Process Heat Applications Research Articles

Solar “tower reflector” systems: A new approach for high-temperature solar plants

During the last few years, considerable research efforts have been directed at the Weizmann Institute towards development of high-concentration, high-temperature solar energy systems. This included optical methods and devices, thermal receivers for solar thermal electricity generation, and thermo-chemical processes for solar energy storage and solar fuel production. Some of these efforts are now mature enough for transfer to industry, and programs are starting to affect the transfer and upscale the new technologies to commercial levels. Feasibility studies carried out during 1995 in cooperation with industry have shown the advantage of the new high-concentration system approach. The costs of high-quality solar energy are attractive, even before application of government subsidies: $800/kW th for high-temperature process heat applications, and $2500/kW e for solar/hybrid power plants.

Feasibility study on the applicability of a diffusion-welded compact intermediate heat exchanger to next-generation high temperature gas-cooled reactor

The development of an intermediate heat exchanger (IHX) transferring high temperature heat to a process heat application is of prime importance for a next-generation high temperature gas-cooled reactor (HTGR). The IHX needs high structural integrity and reliability over 900°C for a long duration. A plate fin type compact heat exchanger (PFCHX) has a large heat transfer area per heat exchanger volume and is expected to be used as the IHX. However, the brazing for connecting fins and plate is not reliable when existing PFCHXs are used in a high temperature condition for a long time. We have proposed a concavo-convex plate type compact heat exchanger (CPCHX) which consists of concavo-convex plates (CPs) welded by solid state diffusion and made of nickel-based superalloy Hastelloy XR. In our study, first, an optimized condition for the solid state diffusion welding between the CPs of the CPCHX was found by experiments using test pieces made of Hastelloy XR. Second, small-scale diffusion-welded CPCHXs were designed, manufactured and installed in a test loop to investigate the reliability of the diffusion welding. As a result of leakage tests, it was confirmed that the reliability of the solid state diffusion welding between the CPs of the small-scale CPCHX is sufficient. A thermal performance test revealed that the thermal conductance of the small-scale CPCHX was better than calculated. In addition, a design study for the CPCHX was performed to investigate the feasibility of the diffusion-welded CPCHX to the IHX in a next-generation HTGR.

Temperature equalization phenomenon in a high temperature reactor core with central column

Abstract The usual design of a High Temperature Reactor in Germany refers to a pebble bed core of cylindrical shape, like AVR, THTR and HTR-Modul. Since also other geometries are possible, concept considerations for a HTR with non-cylindrical core have already been made, indicating some advantage in safety due to a limitation of the maximum core temperature in case of a depressurization accident of the primary loop. Using the concept of the AHTR-500 for process heat applications the effectiveness and influence of the central column was evaluated. Results for heat flows and stored heat in core and central column have been calculated for the case of depressurization by using the computer codes THERMIX/DIREKT/TPlot.

New perspectives and pre-feasibility results of the process heat HTR work

Some pre-feasibility results from the design evaluations of the advanced high temperature reactor AHTR for process heat applications are given, e.g. coating of the spherical fuel elements with silicon carbide as a fission product barrier, design of the central graphite column and the graphite top reflector without any metallic structure, after heat removal system based on natural convection for the primary and secondary circuit, venturi jets to reduce the depressurization rate of the helium in case of damage to the primary ducts etc.. On the basis of these results it is possible in the future, that AHTR can be designed in such a way, that any type of damage of the plant or due to any operator error, poses no hazard to the public. With these design perspectives and attendant simplification of the plant design, it is possible to reduce the investment costs by 10 to 15%, so that the economic competitiveness of AHTR will improve in the future. It has been further shown, that coal gasification with a high temperature reactor reduces CO 2-emissions by a factor of about two by the methanol production and also by the electricity generation in comparison to the conventional methods.

Solar, industrial process-heat applications in selected Turkish industries

We discuss the potential and economic feasibility of solar, industrial processheat applications in the Turkish food, textile and chemical industries. The study covers 18 sites and end-use temperatures up to 120 and 150 °C. A solar system composed of parabolic troughs but without thermal storage and to be backed up by the existing conventional boiler is chosen. The system-size range investigated is 500–20,000 m 2. The economic criteria applied are net present value analysis and the determination of internal rate of return. Break-even net fuel prices and break-even system sizes, which make the net present value equal to zero, are also calculated. Levelized energy-costs analysis and the method of the discounted pay-back period have been included in the study.

Thermal-hydraulics of helical-type helium/helium intermediate heat exchangers (IHX) for nuclear process heat applications of high-temperature gas-cooled reactors (HTR) — fundamental research and large-scale tests

The influence of the yaw angle on heat transfer and pressure drop was studied by testing tube banks of straight tubes at different angles between the flow direction and the tube axis in the range 15° ⩽ ϕ ⩽ 90° (cross advantages caused by an opposite inclination of neighbouring tube layers are shown. Results from the fundamental work on straight tube banks were checked at a semiexperimental helical-type heat exchanger for a nuclear process heat application, which is characterized by a large thread pitch and opposite-sense coiling of the tubes.

Present status of research and development for HTR in China

The HTR R&D project is being carried out in the relevant institutions in China. The topics covered include fuel element technology, graphite development, fuel element handling system, helium technology, fuel reprocessing technology, as well as HTR design study. Some results of the HTR research studies are described. In addition, a test facility for the investigation of HTR Module reactor safety and the process heat applications of HTR is under construction in a joint project to build a 10 MW test HTR with Siemens-Interatom, KFA Juelich and INET. The conceptual design of a 10 MW test HTR has been completed by the joint group. In parallel the application study of HTR Module is being carried out for the oil industry and the petrochemical industry, as well as for power generation. Some preliminary results of the application study include heavy oil recovery in the Shengli oil field and process heat application at the Yan Shan Petroleum Company.

炭酸ガス排出抑制におけるエネルギーおよび技術選択 核エネルギーと化石燃料の共生利用に向けて

The potential of CO2 emission reduction is analyzed by the MARKAL model for the Japanese energy system in the time horizon 1985-2030, taking into account such reduction measures as energy conservation, fuel switching, and technology substitution. Among them, nuclear energy utilization is found to have a large CO2 reduction potential, i.e. from 10% reduction of the total emission in 1990 to the levels of 16%, 21% and 42% in years 2000, 2010 and 2030, respectively, through electric power generation and process heat application.

Development prospects of high-temperature gas-cooled reactors and their role in nuclear power

The advantages of a high-temperature inherently safe nuclear reactor are discussed. The characteristics of the two HTGRs being developed in the USSR, the 200 MW(t) VTR-M reactor and the 1060 MW(t) VG-400 reactor, are described. These prototype reactors will be built and utilized both for electrical power generation and for process heat application.

Prospects for HTGRs in developing countries

The electricity supply options in developing countries are assessed in terms of their need for small and medium power reactors. The world status of nuclear power is summarized and the growing share of nuclear power in developing countries is discussed. The prospects for small HTGRs in these countries are considered for electricity generation and for process heat applications.

Plant design and safety concept of the HTR-module

The new KWU/Interatom concept of a modular High Temperature Reactor is characterized by the fact that several standardized nuclear heat production units, each having a power output up to 200 MW(th), are connected into parallel to obtain a power plant of any desired output for the production of process steam and electricity for the application in district heating and for the direct application of process heat. The safety concept of the modular reactor is such that the reactor plant shall stay in a predictable state and shall not release an excessive amount of fission products into the environment even for hypothetical accidents.

Design evaluation of a small high-temperature reactor for process heat applications

The high-temperature reactor is also suitable for process heat application, in particular in smaller size units. On the basis of the results of R & D and demonstration work on coal refinement some improvements for small high-temperature reactor for process heat applications are discussed. These are: increase of the gas outlet temperature, the gas inlet temperature, the decrease of the overall system pressure, and non-integration of the primary circuit components. Some of these design evaluations are based on the results of the pre-project for the extension of the AVR-reactor in Jülich to be used as a process heat plant.

A high power Class E amplifier for high frequency electric process heating

ABSTRACT The design and construction details are given for a 100 W output Class E amplifier operating at 3-3 MHz suitable for high frequency electric process heating applications. The unit used IRF 450 type MOSFETs in parallel to achieve the power output

The Dual Medium Storage Tank at the IEA/SSPS Project in Almeria (Spain); Part I: Experimental Validation of the Thermodynamic Design Model

Efficient and reliable thermal storage is an important requirement for substituting conventional power systems with solar thermal facilities. Storage will synchronize the intermittent supply of solar radiation with the usually constant demand of technical thermal processes. The distributed collector system of the IEA/SSPS Project in Almeri´a (Spain) uses two different storage systems for the 100 to 295°C temperature range: a single thermocline vessel and a dual medium storage tank (DMST). In the first tank, thermal oil is used as the energy carrier as well as for energy storage; in the dual medium tank, the storage medium is cast iron, and the oil acts primarily as a heat transfer fluid. At the SSPS, this concept’s potential for future process heat applications has been assessed. Performance and operational restrictions of the DMST were systematically studied over a wide range of temperatures, and an existing simulation model was verified and adapted at the same time. The thermodynamic model of the DMST is presented and compared with the first results of the 1985 test program.

High efficiency power source for HF electric process heating applications

ABSTRACT The paper is concerned with the application of a class E converter to electric process heating. A simple efficient converter is described which is suitable for high frequency electric process heating loads.

Class E switching-mode power amplifier for high-frequency electric process heating applications

The letter is concerned with the application of a class E convertor to electric process heating. A simple efficient convertor is described which is suitable for high-frequency electric process heating loads.

Invited paper. Review of solid state power devices and circuits for HF electric process heating applications Part II: circuits†

In Part II of this paper the different switch mode power supply topologies are reviewed as well as high frequency linear amplifiers. Frequency and power limitations are discussed with particular reference to the suitability for dielectric heating power sources.

Operation of a 25 kWh Barium Hydroxide Latent Heat Storage Unit in the Power Range 2–6 kW

Among the latent heat storage media considered for short-term storage of solar and nonsolar heat in house heating and process heat applications, barium hydroxide is particularly promising because of its large storage density and its storage temperature of 78 °C. Results of tests with a 25 kWh barium hydroxide “dynamic” latent heat storage unit are reported. The investigations included the discharge behavior, the range of possible discharge powers, variations of the power during discharges, and the “useful” temperature for a future applier. The results are encouraging. The medium remained unchanged during 40 charge/discharge cycles performed within ten months. Storage densities up to 125 kWh/m3 were achieved with a potential for still higher ones.

Invited paper. Review of solid state power devices and circuits for HF electric process heating applications Part I devices†

This paper summarizes a subsequent review of solid state, high speed switching and high frequency linear devices. MOSFET and bipolar device switching combinations such as the cascade and BIPMOS arrangements are mentioned with emphasis placed on their performance limitations and particular reference to their suitability for dielectric heating power sources.

Energy Conservation Potential of Large Capacity Solar-Assisted Heat Pumps for Low Temperature IPH Applications

Energy conservation and economic potential of large capacity (∼MWth) solar-assisted water-to-water heat pumps (SAHP) is evaluated for year round low temperature (<100° C) industrial process heating applications at four locations in the United States. The long-term thermal performance of the SAHP system is determined by a recently proposed utilizability method that accounts for the variable coefficient of performance of the SAHP system. The large SAHP system appears to be an attractive energy conservation alternative to fuel oil and electricity for locations with high solar resources and low electricity costs. In all but one location, the SAHP system was clearly superior to the solar only systems, such as flat plate and concentrating collectors, from the point of view of the annualized delivered energy cost. For the ranges of collector area and load temperatures considered in this study, the large SAHP system has clearly superior energy conservation potential at all four locations compared to other alternatives such as fuel oil or electricity. However, the practial suitability of SAHP cycle, as determined by the levelized cost of delivered energy, is unfavorable at all four locations when compared with fuel oil.