189- Reform plan using feather vane separation technology for the first cycle gas liquid separation tank in the dioxalate synthesis unit of the waste gas to ethylene glycol project

In recent years, guided by the principles of energy conservation, emission reduction, and efficiency improvement in the coal chemical and coal coking industries, many such enterprises have utilized waste gas for advanced processing and comprehensive utilization, establishing projects to produce methanol from coke oven gas and ethylene glycol from waste gas. These early-established projects for the in-depth processing of waste gas from coke ovens were, due to the limitations of technological and equipment capabilities at that time, characterized by relatively low standards in terms of process and equipment technology. As a result, compared with newly built similar projects that utilized advanced technologies, these projects had higher consumption levels, higher operation and maintenance costs, lower production efficiency, and weaker market competitiveness; hence it was necessary to carry out technical upgrades to overcome the \"bottlenecks\" in their process and equipment. Among them, the originally constructed project for synthesizing ethylene glycol from waste gas is one such example.

This post was last edited by luoli519 on 2021-8-20 at 14:55. Compared to projects that use syngas such as waste gas and coke oven gas to produce ethylene glycol (projects that produce ethylene glycol through the oxidation of ethylene are not classified as such), projects that utilize syngas from waste gas and coke oven gas to produce methanol were actually implemented earlier and in greater numbers. To some extent, the problems associated with these methanol production projects – including high consumption, high operation and maintenance costs, low production efficiency, weak market competitiveness, and numerous bottlenecks in the processing equipment – are even more severe than those encountered in projects that use such syngas to produce ethylene glycol. The reason for choosing projects that utilize syngas such as waste gas and coke oven gas to produce ethylene glycol for analysis and discussion here is, on the one hand, that such projects involve more reaction units, which makes them more suitable for analytical examination; on the other hand, we happen to have recent cases of technical upgrades and modifications for projects using syngas like waste gas and coke oven gas to produce ethylene glycol, so the data available for analysis and discussion is more abundant and practical.

This post was last edited by luoli519 on 2021-8-20 at 18:29. In the series of upgrades and improvements aimed at addressing the \"bottlenecks\" in the process equipment that arise during the actual operation of projects for producing ethylene glycol from syngas such as waste gas and coke oven gas, we already discussed in a previous technical discussion post the technical upgrades for the gas-liquid separation and mist removal equipment at the top of the esterification tower in the nitrosation reaction synthesis unit. This technical discussion post focuses on the use of vane separation technology to address the issue of low separation efficiency in the first cycle gas separation tank used in the carbonylation-oxidation coupling reaction to produce dimethyl oxalate.

This post was last edited by luoli519 on 2021-8-20 at 18:30. Carboxylation synthesis, as the name implies, is a synthetic reaction that involves carbon monoxide (CO). In projects for the comprehensive utilization of waste gas, coke oven gas, and syngas – such as methanol synthesis, ethanol synthesis, ethylene glycol synthesis, acetic acid synthesis, oxalic acid synthesis, etc. – there are carbonylation units. In carbonylation reactions, in the vast majority of cases, the one-way conversion rate of gaseous substances such as CO involved in the reaction is not high; therefore, most of the unreacted gases need to be recycled back into the reactor to participate in the reaction, thereby increasing the overall conversion rate of the gases. And this majority of unreacted gas, which needs to be recycled back into the reactor, forms a mixed stream with the carbonylation reaction products (many of which are liquid) and is released from the end of the reactor. The products of the carbonylation reaction, especially this portion of liquid material, must be separated and collected from the circulating gas stream. On the one hand, separating and removing the carbonylation reactants from the circulating gas stream as promptly and completely as possible is necessary in order to achieve the highest possible one-pass yield of the product ； Secondly, it is necessary to separate and remove the carbonylation reactants from the circulating gas stream as promptly and completely as possible, so as to prevent the carbonylation products from participating in subsequent reaction cycles along with the circulating gas stream. This approach helps avoid excessive reactions of the carbonylation products that could lead to the formation of by-products and impurities, thereby reducing the selectivity of the catalytic reaction, depleting the catalytic activity, and shortening the effective service life of the catalyst ； Thirdly, it is necessary to separate and remove the carbonylation reactants from the circulating gas flow as promptly and completely as possible, so as to prevent the carbonylation products from participating in subsequent reaction cycles along with the circulating gas flow. This approach helps to minimize energy consumption and waste in the operation of the facility, while avoiding any impact on the proper functioning of downstream pipelines and equipment, as well as preventing safety accidents. The primary separation device responsible for removing the carbonylation reactants from the circulating gas stream is the main subject of analysis and discussion in this technology, namely the first circulating gas liquid separator.

This post was last edited by luoli519 on 2021-8-20 at 18:30. The first cycle gas separation tank for the carbonylation unit in the ethylene glycol production project using waste gas, which we upgraded for our client, is located right after the circulating water cooler at the exit of the carbonylation reactor. The client’s original first cycle gas separation tank was of vertical design, with dimensions of ID 2900 mm * SM/SM 4516 mm * SK 1065 mm, and was made of S30403 material. The customer’s original first-cycle gas-liquid separation tank used a traditional, simple-type wire mesh demister with a thickness of 150 mm, which was arranged in a radial pattern on the upper part of the tank. During actual operation, it was observed that there was significant liquid in its gas discharge pipeline; in particular, a bubbling sound could be heard in the exhaust pipeline due to the liquid being pushed along by the airflow. A considerable amount of liquid was collected during maintenance work ； There is also a situation where the operating pressure drop exceeds 10 kPa, which is more than twice the designed upper limit of 5 kPa; as a result, it is necessary to replace the wire mesh demister during the annual maintenance period, a process that is time-consuming and labor-intensive.

This post was last edited by luoli519 on 2021-8-20 at 18:31. Why is the separation performance poor in the first cycle gas-liquid separator using the traditional simple-structure mesh demisting technology? Let’s conduct the following systematic analysis and discussion together: First of all, carbonylation reactions are mostly reactions that result in an increase in molecular weight, and the reaction products tend to be in a liquid state. The carbonylation-oxidation-coupling reaction in the waste gas, coke oven gas, syngas, and ethylene glycol project falls under this category. The stream released from the reactor undergoes cooling and heat exchange, causing the liquid components in the mixture to form slug flows, pulse flows, or even a continuous liquid flow. For such large-scale bulk flows, slug flows, or even continuous liquid flows of liquid substances, specialized vane-type separation inlet assemblies are required for dynamic separation.

This post was last edited by luoli519 on 2021-8-20 at 16:18. The image below shows the typical vane separation inlet assembly that we use.

The main function of the aforementioned vane separation inlet assembly is, in addition to carrying out the separation of large-sized liquid mass flows, slug flows, or even continuous liquid streams, to also pre-remove large-sized liquid masses and droplets, thereby providing a greater processing capacity for the internal components designed to improve separation precision step by step. Furthermore, the feather vane separation inlet assembly is also capable of directing the mixed flow to a dynamic space that is most conducive to the efficient operation of the downstream gas-liquid separation internals, as well as of performing an initial distribution of the flow pattern, thereby establishing the necessary dynamic conditions for the efficient operation of those downstream gas-liquid separation internals. In Shell’s design specifications for DEP separators, this type of inlet separation assembly is preferentially recommended.

Second, the gas-liquid mixture flows in through the 1100 mm diameter inlet pipe of the first circulation separation tank into a expansion chamber with a diameter of 2900 mm, and then exits the system through an outlet pipe with a 1100 mm diameter; the gas flow undergoes a change in flow pattern, progressing first before contracting. To what extent does the flow pattern develop and contract, is it sufficient, and does it meet the basic prerequisites for dynamic separation? In precision dynamic gas-liquid separation technology, this task is carried out by a pre-distributed coalescing internal component set.

This post was last edited by luoli519 on 2021-8-20 at 18:31. The image below shows the actual pre-allocated coalescing internals, provided for everyone to see and understand it visually. Pre-allocated coalescing internals sets are often arranged in multiple composite configurations, and are designed, manufactured, and installed/moved using a convenient detachable structure.