Method and process for upgrading lignite by collaborative optimization of drying and dry sorting

Abstract

The present invention is directed towards a process for upgrading lignite comprising: prior to production pre-assess the calorific value of the coal, by selecting a relational expression between a calorific value of lignite and a degree of metamorphism, a moisture content and an ash content thereof based on a ratio of the ash content to the moisture content, pre-assess the calorific value of the coal; combining a relational expression between a production cost and the ash content and moisture content to make a cost budget; determining degrees of deashing and drying; selecting and implementing a lignite ash reduction pretreatment process; and implementing dry sorting first and then drying. The upgrading process has high sorting efficiency, high drying efficiency and low production cost, and meets the requirement for the surface moisture of the raw coal in the dry sorting operation.

Claims

1. A method for upgrading lignite comprising: (1) prior to production, pre-assessing the calorific value of raw coal by selecting a relational expression between the calorific value of the coal and a degree of metamorphism, the moisture content and the ash content thereof based on a ratio of the ash content to the moisture content, and (2) making a cost budget by combining a relational expression between production cost the ash content, and moisture content; (3) determining degrees of deashing and drying of the lignite, and; (4) selecting and implementing a lignite ash reduction pretreatment process.

2. The method for upgrading lignite according to claim 1, wherein the relational expression between the calorific value of the lignite and the ash content and moisture content thereof is as follows:
Q.sub.gr,d=23.34−0.26285M.sub.t−0.21954A.sub.d+0.16979V.sub.ar−0.00147V.sub.daf.sup.2  (1) wherein, Q.sub.gr,d represents the calorific value of the lignite, M.sub.t represents a total moisture content of the coal, A.sub.d represents the ash content of the coal, V.sub.ar represents the ash content of an as-received basis, and V.sub.daf represents a volatile content of a dry ash-free basis.

3. The method for upgrading lignite according to claim 1, wherein the relational expression between the production cost (S) and the ash content (A.sub.d) and moisture content (M.sub.ad) of the coal is as follows: $\begin{array}{cc}S=\omega .Math.M_{\mathrm{ad}}+\gamma .Math.A_d& \left(2\right)\\ H_{\mathrm{MA}}=\frac{\omega }{\gamma }& \left(3\right)\end{array}$ wherein, H.sub.MA represents a tangent point between an iso-cost line and the calorific value, namely a lowest point of the production cost; S represents the production cost; A.sub.d represents the ash content of the coal; M.sub.ad represents the moisture content; ω represents a proportion of moisture removed during the sorting process; γ represents a proportion of ash removed during the sorting process.

4. The method for upgrading lignite by according to claim 1, wherein the lignite ash reduction pretreatment process comprising: 1) feeding the lignite to X-ray dry sorting equipment, composite dry sorting equipment or fluidized-bed equipment to partially remove gangue, so as to reduce an energy loss in the lignite drying process; and 2) allowing the lignite after the gangue removal to enter microwave, vibrating mixed-flow or fluidized-bed equipment for drying.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of a process according to the disclosure.

(2) FIG. 2 is a flowchart of an example according to the disclosure.

DETAILED DESCRIPTION

(3) As shown in FIG. 1, the disclosure provides an optimized upgrading method, including: selecting, optimizing and combining appropriate drying and dry sorting processes based on a relationship between a calorific value of lignite and a moisture content and an ash content thereof as well as a production cost required by a production process, and implementing the dry sorting process first and then the drying process 9: (1) Before production, select a relational expression between the calorific value of the coal and a degree of metamorphism, the moisture content and the ash content thereof based on a ratio of the ash content to the moisture content, to pre-assess the calorific value 2 of the coal. (2) Combine a relational expression between the production cost 3 and the ash content, and moisture content to make a cost budget; (3) determine degrees of deashing and drying; (4) and select a lignite ash reduction pretreatment process.

(4) The relational expression between the calorific value of lignite and the ash content and moisture content thereof is as follows:
Q.sub.gr,d=23.34−0.26285M.sub.t−0.21954A.sub.d+0.16979V.sub.ar−0.00147V.sub.daf.sup.2  (1)

(5) In the equation, Q.sub.gr,d represents the calorific value of lignite, M.sub.t represents a total moisture content of the coal, A.sub.d represents the ash content of the coal, V.sub.ar represents the ash content of an as-received basis, and V.sub.daf represents a volatile content of a dry ash-free basis.

(6) The relational expression between the production cost and the ash content and moisture content of the coal is as follows:

(7) $\begin{array}{cc}S=\omega .Math.M_{\mathrm{ad}}+\gamma .Math.A_d& \left(2\right)\\ H_{\mathrm{MA}}=\frac{\omega }{\gamma }& \left(3\right)\end{array}$

(8) In the equation, H.sub.MA represents a tangent point between an iso-cost line and the calorific value, namely a lowest point of the production cost; S represents the production cost 3; A.sub.d represents the ash content of the coal; M.sub.ad represents the moisture content; ω represents a proportion of moisture removed during the sorting process; γ represents a proportion of ash removed during the sorting process.

(9) The lignite ash reduction pretreatment process is a process to first preliminarily reduce ash or to deash 5, then dry the lignite 9: first feed the lignite to X-ray dry sorting equipment 4, composite dry sorting equipment 6 or fluidized-bed equipment 7 to deash and to partially remove gangue, so as to reduce an energy loss in the lignite drying process. After the deashing process 5 and the partial gangue removal, the lignite enters microwave 10, vibrating mixed-flow 11 or fluidized-bed equipment 8 to dry 9.

(10) The disclosure is described in further detail below with reference to the accompanying drawings.

Example 1: As Shown in FIG. 2

(11) Step A: The final ash content and moisture content of lignite were determined by using two evaluation indicators, namely calorific value and production cost. Considering the high moisture content of lignite, the production process was determined as first preliminary gangue removal and then drying.

(12) Step B: The lignite was fed to an elastic grading screen 102 through a chute by a belt conveyor for deep dry grading. The mesh size of the elastic screen was 30 mm. The oversize lignite larger than 30 mm entered a crusher 104. The coal discharged after crushing and the undersize coal 103 smaller than 30 mm filtered by the elastic grading screen entered X-ray dry sorting equipment 105, composite dry sorting equipment 106 or fluidized-bed equipment for initial gangue removal. In this way, part of the gangue was removed, so as to meet the ash reduction requirement.

(13) Step C: The undersize lignite smaller than 30 mm filtered by the elastic grading screen and the lignite crushed by the crusher selectively entered vibrating mixed-flow, microwave and fluidized-bed equipment for micro drying treatment. The surface moisture of the coal was removed, and the drying was stopped when an expected drying purpose was achieved.

(14) Step D: After the micro ash reduction treatment, the lignite entered the microwave 109, vibrating mixed-flow 108 or fluidized-bed equipment for drying, and after a certain period of drying treatment, a desired product was obtained.