Related inventions include a prior patent application for a Method and Apparatus for the Production of One or More Useful Products from Lesser Value Halogenated Materials, PCT international application PCT/US/98/26298, published 1 July 1999, international publication number WO 99/32937. The PCT application discloses processes and apparatus for converting a feed that is substantially comprised of halogenated materials, especially by- product and waste chlorinated hydrocarbons as they are produced from a variety of chemical manufacturing processes, to one or more"higher value products"via a partial oxidation reforming step in a gasification reactor.

Gasification is one technology for converting halogenated materials, typically liquid chlorinated organic by-products and waste streams (RCl's), into useful products. Successful implementation of a gasification technology could replace liquid thermal oxidation facilities, which are a current industry method for treating these waste streams. Gasification offers several advantages to thermal oxidation, including lower economic costs, reduced emissions and a more optimized capture of the chemical value of the feed stream constituents. Gasification is also more flexible than competing halogenated material waste treatment technologies, in that it has a significantly broader range of acceptable feedstock composition.

A preferred embodiment for a gasification process, in general, is reviewed below in conjunction with an illustrated block flow diagram, Figure 1, and an illustrated gasifier unit, Figure 2.

Soot removal from aqueous streams is generally not mentioned in the gasification literature. This is likely because typical gasification processes centered around essentially hydrocarbonaceous feedstocks are concerned with making one product (synthesis gas), as opposed to also producing a marketable acid, and consequently clean-up of process water to remove soot is typically not a critical operation unit. In contrast, in the gasification of halogenated or chlorinated feeds, as dealt with herein, where a marketable hydrogen halide

acid product is to be produced, efficient soot removal is critical. This invention discloses cost effective and efficient methods for capturing and removing the soot from aqueous streams so as not to contaminate a synthesis gas product and so that a high purity hydrogen halide product can also be produced.

"Gaseous stream", as used herein, refers to gas and/or vapor and/or aerosol, or gas with suspended particles and/or liquid droplets. The instant invention pertains to methods for particulate removal in processes for the reformation of halogenated materials. The methods include mixing a gaseous stream from a reactor (RGS of Figure 3A), the gaseous stream containing hydrogen halides, with a first liquid stream (LS I of Figure 3A) to form a quenched gaseous stream (QGS of Figure 3A). Preferably, the first liquid stream is an aqueous liquid stream, and more preferably, a recycling stream that includes a solution of hydrogen halides, optionally recycled from a downstream absorber. Preferably, the first liquid stream is a quench liquid used to cool the hot synthesis gases from the reactor.

The method includes separating out a first washed gaseous stream (WGS1 of Figure 3A) containing hydrogen halides from the quenched gaseous stream and separating out at least a portion of a bottoms stream (QGS of Figure 3A) from the quenched gaseous stream and removing solids from the bottoms stream portion in a filter unit (see Figure 3B).

Preferably, the method also includes mixing the first washed gaseous stream WGS1 with a second liquid stream (LS2 of Figure 3A) to form an atomized gaseous stream (AGS of Figure 3A). The second liquid stream LS2 is preferably an aqueous liquid stream, and more preferably, a recycling stream that includes a solution of hydrogen halide, optionally recycled from a downstream absorber. Preferably, the method includes separating out a second washed gaseous stream (WGS2 of Figure 3A) containing hydrogen halides from the atomized gaseous mixture and separating out at least a portion of a bottoms stream from the atomized gaseous stream and removing solids from the bottoms stream portion in a filter unit (Figure 3B).

In preferred designs, the quench mixing of the first liquid stream uses a weir quench associated with a vapor/liquid separator drum, and the second, atomizing gas stream mixing with the second liquid stream includes a wet venturi scrubber associated with a second vapor/liquid separator drum. In preferred designs, portions of bottom streams from the first and second separating steps are combined and flowed to a filter unit. That filter unit

preferably includes a primary filter and a secondary filter. Filtrate from the filter unit may be returned for use in the first liquid stream while wet cake is discharged from the filter unit.

A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which: Figure 1 illustrates in block flow diagram stages of a preferred embodiment for a gasification process for halogenated materials.

Figure 2 illustrates in detail a gasification step and process in a preferred embodiment for the gasification of halogenated materials.

Figures 3A and 3B illustrate a quench and particulate removal process for use in the gasification of halogenated materials.

Figure 4 illustrates an absorber process for use in a process for the gasification of halogenated materials.

A preferred embodiment of a gasification process for halogenated materials, in general, is discussed first, for background purposes. The preferred embodiment of the process is comprised of five major processing areas, illustrated in the block flow diagram of Figure 1.

1. Gasifier 200 2. Quench 300 3. Particulate Removal and Recovery 350 4. Aqueous HC1 Recovery and Clean-up 400,450 5. Syngas Finishing 700 Each area will be discussed briefly. A preferred embodiment of a gasification reactor will also be discussed, illustrated in Figure 2. The halogenated materials are assumed to be chlorinated organics in the following embodiment.

Turning now to Figure 1, various liquid chlorinated hydrocarbon feeds (CHCs) are preferably mixed (within reasonable chemical constraints, of course) in a feed tank from which they may be pumped through a preheater to be injected into a gasifier.

The gasifier area 200, as more particularly illustrated in Figure 2 and as further discussed in more detail below, consists of two reaction vessels, R-200 and R-210, and their ancillary equipment for the principal purpose of converting the halogenated material, typically RCl's to synthesis gas and hydrogen halide products. (Halogenated material is

referred to herein as RCl's, a typical form.) The RCl's or the like liquid stream 144 is preferably atomized into a primary reactor R-200, preferably with pure oxygen 291 and steam 298. In a harsh gasification environment the RC1 or the like components are partially oxidized and converted to synthesis gas (syngas), or to a synthesis gaseous stream, comprised primarily of carbon monoxide, hydrogen chloride and hydrogen, with lesser amounts of water vapor and carbon dioxide and trace amounts of other elements including soot, which is essentially carbon. The syngas preferably flows into a secondary reactor R- 210 to allow all reactions to proceed to completion, thus yielding very high conversion efficiencies for all halogenated species and minimizing undesirable side products. Referring back to Figure 1, hot gases from the reactor section 200 are preferably cooled in a quench area 300 by direct contact with a circulating aqueous stream. Quench area 300 and particulate removal area 350 are discussed in detail below.

From quench area 300, particulate free syngas from a vapor/liquid separator scrubber is next preferably introduced to an acid absorption column 400. Noncondensible syngas components should pass through the absorber overheads and on to a syngas finishing area 700. HC1 in the syngas from the reforming of RC1 feeds is absorbed to a concentrated aqueous acid bottoms stream of about 35 wt percent HC1. This is a high quality aqueous acid stream and is preferably filtered and passed through an adsorption bed 450 to remove final traces of particulates and organics, yielding an aqueous HC1 product suitable for sales or internal use.

A caustic scrubber and syngas flare system can make up syngas finishing area 700.

The caustic scrubber, or syngas finishing column, uses cell effluent in the lower section of the column to absorb final traces of HC1 and C12 from the syngas stream. Water can be used in the upper section of the column as a final wash of the product syngas. If the customer is unable to take the syngas, it can be flared to a dedicated flare system. The spent solution from the column bottoms can be disposed of in a suitable wastewater treatment system (not shown). Having reviewed a preferred embodiment of a gasification reactor process for halogenated materials in general, the gasifier area 200 will now be reviewed in more detail, as illustrated in Figures 2. As discussed above, gasifier area 200, in a particularly preferred embodiment, consists of two reaction vessels R-200 and R-210 and their ancillary equipment for the principal purpose of halogenated feed material reformation and conversion to higher value products. For the purpose of the following discussion the

halogenated material will be assumed to comprise RCl's, a typical form. The RC1 liquid stream is preferably atomized into a primary reactor R-200 with preferably a pure oxygen stream 291 and a steam stream 298 through a main burner or nozzle BL-200.

In the harsh gasification environment the RC1 components are partially oxidized and converted to synthesis gas (syngas) comprised primarily of carbon monoxide, hydrogen, hydrogen chloride, and lesser amounts of water vapor and carbon dioxide, as well as trace elements including particulate carbon (or soot). The syngas preferably flows into a secondary reactor R-210 provided to allow all reactions to proceed to completion, thus yielding very high conversion efficiencies for all halogenated species (all RCl's) and minimizing undesirable side products.

Primary gasifier R-200, in the preferred embodiment illustrated, functions as a down fired, jet stirred reactor, the principle purposes of which are to atomize the liquid fuel, evaporate the liquid fuel, and thoroughly mix the fuel with oxygen, a moderator, and hot reaction products. The gasifier operates at approximately 1450°C and 5 bars gauge (barg) (75 psig). These harsh conditions insure near complete conversion or reformation of all RC1 or halogenated organic feed components.

The secondary gasifier R-210 in the preferred embodiment functions to allow the reactions initiated in the primary gasifier to proceed to equilibrium. The secondary gasifier R-210 operates at approximately 1400°C and 5 barg (75 psig). This is simply a function of the conditions established in the primary gasifier, less limited heat loss Almost all of the oxygen is consumed in the primary gasifier R-200.

The following represents typical operating performance of the gasifier system with respect to production of species other than the desired CO, H2, and HC1 : Exit gas C02 concentration : 1.0-10.0 volume percent Exit gas H20 concentration : 1.0-10.0 volume percent The following example is provided for background.

Example 1 The following feed streams were fed to the gasifier through an appropriate mixing nozzle: Chlorinated organic material: 9037 kg/hr Oxygen (99.5 percent purity): 4419 kg/hr Recycle vapor or moderator: 4540 kg/hr

[58. 8 wt percent water vapor, 41.2 wt percent hydrogen chloride] The resulting gasification reactions resulted in a synthesis gas stream rich in hydrogen chloride and chamber conditions of approximately 1450°C and pressure of 5 bars, gauge (barg).

Given the foregoing description of a preferred embodiment of a gasification process in general, including a gasifier and the products of gasification, preferred embodiments of the instant invention are discussed below, having particular reference to Figures 3A, 3B and 4. The halogenated material will be assumed to be chlorinated organics and the hydrogen halides, below, will be assumed to be HC1. As above, the term gaseous stream includes gases and/or vapors and/or aerosols containing particulate material and/or liquid droplets.

A hot gaseous stream 210 (the RGS), as from reactor R-210, is preferably cooled in a quench area 300 by direct contact with a liquid stream 317 (or LS1), preferably a circulating aqueous hydrogen halide or hydrogen chloride stream. The reactor effluent syngas and the aqueous stream are preferably intimately mixed in a weir quench vessel Q- 310. The mixture, or quenched gaseous stream, then preferably flows to a vapor/liquid separator D-310, such as a drum, from which a first washed gaseous stream WGS1 passes overhead. A bottoms liquid stream 311 (the QGS) from the separator D-310 is preferably pumped, as by pump P-310 A/B/C, and cooled, as in cooler E-310, and recycled to the weir quench Q-310 as liquid stream 317.

The first washed gaseous stream WGS1, exiting separator D-310, preferably passes into an atomizer or venturi scrubber VS-320, preferably a wet venturi scrubber. The particulates in the first washed gaseous stream, consisting primarily of soot, are scrubbed from the first washed gaseous stream in the atomizing wet venturi scrubber by means of the entrapment of the particles in liquid droplets. A scrubber liquid stream LS2 is preferably operated in a circulating loop, in that bottoms liquid stream 322 is preferably separated in a subsequent vapor/liquid separator drum D-320 and recycled. A blowdown stream 325 from the scrubber liquid recycle system, see streams 323 and 324, is preferably combined with a slipstream 314 from the quench liquid recycle system, see streams 312 and 313, and flowed to a filter unit, preferably a continuous candle filter particulate recovery unit 350.

In one embodiment of this particulate recovery unit 350, Figure 3B, primary filter FL-310 would remove solids from these process streams 314 and 325 and discharge the solids as a concentrated slurry 354. Preferably, this concentrated slurry stream 354 would

be forwarded to a secondary filter FL-350 where the slurry would be filtered and dewatered to a wet cake, which could be discharged as stream 355 to an RC1 feed tank for recycling to a gasifier, or to an appropriate disposal system. Alternatively and preferably, the particulate recovery unit 350 can be operated with a single filter unit producing dry cake, as for example in Figure 3B wherein the quench liquor slipstream 330 is fed directly to FL-350.

It has been found that capture of particulates from a gasification process for halogenated materials is accomplished effectively with a gas wash and more particularly with two gas washes, a quench combined with an atomizing scrubber system. It has also been found that the particulate, consisting essentially (or almost entirely) of soot filters effectively with a candle filter system. Importantly, a second washed gaseous stream WGS2 exiting scrubber liquid/vapor separator and feeding an HC1 absorption tower, such as T-410 of Figure 4, is essentially free of particulates (only a small cartridge filter system would typically be needed to remove trace particulates for stream WGS2.) A preferred weir quench design Q-310, illustrated in Figure 3A, which performs the first gas wash, is essentially a short vertical weir cylinder which penetrates a flat plate.

Quench liquor flows into an annular volume created between a vessel wall and the cylinder above the flat plate. The liquor continually overflows the top of the cylinder and flows down the wall of the cylinder. Simultaneously hot gases also flow down through the cylinder into the region below. This co-flow of liquid and gas, with liquid evaporating as it cools the gas, creates an intimate mixing and a cooling of the gas stream. An inventory of liquid around the weir can serve as a reservoir in the event of a temporary interruption of liquid flow. In a preferred operating manner, the liquid flow would fully wet the weir ID, creating a full liquid curtain in essence, but would not completely fill the cross-section of the weir. That is, a gas flow area is still available down the weir diameter. In such a manner, the weir quench Q-310 functions as an effective gas wash for removing contaminants due to the inherent gas-liquid contact. Both particulate and other trace gas species are removed to a certain extent, with removal efficiency increasing with an increasing liquid operating rate. Such a weir quench, in particular coupled with a further downstream particulate scrubber VS-320, should remove essentially all aqueous acid soluble impurities from a gas stream, so that aqueous acid produced in a downstream absorber can meet impurities limits of Aqueous HC1 Specifications. These impurities in question include primarily NH3, metals and metal salts.

Captured particulate is effectively removed from a circulating quench liquid stream by means of the above described slipstream filter system inserted between a quench circulating liquid pump P-310 and quench circulating liquid cooler E-310. Flow of stream 314 can be adjusted to maintain a solids concentration in the bulk stream at less than 0.10 weight percent at all times. At an expected maximum soot yield of 0.5 wt. percent yield of RC1 to soot, for instance, this requires approximately 75 liters/minute (20 gpm) of slipstream flow. Higher concentrations may increase erosion rates and plugging potential.

A preferred filtration operation itself is covered in more detail below.

Particulates remaining in a first washed gaseous stream WGS 1 from the above quench system, the particulates consisting primarily of soot, are further effectively scrubbed from the gas stream in atomizing scrubber VS-320, preferably a wet venturi scrubber, as discussed above. The atomizing scrubbing system typically would operate at 90-110°C and at syngas system operating pressure (which might nominally be 4.8 bars, gauge (70 psig)).

Normal vapor load or flow is I actual cubic meter/second (2100 actual cubic feet per minute under operating conditions) requiring approximately 1875 liters/minute (500 gpm) aqueous scrubbing liquid (being preferably 30-35 wt. percent HC1). Pressure drop across the atomizer would typically be 0.7 bars (10 psi). Solids concentration in the circulating scrubber liquor would be about 0.5 wt. percent. Final particulate removal from a syngas stream is preferably accomplished with such a venturi scrubber VS-320. Efficient particulate removal is desired to prevent downstream equipment plugging problems and to meet syngas particulate specifications. The venturi technology is one of the more efficient technologies for removing very fine solids from a vapor stream. The high energy expended through a venturi improves the capture efficiency for particles of all sizes compared to other wet scrubbing devices. Pressure drop through a venturi would preferably be approximately 10.0 psi. The particles penetrate and are trapped in liquid droplets through the fluid acceleration and deceleration created by the venturi. Pressure drop is optimized to maximize atomization and velocity differentials for particle capture. Pressure drop is, however, limited below the point where atomization of the liquid becomes too fine, creating droplets which are too small to practically separate in the scrubber vapor/liquid separator.

Preferably, a three phase mixture from the venturi VS-320 would be discharged tangentially into a vapor/liquid separation drum D-320. This tangential entry can create a cyclonic effect, the centrifugal force of which forces the liquid droplets (with captured

solids) to the walls where they coalesce and gravity drain to the bottom. A radial vane demister followed by a chevron vane demister in the upper half of the separator drum (not shown) may be used to achieve greatest liquid droplet removal from the gas stream. An essentially particle-free gas stream WGS2, thus, may flow on to an HC1 absorption system 400.

Bottom liquid stream 322 from a scrubber vapor/liquid separator, which is actually a very dilute slurry, can be pumped by pump P-320, directly back to the inlet of the venturi scrubber VS-320. Preferably approximately 80 percent of the scrub liquid stream LS2 is atomized directly into the center of the venturi throat via a pressure atomization nozzle. The remaining liquid is preferably introduced via several tangential nozzles to create a swirling film of liquid which wets the walls of the venturi into the throat. For effective scrubbing efficiency, liquid to gas ratios are preferably maintained at or near 0.25 gallons of scrub liquor per actual cubic foot of gas. Due to the vigorous gas-liquid contact in the venturi, this scrub liquid should be very near equilibrium with the gas phase. That is, the scrub liquid is typically 30-32 wt. percent HC1 at base design conditions. Makeup liquor for the system can be supplied from an absorber bottoms stream 406 from an absorber system 400, which should be at a high enough HCl concentration to avoid absorbing HC1 from the gas, rather letting it pass through to where it can be captured as saleable acid in the absorber.

A continuous blowdown stream 325 to filter unit 350 for particulate recovery controls the solids concentration in an atomizing liquid recirculating loop. Solids concentration may operate best at approximately 0.5 wt. percent, and preferably at no greater than 1.0 wt. percent solids. This blowdown to a filter unit also serves to control the aqueous chemistry of an atomizing liquid recirculating loop, helping to limit salt and metal concentrations to acceptable levels.

Scrubber liquid stream LS2 preferably operates in a circulating loop, and as discussed above, a blowdown stream 325 from this scrubber liquid recycling system is combined with the slipstream 314 from the quench recycling liquid system and both flow to filter unit 350, preferably the continuous candle filter unit. Normal flow to the primary filter FL-310 might be approximately 750 liters/miunute (200 gpm) at 100° C and 0.10 wt. percent solids. Primary filter FL-310 removes solids from the process streams and discharges them as concentrated slurry stream 354 which is forwarded to a secondary filter FL-350 where it is filtered and dewatered to a wet cake 355, which can then be discharged

to an RC1 feed tank for recycle to a gasifier, or to packs for transport to a site kiln, or to a landfill for disposal. The primary filter FL-310 functions similarly to a conventional baghouse, only in liquid service.

The primary filter FL-310 is preferably comprised of a pressure vessel containing multiple filter elements. Several candle/sock type filter elements make up a cluster. The clusters are herded together external to the vessel and valved so they can be individually isolated and backpulsed. Forward element flow is from OD to ID. Solids cake is collected on the OD of the element, and is periodically backpulsed where it settles to the bottom cone of the vessel. Clusters are pulsed sequentially such that the filter remains in service as a continuous operation. The backpulse fluid can be dilute acid from a dilute acid pump.

Filtrate 315 can flow to an environmental area for collection and disposal, or to the quench cooler E-310.

Solids which settle to the bottom of a primary filter vessel can be periodically discharged as a concentrated slurry stream 354 at 2 percent wt. to a sludge holding drum D- 350. This tank is agitated to maintain the solids in complete suspension. This sludge is then preferably pumped to a secondary filter FL-350.

The secondary filter FL-350 is of a similar design to the primary filter FL-310, but operates in a different mode. The slurry again flows from OD to ID of the elements, with cake collecting on the OD. Upon a timed interval, or maximum differential pressure, slurry flow is shut off and the vessel is allowed to drain free of liquid. Nitrogen flow is then forwarded through the filter to blow free liquid out and partially dry the cake. The elements are then backpulsed with nitrogen to dislodge cake, which falls through a bottom filter cone and into a wet RC1 tank. Tank agitation mixes and suspends the particulate in the RC1 liquid and can be fed back to the gasifier where it can be gasified. The cake would be approximately 50 percent wt. moisture.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials, as well as in the details of the illustrated system may be made without departing from the spirit of the invention. The invention is claimed using terminology that depends upon a historic presumption that recitation of a single element covers one or more such elements, and recitation of two elements covers two or more such elements.