공업적으로 중요한 fixed bed, moving bed, fluidized bed 그리고 continuously stirred tank reactor등의 다분체계의 설계와 분석을 여기에 검토한다. 제1, 2, 3부에서 검토한 단일고체의 반응을 다분체계에 응용하는 절차를 예시하였다. 또한 최근에 개발된 다분체계의 반응을 서술하는데 있어 강력한 수학적 방법인 "population balance model"을 함께 소개한다. 이 방법이 앞으로 화학과 야금공정에서 일어나는 여러 가지 다분체계의 분석에 많은 응용이 되리라 믿는다.

The design and analysis of a multiparticle fluid-solid reaction system is discussed. The types of contacting devices discussed are fixed beds, moving beds, fluidized beds, and continuously stirred tank reactors. The analysis, however, can be extended to other multiparticle systems. It is shown how the analysis of the reaction of individual solid particles discussed in the previous parts of this review forms the basis for analyzing a multiparticle system combined with the reactor configuration, fluid flow, and the rate of supply of the fluid reactant.
Also in this article, a powerful mathematical technique called the "population balance model" for describing a reaction of a multisized particle system is introduced. It is believed that this recently developed technique will find many applications in the design and analysis of various chemical and extractive metallurgical processes involving particulate assemblages.