WO2001038787A1

WO2001038787A1 - Improved chlorinated hydrocarbon waste incinerator an d valorization of chlorinated residuals process unit

Info

Publication number: WO2001038787A1
Application number: PCT/US1999/027715
Authority: WO
Inventors: Tommy G. Taylor
Original assignee: Taylor Tommy G
Priority date: 1999-11-22
Filing date: 1999-11-22
Publication date: 2001-05-31
Also published as: AU1743000A

Abstract

Improvement to the typical Valorizatzion of Chlorinated Residuals (VCR) process unit and the typical chlorinated hydrocarbon incineration unit by replacing ordinary air fed into these units with a synthesized blend of CO2 and O2, including modifications to the units preventing air from entering the units and allowing only the injection of the CO2/O2 blend. By replacing ordinary nitrogen-rich air with a controlled gas mixture of CO2/O2, a useful by-product gas of nearly pure CO2 is generated, which may be recycled back into either unit or used in any number of useful applications. Modifications to the HCl purification units render the water purged from said units result in no more than 3 % by weight hydrogen chloride. The addition of absorbent beds to the vent systems of both units remove unwanted contaminants such as dioxin from the CO2 product with those contaminants being recycled back into the reactors for destruction.

Description

Improved Chlorinated Hydrocarbon

Waste Incinerator and Valorization of

Chlorinated Residuals Process Unit Technical Field

The present invention relates to an improved method for treating chlorinated hydrocarbons in the valorization of chlorinated residuals (VCR) process unit (see, e . g. , U.K. Pat.

No. GB 2053452) and the chlorinated hydrocarbon waste inciner- ator, and more particularly to a method for modifying these systems such that a synthesized blend of carbon dioxide and oxygen replaces the ordinary air used to fuel the reaction in either system, thereby generating a useful hydrogen chloride product and a useful carbon dioxide product in both the VCR process unit and the chlorinated hydrocarbon waste incinerator. The invention further encompasses modifications to the anhydrous hydrogen chloride purification unit attached to these systems that prevent the discharge of any hydrochloric acid streams containing 3% by weight or greater hydrogen chloride dissolved in water. Furthermore, the invention encompasses the addition of absorbent beds to these systems that remove contaminants from the carbon dioxide product, with these contaminants ultimately being recycled back into the high temperature reactors, where they are converted to hydro- gen chloride and carbon dioxide. Also, the invention encompasses the addition of a unit whereby oxygen that is present in the carbon dioxide exiting the absorbent beds is separated from the final carbon dioxide product stream and then recycled back into the high temperature reactor. Background Art

Chlorinated hydrocarbon by-product materials are generated in a wide variety of chlorinated hydrocarbon manufacturing operations, such as the manufacture of ethylene dichloride, vinyl chloride monomer, methyl chloroform, tri- chloroethylene, perchloroethylene, allyl chloride or mono and dichlorobenzene . These are all commercial products, some of which may be used as solvents, others as feedstocks for producing materials such as non-ozone depleting refrigerants, plastic film ( e . g. Saran Wrap^®) , polyvinyl chloride, Teflon^®, or Kynar^® . The chlorinated hydrocarbon by-products of these manufacturing operations have been traditionally considered hazardous wastes requiring carefully regulated treatment. One common method for treating these hazardous by-products is to destroy them in a chlorinated hydrocarbon waste incinerator. In such systems, the liquid wastes are injected into a natural-gas fired incinerator, where the chlorinated organic molecules are essentially oxidized, thus yielding hydrogen chloride (HCI) , salt water and a vent gas comprised mostly of nitrogen and carbon dioxide. An example of this type of system is depicted in Fig. 1.

Steam, or perhaps water, that is sometimes used to cool the reaction in these incinerators mixes with the hydrogen chloride, thus yielding a weaker hydrochloric acid by-product solution. This hydrochloric acid by-product, from 4% to 20% percent by weight hydrogen chloride, is too weak for typical commercial uses, which generally require acid strengths in excess of 31% by weight hydrogen chloride. Therefore, the useless hydrochloric acid by-product must be neutralized and disposed of as salt-water waste. Under federal guidelines, any unit producing an acid stream greater than 3% by weight hydrogen chloride must be classed as a halogen acid furnace (HAF) under the General Hazardous Waste Rules. This weak acid stream is therefore considered an undesirable waste product.

Furthermore, the predominately nitrogen/carbon dioxide waste gas generated in these incinerators is simply vented into the atmosphere. Some of the components present in the incinerator may also be converted into extremely toxic dioxin and into nitrous oxide, which may then appear in the vent gases. The fact that all by-products of the typical chlorinated hydrocarbon incineration unit are un-useful, undesirable waste materials represents a disadvantage to this system.

The valorization of chlorinated residuals (VCR) process unit, similar to the incinerator described above, was designed specifically to produce at least one useful by-product of the typical chlorinated hydrocarbon oxidation technique that takes place in an incinerator, namely anhydrous hydrogen chloride, although, of course the principles of the invention are applicable to other types of processes as well, including new facilities which are designed from the beginning to use the principles of the present invention. However, for exemplary purposes, the invention will be primarily discussed with respect to the particular BCP VCR facility described more fully below.

The VCR process unit, as employed by Borden Chemicals and Plastics (BCP) at Geismar, LA (USA) , converts the chlorinated hydrocarbon by-product left over from the manufacture of vinyl chloride monomer into useful hydrogen chloride. One method for producing vinyl chloride monomer (VCM) entails reacting acetylene and anhydrous hydrogen chloride (HCI) as the raw materials for manufacturing the VCM product (see Fig. 2) .

This process, as practiced by BCP, is termed the VCM-A Process. Another method for producing VCM entails reacting chlorine or anhydrous HCI and ethylene to produce ethylene dichloride or 1,2 dichloroethane (EDC) . The EDC is then thermally reacted to produce VCM (see Fig. 3) . This process, as practiced by BCP, is termed the VCM-E Process. In both VCM processes, the chlorinated hydrocarbon by-product, also called organic intermediate materials, is generated. These organic intermediate materials consist primarily of the following chemical components: ethylene dichloride (CH₂C1CH₂C1) , trichloroethane (CHC1₂CH₂C1) , 1,1,2,2 tetrachloroethane (CHCl₂CHCl₂) , 1,1,1,2 tetrachloroethane (CHCl₃CH₂Cl) , and pentachloroethane (CHCl₂CCl₃) Compounds such as chloroprene, 1,1 dichloroethane, 1,1,1 trichloroethane, chloroform, carbon tetrachloride, cis/trans- dichloroethylene, trichloroethylene, perchloroethylene and various other chlorinated organic compounds are also possible intermediate materials. These organic intermediate materials are further used as feedstock in the VCR process unit, whereby anhydrous HCI is manufactured for use as a raw material feedstock for the VCM-A process described above. The VCR process unit therefore serves as an HCI manufacturing unit using as feedstock the organic intermediate materials produced in the VCM-A and VCM-E processes, the intention being to maintain a "closed-loop" manufacturing process whereby all intermediate materials are usefully and beneficially utilized. Thus, the VCR process unit is designed specifically to use the organic intermediate by-product of both VCM processes as a feedstock for manufacturing HCI, a necessary raw material in the VCM-A and VCM-E processes. The reaction taking place in the VCR process unit is depicted in Fig. 4. The system itself is depicted in Fig. 5.

The VCR process unit uses two raw materials for manufacturing HCI, namely the organic feedstock and air. These raw materials are mixed in the VCR reactor, which contains a proprietary mixing device in which HCI is initially manufactured. In this mixing device, vaporized liquid feedstock is introduced into a high velocity, high temperature air stream. The feedstock and the air react to form anhydrous HCI . The type of reactions that occur in the VCR process are repre- sented by the following equation:

CH₂C1CH₂C1 + CHC1₂CH₂C1 + 4.50₂ + N₂ -- 5HC1 + 4C0₂ + H₂0 + N₂ From the VCR reactor, the anhydrous HCI is directed into a purification unit and then used as feedstock in the VCM-A process. Excess water generated in the reactor must be purged from the system via this HCI purification unit. Since this purge water contains greater than 3% by weight hydrogen chloride, thus constituting a weak acid stream, the VCR process unit is also classed as a halogen acid furnace. This weak acid purge must be neutralized to form salt water, which may then be sewered.

Meanwhile, a gaseous by-product, comprised mainly of C0₂, N₂, and minimal amounts of 0₂, HCI and Cl₂, is directed into an alkaline-fed scrubbing unit, where any HCI and chlorine molecules are converted into salt water and then disposed of . Remaining gases, comprised mainly of C0₂, N₂ and minimal amounts of 0₂, are vented to the atmosphere. The VCR process unit attempts to achieve "closed system" status for the VCM manufacturing process by converting the chlorinated organic material into reusable HCI. The remaining by-products, such as the salt water created from the neutral - ization of the weak acid purge from the HCI purification unit or from the alkaline-fed scrubbing unit, or the gaseous vent emissions comprised of C0₂, N₂, 0₂ have been historically considered environmentally harmless and thus suitable for release into the environment. However, recent concern about global warming and the need to reduce emissions of C0₂, a greenhouse-effect gas, has prompted the U.S. EPA to look with scrutiny on chemical processes that needlessly vent C0₂ to the atmosphere .

Furthermore, the weak acid purge from the HCI neutraliza- tion unit is an undesirable waste product, as is the possible presence of dioxins inadvertently generated in the reactor that may appear in the vent gases.

A need exists, therefore, to modify the existing VCR process and the typical chlorinated hydrocarbon waste inciner- ator such that no C0₂ is emitted to the atmosphere in the vent gas emissions from either system. The U.S. EPA, in carrying out the intentions and objectives of the Resource Conservation and Recovery Act (RCRA) , has incorporated into the RCRA regulations certain rules and procedures to encourage chemical manufacturers to exploit as feedstocks for producing useful chemical products those intermediate materials that otherwise would be classified as hazardous waste materials. The EPA's ultimate goal is to achieve near 100% conversion of such intermediate materials into useful chemical products. This goal can be achieved by modifying existing chlorinated hydrocarbon waste incinerators and VCR process units such that no C0₂ is emitted to the atmosphere because of the unnecessary introduction of N₂ into the incinerator or the VCR. With no N₂ being introduced into either system, the vent from both sys- terns becomes reasonably pure, marketable C0₂, thus enabling essentially 100% beneficial utilization of the chlorinated organic intermediates . A need also exists to modify the anhydrous HCI purification unit attached to the VCR process unit such that the weak acid stream purged from the system contains 3% or less by weight hydrogen chloride. These modifications to the HCI purification unit are also applicable to those HCI purification units (herein termed "primary scrubbers") associated with chlorinated hydrocarbon waste incinerators.

A need further exists to modify the final gas vents in the VCR process unit and the chlorinated hydrocarbon waste incinerator such that undesirable compounds such as dioxins that might be present in the vent gases are captured before release to the atmosphere and destroyed within the system. General Discussion of Invention

The present invention is designed in one of its major aspects specifically to eliminate the N₂ component of the final emission from, for example, the chlorinated hydrocarbon waste incinerator shown in Fig. 1 and, for further example, from the

VCR process unit shown in Figs. 4 & 5. The present invention is also designed to eliminate, for example, an acid purge greater than 3% by weight hydrogen chloride from the anhydrous

HCI purification units attached to both systems. Furthermore, the present invention is designed inter alia to eliminate, for still further example, any trace contaminants, such as dioxin, from the vent gases of either system. It is noted that oxygen (0₂) is the only component of air that is needed to react with the chlorinated organic materials in both systems in order either to destroy the molecules in the incinerator, or to manufacture anhydrous HCI in the VCR process unit. Nitrogen (N₂) , an inert gas comprising roughly 78% of air, acts as a necessary diluent and coolant in the mixture that is fed into the incinerator and the VCR reactor. The 0₂ component of the reaction taking place in either system preferably must not greatly exceed the normal 21% volume found in air, lest the reaction go unchecked and temperatures within the incinerator or the VCR reactor exceed specifications. After the reaction, the N₂ component, in the preferred embodiment, simply passes through the system, released in the final emissions stage as an inert, useless vent component, mixed predominately with carbon dioxide (C0₂) , another inert gas. Since C0₂ is an identified greenhouse-effect gas, and since the separation and purification of N₂ and C0₂ in this vent stream would be a very expensive and an inefficient operation, the N₂/C0₂ vent stream is undesirable.

However, the inventor has surmised that a synthesized mixture of roughly 21% by volume 0₂ and 79% by volume C0₂ could be used in place of air in both the chlorinated hydro- carbon waste incinerator and the VCR reactor, thereby eliminating the undesirable N₂ from the vent stream. This synthesized gas mixture could contain as much as 90% by volume C0₂ and 10% by volume 0₂, or as little as 25% by volume C0₂ and 75% by volume 0₂. However, the optimum mixture would likely contain from about 60% to about 80% by volume C0₂, with 40% to 20% by volume 0₂ comprising the remaining percentage.

C0₂, an inert gas, could essentially replace the diluent N₂ in the feed air, thus providing the same diluent and non- reacting properties of the N₂. The 0₂ in this mixture, essen- tially the same amount by volume as found in air, would effectively carry out the reaction with the chlorinated organic intermediates necessary to break down these chlorinated molecules, as in the incinerator, or to produce anhydrous HCI, as in the VCR reactor. The by-products of the reaction would therefore be comprised essentially of C0₂ and a small amount of

0₂. Trace amounts of Cl₂ and HCI in these emissions would still be eliminated in the alkaline scrubbing unit attached to either system, thereby producing a harmless salt water byproduct. Other unwanted trace compounds, such as dioxin, can be eliminated from the vent gases through modifications that are described below. The remaining vent gas emission would therefore be predominately C0₂ and a small amount of 0₂. In this way, no undesirable N₂ would enter or leave the incinerator or the VCR process unit. The reaction employing a C0₂/0₂ mixture in place of air in the VCR process unit is shown in Fig. 6. The modified system using only the C0₂/0₂ mixture is depicted in Fig. 7. The modified waste incinerator is depicted in Fig. 8.

A further advantage exists in using C0₂ as a diluent in the gaseous raw material fed into the VCR process unit and into the chlorinated hydrocarbon waste incinerator. Since C0₂ is a necessary inert component to this raw material, the C0₂ that comprises the final emission from either system could then be reclaimed and reused to mix with 0₂ as the diluent in the gaseous raw material. In this way, the VCR process unit genuinely becomes a "closed-system, " wherein all end-products of the VCM and VCR processes are reused in the system.

No undesirable gases would therefore be released into the atmosphere. Excess C0₂ generated as a result of the VCR process or the chlorinated hydrocarbon waste incinerator could further be used in any number of useful applications.

The modified chlorinated hydrocarbon waste incinerator, using only the synthesized C0₂/0₂ mixture, becomes a much improved, much more useful waste treatment system, since no undesirable greenhouse-effect exit gases are vented from the system, nor may undesirable by-products, such as nitrous oxide and dioxin be created and vented to the atmosphere. Instead, as in the VCR process unit, the C0₂/0₂ vent gas mixture may be reclaimed and recycled back into the incinerator, or the C0₂ may be used in other processes. Since this C0₂/0₂ mixture could also be used in place of water to cool the reaction in the incinerator, the hydrogen chloride by-product generated in the incinerator would be less diluted, and thus more economically processable to anhydrous hydrogen chloride or strong commercial hydrochloric acid. The VCR process unit contains an HCI purification unit, an example of which is depicted in Figs. 4 & 5. The purpose of this unit is to separate the C0₂, N₂ and 0₂ from the HCI and also to separate the HCI from the water, thus producing useful anhydrous hydrogen chloride product. However, the present VCR art practiced for example by BCP does not process all of the HCI produced in the VCR reactor into high purity anhydrous HCI. A small amount of weak hydrochloric acid, 18% to 20% by weight hydrogen chloride, is produced and removed from the system to serve as the outlet for the water that is produced in the VCR reactor (see Fig. 9) , and which must be purged from the system. Because of the production of this weak acid purge stream, BCP ' s VCR operation has been further classified by the EPA as a halogen acid furnace (HAF) under the General Hazardous Waste Rules.

Fig. 10 represents a proposed modification to the VCR HCI purification scheme that eliminates the production of the halogen acid stream, thus achieving nearly 100% production of high purity anhydrous HCI gas from the HCI that is manufactured in the VCR reactor. Without the production of a halogen acid stream containing 3% or more of HCI, the VCR unit does not meet the specified criteria for a halogen acid furnace. The modification to the VCR HCI purification system requires the addition of a distillation column to be used for the purpose of stripping water from a hydrochloric acid solution containing from 14.5% to 19% by weight HCI. Such a stream can be produced by operating the HCI stripper at an elevated pressure. An operating pressure of 110 PSIG will permit the production of an underflow stream from the HCI stripper containing as little as 14.5% by weight HCI. Operating the HCI stripper at such a pressure as will produce 18% by weight HCI underflow stream is suggested. The inventor further suggests operating the water stripping column at pressures ranging from zero to near full vacuum. At a pressure of zero PSIG, the underflow from the water stripping column should be approximately 20.2% by weight HCI dissolved in water. The overhead from the water stripping column could be controlled to produce a water stream containing very little HCI, definitely less than 3% by weight HCI.

The amount of water discharged from the top of the water stripping column will be determined by the amount of water produced in the VCR reactor. It is the opinion of the inven- tor that feeding into the water stripping column a stream containing 18% HCI and withdrawing an underflow stream from that column containing 20% HCI will normally permit the removal of the needed amount of water from the system. If more water removal is required, the operating pressure of the HCI column can be increased, thus lowering the HCI content of the underflow from that column. Another option would be to recycle a portion of the underflow from the water stripping column back into the HCI stripping column as a mid-column feed stream.

The technique described herein for removing water from a VCR process unit is applicable to situations where conven- tional chlorinated hydrocarbon waste incinerators are employed to manufacture high purity anhydrous HCI from chlorinated hydrocarbon waste materials.

Even when feeding a synthesized mixture of C0₂ and 0₂, instead of air, into VCR units or into conventional hazardous waste incinerators, there is still the possibility that minute amounts of undesirable compounds generated in the reactor, such as dioxin, will appear in the C0₂ product stream. The inventor further proposes that absorbent beds capable of absorbing such components as dioxins be incorporated into the vent systems of the VCR process unit and the conventional chlorinated hydrocarbon waste incinerator systems to remove any trace quantities of such components that might be present in the C0₂ product stream.

After leaving the HCI purification unit, this C0₂ product stream preferably would be blown through a bed of absorbent material, such as activated carbon for example, or any number of suitable materials that readily absorb compounds such as dioxin. Said contaminants in the gas would be trapped within this absorbent material. Furthermore, the bottom portion of each absorbent bed can include some desiccant material capable of removing small amounts of water that otherwise would be present in the C0₂ stream exiting the bed. Clean, dry C0₂ containing some amount of 0₂ would exit the downstream end of the bed. In time, the absorbent materials would become satu- rated with said contaminants and would thus require reactivation, which could be accomplished by pumping a hot reactivation gas through the bed to release the contaminants. Since C0₂ in this invention preferably is being recycled to produce a synthesized C0₂/0₂ stream for feeding into VCR reactors or into hazardous waste incinerators, the inventor proposes reactivating the absorbent bed with some of the C0₂ product that has been super-heated by steam. This reactivation gas would then be passed through the spent bed to strip out dioxin or other such contaminants, and then the gas would be routed back into the high temperature incinerator or VCR reactor where said contaminants would be oxidized, and essen- tially destroyed. In this way no contaminants would ever leave the VCR process unit or the chlorinated hydrocarbon waste incinerator.

Fig. 11 depicts two absorbent beds installed in parallel that can be used to clean the C0₂ product, while at the same time preventing in total the escape to the environment of any toxic compounds such as dioxins that might be present in gases exiting a VCR reactor or a hazardous waste incinerator. The optimal design of such a system would employ at least two absorbent beds in parallel so that one bed could be cleaning the C0₂ product while the other bed is in reactivation service. Additionally, it is anticipated that these two modified systems for processing chlorinated hydrocarbons can be located near or adjacent to facilities utilizing C0₂ as feedstock, such as plants manufacturing urea, a vital component in fertilizer, or plants that manufacture methanol, or plants for producing silicon dioxide pigment, or other such CO, consuming operations .

Excess C0₂ generated in either system might also be purified and used for such things as inert purging and padding gas for systems handling, for example, flammable materials and for producing carbonated beverages. Thus, finally, as an optional, supplemental process, a sub-system for separating out undesired 0₂ from the product C0₂ stream for optional use in conjunction with the HCI purification system of the inven- tion is provided.

A further aspect of the present invention includes using a unit whereby the C0₂, which contains some amount of 0₂, exiting the absorbent beds is compressed to a relatively high pressure and then passed through, for example, the tubes of a shell-and-tube, heat exchanger, which has on the shell side of the exchanger liquid C0₂ boiling at a lower pressure. The cold boiling C0₂ on the shell side of the heat exchanger condenses the high pressure C0₂ passing through the tubes, thus producing a stream containing liquid C0₂, 0₂ in solution with the liquid C0₂, and free 0₂ gas. This stream is fed into a column where, for example, hot compressor discharge gas is used to apply heat to the liquid C0₂ at the bottom of the column, thus driving the dissolved 0₂ up and out the top of the column. The 0₂ rich stream exiting the top of the oxygen stripping column can be recycled back into the high temperature reactor, e . g. the incinerator. The vaporized oxygen free C0₂ stream, as it exits the shell side of the heat exchanger is heated with, for example, hot compressor discharge gas, thus producing heated, high quality pipeline C0₂ product. Since this C0₂ product stream contains essentially no 0₂, it can be used, for example, as a reactivation gas for absorbent beds utilizing activated carbon as the absorbent material. Reactivating an absorbent bed containing dioxins will likely require a reactivation temperature higher than that which can be achieved using steam as the source of heat . Heating C0₂ reactivation gas in a furnace fired with the natural gas possibly would enable the achievement of a temperature sufficient for reactivating absorbent beds containing dioxin.

Another approach for accomplishing reactivation would be to use carbon as the absorbent material, enrich the C0₂ reactivation gases with 0₂ and then heat this gaseous mixture with steam in, for example, a shell and bulb heat exchanger prior to feeding it into the bed being reactivated. Raising the termperature of 0₂ enriched C0₂ to 250° F would ignite the carbon within the bed which would vaporize the dioxin and drive it out of the bed along with the very hot C0₂ exit gas that is routed back into the combustion chamber of the incinerator. This approach would consume some carbon during each reactivation, thus requiring the addition of make-up absorbent carbon after, for example, each reactivation.

Also included in this invention is a simplified, integrated process and system for converting chlorinated hydrocar- bon by-products into useful anhydrous HCI gaseous products and useful C0₂ gaseous product with zero discharge of anything to the environment, in a process that completely meets the objectives of the Resource Conservation and Recovery Act (RCRA) or its equivalent. This can be done using a method and system for modifying conventional hazardous waste, incinerator units or VCR units for producing high purity HCI gas and high purity C0₂ gas with zero discharge of any materials to the environment. The present invention also includes a method and system for building and operating new { vis -a -vis modifying conven- tional) incinerator units and new VCR units that will produce from chlorinated by-products high purity HCI and high purity C0₂ with zero discharge of any material to the environment .

It is further noted, with respect to some of the foregoing, that the present invention includes inter alia : 1. Modifications that can be made to the VCR process, which is now a process used for the purpose of destructing chlorinated hydrocarbon materials that have been classified by the EPA as hazardous waste materials, such that these materials would no longer be classified as hazardous waste materials because: a) The materials would be used in total to produce feedstocks that would be further used to produce other marketable products. The production of water and a very miner amounts of salt is acceptable. The key is to convert essen- tially all the carbon, chloride and hydrogen contained in the chlorinated hydrocarbon by-products into useful HCl and useful C0₂. b) No stream would be produced that contained more than 3% by weight HCI in water. If a stream is produced having3% or more by weight of HCI in water, the process as defined in the RCRA regulations is classified as halogen acid furnace and all materials so processed is subject to a hazard- ous waste tax. With no acid produced containing greater than 3% percent HCI in water, the modified VCR process unit can not be classified as a halogen acid furnace. c) There would be no vents to the atmosphere. With the absorbent beds removing water and any possible contaminants from the C0₂ product and those contaminants ultimately being recycled back into the VCR reactor, there is zero discharge to the environment of such things as dioxin. The outstanding thing about the process is that what is now con- sidered very hazardous chlorinated hydrocarbon waste would be processed in a manner such that the environmental impact would be zero.

2. Modifications that can be made to conventional hazardous waste incinerators used for the destruction of materials classified by the EPA as very hazardous chlorinated hydrocarbon waste materials such that those materials would no longer be classified as such, because: a) The materials would be used in total to produce feedstocks that would be further used to produce other market - able products. The production of water and a very miner amounts of salt is acceptable. The key is to convert essentially all the carbon, chloride and hydrogen contained in the chlorinated hydrocarbon by-products into useful HCI and useful C0₂. b) No stream would be produced that contained more than 3% by weight HCI in water. If a stream is produced having 3% or more by weight of HCI in water, the process as defined in the RCRA regulations is classified as halogen acid furnace and all materials so processed is subject to a hazard- ous waste tax. With no acid produced containing greater than

3% percent HCI in water, the modified VCR process unit can not be classified as a halogen acid furnace. c) There would be no vents to the atmosphere. With the absorbent beds removing water and any possible contami- nants from the C0₂ product and those contaminants ultimately being recycled back into the VCR reactor, there is zero discharge to the environment of such things as dioxin. The outstanding thing about the process is that what is now considered very hazardous chlorinated hydrocarbon waste would be processed in a manner such that the environmental impact would be zero. Any conventional hazardous waste incinerator modified in accordance with the principles of the present invention should become units highly suitable for processing materials containing such things as PCBs (polychlorinated bi-phenyls) . Also, hazardous waste incinerators incorporating some of the modifi- cations contained in this invention should be entirely suitable for destructing chemicals manufactured for chemical warfare. Things such as N-mustard compounds and S-mustard compounds could be totally and safely destroyed by employing the absorbent bed technique that is incorporated herewith into the list of suggested modifications for conventional hazardous waste incinerators. Right now, there is a desperate need for a reliable and satisfactory method that the United States Department of Defense can use to destruct a huge quantity of unneeded and unwanted N-mustard and S-mustard. Additionally, as will become clear from the following detailed description, other highly innovative, unobvious advances and improvements are also disclosed as part of the present invention.

Brief Description of Drawings

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accom- panying drawings, in which like elements are given the same or analogous reference numbers, and wherein:

Fig. 1 is a schematic, generalized view of a typical, prior art chlorinated hydrocarbon waste incinerator system. Fig. 2 is a schematic, flow chart view of the exemplary reaction taking place in an exemplary, prior art, vinyl chloride monomer-acetylene (VCM-A) manufacturing unit.

Fig. 3 is a schematic, flow chart view of the exemplary reaction taking place in an exemplary, prior art, vinyl chloride monomer-ethylene (VCM-E) system. Fig. 4 is a schematic, flow chart view of the exemplary reactions taking place in a typical, prior art, air-fed valorization of chlorinated residuals (VCR) process unit.

Fig. 5 is a schematic, generalized flow chart view of the exemplary feed mechanisms for an exemplary, prior art, air- fed valorization of the chlorinated residuals (VCR) process unit.

Fig. 6 is a schematic, generalized flow chart view of the exemplary reactions taking place in a VCR process unit modified for a synthesized C0₂/0₂ feed in accordance with the principles of the present invention. Fig. 7 is a schematic, generalized flow chart view of the exemplary feed mechanism for a C0₂/0₂-fed VCR unit, such as that shown in Fig. 6.

Fig. 8 is a schematic, generalized flow chart view of the exemplary chlorinated hydrocarbon waste incineration system modified for a synthesized C0₂/0₂ feed in accordance with principles of the present invention.

Fig. 9 is a simplified flow diagram of an exemplary, prior art HCI purification system as found in the VCR process unit . Fig. 10 is a simplified flow diagram of the exemplary HCI purification system modified in accordance with the principles of the present invention.

Fig. 11 is a schematic of exemplary absorbent beds for removing contaminants from the C0₂ product generated in the VCR process unit or a chlorinated hydrocarbon waste incinerator.

Fig. 12 is a simplified flow diagram and schematic for an exemplary, optional, preferred process and system for separating out undesired0₂ from the product C0₂ stream for optional use in conjunction with the HCI purification system of the invention.

Fig. 13 is a simplified flow diagram and schematic of the exemplary integrated process for producing, from chlorinated hydrocarbon by-products, high purity HCI gaseous product and high purity C0₂ gaseous product with zero discharge of pollutants to the environment, including no discharge of dioxins, green-house gases or N0_X gases.

Description of the Preferred. Exemplary Embodiment Fig. 1: The typical chlorinated hydrocarbon waste incin- erator system is shown. The system is comprised of a central, high-temperature incinerator into which natural gas, chlorinated liquid wastes and process gaseous wastes are injected, along with combustion air. The controlled natural gas flame burns within the incinerator. There is a port adjacent to this flame wherein steam or water can be injected to cool the reaction. A primary scrubber is attached downstream of the incinerator, wherein hydrogen chloride is dissolved in water to produce a weak acid solution. A secondary scrubber containing an alkali solution is attached downstream of the primary scrubber in order to neutralize any HCI or chlorine still contained in the vent gas. The remaining C0₂/N₂ gas is vented from this secondary scrubber.

Fig. 2: The reaction taking place in a vinyl chloride monomer-acetylene (VCM-A) manufacturing unit is depicted. In this unit, acetylene is reacted with anhydrous HCI to produce vinyl chloride monomer. Chlorinated organic intermediates are shown as a by-product of this reaction. They may be used in a valorization of chlorinated residuals (VCR) process unit. The chemical equation showing the reaction of acetylene with HCI is also depicted. Fig. 3: The reaction taking place in a vinyl chloride monomer-ethylene (VCM-E) system is depicted. In one unit, chlorine and ethylene are reacted to produce ethylene dichloride (EDC) in a liquid phase direct chlorination technique. Chlorinated organic intermediates are by products of this reaction and may be fed into a VCR process unit. In another unit, anhydrous HCI is reacted with ethylene and 0₂ to produce EDC in a gas phase oxyhydrochlorination technique. The EDC manufactured in the liquid and gas phase units is fed into the VCM-E manufacturing unit to produce the vinyl chlo- ride monomer product. Chlorinated organic intermediates are generated in each unit, and may be fed into a VCR process unit. The basic chemical equation for the VCM-E process is also shown.

Fig. 4: The reactions taking place in a typical air- fed valorization of chlorinated residuals (VCR) process unit are depicted. In this unit, chlorinated organic intermediates (i.e. chlorinated hydrocarbon by-products of the VCM-A and

VCM-E processes) are fed with air into the VCR unit, where the chlorinated molecules are oxidized, thus yielding anhydrous HCI, trace amounts of Cl₂, carbon dioxide, nitrogen, and small amounts of oxygen and water vapor. This yield is passed into an HCI purification unit, from which purified anhydrous HCI is removed. Some salt water leaves this unit, while remaining vent gases are passed through a neutralization unit. In the neutralization unit, alkaline wash water neutralizes any remaining HCI and chlorine in the vent gas, turning it into waste salt water. The remaining, "clean" carbon dioxide/nitrogen gas mixture is vented from this unit . The basic chemical equation for this process is also shown. Fig. 5: The feed mechanisms for an air- fed valorization of chlorinated residuals (VCR) process unit is depicted. The unit consists primarily of a reactor, into which vaporized chlorinated organics are injected into a mixing device with a controlled feed of high velocity, high temperature air. Natural gas (CH₄) is used only during start-up of the unit. From the mixing device, the high-temperature organic interme- diate/air mixture enters the reactor itself, where oxidation of the chlorinated compounds takes place. Secondary air ports, whence additional diluent air is drawn into the reactor, are also depicted. The anhydrous HCI, C0₂, N₂, 0₂, and water vapor exits the reactor, passing through the HCI purifi- cation unit, and neutralization unit described in Fig. 4.

Fig. 6: The reactions taking place in a VCR process unit modified for a synthesized C0₂/0₂ feed are depicted. In this modified system, a synthesized mixture comprised of approximately 79% C0₂ and 21% 0₂ is mixed with chlorinated organic intermediates and then injected into the VCR reactor. The resulting anhydrous HCI, C0₂, 0₂, and water vapor product is passed into the HCI purification unit, where anhydrous HCI is removed. Some salt water exits this purification unit. The remaining C0₂ gas, containing trace amounts of HCl and chlo- rine, is passed through a neutralization unit, where an alkaline wash is used to neutralize any remaining HCI and chlorine from the C0₂, converting them into salt water. The nearly pure C0₂, is then collected as it exits the neutralization unit, where it may be used as C0₂ product, or mixed with pure 0₂ in a synthesizing unit. The mixture from the synthesizing unit is then fed back into the VCR reactor.

Fig. 7: The feed mechanism for a C0₂/0₂-fed VCR unit is depicted. The unit includes primarily a reactor into which chlorinated organic intermediates are injected, along with a high-velocity, high-temperature controlled feed of C0₂/0₂.

These components are mixed and injected into the reactor unit, where oxidation of the chlorinated compounds takes place. The synthesized C0₂/0₂ mixture is further drawn into secondary ports to act as a diluent to the reaction. Note that no air is either fed into, nor drawn into this modified system. The anhydrous HCI, C0₂, 0₂, and water vapor mixture is passed into the HCI purification unit, where nearly pure anhydrous HCI is re oved. Some salt water exits this unit. C0₂, and small amounts of 0₂, HCI and Cl₂ exit the purification unit and pass through the neutralization unit, where an alkali wash neutralizes any HCI and chlorine molecules, turning them into salt water. Then, the nearly pure C0₂ product is collected from the neutralization unit, where it may be used in other processes, or blended with 0₂ in a high pressure surge drum, whence the synthesized blend may be drawn for the controlled feed. Additional synthesized C0₂/0₂ mixture is drawn from the surge drum and stored just above atmospheric pressure in a tank for feed into the secondary (diluent) C0₂/0₂ ports in the reactor. Fig. 8: The chlorinated hydrocarbon waste incineration system modified for a synthesized C0₂/0₂ feed is depicted. In this system, chlorinated liquid wastes and process gaseous wastes are injected along with the natural gas fuel and the C0₂/0₂ combustion mixture into the incinerator. Chlorinated molecules are broken down (oxidized) in a controlled flame within the incinerator. Recycled C0₂ is injected adjacent to this controlled flame for cooling purposes. Downstream of the incinerator, a primary scrubber removes most hydrogen chloride from the by-product blend exiting the incinerator, yielding an acid solution that may be purified for further use or neutralized for disposal . A secondary scrubber downstream of the primary scrubber removes any remaining chlorine molecules from the vent gas, yielding salt water and a nearly pure C0₂ vent product. This vent product may then be mixed with pure 0₂ in a synthesizing vessel and re-injected into the incinerator.

Fig. 9: The simplified flow diagram of an HCI purification system as found in the VCR process unit is depicted. In this system, a gaseous mixture comprised of mostly HCI, C0₂ and water vapor is passed into the HCI Absorber from the VCR reactor. This absorber removes nearly all of the HCI from the gaseous mixture, which then exits the absorber in solution with water at approximately 33% by weight HCI. C0₂ containing a small amount of 0₂ is vented from this absorber. The 33% by weight HCI acid stream is pumped into an HCI stripper where HCI is separated from the solution, yielding 100% anhydrous HC1 gas. An approximately 9% percent by weight HCl acid solution is withdrawn from the bottom of the HCl stripper with most of the stream being recycled back to the HCl absorber. A small portion of the 19% HCl recycle stream is purged from the system to remove excess water generated in the VCR reactor. This diagram is also applicable to the HCl purification unit attached to a chlorinated hydrocarbon waste incinerator.

Fig. 10: The simplified flow diagram of a modified HCl purification system as found in the VCR process unit is de- picted. In this system, a gaseous mixture comprised of mostly HCl, C0₂ and water vapor is passed into the HCl Absorber from the VCR reactor. This absorber removes nearly all of the HCl from the gaseous mixture, which then exits the absorber in solution with water at approximately 3% by weight HCl. C0₂ containing a small amount of 0₂ is vented from the Absorber. The 33% by weight HCl acid stream is pumped into an HCl stripper maintained under high pressure where HCl is separated from the solution, yielding 100% anhydrous HCl gas. High pressure operation of the HCl Stripper permits the production of an underflow stream containing less than 19% HCl, the normal being approximately 18% by weight HCl. The 18% percent HCl stream is then fed into the water stripping column, which is operated at zero PSIG or vacuum pressure. Essentially pure water is distilled overhead from the water strip- ping column, thus producing an underflow stream of 20% to 21% by weight HCl in water. The entire underflow from the water stripping column is recycled back to the HCl absorber.

Fig. 11: The schematic of absorbent beds for removing contaminants from the C0₂ product generated in a VCR process unit or a chlorinated hydrocarbon waste incinerator is depicted. In this system, C0₂ from the HCl purification unit is directed into an Absorbent Bed No. 1, where contaminants such as dioxin are absorbed from the C0₂. The clean C0_; product is exited from the downstream end of the absorbent bed. The clean C0₂ may then be used for other operations requiring C0₂. An Absorbent Bed No. 2 is installed in parallel with Absorbent Bed No. 1. It is used to clean the C0₂ product in like manner while the first Absorbent Bed is being reactivated (i.e. while trapped contaminants are removed from the bed through the introduction of a hot C0₂ reactivation gas heated in a natural gas fired heater or in the case of a bed charged with carbon absorbent, a hot C0₂ gas stream enriched with 0₂ being heated by high pressure steam) . Note that C0₂ generated within the system is employed as the reactivation gas, thereby keeping all products within the system. A reactivation stream bearing contaminants is routed from the reactivated Absorbent Bed back into the VCR reactor, where contaminants are destroyed. A system of valves within the system of Absorbent Beds directs the proper flow of C0₂ product or reactivation materials. The C0₂ feed stream entering an absorbent bed will contain a low level of water. The bottom portion of each absorbent bed preferably includes a desiccant material for removing water from the C0₂, thus producing a dry, purified C0₂ exit stream. Fig. 12: The simplified flow scheme of a process for separating 0₂ from C0₂ is depicted. The scheme comprises a unit whereby the C0₂, which contains some amount of 0₂ exiting the absorbent beds, is compressed to a relatively high pressure and then passed through, for example, the tubes of a shell -and-tube, heat exchanger which has on the shell side of the exchanger liquid C0₂ boiling at a lower pressure. The relatively low temperature boiling C0₂ on the shell side of the heat exchanger condenses the high pressure C0₂ passing through the tubes thus producing a stream containing liquid C0₂ and 0₂ in solution with the liquid C0₂ and free 0₂ gas. This stream is fed into a column where, for example, hot compressor discharge gas is used to apply heat to the liquid C0₂ at the bottom of the column thus driving the dissolved 0₂ up and out the top of the column. The 0₂ rich stream exiting the top of the oxygen stripping column can be recycled back into the high temperature reactor. The vaporized oxygen free C0₂ stream as it exits the shell side of the heat exchanger is heated with hot compressor discharge gas thus producing heated high quality pipeline C0₂ product. Since this C0₂ product stream contains essentially no 0₂, it possibly can be used as a reactiva- tion gas for absorbent beds utilizing activated carbon as the absorbent material if the C0₂ is heated to, for example, 2,000° F or greater in a natural gas fired heater.

Fig. 13: The simplified, integrated process, flow scheme for producing, from chlorinated hydrocarbon by-product, high purity gaseous HCl product and gaseous C0₂ product is depicted. The process discharges no environmentally harmful materials to the environment and completely meets the objectives of RCRA. The integrated process involves manufacturing a synthetic mixture of C0₂ and 0₂ in vessel V-100. This synthetic mixture of C0₂/0₂ is properly mixed with the chlorinated hydrocarbon by-products and fed into a high temperature reactor (s), for example, an incinerator R-100 or a VCR unit R-101.

Exiting the high temperature reactor R-100/R-lOl is a gas stream consisting of HCl, C0₂, H₂0 vapor and 0₂. After cooling (cooling step not shown) , this stream is fed into the bottom of the HCl absorber V-101 where the HCl is absorbed into weak acid [approximately 20% in strength] which is fed into the top of V-101. Strong acid [approximately 33% ] is pumped from the bottom of absorber V-101 and fed into the top of the high pressure HCl stripper V-102. Steam heat is applied to the bottom of stripper V-102, thus resulting in the overhead stripping of approximately 54-55% of the HCl fed into stripper V-102. Normally, the high pressure HCl gas produced in strip- per V-102 will be used for producing ethylene dichloride in oxyhydrochlorination reactors and for producing vinyl chloride monomer in VCM-A reactors .

The underflow from the stripper V-102, approximately 15% in strength, is fed into the top of the water stripper V-103, where water is distilled overhead by applying steam heat to the bottom of the column. Enough water is distilled overhead in the stripper V-103 to produce an under-flow stream approximately 20% in strength. This 20% percent stream is recycled back into the top of absorber V-101. (Within the HCl absorp- tion and stripping system, heat removal, which is not shown, is required. )

Carbon dioxide exiting absorber V-101 and containing 4-10% 0₂ and trace quantities of HCl and chlorine is fed into the bottom of the Neutralizer V-104, where the gas is scrubbed with an alkaline solution to neutralize the trace quantities of HCl and chlorine . C0₂ with some amount of 0₂ present exits the top of neutralizer V-104 and is fed into compressor C-l, where the pressure is raised to a level sufficient for recy- cling C0₂ into vessel V-100 and for passing the stream through the C0₂ clean-up beds V-105 and V-106.

Un-purified C0₂ containing some 0₂ is fed through clean-up bed V-105 while V-106 is being reactivated or visa -versa .

Clean-up beds V-105 and V-106 are charged with activated carbon or some other material capable of removing trace contaminants, such as dioxin, from the C0₂ stream. The bottom portion of each C0₂ clean-up bed likely will need to be charged with a desiccant material capable of removing the low levels of water that will be present in the gas stream entering the beds. Upon exiting the active clean-up bed V-105/V-106, depending on which clean-up bed is in service, purified dry C0₂ containing some 0₂ is fed into compressor C-2, where the pressure is elevated to, for example, approximately 250 PSIG and then routed through the tube side of the C0₂ condenser/vaporizer E-100. As the high pressure gas passes through the tubes, the C0₂ condenses taking some 0₂ into solution. Condensed C0₂, 0₂ in solution and gaseous 0₂ are passed into the 0₂ stripper V-107. The bottom of V-107 is heated with hot gas exiting compressor C-2, thus driving the 0₂ dissolved in the liquid C0₂ up and out the top of V-107. The 0₂ rich stream exiting the top of stripper V-107 is recycled back into vessel V-100. Oxygen free C0₂ is withdrawn from the bottom of V-107, where it is routed into the shell side of heat exchanger E-101. The shell side of heat exchanger E-101 is maintained at a pressure well below the discharge pressure of compressor C-2, thus permitting C0₂ to vaporize in the shell of condenser/vaporizer E-100 at a temperature low enough to condense the C0₂ flowing through the tubes. As the purified vaporized C0₂ exits the shell of condenser/vaporizer E-100, it is heated with the hot gas discharged from compressor C-2 and then is marketed as high purity C0₂ pipeline product. A portion of the high purity C0₂ product is routed through the heat exchanger E-101, where it is heated to a sufficient temperature to reactivate either clean-up bed V-105 or V-106, which ever bed is being reactivated. As the hot C0₂ passes through the bed being reactivated, dioxin and other such compounds are stripped from the beds and routed back through the high temperature reactor where they are destroyed. Also, the water captured by the water removing desiccant within the bed is stripped from the bed and routed back into the reactor. Fig. 13 thus depicts a method for modifying conventional hazardous waste incinerators units or VCR units for producing high purity HCl gas and high purity C0₂ gas with zero discharge of any harmful materials to the environment. It also depicts a methods for building and operating new incinerator units and new VCR units that will produce from chlorinated by-products high purity HCl and high purity C0₂ with zero discharge of any harmful material to the environment . It is noted that the embodiments described herein in detail for exemplary purposes are of course subject to many different variations in structure, design, application and methodology. Because many varying and different embodiments may be made within the scope of the inventive concept (s) herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims

ClaimsWhat is claimed is:

1. In a system having a high temperature reactor, including chlorinated hydrocarbon waste incinerators having a HCl purification unit associated with the incinerator, VCR reactors having an anhydrous HCl purification unit associated with the VCR reactor, and the like, having a vent stream, a method of eliminating the emission of N₂ and C0₂ into the atmosphere, comprising the steps of feeding a synthesized mixture of a carbon-dioxide/oxygen

(C0₂/0₂) feed into the high temperature reactor, substantially reducing, if not eliminating, the N₂ from the vent stream.

2. The method of Claim 1, wherein the feed mixture of C0₂/0₂ is in the range of about 90% C0₂ to about 25% C0₂, and from about 10% to about 75% 0₂.

3. The method of Claim 1, wherein the high temperature reactor is a VCR reactor, and wherein there is included for the C0₂/0₂ feed mixture the steps of (a) obtaining the C0₂ component from the vent gas of the VCR reactor; and obtaining pure 0₂ from an air separation plant.

4. The method of Claim 1, wherein the high temperature reactor is a VCR reactor having secondary entry ports, and wherein there is further included the step of supplying the required minor excess flow of 0₂ into the secondary entry ports of the VCR reactor for the C0₂/0₂ feed.

5. The method of Claim 1, wherein the high temperature reactor is a VCR reactor having secondary entry ports, and wherein there is included the step of using a holding tank for the C0₂/0₂ gas mixture to supply flow into the secondary entry parts of the VCR reactor.

6. The method of Claim 4, wherein the VCR reactor is part of a pre-existing plant, and wherein there is included the step of modifying the secondary entry ports of the VCR reactor, which theretofore fed organic feed stock, so that only the C0₂/0₂ mixture in the holding tank can enter the secondary entry ports.

7. The method of Claim 1, wherein there is included the step of adding a HCl stripper rated for high pressure operations and a HCl stripper feed pump capable of developing the higher pressure .

8. The method of Claim 7, wherein there is included the step of running the HCl stripper at a pressure as high as about 110 PSIG .

9. The method of Claim 7, wherein there is included the step of constructing the high pressure stripper and its associated re-boiler of materials which will withstand the more corrosive conditions of the high pressure operations.

10. The method of Claim 1, wherein there is included the step of adding a water stripping column.

11. The method of Claim 1, wherein the high temperature reactor is a VCR reactor having a vent system, and wherein there is included the steps of (a) adding absorbent beds to the vent system of the VCR reactor; and (b) using the absor- bent beds to remove contaminants from the vent gas, C0₂ product stream.

12. The method of Claim 11, wherein there is further included the steps of (a) providing a heater, a control system and related piping; and heating the C0₂ used for reactivating the absorbent beds.

13. The method of Claim 12, wherein there is included the steps of modifying the piping and control systems to direct the reactivation stream with contaminants from the absorbent beds back into the VCR reactor.

14. The method of Claim 1, wherein the high temperature reactor is a VCR reactor having a vent system, and wherein there is included the step of adding a C0₂/0₂ synthesizing unit to the VCR reactor.

15. The method of Claim 1, wherein there is further included the step of including a C0₂/0₂ holding tank providing secondary flow to said VCR reactor.

16. The method of Claim 1, wherein the high temperature reactor is a VCR reactor having a feed mixing nozzle, and wherein there is further included the step of feeding the synthesized mixture of a carbon-dioxide/oxygen (C0₂/0₂) through the feed mixing nozzle for the VCR reactor.

17. The method of Claim 1, wherein the high temperature reactor is a hazardous waste incinerator having a reaction zone, and wherein there is further included the step of including - an absorber to produce about 33% acid; - a high pressure HCl stripper and water stripper; and - piping modifications permitting the injection of recycled C0₂ into the reaction zone of the incinerator for cooling purposes.

18. The method of Claim 1, wherein there is further included the step of substantially reducing, if not eliminating any dioxins from the vent steam.

19. A system having a high temperature reactor, including chlorinated hydrocarbon waste incinerators having a HCl purification unit associated with the incinerator, VCR reactors having an anhydrous HCl purification unit associated with the VCR reactor, and the like, having a vent stream, which eliminates the emission of N₂ and C0₂ into the atmosphere, comprising - feeding system feeding a synthesized mixture of a carbon-dioxide/oxygen (C0₂/0₂) fed into the high temperature reactor, substantially reducing, if not eliminating, the N₂ from the vent stream.

20. The system of Claim 19, wherein there is included one or more of the other innovative, unobvious features disclosed in the foregoing specification.