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Mixing in batch G-L-L′ reactors with top and bottom blowing

Chemical Engineering Science 54(1999)4839}4844

Mixing in batch G-L-L Y reactors with top and bottom blowing

M.D m az *,M.Mart m n

Department of Chemical and En v ironmental Engineering,Uni v ersity of O v iedo,c /Julia n Cla v er n a s /n,33071O v iedo,Spain

Abstract

Mixing in the industrial oxygen steel converter was studied using a water }vaseline }air cold model reactor,equipped with top and

bottom pneumatic agitation.The e !ect of a number of di !erent parameters were studied:the relative e !ect of top and bottom blowing rates,the variation in surface tension,the e !ect of the organic phase,the variation in the relative position of the lance with respect to the quiescent bath level,and the direction of the streamlines.The results are analyzed in terms of the parameters of a previously tested compartments model. 1999Elsevier Science Ltd.All rights reserved.

1.Introduction

Top blowing used to introduce oxygen in steel conver-ters does not produce a good mixing in the bath,gas injection through the bottom of bath,which does im-prove the mixing conditions,is a widely spread practice in the steel-making process.It is very important to deter-mine the parameters on which the mixing and hence homogeneity depend,since the molten steel can present inhomogeneities with regard to temperature and chem-ical composition,because of the short reaction times (+15min)and the successive addition of reactives dur-ing this period.Previous cold model studies have shown the main in #uencing parameters (Mart m n,1994):gas #ow rate,addition of the third phase,height of the lance over the bath and surface tension of the liquid phase.

Nakanishi,Fujii and Szekely (1975)were the "rst to correlate mixing time with agitation power (t "a @

);

they considered that the mixing time was independent of the tested operating conditions.However,the value of the parameters `a a and `b a obtained by di !erent authors are quite di !erent (Schneider,Dromer,Mietz &Deters,1984;Sinha &Mcnallan,1985;Stapurewicz &Themelis,1987).This means that measurement of the mixing time depends on the operating conditions,the geometry of the tank,the point of tracer injection,and the point of measurement,among other factors.In the present work agitation power,

,is expressed by means

*Corresponding author.

of Stapurewizc 's equation (Stapurewicz &Themelis,1987).

Due to hydrodynamics and the presence of di !erently agitated zones,the mixing time near the walls may be higher than in other zones of the reactor.Thus,if both the tracer injection point and the measurement point are placed in the zones walls,the mixing time thus obtained may be considered the global mixing time,since when mixing is achieved here,the tracer concentration will already be uniform in the other zones of the reactor.Conversely,local mixing times are obtained when other possible geometric dispositions for tracer injection and the measurement probe are employed.Simple visual ob-servation of the reactor reveals that there are zones with quite di !erent behaviour,and hence local mixing in the reactor has to be studied.Since in the real converter the addition of di !erent elements (lime,scrap,etc.)is carried out in the central zone,because of the high turbulence that exists in this region (Szekely &Themelis,1971),mixing variables in the cold model are mainly studied with injections in the central upper part.

Moreover,due to the importance that mixing condi-tions and #uid #ow phenomena have on the observable kinetics of the reactions that are produced inside the steel converter,the development of mixing models that de-scribe the behaviour of the reactor as a function of the previously mentioned parameters is of interest.Addi-tionally,the use of a simple compartments model is important because of the ease with which (even complex)chemical kinetics may be introduced,thus allowing the behaviour of this reactor to be anticipated in the steel-making process.

Table 1

Physical properties of aqueous and organic phases

Real converter

Cold model

Properties

Steel (l ) Slag (l ) Water (l )Vaseline (l )Density (kg/m )7150

30611000840Viscosity (Ns/m )

0.0050.0710.0040.043Surface tension (mN/m)1046

360

30}70

(( *Y ! *)/ *

) 0.75

0.63

Average temperature "16003C.

Formation of slag drops inside the steel

phase.

Fig.1.Devices for (a)bottom and (b)top blowing.

2.Experimental apparatus and conditions

A cold model simulating a 250-ton capacity industrial

converter was employed.A strict 1/10length scale down was used to build the cold model.The devices for bottom blowing (a)and top blowing (b)are schematically shown in Fig.1.The bottom blowing device is made up of 16porous units.In the real converter,the available surface for injection of gas is approximately 312mm /porous unit.Since the scale factor employed in the construction of the model is 0.1,each porous unit in the scale model will consist of 3.12mm of free section for the gas #ow.To obtain a bubble diameter approximately equal to the diameter of the bubbles in the real converter,the height of the trapeze is maintained constant in the cold model;the bottom-blowing device is thus composed of 16holes of 2.1mm of equivalent diameter.With respect to top blowing,oxygen is injected into the real converter through a lance ending in a convergent }divergent nozzle.During the real process,the height of the lance over the melt ranges from 3.8to 1.5m.In the cold model,the height of the lance employed in this study varied between 21.5and 37.5cm,thus maintaining a range of geometri-cal analogy.

Water (aqueous phase)was employed to simulate the molten steel,vaseline (organic phase)to simulate the slag,and the gaseous phase (employed in the blowing process)was simulated using air.The choice of the employed #uids was made considering the need for the closest physical similarity in density and viscosity relations in both reactors,so as to induce the same type of physical phenomena in both (the formation of emulsions,the formation of swarm of bubbles,etc.).As an example,similar velocity "elds around particles will give analog-ous properties transfer rates,and to have this velocity similarity,similar values of (( *! *Y )/ *

) are needed if

a Stokes 'law approach is assumed.The physical proper-ties of the di !erent phases are presented in Table 1,which shows how the similarity when comparing densities and viscosities is high,being lower in the case of surface tension.For these multiphase systems,full similarity is impossible.

A conductivimetric method,based on the addition of a tracer (KCl)in the aqueous phase was employed to study the mixing in the reactor (Ramani &Lahiri,1988).Conductivity was measured using two conductivity probes connected to a personal computer.A visual,colorimetric method based on the change in colour of the indicator (phenolphtalein)present in the aqueous phase was also used.Before beginning the experiment,the aqueous phase was acidi "ed (HCl)and phenolphtalein was added,while an injection of NaOH was likewise introduced to change the colour.

The notation employed to indicate local positions is shown in Fig.2:`M a is the measurement point of the changing property,`I a is the point where the tracer is added and `d a is the lineal length between both points.It is of interest to be able to see the e !ect caused by the liquid circulation (streamlines)on the mixing time in the notation itself;direct (d )and inverse (!d )distances with respect to the streamline are considered.

3.Results and discussion

The visual method shows how at the beginning the colour disappears from the surface,as the gas blown

4840M.D n &az,M.Mart n &n /Chemical Engineering Science 54(1999)4839}4844

Fig.2.Local positions notation.

through the bottom of the reactor displaces the liquid

phase from the centre to the wall and therefore,the

colour is displaced through the surface of the liquid

towards the wall.After a certain time,a great part of the

bulk has already changed colour,only a small zone at the

bottom of the reactor remaining without changing,in

the zone of the walls,where a small,stagnant zone may

exist.Inside the plume,the change in colour occurs very

quickly due to the high turbulence in this zone.There-

fore,the reactor may be divided into two zones in which

the behaviour of the aqueous phase is di!erent with

respect to the mixing.Thus,the use of a simple compart-

ments model seems to be an adequate option for simula-

ting the mixing in the reactor,which,due to its simplicity,

is also very appropriate for subsequently simulating the

chemical process.

Compartments model are widely employed due to

their#exibility and because they can be used to simulate

reactors of any shape(Cui,Vanderlans,Noorman&

Luyben,1996;Degaleesan,Dudukovic,Toseland&

Bhatt,1997).The simple model employed here considers

the existence in the converter of two zones designated as

a stagnant zone of volume< and a well-mixed zone of volume< (Robinson,Debelak&Tanner,1988).The model describes the concentration change between

the well-mixed zone(where the tracer is injected)and the

stagnant volume.This model considers that the concen-

tration within each zone is uniform and also considers

that a certain#ow rate,q,is exchanged between both

zones.

Taking into account the initial conditions(m (t"0)" 0,m (t"0)"m ,c "m /< )and the

equilibrium Fig.3.Variation in< and q with the agitation power in the two-phase system,in the case of direct distances.

concentration c "m /(< #< )the equations that de-scribe the variation in the concentration,c(t)"m(t)/<,in both zones are:

c (t)

"1!exp !q 1< #1< t ,(1)

c (t)

"1#

exp !q 1< #1< t .(2)

The model will be valid only when it is possible to simultaneously"t the conductivity curves experimentally obtained in the two di!erent zones considered in this model.The application of this model allows the values of the stagnant and the well-mixed zone volumes to be calculated,as well as the#ow rate exchanged between both volumes,at di!erent points within the reactor and for di!erent gas#ow rates.

3.1.Bottom blowing:two-phase system(aqueous phase in the reactor,? /D "0.35)

The e!ect caused on the mixing by the use of direct and inverse distances was studied.The"tting parameters obtained,that is to say,the stagnant volume and the volume#ow rate exchanged between the tanks,are shown in Figs.3and4.Results for both types of spatial con"gurations show that the values obtained for these "tting parameters are similar,due to the fact that the same gas#ow rates are employed and the agitation power received by the aqueous phase is similar in all the cases.

At the same time,in both"gures it is possible to observe how< decreases as the bottom gas#ow rate increases(Koria&Pal,1991;Roth,Peter,Schindler &Koch,1995),and how q becomes higher as the bottom gas#ow rate increases,due to the agitation power re-ceived by the bath,which increases with the gas#ow rate.

M.D n&az,M.Mart n&n/Chemical Engineering Science54(1999)4839}48444841

Fig.4.Variation in <

and q with the agitation power in the two-phase

system,in the case of inverse

distances.

Fig.5.Variation in <

with agitation power in the three-phase system

for "71.8mN/m and "31.8mN/m.

3.2.Bottom blowing :three-phase system (aqueous and organic phases in the reactor ,? /D "0.42)

If the values of the parameters of the model obtained under similar operating conditions for the three-phase and the two-phase systems are compared,it can be ob-served (Figs.3}6)how the value of the stagnant volume is greater for the three-phase system than for the two-phase system and how the exchanged volume #ow rate is lower,since the organic phase modi "es the mixing conditions in the reactor.

Another parameter that must be taken into account due to its importance is the surface tension of the steel phase,which decreases exponentially in the industrial converter as the dissolved oxygen increases.The surface tension was modi "ed in the cold model with a surfactant (Arkopal N-060)until reaching a value of 31.80mN/m.Fig.5shows how <

is greater when the surface tension

of the aqueous phase is not reduced.Fig.6shows how q is lower when the surface tension phase is not reduced.

This

Fig.6.Variation in q with agitation power in the three-phase system,for "71.8mN/m and "31.8mN/m.

behaviour may be explained taking into account the fact that the decrease in surface tension increases the mobility of the system.

The e !ect of the agitation power is similar in all experi-ments,that is to say,the stagnant volume decreases in a practically linear way and the exchanged volume #ow rate increases as the agitation power increases.

Agreement between the curve obtained employing the proposed model and the experimental data was tested with Fisher 's test.The model is acceptable if F A

(F ,

where F A

is the value of Fisher 's test parameter calculated

from the experimental data and F is the value of the test which can be found in tables for a given level of con "-dence.Considering a level of con "dence of 0.95,validity of the model is assumed as F A "1.01and F "1.84.

https://www.wendangku.net/doc/e47175968.html,bined blowing :e w ect of the v ariation in the top gas y ow rate (two-phase system )

To modelize the mixing under combined blowing con-ditions,the two tanks model was also employed,since bottom blowing contributes more than top blowing to the mixing in the reactor (Mart m n,1994).

Fig.7shows the variation in <

and q with the bottom

gas #ow rate,for two values of the top gas #ow rate (Q 2 "0.0637m /s and Q 2

"0.0288m /s)and a "xed height of the lance.In this "gure,it can be observed how the stagnant volume decreases as the value of the bottom gas #ow rate increases.This "gure also shows that the di !erences between the values of the stagnant volume obtained for the two top gas #ow rates employed are small,and these di !erences are lower in the case of the highest bottom gas #ow rate,due to the fact that the contribution of this type of blowing is greater than that of top blowing to the combined blowing.At the same time,this "gure shows how q increases with the bottom gas #ow rate and how the values obtained for the volumetric

4842M.D n &az,M.Mart n &n /Chemical Engineering Science 54(1999)4839}4844

Fig.7.Variation in < and q ,for two values of Q 2

in the case of the

two-phase system,h "21.5

cm.

Fig.8.Variation in <

and q ,for two values of the height of the lance in

the case of the two-phase system,Q 2

"0.0637m /s.

#ow rate are not very di !erent for the two top gas #ow rates employed.Under top blowing conditions,not all the energy supplied by the gas jet that impacts on the surface of the bath is useful;only a part of this energy is employed to produce the mixing of the bath.The ener-getic contribution of top blowing during combined blow-ing is lower than the contribution of bottom blowing in spite of the high gas #ow rate employed through the lance (Sano &Mori,1983).

https://www.wendangku.net/doc/e47175968.html,bined blowing :e w ect of the v ariation in the height of the lance (three-phase system )

As shown in Fig.8,increasing the gas #ow rate intro-duced through the bottom of the reactor provokes a de-crease in the stagnant volume.This "gure also shows how the value <

is smaller when the height of the lance

is lower;this is because the energy transmitted by the gas jet to the bath is higher when this distance decreases.With respect to the values of q ,it can be observed how this parameter increases when the bottom gas #ow rate increases,due to the existence of a great turbulence in the reactor,similar behaviour to that observed in the case of the two-phase system.As in the case of bottom blowing,

Fisher 's test was employed to verify the proposed model.

The validity of the model is acceptable as F "1.32and F A

"1.1.4.Conclusions

E The mechanism of mixing in the steel converter can be described by a model based on the existence of two zones in the reactor:a well-mixed zone and a stagnant zone,between which exchange of mass takes place.The study of the model parameters shows how the stagnant volume decreases and the volume #ow rate exchanged between the two tanks becomes higher as the gas #ow rate increases,in all the cases considered.The values of the stagnant volume and the exchanged volume #ow rate obtained for the direct and the in-verse distances are quite similar,since the agitation power received by the aqueous phase is similar in all the cases.

E The increase in the value of the relationship ?

/D ,

under similar operating conditions,provokes an in-crease in the value of the stagnant volume and a de-crease in the exchanged volume #ow rate.The organic phase simulating the slag in the real steel converter modi "es the mixing conditions in the reactor;the agi-tation power per unit of volume is lower when this third phase is present in the reactor.When the surface tension is reduced,the value of <

is lower than that

obtained with the original surface tension and the value of q is higher;a decrease in the surface tension increasing the mobility of the system.

E Under combined conditions,the di !erences between the values of the stagnant volume obtained for the top two gas #ow rates employed are small,as the contribu-tion of bottom blowing is greater than that of top blowing to the combined blowing.The same type of behaviour can be observed in the case of the volumet-ric #ow rate exchanged between the tanks.Finally,it has been shown that for a lower height of the lance,<

is smaller and the value of q is higher,as the energy communicated by the gas jet to the bath is higher when this distance decreases.Notation a "tting parameter b "tting parameter c tracer concentration,kg m \ D diameter of the free surface,m h height of the lance,m ? depth of the bath,m m mass of the tracer,kg Q bottom gas #ow rate,m s \ Q 2top gas #ow rate superior,m s \ q volume #ow rate exchanged between the tanks,

m s \

M.D n &az,M.Mart n &n /Chemical Engineering Science 54(1999)4839}48444843

t time,s

volume of the stagnant zone,m

Greek letters

agitation power,W kg\

surface tension,N m\

Subscripts

0initial conditions

1stagnant zone

2well-mixed zone

R equilibrium

References

Cui,Y.Q.,Vanderlans,R.G.J.M.,Noorman,H.J.,&Luyben,K.C.A.

M.(1996).Chemical Engineering Research and Design,74(A2),261.Degaleesan,S.,Dudukovic,M.P.,Toseland,B.A.,&Bhatt,B.L.

(1997).Industrial Engineering Chemical Research,36(1l),4670. Koria,S.C.,&Pal,S.(1991).Steel Research,62(2),47.

Mart m n,M.(1994).Mixing and mass transfer process in the steel converter,Ph.D.Thesis,University of Oviedo.

Nakanishi,K.,Fujii,T.,&Szekely,J.(1975).Ironmaking and Steel-making,3,193.

Ramani,S.,&Lahiri,A.K.(1988).Steel Research,59(3),93. Robinson,J.E.,Debelak,K.A.,&Tanner,R.D.(1988).Chemical Engineering Communications,63,143.

Roth,C.,Peter,M.,Schindler,M.,&Koch,K.(1995).Steel Research, 66(8),325.

Sano,M.,&Mori,K.(1983).Transactions of the Iron and Steel Institute of Japan,23,169.

Schneider,S.,Dro mer,C.,Mietz,J.,&Oeters,F.(1984).Sixth Ja-pan}Germany Seminar Proceedings,Tokyo,1.

Sinha,U.P.,&Mcnallan,M.J.(1985).Metall.Trans.B,16b,850. Stapurewicz,T.,&Themelis,N.J.(1987).Canada Metallurgical Quarterly,26(2),123.

Szekely,J.,&Themelis,N.J.(1971).Rate phenomena in process metal-lurgy.New York:Wiley.

4844M.D n&az,M.Mart n&n/Chemical Engineering Science54(1999)4839}4844

图表与口诀记忆when、as、while的区别

图表与口诀记忆when、as、while的区别 1.图表与口诀前知识关键是比较主从句子的动词，看其动词的持续性。瞬间的理解成点，持续的理解成线。主从关系有：点（点点、点线），线线，线点。点：为瞬间动词，准确地称为“终止性动词”，指动词具有某种内在界限的含义，一旦达到这个界限，该动作就完成了。如come（来），一旦“到来”，该动作就不再继续下去了。瞬间动词：arrive, begin, borrow, become, buy, catch, come, die, find, go，give, graduate, join, kill, lose, leave, marry, realize… 线：为非瞬间动词，准确地称为叫“延续性动词”。包括动态动词静态动词。动态动词：live, sit, stand, study, talk, work, write… 静态动词（状态动词）：情感、看法、愿望等。Be, belong, consist, exist, feel, hate, have, hope, love, want… 兼有瞬时和非瞬时的动词：feel，look，move，run，work，write…，需要根据不同的语境判断。 2. when、as、while的区别一览表【表格说明】：第一个点或者线表示从句谓语动词的持续性特征，黑点表示从句所表示的动作持续短，为瞬间动词，线表示持续长，为非瞬间动词。1~7为主句与从句所表示的动作时间有重合，第8为主句与从句所表示的动作不是同时发生，而是有先后顺序。线线重相并发生，长线” 【主句谓语为非瞬间动词中的动态动词】【记忆：等线动，相并发生，但：【主句谓语为非瞬间动词中的静态动词】【记忆：等线动，

什么是淘宝直通车,具体怎么做直通车

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when,while,as的区别

一、根据从句动作的持续性来区分 1.“主短从长”型：即主句是一个短暂性的动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while [when, as] he was playing tennis. 吉姆打网球时把手臂扭了。 As [When, While] she was waiting for the train, she became very impatient. 她在等火车时，变得很不耐烦。注意：as用于引出一个持续性动词表示“在……期间”时，其谓语通常只能是那些含有动作和发展意味的动词，一般不能是那些不用于进行时态的动词(如be, seem, love, want, agree, see, know, have 等)，所以下面一句中的while不能换为as： A：I’m going to the post office. 我要去邮局。 B：While you are there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗? 若主句与从句表示的是两个几乎同时发生的动作，含有类似汉语“刚要……就”“正要……却”的意思，英语一般要用as(也可用when)，且此时通常连用副词just。且此时，从句一般用进行时，主句用短暂性动词的一般时态。【注意与六区别】 I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。 Just as [when] the two men were leaving, a message arrived. 就在这两个人要离开的时候，突然有了消息。 2.“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，且强调主句动作或状态延续到从句所指的整个时间，此时通常要用while。如： I always listen to the radio while I’m driving. 我总是一边开车一边听收音机。 He didn’t ask me in; he kept me standing at the door while he read the me ssage. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边……一边”之意时，则习惯上要用as。如： He swung his arms as he walked. 他走路时摆动着手臂。 I couldn’t remember a story to tell the children, so I made one up as I went along. 我想不出有什么故事可给孩子讲了，只好现编现讲。 3.“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用a s或when，但不能用while。如：

while、when和as的用法区别

as when while 的区别和用法 as when while的用法一、as的意思是“正当……时候”,它既可表示一个具体的时间点，也可以表示一段时间。as可表示主句和从句的动作同时发生或同时持续，即“点点重合”“线线重合”；又可表示一个动作发生在另一个动作的持续过程中，即“点线重合”，但不能表示两个动作一前一后发生。如果主句和从句的谓语动词都表示持续性的动作，二者均可用进行时，也可以一个用进行时，一个用一般时或者都用一般时。 1、As I got on the bus，he got off. 我上车，他下车。（点点重合）两个动作都是非延续性的 2、He was writing as I was reading. 我看书时，他在写字。（线线重合）两个动作都是延续性的 3、The students were talking as the teacher came in. 老师进来时，学生们正在讲话。（点线重合）前一个动作是延续性的，而后一个动作时非延续性的二、while的意思是“在……同时（at the same time that )”“在……期间(for as long as, during the time that）”。从while的本身词义来看，它只能表示一段时间，不能表示具体的时间点。在时间上可以是“线线重合”或“点线重合”，但不能表示“点点重合”。例如： 1、He was watching TV while she was cooking. 她做饭时，他在看电视。（线线重合） 2、He was waiting for me while I was working. 我工作的时候，他正等着我。（线线重合） 3、He asked me a question while I was speaking. 我在讲话时，他问了我一个问题。（点线重合）

淘宝直通车新手入门教程

淘宝直通车新手入门教程 l新手入门第一课――广告位与竞价词一.广告位让我们来亲身感受一下什么是直通车的广告!按我的步骤来一起操作一下哦,Go 1. 首先打开淘宝首页,在搜索框输入”风衣”这个词,点击搜索按钮,显示搜索页面 2. 往右上角看,有一个掌柜热荐的位置,下面有5个广告位,这是直通车的广告位 3. 把页面拉到最底端,会看到三个大图,这三个也是直通车的广告位以上的步骤可以演示为下图,红色框的为直通车广告位. 1. 2.

3. 二.竞价词这些卖家的广告为什么会出现在这里呢? 因为他们都设置了风衣这个竞价词那竞价词又是什么呢? 就是买家输入这个词搜索，你的广告就能出现。就像百度的搜索,如果信息符合被搜索的关键词,这条信息就会出现,在直通车,我们把这个关键词称为竞价词. 比如你希望买家输入“风衣”这个词，他就可以在我们的广告位上看见你的宝贝，那么“风衣”就是你要设置的竞价词。

新手入门第二课——收费与排名原则大家都知道,直通车是一个收费的产品,那到底是怎么收费呢? 多少钱一天还是有包月还是其他收费方式呢? 直通车不是按时间收费的,它的收费方式是:按点击收费广告展示在广告位上了,我们不收费,只有当买家对您的宝贝感兴趣,点击了您的宝贝,才会有费用产生.所以广告展示跟时间无关，只和余额、日最高限额和定时投放有关（第三课有详细讲解）。点一次多少钱呢? 每次点击最少1毛钱那最多呢? 最多多少钱是您自己设置的,您设置的高,扣的钱就多,设置的低就扣的少. 大家都喜欢设置的低,可以少扣点,那设置的高和低有什么区别呢?(排名规则) 比如”风衣”这个词,有20个人买了这个词,但是第一页只有5个人广告位,谁排在前面呢?这时候就需要看谁对”风衣”这个词的出价高,出价越高,排位越前,当然排位越前的每次点击扣的费用也越多. 这个出价就是竞价词的价格扣钱是从我的支付宝账户扣还是有什么其他方式呢? 是从直通车账户扣款的,首次充值直通车最少500元,按点击扣费,没有任何服务费用,也没有使用期限

第七--when-while-as-区别及练习.

When while as区别一、根据从句动作的持续性来区分 1、“主短从长”型：即主句是一个短暂性动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while［when， as］ he was playing tennis. 吉姆打网球时把手臂扭伤了。 2、“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，且强调主句动作或状态延续到从句所指的整个时间，此时通常要用while。 I always listen to the radio while I’m driving. 我总是一边开车一边听收音机。 He didn’t ask me in; he kept me standing at the door while he read the message. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边……一边”之意时，则习惯上要用as。如： He swung his arms as he walked. 他走路时摆动着手臂。 3、“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用as 或when，但不能用while。如： It was raining hard when [as] we arrived. 我们到达时正下着大雨。二、根据主句与从句动作是否同时发生来区分 1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语“一……就”的意思，英语一般要用as (也可用when)。如： The ice cracked as [when] I stepped onto it. 我一踩冰就裂了。 2、若主句与从句表示的是两个几乎同时发生的短暂性动作，含有类似汉语“刚要……就”“正要……却”的意思，英语一般要用as(也可用when)，且此时通常连用副词just。如： I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。三、根据是否具有伴随变化来区分若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用when或while。如： The room grew colder as the fire burnt down. 随着炉火逐渐减弱，房间越来越冷。注：若不是引导从句，而是引出一个短语，则用with，不用as。如： With winter coming on, it’s time to buy warm clothes. 随着冬天到来，该买暖和衣裳了。四、根据从句动作的规律性来区分若暗示一种规律性，表示“每当……的时候”，英语一般要用when。如： It’s cold when it snows. 下雪时天冷。五、根据主从句动作的先后顺序来区分若主句与从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when。

直通车教程

在对淘宝直通车的运作模式和基础操作有了一定的了解后，就该进行淘宝直通车实战了。一大把服装圈为网友们带来《淘宝直通车技巧篇》，希望可以让广大网友更好的掌握淘宝直通车的技巧从而更好的进行推广活动。我们知道，直通车搜索的原则是当卖家设置的词和买家搜索的词完全一样的时候，才会展示宝贝的广告。所以说，给宝贝设置竞价词是至关重要的。直接影响到您的推广效果。有的掌柜会问，那我该怎么设置竞价词？设置竞价词的思路是什么呢？淘宝直通车技巧篇：设置竞价词的思路设置竞价词一定要站在买家的角度去考虑，您要买这件宝贝的适合，会用些什么样的词搜索。要把浏览量大的词和浏览量小的词结合起来推广。浏览量大的词排名不要很前面（除非产品很有优势），浏览量小的词一定要排在前面，否则出现的机会就更少了。设置竞价词的基本原则是：您要从买家的角度去考虑，如果我是买家，我要搜索这件宝贝要输入哪些关键词呢？

淘宝直通车技巧篇：设置竞价词的思路首先，第一点，宝贝名称，从您宝贝的名称中提炼出来关键词来作为宝贝的竞价词。第二点，宝贝详情里的属性词，宝贝详情是我们在编辑宝贝信息的时候抓取出来的关键信息，也是买家十分关注的，所以说用宝贝详情里的属性词作为宝贝的竞价词是十分明智的。第三点，名称词和属性词里面的组合词。这些词相对比较精确，买家的购买欲望也十分强。淘宝直通车技巧篇：设置竞价词的思路总结了设置竞价词的思路，我们再来看一个例子。图中展示的是一件韩版风衣，它的宝贝详情已经给大家列出来了。包括它的价格，颜色，品牌以及风格。各位掌柜，您看到这件宝贝的话你会设置哪些竞价词呢？

淘宝直通车技巧篇：设置竞价词的思路首先，第一点，宝贝的名称词中我们可以用“风衣”这个竞价词。第二点，宝贝详情里面的属性词，我们可以用双排扣、韩版、淑女、绿色、长款等等作为竞价词。第三点，在宝贝名称和宝贝详情的组合词中，我们可以用韩版风衣，双排扣风衣等作为关键词。

When while as的区别和用法(综合整理)

When while as的区别和用法 when的用法当主句使用持续性动词时. Dave was eating,when the doorbell rang.门铃响时,大卫在吃饭. 2.一个动作紧接着另一个动作发生. When the lights went out, I lit some candles.灯灭了,我赶紧点上一些蜡烛. 3.谈论生命中的某一阶段,或过去的某段时间. His mother called him Robbie when he was a baby. 在他很小时,他妈妈叫他Robbin. 4.指"每一次" When I turn on the TV, smoke comes out the back. 每当我打开电视,就有烟从后面冒出. while/as 的用法从句多为进行时,而且为持续性动词. I'll look after the children while you are making dinner. 你做饭,我来照顾孩子. 注意事项: (1) “主短从长”型：主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用： He fell asleep when [while, as] he was reading. 他看书时睡着了。 Jim hurt his arm while［when，as］he was playing tennis. 吉姆打网球时把手臂扭伤了。 As［When，While］she was waiting for the train，she became very impatient. 她在等火车时，变得很不耐烦。 (2) “主长从长”型：若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不做声。但是，若主从句表示的两个同时进行的动作含有“一边…一边”之意思，通常用as：

拼多多直通车推广场景基础入门教程

开拼多多场景推广的话，首先要有基础销量，还要有个不错的转化率。场景推广是很容易产生爆款的，曝光也高，但前提是你对拼多多各方面有所了解、有一定推广基础才行。概说：首先，我们先弄明白拼多多场景推广的展示以及扣费规则：排名规则：综合排名=商品质量分广告出价。商品质量分=点击率转化率销量交易额。扣费规则：扣费=（下一位的出价*下一位的商品素材点击率）/自己的商品素材点击率+0.01元。单次点击扣费，重复点击虚假点击系统会过滤，不计扣费。定向： 1. 全体人群：所有普通用户 2. 访客重定向：浏览或购买过我的店内商品的用户。 3. 相似商品定向：浏览或购买过相似商品的用户。 4. 叶子类目定向：近期有推广商品所属叶子类目行为的用户。 5. 相似店铺定向：近期对我的店铺的竞品店铺感兴趣的用户。 6. 兴趣点：近期对我的商品相关属性感兴趣的用户。(最多设置5个定向点）。资源位： 1. 基础流量包：默认包含以下3个展示资源位 2. 类目商品页：推广商品将展示在拼多多商城类目标签页、搜索标签页下方的商品列表中 3. 商品详情页：推广商品将展示在拼多多商城商品详情页为你推荐下方的商品列表中（相似商品） 4. 营销活动页：推广商品将展示在拼多多营销活动页面下方的商品列表中，包括多多果园、边逛边赚、现金签到页、天天领现金、拼多多微信公众号； ---开始正题--- 一. 排名权重与优化： 1. 场景一样有排名权重区分的。如何获得一个号的排名，这个就需要针对商品做出一定的优化。并且要了解场景排名权重的核心环节。场景排名核心：场景计划权重--开设每一个计划都有一定的计划权重分，具体是按照改个计划内所有商品的质量分与投入计算所得。商品质量分--通俗的说法按照以下权重划分：点击率—转化率—产出—订单量—产出比。------这里面对于出价的标准就看你商品的质量分是否够高。上述两个点是最为基础并且最主要的两个核心，只要懂这些核心内容才能提高场景的排名。 2. 优化推广内容：计划以5天为一个优化周期，将所有定向与兴趣点5个选择，资源位全选；溢价标准以每个所需推广位置皆有曝光。分别记录每个的曝光量，点击数，点击率，订单量和投产比。5天结束后，记录下每日的点击率、转化率。横向对比你的点击率。根据记录的数据去分析，将曝光量大且点击数点击率高的组合开设一个新的计划。二．实操： 1. 将优化做好后，直接进入降低出价的步骤。上述说过排名权重的几个要点，其中我们需要注意的是点击率，这里因为有了上面的数据，

when,while,as引导时间状语从句的区别

when，while，as引导时间状语从句的区别 when，while，as显然都可以引导时间状语从句，但用法区别非常大。一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。 ①Why do you want a new job when youve got such a good one already？（get 为短暂性动词）你已经找到如此好的工作，为何还想再找新的？ ②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。 ③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。 ④The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while 和as从句的谓语动作必须是和主句谓语动作同时发生。 1．从句动作在主句动作前发生，只用when。 ①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。 ②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。 2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。 ①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。 ②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。 3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用as。这时，as常表示“随着……”；“一边……，一边……”之意。 ①As the time went on，the weather got worse．（as表示“随着……”之意） ②The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。 ③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。 ④The little girls sang as they went．小姑娘们一边走，一边唱。 ⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。 4．在将来时从句中，常用when，且从句须用一般时代替将来时。 ①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。 ②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。三、when用于表示“一……就……”的句型中（指过去的事情）。 sb．had hardly（＝scarcely）done sth．when．．．＝Hardly ／Scarcely had sb．done sth．when．．．

淘宝运营内部教程完整版-初级

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When, while, as的区别和用法

When, while, as的区别和用法版本一 (1) 若主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用： He fell asleep when [while, as] he was reading. 他看书时睡着了。【注】as 用于引出一个持续性动词表示“在……期间”时，其谓语通常只能是那些含有动作(action)和发展(development) 意味的动词，一般不能是那些不用于进行时态的动词(如be, seem, love, want, agree, see, know, have 等)，所以下面一句中的while 不能换为as： A：I’m going to the post office. 我要去邮局。 B：While you’re there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗? (2) 若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不做声。但是，若主从句表示的两个同时进行的动作含有“一边…一边”之意思，通常用as： She sang as she went along. 她边走边唱。 (3) 若从句是一个短暂性动作，主句是一个持续性动作，可用as / when 但不用while： It was raining hard when [as] we arrived. 我们到达时正下着大雨。 (4) 若主从句表示的是两个同时(或几乎同时)发生的短暂性动作，用as / when： I thought of it just when [as] you opened your mouth. 就在你要说的时候，我也想到了。 (5) 若要表示两个正在发展变化的情况，相当于汉语的“随着”，一般用as： Things are getting better and better as time goes on. 随着时间的推移，情况越来越好。 As it grew darker, it became colder. 天色越晚，天气越冷。 (6) 表示“每当…的时候”(暗示一种规律性)，一般要用when： It’s cold when it snows. 下雪时天冷。 He smiles when you praise him. 你夸奖他时他总是笑笑。 (7) 若主从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when： I will go home when he comes back. 他回来时，我就回家去。 (8) when 可用作并列连词，表示“这时(突然)”；while 也可以用作并列连词，表示“而”、“却”(表示对比)；但as 则没有类似用法： We were about to start when it began to rain. 我们正要出发，这时天开始下雨了。 He likes coffee, while she likes tea. 他喜欢咖啡，而她却喜欢茶。 (9) as 和when 后均可直接跟一个名词，构成省略句，但while 一般不这样用： As [When] a boy, he lived in Japan. 他小时候在日本。

直通车报告

直通车报告一、关于直通车概念想要做好直通车，就要先去了解现在直通车的定义，这块很容易被忽视，但若不说，很多“无知”的老板还是在看别人直通车如何如何做成的爆款，如何如何挣钱。停留在过去希望直通车打爆款丶直通车赚钱的年代。并不是说直通车现在打不了爆款赚不了钱，只是有这想法之前，要先明白自己提供什么产品。开车之前要做好哪些相应的准备。直通车的作用：现在的直通车只是点评运营手段之一，只是一个工具，但是他是使用最多的工具，现在的直通车更偏向与新品引流测款，在新店或者店铺效果不太好的适合，可以快速通过直通车提升店铺浏览。并且提升单品搜索关炎键词的排名。现在的直通车基本上每家淘宝店铺都在做，而且有特色的产品越来越多，所以现在的直通车更偏向于，让原先有销量基础的商品（所谓的爆款）销量更好。让没有销量的产品获得一定的流量。所以，在看待数据的时候需要更加理性客观。了解直通车在推广操作中所遇到的问题：直通车的问题基本上总结出来：展现量、点击率、点击单价、ROI、转换率以及相对无线端。大家都很清楚，无线的流量基本上能占店铺总流量的70%以上。大家对无线的需求也就越来越多。二、直通车的推广手段：很多人了解了直通车的皮毛，就开始希望能做好直通车，做不好了就会开始抱怨直通车太贵，淘宝赚不到钱。这种抱怨除了说服自己放弃直通车以外，解决不了任何问题。想了解直通车，先看看直通车的推广手段：关键词推广：流量精准、直击买家定向推广：流量大，点击单价低，相对来说ROI比较高（不适合新品）店铺推广：有门槛，费用低，流量精准性差三、选款有很多大神都有单独分析选款，之前也对选款做了一些分析。今天不做重点，主要提一些点给大家：产品自身基础： 1、价格 2、销量和评价（有一些基础评价，毕竟敢于第一个吃螃蟹的人终归是少数） 3、参谋分析：1. 宝贝在店铺中的流量趋势2. 转换率3. 收藏、加购等市场竞争力，市场趋势如果说宝贝的质量、价格、卖点上没有一项在同行中有竞争力，那么推广也只是为同行产品做广告而已。首先一定要对自己做的产品类目非常了解，清楚的知道同行产品有什么优势，然后确定自己的产品定位，是否有卖点更突出，或者性价比更高？在同行产品中一定要有优势才值得去开车付费推广。充足的货源，如果推广起来，之后因为缺货而终止了，那就实在是太可惜了。产品的利润空间，个人认为起码利润要在30%以上才比较适合开车，利润在30%那么ROI需要做到3.33以上才能保证直通车是盈亏平衡的一个状态。大家可以算一下自己的产品需要什么样的ROI 才能满足最基本的盈亏平衡。产品的质量，产品的质量要对得起这个价格，不然起步的情况下都是中差评，之后的推广将无法进行，买家不死傻子，不要想以次充好，产品的质量影响我们是否能长久的推广下去！四、上车准备 1. 详情页上车之前宝贝的详情页一定要做好充足的优化，详情页是影响宝贝转换的非常重要的因素，不然开车即使引入很好，很精准的流量不能造成转化，那也是白白浪费钱，时间和精力，尤其像现在无线端，一定要单独的去做一份。图片不需要很多，但是一定要清晰，加载速度够快。产品的卖点突出描写。让客户引起兴趣，抓住需求点，引导下单。关联营销，买家进店要充分的利用每一个买家，关联营销也很重要。 2. 宝贝优化

第七whenwhileas区别及练习

When while as 区别一、根据从句动作的持续性来区分 1、“主短从长”型：即主句是一个短暂性动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while ［ when， as］ he was playing tennis. 吉姆打网球时把手臂扭伤了。 2、“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，状态延续到从句所指的整个时间，此时通常要用while 。且强调主句动作或 I always listen to the radio while I ’ m driving. 我总是一边开车一边听收音机。 He didn ’ t ask me in; he kept me standing at the door while he read the message. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边,, 一边”之意时，则习惯上要用 as。如： He swung his arms as he walked. 他走路时摆动着手臂。 3、“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用as 或when，但不能用 while 。如： It was raining hard when [as] we arrived.我们到达时正下着大雨。二、根据主句与从句动作是否同时发生来区分 1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语 “一英语一般要用 as (也可用 when)。如： ,, 就的”意思，The ice cracked as [when] I stepped onto it. 我一踩冰就裂了。 2、若主句与从句表示的是两个几乎同时发生的短暂性动作，含有类似汉语“刚要“正要 ,, 却”的意思，英语一般要用 as(也可用 when)，且此时通常连用副词 ,, just。如：就” I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。三、根据是否具有伴随变化来区分若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用 when 或 while 。如： The room grew colder as the fire burnt down.随着炉火逐渐减弱，房间越来越冷。注：若不是引导从句，而是引出一个短语，则用with ，不用 as。如： With winter coming on, it ’ s time to buy warm clothes. 随着冬天到来，该买暖和衣裳了。四、根据从句动作的规律性来区分若暗示一种规律性，表示“每当,, 的时候”，英语一般要用when 。如：It ’s cold when it snows. 下雪时天冷。五、根据主从句动作的先后顺序来区分若主句与从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when 。