TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Conditions: Hydrogen is separated from a byproduct mixture of the CVD comprising hydrogen and silicon tetrachloride to yield a composition comprising silicon tetrachloride. A composition comprising silicon tetrachloride or hydrogen chloride, and a composition comprising silane, dichlorosilane or trichlorosilane are mixed by a pre-disproportionation reactor silane/chlorosilane mixer (106) to yield the disproportionation reactor feed. The temperature of feed is controlled by a pre-disproportionation reactor temperature controller (110). The feed is reacted to form a disproportionation reaction product comprising dichlorosilane, trichlorosilane, and silicon tetrachloride. The mixing of composition comprising silicon tetrachloride and composition comprising silane includes mixing composition comprising liquid or vapor silane and composition comprising liquid or vapor silicon tetrachloride. The mixing process involves providing composition comprising silane and composition comprising silicon tetrachloride to pre-disproportionation reactor silane/chlorosilane mixer and/or disproportionation reactor at 10-500 psig, preferably 180 psig, or 500-2500 psig, preferably 2000 psig. The disproportionation reactor comprises a catalyst. The catalyst comprises a polymeric ion-exchange resin, or a metal, preferably copper-infused essentially pure silicon. The temperature of feed is controlled to 30-500 degrees C, preferably 60 degrees C. The composition of composition comprising silicon tetrachloride or rate at which composition comprising silicon tetrachloride is supplied to the pre-disproportionation reactor silane/chlorosilane mixer is controlled such that the ratio of chlorine and silicon in the feed comprising the mixture of silane and silicon tetrachloride is 2:1-3.9:1, preferably 3.3:1. Silicon tetrachloride is separated from a product of the disproportionation reaction in a post-disproportionation reactor silicon tetrachloride separator (118), to yield a post-disproportionation reactor silicon tetrachloride-rich stream and a post-disproportionation reactor trichlorosilane-rich stream. The silicon tetrachloride content of disproportionation reactor feed is adjusted using silicon tetrachloride separated from the product of disproportionation reactor in the post-disproportionation reactor silicon tetrachloride separator. A mixture comprising the disproportionation reaction product is vaporized in a pre-CVD reactor vaporizer (128) to yield a vaporized disproportionation reaction product. Hydrogen is mixed with the vaporized disproportionation reaction product by a pre-CVD reactor mixer (132) or CVD reactor to yield a mixture of hydrogen and disproportionation reaction product. CVD of the mixture of hydrogen and disproportionation reaction product is carried out to deposit silicon on the substrate. An effluent mixture comprising hydrogen, silicon tetrachloride, and one or more of hydrogen chloride, dichlorosilane, and trichlorosilane is released from the CVD reactor. The effluent mixture is cooled by a post-CVD reactor cooler (I) (142) to yield a vapor-liquid two-phase mixture. Oily contaminants, including polysilyl materials, are removed from the effluent mixture cooled by cooler (I). The vapor-liquid two-phase mixture is separated by a post-CVD reactor decanter (169) from cooler (I) to yield a vapor phase and a liquid phase. The vapor phase from the decanter is converted to a vapor-liquid two-phase mixture or a vapor-phase by a post-CVD reactor compressor (144). The vapor-liquid two-phase mixture or the vapor phase from the compressor is cooled by a post-CVD reactor cooler (II) (146). The effluent mixture from the CVD reactor is supplied to a post-CVD reactor in-situ hydrogen chloride reactor, and hydrogen chloride in the effluent mixture from the CVD reactor is converted into chlorosilane by the post-CVD reactor in situ hydrogen chloride reactor. The effluent mixture from the CVD reactor is heated by an in situ hydrogen chloride reactor heat exchanger before being supplied to the post-CVD reactor in situ hydrogen chloride reactor. The effluent mixture from the CVD reactor is heated to 200-700 degrees C, preferably 500 degrees C. The in situ hydrogen chloride reactor heat exchanger exchanges heat from an effluent from the post-CVD reactor in situ hydrogen chloride reactor to the effluent mixture from the CVD reactor before supplying the effluent mixture from the CVD reactor to the post-CVD reactor in situ hydrogen chloride reactor. The effluent mixture from the CVD reactor is heated by a post-CVD reactor startup heater before being supplied from the CVD reactor to the post-CVD reactor in situ hydrogen chloride reactor via the in situ hydrogen chloride reactor heat exchanger. The residence time of effluent mixture from the CVD reactor within the post-CVD reactor in situ hydrogen chloride reactor is less than about 10 minutes, preferably less than 0.1 minute. An effluent mixture from the post-CVD reactor in situ hydrogen chloride reactor is cooled by a post-CVD reactor cooler (I) to yield a vapor-liquid two-phase mixture. The vapor-liquid two-phase mixture is separated by a post-CVD reactor decanter from cooler (I) to yield a vapor phase and a liquid phase. The vapor phase from the decanter is converted into a vapor-liquid two-phase mixture or a vapor phase by a post-CVD reactor compressor. The vapor-liquid two-phase mixture or the vapor phase from the compressor is cooled by a post-CVD reactor cooler (II). Hydrogen is separated from the CVD reactor effluent mixture by a post-CVD reactor hydrogen separator (150) to yield a post-CVD reactor hydrogen-rich stream and a post-CVD reactor hydrogen-depleted stream. The concentration of silicon tetrachloride in the post-CVD reactor hydrogen-rich stream is less than 15 wt.%, preferably less than 0.1 wt.%. The post-CVD reactor hydrogen-rich stream is mixed with a post-disproportionation reactor trichlorosilane-rich stream from a post-disproportionation reactor silicon tetrachloride separator by a pre-CVD reactor mixer. The post-CVD reactor hydrogen-depleted stream and post-disproportionation reactor silicon tetrachloride-rich stream from the post-disproportionation reactor silicon tetrachloride separator are mixed by a pre-disproportionation reactor chlorosilane mixer (162). The amounts of elemental silicon and elemental chlorine in the post-CVD reactor hydrogen-depleted stream and in the post-disproportionation reactor silicon tetrachloride-rich stream are determined prior to mixing the post-CVD reactor hydrogen-depleted stream and the post-disproportionation reactor silicon tetrachloride-rich stream. Amounts of post-CVD reactor hydrogen-depleted stream, post-disproportionation reactor silicon tetrachloride-rich stream, and, as required, a feed of purified silicon tetrachloride, trichlorosilane, dichlorosilane, or a mixture of one or more of purified silicon tetrachloride, trichlorosilane, or dichlorosilane are mixed by pre-disproportionation reactor chlorosilane mixer. The amounts of elemental chlorine and elemental silicon supplied from each source are controlled to maintain a selected ratio of chlorine to silicon in the disproportionation reactor feed. Hydrogen chloride is separated from the post-CVD reactor hydrogen-depleted stream by a post-CVD reactor hydrogen chloride separator to yield a post-CVD reactor hydrogen-depleted, hydrogen chloride-rich stream, and a post-CVD reactor hydrogen-depleted, hydrogen chloride-depleted stream. The post-CVD reactor hydrogen-depleted, hydrogen chloride-rich stream is transported from the post-CVD reactor hydrogen chloride separator to a hydrogen chloride storage system. The post-CVD reactor hydrogen-depleted, hydrogen chloride-depleted stream from the post-CVD reactor hydrogen chloride separator is transported to a pre-disproportionation reactor chlorosilane mixer. Silicon tetrachloride is separated from dichlorosilane and trichlorosilane in the hydrogen-depleted, hydrogen chloride-depleted stream by a post-CVD reactor chlorosilane separator to yield a post-CVD reactor silicon tetrachloride-rich stream and a post-CVD reactor dichlorosilane-rich, trichlorosilane-rich stream. Dichlorosilane is separated from the trichlorosilane in the post-CVD reactor dichlorosilane-rich, trichlorosilane-rich stream by a dichlorosilane/trichlorosilane separator to yield a post-CVD reactor dichlorosilane-rich stream and a post-CVD reactor trichlorosilane-rich stream. The post-CVD reactor trichlorosilane-rich stream is mixed with a post-disproportionation reactor trichlorosilane-rich stream. The post-CVD reactor silicon tetrachloride-rich stream and the post-CVD reactor dichlorosilane-rich stream are mixed by a post-CVD reactor chlorosilane mixer. The mixing of silicon tetrachloride-rich stream and dichlorosilane-rich stream includes selecting an amount of dichlorosilane and adding the amount of dichlorosilane to the post-CVD reactor chlorosilane mixer to control the concentration of dichlorosilane in the feed to the disproportionation reactor and CVD reactor. The concentration of dichlorosilane in the feed to the CVD reactor includes controlling the ratio of chlorine to silicon in the feed to the disproportionation reactor, by controlling one or more of make-up silicon tetrachloride, trichlorosilane, and dichlorosilane added to the feed to the disproportionation reactor. Dichlorosilane from the dichlorosilane/trichlorosilane separator is supplied to the CVD reactor. Dichlorosilane from the dichlorosilane/trichlorosilane separator is supplied to the CVD reactor by adjusting the concentration of dichlorosilane in the feed to the CVD reactor. All or a portion of dichlorosilane is stored in a dichlorosilane storage system or disposed off by a dichlorosilane disposal system. Hydrogen and hydrogen chloride from the CVD reactor effluent mixture are separated by a post-CVD reactor hydrogen/hydrogen chloride separator to yield a hydrogen/hydrogen chloride-rich stream and a hydrogen/hydrogen chloride-depleted stream. Hydrogen is separated from hydrogen chloride in the hydrogen/hydrogen chloride-rich stream by a pre-CVD reactor hydrogen/hydrogen chloride separator, and hydrogen chloride is transported from the pre-CVD reactor hydrogen/hydrogen chloride separator to a hydrogen chloride storage system. Hydrogen from the pre-CVD reactor hydrogen/hydrogen chloride separator is mixed by a pre-CVD reactor mixer with a post-disproportionation reactor trichlorosilane-rich stream from the post-disproportionation reactor silicon tetrachloride separator. The hydrogen-depleted, hydrogen chloride-rich stream from the post-CVD reactor hydrogen chloride separator and silane are fed to a pre-disproportionation reactor silane/hydrogen chloride reactor. Silane is reacted with hydrogen chloride by the pre-disproportionation reactor silane/hydrogen chloride reactor to yield chlorosilanes including trichlorosilane and silicon tetrachloride. The temperature within pre-disproportionation reactor silane/hydrogen chloride reactor is 50-700 degrees C, preferably 500 degrees C. The molar ratio of silane and hydrogen chloride in the feed to the pre-disproportionation reactor silane/hydrogen chloride reactor si 0:1-2:1, preferably 0.33:1. Silane is reacted with hydrogen chloride by a pre-disproportionation reactor silane/hydrogen chloride reactor in the presence of a metal-containing catalyst. Amounts of the post-CVD reactor hydrogen-depleted, hydrogen chloride-depleted stream, chlorosilanes from the pre-disproportionation reactor silane/hydrogen chloride reactor, a silicon tetrachloride-rich stream from a post-disproportionation reactor silicon tetrachloride separator, and, as required, a feed of purified silicon tetrachloride, purified trichlorosilane, purified dichlorosilane, or a mixture of one or more of purified silicon tetrachloride, purified trichlorosilane, or purified dichlorosilane are mixed by pre-disproportionation reactor chlorosilane mixer. The amounts of elemental chlorine and elemental silicon supplied from each source are controlled to maintain a selected ratio of chlorine to silicon in the feed to the disproportionation reactor. The hydrogen-depleted, hydrogen chloride-rich stream from the post-CVD reactor hydrogen chloride separator is reacted with silane and CVD reactor effluent mixture by a post-CVD reactor silane/hydrogen chloride reactor. The temperature of CVD reactor effluent mixture in the post-CVD reactor silane/hydrogen chloride reactor is controlled to 200-600 degrees C prior to mixing the hydrogen- depleted, hydrogen chloride-rich stream with the silane and the CVD reactor effluent mixture in the post-CVD reactor silane/hydrogen chloride reactor. The temperature of CVD reactor effluent in the post-CVD reactor silane/hydrogen chloride reactor is controlled by adjusting the temperature by a post-CVD reactor heat exchanger. The temperature of CVD reactor effluent mixture in the post-CVD reactor silane/hydrogen chloride reactor is adjusted prior to mixing of hydrogen chloride with silane and CVD reactor effluent mixture to 400-500 degrees C. The molar ratio of silane and hydrogen chloride in the feed to post-CVD reactor silane/hydrogen chloride reactor is 0:1-2:1, preferably 0.33:1. The flow in post-CVD reactor silane/hydrogen chloride reactor is adjusted such that residence time of hydrogen chloride-silane-CVD effluent mixture within the post-CVD reactor silane/hydrogen chloride reactor is sufficient to allow complete reaction of hydrogen chloride and silane. The post-CVD reactor silane/hydrogen chloride reactor includes reaction chamber(s) of sufficient total volume to provide a residence time appropriate to allow complete reaction of hydrogen chloride and silane. The residence time of effluent mixture within the post-CVD reactor silane/hydrogen chloride reactor is less than 10 minutes, preferably less than 0.1 minute. Dichlorosilane is separated from the post-disproportionation reactor trichlorosilane-rich stream by a post-disproportionation reactor dichlorosilane separator to yield a post-disproportionation reactor dichlorosilane-rich stream. The dichlorosilane concentration in feed to CVD reactor is determined and adjusted by adding post-disproportionation reactor dichlorosilane-rich stream to the feed to CVD reactor. The concentration of dichlorosilane in the CVD reactor is adjusted by adding dichlorosilane separated from CVD reactor effluent mixture from which hydrogen and hydrogen chloride have been removed. The molar ratio of monochlorosilane, dichlorosilane and/or trichlorosilane to silicon tetrachloride is 0-3:1, preferably 0.5:1. Low-boiling phosphorus contaminants are converted to intermediate and high-boiling phosphorus contaminants by disproportionation reactor. The low-boiling phosphorus contaminants include phosphine and chlorophosphane. The intermediate-boiling phosphorus contaminants include dichlorophosphane. The high-boiling phosphorus contaminants include trichlorophosphane. Silicon tetrachloride, and intermediate- and high-boiling phosphorus contaminants are separated from low-boiling phosphorus contaminants in a disproportionation reaction effluent by a post-disproportionation reactor silicon tetrachloride separator. The high-boiling phosphorus contaminants are separated from silicon tetrachloride and intermediate-boiling phosphorus contaminants in a high-boiling phosphorus separator. The high-boiling phosphorus contaminants are discarded. The intermediate-boiling phosphorus contaminants are recycled to the disproportionation reactor. The intermediate-boiling phosphorus contaminants are converted to high-boiling phosphorus contaminants by the disproportionation reactor. Dichlorosilane is separated from trichlorosilane in the post-disproportionation reactor trichlorosilane-rich streamby a post-disproportionation reactor dichlorosilane/trichlorosilane separator to yield a post-disproportionation reactor dichlorosilane-rich/trichlorosilane-depleted material and a post-disproportionation reactor trichlorosilane-rich/dichlorosilane- depleted material. Dichlorosilane concentration in the post- disproportionation reactor dichlorosilane-rich/trichlorosilane-depleted material is determined. Trichlorosilane concentration in the post- disproportionation reactor trichlorosilane-rich/dichlorosilane-depleted material is determined. The post-disproportionation reactor dichlorosilane-rich/trichlorosilane-depleted material is essentially pure dichlorosilane. The dichlorosilane-rich/trichlorosilane-depleted material is stored in a dichlorosilane storage system. The trichlorosilane-rich/dichlorosilane-depleted material is stored in a trichlorosilane storage system. The dichlorosilane-rich/trichlorosilane-depleted material is mixed with trichlorosilane-rich/dichlorosilane-depleted material to yield a CVD reactor feed, and the feed is supplied to the CVD reactor. The dichlorosilane-rich/trichlorosilane-depleted material is mixed with trichlorosilane-rich/dichlorosilane-depleted material from the dichlorosilane storage system. The dichlorosilane-rich/trichlorosilane-depleted material is mixed with the trichlorosilane-rich/dichlorosilane-depleted material from the trichlorosilane storage system. The dichlorosilane-rich/trichlorosilane-depleted material is mixed with the trichlorosilane-rich/dichlorosilane-depleted material to yield a CVD reactor feed by adjusting a ratio of chlorine to silicon in the CVD reactor feed. Cooling system (II) comprises post-CVD reactor heat exchanger (II). Hydrogen is separated from effluent mixture from the post-CVD reactor in situ hydrogen chloride reactor by a post-CVD reactor silicon tetrachloride absorber/hydrogen separator. Hydrogen separated by the post-CVD reactor silicon tetrachloride absorber/hydrogen separator is saturated with trichlorosilane. Hydrogen from the post-CVD reactor silicon tetrachloride absorber/hydrogen separator is mixed with a feed to CVD reactor. The temperature of trichlorosilane is adjusted prior to feeding trichlorosilane to the silicon tetrachloride absorber/hydrogen separator, to 35 degrees C. Trichlorosilane is cooled and vapor phase lower boiling materials are vented from trichlorosilane. A high-boiling phosphorus separator separates high-boiling phosphorus contaminants.