Online analysis of sulfur content in the purified gas outlet of MDEA units
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Our oil field has two MDEA units in operation. For the purified natural gas after desulfurization, it is necessary to monitor its sulfur content at all times; the typical measurement range is 0–50 ppm. We have used two types of online analyzers so far, both of which are manufactured by EMERSON in the United States, but their performance has not been satisfactory. The first analyzer used lead acetate paper strips, while the second was a direct-reading instrument. The problem was significant measurement errors. After analyzing the situation with the manufacturer, we discovered that there was liquid present in the natural gas. We then added separation equipment, but the issue persisted. The manufacturer suggested that the natural gas contained alkalis and required acid treatment. We ask that you consider the operating conditions of your own units – what methods do you use to measure the sulfur content in the purified gas? Let me share some operational experience. .
Online analytical instruments are regarded as the \"best\" among instruments, yet they are also the most difficult to operate. By taking into account the actual process conditions, we have improved the sampling and preprocessing system of these instruments and would like to share it with you all. . . High-sulfur natural gas (associated gas from oil fields) is fed into an MDEA unit for desulfurization treatment. Theoretically, the process design is quite perfect, but many problems arise during actual operation. Whatever these problems may be, they ultimately result in the sulfur content of the purified gas exceeding the specified limits. As for the instrumentation system, the main concern is not the excessive hydrogen sulfide level in the purified gas, but rather the harsh operating conditions. . Problem analysis: The measurement results of the purified gas differ significantly from those on-site. The hydrogen sulfide concentration on-site is above 100 ppm, while the instrument reads only a little over ten ppm. When calibrated using standard gas samples, the instrument functions properly, so why does this problem occur? Question 1: The hydrogen sulfide concentration at the outlet of the purified gas, as measured using a portable hydrogen sulfide detector, is 130 ppm. However, the fixed online hydrogen sulfide analyzer we have installed only detects a level of around a dozen ppm. The manufacturer of the analyzer stated that there are alkaline interfering gases in our gas; we conducted gas chromatography tests but found no alkaline gases. . On-site observation: Unequal amounts of black liquid were found in the sampling pipeline, contaminating the pressure reduction filter and rotameter of the instrument system. Problem analysis: The high concentration of amine solution in the absorption tower of the MDEA system led to mist entrainment; inadequate gas-liquid separation in the outlet separator of the purified gas caused the amine solution, heavy hydrocarbons, and deionized water condensate to enter the sampling system, thereby contaminating the pipelines and sampling equipment. This also affected the lead acetate test strips, resulting in inaccurate color readings by the color detector. . Take measures: Install sampling and liquid separation pretreatment facilities ； The specific structure is shown in the figure. After three stages of liquid separation, dehydration, and filtration, the readings obtained from the instruments were fairly consistent with those taken on-site, thus resolving this issue that had been affecting the quality monitoring of the device. .
Hehe, I hope we can have a pleasant collaboration this time:handshake