Document nk1OdMmjy5ZZXnvL220Byxo11

internal correspondence: GUL.F 073 0 Y\'^| tU 1 CkoA ^ FROM R* T. Cheng AT San Diego TO H. E. Runion AT Houston subject Vinyl Chloride Exposures at China Gulf Plastics Co. 'Ll ^ -i v -<a 7 v '/ IN REPLY REFER TO RTC 74:048 date 3/29/74 While waiting for charcoal and silica gel samples to be analyzed by Health Sciences Laboratory, I believe it makes sense to summarize the vinyl chloride exposure situations at China Gulf Plastics Co. and re sults of my survey using Century Organic Vapor Analyzer. China Gulf Plastics Company has its main plant at Toufen, which employs some 1,300 workers, and a fabrication plant at Taoyun with about 100 employees. In addition, China Gulf Plastics Company is a minority owner (<15%) of Taiwan Vinyl Chloride Monomer Co. (TVCM). TVCM has one plant at Kaohsiung and one plant at Toufen near the China Gulf Plastics Company's Main Plant. The TVCM Toufen Plant was very new and was not in operation due to technical problems during the time I was in Taiwan. I visited TVCM Kaohsiung Plant which employs some 50 workers. I had the impression that China Gulf Plastics Company was in the process of negotiating to acquire TVCM. The attached map shows the location of the plants in Taiwan. China Gulf Plastic Company's Taoyuan Plant is solely a fabrication plant which manufactures PVC films and PVC fabrics from PVC powders and com pounding ingredients supplied from the Toufen Main Plant. Vinyl Chloride can be present at Taoyuan Plant only through evaporation and seepage from the PVC powder. X detected no^ VC monomer (organic vapors) at Taoyuan Plant with Century Organic Vapor Analyzer. TVCM Plant at Kaohsiung is located within a large industrial complex of Taiwan Alkali Works. TVCM produces vinly chloride monomer by reacting ethylene and chlorine to form ethylene dichloride, and subsequent dehydrochloronation of ethylene dichloride to-form VC and HC1. The process units are in the outdoors. Unit operators spend most of their S-hour working shift inside a modern control room well separated from the process CUSAROSS 02496 Fuchou ({wchow) ^Maisu itchtao Huangchi Tac Piachuan Lichiao T Fuchmg* / Hanchiang V- Haitan Tao Mtichou Tao 'V> v4Nanjih Tao Wuchiu Hsu ROUT! ONE irAiuir i/ufl * '7--'1 pL6fOtaowtmowf*mrnmiitsr fAttpHit.iatrftti^r.A(af (V) N A1 ION At GtOukAMMC VOCICIY Elevations in fed Ho....................fake, river, stream Hsu .................................. tslandis) iichtao........ archipelago, islands Shan.............mounfairtfiJ range Shanmo............mountain range Tan.................................. lake Tao............ ................. ,.island(s) 7nn.\l.u..i.i..I.h..t^^ Tanshui *YeMiu KumyrnShan Weitou .Chilung |K|Un,) $*nchw*<tlJ+nYlC?rr*J?i .`'.PIvu'nhiiiil.ni , ------- ..\. . MHIAGCHWCAARhYilnHg^tfyu^h'gkong . Fottwoscl Straxt Makung* Ching Chuan Kang A Air Force Base Sanhstng Shan + , 7,382 East-WEST +12,742 CfrOSKSiG:shiW.ArA*Y0*'c * , . ' "-EHAIGSTHWCOAAYST v '*Tungshih /FcnSY uan " ' * J , y^^Taroko Gorge Changhua^ s* Ta ich un g ,"'10.768$ Yuanli/;n\Jt Erhlin \ *Tsaotu .Nantou Puli 'b lUUo - Waiehechengf j,C, 'Tar0k i Hualien * Hsiloy ex,,/, *Chushdn / j Touliu 11.440+ C>) x/A I W AeN Penghu Liehtao (Pescadores) ' Ycnshui * Chiai* y ./ /-**TM** \ o Shan + IMourtt hJC'fiton> % U lf* / rty \ Chingpu 439 people per square miic in 1949 (o 963 today, one of the world's highest. f` * r T>rr- -fw **73 GOVERNMENT: Republic, area: 13,8SS sq. mi. POP l&H-H ULATION: 13,JS3,000. LANGUAGE: Mandarin, region- --------------------------- al Chinese dialects cruauc ei chib* mi Japanese under stood as result of occupation by Japan, IS95-I04J. Religion: Buddhism, Taoism, Christianity euonomy; Tea, sugar, bananas, rice, mushroom sex ported Natural resources include coal and marble Industries: textiles, fertilizers, cement NtAJOIt CITIES: laipei (pop l.5oO,GSM, capital; Kno bbing, industry, port. Chilung, port. CLI MATE: Rainy summers, mild u imci ^.H$iny*ng ,y * IP.031+ ^ ' -j Sh<ui/ui t tChiall \l Trui -/.Hslnhoa ry / "-040+ * ,^CKengkung ^Tainan _ 9004+^ \ Chishan# * Meinung . 3.904 V yKdngsnan \ ^ ^Santimcn \i ^7^ Taitung Pjngtung ^ ' *TaUi ^DAlidalatl ' Chihpcn Y kaohstung^ / ' Lu Tao Tungchianq y 5.344 t- f i Fangliao' Hsuhai \ + 2.484 Chechcng Hcngchun* Oiuanpi Hungtou Hsu WsMO^ungtou Hvu' 13 CUSAROSS 02497 R. T. Cheng -2- 3/29/74 area. Vinyl chloride can be present at the dehydrochloronation unit (Pyrolysis Unit) and separation towers through leaks in pipings and vessels. However, I was unable to detect any leak of vinyl chloride from, the process equipment when surveyed with Century Organic Vapor Analyzer. The only significant sources of VC exposures were from the daily routine VC sampling program, and during process equipment main tenance and repair time. The purity of vinyl chloride is checked by sampling the VC pipeline twice per each eight hour shift. Before catching VC into sampling containers, the sampling line is bled for a few minutes in order to obtain a truly representative sample. During the time of bleeding, VC concentration downwind from the sampling point can be very high (1000 to 10,000 ppm three feet downwind from the sampling point). But the sample collector knows to stay upwind from the sampling point and gets very little exposure. Overall, I believe that occupational exposure to vinyl chloride at TVCM Kaohsuing Plant was at minimal levels considering that workers usually spend less than one hour per 8 hour shift at the process area. I have advised Mr. C. L. Chow, Plant Manager at TVCM Kaohsiung, to pay extra attention to providing workers with breathing apparatus and protective clothing during routine sample collection and at process equipment maintenance and repair time. The Toufen Main Plant obtains most of its vinyl chloride monomer from TVCM Kaohsiung Plant through railroad pressurized tank cars. Additionally, it also manufactures part of its VC monomer requirement at the Toufen Plant Site by an old acetylene process. Calcium carbide rocks react with water in the acetylene generator to produce acetylene (C2H2) and calcium hydroxide (lime). The acetylene is next reacted with hydrogen chloride gas to form vinyl chloride over a catalyst surface in the monomer reaction tower. The monomer reaction process unit is outdoors in the open. I detected a few minor leaks of VC monomer at process pumps and valves. However, occupational VC exposure was at a minimum CUSAROSS 02498 R, T. Cheng -3- 3/29/74 because workers spent virtually no time at the monomer manufacturing unit. The calcium carbide process to produce acetylene generates a large quantity of waste calcium hydroxide and causes water pollution problems. Further more, the acetylene process to produce vinyl chloride is less efficient compared to the ethylene process. Therefore, it is China Gulf Plastics Company's intention to phase out the existing carbide-- acetylene---VC process and to depend on its monomer supply mainly from the TVCM Toufen Plant once that plant is in full production. In my fair judgment, the only significant occupational exposure to vinyl chloride occurs at the polymerization plant of Toufen Main Plant. PVC is manufactured at Toufen Main Plant by suspension process. In this technique the reaction is charged first with the required amount of deionized water. Then dispersing agents, buffer, and Initiator are added. After the reactor vessel is sealed and evacuated to remove oxygen, the VC monomer is piped into the reactor. Polymerization is conducted at controlled temperature under vigorous agitation. At completion most of the unreacted monomer is evacuated and recovered. The polymer and water mixture is later centrifuged to separate the polymer from the water. Next the wet polymer cake is air dried to produce PVC powder. There are twelve (12) polymerization reactors at the polymerization plant which is inside a three-story enclosed building. The polymerization plant control room and the tops of the twelve reactor vessels are located on the third floor. Photograph 1 shows a corner of the third floor of the polymerization building. At the end of polymerization reaction and after most of the unreacted VC monomer is evacuated for recovery, the reactor hatch cover is evacuated for recovery. The reactor hatch cover is opened to bleed the reactor. The remaining unreacted and un-evacuated vinyl chloride gas bubbles through the PVC and water slurry and escapes to the third floor of the polymerization building through the opened hatch cover. CUSAROSS 02499 R. T. Cheng 4 3/29/74 PHOTOGRAPH 1 CUSAROSS 02500 R. T. Cheng "5- 3/29/74 This bleeding process takes approximately 30 minutes. During this time, vinyl chloride concentrations (as measured with Century Organic Vapor Analyzer) ranges from 1000 ppm to over 10,000 ppm (1%) at a spot 10 feet away from the opened hatch cover. During the 30 minutes reactor bleeding time wateT in the form of high pressure jet is used to wet and flush down the PVC scales formed on the upper portion of the reactor walls. This water jet washing process takes approximately 2 minutes. Then the reactor content (PVC and water slurry) is pumped out of the reactor to be centrifuged and dehydrated. The bottom manhole of the reactor vessel is opened, and the empty reactor is purged with large amounts of air for 30 minutes. The purging air is supplied with a big air hose. The air blows into the reactor through the opened hatch cover and flushes out through the bottom manhole. The air purging of the reactor lasts for about 30 minutes. During this time, Vinyl chloride concentration at the hatch cover opening drops from 500 ppm to less than 10 ppm. Photograph. 2 shows a reactor in the air purging stage. The reactor hatch cover is open. The larger hose on the left blows air into the reactor vessel while the smaller hose on the right supplies water into the reactor. After the 30 minutes of air purging, three reactor cleaners are sent into the reactor vessel through the bottom manhole. These three reactor cleaners, equipped with hammer, knives and chissels, who usually wear nothing but short drawer, hard hat, and a pair of eye goggles, are to manually clean the PVC deposits and scales off the inside reactor walls. The air purging process is kept going during the entire reactor cleaning period. The air purging serves to reduce the vinyl chloride concentration Inside the reactor and to cool the air temperature in the reactor. During the reactor cleaning period, the workers are exposed to 10 to 20 ppm of vinyl chloride due to the continuous seepage of VC from the PVC scales CUSAROSS 02501 R. T Cheng 6 3/29/74 PHOTOGRAPE 2 CUSAROSS 02502 R. T. Cheng -7- 3/29/74 and reactor walls. It usually takes about 30 minutes for the three reactor cleaners to clean a reactor. Photograph 3 shows two of the three reactor cleaners, with tools in hands and especially fully dressed to pose for the picture. After the reactor is removed of the build-up of PVC scales through the cleaning process, the' bottom manhole is closed and the reactor is ready to reload. Due to shortage of monomer supply, the polymerization unit was operated at less than 50% capacity when I was In Taiwan. On the average, only three reactors were cleaned and reloaded per 8 hour shift during the period of this survey. From the above description of the polymerization process, it is clear that by far the greatest ambient air VC concentrations and the largest personal VC exposure occurs during the 30 minutes of reactor bleeding time (1000 to over 10,000 ppm measured 10 feet away from the reactor hatch cover). The corrective measure is to bleed the reactor vessel without letting the VC vapors enter the polymerization building. The second largest occupational VC exposure is the reactor cleaning process. However, the presence of 10 to 20 ppm of vinyl chloride inside the reactor vessel through seepage is more or less uncontrollable, and it appears that the logical solution is to protect the reactor cleaners with proper clothing and respiratory apparatus to reduce their VC exposures. When the polymerization plant is operated at full capacity, there will be 6 to 8 reactors going through the bleeding, cleaning and reloading procedures during every 8-hour work shift. In other words, almost at every hourly interval the vinyl chloride concentration on the third floor of the polymerization building can go up as high as 10,000 ppm near a"bleeding reactor. Therefore, it is not difficult to believe that the last TLV Standard of 200 ppm for 8 hours exposure can be easily exceeded if workers spend an hour or two of their shift time working out side the control room. CUSAROSS 02503 R. T. Cheng PHOTOGRAPH 3 3/29/74 CUSAROSS 02504 R. T. Cheng -9- 3/29/74 To control vinyl chloride exposure problems due to bleeding of the reactor, I suggested that a special lid for the reactor hatch opening be fabricated. The suggestion was adopted and a hatch opening lid was made a week later. This lid was made in stainless steel and lined with a ring of soft rubber on the bottom surface. The stainless metal and the rubber ring was used for the purpose of eliminating any chance of creating sparks when this lid is placed on the reactor hatch opening. Two short pieces of stainless steel pipe were welded on the lid, and another two pieces of PVC pipe were fitted to the stainless steel pipes to make soft, non-sparking seats for connecting the air and water hoses. Photographs 4A and 4B show top and bottom views of the special hatch opening lid. The operating procedure was that immediately after the reactor hatch cover was opened, this special hatch opening lid was placed on top of the hatch opening. Quickly, air and water hoses were connected to the fittings on the lid. Large amounts of purging air was blown into the reactor and exhausted through a vent pipeline to the outdoors. Photograph 5 shows the special lid seated on top of the hatch opening. Purging air was blown into the reactor through the larger (black) hose on the left, while water can be added to the reactor through the smaller (white) hose on the left. The vent pipeline is controlled by valves which are to be opened before opening of the reactor hatch cover. The vent pipe exhausts to the outdoors of the polymerization building. The adoption of this special hatch opening lid and the related changes in operating procedures eliminated almost the entire 30 minutes of the old reactor bleeding time. As a result, there was a drastic reduction of vinyl chloride concentration in the working area, and at no time would-the VC concentration go as high as 1000 to 10,000 ppm near the reactor hatch opening. However, this special hatch opening lid did. not remain seated on the hatch opening throughout the reactor bleeding time. This lid has to : f !. I I ;cj! CUSAROSS 02505 3/29/74 CUSAROSS 02506 R. T. Cheng -11- 3/29/74 be removed for about 2 minutes so that a worker can use high pressure water jet to wet and flush down the FVC scales formed on the upper portion of the reactor walls. During this 2 minute interval, the worker was exposed to approximately 500 ppm of vinyl chloride while he held the water hose doing the flushing. The idea of an automatic water jet flushing system was discussed with the plant management. If we cannot adopt some means of automatic water jet flushing technique to replace the mannual flushing, then the alternative is to provide this worker with a full-face supplied air respirator during his two minute water flushing operation. Overall, I estimate that, even counting the two minutes of lid opening time for water flushing, the time-weighted average concentration of vinyl chloride on the third floor of the polymerization building have been reduced to less than 5 ppm. Considering that the unit workers spend at least half of their working time inside the enclosed control room, I estimate that the 8 hour time-weighted average exposure should be less than 2.5 ppm. When additional analytical results from charcoal tube and silica gel tube samples are available, I shall be able to make a more accurate estimation of the status of occupational exposure to vinyl chloride at China Gulf Plastics Company. RTC:mm cc: Dr. Dr. Dr, F. D. Gassaway R. L. Gibson W. A. Jones R. T. Cheng CUSAROSS 02507