Experimental and simulation studies on the influence of carbon monoxide on explosion characteristics of methane

In underground coal mining, methane explosions often can cause tremendous disasters. In the meantime, carbon monoxide (CO), generated during the process of coal oxidation, may appear in the air. Therefore, the explosion characteristics of the mixture of CH₄ and CO must be investigated to prevent gas explosion accidents in coal mines. We conducted experiments by using a 20-L nearly spherical gas explosion testing device. The software FLACS was used to simulate the explosion of the mixture of CH₄ and CO at various mixing concentrations, and the simulation results corresponded to experimental results. With the increase of CO concentration, both upper and lower explosive limits of CH₄ decreased. On the whole, the explosion characteristic parameters of CH₄ and the mixture are similar. When CH₄ concentration was below the stoichiometric concentration, the addition of CO could promote the intensity of gas explosion; oppositely, excessive CO would inhibit the gas explosion reaction. The inhibitory effects become more significant as the concentration of CH₄ increases.     

Forward osmosis coupled with lime-soda ash softening for volume minimization of reverse osmosis concentrate and CaCO3 recovery: A case study on the coal chemical industry

• Forward osmosis (FO) coupled with chemical softening for CCI ROC minimization • Effective removal of scale precursor ions by lime-soda ash softening • Enhanced water recovery from 54% to 86% by mitigation of FO membrane scaling • High-purity CaCO₃ was recovered from the softening sludge • Membrane cleaning efficiency of 88.5% was obtained by EDTA for softened ROC Reverse osmosis (RO) is frequently used for water reclamation from treated wastewater or desalination plants. The RO concentrate (ROC) produced from the coal chemical industry (CCI) generally contains refractory organic pollutants and extremely high-concentration inorganic salts with a dissolved solids content of more than 20 g/L contributed by inorganic ions, such as Na⁺, Ca²⁺, Mg²⁺, Cl⁻, and SO₄²⁻. To address this issue, in this study, we focused on coupling forward osmosis (FO) with chemical softening (FO-CS) for the volume minimization of CCI ROC and the recovery of valuable resources in the form of CaCO₃. In the case of the real raw CCI ROC, softening treatment by lime-soda ash was shown to effectively remove Ca²⁺/Ba²⁺ (>98.5%) and Mg²⁺/Sr²⁺/Si (>80%), as well as significantly mitigate membrane scaling during FO. The softened ROC and raw ROC corresponded to a maximum water recovery of 86% and 54%, respectively. During cyclic FO tests (4 × 10 h), a 27% decline in the water flux was observed for raw ROC, whereas only 4% was observed for softened ROC. The cleaning efficiency using EDTA was also found to be considerably higher for softened ROC (88.5%) than that for raw ROC (49.0%). In addition, CaCO₃ (92.2% purity) was recovered from the softening sludge with an average yield of 5.6 kg/m³ treated ROC. This study provides a proof-of-concept demonstration of the FO-CS coupling process for ROC volume minimization and valuable resources recovery, which makes the treatment of CCI ROC more efficient and more economical.     

Efficient allocation of coal de-capacity quota among Chinese provinces: a zero-sum gains data envelopment model

ABSTRACT

An efficient coal de-capacity quota allocation scheme is key for accelerating China’s coal supply-side structure reform. This paper allocates the coal de-capacity quota from the perspective of efficiency to seek the optimal capacity allocation in each Chinese province. First, we estimate the coal capacity of 24 coal-producing provinces based on boundary production function model. According to the actual coal overcapacity in each province, we initially allocate the coal de-capacity quota of reducing 0.8 billion tons among them. Then, we optimize the initial allocation plan by using the zero-sum gains data envelopment model (ZSG-DEA) considering backward coal capacity, coal economic output, and coal resource endowment of each province. The results indicate that: First, there is coal overcapacity all over China, and there are obvious differences among the provinces. Second, the optimal allocation results show that the large coal producing provinces, including Shanxi, Inter Mongolia, Shaanxi, etc., need to undertake most of the coal de-capacity tasks, while the old coal producing provinces in northeast and west China should undertake a heavier burden of coal de-capacity. Third, the “one-size fits-all” approach burdens the small coal producing provinces with reducing coal capacity, leading to a general low enthusiasm for coal de-capacity in these regions.     

空气和煤气吹脱法处理高氨氮废水的对比研究

研究了在实验室使用空气吹脱法去除高浓度氨氮废水的条件,通过正交实验得出其影响因素大小顺序为:废水pH>气液比r>废水温度tw>表面活性剂浓度c,最佳吹脱条件为pH=11.0,r=550,c=10mg/L,tw=75℃,最高氨氮去除效率达到71.4%。在某焦化厂以终冷塔后焦炉煤气为解吸介质,现场试验影响因素大小顺序为:o废水pH>废水温度tw>气液比r>煤气温度tg>表面活性剂浓度c,最佳吹脱条件为pH=11.5,tw=90℃,r=650,tg=55℃,c=20mg/L。为煤气吹脱解吸回收氨工艺的应用提出了建议。     

跳态洗煤废水处理及回用技术的研究

比较了几种无机混凝剂对洗煤废水的处理效果,确定了采用CaCl2作为混凝剂,联合有机絮凝剂PAM处理洗煤废水。结果表明:最佳条件如下,400mL水样中10%的CaCl2溶液加入量为6mL,浓度为0.2%的PAM 6mL,分别以120r/min的搅拌速度搅拌,搅拌90s,最后将水样沉淀25min。     

小康矿煤泥水治理方法的研究

本文针对煤泥水难以自然沉降的问题,研究了煤泥水的性质,提出了新的混凝荆ZL—1与PAM联用的治理方法。该方法简单,处理效果好,处理后上清水完全回用于洗煤,实现了洗水闭路循环。     

煤气化是削减重庆SO2污染的重要途径

解决重庆ＳＯ２污染的较好途径是采用德士古煤气化技术，文中对有关煤气化的投资和经济评估进行了探讨。     

热电厂输灰管的不停运清洗

南屯矸石热电厂通过对管道结垢的成分分析,采取添加除垢剂、缓蚀剂、调节酸量,实行不停运酸洗除灰管道实践获得成功。     

用水淬煤渣混合料代替碎石作为集装箱货场硬化面基层的试验研究

本文通过对热电厂的工业废料──水淬煤渣与土、石灰组成混合料的各种物理、力学性能的试验研究，指出用其代替碎石作为集装箱场硬化面基，不仅可以减少工业废料对城市的污染，而且还可以降低工程造价．     

焦化厂全负压净化回收煤气新工艺

通过对焦化厂全负压净化回收煤气新工艺流程的介绍和新、旧回收工艺的比较，总结出全负压净化回收煤气工艺控制污染的特点与效果，焦化全负压回收利用硫化氢生产硫酸，氰化氢生产黄血盐，从生产工艺上消除了ＳＯ２，ＮＯｘ对大气的污染，解决了硫铵生产紧缺的硫酸，实现了焦化厂煤气净化，回收的清洁生产。