【Recommended Article】The gap between quench oil circulation pumps and advanced foreign pump manufacturing technologies, as well as strategies for domestic production

I. Factors Affecting the Localization of Quench Oil Circulation Pumps 1. Large variations in quench oil viscosity: An increase in the viscosity is caused by factors such as an increase in aromatics in the raw materials, which affects the performance of the pump – resulting in low head pressure and insufficient flow rate. Conversely, insufficient circulation of quench oil leads to increased viscosity, causing unstable operation of the quench oil circulation pump and frequent failures, thus creating a vicious cycle. 2. The quench oil contains a large amount of coke powder, and the measures taken to remove this coke powder are insufficient. In the ethylene plants with a production capacity of one million tons per year in Tianjin and Zhenhai, the design for removing coke powder from the quench oil in the cracking process involved the use of coarse filters at the inlet of the circulation pump, as well as pneumatically or electrically driven rotary scrubbers at the outlet, in order to reduce the accumulation of coke powder in the quench oil. Due to limitations such as the circulation rate, the filtering precision was designed to only remove coke powder particles larger than 2.5 mm; smaller particles below 2.5 mm could not be removed and remained in the quench oil. As the operation time of the plants increased, more and more of this coke powder accumulated in the system, severely affecting the safe operation of the quench oil circulation pumps. In the ethylene plants with a production capacity of one million tons per year in Tianjin and Zhenhai, as well as in the 800,000 tons per year ethylene plant in Wuhan, improvements were made to the quench oil filtration systems. A hydrocyclone was installed at the outlet of the quench oil circulation pump to remove coke powder from the oil, achieving a removal efficiency of over 99% for coke powder particles with a diameter of 0.5 mm or more, and 95% for particles with a diameter of 50 μm or more. This significantly improved the operating conditions of the quench oil pumps, creating favorable conditions for their safe and long-term operation.

【HaiChuan Quality Articles Sharing】The development history of domestic linear quenching boilers https://bbs.hcbbs.com/thread-5693280-1-1.html (Source: HaiChuan Chemical Forum)

II. Gap compared with advanced foreign technologies: Compared with advanced foreign manufacturers of petrochemical pumps, China’s level of petrochemical pump manufacturing still has a certain gap. In terms of the overall planning of series products, advanced pumps from foreign countries feature a high degree of systematicness, with very detailed and comprehensive technical documentation. Details such as the performance curves for the entire series, the types of structural variations, the available materials, the accompanying seals and bearings, the critical speed, the lubrication system, the bearing life, the maximum allowable speed, and the temperature-pressure curves of the materials are all provided in great detail; this information is obtained through numerous experiments. Products developed domestically often consist only of drawings and process documents, lacking systematicness and experimental verification. In terms of manufacturing precision, imported advanced pumps are manufactured with great care, especially regarding the surface treatment of the flow channels in components such as impellers, guide vanes, and casings; it can be said that this treatment is extremely meticulous. For example, the surfaces of the flow-through components in Ebara Corporation’s petrochemical pumps are manually polished, resulting in a surface roughness similar to that of turbine blades – almost mirror-like. It is rare for domestic companies to achieve such a level of quality. In terms of product reliability, domestic companies often cannot provide clear answers regarding it – for example, they do not know exactly how long a pump will last, how many hours the seals and bearings can operate before failing, what the level of safety is, or what evidence exists to support these claims. Because we often only have theoretical calculations and no experimental verification, we lack confidence and a solid basis when technical discussions involve such issues. In terms of the quality of materials and accessories, due to the relatively weak foundation of basic materials in our country, the quality of raw materials and accessories as a whole fails to reach international advanced standards, such as in the case of castings, valves, seals, and monitoring instruments. There are certain gaps in the product design philosophy; for example, economic efficiency and systematicity are rarely considered in product design, with an emphasis on design over planning.

III. Slow progress in localization: Although there has been **continuous advocacy for the localization of major petrochemical equipment, the actual progress is slow, and the rate of localization lags behind the development pace of the petrochemical industry. Due to factors such as the restructuring and joint ventures of many state-owned enterprises in the pump industry, the localization of large-scale petrochemical pump equipment in China has been significantly affected; this market was quickly taken over by foreign companies such as Japan’s EBARA, Switzerland’s SULZER, and the United States’ FLOW-SERVE. Although domestic companies are able to manufacture these key pumps, even by using technology imported from foreign firms, it is still not entirely reliable, and there are certain concerns regarding their selection. Moreover, imported equipment also has various issues in operation; especially for the first sets of equipment (i.e., those that have no prior record of actual use), it is preferable to spend more money and import the key equipment instead. Therefore, the domestic production of quench oil circulation pumps holds great prospects.

IV. Feasibility of Local Production of Quench Oil Circulation Pumps 1. Thorough removal of coke powder from quench oil from a process perspective – Addressing the source of coke powder in quench oil at its origin; the coke powder in quench oil mainly comes from the accumulation of coke powder resulting from burning in the cracking furnace before the switching valve for cracking gas, with a smaller amount coming from abnormal shutdowns of the cracking furnace during operation. Since the cracking furnace in ethylene plants uses an online coking process, there is a certain distance between the valves on the cracking gas pipeline and the interface of the coking gas pipeline. When the cracking furnace is in coking mode, coking gas and coke powder accumulate in front of the valves on the cracking gas pipeline. During operation, as these valves open, the gases along with the quench oil flow into the quench oil tower, from where they are circulated to various systems using the quench oil, in a repeating cycle, with more and more material accumulating over time. The hardness of coke powder particles is related to the operating cycle of the pyrolysis furnace; the longer the operating cycle of the furnace, the harder the coke powder particles become. The hardness of such coke powder has been measured to reach HRC 60. To eliminate the accumulation of coke dust, the following measures can be taken: Install purging and pressurization facilities before the pyrolysis gas switch valve to prevent coke dust from being carried along with the pyrolysis gas between the pyrolysis gas valve and the coking pipeline during coking, thereby avoiding its accumulation at this location and reducing the amount of coke dust that enters the quench oil system. Swapping the locations of the pyrolysis gas and coking gas pipelines can also prevent coke dust from accumulating in that area during the coking process in the pyrolysis furnace. However, this approach results in quench oil accumulating in front of the valves of the coking gas pipeline during operation; if the pyrolysis gas is released directly into the atmosphere during coking, the quench oil will also be released into the atmosphere, affecting the environment. This problem does not arise if the pyrolysis gas is discharged through the furnace chamber. Continuously improve the measures in the quenching cycle system to remove coke powder, so as to minimize the amount of coke powder in the quenching oil system and thereby improve the operating conditions of the quenching oil circulation pump.

2. Adjust the viscosity of the quench oil: By adjusting the amounts of heavy fuel oil and light fuel oil taken in, the viscosity of the quench oil is adjusted as appropriate to ensure that it remains within the designed operating range. 3. Select a suitable quench cooler and determine the appropriate pump head. The quench oil mixes with the pyrolysis gas in the oil quench cooler; one of the important functions of the quench oil circulation pump is to rapidly cool the pyrolysis gas. Only by selecting an appropriate oil quench cooler can the head required for the quench oil circulation pump be determined. There are two types of oil quenchers commonly used today. One is the overflow-type quencher, which features a simple structure, poor mixing efficiency, slow cooling rate, long process flow, high consumption of quenching oil, and requires a quenching oil circulation pump with low head pressure. Another type is the injection type, which uses multiple nozzles to inject quench oil into the pyrolysis gas line. This method ensures thorough contact with the pyrolysis gas, results in a rapid cooling of the pyrolysis gas, requires relatively less quenching oil, but demands a higher head from the quenching oil pump. Furthermore, due to the small flow channels in this structure, it is prone to clogging, which affects the cooling effect. The high head of the quench oil circulation pump presents another drawback: if there is an internal leak in the dilution steam generator, and since the pressure on the quench oil side is higher than that of the process water, the quench oil will leak into the process water side, contaminating it and weakening the steam generation system, which in turn has negative effects on the operation of the cracking furnace. When selecting a quencher, it is possible to combine these two characteristics, taking advantage of the positive aspects and eliminating the negative ones, thereby achieving better results.

Select an appropriate drive method. Thanks to the rapid development of power supply systems in recent years, grids now employ dual-power supply systems, rapid switching capabilities, and self-starting mechanisms for low-voltage equipment, all of which have significantly improved the reliability of these systems. For driving the quench oil circulation pumps, direct motor drive should be used, moving away from the traditional approach of using steam turbines coupled with gearboxes. 5. Domestic components: Some spare parts have been made domestically; in particular, mechanical seals have been produced locally for many years, and the issues that arose have been addressed through improvements and modifications, ensuring they can meet production needs. Analysis of high-chromium wear-resistant materials: The high-chromium wear-resistant materials developed in China have reached the same level as similar foreign products; the service life of iron linings exceeds 4 years, and their wear resistance depends on the optimal combination of their hardness and toughness. Its overall hardness depends on the metal matrix, the quantity of carbides, and their microhardness, while its toughness depends on the microstructure of the matrix as well as the shape, quantity, and distribution of the carbides. To improve its overall performance and expand its range of applications, in recent years, building on the research conducted in these areas domestically, new processing technologies have been developed to achieve the optimal balance of high hardness and high toughness under different operating conditions, resulting in many new achievements.

V. Localization status of similar equipment: Slurry pumps are widely used in important industries such as coal, mining, power generation, metallurgy, and water conservancy. As one of the key components of slurry pumps, the impeller is subjected to a combination of factors such as wear from sand and gravel, impact from pebbles, corrosion by wastewater, and cavitation. Operating under such harsh conditions leads to severe wear of the component; coupled with defects in the part itself, the wear process becomes quite complex. To extend the service life of impellers, efforts are ongoing to find high-performance anti-wear materials. For example, a company in the United States has developed innovative ceramic-metal composite materials; the Japanese company Simon-I-Woman has created ceramic impellers; and the Australian company Woman has developed materials such as A61 (with a hardness of 59–61 HRC) and A217 (with a hardness of around 64 HRC). At present, some domestic manufacturers have achieved success in developing high-alloy, high-hardness wear-resistant cast iron (GSM) materials, which have shown significant effects in practical applications. GKM material has high hardness and high brittleness; the impeller features discontinuous cutting surfaces, making high-speed cutting difficult. It is difficult to ensure cutting quality. To address this challenge, researchers have developed polycrystalline cubic boron nitride cutting tools that possess high hardness, good wear resistance, excellent high-temperature red hardness, and high impact resistance. These tools enable high-quality machining and can meet the technical requirements for processing slurry pump impellers. Meanwhile, multiple units with a capacity of 10 million tons per year for oil refining have been put into operation. In distillation units, the hydraulic models of the recycle pumps for the initial distillation tower and those for the bottom of the atmospheric distillation tower are essentially the same, and there are already several domestically produced units of this type in use.

VI. Conclusion: With the rapid development of the refining industry, the domestic pump industry has gained significant growth opportunities, and new progress has been made in the research and development of pump products, as evidenced by an increase in the variety and specifications of process pumps. Many process pumps produced by relying on imported technologies have been serialized, and some older products have also been improved based on the adoption of such imported technologies. Low-flow, high-head pumps, corrosion-resistant pumps, and sealless pumps have all expanded the range of products available. In particular, key process pumps and large-scale water pumps, such as high-end pumps used in the petrochemical industry like hydrogenation feed pumps, radiant furnace feed pumps, vertical and horizontal high-speed pumps, as well as cryogenic pumps, have been successfully developed and put into use through the relentless efforts of manufacturers and users, achieving remarkable results for the domestic industry. Furthermore, some pump manufacturers can provide automatic monitoring and control technologies at the customer’s request, to ensure that pumps in critical areas operate safely, reliably, and within their efficient operating range. Therefore, by continuously improving the operating conditions of the quench oil circulation pump, it is entirely possible to localize the production of such pumps and ensure their safe and reliable operation, thereby breaking the monopoly held by foreign companies over large-scale ethylene plant technology in this field.