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Ignition is one of the most important techniques used to ignite crude oil during the in-situ combustion process. However, one problem with this process is that the ignition time is long. To address this problem, this study provides a solution by using a thermal insulation structure consisting of three layers placed inside an electric heater. To inv...
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... addition, as the air injection rate increases, the time to ignite the oil sand decreases because the reaction rates of crude oil and oxygen increase with the increase of the air injection rate, thus reducing the ignition time. with insulation structure without insulation structure Figure 5 Influence of the air injection rate and thermal insulation structure on the ignition time t1 is the ignition time with the thermal insulation structure, s; t0 is the ignition time without the thermal insulation structure, s. Table 5 shows the growth rate of the ignition efficiency at different air injection rates. As observed from Table 5, the ignition efficiency is obviously improved, with an average improvement of approximately 28%. ...Context 2
... 5 shows the growth rate of the ignition efficiency at different air injection rates. As observed from Table 5, the ignition efficiency is obviously improved, with an average improvement of approximately 28%. For an air injection rate of 1 L/min, the growth rate of the ignition efficiency is lower than those of the other air injection rates because the oxygen concentration in the combustion tube is relatively low and the oxidation reaction rates of crude oil and air are slow, resulting in a long ignition time. ...Citations
... The total time required to heat the closed chamber to a certain level can be calculated using Eqs. (1)-(6) [32,33]. ...
Managing the temperature inside greenhouses is essential for optimum crop growth and the control of diseases and physiological disorders in plants. In large-sized greenhouses, the automatic operation of small-sized multipoint suspension-type heating modules can facilitate better site-specific temperature management by providing favorable uniformity. The objective of this study was to evaluate efficiency of candidate heating modules before the prototype fabrication of a small-sized heating module for smart greenhouses temperature management. Three different heating modules (i.e., finned tubular (FT), fin element positive temperature coefficient (PTCf), and honeycomb positive temperature coefficient (PTCh)) were tested inside a closed chamber (41 m3) and a small greenhouse (98 m3). A wireless sensor network (WSN) was established to monitor the inside environment, operate heating modules, and detect their operational status. In the closed chamber, the PTCf module exhibited a temperature rise rate 8.59% and 7.36% higher than those of the FT and PTCh modules, respectively, while maintaining a superior average temperature variability range of 1.43 – 5.16 (±0.55 – ±0.85) °C. The elapsed times for the three modules were 12.70%, 8.30%, and 10.85% longer than their calculated times, indicating the effectiveness of the heating modules in regulating the environment. During the tests in the small greenhouse, the PTCf module demonstrated a greater average temperature difference between the inside and outside, followed by the FT and PTCh modules. The respective average temperature variability levels inside the greenhouse were recorded as 5.80 – 10.15 (±1.30 – ±2.68) °C, 4.90 – 8.93 (±1.35 – ±2.36) °C, and 4.86 – 9.38 (±1.25 – ±2.35) °C for the three modules. The performance of the PTCf module was better compared to the other two during the experiments in terms of efficiency and maintaining uniformity. However, large-scale field tests with multiple heating modules are required to verify these experimental findings.
... Sezai et al. [24] improved performance by using dual heaters in a storage-type domestic electric water heater. Li et al. [25] studied the ignition time of electric heaters experimentally, and a thermal insulation structure consisting of three layers was used to reduce the heat loss of electric heaters. Liu et al. [26] proposed an instant water heater based on a dual-helical tube and screw tape for application in faucets. ...
In this study, a waste heat recovery method based on the thermoelectric effect was proposed to improve the thermal performance of electric water heaters. The method collected the surplus thermal energy in the high- temperature zone and released heat for reuse in the low-temperature zone through the thermoelectric element. A heat-recovery device using a thermoelectric element was designed and conducted experimentally to verify the method’s feasibility and energy conservation effect. The device performance of heat absorption and
heat release were investigated under various working thermal states. The experimental results showed that the
heating COP of the system could be improved to 1.2–2.3 under different temperature conditions, which means
the device can save energy than using electric power directly. The heat flux through the device can be actively
controlled for an optimal effect of heat recovery. The source-sink matching effect of the device was investigated,
and the results indicated that the device’s energy efficiency could be higher than 75%. The thermal performance
of an improved electric water heater using the heat recovery device was investigated numerically under a specific
working condition. The results verified that the heat recovery device reduced heat dissipation and simulta-
neously increased the temperature of the water outlet.
... Due to the abundant gas sources and low operation cost, air injection technology has been widely used in the exploitation of low permeability reservoirs [11]. However, in the process of air injection in light oil reservoir, there is a gas extraction effect, which makes the light hydrocarbon components in crude oil evaporate and form a flammable mixture with oxygen in the wellbore [12]. ...
Air injection is an important method for tertiary oil recovery. Air with high temperature and pressure will affect the properties of crude oil. It will also affect the oxidation reaction between crude oil and oxygen. As a result, the liquidity of crude oil and safety of air injection process will be influenced. In this study, experiments on oil samples from Liaohe oilfield were carried out to investigate the effect of high temperature and pressure on the properties of crude oil. The viscosity and component change of crude oil were analyzed. Besides, the change of gas components after reaction was also investigated. The results showed that the viscosity of crude oil increased with the increase of reaction time, which was caused by the increase of asphaltene in crude oil. The viscosity of crude oil also showed an upward trend with the increase of temperature and pressure. Interestingly, when the pressure reached 20 MPa, the viscosity of crude oil experienced a decrease. Besides, the oxygen concentration declined as the temperature rose up from 80 °C to 140 °C. Therefore, to ensure safety and better liquidity of crude oil, the temperature and pressure should be controlled in certain range during air injection.
... The middle side of the vessel had two electrodes for connecting with the electric igniter. Additionally, there was a heating sleeve with a thermal insulation structure [33] that can be heated to 350 °C to ensure the accuracy of temperature control. Additionally, a thermocouple and a pressure sensor were attached to the vessel to measure the temperature and pressure inside the vessel. ...
While injecting air into an oil reservoir for enhanced oil recovery, there may be explosion risks at reservoir conditions including elevated pressures and temperatures. A high-pressure experimental apparatus was developed to investigate the flammability limits of natural gas/air mixtures at reservoir conditions with pressure ranging from 1 MPa to 15 MPa and temperature ranging from 40 °C to 120 °C. The results showed that an increase in initial pressure or temperature leads to a wider flammability limit range. Specifically, the upper flammability limit (UFL) shows a logarithmic pressure dependence, and the lower flammability limit (LFL) is linearly dependent on pressure. The UFL shows a linear dependence on temperature, whereas the LFL is slightly affected by temperature. Moreover, it was also found that when the pressure is between 1 MPa and 5 MPa, the effect of temperature on the UFL is affected by pressure. Temperature has little influence on the relationship between pressure and UFL. These results improve our understanding of the fire and explosion hazards of natural gas in oil recovery processes.
In the process of removing hydrogen sulfide from natural gas, it is easy to form an accumulation of hydrogen sulfide in the gas phase space of the liquid sulfur tank, which can lead to an explosion accident. In order to avoid an explosion accident in the liquid sulfur tank, the flammability limit of hydrogen sulfide needs to be determined. Thus, it can be effectively monitored and targeted protective measures can be taken. The temperature of the gas phase space of the liquid sulfur tank exceeds 100 °C and sulfur vapor is present. In such a complex environment, there is no relevant study on the flammability limit of hydrogen sulfide. In this study, a system used to test the flammability limit of hydrogen sulfide in high temperature environment was established. In addition, the sulfur vapor environment can also be simulated. The experiments were carried out at temperature from 25 °C to 160 °C. The effect of temperature and sulfur vapor on the flammability limit of hydrogen sulfide was analyzed. The results showed that the upper flammability limit of hydrogen sulfide increases and the lower flammability limit decreases with the increase of the initial temperature. In addition, the effect of initial temperature on the flammability limit of hydrogen sulfide gradually diminishes in an exponential relationship. It was also found that the presence of sulfur vapor makes the flammability limit range of hydrogen sulfide narrower, but the effect is relatively weak. The results of this study can provide a basis for the detection of hydrogen sulfide concentration in the gas phase space of liquid sulfur tank, thus enhancing the safety of the production process.
Ignition design of air injection wells is the crucial factor to a successful in-situ combustion. In this paper, experimental studies were carried out on post steam flooding wells at JIN-91 of Liaohe oilfield for improving ignition success rate. The experiments were conducted by a high temperature-pressure ignition device specifically designed for in-situ combustion, and the effects of various parameters were investigated by factorial experiments. The results showed that the ignition temperature was reduced and the ignition time was shortened due to three factors: heating temperature, reservoir pressure, and clay minerals. When heating temperature exceeded 360 °C, experimental pressure was higher than 4.0 MPa, and 10% of montmorillonite clay was added, the crude oil samples could be ignited rapidly. According to the factorial results, the most effective method to shorten ignition time is by increasing heating temperature, the safest method to reduce crude oil spontaneous combustion temperature and to shorten ignition time is by applying clay minerals, and reservoir pressure is the key factor for safety operation during ignition operation. These results will provide experimental theoretical guidance for high efficiency ignition, process optimization, and safe implementation of crude oil reservoir, they also will deliver tech support for the high efficiency operation of in-situ combustion.
High pressure air injection is an important method for oil recovery. In this process, due to exist of combustible gas and oxygen, the wellbore explosion accident may happen. To solve the problem, the optimal method is to control the oxygen concentration in the wellbore. Thus, it needs to investigate the limiting oxygen concentration (LOC) of combustible gas at high pressures and temperatures. In this study, experiments were carried out to investigate the LOC of combustible gas at pressures from 1 MPa to 15 MPa and temperatures from 40 °C to 120 °C. The influence of pressure and temperature on LOC was analyzed. The results showed that the LOC of combustible gas declines a lot as the initial pressure and temperature increases. At 15 MPa and 120 °C, the LOC drops up to 8.21%. It was also found that the LOC is exponentially and linearly dependent on initial pressure and temperature, respectively. Besides, the empirical formulas were proposed to calculate the LOC at different conditions. Based on the present results, the standard for controlling the oxygen concentration in the wellbore was confirmed. As a result, the allowable oxygen concentration in the wellbore at different conditions can be determined. Therefore, the results of this study can help to avoid the wellbore explosion and ensure safety during air injection process.
Aiming at the energy-saving of water heater, a novel technology which can enhance thermal insulation and improve energy efficiency simultaneously has been proposed, and its source-sink matching strategy has been investigated in this study. A source-sink heat transfer device is designed, and the optimal installment position of this device has been determined through theoretical and experimental methods, besides that, the rationality of matching strategy is also evaluated. Experimental results and exergy analysis show that the optimal installment position and suitable source-sink matching strategy facilitate to boost the energy-saving effect, lower production cost and conform to the miniaturization trend of water heater. In addition, the experimental results reveal that although adiabatic measures and energy efficiency improvement measures adopted by this technology are different, the ultimate direction is the same, both of which are to directly or indirectly reduce the temperature of heat source, which can provide significant reference for practical engineering application.
