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1 Page : 1 of 28 Project Engineering Standard KLM Technology #03-12 Block Aronia, Jalan Sri Perkasa 2 Taman Tampoi Utama Johor Bahru Malaysia TABLE OF CONTENT 1.0 INTRODUCTION SCOPE CLASSIFICATION OF BLOWDOWN STREAMS Classification Based on Composition Classification Based on Temperature Classification Based on Volatility and Viscosity SAFE HANDLING Aqueous Blowdown Hydrocarbon Blowdown Emergency Blowdown Chemical Blowdown DISPOSAL OF BLOWDOWN Closed Pressured System Sewer Drain System Type of Sewers Basic Design Guidelines for Oily-Water Sewers Special Sewers REFERENCES 17

2 Page 2 of INTRODUCTION Blowdown as defined in this document is a liquid stream containing water, oil, chemicals or a combination of two or more of these which are required to be drained from various process equipment in the hydrocarbon industry under different operating situations like start-up, shutdown, normal operation or emergencies. Since majority of these streams are usually waste products (however in some situations these may be recoverable). Their handling and disposal often gets a low profile in the plant design and operation. However, the importance of handling these blowdown streams in enhancing the safety of the plant cannot be underestimated. The purpose of this document is to recognize the various blowdown streams commonly encountered in the oil and gas industry and give guidelines for the safe handling and disposal of some typical streams. 2.0 SCOPE This document covers the guidelines on design and operating philosophies for safe handling and disposal of liquid blowdown and drains from various process equipment in the petroleum and natural gas processing and storage facilities.

3 Page 3 of CLASSIFICATION OF BLOWDOWN STREAMS Before dealing with the design and operating practices for handling and disposal of blowdown, it is necessary to recognize the various blowdown streams generally handled in the petroleum industry. Based on the nature, frequency and other characteristics, these streams can be classified as below: 3.1 Classification Based on Composition Depending on the composition of blowdown streams, these may be classified as: Aqueous Blowdown: These streams contain water as the major constituent with small amounts of hydrocarbons. Such streams are usually encountered during the normal running of the units. These streams may be continuous or intermittent in nature. Some typical examples are: Water draw-off from reflux drums Water-caustic (or other solvents) draw-off from treating units Brine water draw-off from desalters and heater treaters Water draw-off from oil separators Stripped water draw-off from sour water strippers Water draw-off from crude oil tanks and other product tanks Boiler blowdown Hydrocarbon Blowdown These streams contain mainly the hydrocarbon fractions and may be encountered during normal operation, start-up, normal shutdown and emergency shutdown. These streams are usually intermittent in nature. Some typical examples are: Intermittent draining of process equipment during normal operation. Drains and vents / bleeders on pumps, pipelines, and manifolds Sampling of products from equipment and piping Emptying of an equipment during planned shutdown Emergency draining of process equipment like furnace, tower or vessel etc. Coker plant blowdown

4 Page 4 of Chemical Blowdown These streams contain aqueous solutions of chemicals and may have small quantities of hydrocarbons. Such streams may be continuous or intermittent in nature. Some typical examples are: Caustic drains from treating plants Reactor washes Effluent from water treatment plants Water draw-off from sour water strippers which may contain sulphides, H 2 S, phenols, etc. Cooling Water blowdowns. 3.2 Classification Based on Temperature Blowdown streams as classified above may further be grouped depending on the temperature. These streams may be hot at ambient temperature or be under cryogenic conditions. The hazards involved in handling them and the technique of handling and disposal of each one of such streams may be different. Some typical examples of such streams are: Hot Blowdown Furnace blowdown Coker plant blowdown Fractionating tower blowdown Hot heat exchanger / reboiler blowdown Samples of hot products Vents / drains from hot equipment Boiler blowdown-continuous and intermittent Cryogenic Blowdown Drains, vents and bleeders on equipment operating at sub-zero temperatures like cold boxes, refrigeration systems, etc. Drains, vents, bleeders on flashing liquids Drains, vents and bleeders on high pressure gas transmission lines.

5 Page 5 of Classification Based on Volatility and Viscosity Based on relative volatility, the blowdown streams may be classified as volatile or non-volatile. Similarly, they may be viscous and congealing type or the free flowing type blowdown streams. Some typical examples are: Volatile Gas condensates LPG Gasoline and lighter naphtha s Hot-heavy hydrocarbons above their flash points Non-Volatile Kerosene s and heavier hydrocarbons below their flash points Viscous / Congealing Crude Oil Reduced Crude Oil Fuel Oil Bitumen Wax

6 Page 6 of SAFE HANDLING The facilities and procedures of safe handling of various blowdown streams will vary with the type of general grouping of these streams as listed earlier. Depending upon the type of blowdown, some typical handling facilities are recommended as under: 4.1 Aqueous Blowdown Generally these blowdown streams consist of water with small amounts of hydrocarbons. Depending upon whether these streams are continuous or intermittent and the nature of hydrocarbons associated with them, the handling arrangements will vary as described in some typical examples below: Aqueous Blowdown Continuous in Nature All aqueous blowdown streams from pressure vessels and which are continuous in nature shall be provided with an automatic level indicator cum controller. In addition, high and low level alarms shall be provided in the concerned control room. Further, since majority of such services will be subject to corrosive and or dirty environment due to presence of large quantities of water, the level control valve should be provided with properly sized block and bypass valves for easy maintenance of the control valve. A typical scheme for handling such streams is depicted in Fig. 1a. If the turned down ration of liquid blowdown is very wide as is the case very often in oily-water is very wide as is the case very often in oilywater separators in oil fields, a multiple control valve assembly may be provided to take care of the wide arrange of flow rates. However, if the continuous aqueous blowdown is form a vessel operating at atmospheric pressure, automatic level indicator-cum-controller may not be necessary. Instead, a U-seal with a siphon breaker can be provided. Water draining from Barometric condenser drums and water seal vessels in flare headers are some typical examples of this arrangement. Refer Fig. 1b for typical arrangement of such a scheme. All such blowdown streams consisting of mainly water from vessels which contain non-volatile hydrocarbons (which would not flash at ambient temperature) can be disposed of to the sewer. However, if blowdown stream consists of water from vessels, which contain volatile liquids like naphtha s and lighter fractions, the same should be handled as discussed under below.