流化床反应器

流化床反应器fluidized bed reactor(FBR) :一种利用气体或液体通过颗粒状固体层而使固体颗粒处于悬浮运动状态，并进行气固相反应过程或液固相反应过程的反应器。

在用于气固系统时，又称沸腾床反应器。

流态化过程：当流体向上流过颗粒床层时，其运动状态是变化的。

流速较低时，颗粒静止不动，流体只在颗粒之间的缝隙中通过。

当流速增加到某一速度之后，颗粒不再由分布板所支持，而全部由流体的摩擦力所承托。

此时，对于单个颗粒来讲，它不再依靠与其他邻近颗粒的接触而维持它的空间位置，相反地，在失去了以前的机械支承后，每个颗粒可在床层中自由运动；就整个床层而言，具有了许多类似流体的性质。

这种状态就被称为流态化。

颗粒床层从静止状态转变为流态化时的最低速度，称为临界流化速度。

流化床的性质：（1）在任一高度的静压近似于在此高度以上单位床截面内固体颗粒的重量；（2）无论床层如何倾斜，床表面总是保持水平，床层的形状也保持容器的形状；（3）床内固体颗粒可以像流体一样从底部或侧面的孔口中排出；（4）密度高于床层表观密度的物体在床内会下沉，密度小的物体会浮在床面上；（5）床内颗粒混合良好，因此，当加热床层时，整个床层的温度基本均匀。

一般的液固流态化，颗粒均匀地分散于床层中，称之为“散式”流态化；一般的气固流态化，气体并不均匀地流过颗粒床层，一部分气体形成气泡经床层短路逸出，颗粒则被分成群体作湍流运动，床层中的空隙率随位置和时间的不同而变化，因此这种流态化称为“聚式”流态化。

与固定床反应器相比，流化床反应器的优点是：①可以实现固体物料的连续输入和输出；②流体和颗粒的运动使床层具有良好的传热性能，床层内部温度均匀，而且易于控制，特别适用于强放热反应。

但另一方面，由于返混严重，可对反应器的效率和反应的选择性带来一定影响。

再加上气固流化床中气泡的存在使得气固接触变差，导致气体反应得不完全。

因此，通常不宜用于要求单程转化率很高的反应。

此外，固体颗粒的磨损和气流中的粉尘夹带，也使流化床的应用受到一定限制。

为了限制返混，可采用多层流化床或在床内设置内部构件。

这样便可在床内建立起一定的浓度差或温度差。

此外，由于气体得到再分布，气固间的接触亦可有所改善。

近年来，细颗粒和高气速的湍流流化床及高速流化床均已有工业应用。

在气速高于颗粒夹带速度的条件下，通过固体的循环以维持床层，由于强化了气固两相间的接触，特别有利于相际传质阻力居重要地位的情况。

但另一方面由于大量的固体颗粒被气体夹带而出，需要进行分离并再循环返回床层，因此，对气固分离的要求也就很高了。

流化床法是美国联合碳化合物公司早年研发的多晶硅制备工艺技术。

该方法是以SiCl4、H2、HCl和工业硅为原料，在高温高压流化床内（沸腾床）生成SiHCl3，将SiHCl3再进一步歧化加氢反应生成SiH2Cl2，继而生成硅烷气。

制得的硅烷气通入加有小颗粒硅粉的流化床反应炉内进行连续热分解反应，生成粒状多晶硅产品。

由于在流化床反应炉内参与反应的硅表面积大，故该方法生产效率高、电耗低、成本低。

该方法的缺点是安全性较差，危险性较大，且产品的纯度也不高。

不过，它还是基本能满足太阳能电池生产的使用。

故该方法比较适合大规模生产太阳能级多晶硅。

技术应用目前采用该方法生产颗粒状多晶硅的公司主要有：挪威可再生能源公司（REC）、德国瓦克公司（Wacker）、美国HemLock和M E M C 公司等。

挪威R E C 公司是世界上惟一一家业务贯穿整个太阳能行业产业链的公司，是世界上最大的太阳能级多晶硅生产商。

该公司利用硅烷气为原料，采用流化床反应炉闭环工艺分解出颗粒状多晶硅，且基本上不产生副产品和废弃物。

这一特有专利技术使得R E C 在全球太阳能行业中处于独一无二的地位。

REC还积极致力于新型流化床反应器技术（FBR）的开发，该技术使多晶硅在流化床反应器中沉积，而不是在传统的热解沉积炉或西门子反应器中沉积，因而可极大地降低建厂投资和生产能耗。

在过去几年中，REC进行了该技术的试产。

2006年计划新建利用该技术生产太阳能级多晶硅的工厂，预计2008年达产，产能6500t。

此外，REC正积极开发流化床多晶硅沉积技术（Fluidized bed polysilicon deposition，预计2008年用于试产）和改良的西门子- 反应器技术（Modified Siemens-reactor technology）。

德国瓦克公司开发了一套全新的粒状多晶硅流体化反应器技术生产工艺。

该工艺基于流化床技术（以三氯硅烷为给料），已在两台实验反应堆中进行了工业化规模生产试验，瓦克公司最近投资了约2亿欧元，在德国博格豪森建立新的超纯太阳能多晶硅工厂，年生产能力为2500t，加上其它扩建措施，新工厂的投产将使瓦克公司在2008年达到9000t的年生产能力，最终于2010年达到11 500t的产能。

另外，美国Hemlock公司将开设实验性颗粒硅生产线来降低硅的成本，Helmlock公司计划在2010年将产能提高至19 000t。

MEMC 公司则计划在2010年底其产能达到7000t左右。

Efficiency Leaders in Crystalline Silicon PVWe profile the firms that stand at the forefront of crystalline silicon efficiency, and put their plans and products under the microscope.So much attention gets focused on thin film around these here parts that it's easy to forget that crystalline silicon (c-Si) PV still makes up more than three-fourths of the module market (for more details on this, you can find our free research note on 2009 cell and module production here). To some extent, this is understandable: the obvious exception of CdTe-producer-that-shall-not-be-named aside, thin film is still very much a work in progress as regards commercialization, with much scope for future technological and economic improvement; c-Si, on the other hand, is considered a mature and well-understood (read: boring) technology, with only incremental improvements in cost and efficiency expected over the coming years. And of course, Davids are far more interesting than Goliaths.It is generally true that efficiencies for most c-Si firms have registered only incremental gains over the past few years; however, amongst this large mass ofrelatively undifferentiated firms, a small handful of players are attempting to drive step-function improvements in cell efficiency. While some of these firms have been ahead of the rest of the pack for years, the initiatives of others are still in early-stage commercialization. Besides the bragging rights and distinctiveness they confer, efficiency improvements also drive reductions in cost, both on the module manufacturing and the BOS fronts, although the R&D spend required to maintain improvements is not insignificant, and higher efficiency cell configurations can be more expensive to manufacture. Below, we profile the firms that stand at the forefront of crystalline silicon efficiency, both now and looking to the future, and put their efficiency initiatives under the microscope.1. SunPowerTechnology: All-back contact monocrystallineHigh-Efficiency Product Status: Volume production (2009: 398 MW)Commercialized Cell Efficiency: 22%SunPower has been the heavyweight champion of the world when it comes to commercialized cell and module efficiencies for the last half-decade, and by some measure. The company's back-contact cell design, in commercial production since 2005, moves the metal contacts to the back of the wafer, maximizes the working cell area, and eliminates redundant wires (for details, see this). Impressively, SunPower has been able to achieve consistent improvements in efficiency with each successive generation of commercialized cells, and this has translated to gains in the module arena as well. Its Gen 2 cells, currently in high-volume production, have an efficiency of 22%. Further improvements are on the way: Gen 3 cells, which reportedly have already started shipping, have efficiencies in excess of 23%.The Verdict: As Gen 3 rolls out and exceeds efficiencies of 24% (something the company has already achieved in low volume), SunPower is likely to be the efficiency leader when it comes to high-volume PV cells and modules for the foreseeable future. The problem, as this article by Michael Kanellos points out, is that 24% is awfully close to the realistic ceiling, meaning there may not be much further to go from there. As the other firms on this list start to narrow the difference, the company's price premium will erode, and its high cost structure will come under increased scrutiny. SunPower has already recognized this, and has aimed at what seems to be a realistic target of $1/W by 2014. Whether this will be enough to survive in a commoditized world of low-cost Chinese manufacturing remains to be seen. Fortunately for the firm, though, its downstream business does afford it some measure of insulation.2. SanyoTechnology: Heterojunction with Intrinsic Thin Film (HIT)High-Efficiency Product Status: Volume production (2009: 255 MW)Commercialized Cell Efficiency: 19.8%Ahead of the rest, but a distant second behind SunPower, Sanyo's high-efficiency product has been in volume production for quite some time -- since way back in 1997, to be exact. Its proprietary HIT cell is a hybrid of monocrystalline silicon surrounded by ultra-thin amorphous silicon layers (see here for details). The amorphous silicon layer enables superior temperature characteristics and low light performance compared to standard crystalline silicon technology. Continuous improvements have led to best commercialized cell efficiencies of 19.8% (launched this year), compared to 18.4% six years ago.The Verdict: Sanyo has the same basic problem as SunPower: HIT costs considerably more to manufacture than standard c-Si. At the same time, its cells are about two percent less efficient than SunPower's, which means the cost pressure is significantly more. Sanyo should continue to hold the number-two spot as regards commercial efficiency over the next three years, but unless it can start driving step-function improvements in either cost or efficiency, this will matter less and less in the commoditized global market. The company will, however, enjoy a competitive advantage in its home country of Japan, where residential systems dominate and space constraints mean that there will always be a preference for higher efficiency products. Additionally, the company is banking on the success of specialty products (e.g., BIPV modules, combined module-battery packs) in less price-sensitive markets going forward to ensure demand.3. SunivaTechnology: ARTisun monocrystallineHigh-Efficiency Product Status: Volume production (2009: 16 MW)Commercialized Cell Efficiency: 18.3%The brainchild of PV pioneer Dr. Ajit Rohatgi, a Georgia Tech scientist, Suniva began commercial production of its monocrystalline cells in late 2008. Unlike many struggling PV startups that entered the market around that time, the company has gone from strength to strength over the last 18 months. It has exhibited one of the quickest production ramps of any Western PV company, going from an initial 32 MW to 96 MW to a current 170 MW of cell capacity, and is sold out for 2010. By its own admission, Suniva's technology does not represent a radical innovation; rather, the company has its own paste and texture recipes, is able to customize and optimize every layer of the cell design to its own specifications, and has leveraged its considerable R&D experience to optimize each processing step to a high degree.The Verdict: While Suniva is clearly not going to overtake SunPower or Sanyo any time soon, reports suggest that the company has a much better cost structure compared to these two players, one that is more in line with low-cost manufacturers. That, combined with its current efficiency advantage over other firms, makes it competitively positioned for right now. A 19% efficiency cell is in the works and should maintain competitiveness in the near future as well. The key question is whether the company can maintain this advantage going forward, given that major Chinese players are hell-bent on playing catch-up (see below). Moreover, the company does not really have a differentiated technology that can guarantee this.4. Suntech PowerTechnology: Pluto monocrystallineHigh-efficiency Product Status: Low volume (2010 run rate of 4 MW per month)Commercialized Cell Efficiency: 19%The Chinese cell/module behemoth threw its hat into the next-gen c-Si ring in spring 2009, when it announced the development of its proprietary "Pluto" technology, which can be used to retrofit existing cell lines. The Pluto design is based on the PERL (passivated emitter with rear locally diffused) technology developed at Australia's University of New South Wales, where efficiencies of 25 percent have been achieved in the laboratory. Unique texturing technology with lower reflectivity ensures more sunlight can be absorbed throughout the day even without direct solar radiation, and thinner metal lines on the top surface reduce shading loss. Average cell efficiencies in low-volume production were 19%, with plans to hit 20% in two years. The company aimed to reach 450 MW of Pluto capacity by mid-2010, and envisioned that Pluto would eventually become its core product over time.The Verdict: At 19%, Pluto would place Suntech behind only SunPower and Sanyo in the efficiency stakes. Importantly, Pluto's offers higher efficiency with the potential to simultaneously lower costs: as this GTM article outlined, the cells are made with copper, rather than more expensive silver paste contacts. Pluto thus holds the key to global domination for Suntech. Unfortunately, the company has had trouble ramping production beyond its current levels of 4 MW per month, which it describes as "glitches" with the process flow (see this article for a detailed explanation). Although it is too early to be certain, one is inclined to think that the snags will eventually be resolved; the question is more 'when' than 'if'. Too long, and Suntech runs the risk of lagging behind its Chinese brethren (Yingli and Trina, see below) on both cost (which it already does) as well as efficiency, and facing heated competition from less differentiated Chinese manufacturers (Eging PV, Ningbo, Neo Solar).5. Trina SolarTechnology: Quad Max square monocrystallineHigh-efficiency Product Status: Development (first shipments expected Q3 2010)Commercialized Cell Efficiency: 18.1% (pilot)Trina's new cell tries to avoid cutting corners, quite literally -- Quad Max's square shape allows it to harvest more sunlight by avoiding surface area loss typical with traditional monocrystalline cells, which are octagonal-shaped (also known as "pseudo-square"). In a 72-cell module, the additional active surface area translates into a power output advantage of eight percent. The company has developed a new process for the technology, which involves two high-temperature thermal processes, an additional printing and cleaning step, and usage of special paste for the cell surface. Initial shipments are expected in the third quarter of 2010, but don't expect meaningful megawatts until 2011.The Verdict: "True" square mono has been a talking point in the industry for a number of years without anything to show for it. Trina's move is therefore a much-needed step in the right direction. At 18.1% efficiency, though, it places Trina at the bottom of the pack as far as high-efficiency initiatives are concerned. This will matter less as long as Quad Max does not represent a meaningful increase in manufacturing costs, since Trina is currently the second cheapest manufacturer of c-Si PV in the world, and Quad would drive a 0.6% increase in module efficiency, which would boost product margins. It is still early days for the technology, though: as Suntech's example shows, there is potential for problems galore when going from low- to high-volume production.6. Yingli SolarTechnology: PANDA N-type monocrystallineHigh-efficiency Product Status: Pilot (commercial launch in Q3 2010)Best Commercialized Cell Efficiency: 18.5% (pilot)Yingli's foray into the world of high-efficiency cell technology has come courtesy of a three-way research collaboration with the Energy Research Center of the Netherlands (ECN) and process tool maker Amtech Systems, announced in June 2009. PANDA uses ECN's design, the solar diffusion technology and dry phosphosilicate glass (PSG) removal expertise of Amtech's Tempress Systems subsidiary, and Yingli's process technology. The PANDA cell is N-type (for more on that, see here), whichmeans it has greater impurity tolerance and does not suffer from the light-induced degradation that conventional P-type cells do. Yingli claims the corresponding module will also have better performance under high-temperature and low-light conditions. Plans for PANDA are aggressive: in March 2010, the company announced it would construct 300 MW of ingots, wafers, cells and module capacity by the end of the year, and first shipments are expected by the end of October.The Verdict: As with Trina, Yingli has a ways to go as far as commercial ramp-up of PANDA is concerned, but average cell efficiencies of 18.5% in pilot production are comfortably above Quad Max's 18.1%, although comfortably behind Pluto's 19%. Given N-type's higher impurity tolerance, PANDA also gives Yingli the option of using lower quality (and thus cheaper) polysilicon for its cells, which confers a direct cost advantage. This would further cement the firm's position as the lowest-cost c-Si manufacturer in the world and make life very difficult for its competitors indeed. And with a $5.3 billion loan in hand, the company has some cash to burn before it gets the recipe right.7. JA SolarTechnology: SECIUM nanoparticle inkHigh-efficiency Product Status: Pilot (production began May 2010; commercial production expected H2 2010)Best Commercialized Cell Efficiency: 18.9% (pilot)The secret sauce in JA Solar's high-efficiency cell comes by way of California startup Innovalight, which manufactures a proprietary nanotechnology-based silicon ink and licenses a process which allows a simple upgrade to cell lines to boost efficiency - currently by a full percentage point. Importantly, the modification to the production line is relatively simple, requiring only one additional step: the ink is applied using the screen-printing technology typically used by semiconductor lines during back-end metallization. Pilot production is already underway and first commercial shipments are expected any time soon.The Verdict: Unlike the other firms discussed here, most of which only sell modules, the bulk of JA Solar's business comes from cell sales, which means it is not a direct competitor to them. Success with SECIUM would place JA head and shoulders above other pure-play cell firms in terms of efficiency; only Suniva would come close. And there is potential for further upside -- as discussed in this GTM article, the ink-aided efficiency bump could double to two percent in 2011. Since JA is already the cost leader in cell manufacturing, SECIUM (if ramped up to volume successfully) could provide it pole position on both cost and efficiency fronts. There are two caveats: one, the incremental cost better not outweigh the efficiency gains, and two, nothingreally stops other firms from jumping onto the silicon ink bandwagon at a later point -- indeed, as of January 2010, Innovalight claimed it had lined up five other customers*.That each of these seven firms is employing a different approach to commercializing high-efficiency products should dispel notions that we have reached the end of the road as concerns technological progress in crystalline silicon manufacturing. As with the larger question of PV absorber materials, there is a long way to go before the dust will truly settle on which variant(s) of c-Si will emerge as the dominant leader in the space, if any. There is still much room -- and reward -- for innovation.单质硅的一种形态，为棕黑色或灰黑色的微晶体。