Evaluation of the influence of biomass co-combustion on boiler furnace slagging by means of fusibility correlations
Abstract
In order to show the influence of co-firing biomass with bituminous coal on ash properties, calculations of fusibility correlations have been carried out. Two Upper Silesian coals (with lower—LS and higher—HS slagging inclination) were chosen for emphasizing the influence of basic fuel. Four kinds of biomass were considered: straw, wood, dried sewage sludge and bone meal. Chemical constitutions of the mineral matter as well as the results of calculations are presented in Tables 2–5. The general conclusion is that co-firing biomass increases the fireside slagging hazard. The most difficult additional fuels are sludge and bone meal
©2004 Elsevier Ltd. All rights reserved.

1. Introduction
  The strategic objective fixed by the directive of the Polish government is to obtain until the year 2010, 7.5% of the total energy consumption from renewable sources and  14%  until  2020.  An important part of this program is the development of biomass combustion technologies.
  In  view  of  increase  in  demand  for  waste utilization  and  combustion  of  recovery  fuels, materials  of  this  kind  are  more  often  burned together with coal in steam generators, which may be the lowest cost option for reducing greenhouse gas       emissions.  Because  of their  organic  origin, these fuels  (wood,  bark,  straw,  sewage sludge, municipal  waste,  bone  meal,  etc.)  are  termed "biomass",  although  it  includes  not  only  the strictly natural components but also, for example, plastics. The  waste  fuels  also  contain  mineral matter, generally in proportions strongly different than for coal.
  Blending of coal  with  biomass  containing different mineral matter compositions may create various problems, which not only make the boiler operation difficult but can also make the co-firing biomass with coal in conventional power systems unprofitable. This paper presents an attempt to evaluate the influence of biomass co-combustion on boiler furnace walls slugging.
  Slagging  in  coal  (pulverized  fuel  or  stoker) furnaces is a very complex phenomenon depending on chemical and mineralogical composition of fly ash as well as on conditions  (temperature and velocity distribution, reducing or oxidizing atmosphere  and many  others)  in  the furnace  [1,2].It  is  obvious  that  an  increasing  amount  of low-temperature melting components in fuel ash accelerates  and  aggravates  this  process.  The transformation of inorganic components in connection with chemical reactions occurring in the flame  can  lead  to  the  formation  of  chemical compounds and their complexes with extremely low melting point and/or very high adhesion force during the sintering process. For example, eutectic mixture CaS04-CaS melts by 850 ℃. Even lower melting points (401 ℃ for Na2S2O7, 325 ℃ for K2S2O7, 552 ℃ for Na3K3Fe2(SO4)6, 625 ℃ for Na2S04-NaCl and 640 ℃ for Na2S-FeS) can be expected by combustion of fuels with high sodium and potassium content.

2. Fusibility correlations of ashes
Slugging hazard depends on the properties of ash, which  can  be  (but  only  approximately) described by characteristic ash fusion temperatures: initial deformation  temperature  (IDT),softening temperature  (ST),  hemispherical  temperature (HT) and flow temperature (FT). Over ST ashes can be strongly adhesive, which results in slugging.  Another form of slugging (typical for dry-bottom furnaces) is initiated by a sintering process giving very hard and difficult to remove deposits with time.
  It seems quite impossible to predict unequivocally the slugging and fouling properties of a given fuel. But since a long time it was found that socalled basic  (B)  compounds  lower  the melting temperature, while acidic ones (A) increase it. For a more precise predicting of ash fusibility, various correlations between  fusion  temperatures  and standardized (given in the form of oxides) chemical composition of ashes have been determined.
Often the simple B/A ratio

or percentage of basic constituents in ash

are used.
The B/A ratio has been introduced for fossil fuels with a very low phosphorus content, which therefore is not included in (1). The influence of this element on ash fusibility as well as slagging and  fouling properties  is  not  recognized  in adequate degree  and  depends  on  the  form  in which it occurs in the fly ash. If a considerable fraction  consists  of pentoxide,  one  should  be afraid of an ash melting temperature drop, because for P2O5 HT=569 ℃ [3]. Many publications (for instance [3-5]) confirm that increased P2O5 content enhances  the development of low-melting-point phases in the fly ash. Therefore, for taking into account this influence, it seems to be right to place the P2O5content in the numerator of the formula (1)-version “+P”[6].
  The B/A ratio can be used in simplified form, for
example in [7] as

这个是 要翻译的 专业论文。。
好难的。。

怎么联系你啊　　　我可以翻译出来的　　　　我的是　０７５５　　　２１０９５１７７　　张田

有高手，我们可以为你翻译。我们专业做这个的。有需要联系我：QQ：369866005

怎么联系你？

请联系我，010-68324161    13241911576    QQ：361914293    胡峰（北京广昊翻译）