Lignite drying system and technology with superheated steam capable of recycling waste steam heat

Abstract

The invention discloses a lignite drying technology with superheated steam capable of recycling waste steam heat. The lignite drying technology comprises the steps that (1) after raw lignite is fed to an internal-heating fluid bed dryer after being crushed and sieved; (2) saturated steam from a backpressure unit of a factory enters a built-in heat exchanger in the internal-heating fluid bed dryer; the moisture the pulverized lignite is removed through indirect heat exchange; the pulverized lignite that is dried till the moisture content is qualified is discharged from the bottom end of the internal-heating fluid bed dryer; and (3) the saturated steam generates condensate water through the indirect heat exchange; a part of the condensate water is sent to a boiler feed water system; the rest of the condensate water is sent to an evaporator; the steam generated by removing the moisture from the pulverized lignite and fluidized carrier gas are in superheated steam states and are discharged from the top of the internal-heating fluid bed dryer; after the steam and the fluidized carrier gas are dedusted by multiple stages, the steam and the fluidized carrier gas partially return to the internal-heating fluid bed dryer again; and the rest is recycled. Meanwhile, the invention further discloses a system implementing the technology.

Description

[0001] technical field [0002] The invention relates to a lignite drying system and process, in particular to a superheated steam lignite drying system and process in which waste heat steam heat can be recycled. Background technique [0003] The conventional lignite drying process is to use hot flue gas to directly heat the drum dryer and to use steam as the heat source to indirectly heat the drum dryer. Due to the high volatile content of lignite, the former is easily ignited and burned due to the influence of the air inlet temperature, and the drying efficiency is low and the investment in equipment is huge. Due to the need for moisture-carrying gas, the rotary drum dryer using indirect heating has high drying energy consumption, about 1350kg steam / ton of water, and the output of a single machine is small. The lignite pre-dehydration capacity of a 300MW unit is about 60 tons / hour, and multiple units need to be connected in parallel. Considering safety reasons, a nitrogen...

AI Technical Summary

Problems solved by technology

This process uses waste heat steam to prepare superheated steam, which realizes the recycling of part of waste heat steam, but its drying device occupies a large area, has many auxiliary equipment, and the equipment structure is complex, and the waste heat steam produced needs to be purified, purified, and gas The liquid can only be recycled after the liquid is separated, and the water released from the dry material is discharged out of the machine in the form of high-humidity gas and cannot be recycled, and part of the heat is lost

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