Patent Publication Number: US-2023159419-A1

Title: Ethylene oxide purification

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. Divisional application of U.S. application Ser. No. 17/760,680, filed Mar. 15, 2022, which is the U.S. National Phase application of PCT/US2020/49136, filed 3 Sep. 2020, which claims priority to U.S. Provisional Patent Application No. 62/900,952, filed 16 Sep. 2019, entitled “ETHYLENE OXIDE PURIFICATION” the contents of each of which are incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a method of improving the purity of the ethylene oxide (EO) recovered from the gaseous effluent from an ethylene oxide reactor of a combined ethylene oxide/ethylene glycol plant when the purified gaseous effluent is recovered as aqueous ethylene oxide solutions and used as feeds to both ethylene oxide purification columns and to ethylene glycol units that are integrated into the combined ethylene oxide/ethylene glycol plant. The method relates to improving both the ethylene oxide stripping system and the ethylene oxide reabsorption system to reduce operating costs and provide simplifications to the overall operation of the combined ethylene oxide/ethylene glycol plant. Such ethylene oxide stripping and ethylene oxide reabsorption systems are commonly used in the EO recovery step to produce two pure ethylene oxide-water feed streams with differing EO concentrations. One stream is used as feed to a column or series of columns that further purify the EO to produce high purity EO and the other, lower concentration stream is used as the feed to an ethylene glycol plant that produces polyester fiber grade ethylene glycol. 
     BACKGROUND OF THE INVENTION 
     When ethylene oxide (EO) is produced by silver-catalyzed, vapor-phase partial oxidation of ethylene by molecular oxygen, the EO product is in a hot gaseous effluent stream from the reactor. The ethylene oxide content in this reactor effluent is quite low and therefore requires recovery, further purification and must be concentrated as well. This recovery of the ethylene oxide from the reactor effluent gas, as conventionally practiced, involves cooling of the reaction effluent gases in a heat exchanger train and absorption in water. The water absorption step produces a very dilute EO solution together with various impurities. Ethylene oxide is then stripped from this dilute solution and the EO gas thus stripped is then reabsorbed in recycled EO-free process water to produce the more concentrated EO solutions required to be fed to the columns producing the high purity EO and also to be fed to the plant that produces fiber-grade ethylene glycol. 
     As described in U.S. Pat. No. 7,569,710, the entire contents of which are incorporated by reference herein for all purposes, the cooled EO reactor effluent gas is sent to an EO absorber, which may contain a quench section in the lower part of the absorber column where the reactor effluent is scrubbed with a recirculated, cooled aqueous alkaline stream to absorb and neutralize acidic compounds such as acetic and formic acids and also to absorb almost all of the trace amount of by-product formaldehyde (which is present as methylene glycol) prior to moving through the upper section of the EO absorber column. Also as disclosed in U.S. Pat. No. 7,569,710, the reactor effluent may be passed through a separate quench column where the same scrub with an alkaline stream is performed, before being passed to the absorber. 
     A liquid bleed stream is removed from the quench (also called a scrubber or a quench scrubber) step. This is done whether a separate alkaline quench column is used or if the alkaline quench scrubbing step is performed in the bottom of the absorber column. The purpose of this bleed is to remove the extra water that would otherwise accumulate in the recirculation loop. This water is formed as a by-product during the oxidation of ethylene to ethylene oxide. This by-product water is almost all condensed during the quenching/scrubbing step. 
     Then, the treated vaporous reaction stream from the alkaline quench scrub step is passed through liquid de-entrainment devices and fed to a water wash step where it is washed with fresh process water to remove any entrained quench liquid and to absorb any remaining formaldehyde vapor. After this washing step, the vaporous reaction stream is passed through liquid de-entrainment devices and then fed to the bottom of an ethylene oxide absorber column, where it is counter-currently washed with recirculated, EO-free process water to absorb the ethylene oxide and produce a high-purity EO-containing absorbate. The quench bleed, which in addition to the water mentioned above, contains typically 0.5-5 wt. % of EO and comparable concentrations of glycol and sodium salts as well as a low concentration of formaldehyde (as methylene glycol) is sent to a quench bleed stripper where the EO is stripped out and recovered. The EO-free quench stripper bottoms can then be disposed of as a waste stream or processed separately for recovery of the small quantity of crude ethylene glycol that it contains. 
     In EO reaction systems that include an EO stripper bypass stream flow scheme (as described in U.S. Pat. No. 7,569,710), the EO absorbate (i.e. a water/ethylene oxide solution) from the EO absorber is pure enough to be fed directly to the purification column(s) that produce high purity ethylene oxide (HPEO) and/or reactors that produce ethylene glycol. However, while the purity of this aqueous solution is acceptable, the concentration of EO in the water is normally too low for either of these process routes to be economically feasible. Accordingly, in these plants, only part of the dilute EO absorbate is sent directly to the EO reabsorber, bypassing the main EO stripper. The balance of the EO absorbate is fed to the EO Stripper to produce concentrated EO vapor that, when reabsorbed in the bypassed EO absorbate, will raise its EO concentration to the higher levels required in the feed to an EO purification system and/or a glycol reactor. 
     The concentrated EO bottoms from the EO reabsorber, which contain small concentrations of absorbed CO 2  and reaction gases, are then normally fed to a single lights stripper in which low pressure steam is injected to strip out the CO 2  and other light components before being pumped to the high purity ethylene oxide (HPEO) purification column and/or the reactor that produces ethylene glycol, also referred to as monoethylene glycol (MEG). 
     The most suitable EO concentration in the feed to a large, single high purity ethylene oxide (HPEO) purification column, such as described in U.S. Pat. No. 4,134,797, the entire contents of which are incorporated by reference herein for all purposes, is normally in the range of 10-13 wt. % in water, whereas the normal EO concentration range in the feed to an MEG reactor would be in the range 6-10 wt. % EO in water. The higher water to EO ratio is desirable in order to limit the production of heavier glycols. 
     Accordingly, when both the column that produces high purity ethylene oxide and the reactor that produces fiber grade monoethylene glycol are operating at comparable ethylene oxide equivalent (EOE) capacities with similar net feed rates of ethylene oxide, but with the different required EO concentrations in their feed streams, the EO reabsorber would normally be operated to produce EO reabsorber bottoms feed to the single lights stripper with the higher EO concentration required by the HPEO Column. This is the controlling EO concentration that therefore sets and limits the amount of EO absorbate that can bypass the EO stripper in a plant that uses this process scheme. The desired more dilute EO feed to the MEG reactor is then produced by mixing part of the bottoms from the lights stripper with EO-free recycle process water. 
     However, even with the benefits of utilizing the EO process that incorporates the EO bypass flow scheme, there is still scope for process improvements in terms of energy efficiency and simplification of the process. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved method of purification of ethylene oxide which comprises quenching and washing the ethylene oxide reactor effluent by contact with a recirculated, cooled, aqueous alkaline stream and a water wash, passing the gaseous ethylene oxide containing stream obtained from the alkaline quenching wash to an ethylene oxide absorber. In the ethylene oxide absorber, the ethylene oxide is absorbed in once-through EO-free process water to form a dilute aqueous ethylene oxide-containing absorbate solution. Next, a portion of this ethylene oxide-containing dilute absorbate solution is stripped in an EO stripper to produce a gaseous ethylene oxide overhead vapor. The gaseous ethylene oxide overhead vapor is then passed to an ethylene oxide reabsorber where the ethylene oxide is absorbed in another portion of the dilute aqueous ethylene oxide-containing absorbate which bypassed the EO stripper. Thus, an EO aqueous reabsorbate solution having a higher content of EO than the ethylene oxide-containing dilute absorbate solution emerges from the EO reabsorber. A portion of this enriched-in-EO reabsorbate solution passes to a first lights stripper designed to remove dissolved carbon dioxide with a lights-free, concentrated ethylene oxide-containing solution being recovered for use as high-purity feed to only a high purity EO distillation system. 
     In a preferred embodiment, from 10-90%, more preferably 20-80%, and most typically 25-35% of the dilute ethylene oxide solution obtained from the absorber is passed directly to the reabsorber, and never passes through the EO stripper, thus reducing the stripping steam consumed in the EO Stripper by 25-35%. 
     Additionally, another portion of the reabsorber bottoms (i.e. the EO enriched absorbate) is mixed with additional bypassed dilute EO absorbate (that bypasses both the EO stripper and the EO reabsorber) and an acetaldehyde-EO purge from the high purity EO distillation system. This gasified mixture is fed to a second lights stripper that will then produce lights-free aqueous bottoms containing a lower EO concentration than the feed to the high purity EO distillation system. This lower EO concentration is the correct, lower concentration of EO/higher concentration of water that the MEG reactor requires to reduce the yield of heavier glycols. This entire process which also serves to dilute the EO stream fed to the glycol reactor also substantially increases the total quantity of dilute EO absorbate that bypasses the EO stripper and therefore reduces the stripping steam that is required by the EO stripper. 
     In another preferred embodiment, an additional 5-60%, more preferably 7-40%, and most typically 10-25% of the dilute ethylene oxide solution obtained from the EO absorber bypasses both the EO stripper and the EO reabsorber and is mixed with surplus EO reabsorber bottoms and the acetaldehyde-EO purge stream from the HPEO Column and passed directly to a second lights stripper for use as feed to the glycol reactor, and never passes through the EO stripper or the EO reabsorber, thus reducing the stripping steam consumed in the EO stripper by an additional 10-25%. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows how the maximum potential EO stripper bypass rates (and the related stripper steam savings) are related to the EO concentration in the EO reabsorber bottoms; 
         FIG.  2    is a schematic representation of a flow scheme for an EO reaction system that includes an EO Stripper Bypass stream and a single Lights Stripper that produces the EO feeds for both the EO Purification Column and the MEG reactor; 
         FIG.  3    is a schematic representation of an exemplary embodiment of the invention showing a flow scheme which is the process as shown in  FIG.  2    with the addition of a second Lights Stripper; and 
         FIG.  4    is a graph showing the effect of increasing the water:EO ratio on the glycol reactor product distribution. 
     
    
    
     DETAILED DESCRIPTION 
     According to embodiments of the invention, incorporation of an additional lights stripper into a combined ethylene oxide/ethylene glycol plant that utilizes a stream that bypasses the ethylene oxide stripper column permits a greater percentage of the ethylene oxide to not only bypass the ethylene oxide stripper column, but also to bypass the ethylene oxide reabsorber column.  FIG.  1    shows how the maximum potential EO Stripper Bypass rates (and the related stripper steam savings) are related to the EO concentration in the EO Reabsorber bottoms. This plot demonstrates the energy savings that may be realized by the production scheme in  FIG.  3    as compared to the scheme in  FIG.  2   . This is because a portion of the EO absorbate from the initial EO absorber column  1300  can bypass both the EO stripper  1311  and the EO reabsorber  1327  in the  FIG.  3    scheme. In the  FIG.  2    scheme, a portion of the EO absorbate from the initial EO absorber column  300  can bypass only the EO stripper  311 . Therefore in the inventive scheme, shown in  FIG.  3   , the total amount of EO absorbate that can be bypassed is 40-60 weight % of the process stream compared to 20-30% weight percent in the  FIG.  2    scheme. 
     An exemplary ethylene oxide recovery process as described in U.S. Pat. No. 7,569,710 that has an ethylene oxide bypass stream is shown in  FIG.  2   . This process will be described in detail, since the inventive process comprises certain elements of this process. 
     Generally, the process as shown in  FIG.  2    depicts a process of purifying and concentrating the effluent from a catalytic reactor that oxidizes ethylene gas to ethylene oxide, but includes an ethylene oxide bypass stream, i.e. a stream that bypasses the main EO stripping column. As is known in the art, impurities in the reaction effluent that are byproducts of the oxidation reaction and other side reactions may include water, carbon dioxide, various aldehydes, e.g. formaldehyde and acetaldehyde, as well as organic acids, among others. These need to be removed and in addition, the purified ethylene oxide needs to be provided in the correct concentrations in order to be suitable for further purification steps, and/or to be fed to a reactor that produces high grade ethylene glycol, or mono ethylene glycol (also referred to as EG or MEG) that is suitable to be used in the production of fiber-grade polyester. Utilizing the process described below allows some of the ethylene oxide stream from an ethylene oxide absorber to bypass an ethylene oxide stripper column, be diluted with clean process water and go directly to a glycol reactor. 
     Referring to  FIG.  2   , effluent gas containing ethylene oxide from an EO reaction system (not shown) is introduced directly into the bottom section of a quench scrub section  352  of a column  300  via conduit  302 . Note that in this embodiment, the quench (or quench scrub) section  352  comprises the bottom of the column  300 , but in alternative embodiments, the quench scrubbing step could be performed in a separate dedicated column. Quench bottoms solution is recirculated via conduits  353  and  355 A, through cooler  354 , and conduits  355 B and  357  to the top of the quench scrubbing section  352  of the column  300 . This is clear in  FIG.  2    where conduit  357  is shown entering the absorber column  300  at a point above the bottom, but well below the top of column  300 . 
     An alkaline solution, in the form of concentrated sodium hydroxide (for instance, 10-20 wt. % as an aqueous solution) is injected into the recirculated quench solution via conduit  356 . The NaOH neutralizes dissolved CO 2  which is present as a contaminant and thus converts into sodium carbonate and sodium bicarbonate. The basic solution also neutralizes organic acids, which are likewise are present as contaminants from the oxidation reaction. A cooled, scrubbed vapor, which is free of organic acid vapor, but contains some formaldehyde and entrained quench liquid, thus emerges from the top of the quench section  352  and is passed through a demister unit  359  to remove the entrained liquid. This cooled, scrubbed vapor then enters an upper water wash section  361  above the quench section  352  of the column  300 . 
     The filtered quench gas is then washed in water wash section  361  with fresh purified water, that is introduced via conduit  362 . This water removes any remaining entrained quench liquid and absorbs most of the remaining formaldehyde and water-soluble heavy impurities. A countercurrent water wash will preferably be used for this step. This countercurrent water wash step may optionally be preceded by a recirculated water wash section for maximum vapor-liquid contact. The net wash water from the bottom of the water wash section(s) may drain into the top of the lower quench section  352 . This water thus dilutes the concentration of formaldehyde and other undesirable impurities in the quench liquid and accordingly reduces the equilibrium concentration of these impurities in the scrubbed gas feed to the EO absorber section  303  located in the upper section of column  300 . The net quench bottoms solution bleed stream, containing condensed water, wash water, absorbed impurities and some ethylene oxide, flows via conduits  353  and  365  to a quench bleed stripper  366 . 
     The quenched/scrubbed washed gas from the top of the water wash section, is passed through a second demister unit  363  to remove any entrained wash water from conduit  362 . This gas enters the EO absorber section  303 . Cold EO-free absorption water is introduced into the upper section of absorber section  303  via conduit  321 B. The quenched/scrubbed washed gas (i.e. reaction effluent gas after passing through sections  352  and  361  of column  300 ) is counter-currently contacted by the cold absorbent water to absorb almost all of the ethylene oxide entering the absorber section  303  of column  300 . The non-condensable, non-absorbable-in-water gas remaining from the reaction effluent gas leaving the top of absorber  303  is essentially free of ethylene oxide and is returned to the EO reaction system via conduit  304 . The dilute EO-water solution (i.e. the EO as absorbate) that is formed in absorber  303  is withdrawn from the bottom of the absorption section via conduit  305 . 
     In the flow scheme shown in  FIG.  2   , part of the EO absorbate in conduit  305  bypasses EO stripper  311  and flows directly to an EO reabsorber bottoms recycle cooler  329  via conduits  310  and  333 A. The amount bypassed will vary between 25-35 weight % of the total absorbate solution exiting at conduit  305 . The amount of absorbate solution that bypasses the EO stripper  311  depends on the EO concentration in the absorbate solution and depends on the desired EO concentration in the reabsorber bottoms (and feed to an EO purification unit or a glycol reactor). The amount bypassed can be determined using tables, equations, or graphs. 
     The balance of the absorbate solution (i.e., the portion that was not bypassed and sent to the cooler  329 ) is introduced into an EO stripper preheater exchanger  307  via conduit  308 , and the hot rich absorbate solution, from preheater exchanger  307  is fed to an upper portion of EO stripper  311 , via conduit  309 . Stripping steam, which may be extracted from a downstream glycol plant, is introduced to a lower portion of stripper  311  via conduit  338 B or the stripping steam may be generated internally by a reboiler (not shown). By countercurrent contact of the absorbate solution and steam within stripper  311 , the absorbate solution is stripped of the ethylene oxide, which together with steam, carbon dioxide, light ends, and trace impurities is withdrawn from the top of stripper  311  via conduit  313 A. The stripped (lean) absorbate solution, now comprising water essentially free of ethylene oxide, is withdrawn from the bottom of stripper  311  via conduit  319 A and cooled in heat exchanger  307 , giving up heat to the rich absorbate solution feed. The cooled lean absorbate solution from cooler  307  is passed via conduit  319 B, combined with recycled water from the glycol plant and/or the EO purification tower  345  in conduit  321 A to heat exchanger  320 , where it is further cooled and the total lean (in EO) absorbate solution stream is recycled back to the top of absorber section  303  in column  300  via conduit  321 B. 
     The rich absorbate solution fed to the EO stripper  311  in conduit  309  may contain from about 1 to about 5 wt. % of ethylene oxide and the stripper  311  is operated to recover more than 95% and usually more than 99% of the ethylene oxide contained in the rich absorbate solution fed to the stripper  311 . Although the stripper  311  normally operates at close to atmospheric pressure, the temperatures in the stripper column  311  are high enough to cause about 0.5-3.0% of the total amount of EO in the solution of feed to thermally hydrate (i.e. react with the water) to form mainly monoethylene glycol. The glycol produced in the EO stripper will build up to a low, equilibrium concentration in the EO absorber and EO stripper recycle water system that is controlled by the amount of the absorbate solution that bypasses (via stream  310 ) the stripper, since this bypass stream effectively acts as a very large cycle water glycol bleed. 
     The overhead vapor withdrawn via conduit  313 A from the EO stripper  311 , usually contains about 20 to 30 mole % of ethylene oxide. The primary diluent in this vapor stream is water, although about 7-10 mole % is generally non-condensable gases. These non-condensable gases predominantly comprise CO 2 , but also may include nitrogen, argon, oxygen, methane, ethylene and ethane. The overhead vapor stream in conduit  313 A from stripper  311  is cooled in heat exchanger  312 . The heat exchanger  312  will condense some of the water in the overhead vapor emerging from the stripper  311  and then a total effluent mixture of the uncondensed EO-rich portion of the vapor and the condensate flows from the heat exchanger  312  via conduits  313 B and  316  to an EO reabsorber  327 . 
     The net quench bleed bottoms stream in conduit  353  from the quench scrubber portion  352  of column  300  comprises mainly excess water produced as a byproduct of the EO reaction that is partially condensed in the quench scrubber portion  352  plus makeup wash water. The quench bleed bottoms also comprises alkaline salts and absorbed ethylene oxide. This stream is sent, via conduit  365 , to the small purge stripper  366  where the absorbed ethylene oxide is stripped out, using stripping steam that is injected into purge stripper  366  via conduit  371 . The stripping steam for purge stripper  366  may alternatively be generated in a reboiler (not shown). A heat exchanger may be also used to preheat the stream fed to the purge stripper  366  in order to reduce the reboiler heat duty and/or to reduce the amount of stripping steam needed. 
     The overhead vapors emerging from the top of purge stripper  366  via conduit  367  are cooled in heat exchanger (or condenser)  368  to a temperature that is low enough such that a substantial part, preferably at least 60%, of the water contained in the overhead vapor from the purge stripper  366  is condensed. This condensate phase from heat exchanger/condenser  368  is contaminated with dissolved salts and formaldehyde and is drained or pumped back into the upper portion of the purge stripper  366  via conduit  369 . 
     The remaining uncondensed portion of the cooled purge stripper overhead vapor is withdrawn from the heat exchanger/condenser  368  via conduit  370 . As can be seen in  FIG.  2   , this uncondensed portion of the cooled purge stripper overhead vapor in conduit  370  is then combined with the EO and condensate mixture that emerges via conduit  313 B from the heat exchanger  312  on the overhead from the main EO stripper  311 . The stream in conduit  381 , which is an overhead vapor stream emerging from a lights stripper  380 , is also combined (via conduit  381 A) with the streams in conduits  370  and  313 B and a formaldehyde-rich stream in conduit  347  (also via conduit  381 A) that emerges from the top of an EO purification unit  345 . These four combined streams (conduits  370 ,  313 B,  381  and  347 ) are introduced, via conduit  316 , into a lower portion of the reabsorber  327 . The EO-free aqueous bottoms from purge stripper  366 , which contains most of the formaldehyde, salts, and a small amount of ethylene glycol are sent to waste treatment or technical grade glycol recovery via conduit  372 . 
     Some recycled cold water is introduced to an upper portion of the reabsorber  327  via conduit  351 B. Within the upper portion of the reabsorber  327 , the combined light gases in conduit  316  from the overhead vapor streams from the EO stripper  311 , the quench purge stripper  366 , the lights stripper  380  and the EO purification column  345  and the cold water from conduit  351 B are counter-currently contacted to absorb the maximum amount possible of the ethylene oxide contained in the combined vapor streams of conduit  316 . The non-condensed gases emerging from the top of reabsorber  327 , that normally contain only trace amounts of ethylene oxide are vented via conduit  328 . Since this vent stream in conduit  328  contains a significant amount of hydrocarbons, comprising mainly ethylene and methane, it is preferably compressed and recycled back to the EO reactor gas system for (partial) recovery of the contained ethylene. In some plants, particularly those that have a small production capacity, the reabsorber vent gas in conduit  328  may be vented to the atmosphere, or preferably incinerated to avoid atmospheric pollution. 
     The EO-rich reabsorbate is withdrawn from the bottom of reabsorber  327  via conduit  330 . This reabsorbate is pressurized using a pump (not depicted) and divided into two portions shown as conduits  331  and  332 . A portion that is the net bottoms product (i.e., second portion of the bottoms are cooled and recycled back to the EO reabsorber  327 ) flows through conduit  331  to the top of the lights stripper  380 . The aqueous reabsorbate bottoms comprises not only the reabsorbed ethylene oxide vapor but also comprises acetaldehyde and dissolved carbon dioxide as well as dissolved non-condensable gases. The mass balance of water in the absorber-stripper system may be maintained by injecting low pressure process steam extracted from the glycol plant directly into the EO stripper  311  to provide up to 100% of the stripping vapor required and/or by recycling water from the glycol plant evaporation section for use as absorption water. 
     As described in U.S. Pat. No. 4,134,797, the portion of the EO-rich reabsorbate withdrawn via conduit  330  that goes into conduit  331  will first pass into the lights stripper column  380  (also referred to as the carbon dioxide stripping column). In the lights stripper column  380  the liquid in conduit  331  is stripped of CO 2  and light gases, such as ethane and ethylene. Stripping steam is supplied to the bottom of the lights stripper column  380  from an evaporation train  337  via conduits  338  and  338 A. The CO 2 -rich EO vapor that exits lights stripper  380  via conduit  381  is combined with the overhead vapor purge from the EO purification column  345  in conduit  381 A, is mixed with the main EO feed vapor stream in conduit  316  and then enters the bottom of reabsorber  327 , as described above. The essentially gas-free bottoms, (purified aqueous solution of EO) from the carbon dioxide (lights) stripping column  380  are then pumped to a glycol reaction unit  335  via conduits  382 ,  383 , and  334  and to the EO purification unit via conduits  382 ,  344 A and  3448 . Note however, that in this process, this bottoms stream in conduit  383  is too concentrated in EO for the ethylene glycol reactor  335  and that therefore it is diluted with process recycle water provided via conduit  339 A that originates from the evaporation train  337  to provide the final feed in conduit  334  to the glycol reactor  335 . 
     In the reabsorber unit  327 , the recycled reabsorbate flowing through conduit  332  is combined with bypassed rich absorbate in conduit  333 A, cooled in heat exchanger  329  and introduced as cold liquid to a middle portion of reabsorber  327  via conduit  3338 . Heat exchanger  329  maintains the reabsorber in heat balance to achieve the pre-determined bottom reabsorbate temperature and hence the desired concentration of ethylene oxide. Depending on the operating pressure of the reabsorber  327  and the amount of bypassed dilute absorbate in conduit  310 , the ratio of reabsorbate recycled via conduit  332  to the net reabsorbate withdrawn via conduit  331  will range from as low as no recycle to as high as a ratio of 3:1. The maximum bypass of EO-rich absorbate (not shown) may be achieved when the bypassed absorbate in stream  310  is separately cooled and introduced into reabsorber  327  at a point above the recycled bottom reabsorbate. 
     The reabsorbate in conduit  344 A (from the bottoms of stripper  380  via conduit  382 ) flowing to EO purification is preheated in heat exchanger  343  and fed to the lower part of the single EO purification column  345  via conduit  3448 , where it is separated into a purified side-stream EO liquid product (stream  346 ), and a small formaldehyde-rich crude EO overhead vapor purge stream (stream  347 ) that is recycled back to the reabsorber  327  for recovery of the EO, as described above. In addition, an impure side stream of acetaldehyde-rich EO is removed from the EO purification column  345  via conduit  341  to purge the acetaldehyde. Although not shown, this stream is mixed with the stream in conduit  334  and sent to the glycol reaction unit  335 . The EO-free bottoms water stream containing most of the trace amount of formaldehyde that was in the feed to the EO purification column  345 , is withdrawn via conduit  349 A, cooled in heat exchanger  343  and a portion is recycled to the reabsorber  327  via conduits  3498 ,  351 A, and  3518 . The EO free bottoms not required in the reabsorber  327  are recycled via conduit  342  and combined with recycle condensate from the evaporation train  337  in conduit  3398 . 
     In the glycol reactor  335 , the ethylene oxide in the degasified lights stripper bottoms feed that has been mixed with recycle evaporator condensate via conduit  339 A to increase the water-to-EO ratio (as required to reduce the formation of heavy glycols) and the small acetaldehyde-EO purge in conduit  341  from the EO purification unit  345  is almost completely reacted with water to form mixed ethylene glycols. The effluent from the glycol reactor  335  is fed to the multiple-effect evaporation train  337  in which the water is separated from the concentrated crude glycol that is then fed to glycol purification (not shown) via conduit  340 . Part of the water separated in evaporation train  337  is recycled back to the EO plant as steam via conduit  338  and injected directly into the lights stripper  380  (via conduit  338 A) and EO stripper  311  (via conduit  338 B) to provide up to 100% of the required stripping steam. The balance of the recovered evaporation water is recycled back to the EO plant via conduit  339  and is combined with the balance of the bottoms from EO purification column  345  in conduit  3396 . To provide the required flow of absorption water to the EO absorber  303 , makeup recycle water is added via conduits  3396 ,  339 C,  321 A and  321 B and surplus recycle water is sent to a recycle surge tank (not shown) via conduit  339 D. 
     An embodiment of the present invention as applied to plants that produce both EO and mono-ethylene glycol as described above is shown in  FIG.  3   . 
     Referring to  FIG.  3   , effluent gas from the EO reaction system (not shown) containing ethylene oxide (EO) is introduced directly into a bottom of quench/scrubbing section  1352  of column  1300  via conduit  1302 . Quench bottoms solution is recirculated via conduits  1353  and  1355 A, cooler  1354 , and conduits  1355 B and  1357  to the top of the quench scrubbing section  1352 . Concentrated sodium hydroxide (10-20 wt. % aqueous solution) is injected into the recirculated quench solution via conduit  1356  to react with dissolved CO 2  and be converted into sodium carbonate and bicarbonate, which then neutralize byproduct organic acids. The cooled, scrubbed vapor from the top of the quench section  1352 , which is free of organic acid vapor, but contains some formaldehyde and entrained quench liquid is passed through a demister unit  1359  to remove the entrained liquid and then enters the upper wash section  1361  above the quench section  1352  of the column  1300 . 
     The filtered quench gas is then washed with fresh purified water, introduced via conduit  1362 , to completely remove any remaining entrained quench liquid and to absorb most of the remaining formaldehyde and heavy impurities. A countercurrent water wash will preferably be used, which can be preceded by a recirculated water wash section for maximum vapor-liquid contact. The net wash water from the bottom of the water wash section(s) in column  1300  may drain into the top of the lower quench section  1352 , diluting the concentration of formaldehyde and other undesirable impurities in the quench liquid and reducing the equilibrium concentration of these impurities in the scrubbed gas feed to the upper part of column  1300 . The upper part of column is an EO absorber section  1303 . The net quench bottoms solution bleed, containing condensed water, wash water, absorbed impurities and some ethylene oxide, flows via conduits  1353  and  1365  to a quench bleed stripper  1366 . 
     The washed vapor from the water wash section  1361 , is passed through a demister unit  1363  in column  1300  to remove any entrained wash water and enters the EO absorber section  1303  of column  1300 . Cold EO-free absorption water is introduced into the upper section of absorber section  1303  via conduit  1321 B and the reaction effluent gas is counter currently contacted by the water to absorb almost all of the ethylene oxide entering the absorber. Note that this water in conduit  1321 B may be recycled from an evaporation train  1337  which follows a glycol reactor  1335 . The non-condensable reaction gas, comprising inter alia, unreacted ethylene, leaving the top of absorber section  1303  is essentially free of ethylene oxide and is returned to the EO reaction system via conduit  1304 . The dilute EO-water solution (i.e. the EO absorbate) that is formed in absorber section  1303  is withdrawn from the bottom of the absorption section  1303  via conduit  1305 . 
     Optionally, the three sections of column  1300  may be comprised of two or three separate columns. 
     Part of the EO absorbate in conduit  1305  bypasses EO stripper  1311  and flows directly to the EO reabsorber bottoms recycle cooler  1329  via conduits  1310 ,  1326  and  1333 A. The amount of EO absorbate in conduit  1305  that bypasses the EO stripper  1311  may vary between 15-75%. The amount of EO absorbate in conduit  1305  that can bypass the EO stripper  1311  depends on the EO concentration in the EO absorbate and the desired EO concentration in the reabsorber  1327  bottoms in conduit  1330  (and glycol reactor feed), and can be determined using tables, equations, or graphs. 
     In this inventive flow scheme, a significant additional part of the EO absorbate that exits the bottom of column  1300  will bypass both the EO stripper  1311  and the EO reabsorber  1327  and a first lights stripper  1380  via conduit  1386  and go directly to a second lights stripper  1390 . As can be seen in  FIG.  3   , this EO absorbate that has bypassed the EO stripper  1311 , the EO reabsorber  1327  and a first lights stripper  1380  via conduit  1386  is used instead of recycled process water to dilute a portion of the more concentrated bottoms from EO reabsorber  1327  provided by conduit  1387  in conduit  1388 . By controlling the flow of bypassed absorbate in conduit  1386 , the diluted EO absorbate that ultimately emerges as the bottoms from the second lights stripper  1390  has the desired lower EO concentration that may be fed directly to the glycol reactor  1335 . The addition of the second lights stripper  1390  to degasify only the feed to the MEG reactor  1335  is therefore a significant process improvement from the flow scheme as shown in  FIG.  2    and significantly increases the amount of EO absorbate that can bypass the EO stripper  1311 . This additional amount of process stream that bypasses the EO stripper  1311  means that less heat and electrical energy is needed to operate the EO stripper  1311  and the EO reabsorber  1327  compared to a process that does not utilize the second lights stripper  1390  (also referred to as the MEG lights stripper). Notably, the total energy load on both strippers  1380  and  1390  is approximately the same as the total of the single stripper  380  in  FIG.  2   . 
     The balance of the EO absorbate that exits the column  1300 , i.e., the portion of the EO absorbate stream from conduit  1305  that does NOT bypass the EO stripper  1311  and the EO reabsorber  1327 , is introduced into an EO stripper preheater exchanger  1307  via conduit  1308 , and the hot EO absorbate from preheater  1307  is fed to an upper portion of the EO stripper  1311 , via conduit  1309 . Low pressure stripping steam extracted from a downstream glycol plant  1335  is introduced to a lower portion of EO stripper  1311  via conduit  1338 B. The stripping steam may optionally be generated internally by a reboiler (not shown). The water balance in the absorber-stripper system may be maintained by directly injecting low pressure process steam extracted from the glycol plant  1335  directly into the EO stripper  1311  to provide up to 100% of the stripping vapor required and/or by recycling water from the glycol plant evaporation section  1337  for use as absorption water. 
     By countercurrent contact of the EO absorbate and steam within the EO stripper  1311 , the EO absorbate is stripped of the ethylene oxide, which together with steam, carbon dioxide, light ends and trace impurities is withdrawn from the top of the EO stripper  1311  via conduit  1313 A. The stripped absorbate, now essentially free of ethylene oxide and thus comprising mostly water with a small concentration of ethylene glycol, is withdrawn from the bottom of the EO stripper  1311  via conduit  1319 A and cooled in heat exchanger  1307 , giving up heat to the rich absorbate feed. The cooled lean aqueous absorbate from the heat exchanger  1307  is passed via conduit  1319 B, combined with recycled water from the evaporation train  1337  of the glycol plant and the EO purification tower  1345  via conduit  1339 C, and finally, in conduit  1321 A is passed to heat exchanger  1320 , where it is further cooled and the total lean aqueous absorbate stream is recycled back to top of absorber section  1303  via conduit  1321 B. 
     The rich (in EO) absorbate feed in conduit  1309  to the EO stripper  1311  may contain from about 1 to about 5 wt. % of ethylene oxide and the EO stripper  1311  is operated to recover more than 95% and usually more than 99% of the ethylene oxide contained in the feed. Although the EO stripper  1311  normally operates at close to atmospheric pressure, the temperatures in the EO stripper column  1311  are high enough to thermally hydrate in the range of 0.5-3.0% of the EO feed to ethylene glycol. The glycol thus produced in the EO stripper  1311  will build up to a low, equilibrium concentration in the EO absorber—EO stripper recycle water system that is controlled by the amount of the absorbate that bypasses the EO stripper  1311  via stream  1310 , which acts as a very large cycle water/glycol bleed. 
     The overhead vapor withdrawn from the EO stripper  1311  via conduit  1313 A usually contains about 20 to 30 mole % of ethylene oxide. The primary diluent in this vapor stream is water, although about 7 to 10 mole % can be generally referred to as non-condensable gases, and is predominantly CO 2 , but also includes nitrogen, argon, oxygen, methane, ethylene and ethane. The EO stripper  1311  overhead vapors are cooled in heat exchanger  1312  and the total effluent mixture of uncondensed vapor and condensate flows via conduits  1313 B and  1316  to the EO reabsorber  1327 . 
     The net bleed bottoms stream from the quench section  1352  of column  1300  comprises mainly the water formed as a byproduct of the oxidation of ethylene to EO that is partially condensed in the quench scrubber section  1361 / 1352  plus makeup wash water from section  1361  and also contains some alkaline salts and absorbed ethylene oxide. This stream is sent, via conduit  1365 , to a small purge stripper  1366  where the absorbed ethylene oxide is stripped out, using stripping steam injected via conduit  1371 , or generated in a reboiler (not shown). A purge stripper feed/bottoms heat exchanger may be also used to reduce the reboiler heat duty and/or the amount of stripping steam. The overhead vapors from purge stripper  1366  are cooled in a heat exchanger  1368  to a temperature such that a substantial part, preferably at least 60%, of the contained water is condensed. The contaminated condensate phase from the condenser  1368  is drained or pumped back into the upper portion of the purge stripper  1366  via conduit  1369 . The uncondensed overhead vapor from purge stripper  1366  is withdrawn from the condenser  1368  via conduit  1370 , combined with the EO and condensate mixture from condenser  1312  and the recycled EO vapor in conduit plus the contents of conduit  1381 A and introduced into a lower portion of the EO Reabsorber  1327  via conduit  1316 . Conduit  1381 A contains the combined vented vapors from the first lights stripper  1380  (which produces feed to the high purity ethylene oxide (HPEO) column  1345 ), the second lights stripper  1390  (which produces the feed to the monoethylene glycol plant  1335 ) and the HPEO column  1345  in conduit  1316  and introduced into a lower portion of the EO reabsorber  1327 . The EO-free aqueous bottoms from the purge stripper  1366 , containing most of the formaldehyde, salts, and a small amount of ethylene glycol are sent to waste treatment or technical grade glycol recovery via conduit  1372 . 
     Some recycle cold water is introduced to an upper portion of the EO reabsorber  1327  via conduit  13518 . Within the upper portion of the EO reabsorber  1327 , the light gases in the overhead vapor from EO stripper  1311  and the water from conduit  1351 B are counter-currently contacted in order to absorb the maximum amount possible of the ethylene oxide contained in the vapor into the water. The non-condensable gases emerging from the top of the EO reabsorber  1327 , normally containing only trace amounts of ethylene oxide are vented via conduit  1328 . Since this vent stream in conduit  1328  contains a significant amount of hydrocarbons, comprising mainly ethylene and methane, it is preferably compressed and recycled back to the EO reactor gas system for maximum recovery of the contained ethylene. In some plants, particularly those of small production capacity, the reabsorber vent gas may be vented to atmosphere, or may be incinerated to avoid atmospheric pollution. 
     The EO-rich reabsorbate is withdrawn from the bottom of the EO reabsorber  1327  via conduit  1330 . This reabsorbate in conduit  1330  is pressurized using a pump (not depicted) and divided into three portions. The first portion of reabsorbate from EO reabsorber  1327  is recycled via conduit  1332 , mixed with EO bypass from conduit  1326  in conduit  1333 A, cooled in heat exchanger  1329  and fed to the middle of the EO reabsorber column  1327 . 
     The second portion of reabsorbate from EO reabsorber  1327  is the largest portion of the net bottoms product and flows through conduits  1331  and  1379  to the top of the first lights stripper  1380  (also referred to as the HPEO lights stripper  1380 ). 
     The third portion of reabsorbate from the EO reabsorber  1327  is the balance of the net bottoms product and flows through conduits  1331 ,  1387 ,  1388  and  1389  to the top of the second lights stripper  1390 , also referred to as the MEG lights stripper  1390 . Notably, the aqueous reabsorbate from EO reabsorber  1327  contains not only the reabsorbed ethylene oxide vapor from the EO stripper  1311 , but also contains dissolved carbon dioxide and non-condensable gases that need to be removed before the stream can be fed to the glycol reactor,  1335 . Degasifying the third portion of reabsorbate and the gasified diluent bypassed absorbate is the purpose of this second lights stripper  1390 . 
     The flow rate of the EO-rich reabsorbate from the EO reabsorber  1327  to the HPEO (first) lights stripper  1380  is controlled to supply only the exact quantity of EO feed required by the HPEO Column  1345 . In the first lights stripper  1380 , the reabsorbate feed to the HPEO column  1345  is stripped of carbon dioxide and other light gases using stripping steam that is supplied to the bottom of the column  1345  from the evaporation train  1337  via conduits  1338  and  1338 A. The gas-free bottoms from the first lights stripping column  1380  are then pumped and fed to the lower part of EO purification column  1345  via conduits  1344 A and  1344 B and preheater  1343 . 
     In the high purity EO (HPEO) purification column  1345 , the reabsorbate feed (conduit  1344 B) is separated into a purified side-stream EO liquid product (stream  1346 ), a small formaldehyde-rich crude EO overhead vapor purge stream (stream  1347 ) that is recycled back to the EO reabsorber  1327  for recovery of the EO, and an impure side stream of acetaldehyde-rich EO that is removed via conduit  1341  and sent to the MEG (second) lights stripper  1390  to be fed to the glycol reaction unit  1335 . An EO-free bottoms water stream containing most of the trace amount of formaldehyde in the purification column  1345  feed, is withdrawn from column  1345  via conduit  1349 A, cooled in heat exchanger  1343  and a portion is recycled to the EO reabsorber  1327  via conduits  13496 ,  1351 A, and  1351 B. The EO-free bottoms not required in the reabsorber  1327  is recycled via conduit  1342 , to be combined with recycle condensate from the evaporation train  1337  in conduit  13396 . 
     The balance of the total EO-rich reabsorbate withdrawn from EO reabsorber  1327  via conduit  1331  that is not fed to HPEO (first) lights stripper  1380  is withdrawn via conduit  1387 , mixed with the part of the total bypass absorbate that is withdrawn via conduit  1386  and after combining with the acetaldehyde-EO purge stream in conduit  1341  from a high purity EO column  1345 , the entire mixture is fed to the top of MEG (second) lights stripper  1390  via conduit  1389 . The concentration of the EO in the  1386  conduit is sufficiently low to dilute the feed mixture in conduit  1389  such that the bottoms product from the second lights stripper  1390  in conduit  1334  is the appropriate low EO concentration to be fed to the glycol reactor  1335 . Importantly, the EO/water in the  1386  conduit has bypassed both the EO stripper  1311  and the EO reabsorber  1327 . 
     Optionally, the lights-free acetaldehyde-EO purge stream in conduit  1341  (from high purity EO column  1345 ) can be injected into the bottom of the second lights stripper  1390  to minimize the amount of acetaldehyde that is contained in the overhead vapor from the second lights stripper  1390 . 
     Stripping steam is supplied from the evaporation train  1337  via conduits  1338  and  1338 C to the bottom of the MEG (second) lights stripper  1390 . The light gases that are stripped out exit the second lights stripper  1390  via conduit  1391  and are combined with formaldehyde-rich gas from the EO purification column  1345  in conduits  1391 A, CO 2  rich product from the HPEO (first) lights stripper  1380  in conduit  1381 A and then combined with vapor/liquid effluent from the cooler  1312  and the top vapor product of the small purge stripper  1366  in conduit  1316 , entering the bottom of the EO reabsorber  1327 . The gas-free bottoms product containing EO and water from the MEG (second) lights stripper  1390  is then pumped to the glycol reaction unit  1335  via conduit  1334 , as noted above. 
     In the glycol reactor  1335 , the ethylene oxide in the degasified second lights stripper  1390  bottoms is almost completely reacted with water to form ethylene glycols. The effluent from the glycol reactor  1335  is fed to the multiple-effect evaporation train  1337  in which the water is separated from the concentrated crude glycol that is then fed to a glycol purification process (not shown) via conduit  1340 . Part of the water separated in the evaporation train  1337  is recycled back to the various unit operations (as described above) of the EO plant as steam via conduits  1338  and injected directly into the HPEO (first) lights stripper  1380  (via conduit  1338 A), MEG (second) lights stripper  1390  (via conduit  1338 C) and the EO stripper  1311  (via conduit  1338 B) to provide up to 100% of the required stripping steam. Steam from the evaporation train  1337  may also be utilized for the high purity ethylene oxide distillation column  1345 . 
     The balance of the recovered evaporation condensate from the glycol evaporation train  1337  is recycled back to the EO plant via conduit  1339  and combined with the balance of the bottoms from the EO purification column  1345  in conduit  13396 . To provide the required flow of absorption water to the EO absorber section  1303 , makeup recycle water is added via conduits  13396 ,  1339 C,  1321 A and  1321 B and surplus recycle water is sent to a recycle surge tank (not shown) via conduit  1339 D. 
       FIG.  4    is a graph showing the effect of increasing the water:EO ratio on the glycol reactor product distribution, demonstrating the necessity of having a more dilute ethylene oxide and water concentration to feed the glycol reactor  335  or  1335 . 
     Non-limiting Aspects of the invention are as follows: 
     Aspect 1: A process for producing purified ethylene oxide (EO) and monoethylene glycol (MEG), the process comprising the steps of: 
     a) providing a quenched and alkaline treated and water washed vaporous reaction stream, wherein the quenched and alkaline treated and water washed vaporous reaction stream comprises EO, CO 2 , formaldehyde, and acetaldehyde; 
     b) contacting the quenched and alkaline treated and water washed vaporous reaction stream with water in an EO absorber to produce a first absorbate stream having a first EO concentration in water; 
     c) dividing the first absorbate stream into a first portion of the first absorbate stream, a second portion of the first absorbate stream, and a third portion of the first absorbate stream; 
     d) feeding the first portion of the first absorbate stream to an EO stripper and contacting the first portion of the first absorbate stream with steam to produce a vaporous EO stream; 
     e) feeding the vaporous EO stream to an EO reabsorber and contacting the vaporous EO stream with the second portion of the first absorbate stream to form a reabsorber bottoms stream, wherein the reabsorber bottoms stream has a second EO concentration in water that is higher than the first EO concentration in water; 
     f) dividing the reabsorber bottoms stream into a first portion of the reabsorber bottoms stream and a second portion of the reabsorber bottoms stream; 
     g) feeding the first portion of the reabsorber bottoms stream to a first lights stripper and contacting the first portion of the reabsorber bottoms stream with steam to produce a first lights stripper bottoms, wherein the first light stripper bottoms has a third EO concentration in water that is higher than the first EO concentration in water; 
     h) feeding the first lights stripper bottoms to a high purity ethylene oxide distillation column to produce purified EO; 
     i) combining the second portion of the reabsorber bottoms stream and the third portion of the first absorbate stream to produce a second lights stripper feed; 
     j) feeding the second lights stripper feed to a second lights stripper and contacting the second lights stripper feed with steam to produce a second lights stripper bottom stream, wherein the second lights bottom stream has a fourth EO concentration in water that is lower than the third EO concentration in water; and 
     k) feeding the second lights bottom stream to a glycol reactor to produce MEG. 
     Aspect 2: The process according to Aspect 1, wherein the first portion of the first absorbate stream is 30 wt. % to 80 wt. % of the first absorbate stream, the second portion of the first absorbate stream is 15 wt. % to 50 wt. % of the first absorbate stream, and the third portion of the first absorbate stream is 5 wt. % to 40 wt. % of the first absorbate stream. 
     Aspect 3: The process according to any of Aspects 1 and 2, wherein the first portion of the first absorbate stream is 40 wt. % to 60 wt. % of the first absorbate stream, the second portion of the first absorbate stream is 25 wt. % to 35 wt. % of the first absorbate stream, and the third portion of the first absorbate stream is 10 wt. % to 25 wt. % of the first absorbate stream. 
     Aspect 4: The process according to any of Aspects 1-3, wherein the high purity ethylene oxide distillation column further produces a purge stream comprising ethylene oxide and acetaldehyde and wherein the purge stream comprising ethylene oxide and acetaldehyde is fed to the second lights stripper. 
     Aspect 5: The process according to any of Aspects 1-4, wherein the high purity ethylene oxide distillation column produces a vaporous overhead stream comprising EO and formaldehyde and the vaporous overhead stream comprising EO and formaldehyde is fed to the EO reabsorber with the vaporous EO stream. 
     Aspect 6: The process according to any of Aspects 1-5, wherein the first lights stripper produces a vaporous overhead stream that comprises CO 2  and the vaporous overhead stream that comprises CO 2  is fed to the EO reabsorber with the vaporous EO stream. 
     Aspect 7: The process according to any of Aspects 1-6, wherein an evaporation train after the glycol reactor provides steam to at least one of the EO stripper, the first lights stripper, the second lights stripper, and the high purity ethylene oxide distillation column. 
     Aspect 8: The process according to any of Aspects 1-7, wherein the water that is contacted with the quenched and alkaline treated and water washed vaporous reaction stream in the EO absorber comprises recycled process water. 
     Aspect 9: The process according to any of Aspects 1-8, wherein the high purity ethylene oxide distillation column further produces a purge stream comprising the acetaldehyde and EO, and wherein step i) further comprises combining the purge stream comprising the acetaldehyde and EO with the second lights stripper feed. 
     Aspect 10: An apparatus for producing purified ethylene oxide (EO) and monoethylene glycol (MEG) from a quenched and alkaline treated and water washed vaporous reaction stream, wherein the quenched and alkaline treated and water washed vaporous reaction stream comprises EO, CO2, formaldehyde, and acetaldehyde, the apparatus comprising: 
     a) an EO absorber configured and arranged to contact the quenched and alkaline treated and water washed vaporous reaction stream with water to produce a first absorbate stream having a first EO concentration in water; 
     b) a first series of conduits configured and arranged to divide the first absorbate stream into a first portion of the first absorbate stream, a second portion of the first absorbate stream, and a third portion of the first absorbate stream; 
     c) an EO stripper configured and arranged to contact the first portion of the first absorbate stream with steam to produce a vaporous EO stream; 
     d) an EO reabsorber configured and arranged to contact the vaporous EO stream with the second portion of the first absorbate stream to form a reabsorber bottoms stream, wherein the reabsorber bottoms stream has a second EO concentration in water that is higher than the first EO concentration in water; 
     e) a second series of conduits configured and arranged to divide the reabsorber bottoms stream into a first portion of the reabsorber bottoms stream and a second portion of the reabsorber bottoms stream; 
     f) a first lights stripper configured and arranged to contact the first portion of the reabsorber bottoms stream with steam to produce a first lights stripper bottoms, wherein the first light stripper bottoms has a third EO concentration in water that is higher than the first EO concentration in water; 
     g) a high purity ethylene oxide distillation column configured and arranged to produce purified EO from the first lights stripper bottoms; 
     h) a series of conduits configured and arranged to combine the second portion of the reabsorber bottoms stream and the third portion of the first absorbate stream to produce a second lights stripper feed; 
     i) a second lights stripper configured and arranged to contact the second lights stripper feed with steam to produce a second lights stripper bottom stream, wherein the second lights bottom stream has a fourth EO concentration in water that is lower than the third EO concentration in water; and 
     j) a glycol reactor configured and arranged to produce MEG from the second lights bottom stream. 
     Aspect 11: The apparatus according to Aspect 10, further comprising an evaporation train after the glycol reactor, wherein the evaporation train is configured and arranged to provide steam to at least one of the EO stripper, the first lights stripper, the second lights stripper, and the high purity ethylene oxide distillation column. 
     Aspect 12: The apparatus according to any of Aspects 10 and 11, wherein the high purity ethylene oxide distillation column is further configured and arranged to produce a purge stream comprising the acetaldehyde and EO, and wherein h) is further configured and arranged to combine the purge stream comprising the acetaldehyde and EO with the second lights stripper feed. 
     Example: (Prophetic) 
     An EO plant has an EO reactor with a capacity to produce 260,000 metric tons per year (T/yr.) of EO, equivalent to 31.25 metric tons per hour (T/hr.) as feed to both a monoethylene glycol (MEG) plant that can process 100% of the EO and to an EO purification system with a capacity of 150,000 metric tons per year (T/yr.) of high purity ethylene oxide (HPEO). The EO purification section includes an EO stripper bypass stream (as shown in  FIG.  2   ) and the EO stripper/reabsorber system is designed to produce 10 wt. EO in water feed to the high purity ethylene oxide (HPEO) column and to the MEG reactor, which permits 25% of the EO absorbate to bypass the EO stripper and reduces the stripping steam flow to the EO Stripper by 25% or about 11 tons per hour (T/hr.). 
     During normal operation with 10 wt. % EO in water, the EO feed to the MEG reactor is only 42% of the design capacity of the MEG reactor system (the combination of the MEG reactor and the evaporation train after the reactor). Therefore the amount of process steam that can be provided to the EO recovery and purification sections from the evaporation train of the MEG reactor system is much lower than the amount of steam required by the EO recovery section alone. Accordingly, the optimum EO concentration in the feed to the MEG reactor will normally be much lower than 10 wt. % in water so as to increase the amount of stripping steam that can be extracted from the evaporation train of the MEG reactor system and to reduce the undesirable formation of diethylene glycol (DEG) and triethylene glycol (TEG) and raise the yield of the desired MEG. As shown in  FIG.  2   , the water that would be normally be used to dilute the EO feed to the MEG reactor would be recycled EO-free process water (mainly process condensate from the evaporator section of the glycol reactor system) and as a result, the final EO concentration of the MEG reactor feed cannot affect the amount of absorbate that bypasses the EO Stripper. 
     As shown in  FIG.  3   , by installing a second lights stripper that would be used to degasify only the final diluted EO feed to the MEG reactor, all the diluent water required for the MEG reactor feed can be provided from additional absorbate that will bypass both the EO stripper and the EO reabsorber. Detailed simulations of the EO plant show that by diluting the EO feed to the MEG reactor to the maximum water concentration that the evaporation section can handle, the EO concentration would be about 6.4 wt. % (equivalent to a water to {EO+MEG} molar ratio of 33:1). To provide the required diluent water, an additional 14% of the EO absorbate would bypass the EO stripper and the EO reabsorber, resulting in a total of 40% of the absorbate bypassing the EO stripper. This additional bypass provides a total reduction in stripping steam usage of 17 T/hr. (i.e., an additional 6 T/hr. of steam can be saved due to the enhanced EO bypass). 
     In both the standard and enhanced EO bypass cases, the justification for increasing the water to {EO+MEG} molar ratio from about 22:1 (with 10 wt. % EO) to about 33:1 would be an increase in the MEG yield to about 92.5 wt. % (from about 90 wt. %) as shown in  FIG.  4   . The higher water concentration would result in an increase in the high pressure and medium pressure steam usage in the MEG reaction preheat and evaporation trains that largely would be offset by the increased low pressure process steam that would be extracted from the evaporation train and used in the EO plant in both cases.