污泥热干化系统热量衡算和节能分析

以郑州市马头岗污泥处理厂200t/d(80%)污泥干化系统作为污泥热干化热量衡算研究对象,计算各换热设备的换热效率,分析系统各阶段热量利用率,探讨提高干化热量利用率的有效途径。在该系统中,将含水率80%的污泥干化至含水率23%的污泥,需饱和蒸汽热量15491.5MJ/h。若利用蒸汽凝液回水对载气(空气25℃→110℃)预热,可节约热量169.218MJ/h;若利用蒸汽凝液回水对进泥(25℃→75℃)预热,可节约热量477.414MJ/h;若利用蒸汽凝液回水对锅炉配风(空气25℃→100℃)预热,可节约热量522.585MJ/h。     

燃煤机组耦合蒸气干化污泥能耗特性试验

煤与蒸气干化污泥耦合掺烧是一种大规模处置污泥的技术手段,而蒸气干化污泥掺烧对机组能耗的影响规律尚不明确。对某350 MW燃煤机组开展蒸气干化污泥掺烧性能试验,研究蒸气干化污泥对锅炉效率、厂用电率、汽机热耗率、机组能耗率等的影响。试验期间,湿污泥处理量设定为8.00 t/h,利用污泥干化机将湿污泥含水率从80%分别干化至60%、40%。结果表明,蒸气干化污泥耦合发电时,机组能耗率上升,其中,锅炉效率下降主要是因为排烟热损失和固体未完全燃烧热损失增加,汽机热耗率上升是由于干化蒸气消耗,机组厂用电率上升主要是由于风机系统电耗和脱硫系统电耗上升。污泥干化程度越高,锅炉效率下降幅度越小,汽机热耗率上升幅度越大,机组厂用电率上升幅度越小。利用蒸气将污泥含水率从80%干化至40%,机组供电燃料耗率略有下降,机组供电燃料耗率变化量从2.039 g/kWh降至1.904 g/kWh。当机组掺烧湿污泥时,锅炉效率下降和厂用电率上升是造成机组能耗率上升的主要因素;当机组掺烧蒸气干化污泥时,汽机热耗率上升是导致机组能耗率上升的关键因素。本研究为蒸气干化污泥耦合发电机组能耗评估提供了理论和数据支撑。     

市政污泥的燃料资源化利用

参考垃圾衍生燃料的制备方法考察了市政污泥作为能源的可行性及利用价值,研究了污泥资源化利用前的最佳脱水干化条件及煤粉添加量对污泥燃烧效果的影响. 结果表明,污泥热源干化的最佳时间为4 h,干化后污泥的发热量在18 MJ/kg左右,能量较高,且污泥的发热量随含水率和有机物含量变化而变化. 当干化温度在105~150℃之间时,污泥的可燃有效成分几乎无变化. 污泥含H量较高,燃烧时会有大量挥发分燃烧,这也是污泥燃点低于煤的原因.     

低温热干化技术在某废水厂污泥减量中的应用

将以压力0.3 MPa、温度142℃蒸汽为热源的低温热干化技术,应用于某石化园区废水厂污泥减量化处理中。经考核检测:进料湿污泥含水率为86.7%～97.1%,平均含水率为88.8%,干化后含水率为5.5%～19.9%,平均含水率为8.4%;处理湿污泥运行成本约178.2元/t,具有很好的经济效益和环境效益,能起到低碳高效污泥处理的示范作用,可为同类项目实施提供借鉴。     

市政污水污泥水热耦合干化系统能耗模拟

干化+焚烧技术已逐渐成为我国大中城市中心城区污泥的重要处置手段，水热炭化预处理可提高污泥脱水性能，进而降低系统能耗，但对水热+干化污泥预处置过程的能耗分析还鲜有报道。研究了200～260℃下水热炭化预处理污泥的三相产物分布及水热液有机组分构成，在此基础上建立了水热+空气干化系统的能量-质量流模型，并分析了水热条件对系统能耗的影响，最后与空气干化系统、厌氧发酵+空气干化系统能耗进行对比。发现釜内压力为8 MPa,水热反应温度由200℃上升至240℃时，由于水热液中热值较高的有机组分芳香烃、含氮杂环比例明显下降，水热反应釜能耗由184kJ/kg(以原污泥计)降至161 kJ/kg,温度上升至260℃时，由于水蒸气气相分率明显增加及水热液中芳香烃含量回升，能耗上升至278 kJ/kg。受水蒸气气相分率影响，240℃下水热反应能耗随压力升高而降低，压力升至4 MPa后降低趋势迅速放缓。直接空气干化系统在干化空气温度为110℃时，系统总能耗为1 942 kJ/kg;厌氧消化+干化系统由于对沼气进行高效热回收利用，消化时间为10 d时，系统热耗低至212 kJ/kg,总能耗为984 kJ/kg;而...     

一种新型污泥干化设备的研究与开发

通过利用热泵作为热源对污水处理厂的湿污泥进行干化处理的中试试验,分析该干化技术在运行费、二次污染等方面的可行性及优势,判断该干化技术的推广应用前景。污泥干化过程中不会产生臭气等二次污染,干化后污泥含水率可以达到10%。     

太阳能在污泥处理中的研究进展

剩余污泥作为污水处理厂的副产物,是政府和污水处理厂面临的一个严峻问题,并且处理成本占污水处理总成本的50%~60%。本文介绍太阳能在污泥处理中的发展情况,主要阐述太阳能污泥干化的工作原理、影响因素、干化装置及国内外干化技术工艺,详细介绍部分干化工艺技术。对太阳能在污泥堆肥和污泥热解利用方面进行介绍。太阳能高效集热系统的研发和热泵作为辅助热源的实现,能够大大降低污泥处理所需费用,还为太阳能利用开辟新途径。     

利用太阳能和高温热泵的城市污泥热干化系统技术研究

太阳能是取之不尽的能源，高温双热源热泵也是节能型产品，节能率比普通热泵高70％。所以将太阳能与热泵组合作为热源对城市污泥进行热干化，热干化的污泥可以作为燃料进行焚烧，具有极大的应用潜力。介绍了利用太阳能和热泵作为热源，利用干燥机对城市污泥进行热干化的系统结构、工作原理和实验研究。该系统也可应用于干燥其它物料，如食品、药材等。     

燃煤耦合污泥焚烧发电技术研究进展

焚烧法作为实现我国污泥快速减量化、无害化处置的主流方式得到广泛应用,而在“双碳”减排目标的推动下,燃煤耦合污泥焚烧发电技术能有效实现燃煤低碳减排和污泥清洁焚烧处置。然而,现阶段燃煤耦合污泥焚烧发电技术在锅炉结焦结渣、燃烧污染物排放和技术经济性等方面仍存在较多问题。总结了污泥基本理化性质、水分赋存形态、煤质指标和不同干化技术,对比分析了湿污泥直接掺烧、烟气直接干化污泥后掺烧和饱和蒸气间接干化污泥后掺烧这3种技术路线的优缺点,并结合我国燃煤耦合污泥发电典型工程项目的技术参数进行深入分析。实践表明,湿污泥直接掺烧存在燃烧工况稳定性差、处置量低等问题,而“干化+掺烧”技术路线能在保证燃烧热稳定性的基础上实现较大的污泥处置量。考虑到烟气直接干化污泥存在粉尘爆炸风险高、烟气量需求大等问题,利用饱和蒸气间接干化污泥后掺烧燃烧效果较好。在污泥间接干化技术中,桨叶式干化和圆盘式干化热效率高、粉尘产生量低、占地面积小。由于污泥干化过程中存在黏滞性,需选取合适的干化模型对传热传质过程进行分析。我国燃煤耦合污泥发电典型工程项目运行实践表明,污泥掺烧比例控制在较佳范围时,既能保证燃煤机组燃烧热效率,又能满足常规...     

污泥干化技术的应用现状

污泥干化是利用热物理的原理对污泥中的水分进行排除,从而达到干燥污泥、缩小污泥体积、提高污泥热值的目的。应用自然热源的干化过程称为自然干化,主要包括污泥干化场、太阳能干化床、生物干化和芦苇干化床。使用人工热源的干化过程为人工干化。本文对各种干化技术的应用现状进行了详细的介绍,以期为污泥干化技术的比较与选择提供指导。     

重整C9芳烃分馏塔冷凝潜热综合利用新工艺

基于重整C9芳烃分离装置塔顶油气冷凝潜热的特点,分析对比现有换热工艺及几种新的节能新工艺,研究发现,利用二塔塔顶油气生产0.4 MPa饱和水蒸气,二塔塔釜分别设加热热源工艺和分馏塔热集成与塔顶油气生产0.4 MPa水蒸气联合运用工艺,二者节能效果相当,但是后者装置外提供的一次能量较前者小,因此分馏塔热集成与塔顶油气生产...     

天津石化PTA的节能新技术

详述氧化工序低温位能量回收和超低压透平应用。采用低温 (186℃ )、低压 (1.1MPa) ,每tPTA的动力能耗同比节约标油14 .96kg;工艺上采用 5级冷凝冷却器把反应气相排出物冷却到 40℃ ,使其前 4台产生回收蒸汽 ,可回收热量 2 5 9.5 5GJ/h ,占排出热量的 96.1%。整个氧化反应过程回收的总热量达到 2 85 .0 9GJ/h ,占总反应热量的 88.9%。回收的低温位热能用以推动超低压透平 ,使之可以完全带动空压机 ,还供应醋酸脱水塔的全部热源。加之精制工段加热炉节能和分段结晶热回收 ,使该装置每tPTA的综合耗能考核值只有标油 14 4kg     

COMPARISON OF SUPERHEATED STEAM AND AIR OPERATED SPRAY DRYERS USING COMPUTATIONAL FLUID DYNAMICS.

In this paper a numerical simulation of a spray dryer using the computational fluid dynamics (CFD) code Fluent is described. This simulation is based on a discrete droplet model and solve the partial differential equations of momentum, heat and mass conservation for both gas and dispersed phase.

The model is used to simulate the behaviour of a pilot scale spray dryer operated with two drying media : superheated steam and air Considering that there is no risk of powder ignition in superheated steam, we choosed a rather high inlet temperature (973 K). For the simulation, drop size spectrum is represented by 6 discrete droplets diameters, fitting to an experimental droplets size distribution and all droplets are injected at the same velocity, equal to the calculated velocity of the liquid sheet at the nozzle orifice.

It is showed that the model can evaluate the most important features of a spray dryer : temperature distribution inside the chamber, velocity of gas, droplets trajectories as well as deposits on the walls. The model predicts a fast down flowing core jet surrounded by a large recirculation zone. Using superheated steam or air as a drying medium shows only slight differences in flow patterns. Except for the recirculation which is tighter in steam.

The general behaviour of droplets in air or steam are quite the same : smallest droplets are entrained by the central core and largest ones are taken into the recirculation zone. In superheated steam, the droplets penetrate to a greater extent in the recirculation zone. Also, they evaporate faster. The contours of gas temperature reflect these differences as these two aspects are strongly coupled. In both air and steam there is a “cool” zone which is narrower in steam than in air. Finally, the panicle deposit problem seems to be more pronounced in air than in steam.

Adding to the inherent interest in using superheated steam as a drying medium, the model predicts attractive behaviour for spray drying with superheated steam. In particular. under the conditions tested with the model, a higher volumetric drying rate is obtained in superheated steam.     

Superheated Steam Drying: An Overview of Pilot and Industrial Dryers with a Focus on Energy Efficiency

According to the principle of sustainability, modern industry should preserve nonrenewable energy sources and develop more efficient processes, especially in terms of energy consumption. The depletion of fossil energy reserves, the environmental impact of greenhouse gases, and the possible threats of environmental taxes are the main reasons to develop new processes in general, and new drying processes in particular, for the existing industries. Using superheated steam as a drying medium instead of hot air can improve the energy efficiency by reusing the energy from exhausted steam and prevent gas emission into the atmosphere by condensation. The present review is focused on both lab-scale pilots—including impingement jet, fluid bed, kiln, fixed bed, and flash drying—described in the literature and existing industrial facilities, with a specific analysis focused on energy efficiency. The usefulness of superheated steam drying pilots for experimental research and for the design of industrial dryers is analyzed. The impact on quality specifications of the dried product for different operating conditions is also presented. Documentation on industrial superheated steam dryers is very rare. Nevertheless, this work presents and analyses the key data available for superheated steam drying of beet, alfalfa, industrial pulp, and paint sludge. Energy recovery and process integration, with a focus on specific technological challenges for industrial dryer implementation, are also presented. This document will result in a discussion of some new ideas for possible R&D in superheated steam drying.     

基于蒸汽压缩技术的热泵蒸汽系统热力性能分析

热泵蒸汽技术相比电锅炉及燃煤、燃气锅炉制取蒸汽,具有更高的一次能源利用效率,并且不产生CO₂和NO_x,符合我国节能环保发展战略。本文提出一种基于蒸汽压缩技术的热泵蒸汽系统,采用两级冷凝直接制取低压蒸汽,再通过蒸汽压缩升压至0.7MPa。并基于EES软件建立数值模型,分析冷凝温度T_cond、蒸发温度T_evap、经济器温度T_econ、喷气率β_g对冷媒压缩机功耗W_refri、蒸汽压缩机功耗W_vapor和系统能效系数COP的影响。结果如下：基于蒸汽压缩的热泵蒸汽系统,制取165℃的饱和蒸汽,在T_evap为50℃、T_cond为93℃时,系统COP为2.996,制取1t蒸汽消耗功率仅为247kW·h;系统COP随T_evap的升高逐渐增大,但是T_evap的升高需要更高的热源温度;蒸发温度不变时,系统存在最佳的T_cond、中间冷却温度T_econ和喷气率β_g,当蒸发温度T_evap为50℃,最佳冷凝温度T_cond为93℃时,最佳经济器温度T_econ为65℃,最佳喷气率β_g为0.13。     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.     

OPTIMAL OPERATION OF A CONCURRENT-FLOW CORN DRYER WITH A DRYING HEAT PUMP USING SUPERHEATED STEAM

A numerical model of a concurrent-flow dryer of corn using superheated steam as drying medium is solved applying a shooting technique, so as to satisfy boundary conditions imposed by the optimal design of a drying heat pump. The drying heat pump is based on the theory of minimum energy cycles. The solution of the model proves the applicability of the heat pump to a concurrent-flow dryer, achieving a Specific Energy Consumption as low as 1080 kJ/kg     

过热蒸汽干燥技术的研究进展

过热蒸汽干燥技术具有安全、节能、环保等诸多优点,越来越受到广泛关注。对过热蒸汽干燥技术进行了简介,分析了其优缺点。总结了过热蒸汽干燥的理论研究进展,并对过热蒸汽干燥技术在食品、木材、纸张、污泥和和褐煤等物料的应用现状进行了综合评述。总而言之,过热蒸汽干燥技术是一种先进的干燥技术,具有广阔的应用前景。     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

Abstract

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.