Blowdown System Research Articles

The SPARC cryogenic system

The SPARC project at Commonwealth Fusion Systems (CFS) is a tokamak system designed to demonstrate commercially relevant fusion energy and achieve net fusion power output during the first operating campaign, with eventual fusion pulse energies exceeding 1 GJ. The SPARC tokamak includes eight magnet systems, three that use high-temperature superconducting (HTS) tapes. The SPARC cryogenic system (CRYO) consists of three supercritical helium cryogenic loops at nominal temperatures of 8 K, 15 K, and 80 K. CRYO 8 K and 15 K loops cool the HTS magnets to maintain thermal stability and prevent quench, while magnets cooled to 80 K are normally conductive. CRYO provides cold helium using a hybrid system that includes a Brayton-cycle-based cryoplant supporting all CRYO temperature loops, and a fixed volume 8 K blowdown system to remove heat and maintain temperature stability of the toroidal field (TF) magnets during and immediately following fusion pulses. CRYO 4.5 K equivalent peak cooling power is 17 kW for the cryoplant and 2.9 MW for the blowdown system during a 10-second fusion pulse. Primary cryoplant mechanical equipment includes screw compressors, turbo-expanders, heat exchangers, and circulation pumps, while the blowdown system consists of a series of warm and cold helium storage tanks operating at independent temperatures and pressures, with make-up compressors to reset the blowdown system between pulses. CRYO also includes a distribution valve box and multiple vacuum-jacketed (VJ) process lines ranging in nominal diameter from 20 to 600 mm. This paper investigates the various sub-elements which in combination represent SPARC CRYO, and attempts to address some of the technical challenges identified by the team.

Performance and economic analysis of the cooling tower blowdown water treatment system in a coal-fired power plant

In recent years, the treatment and reuse of wastewater have been widely of interest due to the severe shortage of water resources. As is well known, a huge amount of water is consumed in coal-fired power plants, especially for the circulation cooling system in a cooling tower. Therefore, research on the circulating cooling system and cooling tower blowdown water (CTBD) treatment is crucial. In this study, a computational model was established to study the treatment of CTBD by reverse osmosis (RO) and direct contact membrane distillation (DCMD). Recycled fresh water was used as a water supply for the cooling tower. The effects of the main operating parameters on the performances of the RO and DCMD with/without waste heat utilization were explored. The water-saving effects, energy consumption amounts, and economics of the three systems were analyzed comparatively. The results showed that better water-saving performance of the DCMD with waste heat utilization was achieved with a water-saving rate of 18.4% and that the energy consumption and cost were slightly lower than those of the RO. The lowest water treatment cost of the DCMD with waste heat utilization was 3.38 Ұ/m3. In addition, the effect of electricity price on the costs was studied. When the electricity price was higher than 0.31 Ұ/kWh, the DCMD with waste heat utilization was more economical.

Failure of 24 Inches Blowdown Tower Inlet Nozzle Due to Cyclic Surge Forces

Blowdown tower is one of the equipment in closed blowdown system (CBS) in Delay Coker unit in petroleum refinery. The primary intended function of the CBS is to flush out hydrocarbon vapours from coke drum using high pressure steam into blowdown tower. The system is operating in batches and cycles, due to constant operation at various temperature, pressure, and conditions, components are susceptible to various of failures including thermal fatigue, crack, corrosion, and others. Crack incident was observed on the welding of blowdown tower nozzle that connected to closed blowdown system (CBS) piping after 11 years of operation. This paper aims to study the structural integrity and risk level of the CBS system in relation to liquid level in receiving tower (blowdown tower). Dynamic piping stress analysis and Finite Element Analysis (FEA) was conducted on this line and blowdown tower nozzle to evaluate the overall material behaviour and assessed the risk of failure. The acceptance criteria of the analysis were set to be based on ASME VIII-Division 2 part 5.2.2 (Elastic Stress Analysis Method) and ASME II-part D. Findings from FEA shows that the failure occurred on the blowdown tower nozzle was due to surge pressure impact from high pressure steam flow to obstructed high liquid elevation at the inlet nozzle. The high surge pressure that happened near the nozzle has caused the stress to exceed allowable level thus initiated the crack in cyclic/ batch service. It is recommended that petroleum refinery to continuously maintain the blowdown tower level below nozzle to prevent similar phenomenon to happen in future.

Economic feasibility of retrofitting blowdown heat recovery system using steam dryer to lignite-fired power plant for reduced fuel consumption

Blowdown is responsible for heat losses in boiler systems. The main objective of this paper is to propose a system to recover blowdown heat using steam dryer. The system consists of a flash tank, a steam dryer, and an air preheater. The flash tank is used to produce flash steam that is supplied to the steam dryer. Fuel moisture is removed in the steam dryer, resulting in fuel with lower moisture content and exhaust vapor. Exhaust vapor is supplied to the air preheater to increase air temperature before combustion. Due to lower fuel moisture content and higher air temperature, exhaust flue gas temperature can be decreased by adding air heater area. An analysis was performed to determine the payback period for the investment cost of the proposed heat recovery system. It was demonstrated that retrofitting a power plant with this system led to increased energy efficiency of the power plant. A case study of 250-MW existing power plant operating at the boiler pressure of 12.34 MPa was considered. Simulation results indicate that the power plant retrofitted with this blowdown heat recovery system consumes 0.87% less fuel than the power plant without this system. The payback period or the investment in this system is 7 years.

The recovery of blowdown heat using steam dryer in biomass power plant

The main objective of this paper is to propose the blowdown heat recovery system using a steam dryer. A flash tank is used to reduce blowdown water pressure and generate flash steam. Flash steam is supplied to the steam dryer to decrease fuel moisture content. Exhaust vapor vented from the steam dryer is also used to increase air temperature in an air heater. Furthermore, due to decreased fuel moisture content and increased air temperature, the exhaust flue gas temperature may be decreased by increasing the air heater surface area in the boiler. This method of blowdown heat recovery has never been proposed before. Therefore, it may be considered as knowledge gap that is worth an investigation. The use of blowdown heat for steam drying is compared with the use of blowdown heat for feed water heating. Simulation results show that using blowdown heat for steam drying results in a significantly larger net power output. Furthermore, the integration of this heat recovery system is economically feasible.

Understanding the depressurization system design

AbstractA pressure relief valve (PSV) cannot depressurize a vessel or system; it can only limit its maximum pressure during upset or emergency conditions. A blowdown system is usually specified to accomplish the removal of the pressurized, volatile, hazardous, and flammable compounds such as hydrocarbon or ammonia vapor in vessels or systems. The pressure is removed from the vessel using a blowdown system; however, some hydrocarbon liquid will remain in the vessel. This paper explains different criteria for designing a blowdown system. Examples are presented to show how the blowdown time is affected by several factors. The Joule–Thomson effect and its effect on the vessel's inner wall temperature are illustrated using charts and tables. Several applications of the blowdown system are provided that relate to actual offshore and refining operations. Different mechanisms by which the blowdown system is activated are discussed, and a simplified design procedure to design a blowdown system is also provided.

Mechanical and 1st Chemical Cleaning of NEK Steam Generators

Sludge removal is performed on two steam generators (SG’s) at the Krško Nuclear Power Plant (NEK) during every outage. SG’s are a meeting point of five major plant systems: Reactor Coolant System (RC) on the primary side and four systems on the secondary side – Auxiliary Feedwater System (AF), Blowdown System (BD), Main Feedwater System (FW), and Main Steam System (MS). Sludge removal activities take place on the secondary side of the SG’s on the top of the tube sheet. It always consists of classical Sludge Lancing (SL) which is done by spraying water at different angles (30°, 90°, 150°) between the tube gaps in the steam generator tube bundle with a pressure of around 220 bars. Another method is Inner Bundle Lancing (IBL) which means spraying water directly inside the tube bundle with a traveling lance tape with a spraying nozzle at the end. Water is sprayed at an angle or directly on the top of the tube sheet with a robot-guided manipulator which is placed inside a steam generator. The manipulator and therefore the spraying action is controlled by an operator and at times it is fully autonomous to provide the highest protection measures possible. Another method of sludge removal which was for the first time utilized in 2019 at the Krško site was Chemical Cleaning (CC) of both SG’s. During this process, a chemical was injected into the SG’s through the BD system and periodically pumped between the two SG’s to create a dynamic flow and maximize the cleaning effect. To achieve the best results, a constant temperature of the chemicals had to be maintained at all times. Upon completion of chemical cleaning, a rinsing phase was followed to remove any post-treatment chemicals. After all sludge removal activities, a televisual inspection (TVI) of the top of the tube sheet was performed to access the hard sludge area and to search for potential foreign objects in the SG’s. If for instance an object of importance during TV inspection is found, an attempt to retrieve it would usually take place. Other methods of sludge removal such as upper bundle flushing or ultrasonic cleaning have not been implemented in NEK thus far.
 Since the power plant uprate in May 2000, NEK conducted SL on both SG’s every outage also starting with IBL in 2013 and 2015, and the same method was used in the 2018 outage. During the outage in 2019, all three methods (SL, IBL, and CC) have been utilized with the main purpose to extend the full load operation of the plant, preventing and/or stopping denting processes in the SG’s from occurring, reducing and stopping the build-up of hard sludge area to increase/sustain efficiency and remove foreign objects found in the SG’s. SG’s U-tubes are a barrier between the primary side coolant and the secondary side of NEK and the environment. Therefore, it is crucial to keep the highest level of integrity of the U-tubes because any leak could potentially mean a release of radioactive material into the atmosphere. This paper describes the purpose and workflow of sludge removal activities in the outage of 2019 in NEK.

MOVEMENT OF TWO-PHASE GAS-LIQUID FLOW IN HORIZONTAL AND INCLINED PIPES

"Two-phase flows are found in almost all areas of technology. For example, tubular evaporators, boiling water reactors, boiler blowdown systems, heaters, boilers, gas lift pumps, oil and geothermal wells, oil and gas pipelines, refrigerators, process pipelines, and condensers. Two-phase flows are classified as mixtures. According to the composition of the mixture are divided: (a) for single-component (or one-component) - vapor-liquid flows; (b) multicomponent - gas-liquid flows. One-component mixtures consist of the same substance in different states of aggregation. This can be not only vapor-liquid, but also a mixture of liquid or vapor with a solid phase, a water-ice mixture, or a vapor flow with ice particles, for example, in sublimation installations. Multicomponent mixtures are a combination of substances of different physical nature. These include not only gas-liquid flows, but also, for example, mixtures of air and sand, water and oil. The paper presents the main attention is paid to the movement of two-phase flows in the pipeline."

Computational and experimental justification for increasing the performance of the regenerative heat exchanger in the steam generator blowdown system of the AES-2006 project (RU V-392M)

The article discusses the design and operation modes of the regenerative heat exchanger (RHE) in the steam generator (SG) blowdown and drainage system (LCQ) at Novovoronezh NPP-II 1 and 2 (Project AES-2006). The results of mathematical modeling of the RHE operating modes are presented in order to identify the causes of its low efficiency. Based on the results of the commissioning of the SG blowdown and drainage system at NvNPP-II 1, as well as the thermohydraulic calculations of the RHE operating modes, the authors put forward assumptions regarding changes in the rerouting of the piping (Volnov et al. 2017, Yaurov et al. 2017). According to their proposals, the RHE piping was upgraded at NvNPP-II 2. The upgrading in the RHE piping was implemented first at NvNPP-II 2 at the stage of installing the systems and, after the expected result was confirmed, it was applied in April 2020 at NvNPP-II 1. In addition, the authors carried out a comparative analysis of the results of testing the thermohydraulic characteristics of RHEs of the blowdown and drainage system for NvNPP-II 1 (before upgrading, after upgrading in scheduled maintenance 2020) and NvNPP-II 2. These improvements made it possible to achieve more efficient operation of the RHE in the SG blowdown and drainage system and the system as a whole.

Optimization on Blowdown Flow Regulation Characteristics of Steam Generator in a Nuclear Power Plant

During the operation of a nuclear power plant, the blowdown flow measurement signal of the steam generator fluctuates frequently, which interferes with the automatic adjustment function of the flow control valve. When the signal fluctuation reaches the alarm value, the flow control valve will be closed automatically, isolating the steam generator blowdown system, and affect the water quality regulation of the secondary circuit. Through the analysis of the system design, operating conditions and equipment structure, it is shown that due to the blocked flow of the flow regulating valve, the flowmeter is affected by the two-phase flow. In view of the problems, this paper proposes improvement measures from the rationality of flowmeter selection, the optimization of system control logic parameters, and the system multistage depressurization.

SIMULATION AND PERFORMANCE ANALYSIS OF A HYBRID ROCKET ENGINE WITH SELF-PRESSURIZING OXIDIZER

There are many challenges to simulate and design a hybrid engine, such as the dimensioning of the feed lines and tanks, propulsive performance calculations, and simulations of the expected behavior in the combustion chamber and the oxidizer tank during the engine operation. In this work, methods are assembled in a concise and complete analysis of the Gluon hybrid rocket engine, developed by PION Labs, with a blowdown pressurization system, using N2O as oxidizer and a paraffin-based fuel. For that, a study will be presented on the peculiar characteristics of the oxidizer and its behavior during the phases of operation of the rocket engine. Then, the main equations that describe the operation of the rocket engine, including the combustion chamber, injection plate, feed lines, and the oxidizer tank are presented, and the performance indicators calculations of the engine are shown and discussed. Finally, simulation results of the combustion chamber and the oxidizer tank during engine firing will be presented, leading to the concluding remarks on the data obtained.

불어내기식 감압시스템 유동해석 및 준 1차원 압축성 유동식을 이용한 설계 가이드 프로그램 개발

In this study, using LNG as a working gas, computational fluid dynamics(CFD) was performed on a blowdown depressuring system; then, a design guide program(DGP) which can be used in the initial design of the system was developed and validated. The physical phenomena occurring in the gas vessel, blowdown valve(BDV), restriction orifice(RO), diverging pipeline, and long pipeline, which are the main components of the system, were analyzed. Especially, it was confirmed that a supersonic flow was generated during the operation time of the system, and oblique shock waves and a terminal shock wave were generated inside the system. Therefore, in the DGP, the quasi-one-dimensional compressible flow formula that can reflect the physics of supersonic flow was used as the governing equation, and the Fanno flow equation was used to simulate the long pipeline flow. The DGP was validate by comparing with CFD results, and it is expected to shorten the initial design time by quickly deriving the pressure, temperature, and Mach number results of each major components.

Deterministic and Robust Optimization of Hybrid Rocket Engines for Small Satellite Launchers

In this paper, design and optimization approaches are applied to a hybrid-powered small-satellite launcher, namely a deterministic and a robust-based method. A unique hybrid rocket engine is considered, employed in different numbers in each stage of the three-stage launcher: six, three, and one, respectively, in the first, second, and third stage. Liquid oxygen and paraffin-based fuel are considered as propellant combination. A blowdown feed system is assumed to ensure system simplicity and reduce the overall launcher cost. An airborne launch is proposed at a given altitude and speed, whereas the velocity angle on the horizon at first stage ignition is set free. The optimization procedure of the engine design parameters employs a direct method and an evolutionary algorithm in the deterministic and robust-based approach, respectively. An indirect method is used to optimize the ascent trajectory, given the engine design, in both the approaches. In the robust-based approach, uncertainties in the fuel regression rate are taken into account. Small-launcher initial mass is given and payload mass is maximized for a given insertion orbit. A mission-specific objective function is used in the robust-based optimization process to grant the actual achievement of mission goals, despite the uncertainties in the design. Two different design strategies are compared. In the first case the acceleration at first-stage ignition is fixed, whereas in the second case the initial thrust is optimized. Results show that a 5-ton hybrid-rocket launcher can be viable for launch of satellites in the 50–100 kg range and that a small payload reduction, with respect to deterministic optimized solutions, is sufficient to ensure mission accomplishment and also grant the required design robustness.

Availability Analysis of a Steam Boiler in Textile Process Industries Using Failure and Repair Data: A Case Study

Abstract The demand of steam in process industries is increasing rapidly, and this demand can be met by increasing the capacity utilization of steam boilers. Many of the process industries depend on industrial steam boilers as a vital component for their operation. The availability of the boiler can be improved by identifying critical mechanical subsystems/components concerning failure frequency, reliability, and maintainability and minimizing their likelihood of occurrences. The selection of appropriate technique for data collection and reliability analysis is essential. The time between failure (TBF) and time to repair (TTR) of all components and subsystems were collected to carry out reliability, availability, and maintainability (RAM) analysis. The best-fit distribution and distribution parameters were calculated using reliasoft software weibull++10 after performing trend testing. The preventive maintenance intervals of all components and subsystems and the availability of the system were evaluated. The analysis reveals that the combustion system, feed-water system, and blow-down system are the critical subsystems from a reliability perspective and are still the biggest reasons for the boiler downtime. The research study also showed that TTR was longer for the combustion system than the other subsystems, and thus, to enhance its availability, it is suggested that maintenance resources should be allocated at the appropriate moment to the combustion system. The study also shows the usage of RAM analysis in deciding the preventive maintenance intervals of components/subsystems of the boiler. It also provides a reference for the preparation of the maintenance plan for the boiler system.

Erosion simulation and improvement scheme of separator blowdown system ——A case study of Changning national shale gas demonstration area

In the shale gas vertical separation metering skid, after the shale gas is separated by the gas-liquid separator, the bottom sand-carrying sewage is driven by high pressure, and the high-speed flowing sand particles will cause serious erosion to the sewage valve. Given this problem, taking a production well in the Changning area as an example, the corresponding mathematical model, and a three-dimensional model of blowdown valve is established. Based on FLUENT flow field analysis software, the erosion of the blowdown valve is simulated and analyzed under different pressure, sand particle size, and shape factor, sand particle density, and sewage sediment concentration, and the serious erosion problem of the blowdown system is obtained. Therefore, a new blowdown system improvement scheme is proposed, and the erosion of the blowdown valve after the scheme operation is simulated. The results show that the maximum erosion rate of the improved blowdown valve is 1.024 × 10−6kg/(s·m2), and the converted annual erosion thickness is 57.4 μm, which is 26.538–61.247 mm compared to the unimproved sewage valve. The corrosion inhibition rate of the sewage system can reach more than 99%. This greatly reduces the erosion rate of the blowdown valve and ensures the safe operation of the equipment.

Energy efficiency in steam using industries in Greece

ABSTRACTThe industry sector in Greece is responsible for one-quarter of the overall total final energy consumption accounting for 3.8 Mtoe in 2015. Since 2007, a 29% decrease is noted due to the financial crisis. The goal of this paper is to provide information on the current industrial energy profile of Greece, with particular reference to the steam industry. It presents the outcomes of 10 energy audits in industries that use steam followed by a list of possible measures: insulation, installation of a deaerator unit, heat recovery, automatic blowdown system and regulation of excessive air. The proposed measures result in energy savings of 5.8 GWh/year and show that the potential of energy savings in the Greek steam industry is quite considerable.

Unsteady release model of natural gas transmission station considering effects of safety interlocking system

ABSTRACTRelease parameters of natural gas transmission station (NGTS), such as release rate, released mass, etc., are important for predicting dispersion range of gas jet and flame impingement radius. Through the intervention effects of safety interlock system (SIS) which includes automatic isolation system and blow-down system, the release parameters change with the time as the isolated process unit depressurizes in release accident. The proposed model in this study takes the effects of SIS into consideration for calculating the parameters of unsteady release. A case application confirmed the effects of this model. The results support quantitative consequence assessment and accident emergency response.

Improving the performance of a heating system through energy management by using exergy parameters

Energy management systems are used to analyze the efficiency of energy systems and identify any problem areas to lower costs and save energy, typically using energy based performance measurements. Our aim was to use exergy parameters, instead, to see if more accurate information could be obtained about which ener?gy saving application would result in greater energy savings. Exergy analysis is based on the Second law of thermodynamics and focuses on the environment and the quality of the energy. Implementing an exergetic approach to analyze a steam heating system, we examined data related to exergy flows and exergy losses, and ultimately improved the performance of the system through this energy management model. The following seven energy saving applications were identified and ranked according to their improvement potentials: adjusting the air to fuel ratio ? 1, preventing steam leaks ? 2, installing an automatic blow down system ? 3, insulating the pipes ? 4, insulating valves and flanges ?5, insulating fuel tank ?6, and recovering heat loss from the waste condensate ?7. The optimum ranking obtained through the exergy analysis was 3-1-2-5-7-6-4. A reduction of 15.918 kW in exergy consumption was achieved by installing an automatic blowdown system. This meant a total reduction of 1779.03 kg per year in total fuel consumption, $1458.81 per year of cost reduction and the total cost reduction achieved was $1829.25 per year. Making improvements to the seven selected areas in the system, 38.4% of the energy loss was recovered while the recovery in the exergy consumption was 44.5%.

Natural Gas Saving And Emissions Decrease In Public Health Care Sector – A Case Study

Abstract A study on natural gas saving and emissions decrease in the public health care sector is presented. The analyzed hospital complex belongs to the largest ones in Slovakia and uses both hot water and water steam for heating purposes. Visual steam system inspection revealed serious inefficiencies, including steam venting, missing pipelines insulation and obsolete steam sources with dysfunctional blow-down system. Defined experiment with stepwise steam appliances shutdown enabled quantification of excess natural gas consumption due to these inefficiencies. Measures proposed for the solution of this state are inexpensive, with a short payback period. The expected natural gas savings amount up to 3200 MWh/year, which represents roughly 50% of the total natural gas consumption in the hospital complex.

Experience of commissioning the AES-2006 (V-392M) steam generator blowdown system

Structural features of the AES-2006 design (V-392M reactor plant) steam generator blowdown and drainage system have been considered. Design peculiarities of components and the system as the whole have been comprehensively analyzed, and the advantages and disadvantages of the circuitry and design solutions used are presented. An apparent advantage of the system's flowchart is the maximum blowdown rate increased to 140 t/h. At the same time, issues have been identified caused by insufficient elaboration of structural elements.Based on the earlier experience of the system commissioning, a modified flowchart has been proposed for the steam generator blowdown and drainage using multi-pass valves with an electric single-turn (EST) actuator drive in the system. The flowchart modification makes it possible to reduce the specific content of metal in the system and to provide an extra space for the maintenance of the system's regenerative heat exchanger in a pressurized shell, to use eight multi-pass valves for the steam generators instead of 36 electromagnetic valves, and to cut the operating and repair costs.Modifications have been proposed to the regenerative heat exchanger design to give it a better performance, including installation of circular partitions in the lower inlet (pressure) and the upper outlet chambers. As the result, this leads to a heat exchanger with three passes in the tube space which helps achieving the required flow rate.The above updates will improve the performance and reliability of the steam generator blowdown and drainage system as far as its design functions are concerned, this to result in the secondary circuit's water chemistry arranged so that to minimize the amount of deposits on the heat-exchange surface of the PGV-1000MKP steam generators.