Research progress in hydrate-based technologies and processes in China: A review

Gas Hydrate-Based Heavy Metal Ion Removal from Industrial Wastewater: A Review

Innovating methods for treating industrial wastewater containing heavy metals frequently incorporate toxicity-reduction technologies to keep up with regulatory requirements. This article reviews the latest advances, benefits, opportunities and drawbacks of several heavy metal removal treatment systems for industrial wastewater in detail. The conventional physicochemical techniques used in heavy metal removal processes with their advantages and limitations are evaluated. A particular focus is given to innovative gas hydrate-based separation of heavy metals from industrial effluent with their comparison, advantages and limitations in the direction of commercialization as well as prospective remedies. Clathrate hydrate-based removal is a potential technology for the treatment of metal-contaminated wastewater. In this work, a complete assessment of the literature is addressed based on removal efficiency, enrichment factor and water recovery, utilizing the gas hydrate approach. It is shown that gas hydrate-based treatment technology may be the way of the future for water management purposes, as the industrial treated water may be utilized for process industries, watering, irrigation and be safe to drink.

New Technique Integrating Hydrate-Based Gas Separation and Chemical Absorption for the Sweetening of Natural Gas with High H2S and CO2 Contents

Given the drawbacks of the traditional MDEA absorption process, we introduced a hydrate-based gas separation approach. Then, to study the effectiveness of this method, we performed some hydrating experiments demonstrating that energy consumption could be remarkably reduced. However, the acid components (H₂S and CO₂) in the product gas failed to meet the specification requirements of the sales gas. Consequently, a new technique was developed that integrated hydrate-based gas separation and chemical absorption for the sweetening of natural gas with high H₂S and CO₂ contents. To evaluate the performance of this new integrated method, technical comparisons based on simulation and experimental data were conducted. The results showed that the new integrated method could effectively remove sour components, which resulted in the product gas being able to meet the sales gas specifications. Additionally, the integrated technique consumed much less energy than the traditional MDEA absorption process and its amine regeneration duty was only 42% that of the MDEA method. What is more, upon an economical evaluation being performed, it was shown that the integrated technique tremendously reduced the investment and operating cost.

Molecular insight into carbon dioxide hydrate formation from saline solution

Carbon dioxide hydrate has been intensively investigated in recent years because of its potential use as gas and heat storage materials. To understand the hydrate formation mechanisms, the crystallization of CO₂ hydrate from NaCl solutions was simulated at a molecular level. The influence of temperature, pressure, salt concentration and CO₂ concentration on CO₂ hydrate formation was evaluated. Results showed that the amount of the newly formed hydrate cages pressure went through a fast linear growth period followed by a relatively stable period. Pressure had little effect on CO₂ hydrate formation and temperature had a significant influence. The linear growth rate was greatly reduced as the temperature dropped from 255 to 235 K. The salt ion pairs could inhibit CO₂ hydrate formation, suggesting that we should choose the lower salinity areas if we want to storage CO₂ as gas hydrates in the seabed sediments. The observations in this study can provide theoretical support for the micro mechanism of hydrate formation, and provide a theoretical reference for the technology of hydrate based CO₂ storage.

In the process of the carbon dioxide hydrate formation in NaCl solution, it could form 5¹², 5¹²6² and 5¹²6³ cages, and the 5¹²6² cage and 5¹² cage number ratio was slightly above 3 : 1.

Formation Kinetics of the Mixed Cyclopentane—Carbon Dioxide Hydrates in Aqueous Sodium Chloride Solutions

Hydrate formation from cyclopentane (CP) and carbon dioxide was measured at 281 K by powder X-ray diffraction (PXRD) and macroscopic methods. The effect of initial pressure and CP mass fraction in liquid phase was analyzed. The results showed that hydrate formation was assumed to start with the nucleation of the mixed CP-CO2 hydrate with small fraction of CO2 followed by a large continuous CO2 adsorption. Initial pressure was found to have a positive correlation with the total CO2 consumptions when the initial pressure was below 2.5 MPa. However, the total CO2 consumptions dropped by over a half as the initial pressure was 3.0 MPa. PXRD revealed that all the hydrate samples formed at different initial pressures were structure II. The CO2 consumptions were assumed to be inhibited by the competitive occupation of 51264 cages between CP and CO2 molecules when the initial pressure was above 2.5 MPa. The CO2 consumptions were also found to be reduced as the CP mass fraction was above 0.25. An excess of CP molecules was not assumed to strengthen the formation of the mixed CP-CO2 hydrates at the initial stage, but increased the thickness of liquid CP film at aqueous brine and hydrate particles, which increased the diffusion resistance of CO2 molecules. Therefore, the suitable initial pressure and the CP mass fraction for the mixed CP-CO2 hydrate formation should be around 2.5 MPa and 0.2, respectively.

Gas hydrates in sustainable chemistry

This review includes the current state of the art understanding and advances in technical developments about various fields of gas hydrates, which are combined with expert perspectives and analyses.

Oil and gas companies' low-carbon emission transition to integrated energy companies

In recent years, with the emphasis on environmental protection, the global energy landscape is changing: the proportion of traditional energy is gradually decreasing, and renewable energy are developing rapidly. In this context, the oil and gas company is also in the early stages of the low-carbon emission energy transition. However, this concept is relatively new for many oil and gas companies. Thus, this paper aims to introduce the low-carbon emission transition practices of several large oil and gas companies so that more companies can learn from the experience. This paper summarizes the transition targets, investment, and actions of some large oil and gas companies employing enterprise surveys, and analyses the low-carbon transition paths, opportunities, and challenges. The analysis shows that (1) vigorous development of natural gas business is the first step for oil and gas companies to transition to low-carbon emission stage; (2) increasing investment in renewable energy is a long-term action of oil and gas companies and the key to transforming oil and gas companies into integrated energy companies; (3) oil and gas companies should have rich experience in developing geothermal energy. In addition, the paper also proposes policy recommendations for the low-carbon transition of oil and gas companies.