Recoverable Heat Research Articles

Heat recovery from wastewaters for household space heating

The potential for using heat recovered from household wastewater for space heating is explored. A breakdown of the average household's daily production of 240 gallons of wastewater is analyzed to determine a recoverable heat potential of 50,000 Btu per day. Two types of dwelling, well-insulated single family and multi-family, are estimated to have a potential of 30 percent and 80 percent, respectively, of their space heating requirements available with a heat pump recovery system. Research would be needed to solve the problems of congealed soap and fatty materials in the equipment. Legislation would also be needed to change public health requirements in many areas. Cost estimates indicate that this type of system is only economically feasible for the multi-family residence. (DCK)

Heat Recovery From Multi-Turbine Installations

In an era when energy conservation and fuel shortages are not uncommon, mechanical systems designed to improve the thermal efficiency of fuel-consuming equipment have become a necessity. This paper presents an approach to the process and mechanical design of a energy in a gas-plant process. Introduction Rapidly rising energy costs have resulted in intensified searches for improving gas-plant energy balances and have provided the economic incentive to develop better energy recovery systems. Exxon Co., U.S.A., recently completed two multi-turbine energy recovery systems to supply heat in natural gas processing plants. These installations have been operating successfully for several months. Recognizing that special considerations will be required for each particular application, the design concepts and objectives outline below represent the major considerations for these two installations and are intended to serve as a guide for future applications. 1. Evaluate the gas-plant process fuel requirements and determine if energy recovery from gas-fired turbines could be justified to reduce process fuel volumes. 2. Evaluate and select the optimum heat-transfer fluid to transfer the recovered energy to the process area or utilization. 3. Design and fabricate an energy recovery heater and duct-work system that will allow the turbine exhaust gases to heat the transfer fluid efficiently. 4. Evaluate and de sign special structural requirements of the system to avoid any interference with the turbine operation. 5. Design and install an automatic control system with appropriate alarms and shutdowns to ensure the protection of the equipment. Equipment Description Using a modular design concept, a turbine-exhaust heat recovery system can be divided into five functional elements:Gas-fired turbines supply the recoverable heat energy (see Figs. 1 and 2).Turbine ducts transport the exhaust gases from the individual turbine to a common collection duct (Figs. 1 and 2).The common collection duct accumulates the exhaust gases from the turbines and conveys them into the heater (Figs. 1 and 2).The waste-heat exchanger transfer energy from the turbine exhaust gases to an appropriate heat-transfer fluid (Figs. 1 and 2).The heat-transfer-fluid circulation system transports the recovered energy from the heater to the process equipment for utilization. This circulation system includes such equipment as pumps and surge vessel. Photographs of an actual equipment installation are presented in Figs. 3 and 4. presented in Figs. 3 and 4. Heat-Recovery Application Process heat requirements first must be evaluated to Process heat requirements first must be evaluated to determine whether a heat recovery operation is feasible. This work should begin by reviewing the thermal efficiencies of all fuel-consuming equipment in the plant. Equipment such as old boilers and gas-fired turbines are usually thermally inefficient (20 to 50 percent) and lend themselves to energy-recovery operations. this is particularly true if the old boilers are the heat source particularly true if the old boilers are the heat source for the processing plant. Gas-fired turbines reject 70 to 80 percent of their fuel's energy to the atmosphere. JPT p. 639

An estimate of the natural heat resources in a thermal area in Iceland

Various geological and geophysical principles involved in the exploitation of geothermal areas are summarized with special reference to the Hengill high-temperature thermal area located 30 to 40 km east of the city of Reykjavik, Iceland. A reservoir model, which applies to this area, is discussed quantitatively, and it is shown that the heat stored in the reservoir rock beneath the thermal area is the main source of geothermal energy. The rate at which this stored heat can be tapped depends on the availability of water. An estimate of the order of magnitude of the total recoverable heat resources in the Hengill area, based on the reservoir model presented, indicates that a total of the order of 10 10 tons (1) (1) Metric tons are being used in this paper. of water at 220 to 230 °C could be produced in this area during a period of 100 years. This water is flashed in the boreholes and will yield a total of 2.5 × 10 9 tons of dry saturated steam with a pressure ranging from 10 ata to 2 ata. The estimated production rate of steam is of the order of 3000 tons/hour, or comparable to the production which has already been obtained in the geothermal area at Larderello in Tuscany, Italy. The production costs, based on the rate of 300 tons/hour of steam, have been estimated at $ 0.16/ton steam, and the investment necessary is estimated at $ 5000/ton steam/hour. Corresponding figures for larger installations would probably be somewhat lower.

Total, available, returnable and recoverable heat in combustion gasesP. O. Rosin. Published on behalf of the Institute of Fuel, London, by Chapman & Hall Ltd, 1963, 34 pp. 6s

Refinery plants use diethanolamine (DEA) solutions for gas sweetening. The role of DEA is to absorb H2S from sour gas. Amine Regeneration Units (ARU) are used to regenerate the rich Amine with H2S from refinery units to Lean Amine. An ARU unit of a Middle Eastern refinery that began official production in 2020 was simulated using Aspen HYSYS V.11, and an exergy study was conducted on different equipment. Whereas energy is transformed from one form to another, the exergy is destroyed in an irreversible process. The total exergy was equal to the physical and chemical exergy. The physical exergy was calculated using HYSYS, and the chemical exergy was calculated using a series of equations embedded in Excel. The DEA concentration used was 25 wt%. The exergy destruction rates, destruction efficiency, and percentage share of destruction of each piece of equipment were calculated. The regenerator exhibited the highest destruction rate of 13459.73 kW, and a percentage share of 79.61% of the total destruction. The overall exergy efficiency was 99.7%. The DEA concentration decreased from 25% to 20% as a result of system losses during start-up. Therefore, a case study was conducted to test the effect of this decrease in the H2S concentration in the sweet gas, and no effect was observed. An exergy study was conducted using an DEA of 20%. The distribution of the equipment destruction did not change. The total destruction loss increased by 2057.08 kW. From the exergy and operation point of view, the best scenario was to use a 25% concentration, to prevent destruction losses and operation problems.

Carbonization-Plant “Lurgi” Process of Lehigh (N. D.) Briquetting Company

Abstract The first operating installation of the German “Lurgi” process for treating low-grade fuel is described. The process is particularly adapted to North Dakota lignite; and the carbonized-coal residue, with pitch by-product as a binder, is pressed into merchantable briquets, which burn as a smokeless fuel with high recoverable heat value.