Abstract:
A Method for Improving the efficiency of a silicon purification process is by controlling the temperature and composition of the effluent to a feedstock recovery composition and temperature, rapidly quenching the effluent at or near the recovery composition, separating the gases from the liquids, sending the gases to conventional hydrogen recovery and recycle facilities, separating the hydrohalosilanes from silicon tetrahalide, returning the hydrohalosilanes to the inlet of the deposition reactor, using all or some of the silicon tetrahalide to control the composition and temperature of the effluent and separately heating the hydrogen and any silicon tetrahalide returned to the decomposition reactor to a temperature greater than 400 C. and separately injecting them into the decomposition reactor.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of silicon purification, and more particularly to a method for improving the efficiency of such a silicon purification process 
     The production of high purity electronic grade silicon is the critical first step of the entire multi-billion dollar semi-conductor industry. The basic process consists of three steps; conversion of metallurgical grade silicon into a hydrohalosilane such as trichlorosilane, purification of this material by distillation and other means, and decomposition of the material back to silicon. 
     There are two established ways to produce the hydrohalosilane; a low temperature (300-400 C.) low pressure (1-5 atm) high yield (90%) process using a hydrohalide, such as hydrogen chloride; and a high temperature (400-500 C.) high pressure (30-40 atm) low yield (12-24% depending on catalyst and conditions) process using silicon plus hydrogen to hydrogenate a silicon tetrahalide such as silicon tetrachloride. 
     The hydrohalide process was invented by Siemens and is used by the majority of the silicon producers; the hydrogenation process was invented by Union Carbide and is used in two facilities as part of their silane process. 
     The following equations show the desired reactions for the two processes but as noted above reaction 1 has a much higher yield 
     
       
         Si+3HCl→SiHCl 3 +2H 2  Hydrohalide process  1 
       
     
     
       
         Si+3SiCl4+2H 2 →4SiHCl 3  Silicon tetrachloride hydrogenation  2 
       
     
     Purification is normally done by distillation, but reactive distillation is also used, as is adsorption. In most facilities there is extensive recycle and purification of hydrogen. Three facilities produce silicon hydride or silane, two from the hydrohalosilane by disproportionation (Union Carbide Process) and one from silicon tetrafluoride by reduction via aluminum hydride (Ethyl Process). 
     The decomposition reactors are all rod reactors except for fluid bed reactors operated on silane as part of the Ethyl Process. Fluid bed reactors have significant capital, operating and energy advantages but have proved difficult to implement. The only operating fluid bed units produce a dusty product contaminated with hydrogen that is not widely accepted. 
     There are two decomposition reactions for hydrohalosilanes; thermal decomposition and hydrogen reduction. (Trichlorosilane is used in the examples but bromine or iodine can be substituted for chlorine, fluorine cannot) 
     
       
         4SiHCl 3 →Si+3SiCl4+2H2  (thermal) 
       
     
     
       
         SiHCl 3 +2H 2 →Si+3HCl  (hydrogen reduction) 
       
     
     All halosilane reactors incorporate both and consequently produce an effluent, which has a range of silicon hydrohalides and tetrahalides and hydrogen halides and hydrogen. 
     The essence of the process is impure silicon in, pure silicon out plus small impurity streams. To accomplish this there are large recycle streams of hydrogen, silicon and halide containing streams and is important not to produce low value by-products or waste streams. 
     The key problem is the silicon tetrahalide, which is difficult to convert to silicon, and thus causes a difficult problem in closing the plant silicon and chlorine balances without large waste streams. In the preferred hydrohalide reaction process the silicon tetrahalide is also produced albeit in small quantities (4-5%). Thus there is a net production of silicon tetrahalide as a byproduct. Most plants try to minimize this byproduct production and then convert what they have to fumed silica, which is not as valuable as electronic grade silicon but enables recovery of the hydrogen halide for reuse. The Union Carbide hydrogenation of silicon tetrahalide was invented to overcome this problem but is an expensive and dangerous solution (one accident and two fatalities have been reported to date). Another approach was taken by Wacker-Chemie as is shown in the U.S. Pat. No. 4,454,104 by Griesshammer where silicon tetrachloride is reacted with hydrogen in a reactor parallel to the deposition reactor. The effluent from both reactors are then mixed and compressed to 8 bar and cooled to −60 C. in order to force the hydrogen chloride into solution and allow separation of the hydrogen. No mention is made in this patent of the benefits of controlling the temperature of the effluent or of quenching the reaction. 
     In a recent patent U.S. Pat. No. 5,910,295 by de Luca a closed loop process is proposed which combines the Union Carbide approach of producing silane by disproportionation with the Siemens approach of producing trichlorosilane from hydrogen chloride at high yield. The solution is to react the excess silicon tetrachloride with hydrogen and oxygen. The overall silicon production reaction is simply the thermal decomposition of trichlorosilane to silicon and silicon tetrachloride. The excess silicon tetrachloride is then oxidized with hydrogen and oxygen which chemically is the same as reacting with water. 
     
       
         4SiHCl 3 →SiH4+3SiCl4 
       
     
     
       
         SiCl 4 +2H 2 O→SiO 2 +4HCl 
       
     
     Thus 3 moles of fumed silica are produced for every mole of silicon produced. Thus the trichlorosilane production reactors and purification processes must be four times larger than if all the silicon in the trichlorosilane were converted to silicon. The increased capacity of the above process is used to make fumed silica, which is a much less valuable product and does not require the high purification levels that the electronic grade silicon product does. Other silicon production processes make great efforts to promote the hydrogen reduction reaction because it produces more silicon from a mole of trichlorosilane. 
     
       
         SiHCl 3 +2H 2 →Si+3HCl 
       
     
     Such efforts typically include running the reactor at higher temperatures (1100 C.) than needed for thermal decomposition (850 C.) and recycling silicon tetrachloride and hydrogen to the reactor until the silicon tetrachloride is consumed. All practical plants also convert some product to fumed silica either as a means of disposing of contaminated material or as a byproduct for sale. For an overall optimum facility one would want to have the flexibility of producing the desired product slate of silicon and amorphous silica depending on market conditions. Such optima depend on the market demand and pricing for the products together with the marginal production cost and equipment capability and can be optimized using linear programming techniques, as is done in oil refining, providing the equipment has some flexibility. 
     There have been a number of patents for silicon deposition reactors; the key rod reactor patent is the U.S. Pat. No. 3,041,14 by Schering. U.S. Pat. No. 4,092,446 by Padovani describes an optimized system using a fluid bed and extensive recycle of materials. U.S. Pat. Nos. 5,798,137 and 5,810,934 by Lord describe a fluid bed capable of operating with or without recycle on a variety of feedstock. Various fluid bed patents describe methods of operating and of heating. U.S. Pat. No. 5,374,412 by Kim et al. describe use of two feed streams one of which is used to prevent wall deposition which would block the passage of the microwaves used for heating the beads. 
     All these systems take the effluent from the decomposition reactor as it is cooled down and removed from the reactor and then separate and recycle the components. 
     The primary deficiency in the prior technology is that it neglects the opportunities in the temperature regime between the deposition temperature which is typically between 750 and 1150 C. and the condensation temperature of the halosilanes in the effluent which are typically below room temperature. The effluent gases are allowed to cool and continue to react through this large temperature range thus producing more of the undesired silicon tetrahalide. 
     In this range the species in the effluent change composition with temperature and there is always an optimum temperature for recovery of the desired components which is typically 800-1000 C. At this temperature the desired hydrohalosilanes such as trichlorosilane and dichlorosilane are at or near a maximum and thus can be recovered which has great impact on the overall silicon and chlorine balance. 
     Thus, because of this deficiency the reactors must operate hotter and with greater hydrogen recycle to try and convert the undesired silicon tetrachloride. This in turn results in lower silicon production, more difficult materials problems and greater energy requirements. 
     A further deficiency is that the opportunities to change the composition of the effluent gases so as to recover more of the valuable hydrohalosilane feedstock are also neglected. The current approach of recycling a reaction byproduct (silicon tetrachloride) to the decomposition reactor results in decreased in production of that product but also results in decreased production of the desired product. The alternate approach, used by Griesshammer, of a parallel reactor reducing silicon tetrachloride with hydrogen converts a small percentage, 10%, of the silicon tetrachloride, requires heating both streams, does not promote silicon production, and significantly lowers the trichlorosilane to silicon tetrachloride ratio in the effluent. [This dilution of the feedstock is desirable for the Griesshammer patent as it improves the solubility of the hydrogen chloride but it increases the cost of the later separation.] 
     A further deficiency of the present processes is that the reactor does not have much flexibility in consumption of silicon tetrachloride so the byproduct silicon tetrahalide must be used to make fumed silica even if the market demand is not present. 
     This problem becomes more acute with the use of fluid bed reactors because they are more susceptible to materials problems as the silicon product is in physical contact with the wall, which thus must be at or close to the deposition temperature. This requires hot walls in contrast to the rod reactors, which typically have cooled walls. Furthermore fluid bed reactors do not have the internal heat generation provided by the electrical heating of the rod in rod reactors and so must add heat in some other way. If this heat is added through the walls, the walls must be hotter than the silicon product. U.S. Pat. No. 4,207,360 to Padovani described one solution to this problem, which was to use a graphite lining coated with silicon carbide. Unfortunately this material contaminated the silicon produced with carbon and thus the process failed commercially as the silicon could not sold. Lord points out that the use of silicon oxide is preferred because of its purity and cost and it has some temperature limitations. A further problem is that the materials coming into the reactor can only be preheated to a temperature below their thermal decomposition temperature which is 350-450 C. for most feedstock materials. For high throughput fluid bed reactors putting in the additional heat to bring the temperature up to the desired decomposition temperature of greater than 800 C. is very difficult. Lord suggests use of laser and/or chlorine heating in conjunction with microwaves. Heating the reactor up to the even higher temperatures needed to convert silicon tetrahalides make this problem even worse. Operating at lower temperatures (600-700 C.) as is done in U.S. Pat. No. 4,784,840 requires low deposition rates and results in dusty product contaminated with hydrogen thus requiring post treatment as described in U.S. Pat. No. 5,242,671. A further disadvantage of the prior technology is that the high temperatures used cause formation of silicon dichloride SiCl 2  monomer which condenses and polymerizes on the walls of the effluent piping to form explosive solids such as Si 2 Cl 6 , Si 3 Cl 8  and Si 4 Cl 8 . One approach to resolving this problem is the injection of chlorine or hydrogen chloride in the effluent piping as suggested by Lord. The present technology encourages the reaction of such monomers to form useful products and by keeping the walls of the recovery reactor warm discourages condensation of these species. The selection of optimum recovery temperature can take into account formation of these polymers and thus it may be more optimal to select a lower temperature than would be the case otherwise in order to reduce the operational problems. 
     SUMMARY OF THE INVENTION 
     The primary object of the invention is to increase the overall efficiency of processes for the production of high purity silicon. 
     Another object of the invention is to recover the maximum amount of valuable feedstock. 
     Another object of the invention is to reduce unwanted byproducts. 
     A further object of the invention is to make it easier to use fluid bed reactors. 
     Yet another object of the invention is to simplify the retrofit of fluid bed reactors for rod reactors. 
     Still yet another object of the invention is to use the cheaper hydrohalide reaction for halosilane production. 
     Yet another further object is to improve the quality of product produced by fluid bed reactors 
     In accordance with a preferred embodiment of the present invention, a method for improving the efficiency of a silicon purification process comprises the steps of controlling the temperature and composition of the effluent to an optimum feedstock recovery composition and temperature, rapidly quenching the effluent at or near the recovery composition, separating the gases from the liquids, sending the gases to conventional hydrogen recovery and recycle facilities, separating the hydrohalosilanes from silicon tetrahalide, returning the hydrohalosilanes to the inlet of the deposition reactor and using at least some of the silicon tetrahalide to control the composition and temperature of the effluent and separately heating and injecting the hydrogen and silicon tetrahalide feed streams to the deposition reactor to a temperature above 350 C. 
     In the proposed invention all or some of the silicon tetrachloride bypasses the deposition reactor to the recovery reactor while all the hydrogen goes through the deposition reactor thus improving the yield of the hydrogen reduction reaction. This results in increased yield in the deposition reactor, a reduced flow to the deposition reactor and an increased recovery of feedstock. Combining the two improvements of controlling the temperature and the composition of the effluent also results in equipment and energy savings as the added silicon tetrachloride can be used to cool the effluent and hence does not itself require to be heated to the recovery reactor temperature. 
     Other objects and advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
     FIG. 1 is a schematic diagram illustrating the portion of the invention concerning the recovery of hydrogen and silicon containing feedstock by, in FIG. 1 a , controlling the temperature then quenching to preserve the recovered feedstock and showing the preferred embodiment of controlling the temperature and composition by adding a further reactant to the recovery reactor in FIG. 1 b.    
     FIG. 2 is a schematic diagram with FIG. 2 a  illustrating the portion of the invention concerning the use of three separate feed streams, each of which has different composition and consequently different temperature tolerance, to provide all or most of the needed reaction heat and FIG. 2 b  showing the preferred embodiment where all or some of the STC is added to the recovery reactor. 
     FIGS. 3 a  and  3   b  are schematic diagrams each illustrating one way in which the concepts of the invention shown in FIGS. 1 &amp; 2 can be combined into a complete reactor system which provides significant benefits. 
     FIG. 4 is a comparison of the prior art flow diagram with and without the invention, FIG. 4 a  is a copy of a process flow diagram from a prior patent (FIG. 5 from U.S. Pat. No. 4,092,446 by Padovani) and FIG. 4 b  is the same system modified with the proposed invention. 
     FIG. 5 is a detailed schematic for the new process as implemented in FIG. 4 b  above with the same stream numbering system. 
     FIG. 6 is a graph showing the change in molecular composition with temperature in the recovery reactor after addition of the silicon tetrachloride for the flows shown in Table 1 for the stream numbers shown in the schematics FIGS. 4 a  &amp;  4   b.    
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     In order to produce high purity silicon suitable for use in semi-conductor or photovoltaic applications it is necessary to form and purify a liquid or gaseous silicon containing material then decompose that material back to solid silicon. Processes to do this have been patented using materials that contain silicon and hydrogen and/or a halogen such as chlorine, bromine or iodine. Such materials include silane, trichlorosilane, dichlorosilane, silicon tetrachloride, tribromosilane etc. It is also common to include a diluent, which may partake in the reaction such as hydrogen, or be inert such as argon. The addition of an inert is usually done to add heat or improve fluidization and inerts can be added to any of the reactant streams without changing the basic process. 
     This particular process can be applied to all of the previously patented processes providing that the process is applied correctly so as to make recovery of a feedstock material feasible. In particular the silane decomposition process is inherently irreversible but it is possible to recover the feedstock used to make the silane by adding additional halogen containing materials. This is an optional but preferred step for the halosilane decomposition processes while it is required for decomposition processes using silane. 
     A more detailed description of each figure is as follows 
     FIGS. 1 a  and  1   b  are schematic diagrams illustrating the portion of the invention concerning the recovery of hydrogen and silicon containing feedstock. In both figures, reactants, stream  101 , at a temperature T 1  and composition C 1  enter silicon deposition reactor,  1 , where they are heated to temperature T 2  and react to deposit silicon, stream  103 , and effluent gases Stream  104  with composition C 2  and temperature T 2 . The stream  104  enters the recovery reactor  2  where it is cooled to temperature T 3  and reacts to reform the desired feedstock. This stream,  104 , exits the recovery reactor and enters the rapid quencher,  3 , where the gases are cooled rapidly to prevent decomposition of the newly reformed feedstock. The stream  105  comprises the material leaving the rapid quencher at temperature T 3  that is too low for further reaction and with the desired composition C 2 . These stabilized gases and or liquids may then be treated for further recycle by a variety of means, examples of which are shown in FIG.  3 . In FIG. 1 b  the preferred embodiment is shown with additional stream  106  entering the recovery reactor to control the composition. This stream can have any desired composition, including hydrogen, inerts, halosilanes and halohydrides and may consist of multiple streams mixed in the recovery reactor. 
     FIGS. 2 a  and  2   b  are schematic diagrams illustrating the portion of the invention concerning the use of three separate feed streams, each of which has different composition and consequently different temperature tolerance, to provide all or most of the needed reaction heat. In both figures, stream  101  has a composition C 1 , which is predominantly hydrogen and thus does not decompose to form silicon and thus can have any temperature T 1 . Stream  102  has a composition C 2 , which is primarily silicon tetrahalide and thus does not decompose to form silicon in the absence of hydrogen and can have any temperature T 2 . Stream  103  is the feedstock makeup stream and has a composition C 3 , which is primarily silicon hydrogen halides and thus will decompose to form silicon at temperatures above temperature T 3  and hence cannot exceed this temperature. The reactor operates at a temperature T 4  that is greater than T 3 . For an improved heat balance it is beneficial if temperatures T 1  and T 2  are higher than temperature T 3  and preferably higher than T 4 . Thus the heat supplied by streams  101  and  102  can offset all or some of the heat required to maintain the reaction temperature T 4  even though the feedstock stream  103  enters the reactor significantly cooler than the reactor temperature. In FIG. 2 b  the preferred embodiment is shown with additional stream  106  entering the recovery reactor to control the composition and this stream is preferably some or all of the silicon tetrachloride (STC) available. A portion of the available STC may be sent to the decomposition reactor for other purposes than improving the decomposition efficiency such as improving the heat balance or providing additional fluidizing gas as shown in stream  203 . 
     FIGS. 3 a  and  b  are schematic diagrams illustrating ways in which the concepts of the invention shown in FIGS. 1 &amp; 2 can be combined into a complete reactor system, which provides significant benefits. In both figures, the silicon feedstock stream,  301 , is mixed with the recycle stream  317  to form reactor feed stream,  319 , which is heated in the TCS heater and fed to the reactor at a temperature below its thermal decomposition temperature. The hydrogen feedstock stream,  302 , is mixed with the recycle stream  313  to form reactor feed stream,  320 , heated in the hydrogen heater and preferably fed to the reactor at a temperature above the reactor temperature. In the reactor,  303 , these streams mix with some or all of recycle stream  318 , which is fed to the reactor at a temperature above the reactor temperature. Thus the heat supplied by streams  320  and  318  can offset all or some of the heat required to maintain the reaction temperature T 4  even though the feedstock stream  319  enters the reactor significantly cooler than the reactor temperature. The silicon product leaves the reactor as Stream  304 . 
     The stream  305  enters the recovery reactor  306  where it is preferably combined with stream  325  (consisting of all or some of the STC stream  318 ), cooled and reacts to reform the desired feedstock. This stream,  307 , exits the recovery reactor and enters the rapid quencher,  308 , where the gases are cooled rapidly to prevent decomposition of the newly reformed feedstock. The stabilized gases,  309 , exiting the quench are then cooled further in the gas-liquid separator,  310 , to condense most of the silicon containing species and the condensed liquids,  311 , are separated from the uncondensed gases,  310 . In FIG. 3 a  these gases which are primarily hydrogen and hydrogen halides are further treated in a gas separator,  312 , to provide a stream,  313 , that is primarily hydrogen and a stream,  314 , that contains most of the hydrogen halide. This gas separator can be a cryogenic device, an absorption or adsorption device, a membrane device or any combination thereof. The liquid stream,  315 , is then processed in a liquid separator into a stream,  317  which is primarily silicon hydrogen halides and a stream,  318 , which is substantially free of silicon hydrogen halides. Such a separator will typically be a distillation column but any techniques are suitable which will provide good separation. The required degree of removal of hydrohalosilanes, such as dichlorosilane or trichlorosilane from the tetrahalide stream depends on whether the tetrahalide stream will be heated to such a temperature where silicon might form. In the preferred embodiment this entire stream is sent to the recovery reactor at low temperature thus some contamination with hydrohalosilanes is not an operational problem but only an economic problem. If some of this stream is to be heated above the thermal decomposition temperature of the hydrohalosilanes then there must be insufficient hydrohalosilanes in the stream to cause operational problems due to the formation of silicon by thermal decomposition. FIG. 3 b  represents an alternative approach where gas exiting the top of  310  is primarily hydrogen and the hydrogen chloride is dissolved in the liquid chlorosilanes and is then removed in a further gas liquid separator. Preferably both gas/liquid separators are distillation columns and the benefits and Griesshammer describes requirements of this approach in U.S. Pat. No. 4,454,104, incorporated herein by reference. 
     FIG. 4 shows how this system may be beneficially integrated into an overall silicon purification facility. There are many ways of obtaining such an overall system but the basic principles of production, purification, deposition and recycle must be followed. For the purposes of comparison to prior technology, FIG. 4 is based on FIG. 5 from Padovani as shown in the original form in FIG. 4 a . In FIG. 4 b  the recycle stream  7  is rerouted to the vaporizer, a quench unit is added between the deposition reactor and the recycle unit and stream  8  is changed to a stream which comes from the vaporizer directly to the quench unit. The quench unit consists of the recovery reactor and quench/degasser column described in FIG. 6 which is based on the concepts of FIGS. 1,  2  &amp;  3 . The vaporizer is changed to a distillation column capable of separating out the blowdown stream  10  and recycle stream  8  as silicon halide streams with only small, (0.1%), amounts of silicon hydrogen halides. For ease in comparison the hydrogen streams are shown combined with the silicon halide stream in stream  16 . Preferentially the hydrogen streams  20  and  22  would enter the reactor separately at a temperature higher than the reaction temperature as shown in FIG.  6 . 
     FIG. 4 a  is described in detail in Padovani, incorporated herein by reference, and the Figure is taken directly from Padovani with the same numbering system. In Padovani there is no attempt to control conditions so as to recover feedstock, maintain the purity of the effluent, provide for more than one stream to the reactor or bypass the reactor with a silicon halide stream. 
     FIG. 5 shows the details of how the new process is implemented in FIG. 4 b  to provide the mass balance shown in Table 1 under improved process and the heat balance at the entry to the deposition and recovery reactors as shown in Tables 2 and 3, respectively. 
     The stream numbers are the same as in FIG.  4 . The hydrogen streams  20  and  22  are combined then heated in hydrogen heater,  1 , to a temperature between 1300-1600 C. before entering the deposition reactor through an inlet separate from that used for the remainder of the reacting flows which are heated to a temperature of 350 C. The two components of stream  16  do not meet until inside the reactor to avoid premature decomposition of the silicon containing materials. The resulting heat balances are shown in Table 2. Heating the hydrogen to 1300 C. results in a temperature of 845 C. inside the reactor, heating to 1600 C. results in a temperature of 1102 C. in the reactor under adiabatic conditions. In section B of Table 2 the heat required to raise the reactor temperature to 1100 C. is calculated as 272 Kilowatts for 50% efficient heaters. It is clear to one knowledgeable in the art that many combinations of hot hydrogen temperature and flowrate may be combined with heater input to obtain the desired operating temperature conditions in the reactor. The silicon is deposited and removed as stream  17 . The effluent gases leave the reactor at the reactor temperature of 1100 C. and enter the recovery reactor, where they mix with the recycled Silicon tetrachloride stream,  8 , and react and cool to the chosen recovery temperature (shown as 912 C.). Table 3 shows the heat balance for this reactor and shows that the cooling gas stream,  8  should be at 100 C. for adiabatic heat balance. Again variations on this approach are feasible, the effluent gas could be allowed to cool to 1050 C. and the cooling gas would then have to be heated to a higher temperature. The effluent from the recovery reactor is stream  18  and it enters the quench column where it is rapidly cooled to prevent further reaction. This column is shown with a pumparound cooler in the center which provides the rapid quenching, a reboiler at the bottom which serves to provide some gas stripping for hydrogen and hydrogen bromide removal and a quench condenser at the top to recover as much silicon containing feedstock as possible. Packing or trays are provided in the column to improve the heat and mass transfer. The recovered and degassed feedstock,  7 , is then fed to the vaporizer column, where it is separated into a primarily silicon tetrachloride stream,  8 , a blowdown stream,  10 , which removes impurities and an overhead stream consisting of primarily hydrogenated silicon containing feedstock. Stream  8  is removed as vapor and is heated in STC heater  11  to the desired temperature (100 C. in this example). Additional liquid feedstock makeup is fed to the column near the top via stream  15  from the purification facility; this cold stream provides reflux for the column to aid in the separation. A reflux or knock back partial condenser provides additional reflux. The gas leaving this condenser is superheated to 350 C. in the TCS heater then fed to the deposition reactor. 
     FIG. 6 shows the feedstock recovery vs. temperature for the conditions used in Table 1 for the recovery reactor. It can be seen that as the temperature drops from the deposition temperature of 1100 C. then the SiCl 4  and SiHCl 3  increase but the SiHCL 3  reaches a peak at 1000 C. and starts to decline. The very reactive silicon halides SiCl 2  and SiCl 3  both decline as the temperature drops and by 900 C. the silicon dihalide concentration is very low. These materials can form explosive polymeric solids which are a difficult safety and operational problem thus the optimal recovery temperature of 912 C. and composition used in this example and shown in TABLE 1 is less than the peak trichlorosilane temperature and composition for safety reasons. The silicon dichloride concentration is the most important because it is a polymeric chain former unlike silicon trichloride which is a chain terminator. 
     
       
         xSiCl 2 +2 SiCl 3 =SiCl 3 (SiCl 2 ) x  SiCl 3  Polymerization reaction 
       
     
     Thus as the ratio of SICl 2  to SiCl 3  decreases the chain length decreases and the materials formed are of lower molecular weight, less prone to condense out (Si 2 Cl 6  has MP of −33 C.) and safer to handle. Hexachlorodisilane, Si 2 Cl 6 , is also a valuable product in its own right as a precursor to substituted disilanes. 
     FIGS. 4,  5  and  6  and associated tables are developed to illustrate the use of this design for a fluid bed reactor similar to that used by Padovani. Such reactors are not yet in widespread use and most silicon is currently produced by rod reactors, which maintain a large temperature difference inside the reactor to ensure most of the silicon is deposited on the hot rod. Such reactors can also be used but the hydrogen and TCS would be heated to much lower temperatures prior to the inlet and the effluent gas would be at a lower temperature. The same approach may still be followed but stream  8  would be heated to a much higher temperature and the effluent from the reactor would also be heated in order to obtain the same temperature of about 900 C. in the recovery reactor. 
     Table 1 shows a comparison of the mass balances for FIG.  4  and FIG.  5 . As much as possible the streams have been kept close to the original in composition and flow except where the improvements of the present system require a change. 
     To ease comparison the original molar flows have been divided by the molar flows in the new mass balance. Molar flows are used instead of mass flows because the molar flow more accurately represents the volumetric flow and energy requirements which determines the sizing of the equipment and the required energy. The scaled cost of the equipment depends on the ratio of the size of the equipment to the power of 0.65. Thus the scaled cost ratio shown in the table reflects the effect on the cost of changing the size. 
     The first six streams,  1 ,  2 ,  3 ,  4 ,  5  and  6  which relate to the TCS production reactor all have a molar flow ratio close to one thus there is little impact on this unit. Stream  7  is 20% greater in the improved version but this stream is redirected to the vaporizer. The key improvement is Stream  11 , the feed to the fractionation, which is reduced from 3070 lb./hr to 614 lb./hr. This is reflected in a 20.6% molar flow ratio and a 36% scaled cost. This is a major system which consists of a silicon tetrachloride splitter column, a trichlorosilane column, a silicon tetrachloride adsorber, two silicon tetrachloride columns and associated feed and product tanks, pumps, reboilers condensers etc. Thus five major pieces of equipment are reduced in size by a factor of five which translates to a scaled cost which is only 36% of the original. An additional recovery reactor is provided and the quench unit and distillation column replace the recycle unit and vaporizer. The feed stream to the deposition reactor is 70% of the original flow which results in a 30% energy saving and a scaled cost of 80% for this critical equipment. Coincident with the reduction in cost is a 9% increase in production as shown in stream  16 . The feed stream,  18 , to the recycle equipment/quench is 78% of the original stream thus a reduction in size compensates for an increase in complexity. The feed to the Vaporizer/distillation equipment is the sum of two streams  7  and  15  in FIG. 4 compared to only  15  in FIG.  5 . Thus the feed is 23.37 lbmol/hr compared to 16.74 lbmol/hr for an increase of 40% and a scaled cost factor of 1.24. The equipment is thus larger and more complex since it is a distillation column but only one column is required compared to two vaporizers. Energy requirements are even higher because the requirement for reflux means there is additional heat provided to the reboiler but the temperature is low so low cost energy such as waste heat can be used and the energy can be used efficiently. In contrast the reduction in energy for the reactors is a reduction in high temperature energy which is more difficult to provide, more expensive and less efficient. In U.S. Pat. No. 5,374,413 the silicon deposition reactor is heated by microwaves which is an expensive heating mechanism and difficult to implement because wall deposits block the microwaves. In U.S. Pat. No. 5,798,137 lasers are used for the critical heating in the initial entry or jet region and this is an even more expensive mechanism and much less efficient. Therefore substitution of low-grade heat for expensive reactor heat is a beneficial advantage of this method. 
     In summary the invention provides overall system improvements comprising a fivefold reduction in throughput of the major fractionation train, a 30% reduction in throughput of the deposition reactors and a 9% improvement in silicon production for the cost of a recovery reactor and some increase in cost of the recycle unit and vaporizer. It also provides a method to supplement or replace the reactor heat needed for the decomposition reactor which heat is known to be difficult and expensive to provide for fluid bed decomposition reactors which are established as the desired low cost alternative to rod reactors but which have proved very difficult to implement. 
     This invention is particularly beneficial for increasing the throughput of an existing facility as the same distillation train can process the output of five reactors. Additional equipment is required for deposition and recycle but the production can be increased to 5.5 times the original output. The required throughput to the deposition reactors is only 70% of the original thus the reactor is capable of 40% more throughput hence only three more reactors of the same size are required to increase the throughput to 5.5 times the original. 
     In the present form of the invention three separate innovations; recovering silicon feedstock by control of recovery temperature and composition then quenching; feeding separate streams to a decomposition reactor and bypassing the reactor with some or all of the silicon tetrahalide stream directly to feedstock recovery to control the temperature and composition are connected to standard steps in such a manner that the combination provides an overall optimization of silicon deposition, energy efficiency, product quality and ease of operation. 
     In the best embodiment of this system, the deposition reactor is an energy efficient fluidized bed and the effluent handling and separation system is composed of high purity materials such that no additional purification is needed of the silicon containing materials or hydrogen. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1a 
               
               
                   
               
             
             
               
                 Copy of Table 1 from US Pat. No. 4,092,446 modified to add molar flows 
               
             
          
           
               
                   
                 Stream number 
               
             
          
           
               
                   
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                   
               
               
                 Stream 
                   
                   
                 Makeup 
                 HCl 
                 Crude TC 
                 TCS Unit 
                 TCS Unit 
                 Recycle 
                 TET Botto 
                 TET 
                 Vap 
                 Feed to 
                 Column 
                 TCS 
               
               
                 Identification 
                   
                 MGS 
                 HCl 
                 Feed 
                 Product 
                 Losses 
                 Off gas 
                 Halides 
                 Recycle 
                 OH 
                 BD 
                 Fract 
                 Vents 
                 OH 
               
               
                 Components 
                 MW 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                   
                   
                   
                   
                   
                 6.47 
                 0.16 
                   
                   
                   
                 0.16 
                 0.16 
               
               
                 Silicon 
                 28.06 
                 86.05 
                   
                   
                   
                 8.61 
                   
                   
                   
                   
                   
                   
               
               
                 Hydrogen Chloride 
                 36.461 
                   
                 50.03 
                 338.96 
                   
                   
                 20.34 
                 46 
                   
                   
                   
                 46.18 
                 46 
                 0.18 
               
               
                 Dichlorosilane 
                 100.982 
                   
                   
                   
                   
                   
                   
                 31.58 
                   
                   
                   
                 39.47 
                 31.58 
                 7.89 
               
               
                 Trichlorosilane 
                 135.4 
                   
                   
                   
                 480.78 
                   
                 12.15 
                 795.52 
                   
                 10.36 
                 62.24 
                 1374.17 
                 93.68 
                 25.27 
               
               
                 Silicon Tetrachloride 
                 169.87 
                   
                   
                   
                 28.88 
                   
                 1.7 
                 1217.89 
                 135.4 
                 163.87 
                 64.12 
                 1610.16 
               
               
                 Total 
                   
                 86.05 
                 50.03 
                 338.96 
                 509.66 
                 8.61 
                 40.66 
                 2091.15 
                 135.4 
                 174.23 
                 126.36 
                 3070.14 
                 171.42 
                 33.34 
               
               
                   
               
               
                 Components 
                 MW 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                 0 
                 0 
                 0 
                 0 
                 0 
                 3.209325 
                 0.079365 
                 0 
                 0 
                 0 
                 0.079365 
                 0.079365 
                 0 
               
               
                 Silicon 
                 28.06 
                 3.066643 
                 0 
                 0 
                 0 
                 0.306842 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                 0 
                 1.372151 
                 9.296509 
                 0 
                 0 
                 0.557856 
                 1.261622 
                 0 
                 0 
                 0 
                 1.266559 
                 1.261622 
                 0.004937 
               
               
                 Dichlorosilane 
                 100.982 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0.120318 
                 0.312729 
                 0 
                 0 
                 0 
                 0.390862 
                 0.312729 
                 0.078133 
               
               
                 Trichlorosilane 
                 135.4 
                 0 
                 0 
                 0 
                 3.550812 
                 0 
                 0.089734 
                 5.875332 
                 0 
                 0.076514 
                 0.459675 
                 10.14897 
                 0.691876 
                 0.186632 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 0 
                 0 
                 0 
                 0.170012 
                 0 
                 0.010008 
                 7.169541 
                 0.79708 
                 0.964679 
                 0.377465 
                 9.478778 
                 0 
                 0 
               
               
                 Total 
                   
                 3.066643 
                 1.372151 
                 9.296509 
                 3.720825 
                 0.306842 
                 3.987242 
                 14.69859 
                 0.79708 
                 1.041193 
                 0.83714 
                 21.36453 
                 2.345592 
                 0.269702 
               
               
                   
               
             
          
           
               
                   
                 Stream number 
               
             
          
           
               
                   
                   
                 14 
                 15 
                 16 
                 17 
                 18 
                 19 
                 20 
                 21 
                 22 
                 23 
                 24 
                 25 
                 26 
                 27 
               
               
                   
               
               
                 Stream 
                   
                 Surplus 
                 Vap 
                 Feed to 
                 Silicon 
                 Reactor 
                 Recycle 
                 H2 
                 Losses 
                 Make-up 
                 Vent gase 
                 Vent Reco 
                 H2 Dryer 
                   
                 Recycle 
               
               
                 Identification 
                   
                 TET 
                 Feed 
                 Reactors 
                 Product 
                 Effluent 
                 Gas 
                 Recycle 
                   
                 Hydrogen 
                 to HCl sys 
                 Liquid 
                 Losses 
                 Losses 
                 HCl 
               
               
                 Components 
                   
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                   
                   
                 291.7 
                   
                 286.7 
                 286.54 
                 281.48 
                 6.63 
                 10.22 
                 6.63 
                   
                 3.63 
                 1.43 
               
               
                 Silicon 
                 28.06 
                   
                   
                   
                 69.6 
               
               
                 Hydrogen Chloride 
                 36.461 
                   
                   
                   
                   
                 283.8 
                 237.8 
                   
                 3.31 
                   
                 66.34 
                   
                   
                 11.9 
                 288.93 
               
               
                 Dichlorosilane 
                 100.982 
                   
                   
                   
                   
                 32.9 
                 1.32 
                   
                 3.02 
                   
                 3.02 
                 28.56 
                   
                 1.32 
               
               
                 Trichlorosilane 
                 135.4 
                   
                 1244.74 
                 1182.5 
                   
                 801.2 
                 5.68 
                   
                 1.59 
                   
                 1.59 
                 104.24 
                   
                 5.68 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 28.47 
                 1282.4 
                 1218.3 
                   
                 1218.3 
                 0.41 
                   
                 0.01 
                   
                 0.01 
                 1.69 
                   
                 0.41 
               
               
                 Total 
                   
                 28.47 
                 2527.14 
                 2692.5 
                 69.6 
                 2622.9 
                 531.75 
                 281.48 
                 14.56 
                 10.22 
                 77.59 
                 134.49 
                 3.63 
                 20.74 
                 288.93 
               
               
                   
               
               
                 Components 
                 MW 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                 0 
                 0 
                 144.6925 
                 0 
                 142.2123 
                 142.1329 
                 139.623 
                 3.28869 
                 5.069444 
                 3.28869 
                 0 
                 1.800595 
                 0.709325 
                 0 
               
               
                 Silicon 
                 28.06 
                 0 
                 0 
                 0 
                 2.480399 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                 0 
                 0 
                 0 
                 0 
                 7.783659 
                 6.522037 
                 0 
                 0.090782 
                 0 
                 1.819478 
                 0 
                 0 
                 0.326376 
                 7.924358 
               
               
                 Dichlorosilane 
                 100.982 
                 0 
                 0 
                 0 
                 0 
                 0.325801 
                 0.013072 
                 0 
                 0.029906 
                 0 
                 0.029906 
                 0.282823 
                 0 
                 0.013072 
                 0 
               
               
                 Trichlorosilane 
                 135.4 
                 0 
                 9.193058 
                 8.733383 
                 0 
                 5.917282 
                 0.04195 
                 0 
                 0.011743 
                 0 
                 0.011743 
                 0.769867 
                 0 
                 0.04195 
                 0 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 0.167599 
                 7.549302 
                 7.171955 
                 0 
                 7.171955 
                 0.002414 
                 0 
                 5.89E−05 
                 0 
                 5.89E−05 
                 0.009949 
                 0 
                 0.002414 
                 0 
               
               
                 Total 
                   
                 0.167599 
                 16.74236 
                 160.5978 
                 2.480399 
                 163.411 
                 148.7124 
                 139.623 
                 3.421181 
                 5.069444 
                 5.149877 
                 1.062639 
                 1.800595 
                 1.093137 
                 7.924358 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1b 
               
               
                   
               
               
                 Improved Mass Balance based on FIG 4b 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Stream number 
               
             
          
           
               
                   
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                   
               
               
                 Stream 
                   
                   
                 Makeup 
                 HCl 
                 Crude TC 
                 TCS Unit 
                 TCS Unit 
                 Recycle 
                 TET To 
                 TET 
                 Vap 
                 Feed to 
                 Column 
                 TCS 
               
               
                 Identification 
                   
                 MGS 
                 HCl 
                 Feed 
                 Product 
                 Losses 
                 Off gas 
                 Halides 
                 Quench 
                 OH 
                 BD 
                 Fract 
                 Vents 
                 OH 
               
               
                 Components 
                 MW 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                   
                   
                   
                   
                   
                 6.571664 
                 0.112508 
                   
                   
                   
                   
                 0 
                 0 
               
               
                 Silicon 
                 28.06 
                 8.26E+01 
                   
                   
                   
                 8.2565 
                   
                 0 
                   
                   
                   
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                   
                 46.40906 
                 406.6335 
                   
                   
                 20.34 
                 1.553239 
                   
                   
                   
                 0 
                 0 
                 0 
               
               
                 Dichlorosilane 
                 100.982 
                   
                   
                   
                   
                   
                   
                 16.4696 
                   
                   
                   
                 0 
                 0 
                 0 
               
               
                 Trichlorosilane 
                 135.4 
                   
                   
                   
                 507.0494 
                   
                 12.15 
                 880.9264 
                 1.71958 
                 3.924622 
                 0.022341 
                 520.5693 
                 35.4882802 
                 9.5728954 
               
               
                 Silicon Tetrachloride 
                 169.87 
                   
                   
                   
                 28.40728 
                   
                 1.7 
                 2173.801 
                 2157.349 
                 9.570127 
                 56.0571 
                 94.03451 
               
               
                 Total 
                   
                 82.565 
                 46.40906 
                 406.6335 
                 535.4567 
                 8.2565 
                 40.76166 
                 3072.863 
                 2159.069 
                 13.49475 
                 56.07944 
                 614.6038 
                 35.4882802 
                 9.5728954 
               
               
                   
               
               
                 Components 
                 MW 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                 0 
                 0 
                 0 
                 0 
                 0 
                 3.259754 
                 0.055807 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Silicon 
                 28.06 
                 2.94E+00 
                 0 
                 0 
                 2.94E−01 
                 2.94E−01 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                 0 
                 1.272841 
                 11.15256 
                 0 
                 0 
                 0.557856 
                 0.0426 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Dichlorosilane 
                 100.982 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0.120318 
                 0.163094 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Trichlorosilane 
                 135.4 
                 0 
                 0 
                 0 
                 3.744826 
                 0 
                 0.089734 
                 6.506103 
                 0.0127 
                 0.028985 
                 0.000165 
                 3.844677 
                 0.26209956 
                 0.07070085 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 0 
                 0 
                 0 
                 0.16723 
                 0 
                 0.010008 
                 12.79685 
                 12.7 
                 0.056338 
                 0.33 
                 0.553567 
                 0 
                 0 
               
               
                 Total 
                   
                 2.942445 
                 1.272841 
                 11.15256 
                 4.2063 
                 0.294244 
                 4.037671 
                 19.56446 
                 12.7127 
                 0.085323 
                 0.330165 
                 4.398245 
                 0.26209956 
                 0.07070085 
               
               
                 Molal Flow Ratio 
                   
                 0.9595 
                 0.927625 
                 1.199651 
                 1.130475 
                 0.958943 
                 1.012648 
                 1.331043 
                 15.94909 
                 0.081948 
                 0.394396 
                 0.205867 
                 0.11174132 
                 0.26214461 
               
               
                 Scaled Cost Ratio 
                   
                 0.973485 
                 0.95234 
                 1.125604 
                 1.082978 
                 0.973118 
                 1.008203 
                 1.204273 
                 6.050319 
                 0.196697 
                 0.546206 
                 0.357957 
                 0.24062402 
                 0.41884333 
               
               
                   
               
             
          
           
               
                   
                 Stream number 
               
             
          
           
               
                 Stream number 
                   
                 14 
                 15 
                 16 
                 17 
                 18 
                 19 
                 20 
                 21 
                 22 
                 23 
                 24 
                 25 
                 26 
                 27 
               
               
                   
               
               
                 Stream 
                   
                 Surplus 
                 Vap 
                 Feed to 
                 Silicon 
                 Reactor 
                 Recycle 
                 H2 
                 Losses 
                 Make-up 
                 Vent gase 
                 Vent Reco 
                 H2 Dryer 
                   
                 Recycle 
               
               
                 Identification 
                   
                 TET 
                 Feed 
                 Reactors 
                 Product 
                 Effluent 
                 Gas 
                 Recycle 
                   
                 Hydrogen 
                 to HCl sys 
                 Liquid 
                 Losses 
                 Losses 
                 HCl 
               
               
                 Components 
                 MW 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
                 lbs/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                   
                   
                 207.365 
                   
                 201.6 
                 201.4875 
                 196.3692 
                 6.63 
                 10.88337 
                 6.571664 
                   
                 3.63 
                 1.43 
               
               
                 Silicon 
                 28.06 
                   
                   
                 0 
                 76.0426 
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                   
                   
                 1.553239 
                   
                 310.6477 
                 309.0945 
                   
                 3.31 
                   
                 66.34 
                   
                   
                 11.9 
                 360.224481 
               
               
                 Dichlorosilane 
                 100.982 
                   
                   
                 16.4696 
                   
                 16.96498 
                 0.495377 
                   
                 0 
                   
                 0 
                 0 
                   
                 0.4953773 
               
               
                 Trichlorosilane 
                 135.4 
                   
                 471.538 
                 1350.722 
                   
                 885.516 
                 4.589629 
                   
                 1.59 
                   
                 1.59 
                 46.04828 
                   
                 4.58962943 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 29.56253 
                 54.90185 
                 15.29684 
                   
                 2174.336 
                 0.534908 
                   
                 0.01 
                   
                 0.01 
                 1.69 
                   
                 0.5349084 
               
               
                 Total 
                   
                 29.56253 
                 526.4399 
                 1591.407 
                 76.0426 
                 3589.065 
                 516.2019 
                 196.3692 
                 11.54 
                 10.88337 
                 74.51166 
                 47.73828 
                 3.63 
                 18.9499151 
                 360.224481 
               
               
                   
               
               
                 Components 
                 MW 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
                 lbmol/hr 
               
               
                   
               
               
                 Hydrogen 
                 2.016 
                 0 
                 0 
                 102.8596 
                 0 
                 100 
                 99.94419 
                 97.40534 
                 3.28869 
                 5.398495 
                 3.259754 
                 0 
                 1.80059524 
                 0.7093254 
                 0 
               
               
                 Silicon 
                 28.06 
                 0 
                 0 
                 0 
                 2.71 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 Hydrogen Chloride 
                 36.461 
                 0 
                 0 
                 0.0426 
                 0 
                 8.52 
                 8.4774 
                 0 
                 0.090782 
                 0 
                 1.819478 
                 0 
                 0 
                 0.32637613 
                 9.87972029 
               
               
                 Dichlorosilane 
                 100.982 
                 0 
                 0 
                 0.163094 
                 0 
                 0.168 
                 0.004906 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0.0049056 
                 0 
               
               
                 Trichlorosilane 
                 135.4 
                 0 
                 3.482556 
                 9.975794 
                 0 
                 6.54 
                 0.033897 
                 0 
                 0.011743 
                 0 
                 0.011743 
                 0.340091 
                 0 
                 0.03389682 
                 0 
               
               
                 Silicon Tetrachloride 
                 169.87 
                 0.17403 
                 0.323199 
                 0.09005 
                 0 
                 12.8 
                 0.003149 
                 0 
                 5.89E−05 
                 0 
                 5.89E−05 
                 0.009949 
                 0 
                 0.00314893 
                 0 
               
               
                 Total 
                   
                 0.17403 
                 3.805755 
                 113.1312 
                 2.71 
                 128.028 
                 108.4635 
                 97.40534 
                 3.391274 
                 5.398495 
                 5.091034 
                 0.350039 
                 1.80059524 
                 1.07765287 
                 9.87972029 
               
               
                 Molal Flow Ratio 
                   
                 1.038375 
                 0.227313 
                 0.704438 
                 1.092566 
                 0.783472 
                 0.729351 
                 0.697631 
                 0.991258 
                 1.064909 
                 0.988574 
                 0.329406 
                 1 
                 0.98583555 
                 1.24675347 
               
               
                 Scaled Cost Ratio 
                   
                 1.024779 
                 0.381773 
                 0.796339 
                 1.059232 
                 0.853327 
                 0.814533 
                 0.791328 
                 0.994309 
                 1.041725 
                 0.992558 
                 0.485876 
                 1 
                 0.99077014 
                 1.15413705 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Heat Balance   Feed to Deposition Reactor 
               
             
          
           
               
                   
                 Temper. 
                 Amount 
                 Amount 
                 Amount 
                 Latent H 
                 Total H 
               
               
                   
                 C. 
                 kmol 
                 kg 
                 Nm3 
                 Mcal 
                 Mcal 
               
               
                   
                   
               
             
          
           
               
                 A: Hydrogen Provides All the Heat up to the 1100 C. peak Temperature 
               
             
          
           
               
                 INPUT SPECIES Formula 
                   
                   
                   
                   
                   
                   
               
               
                 PHASE 1: 
                  350.000 
               
               
                 H2(g) * Heating Gas 
                 1620.000 
                 102.779  
                 207.182 
                 2354.344   
                 1211.09  
                 1211.09 
               
               
                 HCl(g) 
                  350.000 
                 0.043 
                  1.564 
                 0.978  
                  0.10 
                 −0.85 
               
               
                 SiCl4(g) 
                  350.000 
                 0.191 
                  32.450 
                 4.281 
                  1.46 
                 −28.79 
               
               
                 SiHCl3(g) 
                  350.000 
                 10.000  
                 1354.524  
                 224.136  
                 72.63 
                 −1113.37 
               
               
                 SiH2Cl2(g) 
                  350.000 
                 0.162 
                  16.363 
                 3.692 
                  0.96 
                 −11.45 
               
               
                 OUTPUT SPECIES Formula 
               
               
                 PHASE 1: 
                 1100.000 
                 120.740  
                 1612.155  
                 2699.030   
                 1040.598  
                 53.802 
               
               
                 H2(g) 
                 1100.000 
                 102.000  
                 205.612 
                 2336.495   
                 785.91  
                 785.91 
               
               
                 HCl(g) 
                 1100.000 
                 8.380 
                 305.542 
                 190.964  
                 66.69 
                 −118.20 
               
               
                 SiCl2(g) 
                 1100.000 
                 1.930 
                 191.054 
                 43.258  
                 28.00 
                 −49.78 
               
               
                 SiCl3(g) 
                 1100.000 
                 0.896 
                 120.462 
                 20.083  
                 18.41 
                 −65.18 
               
               
                 SiCl4(g) 
                 1100.000 
                 1.960 
                 332.999 
                 43.931  
                 52.10 
                 −258.37 
               
               
                 SiHCl(g) 
                 1100.000 
                 0.009 
                  0.581 
                 0.202 
                  0.12 
                 0.20 
               
               
                 SiHCl3(g) 
                 1100.000 
                 2.660 
                 360.303 
                 59.620  
                 67.44 
                 −248.03 
               
               
                 SiH2Cl2(g) 
                 1100.000 
                 0.189 
                  19.090 
                 4.307 
                  4.27 
                 −10.21 
               
               
                 SiH3Cl(g) 
                 1100.000 
                 0.006 
                  0.399 
                 0.137 
                  0.12 
                 −0.08 
               
               
                 Si(Solid Deposited) 
                 1100.000 
                 2.710 
                  76.112 
                 0.033 
                 17.53 
                 17.53 
               
               
                   
                   
                 kmol 
                 kg 
                 Nm3 
                 Mcal 
                 Mcal 
               
               
                 BALANCE: 
                   
                 7.565 
                  0.071 
                 111.598  
                 −245.64  
                 −2.83 
               
             
          
           
               
                 Temperature of Products = 
                 1102.734° C. 
                 When Heat Balance = 0 
               
             
          
           
               
                 B: Hydrogen Provides All the Heat up to the 845 C. Initial Temperature, remaining heat by Rx Heaters 
               
             
          
           
               
                 INPUT SPECIES Formula 
                   
                   
                   
                   
                   
                   
               
               
                 PHASE 1: 
                  350.000 
               
               
                 H2(g) *Heating gas 
                 1300.000 
                 102.779  
                 207.182 
                 2354.344   
                 950.34 
                 950.34 
               
               
                 HCl(g) 
                  350.000 
                 0.043 
                 1.564 
                 0.978 
                 0.10 
                 −0.85 
               
               
                 SiCl4(g) 
                  350.000 
                 0.191 
                 32.450 
                 4.281 
                 1.46 
                 −28.79 
               
               
                 SiHCl3(g) 
                  350.000 
                 10.000  
                 1354.524 
                 224.136  
                 72.63 
                 −1113.37 
               
               
                 SiH2Cl2(g) 
                  350.000 
                 0.162 
                 16.363 
                 3.692 
                 0.96 
                 −11.45 
               
               
                 OUTPUT SPECIES Formula 
               
               
                 PHASE 1: 
                 1100.000 
                 120.740  
                 1612.155  
                 2699.030   
                 1040.598  
                 53.802 
               
               
                 H2(g) 
                 1100.000 
                 102.000  
                 205.612 
                 2336.495   
                 785.91  
                 785.91 
               
               
                 HCl(g) 
                 1100.000 
                 8.380 
                 305.542 
                 190.964  
                 66.69 
                 −118.20 
               
               
                 SiCl2(g) 
                 1100.000 
                 1.930 
                 191.054 
                 43.258  
                 28.00 
                 −49.78 
               
               
                 SiCl3(g) 
                 1100.000 
                 0.896 
                 120.462 
                 20.083  
                 18.41 
                 −65.18 
               
               
                 SiCl4(g) 
                 1100.000 
                 1.960 
                 332.999 
                 43.931  
                 52.10 
                 −258.37 
               
               
                 SiHCl(g) 
                 1100.000 
                 0.009 
                  0.581 
                 0.202 
                  0.12 
                 0.20 
               
               
                 SiHCl3(g) 
                 1100.000 
                 2.660 
                 360.303 
                 59.620  
                 67.44 
                 −248.03 
               
               
                 SiH2Cl2(g) 
                 1100.000 
                 0.189 
                  19.090 
                 4.307 
                  4.27 
                 −10.21 
               
               
                 SiH3Cl(g) 
                 1100.000 
                 0.006 
                  0.399 
                 0.137 
                  0.12 
                 −0.08 
               
               
                 Si(Solid Deposited) 
                 1100.000 
                 2.710 
                  76.112 
                 0.033 
                 17.53 
                 17.53 
               
               
                   
                   
                 kmol 
                 kg 
                 Nm3 
                 Mcal 
                 Mcal 
               
               
                 BALANCE: 
                   
                 7.565 
                  0.071 
                 11.598  
                 15.11 
                 257.93 
               
             
          
           
               
                 Temperature of Products = 
                 845.490° C. 
                 When Heat Balance = 0 
               
               
                   
               
               
                 Reactor heaters @ 50% efficient= 272.0 Kilowatts  
               
               
                 For Flows In Table 1 Improved Mass Balance  
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Heat Balance    Feedstock recovery   SiCl4 Cooling gas 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Temper. 
                 Amount 
                 Amount 
                 Amount 
                 Latent H 
                 Total H 
               
               
                   
                 C. 
                 kmol 
                 kg 
                 Nm3 
                 Mcal 
                 Mcal 
               
               
                   
               
               
                 INPUT SPECIES Formula 
               
               
                 PHASE 1: 
                 1100.000 
                 130.734  
                 3694.185  
                 2983.739   
                 1044.093  
                 −1954.703 
               
               
                 H2(g) 
                 1100.000 
                 102.000  
                 205.612 
                 2336.495   
                 785.91  
                 785.91 
               
               
                 HCl(g) 
                 1100.000 
                 8.380 
                 305.542 
                 190.964  
                 66.69 
                 −118.20 
               
               
                 SiCl2(g) 
                 1100.000 
                 1.930 
                 191.054 
                 43.258  
                 28.00 
                 −49.78 
               
               
                 SiCl3(g) 
                 1100.000 
                 0.896 
                 120.462 
                 20.083  
                 18.41 
                 −65.18 
               
               
                 SiCl4(g) 
                 1100.000 
                 1.960 
                 332.999 
                 43.931  
                 52.10 
                 −258.37 
               
               
                 SiCl4(g) * Cooling gas 
                  100.000 
                 12.700  
                 2157.698  
                 284.653  
                 21.24 
                 −1990.44 
               
               
                 SiHCl(g) 
                 1100.000 
                 0.009 
                  0.604 
                 0.210 
                  0.12 
                 0.21 
               
               
                 SiHCl3(g) * Cooling gas 
                  100.000 
                 0.013 
                  1.720 
                 0.285 
                  0.02 
                 −1.49 
               
               
                 SiH2Cl2(g) 
                 1100.000 
                 0.189 
                  19.090 
                 4.307 
                  4.27 
                 −10.21 
               
               
                 SiH3Cl(g) 
                 1100.000 
                 0.006 
                  0.426 
                 0.146 
                  0.13 
                 −0.08 
               
               
                 OUTPUT SPECIES Formula 
               
               
                 PHASE 1: 
                  912.500 
                 128.878  
                 3694.890  
                 2941.200   
                 1115.013  
                 −1954.713 
               
               
                 H2(g) 
                  912.500 
                 100.000  
                 201.580 
                 2290.682   
                 629.20  
                 629.20 
               
               
                 HCl(g) 
                  912.500 
                 8.520 
                 310.647 
                 194.154  
                 55.28 
                 −132.70 
               
               
                 SiCl2(g) 
                  912.500 
                 0.254 
                  25.144 
                 5.693 
                  3.03 
                 −7.21 
               
               
                 SiCl3(g) 
                  912.500 
                 0.594 
                  79.860 
                 13.314  
                 10.02 
                 −45.40 
               
               
                 SiCl4(g) 
                  912.500 
                 12.800  
                 2174.688  
                 286.894  
                 278.94  
                 −1748.58 
               
               
                 SiHCl3(g) 
                  912.500 
                 6.540 
                 885.859 
                 146.585  
                 135.45  
                 −640.19 
               
               
                 SiH2Cl2(g) 
                  912.500 
                 0.168 
                  16.969 
                 3.829 
                  3.06 
                 −9.81 
               
               
                 SiH3Cl(g) 
                  912.500 
                 0.002 
                  0.125 
                 0.043 
                  0.03 
                 −0.03 
               
               
                   
                   
                 kmol 
                 kg 
                 Nm3 
                 Mcal 
                 Mcal 
               
               
                 BALANCE: 
                   
                 −1.856  
                  0.705 
                 −42.539  
                  70.920 
                 −0.010 
               
               
                   
               
             
          
           
               
                 MATERIAL BALANCE 
                 Input 
                 Output 
                 Balance 
                 Input 
                 Output 
                 Balance 
               
               
                 ELEMENT 
                 kmol 
                 kmol 
                 kmol 
                 kg 
                 kg 
                 kg 
               
               
                   
               
               
                 Cl 
                 81.950 
                 81.968 
                 0.018 
                 2905.368  
                 2906.017  
                 0.648 
               
               
                 H 
                 215.451  
                 215.402  
                 −0.049  
                 217.53 
                 217.104 
                 −0.050  
               
               
                 Si 
                 20.354 
                 20.358 
                 0.004 
                 571.663 
                 571.769 
                 0.106