【Ethylene cracking】What is the quench device located above the cracking furnace? What are the structural features?

The quench heat exchanger is a device of great importance in ethylene cracking furnaces; it is required to rapidly cool the high-temperature cracking gas within an extremely short time, thereby preventing secondary reactions, reducing losses of the desired olefins, and simultaneously recovering thermal energy at high temperatures. The shell-and-tube quenching heat exchanger is divided into a tube side and a shell side; the medium in the tube side is high-temperature pyrolysis gas, while the medium in the shell side is cooling water. The typical process is as follows: the high-temperature pyrolysis gas enters the heat exchange tubes through the inlet head, while the cooling water from the high-pressure drum enters the shell-side space formed by the cylinder via the boiler feed pipe to carry out heat exchange. The rapidly cooled pyrolysis gas exits the quenching heat exchanger through the outlet head, and the cooling water, after heat exchange, leaves the quenching heat exchanger in the form of a water-vapor mixture via the water-vapor outlet pipe. A shell-and-tube heat exchanger uses a tube sheet to separate the tube side from the shell side, and is connected to the inlet and outlet heads by flanging or welding. During operation, the tube sheet is subjected to significant temperature difference stresses. At the junction between the tube sheet and the heat exchange tubes, expansion thermal stresses also arise due to differences in the metal wall temperatures. In existing technologies, an approach has been used that involves a reinforced thin tube sheet to address the aforementioned issues: a thick tube sheet is used to withstand the higher pressures in the shell side, while a thin tube sheet is welded to the heat exchange tubes to keep the metal wall temperature at a lower level. The two tube sheets are connected to each other by struts. The disadvantages of this type of reinforced thin tube sheet are its complex structure, high manufacturing difficulty, and high cost. Moreover, in large-diameter quenching heat exchangers, since the water side of the tube sheet is flat, the dirt deposited at the bottom of the shell side as well as the water vapor accumulated at the top of the shell side are difficult to remove, which leads to corrosion and damage to the equipment.

On October 3, with the assistance of a 1,000-ton crawler crane used as the main lifting device and an 80-ton crawler crane for supporting the load, the first quench reactor for Yantai Wanhua’s 1 million tons per year ethylene cracker, constructed by Shijian, was successfully lifted into place, marking the beginning of the installation of the cracker’s quench reactors. The ethylene project is equipped with a total of 6 cracking furnaces. Furnaces 1 to 5 each consist of 8 primary quenchers and 2 secondary quenchers. The primary quenchers have dimensions of 24 meters by 3.8 meters and weigh 30 tons; the secondary quenchers are 14 meters by 2.2 meters in size and weigh 56.1 tons. Criser No. 6 consists of 3 primary quenchers and 2 secondary quenchers. The primary quenchers have dimensions of 21 meters by 7 meters and weigh 24 tons each, while the secondary quenchers have dimensions of 7.6 meters by 2 meters and weigh 28 tons, and 14 meters by 2.5 meters and weigh 52 tons. All the quenchers are manufactured by the German company Borsig. As imported equipment, they are of high precision and come in carefully packaged forms. For a quencher weighing over 30 tons, the equipment used for protecting the finished wood products and the tools needed for unloading weigh more than 3 tons each; thus, very strict requirements are imposed on lifting operations. There are many challenges associated with lifting this equipment. Firstly, the steel structure has already been completed, and the lifting of the quench tank requires sequential installation without any risk of damage. Secondly, the lifting height is over 55 meters, making it highly sensitive to wind conditions; therefore, the lift crew must act quickly whenever the weather permits to complete the installation promptly. The Ten Construction Project Department prepares construction plans in advance based on the characteristics of the construction work, formulates corresponding safety and technical measures, selects cranes appropriately, and develops emergency response plans to ensure the smooth progress of lifting operations at the site.

【Ethylene Cracking】Summary Post on Discussion of Cracking Furnace Equipment Components https://bbs.hcbbs.com/thread-3308724-1-1.html (Source: Huahai Chuanliu – Haichuan Chemical Industry Forum)

The first quencher in the millisecond furnace system is a type of shell-and-tube heat exchanger that was successfully developed for the first time by drawing on advanced technologies from home and abroad. The first quencher in the millisecond furnace system is a key equipment for the ethylene cracking unit, which is part of the \"95 Major Technical Equipment Localization Project.\" This device rapidly quenches the pyrolysis gas generated by high-temperature cracking in the radiation section of the millisecond furnace, thereby stopping the cracking process and preventing secondary reactions and coking. As a result, high yields of ethylene (32% ethylene, 50% total olefins) can be obtained, along with the recovery of high-quality thermal energy. Technological characteristics and main materials of Ren 1.1 Technical characteristic parameters (see Table 1). This equipment is classified as a Class 3 pressure vessel. The design pressure for the outer and inner tubes is 12 MPa; the maximum operating pressure is 10.90 MPa. The design temperature is indicated in the notes, while the maximum operating temperature is also specified there. The inlet pressure is 3156 MPa, the outlet pressure is 885 MPa. The wall temperature is 315°C at the inlet and 343°C at the outlet. The name of the material (and its toxicity level) is high-pressure steam and boiler water hydrocarbons (flammable and explosive). The pressure for the hydraulic test is 15.0049 MPa, and the pressure for the airtightness test is…

This is a tubular jacketed quench heat exchanger produced by Borsig. A format different from the one in the above image. 24 meters is the height, and 3.8 meters is the width.

The common type is vertical; you are referring to the horizontal one