In this paper, the production of the ethylene plant at PetroChina Sichuan Petrochemical Company Limited, which takes hydrogenated C₄ as the cracking raw materials, is introduced. Through the composition analysis of the hydrogenated C₄, the hydrogenation process route is selected and the control parameters are optimized, so as to obtain high quality cracking raw materials. The optimum combination of production process parameters is determined through the exploration of cracking control parameters, so as to realize the considerable economic value of hydrogenated C₄ as cracking raw materials.

There are 63 spherical tanks in the tank farm of the Olefin Plant of PetroChina Dushanzi Petrochemical Company. The minimum volume of single spherical tank is 400 cubic meters, and the maximum volume of single spherical tank is 5 000 cubic meters. Spherical tank belongs to pressure vessel, so periodical inspection must be carried out in accordance with TSG R7001 Pressure Vessel Periodical Inspection Regulation, and the inspection cycle depends on the safety grade, generally 1 to 6 years. To carry out pressure vessel inspection without shutdown of the ethylene plant, the inspection of the spherical tanks is performed separately within the inspection cycle while satisfying the production needs, i.e. 10 spherical tanks each year calculated by the longest cycle of 6 years. Pressure vessel inspection construction includes the erection of internal and external scaffolding, the weld grinding of storage tank, the inspection of spherical tank and the four levels of high-risk operation for spherical tank inspection. To keep the process safety under control, it is necessary to develop standards from the aspects of construction force arrangement, material entry into the plant, standardized erection of scaffolding and weld grinding quality, perform well the standardized actions and reduce the errors in optional actions.

Flare system is a safety measure for the emergency shutdown of ethylene plant, and its design is very important. Adopting necessary emission reduction measures is helpful to reduce the total load of flare system. This paper introduces the emission reduction measures adopted in ethylene plant, and analyzes the principle of flare control, the setting of pressure control valve, the emission reduction of flare gas in compressor system, the emission reduction of flare in distillation tower system, and the design and calculation basis of flare system. By taking certain emission reduction measures, the investment of ethylene plant can be further reduced on the premise of ensuring safety, thus improving its market competitiveness.

The C₃ hydrogenation cooler (E-5211) of an ethylene plant was put into operation after the overhaul in May 2015. After 18 months of operation, the tube bundle leaked, so the plant was forced to change the process flow, and the MD and PE could not be hydrogenated to propylene as normal, leading to the loss of a large amount of C₃ components and the decrease in propylene production, and seriously affecting the economic benefits of the plant. In view of the leakage of the heat exchanger tube bundle, eddy current testing technology was adopted to detect the tube bundle. The wall thickness loss of the tube bundle was evaluated based on the data and images of far-field eddy current testing, and the inspection and preventive measures for overhaul were put forward. The test results showed that the heat exchanger tube bundle has large areas of thinning and pits, which cannot meet the requirements of long-term operation of the plant, and further protective measures are needed to ensure the safe and stable production. This is also the validation application of far-field eddy current testing technology in equipment performance evaluation of megaton ethylene plant.

A new method of alkali solution analysis was established, which could accurately analyze the NaHCO₃ and NaHS content of waste alkali liquor to provide adjustment basis for the transformation of caustic wash system from Lummus caustic wash process to Nagao soda caustic wash process. By adding caustic injection line to the caustic wash system, the injection amount of fresh alkali liquor can be timely adjusted when the sulfur content fluctuates, thus effectively reducing the usage of fresh alkali liquor and avoiding the unqualified caustic wash. By adding water injection line to the caustic wash system, the plugging of pipeline caused by the crystallization of waste alkali liquor delivered can be prevented. By reducing the formation of grease in the caustic wash system and maintaining proper caustic wash temperature and pressure, the stable operation of the caustic wash system can be ensured. After the optimization and adjustment of the caustic wash system, the concentration of the first-stage alkali liquor decreased from 1％~2％ to 0, and the concentration of the second-stage alkali liquor decreased from 8％~15％ to 8％~10％. The fresh alkali consumption per ton of ethylene was reduced from 6.3 kg to 3.6 kg, and the waste alkali discharge per ton of ethylene was reduced from 21.4 kg to 16.3 kg, achieving the emission reduction of caustic wash system.

The process flow characteristics of the No.2 cracking gas compressor (GB1201) in ethylene complex in the Olefin Plant of SINOPEC Yangzi Petrochemical Co., Ltd. are introduced. By summarizing the steam consumption and the work done by cracking gas compressor turbine and the compressor efficiency, the relevant factors affecting the first-stage suction pressure of the cracking gas compressor are analyzed, the reasons for the high first-stage suction pressure are identified and some improvement measures are proposed, providing operational guidance for the long-term and efficient operation of the cracking gas compressor.

The vacuum loss of turbine in heat pump compressor occurred many times during the normal operation of the ethylene plant at PetroChina Liaoyang Petrochemical Company, seriously affecting the safety of the compressor unit and the operation load of the ethylene plant. Through analysis and overhaul, it was verified that there were problems such as the insufficient design capacity of jet pump and the scaling of condenser. After overhaul, these problems were solved completely, thus ensuring the efficient, safe, stable and economic operation of the compressor unit.

This paper discusses the stability of the waste water system after SSBR plant at PetroChina Dushanzi Petrochemical Company by using DLVO theory. The fundamental reason for the operation problem is the damage to the stabilizing system and the system blockage resulted by the suspension of larger rubber materials agglomerated by oil and rubber particles in the oily water. In this paper, some short-term and long-term improvement measures are put forward such as setting up new waste water pre-treatment facility and revamping the primary waste water treatment unit after SSBR plant by using gas energy flocculation technology to remove all the rubber particles and surfactants in waste water.

In order to guarantee the quality of super-high-pressure steam, it is necessary to regularly drain the quench boiler where the super-high-pressure steam generates. Due to the high temperature and pressure of blowdown water and the frequent switching operation, serious internal leakage often occurs at the blowdown valve, leading to a lot of waste. To save energy and improve economic benefit, cascade recovery of waste heat was carried out for the leaking blowdown water through calculations, achieving the goals of energy saving, consumption reduction and efficiency improvement.

The A-type polymerization inhibitor used in the separation unit of a 1,000 kt/a ethylene plant has good coking inhibition effect, but it was easy to crystallize at low temperature, thus blocking the polymerization inhibitor delivery line and cutting off the polymerization inhibitor flow. According to the research, with the addition of CY solution, which is the bottom product of debutanizer, the A-type crystal can dissolve completely and no crystal will precipitate after 72 h when the reaction temperature is -10 ℃, the speed is 120 r/min, the dissolution time is 1 min and the mass ratio of crystal to CY solution is 1:4. Based on the experiment results, two plans are proposed including the continuous addition of CY solution to inhibit the crystallization of A-type polymerization inhibitor and the intermittent addition of CY solution to dredge the polymerization inhibitor delivery line.