Lock Hopper Research Articles

A deep insight on the coal ash-to-slag transformation behavior during the entrained flow gasification process

Recent research provided deep insight on the coal ash-to-slag transformation characterization during the entrained flow gasification process, with experimentation on a 40 kg/hr (dry basis) coal-fed opposed multi-burner (OMB) entrained flow gasifier and simulation via FactSage™ software. A general mechanism is presented to relate the gasifier design temperature, ash fluid temperature, and operating temperature with the degree of the slag polymerization. The change of the high temperature zone, the corresponding particle residence time in the high temperature zone, and syngas composition have obvious effects on the slag mineral transformation behavior. Mineral types formed on the wall of the gasifier chamber were mainly anorthite (CaAl2Si2O8), aluminum oxide (Al2O3), and calcium sulfide (CaS). These minerals transformed to anorthite and diopside (CaMgSi2O6) at the slag hole zone, while the minerals at the lock hopper were anorthite, orthoclase (KAlSi3O8), quartz (SiO2), gypsum (CaSO4), calcite (CaCO3), and halite (NaCl). FactSage™ predicted minerals as anorthite, diopside, orthoclase, and albite (NaAlSi3O8), etc., where the slag temperature was below the ash fluid temperature and when the ratios of CO/CO2 and (CO + H2)/CO2 were lower than 1.0 and 2.0, respectively. By simulation, residual carbon was found to be the dominant factor over syngas composition to cause mineral transformation, and this was verified experimentally. The Ca-based crystals, typically anorthite, was shifted to diopside, near the slag hole zone, and a linear relationship was found between the content ratios of diopside/(anorthite + diopside), CaO/SiO2, and (CaO + MgO)/SiO2. A dimensionless number, θ, was defined to characterize the changing chemical composition and the degree of slag polymerization, with temperature deviation from the design condition. Three zones of θ were identified and related to the deviation between the actual gasification condition from the design condition. A low slag polymerization degree corresponded with a higher temperature deviation between the actual condition and design condition, and this proved that increased residual carbon content and changing iron valence state increased the mineral types when the slag temperature was below the ash fluid temperature.

Proposals for power generation based on processes consuming biomass-glycerol slurries

A preliminary theoretical feasibility study on the application of new concepts for thermoelectric power generation consuming biomass mixed with glycerol has been completed. Two main alternatives (A and B) have been envisage. At Configuration A, wet sugar-cane bagasse (SCB) is dried at atmospheric pressure. From that, the biomass is mixed with raw glycerol to obtain a high dry-solid content slurry, which is pumped into the gasifier. This greatly simplifies the feeding of particulate solids into pressurized vessels, which otherwise would require costly and cumbersome series of lock hoppers operating sequentially. The produced gas is cleaned to bring the particle content and size as well alkaline concentration within the acceptable limits for injections into standard gas turbines. At Configuration B, the wet SCB is mixed directly with raw glycerol and pumped into the gasifier, therefore dispensing the drying phase. Optimizations of the gasifier characteristics and air injection rates have been conducted having the exergetic efficiency as objective function. In both cases, the complete power generation concepts are optimized aiming the maximization of respective 1st Law efficiencies.

Pneumatic transport characteristics of coarse size pulverized coal for the application of fast circulating fluidized bed gasification

The pneumatic transport characteristics of pulverized coal with very coarse grain size were investigated, especially related to fast circulating fluidized bed gasifier. The lock hopper system was used along with the top discharge blow tank technology to examine the transportation characteristics of pulverized coal. The most important factors among the pulverized coal transportation properties were mass flow rate of pulverized coal and the solid loading ratio, which changed with the amount of fluidization nitrogen and differential pressure between injection hopper and gasifier. The mass flow rate of the pulverized coal and the solid loading ratio were linearly proportional to changes in differential pressure, and were inversely proportional to changes in the amount of fluidization nitrogen. In the case of extended transport line, similar feeding characteristics were obtained by increasing the differential pressure while the level of fluidization nitrogen was kept constant. Pressure losses were observed with changes in the mass flow rate of pulverized coal, solid loading ratio, and the transport gas density in horizontal and vertical, both upward and downward, straight pipelines and at bends. Characteristics of pressure losses under various operating conditions were correlated with the nondimensional numbers such as the Reynolds number, Froude number, solid/gas density ratio, and solid loading ratio. Such correlations were reasonably consistent with the experimental results.

Characteristics of Different Sized Slag Particles from Entrained-Flow Coal Gasification

Gasification slags are byproducts of the coal gasification process, including fine slags (slags from filter) and coarse slags (slags from lock hopper). The characteristics of gasification slags with different particle sizes were investigated by the loss-on-ignition (LOI) method, scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), pore structure analysis, X-ray diffractometry (XRD), and X-ray fluorescence spectrometry (XRF). The relationships between the particle size and the characteristics of slags, which include residual carbon content, surface characteristics, pore structure, crystal mineral content, and ash composition, were analyzed and obtained. For fine slags, carbon content, specific surface area, porosity, and crystal content increase with particle size. For coarse slags, medium sized (105–280 μm) particles contain the most residual carbons and crystal minerals, followed by the smaller (0–105 μm) particles. Si/Al/Ca/Mg/K tends to concentrate in larger coarse slags, while...

Very High-Pressure Fuel-Slurry Integrated Gasifier/Gas Turbine (FSIG/GT) Power Generation Applied to Biomass

The work contributes to the study of the fuel-slurry integrated gasifier/gas turbine (FSIG/GT) concept for the electric power generation process consuming biomass or, more specifically, sugar cane bagasse (SCB). The FSIG/GT process allows for pumping of the solid fuel as a slurry into pressurized reactors, therefore dispensing the need for complex systems of sequential lock hoppers. The slurry drying is achieved through the application of a residual hot gas stream from the process. Because the dryer and gasifier operate at similar pressures, the transfer of particles can be made using simple rotary valves and Archimedes screws. The produced fuel gas is cleaned and injected into the turbine. Previous studies were limited at operational pressures around 2 MPa, while the present evaluates the process working at the vicinity of 10 MPa. This requires intercooling between compression stages as a result of limits of the temperature imposed by the axial compressor blade materials. Rankine cycles are employed to recover energy from the gas-cleaning and exiting process streams as well from the compression intercooling systems. At the present stage investigation, operations at 10 MPa led to overall efficiencies around 34%. That is significantly higher than that presently practiced at power plants of large sugar and alcohol mills but below that achieved in previous studies of FSIG/GT processes consuming SCB and operating around 2 MPa. The main reason for that is attributed to the impossibility of total energy recover and irreversibilities introduced during intercooling. Future works might improve that value.

Investigation into the Flow Properties of Coarse Solid Fuels for Use in Industrial Feed Systems

Material feeding and handling systems have been cited as one of the most common causes of process downtime where thermochemical conversion processes are concerned. New and emerging fuels come in a variety of forms, and if such fuels are to be deployed widely it is imperative that material feeding and handling systems are designed appropriately. This study proposes an approach for designing material feeding and handling systems for use with coarse solid fuels. The data obtained from this study indicates particle size to be one of the key issues affecting the flowability of bulk solids further to the uniformity in particle shape. Coarse bulk solid samples were shown to flow more freely than their milled and pulverised counterparts, generating higher degrees of flowability. The results from this study were also applied to a new feed system used for feeding solid fuels to high pressure processes named the Hydraulic Lock Hopper. In this study the Hydraulic Lock Hopper demonstrated the feeding of wood pellets, torrefied spruce pellets, and ground anthracite coal grains against a pressure of 25 barg in two modes of operation. Energy savings compared to conventional lock hopper systems were recorded in the region of 80%.

煤气化激冷流程锁斗排渣振动分析与解决方案

水煤浆气化、粉煤气化的激冷流程均采用锁斗排渣工艺，都面临着一个共同的问题，锁斗排渣时振动非常大，各公司因为工艺配管的不同差别振动差别也比较大，近年设计院与运行厂家在测试各种方案来解决锁斗排渣振动的问题，例如：锁斗冲洗管线增加弹性支撑、增加波纹软管、改变冲洗水管配管等方式，虽然都有一定效果，但还没有根本的解决振动问题。该振动给高温高压系统管道、设备的安全运行带来极大的风险。本文通过从锁斗振动产生的根本原因入手，彻底解决锁斗排渣振动问题。 Coal water slurry gasification and chilling of pulverized coal gasification process adopt the lock hopper discharge process and are both facing a common problem that the vibration of lock hopper discharge is very obvious. The vibration changes as the process piping of each is different. In recent years, the design institute and coal gasification company have tested different kinds of solutions to solve the vibration of lock hopper, such as adding elastic support or corrugated hose, changing the way of flushing water pipe etc. All these solutions have some certain effects, but the problem still can’t be essentially solved. The vibration to high temperature and high pressure pipeline system, the equipment safe operation brings great risk. This article thoroughly solves this problem by analyzing the root cause of vibration.

Development of a novel solids feed system for high pressure gasification

The Hydraulic Lock Hopper (HLH) embodies a high pressure dry feed system that uses water as an incompressible fluid to bring about compression. No pressurising gas is required, so commonly used inert gases such as nitrogen and carbon dioxide are conserved. The HLH has successfully demonstrated the feeding of solid fuels such as wood pellets to pressures as high as 25barg in two modes of operation. Energy requirements of 15.51kJ/kg (Mode 1) and 20.61kJ/kg (Mode 2) have been recorded which translate to significant energy savings of 81.9% and 75.9% compared to conventional lock hoppers. Energy savings have been projected to increase for Mode 2 where lock gas contamination with syngas takes place, and the mass flow rate has been shown to operate independently of pressure varying between 2 and 2.5tonnes/day. The HLH has also been shown to have a negligible effect on the fuel moisture content with moisture content increases being recorded to be consistently less than 1wt.%.

The Phase Inversion-based Coal-CO2 Slurry (PHICCOS) feeding system: Technoeconomic assessment using coupled multiscale analysis

Coal-CO2 slurry feed is being examined as a way to efficiently feed coal into high-pressure reactors, such as gasifiers, in carbon capture-enabled plants. The preparation of a slurry of coal in liquid carbon dioxide is not trivial and the cost of solutions involving lock hoppers and cryogenic cooling is expected to be high. A novel method for preparing and feeding coal-CO2 slurry has recently been proposed: the Phase Inversion-based Coal-CO2 Slurry (PHICCOS) feeding system operates at ambient temperature, does not require lock hoppers, and inherently reduces the moisture and ash content in the feedstock. This work examines the technoeconomics of the PHICCOS feeding system for high and low-rank coal and compares them with those of commercial technologies. Coupled multiscale analysis, which integrates system-level modeling and component-level modeling, is used here to conduct, for the first time, an integral assessment of the PHICCOS feeding system. The analysis, which uses an Integrated Gasification Combined Cycle power plant as an example application, accounts for multiple aspects of the process that had only been considered individually in the past. Results show that the PHICCOS feeding system is competitive with coal-water slurry feed for bituminous coal gasification and is cheaper than dry feed for low-rank coal. Overall, PHICCOS is the most economic option across coal ranks and offers unique operational advantages, when compared to dry feeding systems, related to high-pressure operation and capability to process high-ash, and high-moisture coal.

Application of Hydrogen Selective Membranes to IGCC

This study considers the integration of Pd-based H2-selective membranes in integrated gasifier combined cycles (IGCC) from both technical and economical point of view. The selected gasification system is based on Shell technology. Two different dry feeding systems are investigated: the first is a state-of-the- art nitrogen-based lock hopper charger while the second uses CO2 as pressurization gas. The net electric efficiency of the two plants is evaluated as a function of the hydrogen recovery factor (HRF) and the membrane feed pressure in order to minimize the membrane surface area. 90% HRF and 54bar feed pressure are the best operating parameters which correspond to a net electric efficiency of 39% both for N2 and CO2 feeding system. The cost of CO2 avoided is calculated as a function of a parameter named MI which represents the membrane development in terms of performances and costs. Results show that an improvement of membrane technology is necessary to match the state-of-the-art CO2 capture plant, even though membranes show good potentiality for cost abatement.

The Fatigue Analysis of Pressure Vessels Based on Workbench

With the rapid development of petrochemical industry, the operation condition of pressure vessels under the alternating load was increasing and the probability of fatigue failure was also on the rise. As a result, pressure vessel fatigue analysis is gaining the designer's attention. This paper describes the key steps and techniques of the fatigue analysis of pressure vessel based on Workbench platform using the lock hopper of the coal chemical industry as an example.

DESIGN OF A PILOT PLANT FOR GASIFICATION OF BIOMASS, MUNICIPAL AND SOLID WASTES

In 2004/2005, a team of undergraduate students undertook an interdisciplinary capstone design project to design a pilot plant to study the gasification of biomass and some forms of solid waste. Gasification is emerging as an environmentally friendly alternative to incineration for converting waste to energy and useful products. Due to the complexity of the reactions in the gasification process, a pilot plant is needed to optimize the process and to produce valuable data for the design of commercial scale units. The pilot plant was designed with a high degree of versatility to process different types of municipal and industrial solid wastes over a wide range of temperatures and pressures, e.g. 0 – 50 psig and 500-1000 oC. A fluidized bed gasifier was designed to maximize the efficiency of solid waste conversion. The oxygen level is carefully controlled to avoid oxidation of organic compounds. The solid waste is pretreated in three stages: drying, crushing and classification. A rotary dryer was designed to reduce the moisture content of the solids to the desired level, as a low level of moisture is required for gasification. The dried material is crushed to reduce the particle size. A fluidized bed reactor requires particles of certain size produced by sieving of crushed particles. Heated air or nitrogen is passed through a distributor plate below the bed to create fluidization. Electrical band heaters were designed to heat the fluidizing gas to the desired temperature. Feed enters the reactor via a screw feeder that is contained within a high pressure zone by a lock hopper. The high pressure zone prevents blowback of dangerous gasses through the feed system. A cross flow heat exchanger with finned tubes was designed to preheat the fluidizing gas. The system is designed to process up to 12 kg/h of feed. Pressure and temperature are measured during the operation for online control of the process. An online gas chromatograph records the composition of products, which can be related to the recorded pressure and temperature and provide useful information for reactor control and enhance the selectivity of the desired product. The students performed CAD modeling of major components, and conducted a simulation study of the gasifier over a range of pressures and temperatures. The project culminated in a final design report containing detailed engineering analysis and a comprehensive set of working drawings.

Rheological Study of Comingled Biomass and Coal Slurries with Hydrothermal Pretreatment†

Gasification of comingled biomass and coal feedstock is an effective means of reducing the net life cycle greenhouse gas emissions in the coal gasification process while maintaining its inherent benefits of abundance and high-energy density. However, feeding a comingled biomass and coal feedstock into a pressurized gasification reactor poses a technical problem. Conventional dry feeding systems, such as lock hoppers and pressurized pneumatic transport, are complex and operationally expensive. A slurry formation of comingled biomass and coal feedstock can be easily fed into the gasification reactor but, in normal conditions, only allows for a small portion of biomass in the mixture. This is a consequence of the hydroscopic and hydrophilic nature of the biomass. The College of Engineering Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside, has developed a process producing high solid content biomass−water slurry using a hydrothermal pretreatment process. In this paper, the systematic investigation of the rheological properties (e.g., shear rate, shear stress, and viscosity) of coal−water slurries, biomass−water slurries, and comingled biomass and coal−water slurries is reported. The solid particle size distribution in the slurry and the initial solid/water ratio were investigated to determine the impact on shear rate and viscosity. This was determined using a rotational rheometer. The experimental results show that larger particle size offers better pumpability. The presence of a high percentage of biomass in solid form significantly decreases slurry pumpability. It is also shown that the solid loading of the biomass−water slurry can be increased to approximately 35 wt % with viscosity of less than 0.7 Pa·s after the pretreatment process. The solid loading increased to approximately 45 wt % when the biomass is comingled with coal.

98/04292 Lock hopper device and the operational method

98/04292 Lock hopper device and the operational method

97/01253 An evaluation of high pressure coal dust explosions

In the United Kingdom an industry-led consortium has been set up to continue the development of a coal-based advanced power generation system. The program primarily addresses the development of the key components for the Air Blown Gasification Cycle (ABGC), previously known as the British Coal Topping Cycle. One of the main features of the ABGC process is the use of an air blown pressurized fluidized bed gasifier which has the advantage over alternative oxygen blown systems, of not requiring air separation equipment. However, as a consequence the ABGC process does not have an available source of nitrogen for purging and pressurizing. Coal in the ABGC process is fed to the gasifier through lock hoppers pressurized up to 25 bar. The storage of coal in air at elevated pressures is associated with an increased propensity for spontaneous heating and dust explosion. This paper describes the experimental work commissioned by the Coal Technology Development Division of British Coal (and undertaken by TNO Prins Maurits Laboratory, Netherlands) to determine the explosive characteristics of a lignite, an anthracite, and a bituminous coal from UK sources over a range of elevated pressures up to 20 bar. Data on the maximum oxygen content, maximum explosion pressuremore » and dust explosion constant are presented. This information will be used to consider the feasibility of alternatives to expensive nitrogen inerting. This will include partial inertization and high pressure dust explosion suppression systems.« less

The variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase

To ensure a trouble-free operation of bulk solids sluice systems, especially lock hoppers, knowledge about the behaviour of bulk solids during and afte

Effects of sudden pressure changes in the surrounding gas phase on flow properties of bulk solids

AbstractThe variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids.

Analysis of solids densification during the pressurization of lock hoppers

Lock hoppers are used to feed solids into high pressure reactor vessels. During the gas pressurization phase of the operating cycle, gas pressure gradients add to the solids stresses caused by gravity, resulting in a gain of density and strength of the solid. The increase of strength may require a larger hopper outlet and, hence, a larger valve at the outlet in order to assure flow without obstructions thus increasing the initial cost and the cost and time of maintenance. Concentric pressurization of a compressible solid from the cylinder walls inward is analyzed. This is a coupled nonlinear diffusion and nonlinear elastic-plastic finite deformation problem in plane strain. The results suggest that the concentric method permits rapid pressurization with little densification.

Flow of slurries of coarse particles at high solids concentrations

AbstractUsing a lock hopper feeding system, gravel and coal shale slurries containing particles of median diameter approximately 4 mm were transported at high concentrations through a pipe of I.D. 7.87 cm at velocities below 3.5 m/s−1. In addition to the usual measurements of velocity, delivered concentration and hydraulic gradient, in‐situ concentrations and particle velocities were determined. With these measurements, a two‐layer model of stratified flow of the type proposed by Wilson was examined and found to give satisfactory predictions. Coefficients of wall friction were found to vary with velocity. Minimum values of these coefficients agreed with the results of direct shear tests. This variation could be attributed to stick‐slip processes at low velocities and a change in the nature of the interparticle stress at higher velocities.

Synthetic oil from coal—the economic impact of five alternatives for making hydrogen from coal and steam

While large-scale liquefaction is approximately 10 to 15 years from fruition, its economic implications are important to assess. This study evaluates the effect of several hydrogen production configurations on the cost of syncrude produced by a general catalytic liquefaction process. The five cases analyzed were: partial oxidation of coal at 44.7,500, and 1000 psia; partial oxidation of char at 1000 psia; and, partial oxidation of process-derived vacuum bottoms at 1000 psia. Material balances for all cases were based on a total coal consumption of 25,000 tons per stream day (TPSD). This study shows that increasing the pressure of partial oxidation from 44.7 to 1000 psia reduces the oil cost by 10 percent. The incremental savings in going from 500 to 1000 psia is only two percent, which may make this increase marginal. The inclusion of a pyrolysis plant, in all cases, resulted in more costly oil. At the highest pressure, coal and vacuum bottoms, Cases 1 aand V, yielded syncrude of comparable cost. No attempt was made to quantify the advantages associated with the vacuum bottoms case, such as less sulfur and nitrogen in the syncrude product, which is also lighter. Operating advantages associated with the elimination of the filtrationmore » step in the liquefaction plant, and lock hopper feeding of coal would produce added benefits for Case V, which have not been included in these cost estimations. Finally, the least costly hydrogen was produced by partial oxidation of coal at 1000 psia.« less