Abstract
The use of recovered wood based fuels sometimes leads to a substantial increase in the rate of corrosion with outages and increase in maintenance costs as a consequence. Therefore, Vaermeforsk has financed two framework programmes on recovered wood based fuels. All results, except those from thermodynamical calculations, support the conclusion that enhanced levels of zinc and chlorine is one of the most important reasons for the development of harmful deposits. The system zinc chloride - potassium chloride contains several intermediate phases, out of which K{sub 2}ZnCl{sub 4} has a considerably higher melting point compared to pure zinc chloride. This provides ground for the suspicion that there may be synergetic effects between potassium and zinc and that condensation from the gas phase therefore might take place at a temperature which is higher than that which has been reported earlier. The purpose of the present study is to investigate the correctness of this hypothesis by means of thermodynamical calculations. As a first step, the energy of the intermediate phase K{sub 2}ZnCl{sub 4} was modelled utilizing results from electrochemical measurements in salt melt. The thermodynamical calculations were conducted using software which had been developed by BeN Systems including a dedicated database. Thus, all
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Citation Formats
Nolaeng, Bengt, and Sjoeblom, Rolf.
Deposition of zinc on deposits on tubes in combustion systems - a thermodynamic study; Deponering av zink i belaeggningar paa panntuber - en termodynamisk studie.
Sweden: N. p.,
2011.
Web.
Nolaeng, Bengt, & Sjoeblom, Rolf.
Deposition of zinc on deposits on tubes in combustion systems - a thermodynamic study; Deponering av zink i belaeggningar paa panntuber - en termodynamisk studie.
Sweden.
Nolaeng, Bengt, and Sjoeblom, Rolf.
2011.
"Deposition of zinc on deposits on tubes in combustion systems - a thermodynamic study; Deponering av zink i belaeggningar paa panntuber - en termodynamisk studie."
Sweden.
@misc{etde_1010822,
title = {Deposition of zinc on deposits on tubes in combustion systems - a thermodynamic study; Deponering av zink i belaeggningar paa panntuber - en termodynamisk studie}
author = {Nolaeng, Bengt, and Sjoeblom, Rolf}
abstractNote = {The use of recovered wood based fuels sometimes leads to a substantial increase in the rate of corrosion with outages and increase in maintenance costs as a consequence. Therefore, Vaermeforsk has financed two framework programmes on recovered wood based fuels. All results, except those from thermodynamical calculations, support the conclusion that enhanced levels of zinc and chlorine is one of the most important reasons for the development of harmful deposits. The system zinc chloride - potassium chloride contains several intermediate phases, out of which K{sub 2}ZnCl{sub 4} has a considerably higher melting point compared to pure zinc chloride. This provides ground for the suspicion that there may be synergetic effects between potassium and zinc and that condensation from the gas phase therefore might take place at a temperature which is higher than that which has been reported earlier. The purpose of the present study is to investigate the correctness of this hypothesis by means of thermodynamical calculations. As a first step, the energy of the intermediate phase K{sub 2}ZnCl{sub 4} was modelled utilizing results from electrochemical measurements in salt melt. The thermodynamical calculations were conducted using software which had been developed by BeN Systems including a dedicated database. Thus, all calculations have been carried out independently of those performed previously. In order to ensure full comparability, some calculations were carried out using the same input parameters as used previously and the results were essentially identical. After this, thermodynamical calculations were carried out using a database which included the intermediate phase K{sub 2}ZnCl{sub 4}. The results show that the influence of this phase corresponds to an increase in condensation temperature for zinc chloride with more than 200 deg C. A prerequisite for the formation of this phase is that the amount of available chlorine exceeds that of potassium. Similar effects can be expected also for chlorides other than potassium chloride. The effect of condensation of chlorides with a low melting point may be counteracted by presence of sulphur provided that the conditions are oxidizing. In such a case sulphates are more stable than chlorides. Thus, the conclusion of this study is that presence of zinc and chlorine can contribute to the development of deposits with low melting point in boilers. This means that thermodynamical calculations now also support the general conclusions from Vaermeforsk's framework programmes on recovered wood based fuels that these elements are potentially harmful}
place = {Sweden}
year = {2011}
month = {Feb}
}
title = {Deposition of zinc on deposits on tubes in combustion systems - a thermodynamic study; Deponering av zink i belaeggningar paa panntuber - en termodynamisk studie}
author = {Nolaeng, Bengt, and Sjoeblom, Rolf}
abstractNote = {The use of recovered wood based fuels sometimes leads to a substantial increase in the rate of corrosion with outages and increase in maintenance costs as a consequence. Therefore, Vaermeforsk has financed two framework programmes on recovered wood based fuels. All results, except those from thermodynamical calculations, support the conclusion that enhanced levels of zinc and chlorine is one of the most important reasons for the development of harmful deposits. The system zinc chloride - potassium chloride contains several intermediate phases, out of which K{sub 2}ZnCl{sub 4} has a considerably higher melting point compared to pure zinc chloride. This provides ground for the suspicion that there may be synergetic effects between potassium and zinc and that condensation from the gas phase therefore might take place at a temperature which is higher than that which has been reported earlier. The purpose of the present study is to investigate the correctness of this hypothesis by means of thermodynamical calculations. As a first step, the energy of the intermediate phase K{sub 2}ZnCl{sub 4} was modelled utilizing results from electrochemical measurements in salt melt. The thermodynamical calculations were conducted using software which had been developed by BeN Systems including a dedicated database. Thus, all calculations have been carried out independently of those performed previously. In order to ensure full comparability, some calculations were carried out using the same input parameters as used previously and the results were essentially identical. After this, thermodynamical calculations were carried out using a database which included the intermediate phase K{sub 2}ZnCl{sub 4}. The results show that the influence of this phase corresponds to an increase in condensation temperature for zinc chloride with more than 200 deg C. A prerequisite for the formation of this phase is that the amount of available chlorine exceeds that of potassium. Similar effects can be expected also for chlorides other than potassium chloride. The effect of condensation of chlorides with a low melting point may be counteracted by presence of sulphur provided that the conditions are oxidizing. In such a case sulphates are more stable than chlorides. Thus, the conclusion of this study is that presence of zinc and chlorine can contribute to the development of deposits with low melting point in boilers. This means that thermodynamical calculations now also support the general conclusions from Vaermeforsk's framework programmes on recovered wood based fuels that these elements are potentially harmful}
place = {Sweden}
year = {2011}
month = {Feb}
}