Electrical Heat Tracing Research Articles

Analysis of sensitivity to hydrate blockage risk in natural gas gathering pipeline

During the operational process of natural gas gathering and transmission pipelines, the formation of hydrates is highly probable, leading to uncontrolled movement and aggregation of hydrates. The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines, resulting in production reduction, shutdowns, and pressure build-ups. Consequently, a cascade of risks is prone to occur. To address this issue, this study focuses on the operational process of natural gas gathering and transmission pipelines, where a comprehensive framework is established. This framework includes theoretical models for pipeline temperature distribution, pipeline pressure distribution, multiphase flow within the pipeline, hydrate blockage, and numerical solution methods. By analyzing the influence of inlet temperature, inlet pressure, and terminal pressure on hydrate formation within the pipeline, the sensitivity patterns of hydrate blockage risks are derived. The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate, potentially mitigating pipeline blockage during natural gas transportation. Furthermore, an increase in inlet temperature and terminal pressure, and a decrease in inlet pressure, results in a displacement of the most probable location for hydrate blockage towards the terminal station. However, it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system, contradicting the operational goal of energy efficiency and reduction of energy consumption. Consequently, for high-pressure gathering pipelines, measures such as raising the inlet temperature or employing inhibitors, electrical heat tracing, and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation. Moreover, considering abnormal conditions such as gas well production and pipeline network shutdowns, which could potentially trigger hydrate formation, the installation of methanol injection connectors remains necessary to ensure production safety.

Challenges & Improvised Methods for a Successful Electrical Heat Tracing Design & Engineering on A Mega-Size Project

Challenges & Improvised Methods for a Successful Electrical Heat Tracing Design & Engineering on A Mega-Size Project

Uniform Thermal Energy Distribution Scheme for Wireless Heat Transfer System Based on Inherent Topology and Thermal Coupling

The wireless heat transfer (WHT) system is proposed to ensure the reliability and flexibility of the electrical heat tracing for domestic and industrial applications. In this article, the inherent coupling relationship among coil dimension, resistance, distance, and inductance of a WHT system is investigated, which illustrates the intrinsic link between thermal energy and electromagnetic feature of the WHT system under multiple mediums. Besides, the magnitude and distribution of the thermal energy among different coils are analyzed according to equivalent circuits and magnetic coupling mechanisms. For further studying the power distribution characteristic, the power flow model of the multiple coil system is established. On this basis, the uniform thermal energy distribution scheme of the WHT system is proposed to ensure all coils have equal heating power. Moreover, the heating power in the partial compensation condition is also investigated. The result indicates the compensation states of the transmitter coil only affect the magnitude of the heating power. Thus, the transmitter coil compensation states which can be used to adjust the heating capacity of the WHT system. The simulation and experiments are carried out to validate the feasibility of the proposed uniform thermal energy distribution scheme.

Coupled Analysis of Thermofluid-Structure Field for Thermal Properties of Early-Age Concrete Influenced by Electric Heating System

When heat energy is transferred to concrete through energy conversion by an electric heating system, the overall thermal performance of the early-age concrete is affected by the local high temperature of the concrete. This, in turn, affects the accuracy of the prediction and calculation of concrete deformation. Concrete thermal physical parameter models considering the mutual influence of heat and humidity were established to clarify the influence of an electric heat tracing system on the heat transfer performance of concrete at an early age, based on the concepts of equivalent age and hydration degree. Additionally, the COMSOL numerical simulation software was used for realizing the numerical solution of concrete heat transfer. The research indicates that the degree of hydration is affected by the heating provided by the electric heat tracing system. When curing for 40 h, the degree of hydration approaches 0.82 and remains unchanged, which indicates that the hydration of cement was almost complete in less than 2 days. The specific heat value of concrete in the early stage was significantly affected by electric heat tracing. This value of concrete at a high initial temperature was larger than that at a low temperature, while the specific heat of each point in the later stage tended to be the same. The thermal conductivity was significantly affected by the local electrical heating. The higher the temperature was, the lower the thermal conductivity was, which remained stable for two days under the influence of temperature. The key contribution of this research is to provide a coupling model for concrete curing. The findings from the study also provide industry practitioners with a comprehensive guide regarding the specific applications of the electric heating system in early-age concrete curing.

Flow assurance, simulation of wax deposition for Rawat field using PIPSIM software

One of the most relevant flow assurance issues in oil transportation is indeed the phenomena of wax deposition. Wax deposition occurs when the temperature along the pipeline falls below a point where it is described as Wax Appearance Temperature (WAT) The deposition may cause a lot of problems to the industry and definitely will involve expensive cause to overcome the problem. The flow system was built for Rawat field which is consists of (13) wells in the Rawat/Wateesh field. In this studies a series of cases were carried out at different flow rates, ambient temperature to study falling temperature through f pipline using PIPESIM Software and providing data from central petroleum laboratory and Rawat operating company. To check that temperature at all points along the flow line and trunk line is above the pour point and wax appearance temperature, check the requirement of heater, heat tracing and insulation for the pipelines more ever is used to studies the influence of changing flow rate, ambient temperature and water cut for pipeline temperature. The line size, line velocity and heat duty of the system have been calculated using excel program.The results show that the minimum temperature criteria for pipelines should be above 54C to avoid gelling of the fluid, Wax precipitation analysis results indicates that the minimum wax precipitation temperature for Wateesh W-was approximately 62°C and the same for Rawat RC-1 well were approximately 58°C.the flowlines size were determined 4” and 6” for trunk line.Also The results show that there is a direct relation between the wax deposition and temperature, It was observed that wax deposit increases with decreasing the temperature. On the other hand, an increase in flow rate results in a decrease in the wax deposition. Finally, hot insulation of the flow lines and trunk line was required, Electrical Heat Tracing to heat the fluid to 75 Deg, chemical injection such as wax inhibitors and pigging process to control the wax deposition.

Analysis of the Influence of Convection Heat Transfer in Circular Tubes on Ships in a Polar Environment

Electric heat tracing is the main measure for cold protection of the polar transfer coefficient in marine engineering equipment, but thermal equilibrium is the key problem this technology faces. In this paper, the circular tube was the research object. We studied the influence of convective heat transfer by Fluent software and experiments with a wind speed of 0–40 m/s and temperature of −40–0 °C by constant heat flux heating. The results show that the convective heat transfer increases with increased wind speed and decreased temperature. When the temperature is below −30 °C, the effect of temperature is increased; when the wind speed is greater than 25 m/s and the temperature is lower than −20 °C, the effect of temperature on the convective heat transfer coefficient of the circular tube increases. Based on the simulation data, we established a prediction model, and the rationality of the prediction model was verified by tests. The model provides reference for the design of electric heat tracing of circular tubes on polar ships.

Enhance flows of waxy crude oil in offshore petroleum pipeline: A review

In the petroleum industry, the transport of offshore crude oil via pipelines may suffer damage known as wax precipitation. This reduces the flow capacity of the crude oil, reducing its transport efficiency. Under extreme conditions, this may also result in serious damage to equipment. To help alleviate this problem, the petroleum transport and flow characteristics of offshore waxy crude oil in pipelines are investigated, together with the development of several options to help minimize wax precipitation. This paper reviews the current research status for reducing wax precipitation and enhancing crude oil flow in offshore pipelines. Specifically, reducing the viscosity of waxy crude oil, strengthening the process technology of the pipeline and the related flow mechanisms are each investigated. This paper also identifies and discusses areas of study that require further investigation. • Offshore crude oil wax deposition is generated by the precipitation of wax crystals in crude oil. • DRAs, PPD, microbial and hydrate inhibitor decrease the viscosity by reducing the generation of wax crystals. • Skin effect electrical heat tracing increase the temperature of pipeline internal to reduce wax deposition. • Inner wall coating reduces the flow resistance of pipe internal to enhance flows of crude oil. • Hernandez Model, Singh Model and Rygg Model describe the multiphase flow characteristics of crude oil in offshore oil pipelines.

Joint Optimization Design of Insulation and Electric Heat Tracing System of Molten Salt Pipelines in Csp Plants

Joint Optimization Design of Insulation and Electric Heat Tracing System of Molten Salt Pipelines in Csp Plants

Heat Recovery from a PtSNG Plant Coupled with Wind Energy

Power to substitute natural gas (PtSNG) is a promising technology to store intermittent renewable electricity as synthetic fuel. Power surplus on the electric grid is converted to hydrogen via water electrolysis and then to SNG via CO2 methanation. The SNG produced can be directly injected into the natural gas infrastructure for long-term and large-scale energy storage. Because of the fluctuating behaviour of the input energy source, the overall annual plant efficiency and SNG production are affected by the plant operation time and the standby strategy chosen. The re-use of internal (waste) heat for satisfying the energy requirements during critical moments can be crucial to achieving high annual efficiencies. In this study, the heat recovery from a PtSNG plant coupled with wind energy, based on proton exchange membrane electrolysis, adiabatic fixed bed methanation and membrane technology for SNG upgrading, is investigated. The proposed thermal recovery strategy involves the waste heat available from the methanation unit during the operation hours being accumulated by means of a two-tanks diathermic oil circuit. The stored heat is used to compensate for the heat losses of methanation reactors, during the hot-standby state. Two options to maintain the reactors at operating temperature have been assessed. The first requires that the diathermic oil transfers heat to a hydrogen stream, which is used to flush the reactors in order to guarantee the hot-standby conditions. The second option entails that the stored heat being recovered for electricity production through an Organic Rankine Cycle. The electricity produced is used to compensate the reactors heat losses by using electrical trace heating during the hot-standby hours, as well as to supply energy to ancillary equipment. The aim of the paper is to evaluate the technical feasibility of the proposed heat recovery strategies and how they impact on the annual plant performances. The results showed that the annual efficiencies on an LHV basis were found to be 44.0% and 44.3% for the thermal storage and electrical storage configurations, respectively.

Analysis and Research on Cold Proof Design of Polar Marine Machinery

Polar marine machinery is an important equipment for China to participate in Arctic energy exploitation. The Arctic region is rich in natural resources and has a very important strategic position. As an important equipment for passage and exploitation of energy, its key technology is particularly important. As a special ship sailing in polar regions, polar ships generally adopt electric heat tracing measures due to the adverse environment in polar regions. The deck machinery and facilities shall be protected against cold. This paper mainly studies the convection of flat plate members under constant heat flow electric heating. The research results can be popularized and applied to the cold protection of most upper facilities of polar ships.

Loss and temperature rise of the skin effect electric heat tracing system

Loss and temperature rise of the skin effect electric heat tracing system

Coupling analysis of a new skin effect electric heat tracing system for deep water heavy oil pipeline

In order to ensure the safety of fluid flow in deep-water submarine pipelines, a safe and energy-saving built-in skin effect electric heat tracing technology was adopted as the thermal management strategy. By analyzing the multi-physics conditions of

Carbonate molten salt solar thermal pilot facility: Plant design, commissioning and operation up to 700 °C

Concentrated solar power (CSP) is not currently cost competitive with conventional power generation or other solar energy technologies, but it is attractive because it integrates commercially viable large-scale thermal energy storage (TES). To improve performance and reduce costs, supercritical carbon dioxide (s-CO2) power cycles have been proposed to increase the thermal-to-electric conversion to values above 50%. However, to achieve this target, the solar energy collected by the receiver and stored in the TES must be delivered to the power turbine at a temperature at or above 700 °C, while current advanced plants only provide thermal energy at 565 °C. For the first time, a high temperature (700 °C) molten salt experimental pilot plant for CSP was designed, built, and tested by Abengoa using carbonate salts as the heat transfer fluid. We demonstrate the feasibility of large-scale, industrially relevant operation between 400 and 700 °C, thus providing a solution to integrate higher efficiency s-CO2 power cycles. We address the key points in material compatibility, component design, instrumentation and system integration. Operational aspects such as preheating and filling procedures, start-up, maximum temperature reached, and the main challenges faced are described in detail. The heat losses in the loop and components are analyzed. We show that with appropriate electrical heat tracing elements, operation with carbonates is feasible and that the main subsystems that must be redesigned are the high temperature tanks and pumps. Lessons learned from the plant operation are summarized here to guide the design of future commercial scale high temperature molten salt plants.

Galvanic corrosion behaviour and mechanism of skin effect heat tracing pipes

ABSTRACTSkin effect electric heat tracing plays an extremely important role in heavy oil transportation because of its high heating efficiency and strong applicability. However, the heat tracing tube often has corrosion failure problems, which threaten the safe operation of the pipeline. We use the weight loss method, potentiodynamic polarisation, combined with SEM and EDS to study the corrosion mechanism of the heat tracing pipe and main pipe under the skin effect. The research results show that the main type of corrosion of the heat tracing pipes in the Liaohe Teshi pipeline is galvanic corrosion. When the two are connected, the main line X52 is protected as a cathode, and the heat treating tube 20# steel is accelerated as an anode.

A Deep-Sea Pipeline Skin Effect Electric Heat Tracing System

In order to ensure deep-water flowline safety, this paper combined the axial temperature distribution model of the submarine pipeline and the distributed parameter circuit model of the skin effect electric heat tracing system; such work is conducive to proving that the heating effect of the skin effect electric heat tracing system depends on the distributed circuit parameters and power frequency of the system. Due to the complexity of the power supply device, the frequency cannot be increased indefinitely. Therefore, for the case that the input of the skin electric heat tracing system is constrained, a generalized predictive control algorithm introducing the input softening factor is proposed, and the constrained generalized predictive control strategy is applied to the electric heating temperature control system of the submarine oil pipeline. Simulation results demonstrated that the control quantity of the skin effect electric heat tracing system is effectively controlled within a constraint range, and also the values of heating power and power frequency are obtained by theoretical calculations rather than empirical estimations. Moreover, compared with the conventional control algorithm, the proposed constrained generalized predictive algorithm unfolds more significant dynamic response and better adaptive adjustment ability, which verifies the feasibility of the proposed control strategy.

Hybrid Solution to the Grand Challenge of Developing Deepwater Stranded Gas

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 27686, “A Revolutionary ‘Hybrid Solution’ to the Grand Challenge of Developing Deepwater Stranded Gas,” by Richard Moore, SubCool Technologies, prepared for the 2017 Offshore Technology Conference, Houston, 1–4 May. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. While the floating liquefied-natural-gas (FLNG) option initially looked promising, high capital expenditure and very high operational expense (OPEX) have limited its potential application, with four potential FLNG projects being canceled in Australasia in the last 2 years. A new solution involving a proprietary hybrid concept has emerged to meet this challenge of developing deepwater gas fields. It is neither surface nor subsea, but the combination of both, offering fundamentally more-efficient and hence lower-cost processing. Background Subsea and Deep Water. When the oil and gas industry moved into deeper waters in the 1990s, subsea processing operations were not available. Techniques were developed to prevent hydrates and corrosion, including addition of chemicals such as glycol and monothylene glycol, insulation, and specialized techniques. More recently, this has included heating in the form of direct electric heating or trace heating in specially constructed pipe-in-pipe-type pipelines. These techniques have proved very successful in shallow waters and for moderate tieback distances. However, with the industry moving to deeper waters and greater distance, these same techniques are proving to be too expensive. The lack of first-stage bulk produced-water separation greatly adds to the costs, resulting in large volumes of glycol and water, as well as salt in the glycol, which requires expensive regeneration methods. Long distances are also a key issue for subsea compression. Power transmission and variable-speed control are viable for short distances but are challenged over long distances (greater than 100 km). Costs of Surface Processing Facilities. Implementation of both conventional gas surface processing and FLNG facilities has often resulted in large mega-facilities that are cost-ineffective. Additionally, they have high OPEX and operational and safety challenges be-cause of the number of people required offshore. The cost impact is greater for surface facilities in deeper water beyond fixed-platform depth. In these cases, deepwater risers and flow-assurance facilities add to a more weight-sensitive floating substructure. Key Differences Between Liquid and Gas Processing. To date, the significant cost of the surface facility has been seen as the driver for long-distance subsea tiebacks. However, there is a key distinction between processing liquids and processing gas. Nevertheless, this distinction has not been considered, debated, or published, to the author’s knowledge. Liquids can be processed on the sur-face relatively efficiently. It is the high-pressure surface gas systems that have a disproportionate impact on size, weight, and cost of surface facilities. Importantly, in regions such as Brazil and West Africa, using a floating production, storage, and offloading (FPSO) vessel to produce liquids is not questioned. Processing liquids offshore on an FPSO is clearly seen as more cost-efficient than bringing the liquids to shore.

Leveraging Control and Monitoring Technologies: Reliability and Lower Costs for Electrical Trace-Heating Systems in Petrochemical Facilities

Electric trace heating is commonly used by the petrochemical industry for the freeze protection of water lines or the temperature maintenance of process fluids. An unreliable trace-heating system can impact the business significantly by damaging the process fluids/piping and potentially causing lost production. Controlling and monitoring the performance of trace heating is important to ensure that the processes are running as desired. This article focuses on the advances made by the trace-heating industry in control and monitoring technologies to improve the reliability of trace-heating systems as well as reduce their total installed costs. A real-world case study example is used to illustrate the reduction in total installed costs using control and monitoring capabilities.

Study of Fuel Oil Handling System in Thermal Power Plants

Study of fuel oil handling system (FOHS) in thermal power plants is intended towards achieving the goal of designing fuel oil handling system in thermal power plants. Designing and process parameters have been proposed in this study analysis. The overall system consists of three stages i.e. Fuel oil unloading, storage and forwarding. Three stages required heat tracing to make the heavy density fuel oil properties suitable to flow through pipes for process requirement in thermal power plants with the help of pumping media. Theoretically, it was found that the proposed Design of fuel oil handling system using electrical heat tracing shows better result as compared to steam heat tracing. The study was done to make existing system of FOHS more refined which is maintenance free and more reliable.

The melting process of a freezing molten salt pipe of concentracted solar power plant

Concentrated solar power plants are potential to provide based load power of the future electrical power system. Commercial concentrated solar power plants using molten salt as the heat transfer fluid and the energy storage medium have been built and show great promising. However, due to high freezing point, the molten salt has a freezing possibility and may block the pipe. In practical, an electrical heat tracing is installed along the flow path of the molten salt to protect against freezing. Once the molten salt is freezing inside the pipe, the electrical heat tracing can be used to melt the molten salt. This paper studied the melting process of a molten salt (60% NaNO3 and 40% KNO3, referred to as Solar Salt) inside a horizontal pipe by an electrical heat tracing. The molten salt is a binary mixture, its freezing point (511 K) is higher than melting point (494 K). A solid-liquid mixture mushy zone exists between the melting point and the freezing point during the melting process. The enthalpy method was used to simulate the solid-liquid phase change phenomenon of the molten salt. The effect of the natural convection inside the pipe was also considerate. The effect of the installation position and the heating power of the electrical heat tracing on the melting process and the melting time were studied. During the heating process, the molten salt close to the electrical heat tracing melts first and forms a mushy zone. With the assistance of the natural convection, the molten salt in the mushy zone flows upward and gathers in the upper zone of the pipe. Thus, the upper zone of the pipe has a higher liquid fraction than the lower zone, which results in a liquid fraction gradient inside the pipe. The results show than the installation position of the electrical heat tracing effects the gradient of the liquid fraction during the melting process. The increase in the angle between the gravity and the installation position, γ , increases the liquid fraction gradient. It takes a same time to completely melt the molten salt when γ equals to 30° and 60°. When γ is 90°, due to a larger liquid fraction gradient, it needs more 5 min than γ is 60°. Therefore, large γ should be avoided for the practically installation of the electrical heat tracing. The results also show that the melting time is 165 min for a 35 W/m heating power, 85 min for 70 W/m, and 51 min for 140 W/m. Increasing the heating power from 35 W/m to 70 W/m can shorten 48.5% of the melting time, while increasing the heating power from 70 W/m to 140 W/m can only shorten 40% of the melting time. This is because a higher electrical heating power increases the liquid fraction gradient of the mushy zone during the melting process. Thus, the percentages of the shorten melting time decreases with the increases of the heating power. This study gives practical reference to the choose and the installation of the electrical heating tracing of the molten salt pipe.

Freeze-proof method and test verification of a cold region tunnel employing electric heat tracing

In recent decades, numerous tunnels have been built in the cold region of China. However, frost damage occurs frequently inside the tunnels; this damage threatens the stability of the tunnels. In order to prevent frost damage, a method employing electric heat tracing (EHT) was presented in this study. Moreover, the EHT-based freeze-proof system layout and installation procedures were also introduced. The tunnel liner EHT system is composed of four parts: heating cable, insulation layer, protective layer and fire protection layer. This EHT system was adopted in the Dongnanli highway tunnel (located in northeastern China) to verify its applicability. In-situ test results indicated that the temperature behind the liner begins to heat up after one hour of electrifying the system; next, the temperature becomes positive and remains stable after three hours of electrifying the system. The operation of the heating system is quite stable, and the insulation effect is significant. Through the assessments of the heating efficiency that is required to reach the target temperature and a constant temperature heating effect, it is suggested that the combination of thermal insulation and electric heat tracing is feasible and effective in preventing frost damage in tunnels. The research results provide references for the design and construction of frost prevention systems in tunnels in cold regions.