Nitrogen Injection Research Articles

Study of Internal Flow in a Liquid Nitrogen Flow Decelerator Through Swirl Effect Consisting of a Jet-Type Cryogenic Injection System for Food Freezing

This article addresses the study of internal flow dynamics within a cryogenic chamber designed for freezing food using liquid nitrogen injection. The chamber features a circular section with strategically placed jet-type atomizers for this purpose. The primary objective is to extend the residence time of the cryogenic fluid within the chamber to ensure uniform and effective freezing of the passing food items. This is achieved by inducing a swirl effect through strategic deceleration of the flow using the atomizers. The meticulous placement of these atomizers at periodic intervals along the internal walls of the cylindrical chamber ensures prolonged recirculation of the internal flow. Internal temperature analysis is crucial to ensure the freezing process. The study is supported by numerical analysis in CFD ANSYS to assess the dynamics of the swirl effect and parameters associated with the nitrogen–air interface, from which we obtain a sophisticated analysis thanks to the design of a hexahedral mesh made in greater detail in ICEM CFD. This approach aims to understand internal flow behavior and its correlation with the complexity of cryogenic system design, utilizing variable nitrogen-injection pressures and strategic atomizer placement as fundamental parameters to optimize system design.

Asphyxiation effect analysis in confined space of B-type oil pool fire under pressure changes of nitrogen extinguishing system

Nitrogen fire extinguishing system has a significant development space in the modern fire extinguishing because of its environmental protection, energy saving and high stability. To further broaden the application field of nitrogen fire extinguishing system, a shrinkage size model was used as the research object and combined with simulated flow field analysis. A nitrogen fire extinguishing system was characterized for alcohol fire extinguishing efficacy using nitrogen injection pressure as a variable and parameters such as extinguishing time, oxygen concentration, and temperature. Furthermore, diesel and gasoline were used as combustible materials to verify the extinguishing efficacy of pressure variation on Class B oil pool fires. It was found that with the increase of nitrogen injection pressure, the nitrogen extinguishing efficacy gradually increased and then leveled off in the confined space. The asphyxiating oxygen concentrations were 12.2%, 13.2% and 13.7% for ethanol, diesel and gasoline, respectively. Asphyxiating oxygen concentration above limiting oxygen concentration (LOC). For extinguishing Class B oil pool fires in confined spaces, nitrogen extinguishing systems showed excellent fire extinguishing efficiency. They had specific application prospects in the field of protecting underground oil storage tanks and oil wells.

Experimental Study on Enhanced Oil Recovery of Shallow Super-Heavy Oil in the Late Stage of the Multi-Cycle Huff and Puff Process

The shallow, thin super-heavy oil reservoir demonstrates certain characteristics, such as shallow reservoir depths, low-formation temperature, and high crude oil viscosity at reservoir temperatures. In the current production process, the central area of P601 is undergoing high-frequency huff and puff operations, facing certain problems such as decreasing production, low recovery rates, and rapid depletion of formation pressure. Through physical simulation experiments, the various elements of HDNS-enhanced oil recovery technology were analyzed. Nitrogen plus an oil-soluble viscosity reducer can improve the thermal recovery and development effect of super-heavy oil. With the addition of the viscosity-reducing slug, the recovery rate of steam flooding was 58.61%, which was 23.32% higher than that of pure steam flooding; after adding the 0.8 PV nitrogen slug, the recovery rate increased to 76.48%. With the increased nitrogen injection dosage, the water breakthrough time was extended, the water cut decreased, and the recovery rate increased. Nitrogen also plays a role in profile control and plugging within the reservoir; this function can effectively increase the heating range, increase steam sweep efficiency, and reduce water cut. So, the synergistic effects of steam, nitrogen, and viscosity-reducing agents are good. This technology enhances the development of shallow-layer heavy oil reservoirs, and subsequent development technologies are being compared and studied to ensure the sustainable development of super-heavy oil reservoirs.

ENSURING THE SEALING OF GAS WELLS EQUIPPED WITH LINER

The current problem of fountain safety, which affects the further well operation, namely the problem of their sealing, is considered. Traditional and modern technologies used to ensure the sealing of gas wells (including offshore wells), equipped with liners that simultaneously cover gas and water layers, are analysed. The issue of mandatory testing of casing strings in two ways is considered in more detail: pressing after lowering and cementing of the liner; lowering the level of the working fluid in the wellbore. These tests are intended to detect the fact of the well sealing and its suitability for further operation, or to detect the sealing fact and at the same time collect data for the analysis of the further action plan to overcome the consequences of such sealing. The sequence of testing casing strings using vaporizer-type coiled tubing installation that consumes liquefied nitrogen is considered. Schemes of well tying during tests of the production casing are presented. The peculiarities of the pressing process when nitrogen is injected into the annular space and into the tubing are noted. As a result of calculating of nitrogen injection pressure (the permissible value of which was 80 % of the testing pressure of the production casing) and the permissible pressure in the casing pipes, a comparative graph was constructed. The analysis of the received data confirmed the feasibility of pressing using a coiled tubing unit when pumping liquid into the tubing, as a result of exceeding the permissible pressure value at a depth of 3500 m. The need to use an operational packer, which was installed in the pipeline at the level between the head of the liner and the productive horizon, was determined. The necessity of perforating the liner through the inner space of the tubing using a hydraulic sandblasting perforator was confirmed.

Mechanism evaluation of edge-water invasion mitigation by low temperature oxidation (LTO) coking in VHSD heavy oil reservoirs: A comparative study with traditional plugging techniques

Heavy oil is one of the globally important unconventional oil and gas resources, and its development faces the challenge of water invasion. The numerical model of a heavy oil reservoir with edge water is established and validated by field data and physical experiments. An evaluation model for selecting water invasion mitigation measures for different targets is established. The mechanisms of mitigating water invasion in the vertical-horizontal well steam drive (VHSD) heavy oil reservoir by cold-water injection, gel injection, nitrogen injection, and “Air + LTO” coking are investigated. The advantages of the “Air + LTO” coking technology in mitigating water invasion are elucidated. The importance of LTO reaction for water invasion mitigation is emphasized. The results show: (1) the edge water flows into the reservoir along the drainage interface of the steam chamber first and forms large water invasion channels in the heated crude oil region in the middle part of the reservoir; (2) the cold-water injection reduces the oil recovery factor by 3 %, the nitrogen injection increases it by 16.3 %, the gel injection improves it by 11.5 % and the “Air + LTO” coking technology enhances it by 24.1 %; (3) after air injection, the coke deposition effectively plugs the water invasion channels in the middle of the reservoir. This research provides a new perspective for mitigating water invasion and improving the oil recovery factor in heavy oil reservoirs with edge water, demonstrating the potential value and feasibility of the “Air + LTO” coking technology.

Visualization and Simulation of Foam-Assisted Gas Drive Mechanism in Surface Karst Slit-Hole Type Reservoirs

Nitrogen injection technology has become an important production technology after water injection development in the karst fracture-vuggy reservoir in Tahe Oilfield. However, due to the influence of reservoir heterogeneity and the high mobility of gas fluid, nitrogen easily forms a dominant channel and gas channeling occurs, and the recovery effect time is short. Based on this, a visual surface karst model is designed and created to study nitrogen foam-assisted gas drive. The results show that after gas channeling occurs in the dominant channel of nitrogen flooding, foam injection-assisted gas flooding can improve oil recovery. In the longitudinal direction, foam-assisted gas drive mainly displaces the remaining oil because of gravity differentiation and the reduction of oil–water interfacial tension. In the horizontal direction, foam-assisted gas drive is mainly used to block the large pore cracks and dominant channels, promote the gas to turn into large tortuous and small cracks, and expand the swept efficiency of the gas. After forming the dominant channel, injecting 0.3 pv salt-sensitive foam with a gas–liquid ratio of 2:1 in the middle of the gas channel can improve the recovery rate of the model from 4% to about 25%, and the recovery rate can be increased by about 20%, which improves the effect of gas flushing and improves the development efficiency of the oil field at the same time.

Evaluation of Nong’an oil shale reservoir stimulation based on nitrogen injection

Reservoir stimulation for in-situ oil shale conversion employed hydraulic fracturing, as demonstrated in the Nong’an oil shale in-situ conversion project. This study examines the extent of reservoir stimulation and the associated changes in permeability. Hydraulic fracturing significantly increased the reservoir stimulation volume, raising the permeability in the stimulated area to 324.6 mD. Subsequent water replacement involved injecting lower-temperature nitrogen, which mitigated volume shrinkage and closed microfractures. However, this process reduced permeability by 80.54%, decreasing the seepage area to 2660.7 m3. The gas injection and mining process encompassed two stages: warming and cracking. The former aimed to enhance the drying of the formation in the stimulation area, restoring 22.87% of the permeability of the original area. The latter stage facilitated organic matter decomposition to release hydrocarbons, increasing the permeability of the reformed region to 704.842 mD. The reservoir-stimulated area can be categorized into cracking, high seepage, or low seepage zones, depending on the difficulty of injected gas flow and the extent of high-temperature influence.

Numerical Investigation of coupling hazard zone of coal spontaneous combustion and gas in gob for high-gas mines

As coal mining operations continue to deepen, the frequency of coal spontaneous combustion (CSC) and gas explosion disasters in high-gas mines is increasing. Understanding the distribution patterns of CSC and gas compound disaster zones in the gob during the extraction process is crucial for reducing the risks of combustion and explosion. This study focuses on the 201 working face of the Shuanglong Coal Mine, where a multi-physical field coupling model of pressure, temperature, gas seepage, and diffusion was established to investigate the evolution characteristics of compound disaster zones and propose corresponding prevention and control measures. The results demonstrate that the area with the most severe composite hazard is mainly located at the return roadway side, extending to the middle of the gob. With increased ventilation volume and advance rate, the area of the CSC and gas coupling hazard zone expands continuously. By implementing measures such as brattice cloth and nitrogen injection, the areas of spontaneous combustion and CH4 explosion zones were reduced by 53.6 % and 49.5 %, respectively, effectively controlling the extent of the compound disaster zone and eliminating the risk of gas explosions.

Research and Practice on EOR Development Strategy of Water Drive Followed by Gas Drive in Fractured Carbonate Reservoir in Bohai Sea

Abstract Focusing on the issues of high comprehensive water cut and low recovery degree following water flooding in the CFD 2-2 carbonate buried hill reservoir in the Bohai Sea, the productivity variation law, water cut rising characteristics and development effect of horizontal wells were analyzed based on different types of reservoir classification systems. The reservoir numerical simulation model of dual media coupling of matrix and fracture is established, and the analysis is done on the matrix and fracture production state, the distribution pattern of the residual oil, and the primary governing parameters.. The physical simulation experiment of water flooding to gas flooding is carried out. In conjunction with the distribution characteristics of fractures and matrix residual oil in low, middle and upper tiers of the framework, the development strategy of nitrogen injection pressure water cone in low water-flooded area, nitrogen flooding in middle inter-well residual oil enrichment area and nitrogen huff and puff in high well point residual oil enrichment area is put forward. The recovery rate is increased by 5-8 %, which successfully enhances the high water cut stage development effect, and provides reference for similar oilfield development.

Simulation of edge water invasion mitigation of the SAGD chamber by low temperature oxidation (LTO) coking air injection and optimization of operating parameters

During the long-term use of steam assisted gravity drainage (SAGD) in oil fields, the continuous expansion of the steam chamber often leads to edge water invasion, which significantly reduces thermal efficiency and oil production rate. To address this challenge, we hypothesize that a low temperature oxidation (LTO) coke formation air injection method may alleviate edge water invasion. To test our hypothesis, we developed a numerical SAGD model tailored to a typical SAGD field, the Guantao Du84 block in the Liaohe Oilfield, China. The model incorporates a four-step coke generation kinetics and considers the complexity of coke distribution. Our results reveal that coke generation (1) shifts the direction of edge water flow from the steam chamber to a vertical downward direction, (2) causes pore clogging, resulting in reduced flow velocity, (3) leads to reduced porosity and water cut, significantly improving oil recovery as compared to nitrogen injection (e.g., by 18.2% in the Guantao Du84 block), and (4) allows for proactive establishment of coke zones before the water cut reaches 85%. Through this numerical study, we investigate the feasibility of implementing the method of LTO coking air injection in SAGD fields and provide insights into its optimization.

Technology Progress in High-Frequency Electromagnetic In Situ Thermal Recovery of Heavy Oil and Its Prospects in Low-Carbon Situations

Heavy oil resources are abundant globally, holding immense development potential. However, conventional thermal recovery methods such as steam injection are plagued by high heat loss, substantial carbon emissions, and significant water consumption, making them incompatible with carbon reduction goals and the sustainable socioeconomic development demands. A new method of high-frequency electromagnetic in situ heating, which targets polar molecules, can convert electromagnetic energy into heat so as to achieve rapid volumetric heating of the reservoir. This method has the potential to overcome the drawbacks of traditional techniques. Nevertheless, it faces significant drawbacks such as limited heating range and inadequate energy supply during later production stages, which necessitates auxiliary enhancement measures. Various enhancement measures have been reported, including nitrogen injection, hydrocarbon solvent injection, or the use of nano-metal oxide injections. These methods are hindered by issues such as pure nitrogen being easy to breakthrough, high costs, and metal pollution. Through extensive literature review, this article charts the evolution of high-frequency electromagnetic in situ heating technology for heavy oil and the current understanding of the coupled heat and mass transfer mechanisms underlying this technology. Moreover, based on a profound analysis of the technology’s progression trends, this work introduces a new direction: CO2-N2 co-injection as an enhancement strategy for high-frequency electromagnetic in situ heavy oil recovery. There is promising potential for the development of new technologies in the future that combine high efficiency, low carbon emissions, environmental friendliness, economic viability, and energy conservation. Furthermore, some research prospects in low-carbon situations and challenges for the new technology in future are presented in detail. All in all, the contribution of the paper lies in the summarizing of some main drawbacks of current enhanced electromagnetic in situ thermal recovery methods, and presents a novel research direction of using CO2-N2 co-injection as an enhancement strategy based on its current research status in low-carbon situations.

Study on multi-field coupling characteristics of underground coal combustion and nitrogen injection parameter optimization

Underground coal fires, which are widely distributed and cause serious resource waste and environmental hazards, have become a common concern of the international community. This paper aims to reveal the mechanism of coal spontaneous combustion and the expansion law of underground coal fires. A void rate model from the goaf to the ground surface and a multi-field coupling model for underground coal fires were established. Based on which, the combustion process from the beginning of oxidation to the formation of large-scale fire of the remaining coal in goaf was analyzed. Furthermore, the evolution law of underground coal fire after nitrogen injection and the influence of different nitrogen injection parameters were analyzed. The results show that the coal spontaneous combustion can be divided into three stages: slow reaction stage (stage Ⅰ), violent combustion stage (stage Ⅱ), and stable combustion stage (stage Ⅲ), and the transformation of different stages is mainly controlled by the oxidation reaction rate of coal. To obtain the optimal parameters for nitrogen injection for fire suppression, the fire extinguishing efficiency concerning nitrogen injection time, nitrogen injection amount and nitrogen injection position, as well as the distribution law of nitrogen in rock strata were analyzed. Through range analysis, it is determined that the most effective fire extinguishing occurs with the injection rate of 0.15 m3/s in stage I, and the injection position has little influence on the fire extinguishing effect. This understanding contributes to a deeper understanding of the multi-field coupling mechanism of underground coal fires and provides a guidance for extinguishing and preventing underground coal fires.

Optimization of ammonia production unit using polymeric membrane: Re-design of ammonia synthesis reactor feeding strategy and methane removal

The optimization of an industrial-scale ammonia production reactor is studied in the present work by re-designing the ammonia synthesis reactor and using a membrane. After simultaneous modeling and simulation of the ammonia synthesis reactor and the membrane unit, the maximization of ammonia production rate was investigated. The simulation results for a single pass through the reactor showed that removing methane, increasing the nitrogen flow, and combining these two cases increased ammonia production efficiency by 1 %, 15 %, and 19 %, respectively. Furthermore, for the reactor with the recycle stream, the efficiency of ammonia production can be increased by 2.74 % by re-designing the feeding strategy and optimization of the reactor. For this purpose, the PFMMD–CTFE copolymer membrane with a total area of 1550 m2 is required to separate methane, and the cellulose acetate membrane with a total area of 1343.9 m2 should be used to provide the required amount of nitrogen injection.

Coal deformation characteristics during methane displacement by pulsed nitrogen injection: New method of using pulsed energy to improve coal permeability

The displacement of methane by injecting nitrogen is an effective method for improving extraction efficiency in low-permeability coal seams. By conducting the experiments on uniform/pulsed pressure nitrogen injection for methane displacement (UPNI-MD/PPNI-MD), the coal deformation characteristics are quantitatively characterized, and the coal deformation mechanism is discussed. The results show that the technology of methane displacement by PPNI-MD is more effective in enhancing the permeability of low-permeability coal seams. The pressure of nitrogen injection and the amount of methane/nitrogen adsorption are crucial factors affecting the coal deformation during the process of UPNI-MD/PPNI-MD. The erosive effect of methane adsorption on the mechanical properties of coal decreases, while the erosive effect of nitrogen adsorption on the mechanical properties of coal shows a “wave-like” variation in the case of PPNI-MD. The application of PPNI-MD technology can effectively decrease the coal expansion deformation while undergoing the methane displacement process. Nitrogen injection to displace methane breaks the system energy balance of coal, resulting in deformation. And the coal deformation during nitrogen injection for methane displacement depends on the energy carried by the injected nitrogen, the energy change during gas competitive adsorption and the heat exchange between nitrogen and coal. The effective stress of coal depends on the change in methane/nitrogen pressure. The mechanical properties of coal depend on the amount of methane/nitrogen adsorption and the pore pressure. High-energy nitrogen damage to coal during the process of PPNI-MD is manifested in coal deformation caused by methane/nitrogen pressure, coal deformation caused by methane/nitrogen adsorption, and damage to coal mechanical properties caused by methane/nitrogen adsorption.

Research on the technology of uniformly injecting nitrogen into the porous long pipes in the gob of the gob-side entry retaining mining mode with roof cutting and pressure relief

The implementation of the Gob-Side Entry Retaining Mining Mode with Roof Cutting and Pressure Relief (GERRCPR) results in the gob connecting to the retaining roadway, creating an open space that causes significant air leakage and increases the risk of spontaneous combustion. A study was conducted during the implementation of the GERRCPR in the Xiaonan Coal Mine N1-1502 working face to investigate spontaneous combustion characteristics, along with fire prevention and extinguishing measures. To analyze gob airflow, Computational Fluid Dynamics (CFD) was employed to collect data on airflow conditions, O2 concentration, and temperature. Based on this, this study focuses on exploring the effects of nitrogen injection treatment under various rates and positions to optimize parameters for buried pipe nitrogen injection. Results indicated that within the GERRCPR, air leakage in the gob increased, leading to an increase in O2 concentration, expansion of the oxidation zone, and an elevated risk of spontaneous combustion. Air leakage primarily occurred from the retaining roadway and the working face near the intake-air roadway, peaking at a retaining roadway length of 500 m, with a flow rate of 226 m3/min. Following nitrogen injection treatment, the oxidation zone was significantly reduced, with optimal treatment achieved at a nitrogen injection depth of 70 m and a rate of 600 m3/h. Field monitoring data showed that the inertization measure of using porous long pipes, a nitrogen injection spacing of 30 m, and a nitrogen injection rate of 600 m3/h significantly decreased the O2 concentration within the gob. This reduction meets safety production requirements and outperforms the effectiveness of traditional buried-pipe nitrogen injection methods, thereby validating the simulation accuracy. Understanding the laws governing spontaneous coal combustion in the GERRCPR and enacting preventive measures for nitrogen injection can improve safety standards in mining operations. This proactive approach can effectively prevent spontaneous coal combustion accidents, resulting in substantial social benefits.

Development of a Graded Early Warning Index System and Identification of Critical Temperatures for Coal Spontaneous Combustion Using Composite Gas Characteristics.

Conventional single gas alarm method and coal spontaneous combustion three-stage alarm method have become increasingly inadequate to meet complex underground conditions. To address this issue, this study focuses on the coal in the goaf of the Z109 working face in the Donggucheng Mine as the research object. Through program-controlled heating experiments, the production of carbon monoxide and hydrocarbon gases during the coal oxidation process was determined, and the variation characteristics of gas ratios with temperature were further analyzed. The coal spontaneous combustion process was subdivided into seven small stages, and a quantitative composite parameter coal spontaneous combustion grading warning system was formulated. Based on its characteristics, measures to be taken under different warning levels were proposed, and it was determined that 120, 140, and 160 °C are the key temperatures for coal spontaneous combustion prevention and control in the Z109 working face of Donggucheng Mine. By using numerical simulation, the optimal nitrogen injection position for the working face was determined and the on-site fire prevention and extinguishing measures were optimized, providing insights into the establishment of a coal mine spontaneous combustion warning system.

Research on the Low-Temperature Oxygen Consumption and Low-Oxygen Gas Emission Law in Goaf of Ultrathick Coal Seams.

Low-oxygen (oxygen concentration below 18.5%) phenomena often occur in the top coal caving working face of ultrathick coal seams, posing a serious threat to the safety of workers. The characteristics of oxygen consumption and gas production at low-constant temperature and the corresponding functional group evolution of residual coal in goaf were studied by temperature-programmed and infrared spectrum experiments. The influence of different factors on the emission of low-oxygen gases was studied through numerical calculation. The results show that low-temperature oxygen consumption and gas production occurred when the coal was about 40 °C. When the temperature was constant, the oxygen consumption and gas production rate increased with the extension of time. In the early stage of coal oxidation, the aliphatic C-H components were attacked by oxygen molecules and reacted with them. The asymmetric methyl and methylene groups were more likely to oxidize and produce carbonyl compounds. With the increase of nitrogen injection, the overall width of the oxidation zone (oxygen concentration was defined as 10-18%) narrowed, and the range of the oxidation zone moved forward from the depth of the goaf. The oxygen concentration in the air return corner decreased gradually, and the low-oxygen area in the air return corner expanded gradually. The distance between the low-oxygen area of the working face and the air intake corner was gradually shortened. With the increase of air intake, the width of the oxidation zone increased and moved to the depth of goaf, and the degree of low oxygen in the air return corner increased. The research results are of great significance for the understanding and prevention of the low-oxygen phenomenon in ultrathick coal seams.

Research and application of continuous and precise nitrogen injection fire extinguishing technology in coal mines

To overcome shortcomings in traditional nitrogen injection fire prevention techniques, such as discontinuous nitrogen distribution, poor inerting effects, and severe waste of pipeline resources, a method for continuous and precise nitrogen injection fire extinguishing was proposed. To implement this method, this study utilizes FLUENT, FLAC 3D simulations, and principles of elasticity to determine the process and dynamic parameters of nitrogen injection. This information guides the selection, design, and manufacturing of equipment components, leading to the development of a novel “rotating towing type” continuous and precise nitrogen injection fire extinguishing equipment. Taking Wenzhuang 15,102 working face as an example, the inerting effect was compared and analyzed by using CO, Graham coefficient R2 (ΔCO/ΔO2), R3 (ΔCO/ΔCO2) and other quantitative indicators. The findings revealed following results: after deploying this equipment, there was an approximate 70 % reduction in CO concentration. Comparatively, R2 in the extraction area decreased by 45 % compared to the 0.38 % observed in the buried pipe nitrogen injection process. Similarly, the R3 values for the gob and upper corner were reduced by about 56 % and 60 %, respectively. These substantial improvements highlight the superior efficacy of the continuous and precise nitrogen injection fire extinguishing method for nitrogen injection and fire suppression in gobs.

Division of Main Geological and Engineering Controlling Types of Low-Production Coalbed Methane Well-Blocks and their Stimulation Measures.

At present, the identification of the main factors controlling low-production coalbed methane (CBM) wells and production enhancement measures does not consider geological and reservoir differences between individual wells and the CBM production effect of well groups simultaneously. In view of this, an evaluation index system suitable for use on inefficient well-blocks was established, which involves their geological resource potential, ground stress, coal structure, and comprehensive permeability under engineering influences from a systemic perspective. The main geological engineering types were determined by zoning superposition, and the corresponding stimulation measures were proposed. The evaluation results of the Shizhuang South Block in the Qinshui Basin show that the area of interest can be divided into Class I, II, and III potential areas, of which the Class II potential areas are subdivided into six blocks. In Zone I, the horizontal well infill method is preferred to increase the CBM production from well groups. At the current level of technology, it is difficult to gain economic benefits from Zone III. In Zone II, these stimulation measures such as the infilling method of staged fracturing horizontal wells, refracturing under supplementary injection holes, roof fracturing, the combined method of acidification and secondary fracturing or nitrogen injection and secondary fracturing, the combined method of acidification and controlled displacement secondary fracturing, and controlled displacement repetitive roof fracturing, among others, can be adopted.

Investigating the effect of the perturbation on emulsion polymerization of polystyrene nanospheres

Polystyrene nanospheres (PS spheres) were prepared by soap-less emulsion polymerization. The polymerization reaction with the monomer styrene was initiated using potassium persulfate under nitrogen injection. By adjusting the amount of precursor and the mixing speed of the stirrer during the polymerization process, PS particles of the expected appropriate size can be obtained. This work focuses on the effect of precursor concentration, reaction conditions and stirrer speed on particle size. Samples (C1–C6) were systematically prepared with varying amounts of K2S2O8 and C8H8. The particle sizes ranged from 69.9[Formula: see text]nm to 364.44[Formula: see text]nm. The calculated K2S2O8 to C8H8 ratio remained approximately constant across the samples. This supports the observed trend where increasing monomer concentration leads to larger particle sizes, indicative of bonded spheres. In addition, a correlation between stirring speed and PS bead size is found, with higher speeds resulting in smaller particles. Transmittance analysis of the filtered and sieved process samples showed that better polymerization conditions could be selected for PS beads up to 220[Formula: see text]nm at a stirring speed of 900[Formula: see text]rpm.