US-12617718-B2 - Energy-efficient, carbon-enriched cement production system and a method of producing cement clinker

US12617718B2US 12617718 B2US12617718 B2US 12617718B2US-12617718-B2

Abstract

The present disclosure provides an energy-efficient (low energy consumption), carbon enriched cement production system and a method for producing cement clinker. This system involves raw material preheating and precalcining system and sequentially connected kiln inlet chamber, rotary kiln and cooler, wherein the raw material preheating and precalcining system involves precalciner and preheater, and the cooler involves first cooling zone and second cooling zone. The first cooling zone includes first cooling partition and second cooling partition, wherein a mixture of pure oxygen and high-concentration CO 2 flue gas entering the inlet of the first cooling partition, high-concentration CO 2 flue gas entering the inlet of the second cooling partition, and air entering the inlet of the second cooling zone have solved the problems in existing cement kiln CO 2 enrichment technology, i.e., extensive air leakage and high energy consumption between the first cooling zone and the second cooling zone.

Inventors

Xiaolong He
Xueping Peng
Changhua Chen
Zhongyuan DAI

Assignees

TIANJIN CEMENT INDUSTRY DESIGN & RESEARCH INSTITUTE CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20201216

Claims (15)

1 . An energy-efficient, carbon-enriched cement production system comprising: a raw meal preheating and precalcining system, a kiln inlet chamber, a rotary kiln comprising a first burner; a cooler; the kiln inlet chamber, the rotary kiln and the cooler being connected in sequence; the raw material preheating and precalcining system including a precalciner and a preheater, wherein the precalciner is equipped with a second burner and a raw material inlet; a lowermost air inlet of the preheater being connected to an outlet duct of the precalciner, and an uppermost air outlet of the preheater being configured to emit a low temperature flue gas; an uppermost feed port of the preheater being configured for feeding raw materials, and a lowermost discharge port thereof being connected to the kiln inlet chamber; the cooler including a first cooling zone and a second cooling zone, wherein the first cooling zone is set with a partition wall in the middle, dividing it into a first cooling partition and a second cooling partition, and the second cooling partition being arranged between the first cooling partition and the second cooling zone, an inlet of the first cooling partition being configured to feed a mixture of pure oxygen and high-concentration CO 2 flue gas, an inlet of the second cooling partition being configured to fill high-concentration CO 2 flue gas, and an inlet of the second cooling zone being configured to fill air, an outlet of the second cooling partition being connected to the lowermost air inlet of the preheater through a first pipe, the uppermost air outlet of the preheater being connected via a second pipe to a first fan, from an air outlet of the first fan the low temperature flue gas being split into a first portion and a second portion: the first portion entering a carbon capture system through a third pipe, and the second portion entering a fourth pipe where a second fan is set, the low temperature flue gas being divided into a third portion and a fourth portion by an outlet of the fourth pipe: the third portion entering a fifth pipe to mix with pure oxygen and get into the first cooling partition via the inlet of the first cooling partition, while the fourth portion entering the inlet of the second cooling partition via a sixth pipe, and wherein the circulating flue gas has a CO 2 concentration of 70-95%.
2 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the cooler is a grate cooler provided with a roll mill in the middle, dividing it into the first cooling zone and the second cooling zone.
3 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the mixture of pure oxygen and high-concentration CO 2 flue gas of the first cooling partition is divided into a first portion and a second portion: wherein the first portion directly enters the rotary kiln as secondary air for fuel combustion, and the second portion enters the precalciner via a tertiary air duct as tertiary air for fuel combustion.
4 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the second pipe is furnished with a heat exchanger.
5 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the fourth pipe is arranged with a dust collector at a position close to an air inlet of the second fan.
6 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the fourth pipe is equipped with a first valve.
7 . An energy-efficient, carbon-enriched cement production system according to claim 1 , characterized in that the fifth pipe is equipped with a second valve.
8 . A method of producing carbon enriched cement comprising: feeding raw materials into a preheater where the raw materials are separated from a flue gas by heat exchange to obtain preheated raw materials; providing the preheated raw materials to a precalciner in which a burning fuel releases a large amount of heat to break down the preheated raw materials, forming hot raw materials; providing the hot raw materials passing from a kiln inlet chamber into a rotary kiln where they are calcined into a cement clinker, which enters a cooler from a rotary kiln outlet; initially cooling the cement clinker with a mixture of pure oxygen and high-concentration CO 2 flue gas poured into a first cooling partition to obtain a first cooled gas and a first cooled cement clinker; dropping the first cooled cement clinker into a second cooling partition and cooling it with a high-concentration carbon dioxide gas to obtain a second cooled gas and a second cooled cement clinker; allowing the second cooled cement clinker to enter a second cooling zone and cooling it with air in the second cooling zone to obtain a finished cement clinker as well as a third cooled gas; wherein a kiln gas entering the precalciner meets a flue gas produced by fuel combustion and raw material decomposition to form a mixed flue gas product, which enters the preheater via an outlet duct of the precalciner and is separated from the raw materials in the preheater by heat exchange to become a low-temperature flue gas to be discharged from the a top air outlet of the preheater, the CO 2 concentration in the low-temperature flue gas being 70-95%.
9 . A method of producing carbon enriched cement according to claim 8 further comprising: providing the low-temperature flue gas to a first fan, the low-temperature flue gas from an air outlet of the first fan being divided into a first portion and a second portion, the first portion entering a carbon capture system and the second portion becoming a circulating flue gas after passing a second fan and entering an enters an inlet of the first cooling partition after mixing with pure oxygen.
10 . A method of producing carbon enriched cement according to claim 9 , characterized in that the flue gas enters a heat exchanger for heat exchange and utilization before entering the first fan.
11 . A method of producing carbon enriched cement according to claim 9 , characterized in that the second portion of flue gas enters a dust collector for dust removal before entering the second fan.
12 . A method of producing carbon enriched cement according to claim 8 , characterized in that the first cooled gas is divided into a first portion and a second portion, the first portion entering the rotary kiln as secondary air for fuel combustion, and the kiln gas entering the precalciner; the second portion entering the precalciner as a tertiary air for fuel combustion.
13 . A method of producing carbon enriched cement according to claim 8 , characterized in that the second cooled gas enters an air inlet of the preheater.
14 . A method of producing carbon enriched cement according to claim 8 further comprising: providing the low-temperature flue gas enters to a first fan, from an air outlet of which the low-temperature flue gas is divided into a first portion and a second portion: the first portion entering a carbon capture system and the second portion passing a second fan and entering an inlet of the second cooling partition.
15 . A method of producing carbon enriched cement according to claim 8 further comprising, providing the low-temperature flue gas to a first fan, the flue gas from an air outlet of the first fan being divided into a first portion and a second portion, the first portion entering a carbon capture system and the second portion being further split into a third portion and a fourth portion when passing a second fan: the third portion meeting pure oxygen to become a mixed gas entering an inlet of the first cooling partition, while the second portion enters an inlet of the second cooling partition.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national application of International Application No. PCT/CN2020/136713 filed on Dec. 16, 2020, the disclosure of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present disclosure relates to the field of cement process technology, in particular to a carbon-enriched cement production system with low energy consumption and a method of producing cement clinker. BACKGROUND As global climate heats up, carbon dioxide emissions have received widespread attention. Oodles of carbon dioxide are produced during cement production. According to statistics, the production of 1-ton cement emits 0.6 to 0.7 ton carbon dioxides. Carbon dioxide in cement kiln exhaust gas mainly comes from two sources: 1. Carbon dioxide generated by fuel combustion, accounting for about 40%.2. Carbon dioxide generated from the decomposition of carbonate in raw materials, accounting for about 60%. The Cement Technology Roadmap 2050 developed by the International Energy Agency (IEA) in cooperation with the Cement Sustainability Initiative (CSI) states that carbon capturing and sequestering technology is currently the most viable new technology for reducing CO2 emissions in the cement industry, and expected to cut down 56% CO2 emissions by 2050. At present, the technology of capturing all carbon dioxides in cement kiln waste gas is yet in the R&D stage when the enrichment of carbon dioxides in waste gas is the key point. One CO2 enrichment means used in current cement kilns is as follows: the original cooler is divided into first cooling zone and second cooling zone; the first cooling zone is injected with O2/CO2 mixture for heat exchange with clinker, and the heat-exchanged flue gas enters the rotary kiln and precalciner; the second cooling zone is injected with conventional air for heat exchange with clinker, and the heat-exchanged air is used for waste heat utilization or emission; For one thing, the cement kiln is automatically enriched with CO2, which greatly facilitates the subsequent operation of CO2 capture and purification. And for another, the temperature of cooled cement clinker meets the follow-up production requirements, and the cooling effect of the cement clinker is not affected. The above CO2 enrichment technology for cement kiln has the following problems: 1. The O2/CO2 mixture in the first cooling zone and the air in the second cooling zone can easily be blended to reduce the concentration of CO2 in the flue gas, affecting subsequent CO2 capture while increasing the consumption of pure oxygen. All this will increase the production cost.2. The heat recovery of high temperature air out of the cooler is not sufficient. After oxyfuel combustion, the combustion air volume required for rotary kiln and decomposer is lowered, making it difficult to fully recover the heat of high temperature air exiting the first cooling zone to the calcining system, thus causing high energy consumption during cement production. SUMMARY To overcome the defects of the prior art, the present disclosure provides an energy-efficient, carbon-enriched cement production system and a method of producing cement clinker that can solve the problems in existing cement kiln's CO2 enrichment technology, namely the O2/CO2 mixture in the first cooling zone and the air in the second cooling zone are prone to blending, consequently lowering the CO2 concentration in the flue gas and therefore affecting subsequent CO2 capture. This will increase the consumption of pure oxygen and cause an increase in the production cost as well as inadequate heat recovery of high temperature air out of the cooler and high energy consumption in cement production. The present disclosure is realized by the following technical solutions: An energy-efficient, carbon-enriched cement production system of the present disclosure, comprising raw meal preheating and precalcining system, kiln inlet chamber, rotary kiln and cooler, wherein the rotary kiln is provided with first burner;The kiln inlet chamber, rotary kiln and cooler are connected in sequence;The raw material preheating and precalcining system includes precalciner and preheater, wherein the precalciner is equipped with second burner and raw material inlet;The bottom air inlet of the preheater is connected to the outlet duct of the precalciner, and the top air outlet of the preheater emits low temperature flue gas; the top feed port of the preheater is used for feeding raw materials, and the bottom discharge port thereof is connected to the kiln inlet chamber;The cooler includes the first and second cooling zones. The first cooling zone comprises the first and second cooling partitions, and the second cooling partition is arranged between the first cooling partition and the second cooling zone. The inlet of the first cooling partition is used to feed a mixture of pure oxygen and high-concentration CO2 flue gas, the inlet of the second cooling parti