On-line moisture determination of ore concentrates 'a review of traditional methods and introduction of a novel solution'.

The manual gravimetric drying moisture determination methods currently employed by most mineral processing plants fail to provide timely and accurate information required for automatic control. The costs associated with transporting and handling concentrates still represent a major portion of the overall treatment price. When considering the cash flow of a mining operation that is governed by both the smelter contract, with moisture penalties and the quantity and quality of the concentrates shipped, an efficient method of on-line moisture content would be a welcome tool. A novel on-line determination system for ore concentrate moisture content would replace the tedious manual procedure. Since the introduction of microelectronic-based control systems, operators have strived to reduce the treatment costs to the minimum. Therefore, a representative and timely determination of on-line moisture content becomes vital for control set points and timely feedback. Reliable sensors have long been on the 'wish list' of mineral processors since the problem has always been that you can only control what you can measure. Today, the task of moisture determination is still done by the classical technique of loss in weight utilizing uncontrolled procedures. These same methods were introduced in the earliest base metal concentrators. Generally, it is acceptable to have ore concentrate moisture content vary within a range of 7-9%, but controlling the moisture content below 8% is a difficult task with a manually controlled system. Many times, delays in manually achieving reliable feedback of the moisture content results in the moisture varying from 5-12% before corrective actions can be made. This paper first reviews the traditional and widely available methods for determining moisture content in granular materials by applying physical principles and properties to measure moisture content. All methods are in some form affected when employed on mineral ore concentrates. This paper introduces and describes a novel on-line moisture sensor employed for mineral processing de-watering applications, which not only automates the tedious tasks but also results in reliable moisture feedback that can be used in the optimization of the de-watering process equipment such as pressure or vacuum filters and fuel-fired driers. Finally, two measurement applications will be presented which indicate the usefulness and summarizes the measurement requirements for the proposed method of employing drag force and mechanical properties of the material itself to determine the moisture content.

1,005 delayed days: a study of adult psychiatric discharge.

Delay in discharge of psychiatric patients frequently is attributed to the lack of available community resources, or to the unwillingness of the patient or his family to accept discharge or transfer to another facility. The role of the psychiatric system itself rarely is mentioned as a factor. A study of 138 psychiatric patients in a Canadian community hospital in 1978 showed that 35 per cent were judged to be delayed in their discharge. By far the greatest source of delay was the administration of the various psychiatric services within the system. Delayed patients were found to be statistically similar to nondelayed patients, except for the delayed patients tendency to be poorer and to be overrepresented on two of the six wards studied. The cost implications of the delays in discharge are discussed, as are suggestions for solving the problems within the administrative framework.