CN216497480U

CN216497480U - Organic matter heat recovery device for aluminum oxide production

Info

Publication number: CN216497480U
Application number: CN202122674682.2U
Authority: CN
Inventors: 付军; 张辉; 陈星宇; 田卫国; 侯宝; 王丹阳; 杨园园; 刘望锡; 张孔越; 张婧霞; 薛艳军; 姚帅
Original assignee: Chalco Zhongzhou Aluminium Industry Co ltd; Aluminum Corp of China Ltd
Current assignee: Chalco Zhongzhou Aluminium Industry Co ltd; Aluminum Corp of China Ltd
Priority date: 2021-11-03
Filing date: 2021-11-03
Publication date: 2022-05-13
Anticipated expiration: 2031-11-03

Abstract

An organic matter heat recovery device for alumina production, comprising: the system comprises a first settling tank, a bottom flow pump, an evaporator, a circulating pump, a negative pressure air chamber, a first conveying pump and a second settling tank; a discharge port arranged on the first settling tank is connected with a feed end of the underflow pump; the evaporator comprises an evaporation chamber and an air chamber, an inlet arranged on the side wall of one side of the evaporation chamber is connected with the upper end of the air chamber, the lower end of the air chamber is connected with the discharge end of the circulating pump, the lower end of a discharge pipe arranged at the bottom of the evaporation chamber is connected with the feed end of the circulating pump, and the pipe wall of the discharge pipe arranged in the evaporation chamber is connected with the discharge end of the underflow pump; the negative pressure air chamber is connected with an air outlet formed in the top of the evaporation chamber, and the second settling tank is connected with a discharge hole formed in the side wall of the other side of the evaporation chamber through a first conveying pump. The device can forcibly cool the organic matters from more than 100 ℃ to about 85 ℃ through the evaporator with the circulating pump, and the recovered heat is converted into 0.6MPa saturated steam (enthalpy value 2756kJ/kg) which is about 2.05 t/h.

Description

Organic matter heat recovery device for aluminum oxide production

Technical Field

The utility model belongs to the field of alumina production, and particularly relates to an organic matter heat recovery device for alumina production.

Background

The evaporation process in the production of alumina is a key process of energy consumption, and the steam consumption of the evaporation process accounts for about 35 percent of the production of alumina. The heat loss of the low-pressure steam reaches 5 t/h. Along with the operation of the low-temperature Bayer process, the content of imported ore organic matters is high, the system solution TOC, oxalate and the like gradually rises, the phenomena of obvious changes of pulp, red mud fluidity, semen property and the like gradually appear, and the stable operation of the production flow is adversely affected and mainly reflected in that: in the decomposition process, the nucleation frequency of decomposition is accelerated, agglomeration of aluminum hydroxide is disturbed, the quality of the finished aluminum oxide product is influenced, scabbing of equipment such as a decomposition tank (a settling tank), a seed tank and a cooling tank is accelerated, and the solution viscosity is increased due to accumulation of organic matters, so that the decomposition rate is reduced. The property of slurry in the decomposing tank is changed to generate abundant foam, and when the condition is serious, the foam is 1.5-2.0m above the decomposing tank, so that the productivity of a seed filter is reduced, and the output and the liquid quantity balance of a system are seriously influenced besides that the efficiency of intermediate heat exchange equipment is low (the foam is generally a liquid, solid and gas three-phase mixture, and pump cavitation is caused after gas enters a pump cavity to influence the output); oxalate precipitation can be caused due to the fact that conditions such as temperature and the like are not controlled in place in the decomposition process, and oxalate enters a roasting system along with aluminum hydroxide, so that products are greatly damaged before and after roasting, and difficulty is brought to quality control of aluminum oxide products; part of the decomposed mother liquor and AH washing liquor enter an evaporation system along with the decomposed mother liquor and sodium carbonate are co-separated out in the forced effective salt discharge process, so that the fluctuation of the granularity of the separated salt is large, and the stable operation and the salt discharge effect of the salt discharge filter are influenced.

In Bayer process production, process organic matters mainly come from bauxite and high molecular agents (including flocculating agents, dehydrating agents, crystallization aids, defoaming agents, beneficiation agents and the like), and as the organic matters are gradually accumulated in a circulating system, more adverse effects are brought to subsequent production.

The prior problems in production include that the temperature of discharged salt and conveyed floating materials is about 103 ℃, the temperature is higher, the precipitated carbon and alkali are less, and the organic matter is less. The high temperature can also cause the filter plate of the plate and frame filter press to deform and easily spread, the high temperature causes the filter plate of the plate and frame filter press to deform and bur in the operation, the operation safety of workers cannot be ensured, and the high temperature affects the discharge of carbon alkali and organic matters.

In the evaporation process, the carbon-base ratio of the production system is kept below 12% at present, the average carbon-base ratio of the semen system in the first half of 2020 is 11.5%, the forced effect only needs to be opened normally for 2 groups according to the steam load production organization, and the other 3 groups are forced to be not opened, so 8 groups of forced effects are in a stop operation state. 8 groups are two-stage feeding and discharging processes, and the original flash system needs to be supplemented by additional heat sources to improve the concentration because the temperature of the original liquid is low, generally about 70-75 ℃.

Disclosure of Invention

Aiming at the defects of the prior art, the utility model provides an organic matter heat recovery device for alumina production.

The utility model is realized by the following technical scheme.

An organic matter heat recovery device for alumina production, characterized in that the device comprises: the system comprises a first settling tank, a bottom flow pump, an evaporator, a circulating pump, a negative pressure air chamber, a first conveying pump and a second settling tank; the discharge port arranged on the first settling tank is connected with the feed end of the underflow pump; the evaporator comprises an evaporation chamber and an air chamber, wherein an inlet arranged on the side wall of one side of the evaporation chamber is connected with the upper end of the air chamber, the lower end of the air chamber is connected with the discharge end of the circulating pump, the lower end of a discharge pipe arranged at the bottom of the evaporation chamber is connected with the feed end of the circulating pump, and the pipe wall of the discharge pipe arranged in the evaporation chamber is connected with the discharge end of the underflow pump; the negative pressure air chamber is connected with an air outlet formed in the top of the evaporation chamber, and the second settling tank is connected with a discharge hole formed in the side wall of the other side of the evaporation chamber through a first conveying pump.

Further, the feed inlet that the second settling tank top was equipped with is connected with the discharge end of first delivery pump, the discharge gate that the second settling tank bottom was equipped with passes through the second delivery pump and is connected with the filter press.

The beneficial technical effects of the utility model are that,

(1) the evaporator with a circulating pump can be used for increasing the evaporation capacity of organic matters such as sodium aluminate solution (salt discharge underflow), thereby rapidly reducing the temperature; (2) the heat of organic matters such as sodium aluminate solution (salt discharge underflow) is recovered by applying the temperature and the pressure difference, and the temperature of the salt discharge underflow is more than or equal to 100 ℃. The temperature of the negative pressure air chamber is about 70 ℃, the temperature of the evaporator evaporation chamber is about 62 ℃, and the final effect is negative pressure evaporation, so that the heat of the discharged salt bottom flow can be fully absorbed. (3) The device can forcibly cool organic matters such as sodium aluminate solution (salt discharge underflow) from more than 100 ℃ to about 85 ℃ through the evaporator with the circulating pump, and the recovery heat is converted into 0.6MPa saturated steam (enthalpy 2756kJ/kg) which is about 2.05 t/h.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, an organic matter heat recovery apparatus for alumina production includes: the system comprises a first settling tank 1, an underflow pump 2, an evaporator 3, a circulating pump 4, a negative pressure air chamber 5, a first conveying pump 6 and a second settling tank 7;

a discharge port arranged on the first settling tank 1 is connected with a feed end of the underflow pump 2;

the evaporator 3 comprises an evaporation chamber 8 and an air chamber 9, an inlet arranged on one side wall of the evaporation chamber 8 is connected with the upper end of the air chamber 9, the lower end of the air chamber 9 is connected with the discharge end of the circulating pump 4, the lower end of a discharge pipe arranged at the bottom of the evaporation chamber 8 is connected with the feed end of the circulating pump 4, the pipe wall of the discharge pipe arranged in the evaporation chamber 8 is connected with the discharge end of the underflow pump 2, and the sodium aluminate solution circularly and upwards enters the evaporation chamber 8 through the circulating pump 4 and the air chamber 9, so that the heat dissipation is fast and large; the negative pressure air chamber 5 is connected with the air outlet arranged at the top of the evaporation chamber 8, the second settling tank 7 is connected with the discharge port arranged on the side wall of the other side of the evaporation chamber 8 through the first conveying pump 6, and the discharge port arranged at the bottom of the second settling tank 7 is connected with the plate-and-frame filter press through the second conveying pump 10.

The first settling tank 1 and the second settling tank 7 both comprise cylindrical tank bodies and conical tank bodies connected with the lower ends of the cylindrical tank bodies.

The method for recovering the heat of the organic matters comprises the following steps:

(1) the method comprises the steps of introducing organic matters such as sodium aluminate solution (salt discharge underflow) in a first settling tank 1 into an evaporator 3 of an evaporator unit in the Bayer process production process, wherein the evaporator 3 is connected with a circulating pump 4, the circulating pump 4 is started, the exhaust steam flow of the evaporator is led to a negative pressure air chamber 5, the temperature of the negative pressure air chamber 5 is controlled to be about 70 ℃, the temperature of an evaporator evaporation chamber 8 of the evaporator is about 62 ℃, the last effect is negative pressure evaporation, the pressure of the negative pressure air chamber 5 is-0.06 MPa, and the pressure of the evaporation chamber is-0.07 MPa, so that the heat of the sodium aluminate solution (salt discharge underflow) can be fully absorbed, the sodium aluminate solution (salt discharge underflow) is cooled and evaporated, the cooling process of the sodium aluminate solution (salt discharge underflow) is realized, the recovered heat is used for the negative pressure air chamber 5, and a heat supply source can be provided for the lack of the primary flash heat of the evaporator unit.

(2) And (2) placing the cooled sodium aluminate solution (the salt-removing underflow) into a second settling tank 7 to naturally separate out for 1-2 h, wherein organic matters (containing oxalate) and carbonate can be separated out in the process of cooling to 80 ℃ at 100 ℃, then naturally separating out for 1-2 h in the second settling tank, and conveying the solution to a plate-and-frame filter press through a second conveying pump 10 to perform filter pressing to complete a solid-liquid separation process, so as to obtain a filtrate and a filter cake, wherein the filtrate is the solution with low organic matter content, can return to the Bayer process production flow to continuously produce alumina, and the filter cake is the substance with high organic matter content, can be sent to the sintering process alumina production flow as an ingredient to produce alumina, and cannot influence the alumina production. After the organic matters are removed through temperature reduction and retention, the removal rate of the organic matters in the discharged salt bottom flow is improved by 5 to 8 percent, and the removal rate of the oxalate can be improved by 16 to 24 percent.

Example 1

The sodium aluminate solution (the salt discharge underflow) in the first settling tank 1 is introduced into an evaporator 3 which is connected with a circulating pump 4 in the Bayer process production process, the circulating pump 4 is started, the temperature of the sodium aluminate solution (the salt discharge underflow) is generally above 100 ℃, a valve for forcing exhaust steam to a negative pressure air chamber 5 is started, an evaporator unit adopts a 6-effect 4-stage flash evaporation countercurrent evaporation process, the temperature of the negative pressure air chamber 5 is controlled to be about 70 ℃, the temperature of an evaporator evaporation chamber 8 is controlled to be about 62 ℃, and the final effect is negative pressure evaporation, the pressure of a negative pressure air chamber is 5-0.06 Mpa, the pressure of an evaporation chamber is 8-0.07 Mpa, the heat of the sodium aluminate solution (the bottom flow of the salt discharge) can be fully absorbed, the temperature reduction and evaporation are carried out on the sodium aluminate solution (the salt discharge underflow), so that the temperature reduction process of the sodium aluminate solution (the salt discharge underflow) is realized, the recovered heat is used for the negative pressure air chamber 5 of the 6-effect evaporator, and a heat source can be provided for the lack of the original flash heat of the evaporator unit.

The temperature of the sodium aluminate solution (the bottom flow of the discharged salt) is 104.6 ℃ and the forced effect is carried out in the unit, and the flow rate is 100m³H, concentration Nk greater than 300g/l, specific gravity 1.42kg/m³. After cooling, the temperature was 89.9 ℃. Calculating the recovered heat quantity, which is converted into 0.6MPa saturated steam quantity (t/h). The unit is forced to operate according to 80 percentAnd (5) calculating the rate. Saturated steam (enthalpy 2756kJ/kg) at 0.6MPa, the specific heat of the sodium aluminate solution changes with the change of concentration and alpha k, the specific heat is generally between 2.7 and 3.7kJ/kg. ℃, the specific heat is 3kJ/kg. ℃, and the recoverable heat 41691222720kJ/a is released after temperature reduction.

And (3) placing the cooled sodium aluminate solution (the salt discharge underflow) into a second settling tank 7 for natural precipitation for 2 hours, precipitating organic matters (containing oxalate) and carbonate in the process, conveying the naturally precipitated sodium aluminate solution for 2 hours to a plate-and-frame filter press through a second conveying pump 10, and performing filter pressing to complete a solid-liquid separation process to obtain filtrate with low organic matter content and filter cakes with high organic matter content, returning the filtrate with low organic matter content to the Bayer process production process, and sending the filter cakes with high organic matter content to the sintering process alumina production process to serve as raw materials of ingredients. After the temperature is reduced and the organic matters are removed, the removal rate of the organic matters in the sodium aluminate solution (the salt discharge underflow) reaches 8 percent, and the removal rate of the oxalate reaches 24 percent.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model. It should be noted that other equivalent modifications can be made by those skilled in the art in light of the teachings of the present invention, and all such modifications can be made as are within the scope of the present invention.

Claims

1. An organic matter heat recovery device for alumina production, characterized in that the device comprises: the device comprises a first settling tank (1), an underflow pump (2), an evaporator (3), a circulating pump (4), a negative pressure air chamber (5), a first conveying pump (6) and a second settling tank (7); a discharge port arranged in the first settling tank (1) is connected with a feed end of the underflow pump (2); the evaporator (3) comprises an evaporation chamber (8) and an air chamber (9), an inlet arranged on one side wall of the evaporation chamber (8) is connected with the upper end of the air chamber (9), the lower end of the air chamber (9) is connected with the discharge end of the circulating pump (4), the lower end of a discharge pipe arranged at the bottom of the evaporation chamber (8) is connected with the feed end of the circulating pump (4), and the pipe wall of the discharge pipe arranged in the evaporation chamber (8) is connected with the discharge end of the underflow pump (2); the negative pressure air chamber (5) is connected with an air outlet formed in the top of the evaporation chamber (8), and the second settling tank (7) is connected with a discharge hole formed in the side wall of the other side of the evaporation chamber (8) through a first conveying pump (6).

2. The organic matter heat recovery device for alumina production according to claim 1, wherein the feed inlet arranged at the top of the second settling tank (7) is connected with the discharge end of the first conveying pump (6), and the discharge outlet arranged at the bottom of the second settling tank (7) is connected with the plate-and-frame filter press through the second conveying pump (10).