CN-121988164-A - Online reviving method for liquefied gas self-cleaning active alkali sweetening process

Abstract

The invention discloses an online reviving system and method for a self-cleaning active alkali desulfurization process. Aiming at the problem that alkali liquor is deactivated due to the reduction of the solubility of sodium mercaptide caused by accumulation of heat stable salt, the invention adopts skid-mounted equipment to lead out the deactivated alkali liquor, and sequentially removes organic sulfur matters through adsorption of active carbon, interception of suspended matters through sand filtration, cooling and salt precipitation, removal of inorganic salt crystals through cold filtration, deep removal of heat stable salt such as sulfate radical, thiosulfate radical and the like through anion resin exchange, and blending of alkali compensation, and finally returns to a main system. The invention realizes the on-line regeneration of the main device without shutdown, effectively recovers the desulfurization performance of the alkali liquor after reactivation, has high removal rate of heat stable salt, remarkably prolongs the service life of the alkali liquor and reduces the discharge of waste liquor.

Inventors

• ZHU LIJUN
• Li Menying
• SUN YUJIE
• LIU SHUO
• BAI YAN

Assignees

• 中国石油大学(华东)

Dates

Publication Date

20260508

Application Date

20260407

Claims (1)

1. 1. The online reviving system for the self-cleaning active alkali desulfurization process is characterized by comprising a skid-mounted integrated platform and the following functional units mounted on the skid-mounted integrated platform: The system comprises an alkali liquor extraction unit, an adsorption purification unit, a cooling and salt precipitation unit, a cold filtration unit, an anion resin exchange unit, an alkali replenishment preparation unit and an alkali liquor return unit, wherein the alkali liquor extraction unit is connected with a lean desulfurizing agent circulation pipeline of a main process system in parallel, the adsorption purification unit comprises an active carbon adsorption tower and a sand filter which are sequentially connected in series, the cooling and salt precipitation unit comprises a heat exchanger and a crystallization tank, the cooling and salt precipitation unit comprises a precision filter and/or a centrifugal separator, the anion resin exchange unit is connected with the cooling and salt precipitation unit and filled with strong alkaline anion exchange resin, the alkali replenishment preparation unit is connected with the anion resin exchange unit and comprises an online analyzer and an alkali replenishment tank, and the alkali liquor return unit is connected with the alkali replenishment preparation unit and is used for returning the revived alkali liquor to the main process system; The online reviving system for the self-cleaning active alkali desulfurization process is characterized by comprising the following steps of: (1) Leading out alkali liquor, namely leading out the deactivated alkali liquor to be revived from a lean desulfurizing agent circulation pipeline of the main process system; (2) Adsorption purification, namely sequentially passing the deactivated alkali liquor through an active carbon adsorption tower and a sand filter to remove macromolecular organic sulfides and suspended particulate matters; (3) Cooling to-5-10 deg.c for separating out salt to separate out partial inorganic salt; (4) Cold filtering to separate out salt crystal and obtain primary purified alkali liquor; (5) Strong alkaline anion resin exchange, namely, introducing primary purified alkali liquor into strong alkaline anion resin, and selectively exchanging to remove heat stable salt anions to obtain deep purified alkali liquor; (6) Adding alkali, namely detecting components of the deeply purified alkali liquor, adding missing alkali and additives, and recovering the alkali liquor to the composition of a fresh desulfurizing agent; (7) Returning alkali liquor, namely returning the revived alkali liquor to a lean desulfurizing agent circulation pipeline of the main process system; The on-line reviving system for the self-cleaning active alkali desulfurization process is characterized in that the strong alkaline anion exchange resin used in the step (5) is N, N-diethyl hexadecylamine modified strong alkaline anion exchange resin, the preparation method is that chloromethylated white balls are used as carriers, the chlorine content is generally controlled to be 15-20%, the raw materials are proportioned, the chloromethylated white balls are 1 part by weight, the N, N-diethyl hexadecylamine is 0.5-1.0 times of the molar mass of the chlorine balls, the trimethylamine is 0.5-1.0 times of the molar mass of the chlorine balls, the dichloroethane is adopted as a solvent, the amount is 3-5 times of the molar mass of the chlorine balls, the chlorine balls are added into the dichloroethane, swelling is carried out for 4-6 hours at room temperature, then the N, N-diethyl hexadecylamine and trimethylamine are added, the temperature is raised to 70-90 ℃, the reaction is finished, the anhydrous ethanol and deionized water are used for full washing to remove residual unreacted amine and organic solvent, and the N-diethyl hexadecylamine is subjected to high-concentration anion exchange treatment, and alkali solution is obtained after the high-concentration of the N-diethyl hexadecylamine is subjected to the alkali resin. The online reviving system for the self-cleaning active alkali desulfurization process is characterized in that coconut shell active carbon or coal active carbon is filled in an active carbon adsorption tower in the step (2), the airspeed is 0.5-5 h < -1 >, the temperature of cooling and salting-out in the step (3) is controlled to be minus 2-5 ℃, the residence time is 60-90 min, a precise filter with the filtering precision of 0.5-10 mu m is adopted in cold filtration in the step (4), the exchange capacity of N, N-diethyl hexadecylamine modified strong alkaline anion resin in the step (5) is more than or equal to 3.0 mmol/g, the operation airspeed is 1-10 h < -1 >, and the supplementary alkali and additives in the step (6), and the self-cleaning active alkali desulfurization agent comprises non-sodium alkali, organic alkali, a sulfur-philic sodium dirty solvent and a phase transfer surfactant; The on-line reviving method is operated continuously or intermittently under the condition that the main device is stopped or not stopped, the performance of the revived alkali liquor for removing the mercaptan is recovered to more than 90% of the fresh alkali liquor, and the removal rate of the heat stable salt is more than 85%.

Description

Online reviving method for liquefied gas self-cleaning active alkali sweetening process Technical Field The invention belongs to the technical field of liquefied gas sweetening, and particularly relates to an online reviving system and method for a self-cleaning active alkali desulfurization process, in particular to a skid-mounted online reviving method for reviving an inactive sweetening alkali solution by removing macromolecular organic sulfide and heat stable salt in the inactive alkali solution through the processes of active carbon adsorption, sand filtration, low-temperature salt precipitation, cold filtration, resin exchange, alkali supplementation and the like. Background 1. Composition and hazard of mercaptans in liquefied gases Liquefied Petroleum Gas (LPG) is mainly derived from catalytic cracking, coking, atmospheric and vacuum devices in refineries, and light hydrocarbon recovery processes in oil and gas fields. In these processes, liquified gases carry a variety of sulfides, which fall into two main categories: The inorganic sulfur is mainly hydrogen sulfide (H 2 S) and can be easily removed by an amine washing method. The organic sulfur mainly comprises mercaptan compounds such as methyl mercaptan, ethyl mercaptan, propyl mercaptan and the like, and a small amount of disulfide, methyl sulfide, carbonyl sulfide and the like. Wherein, the mercaptan is the main component of organic sulfur, the proportion of which can reach more than 90 percent, and is also the difficult point and the important point of desulfurization. The presence of mercaptans can present a number of hazards: (1) The product quality problem is that the mercaptan has bad smell, which leads to unqualified liquefied gas products; (2) Downstream processing effects, namely poisoning and deactivation of the catalyst in subsequent processing; (3) Equipment corrosion, namely sulfide has corrosiveness on pipelines and storage containers; (4) And environmental pollution, namely generating SOx when being burnt as fuel to form acid rain pollution. The national standard of liquefied gas (GB 1174-1997) prescribes that the mass fraction of total sulfur in the liquefied gas is less than 343 mg/m < 3 >, and the corrosion grade of copper sheets is less than 1 grade. With increasingly strict environmental protection requirements, the upgrading of oil quality further requires the reduction of the sulfur content of MTBE, and further requires the reduction of the sulfur content in the liquefied gas to below 20 mg/m 3. 2. Basic principle of liquefied gas sweetening At present, the vast majority of liquefied gas sweetening adopts a Merox extraction oxidation method. The process comprises two core steps: First step, extraction reaction The thiol in the liquefied gas is neutralized with alkali liquor (sodium hydroxide solution) to generate sodium mercaptide and enters into alkali liquor phase. The reaction formula is as follows: RSH + NaOH → RSNa + H2O The mercaptan is transferred from the liquefied gas phase to the alkaline liquid phase for desulfurization purposes. Second step, alkali liquor oxidation regeneration The alkali liquor enriched with sodium mercaptide reacts with oxygen under the action of a catalyst to oxidize the sodium mercaptide into disulfide and simultaneously regenerate sodium hydroxide. The reaction formula is as follows: 4RSNa + O2 + 2H2O → 4NaOH + 2RSSR the regenerated lye can be recycled and the disulphide is separated as a by-product. 3. Major problems of the conventional Process The conventional Merox process has the following prominent problems in industrial applications: 1. Insufficient desulfurization depth Sulfide in liquefied gas after mercaptan removal in the traditional process is mainly disulfide. Analysis shows that the disulfide is oxidized by mercaptan during the process of eliminating mercaptan, and the two main sources include that the disulfide formed during alkali liquor regeneration is not removed in time, and the disulfide is re-extracted into liquefied gas after the alkali liquor is recycled back to the extraction section, and the regenerated catalyst is dissolved in the alkali liquor to form 'alkali catalyst', and sodium mercaptan is catalyzed to be oxidized into disulfide in the extraction section. 2. The discharge amount of the alkaline residue is large Along with the extension of the operation time, heat Stable Salts (HSS) such as thiosulfate, sulfate and the like can be accumulated in the alkali liquor, so that the solubility of sodium mercaptide is reduced, the desulfurization activity is reduced, the concentration of the alkali liquor is reduced, frequent alkali replacement is needed, a large amount of high-toxicity waste alkali residues are generated, and the treatment cost is high. According to statistics, the national emission of liquefied gas mercaptan removal waste alkali is about 15 ten thousand tons/year, the biotoxicity is extremely high, and the investment cost for standard emission is quite