A desalination plant using solar heat as a heat supply, not affecting the environment with chemicals

Steel production is one of the biggest emitters of greenhouse gas in the industrial sector with about 8% of total global CO2 emissions. Although the majority of emissions can be attributed to primary steel production, there is also potential for reducing CO2 emissions in downstream steel processing. Large industrial furnaces, which are necessary for heating steel, are currently primarily fired with natural gas and by-product gases from primary steel production, offering great potential for heat recovery measures from exhaust gases. However, switching to alternative climate-neutral fuels could change this potential and thus jeopardize the economic viability of heat recovery measures. In the present work, it was therefore examined to what extent a change in energy sources in industrial furnaces affects the potential use of heat recovery in steel processing. For this purpose, an optimization model was used that takes into account heat recovery by means of direct heat transfer, heat pumps and heat distribution systems. Potential future changes in energy supply for industrial furnaces were examined using different storylines. Two different energy price scenarios were also considered to address uncertain developments in energy markets. The results show that heat recovery is a cost-effective and definitely recommendable measure. Switching to alternative fuels has little impact on the use of heat recovery. Electrification and thus the elimination of flue gas, on the other hand, greatly reduces the potential for heat recovery.

High-energy efficiency desalination project using a full titanium desalination unit and a solar pond as the heat supply

Despite the fact that aviation gas turbine engines (GTE) have reached a high degree of sophistication, requirements for the improvement of their efficiency are constantly increasing. Reduction of specific fuel consumption and specific weight of the engine unit makes it possible to improve aircraft performance. One of the effective means of reducing specific fuel consumption and obtaining high thermal efficiency of a gas turbine engine is the use of heat recovery, so the interest in it holds throughout the period of development of gas turbine engines. However, the use of heat recovery in aircraft gas turbine engines is faced with a contradiction: on the one hand, heat recovery allows reducing specific fuel consumption, but, on the other hand, it increases the weight of the power plant due to the presence of a heat exchanger. Moreover, with the increase in the degree of regeneration, specific fuel consumption decreases, whereas the mass of the power plant increases.To obtain the desired effect, it is necessary to optimize simultaneously both the parameters of the engine work process and the degree of regeneration of the heat exchanger according to the criteria of evaluating the engine unit in the aircraft system. For this purpose, it is necessary to have a mathematical model for estimating the weight of a highly efficient aircraft heat exchanger. The article presents a developed mathematical model for calculating the weight of a compact plate heat exchanger used to increase the efficiency of a gas turbine engine due to the heating of compressed air entering the combustion chamber by the hot gas that enters the combustion chamber from behind the turbine. We chose a rational pattern of relative motion of the working media in the heat exchanger, the optimal type of plate-type heat transfer surface in terms of minimizing the weight of the heat exchanger and the hydraulic losses in the air and gas ducts. For the selected surface type, the dependence of the specific weight of the heat exchanger on the degree of regeneration is determined for different nozzle exhaust velocities on the basis of a computational algorithm. To assess the reliability of the obtained model, comparative analysis of the effect of the degree of regeneration on the specific weight of the heat exchanger was carried out, based on the comparison of the results of calculations for the developed model with the data of other authors and with the data for the produced regenerators.

Two rectangular modules with a total interior membrane surface area of 13.53 m2 were consecutively combined to evaluate the use of heat recovery in an air-gap membrane distillation (AGMD) system. Several operating inlet parameters including feed water temperature, mass water flow rate and salinity were investigated. The experimental results revealed that the performance of the system was improved by virtue of efficient heat recovery resulting from combining two AGMD membrane modules in series. Under optimal inlet operating parameters of cooling water temperature of 20 °C, salinity of 0.05% and flow rate of 3 l/min, the system productivity (Pp) increased up to 192.9%, 179.3%, 176.5% and 179.2%, and the thermal efficiency (ηth) by 261.5%, 232.6%, 239.4% and 227.3% at feed water temperatures of 45 °C, 55 °C, 65 °C and 75 °C, respectively. Concurrently, the specific waste heat input (Ew.h.i) decreased by 6.7%, 4.7%, 5.6% and 2.7% due to the efficient heat recovery. The results confirmed that heat recovery is an important factor affecting the AGMD system that could be improved by designing one of the two AGMD modules with polytetrafluoroethylene (PTFE) hollow fibers with a flow length shorter than the other one having a salt rejection rate of 99%.

This paper proposed the effect of using a heat recovery system in the gas turbines of Semnan to shahroud oil pumping station in energy conservation point of view. Heating the transferred fluids is one of the common approaches to reduce fluids viscosity and energy consumption, respectively. Due to the low efficiency of station turbines compared to modern turbines, it is expected that the use of heat recovery has a positive effect on improving station performance. By analyzing the combustion products of the gas turbine at the station, the heat extracted from the exhaust gas flow has been calculated which is consumed in the recovery boiler. The pipeline application process including recovery boiler and main equipment of Semnan and Shahroud pumping stations have been modeled. By applying the model, it found that the amount of energy savings by gas-oil heating using a heat exchanger equals to 395311 m3 natural gas in annually. Therefore, optimal points of using combustion heat in the gas turbine output were obtained. In addition, the reduction of power consumption in the presented station has been calculated. Economic calculations were carried out for different countries including Iran, Scandinavian countries, China and the Europian Union average, based on their energy prices and bank interest rates.

Experience with plate-and-frame ultrafiltration and hyperfiltration systems for desalination of water and purification of waste water

The article considers conditions and possibilities for installing cogeneration units (CUs) in district heating boiler houses. The main requirement to do it is the equality of the CUs’ heat capacity and the heat capacity of the boilers that are going to be replaced.
 Because the fuel (natural gas) consumption increases due to such replacement, it is necessary to determine the conditions, taking into account the constant growth of energy carriers’ prices, under which the transition to cogeneration technologies in the heat supply system will be feasible, i.е. the project will make a profit and ensure the reasonable payback period. For this purpose, the relationships between the profitability of the project, the economic indicators of the equipment included in the cogeneration unit, and the price of energy carriers are suggested. An analysis performed with the help of these relationships showed that the cogeneration unit of the same thermal capacity as the boiler (or boilers), which is going to be replaced, in comparison with CU installed on the basis of a generating unit definitely requires an increase in fuel consumption, and the profit, determined as the difference between income from generated electricity sales and fuel purchase costs, becomes dependent on the prices of natural gas and electricity, as well as the cost-effectiveness of the equipment for cogeneration. With certain combinations of these parameters, the cogeneration unit, installed on the basis of heat generation, may not be profitable, but unprofitable. Moreover, as natural gas price increases and electricity tariff remains fixed, CUs, designed as profitable, may become unprofitable. These conditions are considered in the article. Relationships between the CU’s parameters and tariffs for the natural gas and electricity, which determine the area of profitable work of the cogeneration unit, are obtained. Given the current prices for energy carriers, the design of the CU based on the communal heat supply comes to the selection of the equipment that ensures the profitability of the installation that is sufficient for the recoupment of capital investments within 2-3 years. At the same time, the acceptable limits of the possible increase in the gas/electricity tariffs ratio should be determined.
 The main conclusion: the cogeneration unit based on district heat supply with a positive economic effect can be installed only if certain economic and technological conditions, which must be taken into account when designing it, are observed.

Apart from absorption cooling, absorption heating technologies are also widely used for waste heat recovery and renewable energy utilization. Waste heat recovery in district heating systems covers cogeneration heat recovery and flue gas heat recovery, which can improve the overall energy efficiency by 5–30%. Meanwhile, in industrial processes (drying, evaporation, and distillation), technologies such as closed/open absorption heat pump (AHP/OAHP), closed/open absorption heat transformers (AHT/OAHT) and absorption-compression heat pump (ACHP) are employed with various stages, effects and working fluids, to meet temperature requirements of 50–160 °C. To evaluate the efficiency of absorption heating technologies in the renewable energy field, solar heating performances between a solar air source absorption heating pump (ASAHP) and a conventional solar collector heating, are compared within ASAHP’s applicability domain (based on the temperature and radiation ranges). In addition, different geothermal heat pump systems are introduced for cascade utilization of geothermal energy. The absorption-compression heat pump (ACHP) is selected as a promising candidate, and detailed comparisons of this technology working with various novel NH3/IL working fluids are presented. This chapter also provides many advanced prospective for a more reasonable utilization of waste heat and renewable energy sources.

This dissertation provides a new way of research thinking to the optimization of CHP cogeneration unit's thermal system, using 'unit consumption analysis'. The 'fuel unit consumption analysis' method is applied to build up the optimization model of a thermal system in cogeneration unit, and to propose the optimization scheme of the waste heat recovery system or condenser circulating water for heat supply. Meanwhile, the optimization scheme of reducing the heat supply network terminal temperature difference is put forward as well. After the application of these optimization models and schemes in the 300MW cogeneration unit, the results show that with the reduction of the heat exchanger's terminal temperature difference, the unit fuel consumption of the cogeneration unit drops significantly. The optimization models and the specific optimization scheme proposed in this paper to a certain extent provide and important reference to the energy saving in cogeneration units.

Case study on combined heat and water system for district heating in Beijing through recovery of industrial waste heat in Tangshan

An experimental study was performed for the boiling heat transfer enhancement of water/salt mixtures on both plane and roll‐worked enhanced tubes in compact staggered tube‐bundle evaporators under atmospheric and increased pressure conditions. The effects of tube spacing, position of tubes, test pressure and salt‐water concentration on the boiling heat transfer characteristics in restricted spaces of compact tube bundles consisting of plane and roll‐worked tubes were investigated. The experimental results indicate that the single roll‐worked tubes in a bulk liquid have a greater boiling heat transfer promotion than the single plane tubes. For the plane tubes in compact tube bundles, the effect of tube spacing on the boiling heat transfer is very significant. The boiling heat transfer has a maximum enhancement when the optimum tube spacing is selected. For the roll‐worked tubes in compact bundles, the effect of tube spacing on the boiling heat transfer is also significant as the tube spacing is small. The boiling heat transfer still has a maximum value and a compound enhancement effect of the boiling heat transfer from both the optimum tube spacing and the surface treatment is observed for the enhanced tube bundles.

This paper presents a proposal for a test specification for HVDC thyristor valves. The test specifiation includes a discussion of the criteria for successful type testing, a proposal for selection of test withstand voltage levels and a description of proposed dielectric and operational tests. The dielectric tests are intended to verify the withstand and other voltage-related characteristics of the valve and the operational tests are intended to demonstrate the correct operation and capabilities of the valve under various operating conditions including critical faults. The test series consist of type tests and production sample tests performed at the manufacturer's test facilities prior to shipment. Manufacturer's equipment development tests, routine factory tests, commissioning tests and other site tests are not within the scope of the test specification, and hence are not included.

Experimental validation of the theoretical ejector model in a low-grade waste heat refrigeration system using R1233zdE as a working fluid

During the COVID-19 pandemic, many recommendations were made in the field of limiting the transmission of the SARS-CoV-2 virus, from which we can learn a lesson for determining ventilation strategies in strategic types of buildings (those whose closure during a pandemic is harmful to the economy, e.g., nurseries). The research was aimed at identifying recommendations in the field of ventilation and proposing a solution that would be applicable in existing buildings intended for the care of small children, and which would ensure the proper quality of the building environment, at the same time with low costs incurred by the owners. The outside air pollution (PM10) and the climate in winter (low air temperature) were also taken into account. A strategy was proposed based on the use of decentralized units, dedicated to single rooms, thanks to which the appropriate amount of air is supplied (per person), the air is cleaned and heated in the heat recovery exchanger. It has been shown that the use of heat recovery ensures that the costs of air heating will be significantly lower than during airing. The proposed solutions require two holes in the external wall with a diameter of 160–200 mm (depending on the number of people), which guarantees the technically possible application in existing buildings. The strategy provides suitable conditions for the functioning of nurseries, but can be used in many types of buildings, in cold and temperate climates, where airing of the rooms during winter is not possible, especially in the case of locations where the quality of outdoor air is very poor. The proposed strategy may be applied during a pandemic, but also on a daily basis, because by ensuring the proper quality of indoor air, young children will have healthy and hygienic conditions for development when they are not at home.

Different solutions of renovating the ventilation in apartment buildings have been researched. The analysis shows that the use of heat recovery in cold climate regions is essential. Central as well as apartment- and room-based solutions with heat recovery have been studied. Balanced ventilation is suitable for small (2 - 3-storey) apartment buildings with a suitable room solution for apartments. In larger apartment buildings, the system with the exhaust air heat pump could be used. This is particularly suitable for apartment buildings with mechanical exhaust ventilation. In small apartments, it is most suitable to use room-based air handling units (AHUs) with the recuperative heat exchanger, plus exhaust ventilators in the WC, bathroom and kitchen. The economic indicators of this system are best for two-room apartments. Apartment-based AHUs are suitable for large apartments if there is no opposition from the residents, which is caused by ventilation tubes (ducts) in the apartment. The comparison of the reduced energy cost in case of different AHUs has been presented for small apartment buildings.