Document bB2k3VGbD8vemXL8rwMDwbaoD

inter office memo TENNECO CHEMICALS, INC. To Route List F ROM F.W. Kanzler Subject VCM Sampling - EPA At At Burlington date November 3, 1977 copy to R.A. Injewski P.M, Reed File Attached are copies of two articles which may be useful in our effort to install sampling loops for rail car and in-process VCM sampling. Attachments (2) FWK/jst JnjYf. tic^ F.W. Kanzler Route List Rj,H. Mathis Sandstedt P.R. Scarito A.C. Siegel COLORXTE 019064 >` EMlSSIOt^ONTROL:!. . Control Methods for Vonyl Chloride Some tips on how PPG handles sample collection and analyses of VCM, and on how it handles the tricky aspects of loading operations. i.. Z. G. Bell, Jr.f J. C. Lafleur, R. P, Lynch, and G. A. Work, PPG Industries, Inc., Pittsburgh, Pa. Vinyl chloride monomer (VCM) is hazardous not only because it is highly flammable, but also because of its toxicological effect on human beings. Consequently, the design and operating procedures of our vinyl chloride facilities at Lake Charles, La., and Caribe, P.R., provide that the release and exposure of VCM to personnel be minimal. This article describes two procedures that we have adopted, which have contributed to improved VCM confinement and employee exposure control. Sample collection and analyses The first of these techniques involves sample collec tion and analyses. In our process, quality control sample collection is achieved from different points in the system by attaching the sample cylinder or bomb to a small fit ting in a closed loop system, Figure I. The sample bomb is installed vertically in the system with its stand leg fit ting in the top position to prevent overfilling and bomb overpressurization. The bomb is equipped with a safety relief valve as further protection. To assure that the bomb is inserted properly, its fittings are of different sizes. The sample collection lines are small diameter stainless steel tubing. Valves are located as dose as possible to the sample bomb connections to minimize the quantity of vinyl chloride in the tubing. Before the bomb is removed, the small amount of vinyl chloride trapped between the valves is released to a remote location, and the tubing between the valves is purged with nitrogen. The storage of sample bombs within the main or plant laboratories is prohibited, and although these sample bombs were.capped between use, a storage rack or cabi^|t similar to a gun rack is provided, Figure 2. All vinyl ^Hloride bombs must be stored in the cabinet while not in ^mse, and all analyses of samples must be accomplished . within a laboratory hood. A flexible line is installed on the gas chromatograph back into the laboratory hood. COLORITE 019065 After the analysis, there is from COO to 700 ml. of vinyl chloride remaining in the hoinb. The wimple bombs arc capped and returned to the plant where the bomb and its residual contents ore inserted during the next sample collection round its', the unused vinyl chloride to the process U Figure 2. Storage rack for sample bombs. The bomb valve integrity is cheeked periodically using n Century organic vapor analyzer. All laboratory hoods where vinyl chloride is used or analyzed have been checked for adequate capture velocity. A baffle has been installed across the front lip of the hood to prevent any vinyl chloride vapors, which arc heavier than air, from exiting the hood. The levels of vinyl chloride are routinely monitored. Loading operations ~j^ The second procedure involves loading operations for tank cars, tank trucks, barges, and ships. The potential problem areas are sampling, vehicle emissions, vehicle gauging, and loading line clearing. The oxygen content of empty transportation vehicles is determined prior to loading, and the oxygen analyzer is vented remotely so that personnel exposure is avoided. There are equalizing lines so that vehicle vapor content may be displaced dur ing loading. See Figure 3 for tank car loading. The vapor space material is equalized with the storage tank from which the vehicle is being loaded. There are a number of ways to determine when a tank car or tank truck is full. The vinyl chloride may be scale loaded (for trucks and cars), or a flow meter may be used. A magnetic level indicator is used by some producers. Special procedures are required so that personnel expo sure may be avoided. Exposure may be prevented by us ing a flexible hose to connect the gauge rod to a bull's eye. Liquid can be observed in the bull's eye when the car is rilled. The bull's eye must be vented remotely to an in cinerator or tall stack, as shown in Figure 3. The final problem of loading operations is the clearing of the loading hose so that the hose may be disconnected without allowing exposure. The liquid in the loading hose A* -7.;' Y*r. YY v Y vcw v-vv7>-;'" -v.r'' roU>UZ,SJC3 S>au.5rre--n I "t] I v-.in'. 'i'.hr :j.'. V K` Vow ozzev ccx/zmc'ctb' <3,cmgvvvi3' cev/Of-- /cz'x/ace z^xsas'.7 ,,VJ, I .:! r $*/:-'V- V. 7v:7;iv-:: - &T*Ct /*' i.:,v*. ,;r! ** : ' ,'/.=h *tAv1 S 'O . '-'7. ' , Figure3. Piping diagram for tank car loadinq. TXkj*' C47 4A COLORXTE 019066 must be pushed (with nitrogen) into the transportation vehicle. The loading line is then nitrogen-purged to an in cinerator or tall stack so that vinyl chloride vapors are removed before the hose is disconnected. The displacement of inerts to the storage tank from transportation vehicles during loading operations will cause the storage tank pressure to be excessive as the tank is refilled unless a recovery system is provided. If a refrigerated vent recovery system is used, some vinyl chloride must be vented to the atmosphere or to an in cinerator. A viable alternative is to compress this stream and feed it to the plant process where the VCM is recov ered and the inerts, normally nitrogen, accompany the byproduct HC1 stream. Figure 4. Clearing a filter There are other procedures that may be followed so that equipment can be cleared for maintenance work, or made ready for service without exposing personnel to VCM. In order to do this, some high pressure nitrogen must be used and a sufficient amount of nitrogen must be available for purging. The procedure for clearing a filter for element replacement will provide an example of how most process equipment and piping may be cleared. Fig ure 5. The first step is to push the filter liquid into the pro cess piping with high pressure nitrogen. The filter is then blocked and the filter depressurized through a hose to a vent system. The final step is to continue a small nitrogen purge through the filter until VCM is removed. After the elements are removed and replaced, the filter is nitrogen purged to remove air and a leak check is made. The filter is then depressurized and filled with vinyl chloride. When the filter is completely filled, a nitrogen purge is used to clear all hoses to the vent'system prior to disconnecting. # CHEMICAL ENGINEERING PROGRESS (Vol. 71, No. 9) September 1973 COLORITE 019067 47 =MISS!<5igf(CONTROL:' Control of Sn-franssf VCM The only certainties regarding VCM regulations is that they are here to stay, and that industry will have little to say concerning employee safety andplant procedures. R. N. Wheeler, Jr., and M. E, Sutherland, Union Carbide Corp., South Charleston, W.Va. From the standpoint of safety, the primary objective in transporting vinyt chloride monomer (VCM) is to pro tect shipping personnel and the public from excessive exposure to VCM emissions. With this in mind, the Oc cupational Safety and Health Administration (OSHA) has issued a standard for workers, which will be fol lowed by regulations from the Environmental Protection Administration (EPA), the Department of Transporta tion, (DOT) and the Coast Guard. The OSHA permis sible exposure limits of X part/million by volume for workers, and the rumored EPA limit of 90 parts/billion by volume for plant fence-lino concentration are hard to conceive in an industrial environment. Gauging a tank car with a slip tube releases several pounds of vinyl chloride to the atmosphere. One pound of vinyl chloride raises the concentration of 6 million cu. ft of air to X part/million, or 70 million cu. ft. of air to 90 parts/ billion. While the subjects of safe vinyl chloride con centration and the health problem resulting from vinyl chloride exposure may be debatable, governmental reg ulations in regard to workers and public exposure are here to stay. There are no easy solutions to emission control; thus, the scope of this discussion is limited to .a brief review of vinyl chloride transportation operations, defining some major problems, and proposing some ways of approach ing the solution to those problems. Most transport via rail or pipeline Vinyl chloride distribution facilities generally consist of large storage tanks such as refrigerated spheres or buried tanks located at some distance from the produc tion facility, smaller horizontal storage'vessels located in or adjacent to the production facility, pipelines. shipping containers, and loading or unloading facilities for these containers. Some vinyl chloride monomer is moved by tanker, by truck, and by barge but, in the main, transport is via tank cars or pipelines. Figure 1 shows a flow sheet of a representative vinyl chloride distribution system. The shipping containers and the storage tanks are pressured by the vinyl chloride vapor they contain. Theoretically, a tank car containing only vinyl chloride gas can be loaded without venting. On a more practical basis, these containers are vented either to the aiT or back to the storage tank from which ultimately some inert gases must be released. The loaded tank car is then valved in, loading hoses are removed, and it is moved via rail to the consumer. Upon arrival, unloading hoses are attached, pressure in the car is raised above that generated by ambient temperature with vapors from a vinyl chloride vaporizer, and the con tents pumped to a storage tank. At the completion of the unloading, the pressure in the car is reduced by a compressor to 1 to 5 lb,/sq.in. gauge. The car is valved in and the hoses removed. The consumer's system is also pressured by the vapor pres sure of vinyl chloride, but again some venting of inert gases is required. For normal distribution operations, major emissions result from slip-tube gauging of the tank car, TemovnI of loading and vent hoses, and any venting required to maintain the storage tank pressures at the pressure of saturated vinyl chloride vapor. Vapor compression and condensation are often used for tank cooling. The pres ence of large amounts of uncondensable gases would pre clude the operation of such a cooling system. The plant usually has a remote vent stack or a flare for handling these vents. Formerly, when equipment maintenance was re- 48 September 1975 CHEM1CAI ENGINEERING PROGRESS (Vol. 71, No. 9) COLORITE 019068 the item was emptied of liquid vinyl chloride ; j^^)ble, the pressure released to a vent system or to he^ff, and the equipment' purged with inert gas to reuove the contained vinyl chloride gas. The inert gas was hen removed by a thorough airing. On completion of the maintenance, the equipment wa3 purged with inert gas followed by displacement of the inert gas with vinyl chloride. Gases released were vented to a flare stack or simply released to the ambient air. Maintenance work on a tank car could result in release of 500 lb. of VCM while a simple pump repair might re lease 1 to 10 lb. Design of storage systems often stressed vapor conservation for operational emissions, but only rarely was provision made to control emissions resulting from maintenance work. Emission reduction is costly The various governmental safety regulations will re quire changes in distribution equipment and operations to control VCM emissions. Reducing emissions to achieve the permissible levels of exposure required is arduous, expensive, and time-consuming. A thorough and detailed discussion would require more space than is available; therefore, only certain useful items will be covered in the following. " * Gauging devices that permit no product emission must be installed on tank cars, tank trucks, and barge tanks. A common practice when loading a shipping vessel in the past was to pull the slip-tube out to the desired liquid I .: * , * Mi^> i mt*** COLORITE 019069 v. t,'f' ' - \ * * piv1; K. ' . Figure 3, Solvent - . ' {W-**;/. :!*>* j vent . jP.V...scrubbing . system.' j; is" 4 -> t"'* >>'<> ' pv-i',' ' '/ VV / - >' , ^i V - W`.. '**7 4 '*' ** V'"w - 4 4 jStrippio, l-K:4-%> 't I CfllttHtt ' 1 " V l* < *'',-* ' 1 * **i*.*"'#n*,i11 , ,yI.J**>; * *i -* "* t' " * I**i\l:' ,--hit jjrf;^\ iK--.4r- r*.'*f:*l-*AU*-j.'. *i 2i4> v Q< _i*tjii,t*J-***-Aj* . f * ^ v-T M -*t:-:U '' * i j'f, r*if ;** * >-* \ ;jCi} txi :/f vi\v "'ft >-w * S'f^i'JTfic'tlt'.>c'r*?srl*yti*21*T-r:t; T.f:' *<---l5 ;** , .>-*! *' * (,rilt.< ,lr Mt*4'-' \ ' -'. r *S >- *i.--4j VifrfefcMn^ w~*7?,-sTi*<^ i n--if `V yR.fcrtUp^;: i-.:`:; .1 . , .' s fain 4 J*t**<i'f---t-W------ ----"f--I^'w^/r<?'cg'v}?T'a-.t*T^**"1 ' K: ; :. Figure 4. '/Refrigerated g^VV;;-vent ' f-'fv/ system, p%V?*ivi/rV >'''" ./.. .-.. f. -r/` J.' level and open, the valve slightly. When the vessel was filled to the desired level, the sporting of liquid was readily visible to the loader from a distance, and loading was stopped. This procedure also took care of any air or other nopcondensable gases that might be in the car. As a result of the OSHA regulation, various ventilation hoods and sight-flow indicators are being used in loading and unloading operations. A gauging device that has worked well on tank cars is a float magnetically coupled to a tape system in a pipe isolated from the product. In the event of a failure of the mechanical tape system, it can be removed for repair without emptying the car. The tape sightglass simply protects the tape assembly from the weather. The tank can be gauged by reading the tape and measuring the tank temperature. Adaptation of this or similar devices to all shipping containers is the most direct approach to control of gauging emissions. Tank car size is being limited to 2r>,500 gal. for all new cars in vinyl chloride service. The car must be insulated or have steel safety shields on the ends to reduce the pos sibility of tank punctures in derailments. Cars that are not insulated or do not have the safety shield must be switched individually by engine in the rail yards. Major industry use of a poorly-designed, 38,000 gal, tank car for vinyl chloride transport has caused much of the railroad transportation hazard and the resulting reg ulations. These cars, with their six-wheel trucks, were unable to round a normal railroad curve properly. As a SO ' ' September 1975 CHEMICAL ENGINEERING PROGRESS (Vol, 71, No. 9) COLORITE 019070 > result, they demited frequently, especially when empty. The coupling* often did not mulch properly with oilier cars in switching: thus, in switching and train make-up, the coupler missed connection and the tank car was punctured when it struck the car being coupled. Lit.Stations on car size and handling procedures are highly regressive steps and fail to approach directly the problems of proper tank car design and of failure by the , railroads to maintain their road'beds. For an industry changing to 30,000 gal, reactors, the proper tank cor for minimum emissions is the 48,000 gal. tank car, equipped with float gauging and insulation. In requiring the small tank cor, the Department of Trans' portation has reduced some of the danger of the in dividual nccldent at the risk of increasing the cost of transportation and of increasing the frequency of ac cidents by requiring more tank cars for vinyl chloride transportation. Pipelines offer the ultimate potential reduction in emissions for VCM distribution, but pipelines carrying suspected ca rcinogens will be subject to a new set of rules. Above-ground pipelines can be properly labeled and monitored regularly-for leaks. Emergency procedures could be instituted quickly before any leak became sig nificant. Buried pipelines will require above-ground warning signs, a foolproof system for leak monitoring, and cathodic protection. Double pipe system is the most dependable The only foolproof system for leak monitoring in a buried pipeline appears to be a pipeline within a pipeline. The outside pipeline would provide the basis for leak de tection and disposition. Ill either the above-ground or buried pipeline, the num ber of flanges, valves, and pumps should be minimized while provisions for prompt isolation of leaking sections and disposition of their contents must be planned with great care. In-plant pipelines impose little or no regulatory prob lems, but the likelihood of getting a permit tojnstall a vinyl chloride pipeline on public property' appears remote. Vinyl chloride scavenging systems will need to be in stalled or expanded so that each pipeline, heat exchanger, pump, tank, or tank car can be stripped of vinyl chloride liquid or vapor in the event of failure, prior to Inaintenance work, or prior to routine disassembly. Fig ure 2 shows a flowsheet of such a system. Where there is access to a plant monomer recovery sys tem, an additional compressor, a condenser, and a collec tion tank are not needed. In remote facilities, this scavenging system could consist of a small compressor, such as the Corken built by Pump Service Co. This com pressor requires 80 h.p. and will pump 40 to 54 actual cu.ft./min. from 0 to 105 lb./sq.in. without lubrication. If the compressor discharge system has the ability to absorb heat, then the condenser is unnecessary. This compressor has been used to evacuate unloading hoses, tank cars, and other equipment at a tank car un loading station. The compressor may be discharged into the liquid vinyl chloride transfer pipeline without cooling Figure 5. Manual vinyl chloride mono- mer monitoring with a portable organic 1 vapor detector, .`.y ^-vA/V; CHEMICAL ENGINEERING PROGRESS (Vol. 71, No. 9) September 1975 COLOR!TE 019071 51 if the Rystem has adequate heal dissipation capacity. In nn emergency, it has been simply discharged into an empty tank car. When such scavenging compressor is used inter mittently, provision must be made to keep it from filling u,,. with liquid vinyl chloride. On this installation, electric heaters were installed in the compressor suction trap to vaporize any liquid that collected during the out-of* service time. Activation of the heaters for a preset time is required before the compressor will start. The scaveng ing system must be designed to fit the operation involved. The most important criteria to consider in such a de sign is to he sure all .eventualities requiring scavenging have been considered, and to be sure that air is excluded from such a system. Inert gas purging of equipment that has been scavenged of its available vinyl chloride monomer is necessary to re duce the explosion hazard and to remove the last traces of monomer. A tank-car unloading hose that has been scavenged contains several tenths of a pound of vinyl chloride. A tank car contains several hundred pounds. This material must be removed and the VCM concentra tion in the equipment reduced. One tank car shop has al ready notified owners it will not accept tank cars for servicing containing more than 25 parts/million VCM. Dependingon the equipment configuration, it may be swept out by blowing inert gas through the system or it may be diluted by alternately pressurizing the tank with inert gas and venting it down. In any case, sweeping the last traces of vinyl chloride out of equipment prior to maintenance generates a large volume of inert gas con taminated with VCM. Inert gas supply 5s needed A rule of thumb for the pressurizing and venting tech nique is 15 to 20 cu.ft. of inert gas per cu.ft. of vessel capacity. The inert gas must then beTemoved by airing, if vessel entry is required. When maintenance is complete, the process must be reversed with inert gas purging out the air and then vinyl chloride purging out the inert gases. Maintenance of distribution facilities and trans portation equipment will require a supply of inert gas and Figure 7. VCM storage sphere equipped .. with remote controlled valves and r pumps.' : .... . the equipment tu dispose rif the VCM contaminated inert gns. Refrigerated solvent scrubbing of inert gas streams, as shown in Figure 3, represents the most reliable and economical means of removing vinyl chloride from inert gas. The choice of solvent is lurgely a matter of which ones are readily available, the conditions chosen for stripping the nWsolved vinyl chloride from the rich sol vent, and limiting the loss of solvent with the vent gas stream. Solvents that have been used successfully are acetone, methyl ethyl ketone, ethylene dichloridc. hutyl acetate, and heptyl butyl ketone. Absorber temperatures of 0 to -20'C. are effective. To keep equipment sizes down, a solvent scrubber is normally operated under pressure in conjunction with the vinyl chloride scavenging system. Vinyl chloride recovery efficiencies of 99.570 are readily obtained. Solvent rates of 4 lb./lb. of gas at 100 Ib./sq. in. gauge and 10'C. yield essentially vinylchloride-free vent gas. Refrigerated vent coolers are useful only where the vol ume of inerts is very low or more efficient recovery equip ment is not available. Figure 4 shows an inert gas purge system that operates in conjunction with a large re frigeration system to rid a storage sphere of inert gases. This unit requires 2 h.p. to cool inert gases to -29'C. and discharge heat at 6*C. The inert gas discharged to the air contains 13 vol. % VCM. The storage sphere using this unit is remote from other operations and receives little or no operating supervision. In this case, the amount of vent gas is essentially insig nificant and, due to remoteness, no personnel exposure is involved; thus, a relatively poor system is acceptable. Decontamination of vent gases by other methods, such as carbon adsorption or incineration followed by scrub bing the incinerated gas with water, are being considered by many companies. In the case of carbon adsorption, the technology is not fully defined and proven in practice. Operation of the ad sorbers is cyclic, requiring more operating labor. The for mation of polymer and peroxides on the carbon could be problems. Incineration, or flare stacks, are widely used for dis posal of flammables and should be used as a final cleanup technique for even solvent-scrubbed vent gases. Use of incineration to dispose of relatively large amounts of vinyl chloride would entail removal to the hydrogen chloride generated by water scrubbing and subsequent disposal of acid formed. Disposal of quantities of salt, muratic acid, or hydrogen chloride is a pollution problem not lightly considered by EPA. Monitoring vinyl chloride concentrations in distribu tion operations is necessary to determine sources of emis sions and to protect personnel and the public from exces sive exposure to vinyl chloride in their breathing air. For general troubleshooting and survey work, one oT the most adaptable instruments is the Century organic vapor analyzer, with or without the chromatographic column attachment. This instrument. Figure 5, is por table and is direct reading in terms of organic vapor. If there is a question as to whether the organic vapor is vinyl chloride, then the chromatographic column attach ment, has value. In addition to locating leaking pump seals, valves, and other fixed equipment, it should be used to carefully check each loaded tank car or other shipping container for leakage prior to shipment. Admittedly, a shipping container can develop a leak in transit but, in most cases, the container was leaking when shipped because this was the last time the container's mechanical equipment was operated. 52 September 1975 rucnir*! cwriKw....-------------- COLORITE 019072 For large, fixed distribution facilities, a fixed area monitor with alarms, such as the multipoint automatic chromatograph, is valuable. Fixed distribution facilities are usually remote from plant operations and may not even be manned full time. This lack of supervision, plus the potential for massive VCM releases, makes auto matic detection a primary protective device. The automatic chromatograph in Figure 6 analyzes 19 points within a remote vinyl chloride tank car unloading and storage system every 40 minutes, and it will sound an alarm if a preset concentration is exceeded. Auto matic analyzers, unfortunately, provide more data than can be readily assimilated by the operating supervisor; therefore, a data processing system is worthwhile. These systems compile and correlate results so that problems, other then emergencies, can be identified. ta to be filed for 30 years t.egardless of the technique or the equipment for monitoring, it should be done frequently and thoroughly. The monitoring data should be carefully evaluated and kept on file for up to 30 years, if personnel exposure is involved. If the evaluation identifies a problem, then prompt action must be taken. Monitoring provides the basis for demonstrating com pliance to governmental regulations and, as such, is re quired. In addition, it 13 the means by which equipment is improved, faulty work practices are corrected, emer gency situations are controlled, problems are identified and, above all, personnel are protected from excessive exposure to vinyl chloride. Monitoring is the means one uses to see the situation and, as such, it is the most im portant action to be taken in the control of vinyl chloride emissions. Timely data from monitoring, though expen sive in terms of equipment, is less costly than using yesterday's data on today's problems. Automation is the final approach to control of person nel exposure to vinyl chloride. Regardless of the system design, the potential for personnel exposure to vinyl chloride exists; therefore, removal of personnel from that operation via automation reduces hazards as well as cost. Vinyl chloride storage tank areas may be barricaded and never entered in normal operations. Tank car un loading or loading can be designed so that the only human intervention is the unloading hose coupling or un coupling, Equipment for these kinds of operations are lu^es with position indicators, pipeline flow indicators, ^^p>te-operated pumps, remote-control valves, and pro-. ^mimed controllers. The vinyl chloride sphere in Figure 7 with attendant pumps, refrigeration equipment, and pipelines is oper ated entirely by remote control from a central control room. The tank car unloading system in Figure 8 requires manual hookup anrf disconnections of the unloading hoses and operation of the shutoff valves on the car and at the hose ends. All oLlicr operations arc controlled from a control building. The foregoing was intended to show some of the-ways to reduce vinyl chloride emissions and control personnel exposure in distribution. No implications of governmen tal approval for the techniques involved should be drawn. While the various procedures will lead to minimum expo sure to vinyl chloride, the ability to. meet the various regulations is not implied through use of the same. In controlling vinyl chloride emissions and_rcducing personnel exposures, interaction of regulations and goals from OSHA, EPA, DOT, and the Coast Guard must be considered; i.c., ventilation of the work space may please OSHA while creating EPA problems. The only certainties regarding vinyl chloride regula tions is that they are here to stay and that the latitude available to the vinyl chloride monomer and polymer in dustry, with regard to employee safety and to plant pro cedures, will be minimal. f R. N. Wheeler, Jr., ossistonf production manager lor vinyl chloride resins ot Union Corbide Corp,, is o graduate chemical en gineer from Virginia Polytechnic Institute. Wheeler, whp hai been associated wi1h the manufacture of vinyl resins for 30 years, has represented the firm in various aspects of the vinyl chloride health problem. M, E, Sutherland bos spent most of bis corcer in the production of vinyl chloride ' monomer, ond hos held a number o( su pervisory posts in this orea with Union Carbide Corp. He bos olso worked on sev eral projects involving the development and design of new vinyl chloride monomer plants ond facilities. Since 1969, he has been associated with the Chemicals ond Plastics Safety Group, ond presently holds the position of process safety program monager. CHEMICAL ENGINEERING PROGRESS (Vol. 71, No. 9) September 1975 53 COLORITE 019073