Document zQBKzNegYEkKD1XVONpz7apv7

ABD00317431 _ WASHINGTON. D.C. ' ,50 l >i t * 141980 */ OF PICE OF AIR, NOISE, ANO RA01A710N SUBJECT: Vinyl Chloride^Standard - Safety Relief Valve Discharges FROM: Assistant Administrator -for Air, Noise, and Radiation V TO; , Rebecca Manner, Regional Administrator Region IV This is in regard to John White's request in the December Senior Management Report.for better guidance on control of vinyl chloride ' emissions from safety relief valve discharges. I understand that the regional offices in general have had difficulties in enforcing section 61.65(a) of the vinyl chloride standard which-dcals with relief valve discharges. I also understand that the number..of relief valve discharges ------reported during the enforcement of the standard has been greater than may have been expected. This concerns .me because of the large amount of emissions which can occur during one of .these .discharges. The vinyl chloride standardjs scheduled for review in 1931, five, years from the original promulgation date. We*are already beginning to develop-a work plan for review .of that standard. During the review of --the standard, my staff plans to. focus on the part of the regulation dealing with relief valve discharges. An effort will be mads to identify any new developments in technology for control of these discharges. Also, iny staff will contact the offices and obtain data on the frequency and causes of relief valve discharges which have occurred and evaluate alternative ways of writing this part of the standard to improve its * clarity and effectiveness. The following paragraphs provide information on the development of the regulation for relief valve discharges and guidance on the interpretation of it. " Section 61.65(a) of the vinyl chloride standard states that "Except for an emergency relief discharge, there is to be no discharge to the atmosphere from any relief valve on any equipment in vinyl chloride service." An emergency relief discharge is defined as "a discharge which could not have been'avoided by taking measures to prevent the discharge." Although the regulation covers any relief valve on any equipment .that contains at least 10 percent vinyl chloride,, and is located .in a ABD00317432 (4 . -1 ,,. | . .j v.;.j CiTiori^ plant, the primary Intent of roo-* uion was to substantially re* ae the number of relief valve disw..drges from polyvinyl chloride reactors. At the time the regu v/as being developed, relief valve discharges from polyvinyl chlori reactors were a common occurrence and we v/ere aware of specific me that could be implemented to prevent these discharges. Relief val discharges from other equipment occurred much l**ss frequently and i did not include, in our background documents specific information 01 they can be prevented. They v/ere included in the regulation, howev to ensure that emissions from these relief valves did not occur unnecessarily. Our intention v/as that primary attention be focused on the polyvinyl chloride reactor discharges which are the largest source*of emissions and for which we had described specific prevent measures. ' * j 1 The information we obtained during the development of the stanc indicated that the frequency of relief valve discharges from polyvir chloride reactors varies considerably from plant to plant. Some pie had less than one discharge per year; others had twenty or more. On , the average, 5000.pounds of vinyl chloride was emitted .from one of t . ! .discharges within a five to ten min.u. te .period. . * . # __ Ralief-va-Tve'cHscha'rges from polyvinyl chloride reactors occur in order to prevent catastrophic rupture when pressure within the reactor builds up beyond the capabilities of the reactor to contain it. The production of polyvinyl chloride from vinyl chloride in reactors #is an exothermic.reaction. Reactors are equipped with agita and cooling jackets to remove the heat due to the exothermic reaction Pressure buildups in reactors can occur if the cooling equipment does operate properly; this can happen if there is a power outage for exam; It can also occur if the operator adds too much vinyl chloride or somi other ingredient to the reactor during formulation of a batch. In order to prevent discharges, several steps can be taken. For example, reactors can be equipped with temperature or pressure sensing devices. When high temperature or'prcssurc is detected, chemicals can be manually or automatically added to the reactor to stop the reaction Provisions can be made to remove enough of the contents of a reactor batch to another vessel so that the pressure is broughfback down to a satisfactory level before.it is necessary for the relief valve to discharge. Back-up power sources can also be provided to keep agitato* operating during main power outages. Soma of the newer plants contain computerized systems which automatically fill reactors with the proper quantity of each ingredient and which contain provisions for altering operations when overpressure is detected. Newer plants with computer ized systems tend to have fewer discharges. These are several examples of preventive measures which had been demonstrated in existing plants a the time of development of the standard. ABD00317433 Wot all relief valve discharges can be prevented. The intent of 1 the regulation v/as that if_a plant took steps such as those named above and still had a relief valve discharge, that relief valve discharge v/ould be considered an emergency condition and would not be a violation. We expected such situations to be rare. V/e did not specifically require that each plant take all of the preventive measures described above for a couple of reasons. First, some plants were haying very-few discharges (less than one per year) already without taking all of the above named steps/ It did not appear prudent-to require plants to unnecessarily install expensive equipment when they were preventing the discharges without it. There#v/ere wide variations among plants. Some contained numerous older, smaller reactors, while others contained large, more, modern reactors. Relief valve discharges are much more easily controlled from the newer and larger reactors than from the older and smaller reactors. In addition, * v/e did not v/ant to preclude the development of improved technology which may be even more successful in preventing discharges than the technology available at the time v/e developed the. regulation. * The intention of the regulation v/as that each plant install sufficient preventive equipment to reduce the number of polyvinyl chloride reactor discharges to a very small number. For-plants who report essentially no discharges, no additional equipment v/ould be required. # However, for plants who do report discharges, more and more _ preventive measures v/ould be required through enforcement actions until ' the'occurrence of discharges frpm any one plant is rare. I hope this, information is useful to you. If you have additional questions, comments,' or suggestions, please contact me.