AU2013377629B2

AU2013377629B2 - Process and system for upgrading lignite by vibration hot-pressing dehydration

Info

Publication number: AU2013377629B2
Application number: AU2013377629A
Authority: AU
Inventors: Zhidan CAI; Yingjie DAI; Xuelian HU; Guoning LI; Xia Li; Jiongtian Liu; Jiang MA; Xiaoling SHANG; Yukun SHANG; Xin Shi; Yongzhou WAN; Yong Wang; Jianjun Wu; Yixin Zhang; Guoli ZHOU
Original assignee: China University of Mining and Technology CUMT; China University of Mining and Technology Beijing CUMTB
Current assignee: China University of Mining and Technology Beijing CUMTB
Priority date: 2013-02-07
Filing date: 2013-04-19
Publication date: 2017-02-02
Anticipated expiration: 2033-04-19
Also published as: WO2014121558A1; CN103087796A; AU2013377629A1; CN103087796B

Abstract

A process and system for upgrading lignite by vibration hot-pressing dehydration, belonging to processes and systems for coal processing and cleaning. The system: a discharge port of a raw coal bin is connected with a feed port of a fan-milled powder pre-drying device, a discharge port of the fan-milled powder pre-drying device is connected with a feed port of an upgrading device by vibration hot-pressing dehydration through a powdered coal bin and a distributing device, a steam generating device is connected with a steam inlet of the upgrading device by vibration hot-pressing dehydration through a steam switching valve, a water outlet of the vibration hot-pressing dehydration upgrading device is connected with the inlet of the upgrading device by vibration hot-pressing dehydration at one end and is discharged through a waste water purification system at another end, via a three-way valve; the process: the fan-milled coal powders are conveyed into the upgrading device by vibration hot-pressing dehydration, is preheated and then sealed, steam is introduced into the device to heat the coal until the coal is heated to the process temperature, then the introduction of steam is stopped and the coal is dewatered and formed. The lignite can be efficiently dehydrated and formed in a relatively short time under comparatively mild process conditions, preventing reabsorption and spontaneous combustion, so that the lignite can be conveniently stored and transported.

Description

1 2013377629 08 Dec 2016

Process and System for Upgrading Lignite by Vibration Hot-Pressing

Dehydration

Field of the Invention

The present invention relates to a process and system for coal processing and 5 cleaning, particularly to a process and system for upgrading lignite by vibration hot-pressing dehydration.

Background of the Invention

Energy and environment are important factors for sustainable development of national economy and society. By 2020, coal will still account for about 60% of 10 national energy. By 2050, the coal in China’s primary energy will account for about 50%. At present, Inner Mongolia and Northeast China are the largest sources of proved recoverable deposits of lignite in China, accounting for about 3/4 of national lignite recoverable deposits; the reserves of lignite in Southwest China, mostly in Yunnan Province, account for about 1/5 of national lignite recoverable 15 deposits. Lignite is a kind of coal with the lowest degree of coalification. Its main features are: 30%~50% of water content, 15% to 30% of oxygen content, about 50% of high volatile content, low calorific value of about 14MJ/kg, low ash fusion point, large porosity, humic acids in different quantity, strong chemical reactivity and poor thermal stability, which limit the effective utilization of lignite. The research 20 result indicates that after being upgraded and processed by de-ashing and dehydration, the composition and properties of lignite is similar to soft coal, which is convenient for utilization, transport and storage and shows high environmental and economic values.

Currently, multiple processes for upgrading by dehydration have been developed 25 at home and abroad and mainly are divided into two categories: evaporation dehydration and non-evaporation dehydration. The present evaporation dehydration technology uses flue gas or other hot gas as a drying medium, which contacts lignite directly to heat it and evaporate the water in it for drying, resulting in vulnerability of lignite to rupture and less lump coal; as water is removed in a 30 gaseous state, latent heat of vaporization needs to be absorbed, resulting in high energy consumption; as the process is performed at normal pressure and low temperature, the structure of the coal cannot be changed permanently and once in a humid environment, the coal will quickly absorb moisture, thus is not good for storage, long-distance transport and subsequent utilization and processing. The 35 non-evaporation dehydration technology is a method for upgrading by dehydration by which the water in lignite is removed in a liquid state and high-temperature high-pressure steam (or hot oil) is used to change the physical and chemical structures of lignite and convert lignite into coal similar to soft coal. It has a broad development potential. 40 At present, the mechanical and thermal dehydration (MTE) proposed by Strauss et al from German Dortmund University is a relatively mature non-evaporation dehydration technology, but it still has shortcomings such as: requirement for high temperature and pressure; long acting time of hot-pressing dehydration; low production efficiency; uneven axial distribution of pressure in coal, and 45 vulnerability to transverse rupture in the middle of formed coal briquettes. As a whole, due to the influences of many factors, such as: conditions, technology, 2 2013377629 08 Dec 2016 material and economy, further improvement is needed for energy-saving and efficient lignite dehydration process.

Embodiments of the present invention may provide a process and system for upgrading lignite by vibration hot-pressing dehydration, i.e.: mold lignite while 5 upgrading lignite by dehydrating to solve the problem of uneven pressure distribution during hot-pressing dehydration and reabsorption after upgrading by dehydration of lignite.

Summary of the Invention

According to one aspect of the invention, there is provided a process for upgrading 10 lignite by vibration hot-pressing dehydration, characterized in that the upgradingprocess has the following steps: A) The lignite in a raw coal bin is pulverized into particles of below 3mm by a fan-milled powder pre-drying device and then sent to a pulverized coal bin. Through a distributing device, lignite is sent into a device for upgrading by 15 vibration hot-pressing dehydration. After preheating, it is sealed; B) Steam is introduced into the device for upgrading by vibration hot-pressing dehydration to heat lignite to the process temperature. The temperature is substantially 150-220°C and pressure is substantially 5-12MPa. The steam generated by a steam generator directly contacts the coal to heat it. 20 The steam for heating comes from a boiler. The lignite is subjected to vibration hot-pressing dehydration and molding. The static pressure of molding is substantially 5~12MPa. The amount and frequency of the exciting force of vibration are adjustable; C) Demold after dehydration and molding. After cooling, the coal briquettes 25 are sent to a final product bin. The coal powder generated during cooling is sent back to the distributing device; D) After dehydration and molding, the coal is utilized as upgraded lignite. The removed water is treated and discharged after it preheats coal to be preheated. 30 According to another aspect of the invention, there is provided a system for implementing a process for upgrading lignite by vibration hot-pressing dehydration, the system includes: raw coal bin, fan-milled powder pre-drying device, pulverized coal bin, distributing device, device for upgrading by vibration hot-pressing dehydration, three-way valve, wastewater purification system, steam switching 35 valve and steam generator; the discharge port of the raw coal bin is connected to the feed port of the fan-milled powder pre-drying device, the discharge port of the fan-milled powder pre-drying device is connected to the feed port of the device for upgrading by vibration hot-pressing dehydration via the pulverized coal bin and the distributing device, the steam generator is connected to the steam inlet of the 40 device for upgrading by vibration hot-pressing dehydration via the steam switching valve, one end of the water discharge port of the device for upgrading by vibration hot-pressing dehydration is connected to the feed port of the device for upgrading by vibration hot-pressing dehydration via a three way valve, and at the other end, water is discharged through the wastewater purification system. 45 Beneficial Effects of the Invention 3 2013377629 08 Dec 2016

Beneficial Effects

As the above solution is adopted, in the vibration, mechanical and hot-pressing dehydration process, under the synergistic effect of vibration, static pressure and heat, lignite can be efficiently dehydrated under moderate process conditions in a 5 short acting time and form coal briquettes with certain strength, which can effectively prevent reabsorption and spontaneous combustion and is convenient for storage and transport. Moreover, this process system is simple, its process conditions can be easily realized and its production process is safe. It has a good prospect in industrial application. 10 A vibratory compaction system is adopted. As coal is under the synergistic effect of static pressure and exciting force, the transfer of pressure in coal can be effectively improved, thus the axial distribution of pressure in coal becomes more uniform and low strength and transverse rupture of molded coal briquettes resulting from small pressure in the middle part can be avoided; 15 Exciting force may accelerate dehydration and molding of lignite, shorten squeezing time and increase production efficiency;

Saturated steam is used to directly heat coal. The saturated steam experiences phase change and releases latent heat to enhance the heat exchange with coal, raise heat exchange efficiency and shorten heating time. Further, saturated steam is easy to 20 obtain in industrial production;

After the coal is heated, the properties of the organic functional groups on coal surface and the physical performance of water in coal will be changed. The coal surface becomes more hydrophobic and the viscosity, density and surface tension of water are reduced, such that water can be easily removed from coal; 25 Under mechanical pressure, with the help of squeezing and pore volume reduction, water is removed. The melting of waxy and asphaltene substances also are beneficial to squeezing;

The change of the properties of functional groups and pore structure enables dehydrated and molded coal briquettes to effectively avoid reabsorption and 30 spontaneous combustion;

Water is removed in a liquid state and there is no need to absorb latent heat of vaporization, so the thermal efficiency is high;

Moderate process condition and high dehydration efficiency: the temperature is 150-220°C and the static pressure is 5~12MPa. The water content of lignite may 35 be reduced to 10%. It solves the current problems of uneven pressure distribution of hot-pressing dehydration and vulnerability of lignite to reabsorption after upgrading by dehydration and achieves the object of the present invention.

Brief Description of the Drawings

Description of the Drawings 40 FIG. 1 is a device system diagram of the present invention.

In the diagram: 1. raw coal bin; 2. Fan-milled powder pre-drying device; 3. pulverized coal bin; 4. distributing device; 5. device for upgrading by vibration hot-pressing dehydration; 6. three way valve; 7. wastewater purification system; 8. 4 steam switching valve; 9. steam generator.

Detailed Description of the Embodiments Embodiments of the Invention

The present invention will now be described in more detail with reference to FIG. 1, but this is not limitation to the present invention.

Example 1: the upgrading process has the following steps: A) The lignite in raw coal bin 1 is pulverized into particles of below 3mm by fan-milled powder pre-drying device 2 and then sent to pulverized coal bin 3. Through distributing device 4, lignite is sent into device for upgrading by vibration hot-pressing dehydration 5. After preheating, it is sealed; B) Steam is introduced into device for upgrading by vibration hot-pressing dehydration 5 to heat lignite to the process temperature. The temperature is 150~220°C and pressure is 5~12MPa. The steam generated by steam generator 8 directly contacts the coal to heat it. The heating steam comes from a boiler. The lignite is subjected to vibration hot-pressing dehydration and molding. The static pressure of molding is 5~12MPa. The amount and frequency of the exciting force of vibration are adjustable; C) Demold after dehydration and molding. After cooling, the coal briquettes are sent to a final product bin. The coal powder generated during cooling is sent back to distributing device 4; D) After dehydration and molding, the coal is utilized as upgraded lignite. The removed water is treated and discharged after it preheats coal to be preheated.

The devices include: raw coal bin 1, fan-milled powder pre-drying device 2, pulverized coal bin 3, distributing device 4, device for upgrading by vibration hot-pressing dehydration 5, three way valve 6, wastewater purification system 7, steam switching valve 8 and steam generator 9; the discharge port of raw coal bin 1 is connected to the feed port of fan-milled powder pre-drying device 2, the discharge port of fan-milled powder pre-drying device 2 is connected to the feed port of device for upgrading by vibration hot-pressing dehydration 5 via pulverized coal bin 3 and distributing device 4, steam generator 9 is connected to the steam inlet of device for upgrading by vibration hot-pressing dehydration 5 via steam switching valve 8, one end of the water discharge port of device for upgrading by vibration hot-pressing dehydration 5 is connected to the feed port of device for upgrading by vibration hot-pressing dehydration 5 via three way valve 6, and at the other end, water is discharged through wastewater purification system 7.

The lignite in raw coal bin 1 is delivered to fan-milled powder pre-drying device 2 and pulverized into particles of below 3mm and then is sent to pulverized coal bin 3. Through distributing device 4, the coal powder is loaded to device for upgrading by vibration hot-pressing dehydration 5. The water removed from the coal in the previous process step is used to preheat the coal powder. After preheating, the material cylinder is sealed and steam switching valve 8 is opened. After lignite is heated with steam to the predetermined temperature, steam switching valve 8 is closed. Then the coal is upgraded by vibration hot-pressing dehydration. After dehydration and molding, the coal is utilized as upgraded lignite. The removed 5 2013377629 08 Dec 2016 water has high temperature and is used to preheat the coal in next batch. When the removed water has much impurity, it should enter wastewater purification system 7 and be purified before discharge.

The term “comprise” and variants of that term such as “comprises” or “comprising” 5 are used herein to denote the inclusion of a stated integer or integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required.

Reference to prior art disclosures in this specification is not an admission that the disclosures constitute common general knowledge in Australia or any other country. 10

Claims

Claims

1. A process for upgrading lignite by vibration hot-pressing dehydration, characterized in that the upgrading process has the following steps: A) the lignite in a raw coal bin is pulverized into particles of below 3mm by a fan-milled powder pre-drying device and then sent to a pulverized coal bin, and through a distributing device, lignite is sent into a device for upgrading by vibration hot-pressing dehydration, after preheating, the device for upgrading by vibration hot-pressing dehydration is sealed; B) steam is introduced into the device for upgrading by vibration hot-pressing dehydration to heat lignite to a process temperature, the temperature is substantially 150-220°C and pressure is substantially 5~12MPa, steam generated by a steam generator directly contacts the coal to heat it, the heating steam comes from a boiler, the lignite is subjected to vibration hot-pressing dehydration and molding, the static pressure of molding is substantially 5~12MPa, the amount and frequency of a exciting force of vibration are adjustable; C) demolding after dehydration and molding, and after cooling, coal briquettes are sent to a product bin, coal powder generated during cooling is sent back to the distributing device; D) after dehydration and molding, the coal is utilized as upgraded lignite, removed water is treated and discharged after it preheats coal to be preheated.
2. A system for implementing a process for upgrading lignite by vibration hot-pressing dehydration, the system includes: raw coal bin, fan-milled powder pre-drying device, pulverized coal bin, distributing device, device for upgrading by vibration hot-pressing dehydration, three way valve, wastewater purification system, steam switching valve, and steam generator; characterized in that a discharge port of the raw coal bin is connected to a feed port of the fan-milled powder pre-drying device, a discharge port of the fan-milled powder pre-drying device is connected to a feed port of the device for upgrading by vibration hot-pressing dehydration via the pulverized coal bin and the distributing device, the steam generator is connected to a steam inlet of the device for upgrading by vibration hot-pressing dehydration via the steam switching valve, one end of a water discharge port of the device for upgrading by vibration hot-pressing dehydration is connected to the feed port of the device for upgrading by vibration hot-pressing dehydration via the three way valve, and at another end, water is discharged through the wastewater purification system.