Document 8yw1ep3Nv9dkmM6gmV27REzK

CHEMICALS INTEROFFICE / LAKE CHARLES JO FROM Distribution Brian O'Rourke DATE SUBJECT November 6, 1991 WTU Vent Compressor The WTU Vent Compressor has recently become an item of concern to several groups because of the number of non-VCM vent trip events generated by this service. The Derivatives Process Engineering Group, Lab/Environmental Group, Derivatives Chief Process Engineer, Derivatives Production Superintendent, and Derivatives Environmental Foreman have all shown an intense interest in this problem. Several meetings have been held to discuss the vent compressor problem and the action plans formulated to solve the problem. This memo serves to document for any interested parties the actions taken to date as well as future plans to address the WTU vent compressor trip problem. This memo also attempts to provide some historical perspective on the WTU Vent Compressor, its intended purpose, and its current performance. HjLfftarig&l Payspgctlye In March, 1979 a stack was added to the WTU Vent Scrubber to reduce the chance of personnel exposure to VDC known to exist in the vent stream. The stack also allowed stack sampling to be more easily performed. In October, 1979 stack sampling at the WTU Vent Scrubber yielded an estimate of 150 - 452 lbs/day (27.4 - 82.5 Tons/year) with > 2000 ppm VCM present in the vent stream. This was deemed an unacceptable level. In December, 1979 the existing three seal loops on the WTU Steam Stripper column, phase separator, and T-l preheater were extended by 8 ft. to introduce a 5 - 6 psig backpressure on the stripper system, thereby increasing the stripper system operating pressure to about 5 psig. The installation of a vent header and K.O. Pot at WTU allowed the vents to be sent to the incinerators. The LD Report (LD-2019) issued in May, 1980 documents this system change. This system existed in some form until September, 1987 when the WTU Vent Compressor system became operational. tie ***! *. I,?* < ** - tarxi ** <1 Prior to stack sampling in October, the WTU Vent Scrubber (67-//f), EIQ 1985, the estimated C1HC emissions Pttf 342 (old EIQ Pt# 79), had been frotsfl estimated at 42 Tons/year in the 1984 EIQ report. After stack sampling in October, 1985, the C1HC emission estimate was estimated as high as 498 Tons/year. The 1985 EIQ report estimate was *e> * *3 & 285 Tons/year. Mechanical repairs to the WTU Vent Scrubber intended to SL 002199 address this problem failed to provide the necessary reduction in the C1HC emissions, yielding only a reduction to 221 Tons/year. Subsequent op rating system changes (sparger modifications and swapping to clean Sabine water instead of stripper feed) also failed to yield significant reductions in C1HC emissions. Additional stack sampling in December, 1985 yielded a revised 1985 EIQ report value of 307 Tons/year for EIQ Pt# 79. A memo to the La. DEQ in January, 1986 promised to deliver a plan of action by May, 1986 to reduce the vents from EIQ Pt# 79 to < 100 Tons/year. The decision was made in April, 1986 to install a vent compressor to collect and compress the vent from the two UTU Steam Stripper Phase Separators and to direct the compressed vent to the Incinerators. Project P-148, Incinerate WTU Vents, was explained to the La. DEQ in June, 1986. This project proposed the installation of the WTU Vent Compressor system. The ACT LC-2460 was approved In January, 1987. The minutes of the ORC Subcommittee meeting held In June, 1987 state that the low suction pressure trip is intended to protect the system from the possibility of the vent compressor sucking air into the vent header and/or creating a vacuum on the stripper column and causing it to fail on vacuum. The ORC recommended prooftesting all shutdown system elements. A Nitrogen regulator was to be installed as a backup to the low suction pressure trip device. The WTU Vent Compressor became operational in September, 1987. The stated purpose of the WTU Vent Compressor was to reduce the C1HC emissions from the WTU Vent Scrubber to less than 100 Tons/year to meet the requirements of the then current NESHAFS permit. The WTU Vent Compressor was defined as a vent control device in a memo dated September 8, 1987. This memo also describes the 4-hour reporting limit set for WTU vent trips out of the incinerator. A spare WTU Vent Compressor was ordered In September, 1988 after it became apparent that one was needed to maintain the 100X on-stream factor the La. DEQ deemed desirable and necessary for a vent control device. ^ Sometime in 1989 the original Atlac 570 K.O. Pot (60-2407) was replaced with h ** ^ a Furan K.O. Pot (60-2581) to which a demister was added. O 4J b System changes and maintenance activities after May, 1990 are documented in .. kthLe-- a. ttachLe* dJmem, o Aby 8n . O'Rourken i n_______1 _ . ida._ted* t*N_o. vemi_ ber 4t , *1a9a91i . HTU Vent Compressor Performance Summary: 1987 - 1991 In 1987, the total down time for the WTU Vent Compressor was 97 hours. The^:***^i *" estimated emissions associated with this down time were Tons. This was' M 3.43 X down time for the 118 day period from 9/4/87 through 12/31/87. b3 In 1988, the total down time for the WTU Vent Compressor was 187.05 hours or v 2.14X. The estimated emissi ns associated with this down time w re SL 002200 S 5.93 Tons. In 1989, the total down time for the WTU Vent Compressor was 136.7 hours or 1.56 X, The estimated emissions associated with this down time were 3.94 Tons. In 1990, the total down time for the system was 144.95 hours or 1.65 X resulting in emissions of 3.76 Tons. The down time year-to-date through September, 1991 for the system was 116.52 hours or 1.78% resulting in emissions of 1.26 Tons. This is a 55% reduction in emissions (tonnage) year-to-date) In September, 1991 an extremely low number of vent trips were reported. Investigation of this low value led to the discovery of a new problem with the WTU Vent Compressor system involving the vent diversion valve FV-1404, This problem is described in more detail in the attached memo from B. O'Rourke dated November 4, 1991. This low figure was an aberration. The October, 1991 performance data indicate only 6 WTU Vent Compressor trips ccurred. This low figure is in part attributable to the inoperative condition of pressure switch PSLL-1403 during.October. This condition existed while waiting on the delivery of a new pressure switch for this service. When the new switch was installed on November 6, 1991, the vent compressor immediately tripped and would not run with the switch in service. This indicates that the vent compressor is creating a vacuum on the stripper system. System Analysis and Design Review Pareto analysis of the WTU Vent Compressor vent trip data for the last 22 months reveals that the principle cause of WTU vent compressor trips is low suction pressure at the compressor inlet. Previous efforts to address this symptom have focused on increasing the vent flow to the compressor through several methods: installing a larger recirculation valve, adding Nitrogen to the compressor suction line manually, manually throttling the bypass valve around the recirculation valve, and increasing preheater steam flow to increase the overhead vent flow. None of these have been completely successful in reducing the incidence of vent trips due to low suction pressure to an acceptable level. Consideration of this problem from another perspective allows that the vent compressor capacity may be too large for the current steam stripper operating conditions in the WTU area. Operation of only one steam stripper at feed rates of 290 to 480 gpm is now the normal situation. The vent compressor was designed to handle a vent flow of 100 cfm associated with maximum feed rates of 1100 gpm. In short, It is now oversized. The vent compressor is a positive displacement, single-stage liquid ring machine. Attempts to reduce the vent compressor's capacity have included: increasing water flow to the compressor inlet and installing larger sheaves on the driven end to effectively slow down the compressor to 1533 rpm. These m asures have not proven terribly effective, yielding only a 15 to 20% capacity reduction. SL 002201 sbj f Uth Judicial Sf!;*''" 0rd*r *o. n-?usct Court Another alternate approach Is to load up the vent compressor with vents from the WTU Settlers and WTU Surge tanks which n w go to a water scrubber (67223) designated as EIQ Pt #348B. Project P-3010 includes this idea within its scope. This EIQ point is estimated to generate 24 Tons/year in C1HC emissions. Without current information on the actual vent flow to the compressor it is n t possible to determine the capacity requirement. An orifice plate will be installed in the compressor suction line to measure the flow to the vent compressor. Field verification of all shutdown system component settings was performed during the design review. Several altered settings were discovered. Changes to all switch settings are being considered to try to configure the system to operate more reliably. A list of system components and shutdown system component settings has been compiled and is attached for reference with PPG Dwg. # 57A-10024. Another suggestion is to provide a secondary control device for this service to handle vents during vent compressor trips instead of the water scrubber (67- ). This system would be a carbon bed vent scrubber. One 55- gal drum of carbon ( lbs) would last for days at the rated maximum vent flow of 100 cfm. The annual average down time of the vent compressor is hours. cc. Jim Rock Buster Thomas Lamar White / Dick Holliday Dave Angell / Andy Plauche / Esther Liggio Charles Parnell F. Ortiz-Cotto or<*er court SL 002202 WTU Vent Compreaaor Syatam Camponante PracMj Alarma _ Syatem Alarms_______________________ Procaaa SatDOint Chart or Scala Input Signal Valua Switch React Point SatDOint Matf^Jfl LAB-1200 PAL-1400 PSH-1401 HA-1900 K.O, Pot High Level Compreaaor Recycle Praaaura Low Discharge Praaaura High Vant Compreaaor Trip Alarm 3 pslg 0-100 X 0-20 "H20 0-15 palg on/off 3-15 palg 4-20 aa contact 4.8 palg 16.8 ma opn 316 SS/Buna 1 5.4 palg 316 SS/Buna Shutdown Svatam Componanta Ta* No. Shutdown Syatem Components Frocuft SatDOint Ooan on Adi. Ranee Setpoint PSH-1404 Suction Praaaura High (50 *H20) 10 "H20 Inc 2.5-45 "H20 FSLL-1403 Suction Praaaura Low Low \ *H20 Dae 0.6-2.5 "H20 teflon ctd polymide/Baatelloy LSHH-1200 K.O. Pot Laval High High 40 X Inc 3-50 paig PSHH-1401 Diacharga Praaaura High High 12 palg Inc 3-50 paig 12.6 pal PDSL/PDSH- 1402 Anti-backup ine open 15 paig-20 "H20 3-50 palg dac open t 9 palg">10 *H20 3-50 paig TSH-1600 Diacharga Tamp. High 160 F normal tamp 137 F, eontaeta open on Inc HS-1901 Emergency Shutdown Button Proci Monltorlna Comoonanta 118 P9.SAg 1*9,___ Svitwa Comoonanta FE-1180 Seal Hatar Flow Senaor FI-1101 FT-1400 PT-1401 80-70216 80-70219 Seal Water Flow Indicator Recycle Praaaura Diacharga Praaaura 11-1600 TE-1600 PI-4-100 PI-4-200 TI-6-200 K.O. Pot Tamp thermowell on K.O. Pot Suction Praaaura Diacharga Praaaura Diacharga Tamp. 0-8 gpm Signet Scientific Modal Ho. MKS15-VO, 1/2* FVDF Senaor with Modal MC509 Indicator 0-10 *H20 0-40/0-250 *H20 Haatalloy C/PDVF 0-15/0-100 paig Haatalloy C/316 SS control t 8 palg/ a/d comp t 15 paig/ on a/u cloaa PV-1405 to acrubbar 2 paig (4.6 paig aignal) 0-200 F 10* long TI thermowell. 10* long. Type "J" teflon-coated, 1.5' fig 0-15 *H20 gauge 0-15 paig gauge 0-250 F, 10* atam SL 002203 CONF1DWT1or(Jer of 14th Ju No. court Control Velvet T Ho.___ SAC No. FV-1181 .3' 80-70220 LV-1200 1* 80-70204 FV-1400 1" 80-70202 FV-1403 2" 80-70201 FV-1401 2' 80-70203 FV-1406 1* 80-70243 LT-120O PDT-1402 80-70216 80-70217 ControlLeri Syatem Component* Soal Watar On/Off Flow Valva 2.3 gpm norm. opan 860 palg, cloaa 80 palg, FC K.O. Pot LCV 3 gpta max. opan 83 palg. cloaa 813 palg, FO Racycl# Praaaura FCV normally eloaad opana to allow flow at approx. 3 "B20, FO.CV-ll, full port 1' normal flow 300 acfh / max flow 5200 sefh Scrubbar Dlvaralon valva 3200 acfh on/Off. FO on air or powar loaa, aolanoid controlled, powar ramovad whan PSH-1404 C 10 "B20, motor dropa out -motor dropa out for for Inc. parmlaalva, hand awltch trip, low auction praaa. PSLL-1403 m 1 *820, high K.O. Pot tamp TSB-1600 C 180 F, high Inc, hdr praaa PSHH-1401 c 12 palg Dlacharga PCV Watar to WTU Vant Scrubber 3331 acfh/3600 acfh 43Z/60X opan, FC.CV-42, full port 2' on/off 30 gpm (4 gpm) cloaa 8 3palg, opan 8 IS palg K.O. Pot Laval Tranamltter Anti-Backup Dlff, Praaa. Tranaaittar Ranaa 0-20/0-230 *820 0-20/0-230 "H20 Haatelloy C/PVDF Haatalloy C/PVDF XlI-ESLi_____ {*9.______ Svatam Coanonanta_____ Range Scale________ Alarm SitPQlnt PIC-1400 PIC-1401 LIC-1200 80-70214 80-70213 80-70213 Recycle Praaaura Dlacharga Praaaura K.O. Pot Laval (0-10 *H20) 3-13 palg 3-13 palg 3-13 palg 0-20 *H20 0-13 palg 0-100 X 3"H20 (4.6 palg falling) 3 *020 12 palg 40 X SL 002204 CONFIDBt^ClMjl ^.ubtect to Proactive otdef of t'lth .tvdicieV&Ls&rict Court No. 91-1145