1
OISD-GDN-224
November 2006
FOR RESTRICTED
CIRCULATION ONLY
MONITORING & CONTROL
OF
VOLATILE ORGANIC COMPOUNDS EMISSION
OISD-GUIDELINES-224
OIL INDUSTRY SAFETY DIRECTORATE
Government of India
Ministry of Petroleum & Natural Gas
OISD-GDN-224
November 2006
FOR RESTRICTED
CIRCULATION ONLY
MONITORING & CONTROL
OF
VOLATILE ORGANIC COMPOUNDS EMISSION
Prepared by:
COMMITTEE ON
“MONITORING AND CONTROL OF
VOLATILE ORGANIC COMPOUNDS EMISSION”
OIL INDUSTRY SAFETY DIRECTORATE
7th FLOOR, “NEW DELHI HOUSE”,
27, BARAKHAMBA ROAD,
NEW DELHI – 110 001
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N O T E
Oil Industry Safety Directorate (OISD) publications are prepared for use in the Oil and Gas Industry under the Ministry of Petroleum and Natural Gas. These are the property of Ministry of Petroleum and Natural Gas and shall not be reproduced or copied or loaned or exhibited to others without written consent from OISD.
Though every effort has been made to ensure the accuracy and reliability of data contained in these documents, OISD hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use.
These documents are intended only to supplement rather than replace the prevailing statutory requirements.
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FOREWORD
The Oil Industry in India is about 100 years old. As such, a variety of practices have been in vogue because of collaboration/association with different foreign companies and governments. Standardisation in design philosophies, operating and maintenance practices was hardly in existence at a national level. This, coupled with feedback from some serious accidents that occurred in the recent past in India and abroad, emphasised the need for the industry to review the existing state-of-the-art in designing, operating and maintaining oil and gas installations.
With this in view, the Ministry of Petroleum and Natural Gas in 1986 constituted Safety Council assisted by the Oil Industry Safety Directorate (OISD) for formulating and implementing a series of self-regulatory measures aimed at removing obsolescence, standardising and upgrading the existing standards to ensure safer operations & also develop standards in new area identified. Accordingly OISD constituted a number of functional committees comprising of experts nominated from the industry to draw up standards and guidelines on various subjects.
At every stage of production, processing, handling, transfer and distribution of hydrocarbon based products, there is potential for losses to the environment. Volatile Organic Compounds (VOCs) being high in vapour pressures significantly vapourise and participate in atmospheric photochemical reactions with oxides of nitrogen and sunlight to form ozone. Ground level ozone affects normal function of the lung in healthy humans. For this reason controlling of VOCs is an effective method of minimizing ground level ozone.
The present document “Monitoring and Control of Volatile Organic Compounds (VOCs) Emission ” was prepared by the Functional Committee on “VOC Emission control”. This document was prepared based on the accumulated experience and knowledge of industry members and various national & international codes and practices.
This document will be reviewed periodically for improvement based on the new experiences and better understanding. Suggestions may be addressed to:
The Coordinator
Committee on "Monitoring and Control of Volatile Organic Compounds (VOCs) Emission”
Oil Industry Safety Directorate
7th Floor, New Delhi House
27, Barakhamba Road,
NEW DELHI - 110 001.
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FUNCTIONAL COMMITTEE
NAME
/ORGANISATION
LEADER
Shri M.K.Dutta
/ Centre for High Technology, New DelhiMEMBERS
Shri A.K. Sharma
/ GAIL (India) Limited, PataDr.P.S.Viswanathan
/ Kochi Refineries Limited, KochiShri D.V.Dixit
/ Engineers India Limited, New Delhi.Shri A.D. Vyawhare
/ Bharat Petroleum Corporation Limited. MumbaiDr. M.S.R. Swami
/ Chennai Petroleum Corporation Limited, ChennaiShri P. Sitarama Rao
/ Hindustan Petroleum Corporation Limited, VizagShri Harendra Singh
/ Oil & Natural Gas Corporation Limited, MumbaiShri S.Dasgupta
/ Indian Oil corporation Limited, New DelhiMEMBER COORDINATOR
Shri P. Kulshreshtha
/Oil Industry Safety Directorate, New Delhi.
In addition to above, several other experts from industry contributed in the preparation, review
and finalisation of this document.
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INDEXSECTION / DESCRIPTION / PAGE NO.
1.0 / Introduction / 1
2.0 / Scope / 1
3.0 / Definitions / 2
4.0 / Sources of Emissions / 3
5.0 / Estimation of Emissions / 6
7.0 / Prevention & Control of Emissions / 7
7.0 / Control of Emissions – By LDAR / 8
8.0 / Emission Prevention through In-built Features / 11
9.0 / Recommended Practices / 12
10.0 / References / 13
ANNEXURES
I / Estimation of emission from fixed roof tank / 14
II / Estimation of emission from floating roof tank / 17
III / Steps in Brief on US EPA Method 21 for monitoring fugitive emissions / 19
IV / Sample Calculation for Fugitive Emission Monitoring using Emission Rate Correlation Equation / 21
V / A Brief on Vapour Recovery systems / 22
VI / Sample calculation for emissions from loading operations / 25
VII / Typical Format for Fugitive Emission (Leak) Survey / 26
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1
Monitoring and Control of
Volatile Organic Compounds Emission
1
1
1.0Introduction
Emission of Volatile Organic Compounds (VOC) is an area of significant concern. Refineries & gas processing plants are major contributors. Apart from causing production loss, VOCs are partly responsible for ground-level ozone, which may affect normal functioning of lungs. Many VOCs are toxic, causing illnesses such as cancer, neurological and respiratory diseases.
VOCs are present in crude oil and the produced petroleum fractions viz. LPG, motor spirit, kerosene, naphtha, benzene, hexane, cyclohexane, fuel gas etc. Volatile hydrocarbon vapours get released to atmosphere from storage, pumping, loading / unloading and processing of crude & petroleum products. However, fugitive emission (leakage to atmosphere) of VOCs usually occurs through seals of equipment, wastewater collection & treatment facilities, cold vents, leakages etc. Actions taken in recent years have shown substantial reduction in VOC emission.
These guidelines include identification of fugitive emission sources alongwith quantification and control techniques through design measures, inspection, repair & maintenance schedules, administrative actions, reporting and record keeping in a systematic manner.
2.0Scope
This document lays down guidelines applicable for refineries and gas processing plants, for identification and control of fugitive VOC emissions.
3.0Definitions
3.1Volatile Organic Compounds (VOC):
These are the organic compounds whose vapour pressure at 20oC exceeds 1.0 kPa (0.145 psi). As a result, these can easily become vapour or gas from the solid or liquid state.
3.2Component:
Equipment or accessories which include pump seals, compressor seals, seal oil degassing vents, flanges of heat exchangers, pipeline valves, flanges and other connections, pressure relief devices, process drains, open-ended pipes, sampling connections etc. that could potentially leak to emit VOCs into the atmosphere.
3.3Fugitive emissions:
Also known as “equipment leaks”, the fugitive emissions are the result of leaks of volatile organic compounds from components as above including the hydrocarbon transfer lines and associated equipment. Valves are usually the single largest source of fugitive emissions.
3.4Background Concentration level:
It is the concentration of VOC measured through the portable hydrocarbon detection instrument which is taken upwind (atleast three metres) from any component to be inspected (e.g. pump or compressor) so that it is unaffected by any specific emission point.
3.5Essential Equipment:
Any equipment in the process whose outage from service will cause cut in unit throughput by > 33%.
3.6Leak:
Gaseous hydrocarbon emission found to be in excess of 10,000 ppm above background concentration level, when measured by a portable hydrocarbon detector at a distance of one (1) centimeter from the surface of potential source with the instrument calibrated with methane. However, in case of Benzene, which is highly carcinogenic, the leak is defined as the emission value measured in excess of 3000 ppm above the background concentration level.
Regardless of concentration, a leak is also identified by sight, sound or smell at a component caused by liquid dripping or vapour leak, which is sometimes visible through bubbles in presence of soap solution. The dripping of liquid VOCs at a rate of more than three (3) drops per minutes can be construed as leak.
3.7Reference compound :
This is VOC used for instrument calibration.
3.8Emission Control System:
It is a combination of capture system(s) and control equipment used to recover, reduce, remove or control the release of VOC to atmosphere. Such equipment includes vapour recovery system, compressor, incineration system, flare system, process heaters etc.
3.9Leak Detection And Repair (LDAR) :
It is a tracking programme to ensure that all components are monitored on regular basis and repaired in timely manner to reduce/eliminate VOC emissions from leaking components.
3.10Response Factors (RF):
Response factor is required to provide an accurate relationship while using an analyzer calibrated for one gas to measure leaks of other compounds. The response factor is defined as Concentration in actual = RF x Concentration measured. A response factor of 1.0 means the instrument reads out identical to actual concentration of chemical in the gas sample.
3.11Emissions:
“VOC Emissions” shall hereinafter be expressed as “Emissions” in this document.
4.0Sources of EMISSIONS:
In oil and gas installations, probable sources of emissions are as follows:
- Process Vents, which are mostly controlled.
- Fugitive releases of hydrocarbon vapour caused by leaks in process equipment or evaporation from open areas. These are the major source of emission,which include:
- Evaporative emission sources viz hydrocarbon storage & transfer facility (loading/ unloading), wastewater transfer & treatment facility, cooling tower, waste management area e.g. oily sludge lagoons, sludge pits, etc.
- Process Equipment Emission Sources viz pumps, valves (from gland, bonnets etc.), compressors, pressure relief valves, connectors and flanges, agitators, open ended lines, sampling connections.
4.1Emissions from Storage tanks:
Emissions from fixed roof storage tank include standing losses and working losses. Standing losses occur due to variation in ambient temperature (thermal breathing). Working losses occur during filling operation.
Emissions from floating roof tanks include standing losses and withdrawal losses. The standing losses occur from roof rim seals, deck fittings, deck seams, still wells etc. The withdrawal losses pertain to evaporation loss of liquid stock that clings to the shell, guide pole etc while the stock is being pumped out.
Emissions from Pressurised storage tanks (e.g. dome roof tanks or nitrogen blanketed fixed roof tanks) occur when their safety valves / controlled vents discharge to atmosphere. Similarly, emissions from the other pressurized storages (e.g. spheres & bullets) occur when their safety valves/ controlled vents discharge to atmosphere. In order to minimize these discharges to atmosphere, safety valves / vents of horton spheres and bullets should normally be connected to flare header.
4.2Emissions from Loading facilities:
Emission is significant during filling of road tankers and rail wagons in case of lighter products like naphtha/gasoline.
4.3Emissions from Effluent Treatment Facilities:
Drainage routing from process units, storage tanks, loading areas etc. to the Effluent Treatment Plant (ETP) through Oily Water Sewer (OWS) involve considerable emission from the open inlet chamber of ETP, API oil separator, other open storages etc. depending upon the oil content in the influent streams and the temperature.
Recommended system for reduction of emission from wastewater treatment is to have a closed system for contaminated and odorous wastewater stream with provision of water seals on sewers & drains and gas tight covers on junction boxes.
4.4Emissions from Cooling Towers:
Cooling towers, under normal circumstances, do not contribute to emissions. However, leakages in the water cooled exchangers can lead to hydrocarbon carryover to cooling towers resulting in emissions. Hydrocarbon detectors should be provided at cooling tower return stream from units.
4.5Emissions from Oily Sludge:
The main sources of generation of oily sludge are tank cleaning, ETP, oil catchers, API separators, and spillages from bitumen plant, crude oil and product storage tanks. For API separators and oil catchers, oil content and temperature have major effect on emission. Sludge removed from these sources and stored in open pits, contributes to emissions in significant quantity. Oil should be removed from the oily sludge before disposal. The residual sludge should not have hydrocarbon content more than 10% v/v.
4.6Emissions from Process Units:
In process units, VOC emissions can occur through leaks, vents, drains, flanged joints, instrument connections, PSVs open to atmosphere, pump seals, compressor seals, valve gland/ bonnet, sample connections etc. These should be minimised through an effective LDAR programme. Significant amount of emission can also occur while preparing the equipment / vessels for handing over to maintenance for repairs or during start up/ emergency shut down of the unit. Such emissions should be minimised by adopting standard operational practices of emptying out the equipment/vessel completely into close blowdown system for reprocessing instead of routing to ETP via Oily Water Sewer.
5.0Estimation of emissions
Estimation of emissions from storage tanks, loading facility and equipment leaks can be done as described below:
5.1Estimation of emissions from storage
Fixed Roof Tanks: Working losses for the fixed roof tanks are estimated on the basis of tank filling rate. Standing losses from the fixed roof tanks are estimated based on thermal breathing from the tank. See Annexure-I for guideline to estimate annual average emission loss of VOCs from a fixed roof tank.
Floating Roof Tanks: The method to determine annual average emission loss of VOCs from internal/ external floating roof tanks is provided at Annexure-II.
Pressurised storage tanks and vessels: Annual average emission loss of VOCs for low-pressure storage tanks (upto 2.5 psig) can be estimated based on method provided at Annexure-I. For high-pressure storage tanks (2.5 to 15 psig) and vessels, the atmospheric emissions are considered insignificant with proper maintenance measures in place.
5.2Estimation of emissions from loading facilities:
Estimation of emissions from loading gantries is done on the basis of loading flow rates and the concentration of the vapours emitted from the vent nozzle of the tanker/ wagons. Typical parameters, which should be collected for estimating emissions from loading gantries, include Product information (i.e. name, vapour pressure, density, composition, molecular weight of vapour), number of loading points, flow rate per loading point and concentration of vapour being emitted to atmosphere.
Emission rate from loading gantry can be estimated using the following equation (valid for bottom loading / top submerged loading):
- Emissions from loading operation of Petroleum Liquids : (Reference AP-42 of EPA Chapter 5.2 )
LL = 12.46 SPM / T
Where,
LL = Loading loss, lb per 1000 gal of liquid loaded
S = A saturation factor
P = True vapour pressure of liquid loaded in psia
M = Molecular weight of vapours , lb/lb-mole
T = Temperature of bulk liquid loaded, 0R ( 0F + 460).
- Sample calculation is given in annexure VI.
5.3Estimation of emissions from Equipment Leak
Emissions due to equipment leak (i.e. valves, flanges, other connections, pumps, compressors etc) should be estimated using US EPA Method 21. Procedural steps in brief alongwith a typical example calculation are illustrated in Annexure-III and Annexure-IV respectively. The instrument used for detection of VOC leakage should be able to detect VOC concentrations in parts per million volume (ppmv) and % LEL in line with leak definition concentration. The instrument must be intrinsically safe for use in the hazardous area of the processunits. Typical specification of the instrument as per EPA Referencemethod 21 are given at Annexure-III.
6.0Prevention & control OF EMISSIONS
Two primary techniques of equipment leak emission control are:
- Equipment modification for Emission Prevention (on case to case basis, such as replacing standard valve with seal less type).
- Implementing a regular and structured leak detection and repair programme (LDAR) for Emission Control.
Equipment reliability improvement is recommended on following lines:
i)Valves: Use of better quality of packing, proper engineering specifications, use of special type of valves e.g. bellow type.
ii)Flanges: minimization of flange connections in number, proper rating & gasket material.
iii)Pumps: Provision of double mechanical seals, other high performance seals etc. Compressors: Connecting the packing vent of reciprocating compressor preferably to the flare system. Use of seals permitting minimum gas leakage, other high performance seals, collection and safe routing to Emission Control system.
iv)Safety Valves: Connecting to flare.
v)Wastewater Treatment: Covered processing and storage, pre-treatment for toxics.
vi)Storage: Proper type of storage and Seals, inclusion of Vapour recovery system for fixed roof tanks.
vii)Loading: Installing vapour recovery system (See Annexure-V for information on typical VRS).
viii)Route the flushing from sampling points preferably to Closed Blowdown system.
7.0Control of emissions - BY LDAR
LDAR programme should be implemented in three phases:
Components identification to determine which of them requires to be monitored, the same to be tagged by using weatherproof tags. Components may be identified from P&ids and Unit inspection. Process streams should be followed in logical order to identify all potential leak sources.
7.1Monitoring potential fugitive emission sources for leaks and tagging the detected leaking components.
7.2Repair or replacement of leaking component—first attempt at repair of component within 5 days of leak detection and final repair within 15 days. If the leaking component is essentially required for sustaining the process operations and cannot be repaired within 15 days after detection, one of the following actions should follow:
i.Replace the leaking component and inspect for leaks within 5 days after detection.
ii.Vent out emissions to vapour recovery system operating at 95% efficiency (min) or to a flare.
iii.Plan for repair/replacement of the essential component in the next shutdown of the process unit but within a reasonable time as per management’s decision( say, one year from the date of the original leak). It should be accordingly marked/tagged distinctly. Similarly, a component which is not getting isolated for repair, should be tagged and short-listed for action in next shutdown.
iv.After repair is done, the component should be re-tested within 15 days for the residual leak assessment.
A cost effective LDAR programme should be developed by focusing attention to locate very high leaking points and repair them on priority.