.3. The effect of heat exchanger performance, NTU, and heat capacity ratio, h, on the normalized heat loss for heat-integrated processes in (a) countercurrent and (b) counter-cocurrent flow configuration.

The activities of heat-integrated processes with recuperative heat exchange are mainly devoted to the conversion of primary fuels (hydrocarbons or alcohols) to hydrogen, with few exceptions - for example, investigations on the dehydrogenation of light alkanes in Schmidt s group [3]. The practical relevance and vitality of... 

In the present work a new developed heat integrated hybrid pervaporation distillation process is modeled and experimental studies are carried out to analyze the effect of the heat integration in the process. With the results of the experiments, the model is validated and a comparison between industrial scale non heat integrated and heat integrated processes is done. As a result, three main advantages are presented in the approach a) reduction of the necessary external energy supply into the process, b) improvement in the pervaporation separation performance and c) reduction in the necessary membrane surface. 

Repeat step 1 for the heat-integrated process. You may wish... 

A chemical process uses physical and/or chemical operations to transform feed materials into products of different composition. Table 9,1 lists the types of operations that are most widely used. Depending on the production rate and the operations used, the process is conducted batchwise, continuously, or cyclically. A continuous, heat-integrated process that illustrates several of the operations in Table 91 is shown in Figure 91. where benzene and a mixture of xylene isomers are produced by the disproportionation of toluene. The heart of the process is a fixed-bed catalytic reactor, R-1, where the main chemical change is the reaction... 

The heat-integrated process provides an excellent example of the power and usefidness of dynamic simulation of distillation column systems. Alternative control structures can be easily and quickly evaluated. 

Base case with separate processes (MW) Mass and heat integrated processes (MW) Integration with existing site (MW)... 

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