(620m) Production of Ethyl Alcohol From Excess Ethylene: A Systematic Approach for Conceptual Process Design

Abstract: Poster Session 10A07 Production of Ethyl Alcohol From Excess Ethylene: A Systematic Approach for Conceptual Process Design

Thomas Bisgaard, Kim B. Carlsen and Adam S. Kadhim

Department of Chemical and Biochemical Engineering, Technical University of Denmark, Kgs. Lyngby

Ethyl alcohol is one of the most important and used chemicals. Two common routes exist for the production: synthetic route typically based on petroleum feedstock and a fermentation route. The fermentation route comprises the majority of the produced ethyl alcohol. In this work, however,  we will focus on the synthetic method, which employs direct hydration of ethylene.

A conceptual process design of an ethyl alcohol producing plant is performed in a MSc-level course on Process Design at the Department of Chemical and Biochemical Engineering at DTU. In the designed process,  190 proof ethyl alcohol (azeotropic mixture) is produced from excess ethylene containing propylene and methane as impurities. The design work is based on a systematic  approach consisting of 12 tasks performed in a specified hierarchy. According to this 12-tasks design procedure,  information about the product and process is obtained in tasks 1-2. A preliminary process flowsheet is obtained in task 3 using a modified Douglas hierarchical process synthesis method. The next tasks  involves making design decisions and then further refining them in tasks 4-7 related to separation factors, reactor operating conditions, product purity, etc.. In tasks 4 mass balances is are performed while in tasks 6-7 energy balances are performed. All simulations are made with PRO/II. Tasks 8-9 make the sizing and economic valuation calculations. At this point, the base case design is obtained, which is then further refined and improved with respect to heat integration and process optimization (tasks 10-11). In the final task-12, the environmental impact of the process design is evaluated together with some of the key sustainability measures. In addition to PRO/II, the following software is used: ICAS (for property prediction, analysis) and ECON (cost and economic analysis). This design therefore covers all stages of conceptual design, starting from the consideration of qualitative aspects of the process flowsheet and preliminary calculations to detailed process simulations, equipment sizing, costing and an economic evaluation of the designed process.

The resulting design utilizes 75 million kg/year ethylene feed in order to obtain an ethyl alcohol production of 90.5 million kg/year. The total capital investment has been estimated to 43 million USD and the total product cost without depreciation to 58.5 million USD. Furthermore, computer aided economic analysis method has been applied to investigate the potential economic improvements. This analysis helps to define targets for improvement, which are then achieved through heat and mass integration as well as mathematical optimization.  In the final step, the environmental impact of the process is analyzed and key sustainability factors such as energy used per kg of product, water used per kg of product, etc., are also determined. A sizable reduction of the operating costs has been possible through heat integration and process optimization yielding a
20 % reduction in total capital investment and a 15 % reduction in product cost without depreciation.

The design project was carried out under the supervision of Professor Rafiqul Gani.