A MATHEMATICAL OPTIMIZATION MODEL FOR CHEMICAL PRODUCTION AT SAUDI-ARABIA FERTILIZER COMPANY

This paper develops a mathematical economic optimization model for chemical production at Saudi Arabian Fertilizer Company (SAFCO) for two of their major products, ammonia and urea.The amount of ammonia and urea produced is determined by the product reactor setting.A reactor setting is determined by a set of operating parameters, such as raw material feed rate, reactor air flow velocity, and pressure.The model selects the minimum cost operating strategy while meeting a given production target.A zero-one integer programming model is developed for each product.The relevant data for the model are obtained, and then the model is solved.The results of the model showed substantial savings per year in both ammonia and urea plants.A systmatic sensitivity analysis is conducted on the optimal solutions of the model.It is concluded that such models should be applied across the petrochemical industry plants in Saudi Arabia

Impact Of Inspection Errors On The Performance Measures Of A General: Repeat Inspection Plan

Multi-characteristic critical components exist in many systems. Such components may be a part of an aircraft, spac shuttle or a gas ignition system. An inspection plan for such components has been proposed in quality control tat deals with several types of classification errors made by the inspector. In this paper, performance measures for this plan are defined and the statistical and economic impact of the several types of inspection errors on these measures is investigated. The impact of the errors is studied by conducting sensitivity analysis on the errors utilizing computer software which implements an algorithm that determines the optimal parameters of the model of the plan. The behaviour of the performance measures upon variation in the levels of errors is investigated. The results indicate that these errors have a considerable effect on the performance measures of the inspection plan

Process Targeting With Multi-Class Screening And Measurement Error

In this paper, a Process Targeting model for a three-class screening problem is developed. The model extends the work in the literature by incorporating a measurement error present in inspection systems. The strategy adopted, to nullify the effect of measurement error, is to introduce the concept of 'cut-off points', i.e. the decision during inspection is based on these cut-off points rather than specification limits of the various product grades. This model considers cut-off points as decision variables. In addition, an illustrative example is presented that compares model performance with the model presented in Min and Jang (1997). Sensitivity analysis is also conducted to study the effect of various model parameters, particularly measurement error on expected profit, optimal process mean and cut-off points

A SIMULATION-MODEL FOR DETERMINING MAINTENANCE STAFFING IN AN INDUSTRIAL-ENVIRONMENT

In a plant, the size of a maintenance staff must be related to the level of output.The optimal level of maintenance is essential for maximizing the output of the production process.This paper develops a simulation model to determine the size of a maintenance crew.The heart of the simulation model is the machine servicing model.The model is applied to a local soft drink plant to determine the optimal number of their maintenance crew, and the result of the study is presented

An Optimal Repeat Inspection Plan With Several Classifications

Multicharacteristic critical components exist in many systems. Such components could be a part of an aircraft, space shuttle or a gas ignition system. A component is critical if it causes disaster or a very high cost upon failure. In this paper, a new inspection plan for critical multicharacteristic components is presented. A mathematical model that depicts the plan is developed. An algorithm is proposed for finding the optimal number of repeat inspections and the sequence of characteristics for inspection that minimizes expected total cost per accepted component. The expected cost consists of the cost of inspection and the cost of misclassifications. The inspection plan and the model developed generalize existing models in the literature and provide a more realistic formulation. An example is given to demonstrate the plan and the model

Impact Of Scale Build-Up Models On Energy Utilization In Heat Exchangers

In this paper an energy utilization index is presented. It is used to investigate the impact of scale build-up in heat exchange equipment. The investigation is carried out using several scale build-up models. The models employed in this paper are the linear, logarithmic, and the asymptotic one. It has been demonstrated by a realistic example that the type of scale build-up model assumed greatly affects energy utilization and maintenance scheduling for heat exchange equipment. Copyright (C) 1999 John Wiley Sons, Ltd