Water Curtain Research Articles

Experimental Investigations and Field Applications of Chemical Suppressants for Dust Control in Coal Mines

It is known that high dust concentrations are severely hazardous to health of miners and the safe operations of coal mines. The results of the suppressions of coal dust via chemical dust suppressant methods have been of critical significance, and these methods have been widely applied in coal mines. In this research study, a type of complex dust suppressant composed of surfactants, synergists, and cellulose was prepared. The prepared suppressant was characterized by a high wetting ability and adhesive capacity. The results of the performance tests of this study’s proposed complex dust suppressant showed that its dust sedimentation time was only four seconds, which was observed to be much shorter than that of water alone. Also, the proposed suppressant displayed a viscosity which was 25 times that of water. In this study’s field tests, the proposed complex dust suppressant was used for dust control in a mining roadway of the Zhangcun Coal Mine. The field test results revealed that the average suppression efficiencies of the total dust and respirable dust had reached 89.2% and 87.7%, respectively. Furthermore, a 44.5% increase in the control of the total dust had been observed, and a 65.6% increase in the control of the respirable dust had been achieved with the proposed method, when compared with the results of the previously used water curtain technology.

Study of water curtain effectiveness to fight against vapours of methyl acetate during uncontrolled release

The paper presents results of studies concerning the effectiveness of water curtains in eliminating airborne vapours of methyl acetate. It was found that for methyl acetate the determined effectiveness of water curtains was 13.57 times lower than that of ammonia. In practical terms the absorption rate of methyl acetate vapours equalled to the absorption rate set out for ethanol, but was much lower than for methanol. The obtained results have pointed to the efficiency of water curtains in incidents that comprise uncontrolled release of methyl acetate.

Effectiveness of water sprays in mitigating toxic releases

Water spray curtains are often advertised as means to mitigate the consequences of released chemicals from high pressure tanks. Spray curtain effectiveness claims by certain vendors are misleading—a curtain placed at the periphery of a tank will only scrub a puff of a release. A spray curtain that can effectively contain a consequential release will look very different and cost much more. Studies that demonstrate spray curtains to be effective assume low gas velocities. However, calculations show that pressurized liquid NH3 or HF when released from an orifice to the atmosphere comes out at a high velocity and momentum in the form of a two‐phase jet. The jet must travel quite a distance before the velocity drops enough to be effectively scrubbed by a water curtain. The water curtain therefore needs to be at this large distance and consequently the diameter of the water curtain manifold ring needs to be quite large to be effective. This paper presents engineering calculations to estimate jet velocity, diameter & concentration, calculations to evaluate the efficiency of water sprays and discussion of water spray curtain designs that are more effective. © 2017 American Institute of Chemical Engineers Process Saf Prog 37: 256–262, 2018

Hydro-geochemical analysis of the interplay between the groundwater, host rock and water curtain system for an underground oil storage facility

Hydro-geochemical analysis was performed to investigate the interplay between the groundwater, host rock and water curtain system for the start-up of a pilot underground oil storage facility in China. 54 groundwater samples were collected and analyzed to obtain the characteristics of the hydro-geochemical environment evolution for the start-up period. The groundwater-rock mass interaction was studied with comparing the changes in the ion concentrations, pH values and total dissolved solid concentrations in the groundwater and a mineralogical analysis of the host rock. The groundwater-water curtain system interaction was identified using statistical analysis of the similarity in chemical contents in the groundwater samples. A mixing calculation was performed to evaluate the mixing ratios of the water curtain system, background water and oil/vapor in the seepage water into the storage caverns. It was concluded that calcium carbonate equilibrium is the predominant chemical reaction. The 54 groundwater samples could be classified into 5 clusters. Among the 5 clusters, there is one cluster showing that the tap water injected to the water curtain system is similar in chemical contents to those in the monitoring boreholes around the facility, which confirms the efficiency of the water curtain system for the start-up of the facility. It was found that the two dominant factors influencing the evolution of groundwater chemical content were host rock dissolution and groundwater seepage. Most of seepage water was originated from oil/vapor and water curtain system while the percentage from the background water was almost zero in the start-up period of the facility.

Water Curtain System Pre-design for Crude Oil Storage URCs: A Numerical Modeling and Genetic Programming Approach

In this paper the main criteria of the water curtain system for unlined rock caverns (URCs) is described. By the application of numerical modeling and genetic programming (GP), a method for water curtain system pre-design for Iranian crude oil storage URCs (common dimension worldwide) is presented. A comprehensive set of numerical simulations is performed using the finite element based commercial software (COMSOL 5.1) where the results are used as database for genetic programming. Describing equations of water inflow to the filled and empty caverns and water production rate of water curtain boreholes are generated using GP. By equating the proposed equations to each other, water curtain system can be pre-designed. Relative error of the generated GP equations shows their ability and accuracy. Applying a standard regression coefficient method, sensitivity analysis of parameters related to water curtain performance and water inflow to the caverns is performed as well. The results help the design of the water curtain system for crude oil storage caverns worldwide.

Field tests of pumping-recharge technology for deep confined aquifers and its application to a deep excavation

The execution of deep excavation above confined aquifers asks for dewatering measurements to reduce the hydrostatic pressure so that the safety of the deep excavation can be assured. Dewatering will inevitably cause deformations in the surrounding strata. To reduce the dewatering-induced strata movement, an innovative pumping-recharge technology has been developed in which the dewatering is carried out in the excavation and the recharge is conducted near the protected facilities. However, the capacity and efficiency of this technology in deep confined aquifers need to be further investigated. This paper presents two in-situ pumping-recharge tests in a deep confined aquifer under a deep foundation pit. The feasibility of artificial recharge in the deep confined aquifer has been verified by conducting a single-well pumping and multi-well recharge test with different discharge and injection rates. Then a multi-well pumping-recharge test was carried out in accordance with the requirement and circumstance of construction to evaluate the capacity and efficiency of recharge in controlling the drawdown and ground settlement. The results showed that multi-well recharge could form a water curtain which has a water-proof function to reduce the groundwater drawdown. Meanwhile, by controlling the groundwater head of the confined aquifer during the recharge, the pumping-induced settlement of the surrounding area can be reduced or even eliminated. The pumping effect in the pit would be affected by the recharge around the protected facilities, so it is necessary to take in-situ pumping-recharge tests to determine the layout of wells and the discharge and injection rate. Finally, the artificial recharge was applied to the construction of a deep excavation in Shanghai, and the drawdown and the ground settlement around the protected buildings were effectively controlled by recharge.

Analysis of support requirements for underground water-sealed oil storage cavern in China

The aim of this study is to provide a sound support design for a large-scale underground water-sealed oil storage facility in China. The lithology of this study area consists of reddish-gray, medium-coarse grained granites interpenetrated by diabase, amphibole dioritic porphyrite and aplite. In order to obtain the geotechnical properties of intact rocks and rock masses, detailed field and laboratory studies were carried out. Rock masses at three sites were characterized in terms of Rock Mass Rating (RMR), Rock Mass Quality (Q-system) and Geological Strength Index (GSI), and then rock mass properties of underground caverns were estimated, accordingly. The support systems obtained from empirical methods were analyzed using FLAC3D commercial software considering the effect of the water curtain system. The maximum thickness of plastic zones and the maximum total displacement occurred around underground caverns after installing the support systems suggested by the empirical methods were compared to the unsupported case. The results show that more reliable support design could be obtained by using both empirical rock mass classifications and numerical analysis method.

A constrained Delaunay discretization method for adaptively meshing highly discontinuous geological media

A constrained Delaunay discretization method is developed to generate high-quality doubly adaptive meshes of highly discontinuous geological media. Complex features such as three-dimensional discrete fracture networks (DFNs), tunnels, shafts, slopes, boreholes, water curtains, and drainage systems are taken into account in the mesh generation. The constrained Delaunay triangulation method is used to create adaptive triangular elements on planar fractures. Persson's algorithm (Persson, 2005), based on an analogy between triangular elements and spring networks, is enriched to automatically discretize a planar fracture into mesh points with varying density and smooth-quality gradient. The triangulated planar fractures are treated as planar straight-line graphs (PSLGs) to construct piecewise-linear complex (PLC) for constrained Delaunay tetrahedralization. This guarantees the doubly adaptive characteristic of the resulted mesh: the mesh is adaptive not only along fractures but also in space. The quality of elements is compared with the results from an existing method. It is verified that the present method can generate smoother elements and a better distribution of element aspect ratios. Two numerical simulations are implemented to demonstrate that the present method can be applied to various simulations of complex geological media that contain a large number of discontinuities.

Mitigation of industrial hazards by water spray curtains

A Nowadays, the water spray curtain is recognized as a useful technique to mitigate major industrial hazards. It combines attractive features such as simplicity of use, efficiency and adaptability to different types of risks. In case of accidental toxic gas releases, the spray curtain may be used as a direct-contact reactor exchanging momentum, heat and mass with the gas phase. The cloud is diluted, warmed, and if toxic, some of its toxic content can be absorbed by the droplets to which chemical reactants can be added. In case of fire, water sprays can provide thermal shielding to maintain the integrity of storage tanks. The curtain behaves as a filter and can produce significant attenuation of the incident radiation that impinges on crucial structures such as petro-chemical storage tanks.Both of these applications have been thoroughly investigated at the von Karman Institute The outcome of these research projects is a comprehensive engineering code simulating on the one hand the forced dispersion, heating and physico-chemical inhibition of cold pollutant clouds and on the other hand the thermal shielding performance of a water curtain. The numerical approach is supported by laboratory (including wind tunnel tests) and field tests dedicated to investigate the effects of numerous operating parameters on the water spray curtain efficiency and to build a data base for model validation.The paper gives an overview of the main features of the modeling and on practical industrial applications with a special focus on the adequate water curtain operating conditions and the influence of environmental factors.

Quantifying the effectiveness of impaction by using physical objects as a method for mitigating accidental releases of liquid ammonia and sulfur dioxide

Previous studies on mitigating accidental releases of toxic liquefied gases have mainly focused on the use of water sprays with different shapes. There have been no experimental studies on impaction, in which the released material is impacted against an object and confined to maintain it in the liquid state. To assess the effectiveness of impaction, readily available objects such as metal plates, a fire jacket mounted on a ladder, and a pipe were placed in front of controlled releases (with flow rates of 0.1 and 0.7 kg/s) of sulfur dioxide (SO2) and ammonia (NH3) in an intermediate-scale field trial. Digital scales were used to measure the released and impacted amounts of chemicals, while gas concentrations downwind of the release point were measured with gas analyzers and compared to concentrations determined without impaction. Impaction using a solid object placed close to the release nozzle allowed up to 84% of the released mass to be recovered and attenuated downwind gas concentrations by as much as 85%. Increasing the distance between the object and the nozzle reduced the mass recovery, but it remained above 50%. There were no differences in recovery between releases of SO2 and NH3, indicating that the impaction method is applicable to various kinds of liquefied gases. This study highlights the potential usefulness of impaction as an initial measure to be used in an emergency that can be implemented more simply and with less preparation time than established mitigation methods such as those involving water curtains and foam covering.

Attenuation of thermal radiation through water mist

This article focuses on the interaction of thermal radiation with water droplets and the creation of water mist for the purpose of evaluating the decrease of heat flux when positioning a water curtain of various parameters between a radiation source and a radiometer. The change of water curtain parameters, affecting the passing through of thermal radiation, was performed using five nozzles with a variable spray characteristics. For the respective nozzles the attenuation of thermal radiation was determined and the thermal radiation transmittance was calculated. Water mist was created using a high‐pressure pump and nozzles with a different size of the orifice. The measurement of droplet size was performed using the time‐shift technique. The Omegalux radiant panel was used as the radiation source and the Hukseflux SBG01 radiometer with a working range of 0–5 kW.m−2 was used as the detector. © 2017 American Institute of Chemical Engineers Process Process Saf Prog 37:18–24, 2018

Theory and Simulation of the Relationship between Smoke-proof Water Curtain’s Tank Structure and Flow Non-uniformity

The flow of water in the water tank of the weir-flow smoke-proof water curtain system is analyzed. Fluent software is used to simulate the form and location, the internal and external design of the water tank. The water outlet flow non-uniformity β is used as the evaluation index of the forming quality of the water curtain. The results show that: 1) The water flow state of the rectangular inlet is better than that of square one, and locate the inlet in the middle is overmatched that in flank. 2) The outlet velocity uniformity of setting partition is higher than that without in the internal structure of the water tank. 3) In the design of the external structure of the water tank, the linear proportion of β is increasing with the decrease of the height of the water tank. With the decrease of the width, β is increasing first and then decreasing, and the trend of variety presents a cubic function.

Экранирование тонкораспыленной водой излучения от пожара

The theoretical and experimental study results of finely-dispersed water droplet flow features screening fire heat radiation are shown. Water curtains offer cooling and fire with its danger factor spread prevention (OFP) through window, door and technological openings, outside protected equipment, area or rooms, as well as safe people escape provision from rooms on fire. In designing water curtain generation devices, as a rule, there aren’t taken into account curtain parameters defining their protection features, such as screening factor, droplet diameter and their concentration. Fire protection curtain efficiency depends to a lesser extent on fire temperature but to a greater extent it depends on water droplet diameter and water flow rate. A relatively efficient and water flow-rate-effective curtain can be designed with sprayer generated droplets of less than 200 mm diameter. With droplet size of more than 500 mm the infra-red fire radiation is screened by less than 25 %. Single-fold dispersion for finely-dispersed water with r = 20 mm droplet radius and n = 10 10 m -3 droplet calculated concentration is possible in a few centimetre length. In considering screening curtain features the average Zauter diameter d 32 plays an essential role, particularly it refers to a multiple dispersion that considerably (by 4…5 fold) decreases radiation falling onto the screen. Fine droplets usage d 32 < 100 mm in diameter is connected with certain features of that flow. This also relates to an output sprayer nozzle, the diameter of which greatly effects the size of generated droplets: the less the nozzle diameter, the less average Zauter diameter of the droplets in the spray cone. A great droplet diameter dependence follows from output sprayer nozzle liquid velocity value that turns into a droplet flow while interacting with the ambient air, thereby the greater an output liquid velocity, the smaller the droplets. The experimental data analysis shows that infra-red radiation shade coefficient increase is connected with volumetric droplet concentration (curtain flow rate), and average median diameter decrease (droplet flow dispersion).

Evaluation of optimal water flow and temperature in response to outdoor air temperature in plastic greenhouse with recirculated water curtain system

This study evaluated the optimal supply water temperature and flow rate in response to the outdoor air temperature in order to maintain a target indoor air temperature and minimize the amount of energy required to reheat a recirculated water curtain in a plastic greenhouse. This paper proposed a multiple regression model that estimated the indoor air temperature using the outdoor air and the inlet water temperatures, as well as the water flow rate, as independent variables. We also established a multiple regression model that estimated the average amount of energy required to reheat the recirculated water curtain. To this end, the study analyzed and quantified a reasonable inlet water temperature and water flow rate in response to the outside air temperature using isothermal and iso-energy curves. The results indicated that maintaining a higher water flow rate was preferable to maintaining a higher inlet water temperature for cultivation purposes.

수치모사를 이용한 하천변 수막재배 지역 대수층-하천간 물 유출입의 시기적 변동 정량화

수치모사를 이용한 하천변 수막재배 지역 대수층-하천간 물 유출입의 시기적 변동 정량화

A numerical procedure for modeling the seepage field of water-sealed underground oil and gas storage caverns

Underground rock caverns have been considered as an effective technique for oil storage, commonly with water curtains for maintaining a desired and stable groundwater level and preventing the products from escaping. This study presents a three-dimensional analysis of groundwater flow in the surrounding rocks of water-sealed underground oil storage caverns. The water curtain consisting of numerous boreholes of small diameter, long extension and dense spacing is accurately modeled with a substructure technique. The influence of the oil vapor or mixed gas pressure in the caverns on the groundwater flow is considered by integrating it into the water head and complementary boundary conditions. The proposed method is applied to assess the performance of the water curtain system in the Huangdao oil storage caverns, the first-built underground oil storage project in China. The numerical results show that the gas pressure in the caverns leads to development of gas invasion zones around the cavern roofs, which decreases the thickness of the groundwater barrier and increases the risk of oil and oil vapor leakage. Based on the numerical observations, the design criteria for the water curtain system are discussed and modified.

Hazardous consequence dynamic simulation of LNG spill on water for ship-to-ship bunkering

The significant hazards associated with LNG ship-to-ship bunkering could involve LNG vapour dispersion and LNG pool fires. The boil-off LNG vapour initially behaves as a denser-than-air vapour due to its cryogenic temperature and then is dissipated, as the vapour cloud heated up by surrounding environment. LNG pool fires occur due to either the source ignites immediately or a flash fire burns back to the source. It could cause thermal radiation damage to the surrounding properties or people. Due to different LNG discharge locations, i.e. below waterline, at waterline and above waterline, three possibilities of lumped LNG vapour source planes were compared to investigate the vapour dispersion behaviours and fire radiation hazards in different cases. The present study is aimed at capturing the features of different hazards, analysing the potential hazardous area and investigating a possible mitigation method by applying computational fluid dynamics. Thermal radiant heat flux and temperature were utilised to analyse the material effectiveness on both the LNG bunker and the cargo vessel. The water curtain, which is commonly used to prevent material stress cracking in case of LNG leakage, were considered appropriately to mitigate the radiation hazard.

A Study on Mineralogical and Microbiological Clogging in Water Curtain System of Underground Hydrocarbon Storage Caverns - Calcite and Slime-Forming Bacteria

A Study on Mineralogical and Microbiological Clogging in Water Curtain System of Underground Hydrocarbon Storage Caverns - Calcite and Slime-Forming Bacteria

A study of formative and continuous models for umbrella water curtain based on wall-attaching jets

In this paper, models are established to assess the characteristics of an umbrella water curtain, and two properties on formation and continuity are investigated theoretically. According to flow process of the jets, three computational steps, wall-attaching formation process, wall-attaching flow process and free flow process, are designed to analyze the characteristics. Based on the geometry establishing of an umbrella water curtain, three typical factors, namely, jet velocity, incident angle and wall inclination, are modeled in the first two computational steps to analyze the formative characteristics, and numerical investigation is carried out carefully based on the wall-attaching jets. To analyze the continuous characteristics, a length model on the free flow process is proposed, and an improved Wave-KH model combining with the primary break-up theory are presented to improve its predictive precision. Numerical investigation considering wall length else is also discussed in detail and the biggest factor affecting the continuous performance is revealed. Simulations and experiments are provided to verify the validity of these models, the contrastive results show that models can describe the formative and continuous characteristics more accurate, and models also provide a theoretical basis for fluidic parameter design on an umbrella curtain.

청주 상대리 수막재배지의 지중 침투형 갤러리 설치와 예비 주입시험

청주 상대리 수막재배지의 지중 침투형 갤러리 설치와 예비 주입시험