Optimility Of Water Resources Utilization Network In Petrochemical Industry

The integral level of water resource utilization and waste minimization of China petrochemical industry is lower than that of developed country. Water consumption to refine one ton petroleum in our country is 1.08t/t that is 2 times of 0.5t/t of developed countries. The petrochemical industry of China has enormous capacity to save water.The dissertation supported by planned scientific programs of Shanghai Science and Technology Committee ( Grant No.042312081 ) applied water system optimization concept to petrochemical industry. Water-using network optimization in petrochemical industry includes analysis of water conditions, method of optimizing and effect which are all shown in the dissertation. The main achievement is mentioned as below.(1) Water utilization and wastewater discharge were analyzed systemically in a large petrochemical enterprise. The supply system consists of fresh water system, fire-fighting system and cycle-cooling system. Water was used as cooling water, producing water and steam water. Discharging system includes sulfur and oil contained systems. Sulfur and oil water system are established for optimizing.(2) The propose and steps of water reuse were analyzed. Many methods and the principle of water reuse were set. Sulfur, oil, ammonia and COD should be considered when designing network in which water containing sulfur and oil was reused directly.(3) Feasibility analysis of water reuse was made. The water reusing standard was fixed and the effect of concentrated wastewater was discussed. The database of water parameters was built and the factors which can ensure the project were analyzed to support the water reuse,(4) A matching method of water-using network optimizing was built: 1) The matching thread was set: to maximize the mass load of water in the whole system. The water currents were assorted into fresh, low-contaminant and high-contaminant kinds. Then they were matched to the operations by concerning the inlet limit condition of the operation. The ratio of the actual and limit inlet flowrates should be inclined to 1. And the operations should be ordered by the outlet contaminant concentration from low to high. 2) In water network with multiple contaminants, the key contaminant should be fixed first. Then some illogical calculation results should be abandoned. In the same time, the operations should be orderd by the product of outlet contaminants. 3) The alterations of the conditions can be concerned by amending certain parameters such as the flowrate and contaminant concentration in certain steps. The alteration of flowrate should be moved to the inlet or outlet of the operation. And the contaminant concentration could be directly sent into the database without cauculating. Regeneration operation should not only influence the contaminant concentration, but also influence the whole structor of the network. The network should be altered real-time with the online monitors. In case the network is fixed, the water distribution should be altered. 4) Distributed network which represents majority of real water using-networks was optimized. The operations were divided; the outlet water streams were assorted into fresh, low-contaminant and high-contaminant kinds, and then matched to the inlet streams by concerning the inlet limit condition of it. The actual inlet concentration should be inclined to the limit one. When there comes to be multiple contaminants, a key contaminant was chosen by each inlet stream, the flowrate ratio was fixed on base of it and the proper reused water streams were applied. The costs were concerned to abandon the water streams in the actual designing.(5) Water system was optimized and water chain was built in the enterprise with matching optimization method: 1) The water systems with sulfer and oil were optimized. In water system containing sulfur the fresh water reduction was 38.31% and 19.98% respectively on the conditions of single contaminant and 17.81% on the condition of double contaminants. The water system containing oil with flowrate alteration was optimized and the fresh water reduction was 33.67%. The regeneration operation was added, if only for reuse the fresh water and wastewater reductions were increased by 1.1% and 1.4%. And they were increased to 63.11% and 76.05% when the regeneration operation was used to recycle the water of the whole system. 2) The real distributed network was set. After optimization, the fresh water consumption for desalter, water seal and cooling was reduced from 199.62t/h to 11.59 t/h, and 188.03t/h recycle water became the substitute. 3) Water system industry chain was built by integrated optimization of the whole water system in the enterprise. the fresh water consumption refining one ton petroleum was reduced from 1.03t/t to 0.53 t/t and the water discharge from 0.53t/t to 0.028 t/t.