Roger Renström

Basic design criteria and corresponding results performance of a pilot-scale fluidized superheated atmospheric condition steam dryer

Basic design criteria and corresponding results performance of a pilot-scale fluidized superheated atmospheric condition steam dryer

Drying of sawdust in an atmospheric pressure spouted bed steam dryer

ABSTRACT The results presented in this paper show the possibility to control the outgoing moisture content using the exhaust temperature as a control parameter. A model for heat exchange is used to support visual observations of the spouting quality in the bed. The model is also used in a discussion about the heat and mass transfer coefficients. Two efficiency concepts are defined and experimental results presented. The temperature efficiency is used to present the possibility to integrate a steam dryer into energy systems such as boilers and heat sinks. Energy efficiency is used to show the variation of the recoverable heat and to point out suitable outgoing moisture contents for steam dryers. It is important to keep the temperature after the dryer as low as possible in order to achieve a high temperature efficiency. It is also shown that energy efficiency improves with decreasing outgoing moisture content and increasing inlet steam temperature.

Controllability of Product Moisture Content When Nonscreened Sawdust Is Dried in a Spouted Bed

Abstract The control of the dried products moisture content is of importance in the production of fuel pellets. Tests have been made in air and superheated steam in a spouted bed using the outlet temperature of the drying medium as a control parameter of the dried materials moisture content. For superheated steam different settings for the inlet medium temperature are also used. In the moisture content interval of 8–17% wet base there is a linear correlation between the dried material moisture content and the outlet temperature of the drying medium. When drying nonscreened sawdust in a spouted bed it is recommendable to use the outlet temperature of the drying medium as a control parameter of the dried material moisture content. This is independent of the size of the sawdust, whether superheated steam or air is used as a drying medium.

USEFULNESS AND SIGNIFICANCE OF ENERGY AND MASS BALANCES OF A FLUIDIZED SUPERHEATED STEAM DRYER

The key characteristics of a drying method for biomass are, firstly, its ability to control temperature, steam flow and pressure drop and, secondly, its ability to stabilise the material flows, particularly the outgoing moisture content. This paper presents the usefulness and significance of using energy and mass balances to improve the measurements and control systems of a drying system of industrial size in order to fulfil the moisture content requirements for biomass compression. In order to assess the reliability and accuracy of the measurements a series of tests at four different temperature and pressure levels were conducted. By verifying the plants energy and mass balances the accuracy of the measurements could be determined and the control system was evaluated. The test results are used to determine the energy and mass balances. The control system yields good stability for the pressure drop, the temperature and the gas flow.

An Experimental Study on the Influence of Using a Draft Tube in a Continuous Spouted Bed Dryer

Further increasing the production of processed biofuel also increases the demands on drying capacity. With the aim of increasing the heat capacity flow, experimental tests have been performed on the process of drying sawdust in a continuous spouted bed dryer with nine different draft tube designs. The results showed that a draft tube with an increased length and an increased disengagement height decreased the dry substances’ flow rate throughout the dryer. The results also showed that the mass of the material in the dryer was approximately the same in all the tests. This means that the draft tubes, no matter their size, do not influence the amount of material in the dryer.

The Potential of Using Two-Step Drying Techniques for Improving Energy Efficiency and Increasing Drying Capacity in Fuel Pellet Industries

The use of wood fuel pellets has increased worldwide in recent years, and pellet producers conclude that the lack of drying capacity is a barrier to increased production. In this study, we develop a concept of two different dryers called the two-step drying technique. The aim is to show the potential for increasing the drying capacity and improving energy efficiency when introducing a second dryer into the pellet plant. The study is theoretical and based on an industrial packed moving bed dryer. It shows that the drying capacity increased by 22% when a pneumatic second dryer was used.

Performance Study of a Closed-Type Heat Pump Tumble Dryer Using A Simulation Model and an Experimental Set-Up

In the interests of competitiveness, manufactures of tumble dryers are seeking to reduce both their electricity use and the drying time. This study examines how the cylinder volume of the compressor and the total heat transfer of the condenser influence the drying time and electricity use in a heat pump tumble dryer. A transient simulation model was developed and compared to an experimental set-up with good similarity. The simulations show that increasing the cylinder volume of the compressor by 50% decreases the drying time by 14% without using more electricity.

Mean residence time and residence time distribution when sawdust is dried in continuous dryers.

Information on the mean residence time and the residence time distribution is of importance when optimizing a continuous dryer. In this study, an industrial method for determining the mean residence time is developed. The produced method is benchmarked on a laboratory scale against the stop-and-empty method. The method, which uses LiCl as the tracer does not cause any disturbances in the biofuel drying or pelleting processe.

Model for the Organisation of an Education in Engineering.

In this article it is described how the department has encouraged learning outcome discussions among the teachers and students. The typical development process of a new course is described. A two dimensional learning outcome model is also briefly introduced. This model is used to discuss what kinds of knowledge and skills are relevant in a specific course and how teaching models for these subjects can be designed and assessed. The teachers have gained more experience of various alternatives to organise a course in order to fulfil its objectives, regardless of what they are. The students now meet a variety of teaching models during the education programme. Each of them adapted to the aim and the objectives of the course.