Analytical estimation of the water regime of the oil refinery boiler plants

Abstract

Petroleum refineries are complex systems of multiple operations that depend on the type of crude refined and the range of desired oil products such as petrol, diesel, fuel oils, lubricating oils and asphalts. Many of the processes in a refinery use water, however, not each process needs raw or treated water, and water can be cascaded or reuse in many places. The modern refinery operation is associated with a significant consumption of thermal energy, which is supplied to oil processing units with low, medium and high pressure water steam generated at the enterprise's boiler plants. A reliable boilers΄ operation  depends on the quality of the raw water, on the correct setting of boilers΄ blowdowns, and the quality and volume of discharges affect the operation of the sewage system and waste water treatment plant. A portion of the boiler feedwater and condensate that is fed to the boilers in the refinery is purged from the system to maintain the dissolved solids level in the system at the acceptable level. Understanding water balance for a boiler houses is an important step towards optimizing of water usage, recycle and reuse. Therefore, the article assesses the qualitative and quantitative characteristics of water streams of boiler houses for compliance with the requirements of process regulations and compliance with current regulations governing the boilers’ operation and related to waste water drainage within the refinery. Based on the data of analytical and production control of the boilers’ technological process the authors of the article have developed recommendations for the rational water resources usage of the boiler houses integrated into the general technological processing cycle of oil and oil products. The recommendations can be categorized as follows:

-         to foresee boilers’ blowdown water accumulation and mixing it with conventionally clean effluents (for example, polypropylene unit wastewater, water cooling towers blowdowns, revers osmoses concentrate etc.). Depending on total contamination level, the mixture can be discharged directly to the water body or used for refinery’s own needs (for example, to coke hydrocutting system make-up of delayed coking unit; to use as raw water for distillation or reverse osmoses units);

-         to minimize the blowdown water volume considering of continuous monitoring of boiler water quality. Periodic blowdown should be done only when the qualitative characteristics of the boiler water approach the critical values specified in the regulatory documents;

-         to harmonize the feed water and boiler water internal standarts with the requirements of the standard EN 12952-12: 2003 / GOST 55682.12.

Taking into account the significant amount of water consumed by boiler plants in the balance of the refinery, the implementation of the proposed measures saves considerable material resources at the wastewater stage using the boiler blowdown for the refineries’ own needs and results in improvement of economic and environmental activities of the enterprise.