Publikationsserver der RWTH Aachen University
Untersuchungen über die Verbrennung von Flüssigschwefel mit Sauerstoff und Spaltung von Abfallsäuren in einem Drehofen zur Herstellung von Schwefeldioxid
Abstract
dc:descriptionThe Grillo process is designed to produce sulphur dioxide from solid and liquid sulphur, spent sulphuric acids and other high-calorific-value waste materials of the chemical industry. The raw materials used are converted in a rotary kiln with a moving coke bed at approximately 1000°C under a weak reducing atmosphere; the hydrocarbon compounds are cracked and sulphur is converted into SO2. To supply additional energy, the rotary kiln is fitted with an oil burner. After passing through post-combustion chambers, the product gases from the decomposition process are cooled down in a waste heat recovery boiler and fed to an absorption-desorption reactor. In there, high-purity sulphur dioxide is obtained and stored in liquid form in pressure tanks for sale. In the Grillo process both, solid and liquid sulphur, can be used separately but also simultaneously. The use of sulphur and its combustion with air represents the state of the technology. The combustion of liquid sulphur with pure oxygen combined with the decomposition process, however, has only been practiced in the Grillo process so far. This study investigates the reactions taking place in the rotary kiln, in particular the vaporisation and combustion of liquid sulphur and the separation of spent acids using thermodynamic and reaction kinetic methods. The thermodynamic-based calculation of the chemical changes and energy conversions in the Grillo process (rotary kiln – post combustion chamber – waste heat recovery boiler) is used to assess the effects of the decomposition in the rotary kiln on the entire process. The field tests on the system using a variation of the type and quantity of substances represent an important basis for the process analysis. The temperatures and gas compositions were measured continuously at the outlet of the rotary kiln, in the post-combustion chamber as well as the waste heat recovery boiler. One of the priorities of the investigation, is the combustion of liquid sulphur with oxygen, an area which has barely been investigated up to now. During the vaporisation of liquid sulphur, gaseous sulphur molecules from S8 to S1 are created, which make up different amounts in the gaseous phase, depending on temperature and pressure. This influences, e. g., the sulphur combustion by the oxygen supply in the rotary kiln. In addition to an oxygen supply, sustaining the sulphur flame also requires a certain droplet spectrum. A further object of investigation is the separation of spent sulphuric acids, tar acids and high-heat-value waste materials in the rotary kiln. The spent acids also contain hydrocarbons and heavy metal compounds, which may be present in a solute form or as independent phases, which react differently in the rotary kiln, where special effects, such as microexplosion, may occur. The soot formation frequently occurring in the gasification of hydrocarbon compounds also takes place in the rotary kiln and thus feed the coke bed, which serves as both a heat reservoir and a carbon supply in the Grillo process. This study shall describe the kinetics of vaporisation and combustion of liquid droplets on simplistic conditions. First of all, the size of the liquid droplets that enter the hot gas compartment of the rotary kiln is calculated, considering the entry conditions. The time related sequence of the substance and heat transmission processes during the heating, vaporisation, separation and combustion of sulphuric and spent acid droplets is described on the basis of simple single droplet models. In this way the maximum diameters of the droplets which can be converted in the rotary kiln are determined. Following from calculations and actual measurements, large spent acid droplets are evidently fragmented as a result of the microexplosions and can thus fully react in the rotary kiln. One of the practical objectives of this study is the control and monitoring of the overall process, going beyond the empirical field tests. This objective is served by the thermodynamic-based process calculations carried out in combination with field tests in which the chemical changes and energy conversions in the individual reactors were recorded. The quantities and compositions of the reaction products formed in both the rotary kiln and the post-combustion chambers have also been determined. While doing so, it was possible to demonstrate that the delayed conversion of substances such as tar acids can impair the energy balance in the rotary kiln and thus the entire process. All in all, the calculations in comparison with measurements have considerably improved the basis for the practice-oriented analysis and optimisation of the process in the reactor coupling comprising rotary kiln, post-combustion chamber and waste heat recovery boiler.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2009
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Schulte, Jochen
- Contributors dc:contributor
-
- Modigell, Michael
Subjects
dc:subject × 13Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger