Processing of Aluminum Dross: The Birth of a Closed Industrial Process

This is the history of a modern aluminum dross recycling company, from its beginnings in the last years of the twentieth century to the present day. The vision of the founders was to build a local recycling plant and take full responsibility for sensitive environmental issues by recycling aluminum dross locally rather than shipping it abroad. The paper tells the history of the company from the environmental perspective, and gives an overview of some of the challenges and the decisions that followed from this vision, for instance the selection of technology. The company developed a closed industrial process for the recycling of aluminum dross, and the paper discusses some of their laboratory experiments and industrial trials. An important milestone has now been reached as the process in its present form is recognized by the environmental authorities in the country. Furthermore, it seems realistic that in the near future the final product from this process will be comparable to the product delivered in the processing of salt cake in specialized chemical plants, but at a fraction of the cost.     

Position of Maximum Ceiling Temperature in a Tunnel Fire

The position of the maximum ceiling gas temperature indicates how far the fire plum could be blown away by a ventilation flow. It could be applied to estimate the activation of a detection system or a sprinkler system, or to estimate the range of damage to the tunnel structure. An equation for predicting the position of the maximum ceiling gas temperature in a tunnel fire is proposed based on a theoretical analysis and validated using both laboratory test data and full scale test data. A flame angle has been defined based on the position of the maximum ceiling temperature in a tunnel fire. The flame angle is directly related to the dimensionless ventilation velocity, and it becomes insensitive to the heat release rate for a large tunnel fire. Further, it is found that a constant critical flame angle exists, defined as the flame angle under the critical condition when the backlayering just disappears. For a given tunnel and fire source, the flame angle under critical conditions is the same value, independent of heat release rate, and the maximum ceiling temperature under critical conditions always corresponds to the same position. Generally the horizontal distance between the position of the maximum ceiling temperature and the fire source centre is around 1.5 times the effective tunnel height under the critical condition.     

Numerical simulation of the wind shadow effect on the convective heat transfer to glass bulb sprinklers

A theoretical analysis of the wind shadow effect caused by the arms of the sprinkler frame has been performed using a finite volume computer code. The calculations show that the influence of the arms of the frame upon the convective heat transfer to the bulb is small when the arms of the sprinkler frame and the bulb are orientated perpendicular to the flow. The arms of the frame cause a slight acceleration of the flow around the bulb. Hence, the heat transfer to the bulb in this orientation is somewhat greater than for free flow around a cylinder. In the case when the arms of the sprinkler frame are aligned with the flow, the heat transfer is decreased by approximately a factor of two for the particular geometry considered. This is in agreement with results from wind-tunnel tests for the same geometry. The Nusselt number for this case is still roughly proportional to the square root of the Reynolds number. This finding is of practical importance, as the lumped mass theory for calculating the time to operation of sprinklers relies heavily on the assumption of a square root dependence of the Reynolds number. Good agreement is found between calculated and measured velocity profiles in the region between the glass bulb and the upstream arm of the frame, when the arms are aligned with the airflow.     

Positive Pressure Ventilation in Single Medium-Sized Premises

The objective of this study was to investigate the feasibility, for the fire and rescue services, of using mobile fans as a pro-active means of ventilating smoke in medium-sized premises. The efficacy of various types of such fans was therefore tested in two different-sized premises by measuring air pressures and volume flow rates in the premises. Three different types of mobile fans were used. The study was a cold exercise, i.e. the effects of heat and smoke were not considered, in view of the fact that we were primarily interested in the volume flow capacity and pressure. In order better to illustrate and understand the experimental data, simple theoretical models were developed which describe how various parameters affect the results. The parameters considered in the model were the size of the supply and exhaust openings, the primary air flow of the fan, volume flow and static pressure in the building.     

Response characteristics of glass bulb sprinkler heads mounted in a paint spray booth

The response of sprinklers mounted in a paint spray booth is usually influenced by paint covering the heat-sensitive element. To avoid this problem, sprinklers are often covered to prevent the paint from accumulating on the heat-sensitive element. The influence of various numbers of paint layers and different types of covers on the response time of two different types of glass bulb sprinkler heads has been investigated. Both wind-tunnel tests and large-scale fire tests were performed in the test series.It was found that covers delayed the activation of the sprinklers considerably, though a faster response was obtained with a quick response sprinkler than with a standard response sprinkler. It was found that the accumulated paint on the heat-sensitive element also affected the response time, but not nearly as much as the covers. It was also found that a paint layer covering both the glass bulb and the frame acted as a glue; the consequence was that the spray pattern of the sprinkler was considerably affected.     

Fire Spread and Flame Length in Large-Scale Tunnel Fires

An analysis of fire spread during four large-scale fire tests that were performed in the Runehamar tunnel in Norway is presented. The fire loads consisted of mock-ups simulating a Heavy Goods Vehicle (HGV) trailer. The fire spread downstream of the HGV trailer mock-ups was studied, both to large targets with the same type of commodities as used in the trailer mock-up for each tests, and to small pieces of wood and plastic poles placed at different distances from the fire. The purpose was to determine a critical distance for fire spread between HGV trailers for different heat release rate histories. The time to ignition of a second object and fire spreading distances were estimated from post-visual observations and temperature measurements. Correlations for flame length were developed from the experimental results. Since the average temperature of the cross-section often is used to estimate fire spread, results from a model for the average temperature were compared with the measured temperatures.     

Gas temperature measurements using fibre Bragg grating during fire experiments in a tunnel

Gas temperature measurements with thermocouples are affected by radiation. This effect means that the temperature measured by a thermocouple can be far from the actual gas temperature. To study this effect and to compare the thermocouple readings with the readings of a fibre Bragg grating (FBG) sensor, fire experiments were performed in a model-scale tunnel. In this paper the results from two such fire experiments are presented. The temperatures measured using thermocouples with different diameters and the FBG sensor are compared and discussed. The “true” gas temperature, corrected for radiation effects from the thermocouples, was calculated from the results from the thermocouples with different diameters. The results show that the temperature measured by the FBG sensor is closer to the “true” gas temperature than is the case for any of the thermocouples used in these tests.     

Full Scale Firefighting Tests in the Tistbrottet Mine

The paper describes full-scale fire-fighting tests performed in an underground mine. A total of six different methods to fight a full scale fire in a mine tunnel were tested. The methods involved different fire-fighting equipment but were comparable regarding fundamental conditions such as length of response-route, fire-fighting set-up, and smoke and fire size. The aim was to compare different equipment and methods to reach and eventually extinguish the fire. Fire fighters using breathing apparatus (BA) were monitored regarding air consumption, movement speed and local actions and decisions. The results are presented and analyzed in respect to fire-fighting efficiency, front BA operations including moving speed and performed actions, as well as the time to successfully put out the fire. Measurements of heat release rates, temperatures and moving speeds are given in order to quantify the efficiency of the operation. Results indicate that a timespan of 15–30 min is needed for the firefighters to reach the fire source and achieve the extinguishing criteria in five of the tests. The standard equipment and nozzles shows good performance in the tests. A limiting factor on the firefighter’s endurance is the amount of air that is available. As a result from these findings the endurance of BA-teams could improve if focus is put on team organization, lightweight equipment and air supply.     

Maximizing industrial infrastructure efficiency in Iceland

As a consequence of the increasing aluminum production in Iceland, local processing of aluminum skimmings has become a feasible business opportunity. A recycling plant for this purpose was built in Helguvik on the Reykjanes peninsula in 2003. The case of the recycling plant reflects increased concern regarding environmental aspects of the industry. An interesting characteristic of this plant is the fact that it is run in the same facilities as a large fishmeal production installation. It is operated by the same personnel and uses—partly—the same equipment and infrastructure. This paper reviews the grounds for these decisions and the experience of this merger of a traditional fish melting industry and a more recent aluminum melting industry after 6 years of operation. The paper is written by the original entrepreneurs behind the company, who provide observations on how the aluminum industry in Iceland has evolved since the starting of Alur’s operation and what might be expected in the near future.