A high-efficiency solid-liquid separation method for metatitanic acid slurry

Abstract

The present invention discloses an efficient solid-liquid separation method for metatitanic acid slurry, which sequentially adopts a solid-liquid separation method of low-pressure feed filter pressing, medium-pressure top feeding, and high-pressure pressing, and collects most of the impurity components of ferrous sulfate and sulfuric acid in the hydrolyzed metatitanic acid slurry in the titanium dioxide waste acid generated by the upper filtration, so that only ferrous sulfate and sulfuric acid components accounting for 5% to 10% of the system enter the first washing acid waste water, so that most of the impurity components of ferrous sulfate and sulfuric acid that need to be separated from the hydrolysis slurry are concentrated into the titanium dioxide waste acid; and the generation of the first washing acid waste water can be greatly reduced, and the first washing acid waste water is all discharged into the sewage station for neutralization treatment, or part of the first washing acid waste water is directly reused in the ilmenite acid hydrolysis section as a leaching liquid, and the remaining part is discharged into the sewage station for neutralization treatment. The present invention is economical and environmentally friendly, and the titanium gypsum slag generated is basically negligible.

Description

Technical Field

[0001] The invention relates to a solid-liquid separation method of metatitanic acid slurry. Background Art

[0002] More than 85% of domestic titanium dioxide companies adopt the sulfuric acid production process, in which the hydrolyzed titanic acid slurry will go through upper sheet filtration → first washing → bleaching → second washing, and then enter the subsequent process.

[0003] The filtrate produced by the upper filtration will be hydrolyzed and recovered by metatitanic acid to obtain the commonly known titanium dioxide waste acid, whose main components are H2SO4 content of 20%-25% and FeSO4 content of 10%-15%. There are two methods for the disposal of this type of waste acid. The first method is to use multi-effect waste acid concentration technology for direct concentration treatment, and finally produce 50-92% of finished acid and ferrous iron (ferrous sulfate monohydrate with high impurity content). The finished acid is generally returned to the acid hydrolysis process for reuse, while the ferrous iron is partially mixed with pyrite to burn sulfuric acid, or partially or even completely pulped and neutralized to produce red gypsum slag; the second method is to directly use alkali neutralization to produce red gypsum slag.

[0004] The acidic wastewater produced in the first washing is recovered and disposed of by hydrolysis of titanic acid, and then discharged into the environmental protection workshop for neutralization treatment, which will produce a large amount of titanium gypsum slag.

[0005] The cleaning water produced by the second wash is recycled and used as the cleaning water for the first wash.

[0006] At present, the disposal of titanium gypsum slag is mainly through storage and landfill, but it occupies a large space. With the continuous shrinkage of the land available for titanium dioxide production enterprises, especially enterprises in coastal areas are facing strong environmental pressure to reduce slag. Therefore, the demand for slag reduction by titanium dioxide enterprises has also shown a "rising tide lifts all boats".

[0007] Titanium gypsum slag mainly comes from the neutralization treatment of titanium dioxide waste acid and the first-wash acidic wastewater. At present, the treatment of titanium dioxide waste acid is mainly concentrated and the acid is recovered. Some companies mix the ferrous yellow with sulfuric acid or send it out to produce polyferric. If it cannot be completely consumed, it will eventually be pulped and neutralized to produce titanium gypsum slag. For the acidic wastewater produced by the first washing, although a few companies have used membrane separation technology to recover some pure acidic water, the ferrous sulfate in the membrane concentrate and the untreated acidic wastewater are eventually neutralized and treated. It is the main source of titanium gypsum slag produced by titanium dioxide production enterprises and a disposal object that needs to be paid special attention to. It has been a trouble for enterprises for a long time.

[0008] According to statistics from sulfuric acid titanium dioxide manufacturers, for every ton of titanium dioxide produced, 1.8-1.9 tons of 100% acid will enter titanium dioxide waste acid and primary washing acid wastewater respectively, of which sulfuric acid and ferrous sulfate account for about 50%:50% of the distribution of the two. Therefore, how to reasonably dispose of titanium dioxide waste acid while solving the problem of primary washing acid wastewater disposal is a difficult challenge facing sulfuric acid titanium dioxide manufacturers and environmental protection workers. Summary of the invention

[0009] The object of the present invention is to provide an efficient solid-liquid separation method of metatitanic acid slurry which is economical, environmentally friendly and produces substantially negligible titanium gypsum slag.

[0010] The technical solution of the present invention is:

[0011] A high-efficiency solid-liquid separation method for metatitanic acid slurry is characterized by: a solid-liquid separation method of sequentially adopting low-pressure feed filtration, medium-pressure top feeding, and high-pressure pressing to collect most of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed metatitanic acid slurry in the titanium dioxide waste acid generated by the upper filtration, so that only ferrous sulfate and sulfuric acid components accounting for 5% to 10% of the system enter the first-wash acid waste water, so that most of the ferrous sulfate and sulfuric acid impurity components that need to be separated from the hydrolyzed slurry are concentrated into the titanium dioxide waste acid; and the generation of the first-wash acid waste water can be greatly reduced, and the first-wash acid waste water is all discharged into a sewage station for neutralization treatment, or part of the first-wash acid waste water is directly reused in the ilmenite acid hydrolysis section as a leaching liquid, and the remaining part is discharged into the sewage station for neutralization treatment.

[0012] The method of collecting most of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed metatitanic acid slurry into the titanium dioxide waste acid produced by the upper filtration means collecting more than 90% to 95% of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed metatitanic acid slurry into the titanium dioxide waste acid produced by the upper filtration.

[0013] The specific steps are:

[0014] Step 1: The hydrolyzed metatitanic acid slurry after cooling treatment is pumped to the high-pressure solid-liquid separation device through the low-pressure feed pressure pump P01, and the pumping pressure control value is set to p1. When the pressure after the pump P01 reaches the p1 value, the P01 pump is stopped to obtain the filter cake, the valve is switched, and the top water pump P02 is started. The pump outlet pressure is p2, and the process water or the higher concentration acid washing water collected in the front stage of the first washing is delivered to replace the residual concentrated acid liquid in the top filter cake. The running cumulative flow rate of the top water pump P02 is set to Q. When the cumulative flow rate reaches the set value, the top water pump P02 is stopped, and the high-pressure water squeezing pump P03 is started. The pumping pressure control value is set to p3, and the upper filter cake is further squeezed to squeeze out the residual sulfuric acid and ferrous sulfate components as much as possible; the filtrate produced by the above filter pressing is collected together and all used as titanium dioxide waste acid;

[0015] Step 2: Discharge the filter cake obtained after the filter press in step 1, use the secondary washing acid wastewater to pulp the filter cake, filter it on the upper sheet, introduce the filtrate into the metatitanic acid recovery device, and then discharge the clear liquid into the sewage workshop;

[0016] Step 3: The filter cake obtained after the upper filtration in step 2 enters the first wash, and the recycled second wash wastewater is used as the first wash cleaning water. The acidic wastewater generated by the first wash filtration is directly discharged or collected separately in two stages; if two-stage separate collection is adopted, the valve switching time is set to t2. During the period of 0 to t2, the acidic wastewater with higher concentration is collected in the water supply tank of the top water pump P02 for top material use. When the time reaches t2, the valve is switched to transport the remaining low-concentration acidic wastewater to the corresponding collection pool for reuse as ilmenite acid hydrolysis leaching liquid, or directly discharged to the sewage treatment station for neutralization and disposal.

[0017] The solid-liquid separation device described in step 1 includes but is not limited to a high-pressure separation device of a plate and frame diaphragm filter press.

[0018] In the step 1, the value of p1 is 0.2-0.4Mpa, the value of p2 is 0.4-1.0Mpa, and the value of p3 is 1.2-10.0Mpa; the value of Q is 1.5-3.0 times the mass of the slurry titanic acid entering the solid-liquid separation device in batches; the value of t2 in the step 2 is 5-10min.

[0019] The high-efficiency solid-liquid separation method can realize the collection of impurity components in the metatitanic acid slurry of sulfuric acid process titanium dioxide production in high-concentration titanium dioxide waste acid. The specific advantages are mainly reflected in the following aspects:

[0020] 1) Get rid of the traditional idea of ​​washing titanic acid, remove the impurity components such as sulfuric acid and ferrous sulfate in the hydrolyzed titanic acid during the upper filtration and first washing process and redistribute them, that is, the proportion of the components in the titanium dioxide waste acid and the first washing acidic wastewater is changed from the traditional about 50%:50% to (90%~95%):(5%~10%), so as to achieve the purpose of centralized collection.

[0021] 2) The amount of water and impurity content of the first-wash acid wastewater are greatly reduced. If neutralization treatment is used, the amount of slag produced can be greatly reduced, and the titanium gypsum slag produced can be basically ignored. It can even be achieved that almost all of the first-wash acid wastewater can be reused in the acid hydrolysis process as leaching liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] Figure 1 It is the overall process flow chart of the present invention.

[0024] Figure 2It is a schematic diagram of the filter pressing process. DETAILED DESCRIPTION

[0025] Embodiment 1:

[0026] Hydrolyze the titanic acid slurry H2TiO3 218g / L, H2SO4 22%, FeSO4 200g / L, start the plate and frame filter press screw pump P01 to transport the slurry to 200m 2 Plate and frame diaphragm filter press, the pressure gauge value p1 of the filter press feed pipe gradually rises, the filtrate is sent to the waste acid collection tank T01, and after running for 1.5 hours, the pressure gauge shows 4 bar, the pump P01 is stopped, the feed valve XV-1 is closed, the top feed valve XV-2 is switched, the top feed pump P02 is started, and the top filtrate enters the waste acid collection tank T01. When the cumulative flow rate at the pump P02 outlet reaches 5.2m 3 When the pressure rises to 30 bar, stop feeding, close the top valve XV-2, switch to the squeeze water inlet valve XV-3, start the squeeze water pump P03, squeeze the filtrate into the waste acid collection tank T01, wait for the pressure p3 to rise to 30 bar, stop the pump P03, maintain the pressure for 30 minutes, open the squeeze reflux valve XV-4, drain the squeeze water back to the squeeze water tank T01. The concentrated titanium dioxide waste acid H2TiO3 0.11%, H2SO4 22.25%, FeSO411.90%. The filter cake is unloaded, the second washing acid waste water is used for pulping, the leaf filter is vacuum filtered on the upper sheet, the filtrate enters the metatitanic acid recovery and treatment device, the upper filter cake is hoisted into the first washing tank, the collection valve is opened, the discharge valve is closed, and the vacuum filtration is started. The filtrate is collected to the top material tank. When the time is up to 5 minutes, switch to open the discharge valve first, then close the collection valve, the filtrate is treated in the metatitanic acid recovery device and then goes to the collection tank and reused in the acid hydrolysis process.

[0027] Embodiment 2:

[0028] Hydrolyze the titanic acid slurry H2TiO3 205g / L, H2SO4 25%, FeSO4 220g / L, start the plate and frame filter press screw pump P01 to transport the slurry to 250m 2 Plate and frame diaphragm filter press, the pressure gauge value p1 of the filter press feed pipe gradually rises, the filtrate is sent to the waste acid collection tank T01, and after running for 2.0 hours, the pressure gauge shows 6 bar, pump P01 is stopped, feed valve XV-1 is closed, switch to top feed valve XV-2, start top feed pump P02, and the top filtrate enters the waste acid collection tank T01. When the cumulative flow rate at the pump P02 outlet reaches 6.1m 3When the pressure rises to 40 bar, stop feeding, close the top valve XV-2, switch to the squeeze water inlet valve XV-3, start the squeeze water pump P03, squeeze the filtrate into the waste acid collection tank T01, wait for the pressure p3 to rise to 40 bar, stop the pump P03, maintain the pressure for 20 minutes, open the squeeze reflux valve XV-4, drain the squeeze water back to the squeeze water tank T01. The concentrated titanium dioxide waste acid H2TiO3 0.10%, H2SO4 23.12%, FeSO411.97%. The filter cake is unloaded, the second wash acid wastewater is used for pulping, the leaf filter is vacuum filtered on the upper sheet, the filtrate enters the titanic acid recovery treatment device, the upper filter cake is hoisted into the first washing tank, and the first wash filtrate is treated by the titanic acid recovery device and then discharged to the sewage treatment workshop.

Claims

1. An efficient solid-liquid separation method for metatitanic acid slurry, characterized in that: A solid-liquid separation method of low-pressure feed filtration, medium-pressure top feeding, and high-pressure pressing is sequentially adopted to collect most of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed metatitanic acid slurry into the titanium dioxide waste acid produced by the upper filtration, so that the ferrous sulfate and sulfuric acid components enter the first washing acid waste water, so that most of the ferrous sulfate and sulfuric acid impurity components that need to be separated from the hydrolysis slurry are concentrated into the titanium dioxide waste acid; the first washing acid waste water is all discharged into the sewage station for neutralization treatment, or part of the first washing acid waste water is directly reused in the ilmenite acid hydrolysis section as a leaching liquid, and the remaining part is discharged into the sewage station for neutralization treatment; The specific steps are: Step 1: The hydrolyzed metatitanic acid slurry after cooling treatment is pumped to the high-pressure solid-liquid separation device through the low-pressure feed pressure pump P01, and the pumping pressure control value is set to p1. When the pressure after the pump P01 reaches the p1 value, the P01 pump is stopped to obtain the filter cake, the valve is switched, and the top water pump P02 is started. The pump outlet pressure is p2, and the process water or the higher concentration acid washing water collected in the front stage of the first washing is delivered to replace the residual concentrated acid liquid in the top filter cake. The running cumulative flow rate of the top water pump P02 is set to Q. When the cumulative flow rate reaches the set value, the top water pump P02 is stopped, and the high-pressure water squeezing pump P03 is started. The pumping pressure control value is set to p3, and the upper filter cake is further squeezed to squeeze out the residual sulfuric acid and ferrous sulfate components as much as possible; the filtrate produced by the above filter pressing is collected together and all used as titanium dioxide waste acid; Step 2: Discharge the filter cake obtained after the filter press in step 1, use the secondary washing acid wastewater to pulp the filter cake, filter it on the upper sheet, introduce the filtrate into the metatitanic acid recovery device, and then discharge the clear liquid into the sewage workshop; Step 3: The filter cake obtained after the upper filtration in step 2 enters the first wash, and the recycled second wash wastewater is used as the first wash water. The acidic wastewater generated by the first wash filtration is directly discharged or collected separately in two stages; If two-stage separate collection is adopted, the valve switching time is set to t2. During the period from 0 to t2, the acidic wastewater with higher concentration is collected in the water supply tank of the top water pump P02 for top material use. When the time reaches t2, the valve is switched to transport the remaining low-concentration acidic wastewater to the corresponding collection pool for reuse as ilmenite acid hydrolysis leaching liquid, or directly discharged to the sewage treatment station for neutralization and disposal; In the step 1, the value of p1 is 0.2~0.4Mpa, the value of p2 is 0.4~1.0 Mpa, and the value of p3 is 1.2~10.0 Mpa; the value of Q is 1.5~3.0 times the mass of the slurry titanic acid entering the solid-liquid separation device in batches; the value of t2 in step 2 is 5~10min.

2. The method for efficient solid-liquid separation of metatitanic acid slurry according to claim 1, characterized in that: The method of collecting most of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed titanic acid slurry in the titanium dioxide waste acid produced by the upper filtration means that more than 90% of the ferrous sulfate and sulfuric acid impurity components in the hydrolyzed titanic acid slurry are collected in the titanium dioxide waste acid produced by the upper filtration.

3. The efficient solid-liquid separation method of metatitanic acid slurry according to claim 1 or 2, characterized in that: The solid-liquid separation device in step 1 includes a high-pressure separation device of a plate and frame diaphragm filter press.

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