Measuring Technologies for CFB Solid Circulation Rate: A Review and Future Perspectives

Solid circulation rate (Gs) represents the mass flux of circulating particles in circulating fluidized bed (CFB) systems and is a significant parameter for the design and operation of CFB reactors. Many measuring technologies for Gs have been proposed, though few of them can be applied in industrial units. This paper presents a comprehensive study on measuring technologies, and the results indicate that though the accumulation method is most widely applied, it is constrained by the disturbance of normal particle circulation. Some publications have proposed mathematic models based on pressure drop or other parameters to establish Gs measurement models; these necessitate the accurate modeling of complicated gas-solid flows in industrial devices. Methods based on certain measurement devices to specify parameters like velocity require device endurance in the industrial operation environment and stable local gas-solid flow. The Gs measuring technologies are strongly influenced by local gas-solid flow states, and the packed bed flow in standpipes make the bottom of standpipes an ideal place to realize Gs measurement.

ALGORITHMIC SUPPORT FOR DECISION-MAKING ON THE EFFICIENCY OF OPERATION OF ABSORPTION AND REFRIGERATION PLANTS OF AMMONIA PRODUCTION

The features of the hardware and technological design of the AM-1360 series ammonia synthesis units operating in Ukraine are established, the main of which is the use of heat-using ammonia-water absorption and refrigeration units in the secondary condensation complex. The analysis of the functioning of the absorption and refrigeration units has been carried out. A significant dependence of their efficiency on external disturbances, such as temperature and humidity of atmospheric air, has been established. This causes significant fluctuations in the cooling temperature of the circulating gas in the evaporators of absorption-refrigeration units, which significantly affects the efficiency of ammonia production in general. Based on the results of the analysis of the existing information system, implemented on the basis of the TDC-3000 microprocessor complex, recommendations for its improvement were developed, the presence of which makes it possible to abandon daily analyzes and carry out only control ones to check measuring instruments. Algorithmic support has been developed, implemented in the MATLAB package and tested according to the data of industrial operation of absorption and refrigeration units of the ammonia synthesis unit. This allows the operator, in real production conditions, to obtain operational information on the numerical indicators of the efficiency of operation of absorption and refrigeration units, which characterize their operation to the greatest extent (circulation rate, cooling capacity, circulating gas cooling temperature and thermal coefficient) and make a decision on the possibility of reducing the cooling temperature. of circulation gas in evaporators by changing the frequency of circulation of solutions The created algorithmic software in the MATLAB environment allows embedding a client module, the so-called OPC client. The latter provides technology for free programming of access to current data.

Repurposing End-of-Life Wells for Geothermal Energy Production: An Evaluation of Mississippi Wells

End-of-life production or injection wells may be converted into wellbore heat exchangers for geothermal energy extraction. Whether this conversion is technically and economically feasible depends on several factors such as geothermal potential of the formation, well depth, and working fluid circulation parameters. Here we present a case study where we analyze these parameters and determine their optimum operational brackets. We focus on repurposing active wells that are located in regions with high geothermal potential in the state of Mississippi. Geothermal gradient map of the state of Mississippi was used to select potential candidate wells. Well logs of these candidate wells were used to find formation temperature and other properties such as well diameter and depth. Next, we conducted heat transfer calculations to estimate the temperature rise of various working fluids as a result of circulating inside these wellbores. We ran sensitivity analyses to determine the effect of circulation rate, tubing insulation, and time. Finally, we estimated the power production potential of each well. Our results indicate that geothermal energy production through repurposed end-of-life wells may be viable depending on well depth and geothermal potential of the region. With insulated tubing, the thermal energy delivered by a number of candidate wells is sufficient for a small-scale binary power plant with organic Rankine cycle.

Investment Decisions of the Blockchain-Based Anti-Counterfeiting Traceability Service in A High-Quality Fresh Supply Chain

Applications of the blockchain-based anti-counterfeiting traceability system (hereafter, blockchain-based ACTS) present a positive result in helping improve the repeat purchase rate and the product circulation rate. However, using the blockchain-based ACTS needs chain members’ additional expenditure. They want to know investment conditions about the blockchain-based ACTS and how to coordinate the supply chain. To solve these problems, we chosen a supply chain with one fresh producer and one retailer as the study object. Afterwards, considering the changes of the repeat purchase rate and the product circulation rate, we revised the demand function. Then, we constructed the profit functions before and after adopting the blockchain-based ACTS, and then a price discount and revenue-sharing contract was put forward to coordinate the supply chain. Findings: with the growth of the repurchase rate, benefits of chain members in the proposed three situations will increase. Thus, we can know that after using the blockchain-based ACTS.

Towards zero carbon dioxide concentration in sweet natural gas product from amine sweetening plant

This work presents a two-step method to reduce CO2 concentration of sweet natural gas product from amine sweetening plant via amine blending (Step 1) followed by minor process modification (Step 2). In Step 1, an industrial natural gas sweetening plant was simulated using Aspen HYSYS and the simulation results were validated against the plant data. Afterwards, different blends of methyl diethanolamine and monoethanolamine (MDEA-MEA) and methyl diethanolamine and diethanolamine (MDEA-DEA) were investigated. Then the optimum amine blend of 28 wt.% MDEA and 10 wt.% MEA was reported. The optimum amine blend achieved a significant reduction in CO2 concentration of sweet natural gas of 99.9% compared to the base case (plant data). In Step 2, two types of amine stream splits, i.e., lean amine stream split and semi-lean amine stream split were studied. The study covered split stream amount, absorber recycle stage, and regenerator stage withdrawal. Both types of stream splits attained a significant reduction in CO2 concentration of sweet natural gas product and amine circulation rate compared to Step 1. However, the semi-lean amine stream split was superior to lean amine split with 69.1% and 63.6% reduction in CO2 concentration of sweet natural gas and lean amine circulation rate, respectively.

Effect of Connection Resistance between Cyclones and Backpass on Furnace Solids Suspension Density Profile and Circulation Rates in CFB

The connection section between cyclones and backpass is an important configuration in multi-cyclone circulating fluidized bed boilers (CFB). In this work, the resistance coefficient of different connection modes, and connection resistance distribution from each cyclone outlet to backpass (connection branch) in one mode are defined and calculated, in order to investigate their effects on furnace solids suspension density distribution and circulation rates. Three connection modes with different overall resistance coefficients were tested experimentally and analyzed by a 1.5-dimensional model in a four-cyclone scaling CFB apparatus. Both experimental and theoretical results show that, with larger overall resistance of a connection, there are more solids suspended in the furnace bottom and fewer in the top section. The investigation of the C-type connection has revealed that when the branch resistance of the connection decreases from branch No. 1–4, the solids suspension density and circulation rate from corresponding solids recycle loops (No. 1–4) increase. Moreover, the non-uniformity of connection branch resistance distribution will lead to uneven lateral solids suspension density distribution and circulation rates allocation. This effect is enhanced by growing superficial velocity.

Increase of energy efficiency ratio of a direct evaporative cooler by dynamic behavior with energy and exergy analysis

The present research is about increasing the energy efficiency ratio (EER) in current direct evaporative coolers (DEC) in Iran. Increasing the cooling load and reducing the electrical energy consumption simultaneously (increasing the energy efficiency ratio (EER)) in DEC are the main goals of manufacturers and consumers of this device. When the circulation water pump runs continuously (static state), the circulation water rate is about 1.89 to 2.90 times of the amounts recommended in the reasonable standards. In order to adjust the circulation water rate to the recommended amount by standards, the present study has utilized repetitive cyclic scheduling programs to reduce the circulation rate to the optimal amount, (by turning the circulation pump on and off by dynamic pattern operation). In other words, the circulation pump stays on only for a certain period of a working cycle, and then the pump stays off for the rest of it. The cooling load and EER were measured based on ASHRAE 133 (2015). The results indicated that the cooling load in the dynamic state increased by 5.03 and 6.18 percent compared to the static state at low and high fan speeds, respectively. Moreover, in comparison with the static state, the amount of electrical energy consumed (kW-hr) in the dynamic state decreased by 8.8 and 4.2 percent at low and high fan speeds, respectively. Finally, the coefficient of performance (COP or EER) of the DEC in the dynamic state is increased by 15.16 and 10.78 in comparison with the static state at low and high fan speeds, respectively.

Pump function of the heart in patients with scoliosis in rest and in stress test

The indices of the pump function of the heart in teenagers with scoliosis of the 3d 4 th degree in rest and during stress test are studied. Disorders of the pump function of the heart take place in rest: the heart rate signficantly increases. During physical exercise in patients with scoliosis the increase of minute blood volume is less pronounced than in healthy persons and is realized by the increase of the heart rate and not by the stroke blood volume. It is less economical form of adaptation of the pump function of the heart to physical exercise. The functional reserves for increasing the minute blood volume, volumetric circulation rate in the response to physical exercise are decreased

Evaluation of Water Circulation by Modeling: An Example of Nonpoint Source Management in the Yeongsan River Watershed

Owing to urbanization, impervious areas within watersheds have continuously increased, distorting healthy water circulation systems by reducing soil infiltration and base flow; moreover, increases in surface runoff deteriorate water quality by increasing the inflow of nonpoint sources. In this study, we constructed a Hydrological Simulation Program—Fortran (HSPF) watershed model that applies the impervious area and can set medium- and long-term water circulation management goals for watershed sub-areas. The model was tested using a case study from the Yeongsan River watershed, Korea. The results show that impervious land-cover accounts for 18.47% of the upstream reach in which Gwangju City is located; approximately twice the average for the whole watershed. Depending on the impervious area reduction scenario, direct runoff and nonpoint source load could be reduced by up to 56% and 35%, respectively; the water circulation rate could be improved by up to 16%. Selecting management goals requires the consideration of both policy objectives and budget. For urban areas with large impervious cover, the designation of nonpoint source management areas is required. For new cities, it is necessary to introduce water circulation systems (e.g., low impact development techniques) to improve rainwater penetration and recharge and activate preemptive water circulation.