Research And Development Of The Novel Solvent With Excellent Desulfurization Performance For Purifying High Sour Petroleum Natural Gas

With the fast development of domestic petroleum natural gas industry in the past few years, the Puguang natural gas field which is extremely rare in worldwide gas fields because of its high sour components contents, has been observed and is being developed. As "the second fire wall", the purification solvent with high absorption selectivity for the impurities such as H2S and organosulfurs needs to be developed in order to meet the strict purification requirement. Furthermore, it is of great significance to develop the purification solvent with independent intellectual property rights in the consideration of the localization of desulfurization solvent as well as smooth and steady running of domestic purification plants.The composition design of a novel solvent oriented by enhancing solubility and mass transfer properties of organosulfurs absorption into solvent was conducted by using thermodynamics and kinetics analysis methods as well as the quantum chemistry calculation method. Based on the basic formation, the novel UDS solvent shows not only the perfect removal performance for H2S but also high removal efficiency for organosulfurs.The results of dynamics analysis and the quantum chemistry calculation indicate that MOR component with ringed structure can accelerate the zwitterion deprotonation reaction and significantly catalyze the COS hydrolysis reaction, thus, improved the chemical removal efficiency of COS in solvent. Meanwhile, SUL component increases the physical solubility of COS and mercaptans in solvent. As a result, the UDS solvent displays an excellent performance for removing organosulfurs from high sour petroleum natural gas.Hereafter, the equilibrium behavior and mass transfer property of COS, methyl mercaptan (MeSH), ethyl mercaptan (EtSH), iso-propyl mercaptan (i-PrSH) as well as n-propyl mercaptan (n-PrSH) in UDS solutions were measured at static equilibrium apparatus and the packed column. The solubilities of five organosulfur compounds in UDS solutions show the turns as:MeSH>EtSH>i-PrSH>n-PrSH. As compared with MDEA solvent, the smaller Henry constants and the larger mass transfer factors have been observed for UDS solvent, suggesting the higher solubility and the better transfer performance of organosulfurs absorption in UDS solvent.In addition, the corrosivity and the foam behavior of UDS solution were investigated. By adding corrosion inhibitor into UDS solvent, the passive film is formed in the surface of the metal and the corrosion rates of stainless steel and carbon steel exposed to UDS solutions are reduced significantly. In the same condition, UDS solution indicates lower corrosivity as compared to MDEA solution. Meanwhile, UDS solution shows the low foaming trend after adding 20 ppm DF-E.Then, the absorption experiments for purifying high sour petroleum natural gas using UDS solvent were executed at simulation and side-stream absorption units, respectively. The purification results indicate that UDS solvent have equivalent removal performance for H2S and higher removal efficiencies for organosulfurs as compared with MDEA solvent. The organosulfurs removal efficiencies of UDS solvent are 30～40% higher than MDEA solvent as the content of UDS-F component is above 20%. Moreover, UDS solvent also shows the satisfactory removal efficiency for CO2.Based on the excellent desulfurization performance obtained from simulation and side-stream experiments, the industrial application test of UDS solvent was carried out in Puguang Natural Gas Plant. Under the present operation conditions of industrial plants and keeping the whole purification process, the COS contents in natural gases from the top of the first absorption column are 165 and 220 mg/m3 as using UDS and MDEA, respectively. For UDS solvent, the COS content in purified natural gas is 135 mg/m3 while the hydrolysis reactor is shut down. The quality of purified natural gas met the second-class standard. The organosulfur removal efficiency of UDS solvent is 20～27% higher than that of MDEA solvent. The steam consumption for regenerating UDS solvent seems to be similar to the consumption for MDEA solvent. As compared to MDEA solvent, the flow and organosulfur contents of flashing gas from the purification plant using UDS solvent are lower under the similar conditions.