CN101603909A - A Test Method for Saturation Vapor Pressure of Heavy Metal Chloride in Complex System - Google Patents

Abstract

The invention belongs to the field of environmental engineering, in particular to a test method for the saturated vapor pressure of heavy metal chlorides in complex systems. It is characterized in that the airflow carrying method is selected as the basic method, and an inert gas is selected, that is, the carrying gas flows over the sample at the test temperature. When the vapor of the sample to be tested is saturated by the carrying gas, the sample in the mixed gas The partial pressure is equal to the saturated vapor pressure of the substance at the same temperature; the relationship between the saturated vapor pressure of heavy metal chlorides in a complex system and the weight loss of the sample is as follows: Among them: M _M —the molar mass of the heavy metal to be measured, g·mol ^-1 ; R—constant, 8.314J·K ^—1 ·mol ^—1 ; T—temperature, K; ΔW _M ——the heavy metal element to be measured weight loss, g; V _c —— gas volume; m ³ . The invention obtains the saturated vapor pressure value of the heavy metal chloride in the complex system more accurately; the acquisition of the saturated vapor pressure value of the heavy metal chloride is helpful for promoting the separation and recovery of heavy metals in the process of melting fly ash and dust, and realizing such hazardous waste resources It is of great significance to detoxify and completely harmless.

Description

The method of testing of saturation vapor pressure of heavy metal chloride in a kind of complex system

Technical field

The invention belongs to field of environment engineering, specially refer to the method for testing and the device of saturation vapor pressure of heavy metal chloride in the complex system.

Background technology

High-temperature heat treatment industry is annual can to produce a large amount of flying dust and dust, the flying dust after burning as solid refuse, dust that the metal smelt industry produces in process of production or the like.This class material is listed in dangerous goods and needs special processing owing to containing too high harmful heavy metal such as Pb, Cd etc.The measure of taking from present countries in the world, melt process are a kind of disposal routes that application prospect is arranged most.Except can efficiently subtracting the appearance, its biggest advantage is to separate and to reclaim some heavy metal resources by means of the high volatile volatile of heavy metal.In addition since at high temperature the processing time longer, the toxic organic compound matter such as the dioxin that are contained in the discarded object can suffer effective destruction, if the harmful heavy metal volatilization can be separated to a certain degree, can reach the thoroughly innoxious of final residual thing.Therefore, in this class danger wastes process of melt process, thoroughly innoxious for the fully recycling and final residual thing of realizing heavy metal resources, the at utmost volatilization of heavy metal is its necessary condition.

On the thermodynamics, the necessary condition that produces the volatilization behavior be the saturated vapour pressure of material greater than its dividing potential drop in gas phase, so saturated vapour pressure is the important thermodynamic parameter of decision material volatilization behavior.In the danger wastes such as industrial dust that preamble is mentioned and flying dust, it is CaO, SiO that common matrix is formed ₂, FeO/Fe ₂O ₃, Al ₂O ₃Deng containing Partial K, Na, S, Cl and heavy metal Zn, Pb, Cd etc. simultaneously, the flyash ingredient for producing in certain waste solid incinerator burning process as shown in table 1 below.In this class flying dust of melt process and the dust process, these compositions have constituted the polynary slag/molten salt system of a complexity, and for heavy metal, the saturated vapor pressure in this slag/molten salt system is the important thermodynamic parameter of its volatilization behavior of decision.In addition, can grasp its activity information, and then understand the mechanism that reacts to each other between each composition in the heavy metal that to inquire into and the slag/molten salt system by saturated vapour pressure.

Studies show that in a large number, often contain a certain amount of Cl element in the danger wastes such as above-mentioned dust and flying dust, and chloride is the important form of heavy metal volatilization under the hot conditions.Therefore, the acquisition of saturation vapor pressure of heavy metal chloride value in the complex system is for separate reclaiming heavy metal resources to greatest extent, realizing that danger wastes is thoroughly innoxious and have an important theory directive significance.

The flyash ingredient that certain waste solid incinerator of table 1 produces

Summary of the invention:

The objective of the invention is to select a kind of suitable saturated vapour pressure assay method, and it is revised and is improved according to the volatilization characteristics of heavy metal chloride in the complex system, corresponding testing device is finished in design according to measuring principle simultaneously, comparatively accurately obtains the saturated vapour pressure value of heavy metal chloride in the complex system on this basis.

The mensuration of saturation vapor pressure of heavy metal chloride in the complex system, it is characterized in that selecting for use the air-flow method of carrying is basic skills, and according to actual conditions it is revised and improves.The ultimate principle that air-flow carries method is that selected a kind of inert gas (promptly carrying gas) flows through above the sample that is under the probe temperature, when the steam of sample to be tested is carried gas when saturated, the dividing potential drop of sample promptly equals the saturated vapour pressure of this material under synthermal in the mixed gas.The weightless relation of testing sample saturated vapour pressure and sample is as follows:

P＝ΔWRT/MV _c (1)

Wherein: M---the molal weight of volatilization gas, gmol ^-1

R---constant, 8.314JK ^-1Mol ^-1

T---temperature, K;

Δ W---weight loss, g;

V _c---gas volume; m ³

Content of the present invention generates situation at following two kinds of different heavy metal chlorides and describes respectively.

(1) have only a kind of heavy metal chloride to generate

For example, for CaO-FeO/Fe ₂O ₃-SiO ₂-Al ₂O ₃-ZnO-CaCl ₂In the system, calculation of thermodynamics shows that Zn is only with ZnCl in the 973K-1033K temperature range ₂A kind of form volatilization.Selected probe temperature T in this temperature range, sample is at this probe temperature T (K) and suitable carry constant temperature a period of time t (min) under gas flow rate v (l/min) condition, sample cools off under inert atmosphere conditions after the off-test, obtain the Zn content in the sample before and after the test by the icp analysis method, and then obtain in the thermostatic process volatile quantity Δ W of Zn in the sample _Zn(g).Because Zn is only with ZnCl ₂A kind of form volatilization, and then ZnCl ₂Volatile quantity Δ W _ZnCl2(g) can be by Δ W _Zn(g) calculate:

$\mathrm{\&Delta;}{W}_{\mathrm{<figure-callout\; id="2"\; label="ZnC\; l"\; filenames="A2009100888210009H1.png"\; state="\{\{state\}\}">ZnC</figure-callout>}{l}_{}{}_2}=\frac{\mathrm{\&Delta;}{W}_{\mathrm{Zn}}}{65}\&times;136---\left(2\right)$

And then ZnCl in this system ₂Saturated vapour pressure can be obtained by following formula (3):

${\mathrm{<figure-callout\; id="2"\; label="P\; ZnCl"\; filenames="A2009100888210009H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_{{\mathrm{ZnCl}}_{}}=\frac{\mathrm{\&Delta;}{W}_{\mathrm{<figure-callout\; id="2"\; label="ZnC\; l"\; filenames="A2009100888210009H1.png"\; state="\{\{state\}\}">ZnC</figure-callout>}{l}_{}{}_2}\mathrm{RT}}{{\mathrm{<figure-callout\; id="2"\; label="M\; ZnC\; l"\; filenames="A2009100888210009H1.png"\; state="\{\{state\}\}">M</figure-callout>}}_{\mathrm{ZnC}{l}_{}}\mathrm{vt}/1000}=\frac{\mathrm{\&Delta;}{W}_{\mathrm{Zn}}\mathrm{RT}}{M_{\mathrm{Zn}}\mathrm{vt}/1000}---\left(3\right)$

In the formula, M _ZnCl2, M _Zn-be respectively ZnCl ₂, simple substance Zn molal weight, g/mol.

(2) there is two or more heavy metal chloride to generate

For example, for CaO-FeO/Fe ₂O ₃-SiO ₂-Al ₂O ₃-PbO-CaCl ₂In the system, calculation of thermodynamics shows that the volatilization gas kind of Pb in the 973K-1033K temperature range is PbCl ₂With two kinds of PbCl.Selected probe temperature T (K) in this temperature range, sample is at this probe temperature T (K) and suitable carry constant temperature a period of time t (min) under gas flow rate v (l/min) condition, sample cools off under inert atmosphere conditions after the off-test, obtain the Pb content in the sample before and after the test by the icp analysis method, and then obtain in the thermostatic process volatile quantity Δ W of Pb in the sample _Pb(g).Because Pb is with PbCl ₂With two kinds of form volatilizations of PbCl, this test result is PbCl and PbCl ₂The saturated vapour pressure sum, concrete computation process is as follows:

Suppose P _PbCl, Δ W _PbCl, M _PbCL represents the saturated vapour pressure of PbCl, weightlessness, the molal weight that volatilization causes respectively;

P _PbCl2, Δ W _PbCl2, M _PbCl2Represent PbCl respectively ₂Saturated vapour pressure, the volatilization weightlessness, the molal weight that cause.

Carry the test philosophy of method according to air-flow, set up following formula (4), (5):

P _PbCl＝ΔW _PbClRT/(M _PbClvt/1000) (4)

P _PbCl2＝ΔW _PbCl2RT/(M _PbCl2vt/1000) (5)

The two saturated vapour pressure sum P then _PbCl2+PbClFor:

P _PbCl2+PbCl＝P _PbCl2+P _PbCl＝(ΔW _PbCl2/M _PbCl2+ΔW _PbCl/M _PbCl)RT/(vt/1000)

＝(N _PbCl2+N _PbCl)RT/(vt/1000)＝N _PbRT/V＝ΔW _PbRT/(M _Pbvt/1000) (6)

In the formula, N _PbCl, N _PbCl2, N _Pb-be respectively PbCl, PbCl ₂, and the molal quantity of total Pb of volatilization;

Δ W _PbThe weightlessness of-Pb element, g; M _PbThe molal weight of-Pb, g/mol;

Formula (3), (6) are available with a kind of form, and formula (7) is expressed:

$P_{M{\mathrm{Cl}}_x}=\frac{\mathrm{\&Delta;}{W}_M\mathrm{RT}}{M_W\mathrm{vt}/1000}---\left(7\right)$

In the formula,

The saturated vapour pressure of-tested heavy metal chloride, Pa

Δ W _M, M _M-be respectively weightlessness (g) and the molal weight (g/mol) thereof of heavy metal element M in thermostatic process.

Characteristics of the present invention are: at first utilize calculation of thermodynamics to determine the temperature range that heavy metal only volatilizees with chloride form in the complex system to be measured; Secondly under a certain specific temperature conditions in this temperature range, utilize the air-flow method of carrying to obtain sample weightlessness in special time t (min) scope, and, can obtain the saturated vapour pressure of heavy metal chloride by formula (7) in conjunction with the weight loss of testing front and back this heavy metal element itself.When having only a kind of heavy metal chloride to form, by formula (7) acquisition is that this muriatic saturated vapour pressure value is (as ZnCl ₂), if when having two or more heavy metal chloride to form, what obtained by formula (7) is that the saturated vapour pressure sum of these several heavy metal chlorides is (as PbCl and PbCl ₂).

It is basic skills that the present invention selects the air-flow method of carrying for use, and according to actual conditions it is revised and improves, and comparatively accurately obtains the saturated vapour pressure value of heavy metal chloride in the complex system.The acquisition of saturation vapor pressure of heavy metal chloride value is reclaimed, is realized this class danger wastes resource and thoroughly innoxiously have an important theory directive significance for the separation that promotes heavy metal in flying dust and the dust melt process process.

Description of drawings:

Fig. 1: air-flow carries the test unit of saturation vapor pressure of heavy metal chloride in the method testing complex system

This device mainly comprises five parts: (1) carries gas source, carries gas and selects pure Ar for use, feeds reaction zone (11 parts among the figure) with constant speed; (2) import system adopts good sealing performance plastic cement pipe, places resistant to elevated temperatures insulating plug simultaneously on the reaction tube xsect, and is very low to the gas phase diffusion of inlet outside to guarantee the reaction zone saturated vapour, so that negligible degree (2,12 parts among the figure); (3) vapo(u)rous district is placed on the middle part that solid sample in the porcelain boat places this zone, guarantees in the test process that specimen temperature evenly and prevent unnecessary chemical reaction, keeps the saturated vapour dividing potential drop constant (3,7 parts among the figure) of sample; (4) guiding system adopts the plastic cement pipe as the gas guiding system, places resistant to elevated temperatures insulating plug simultaneously on the reaction tube xsect, makes gas phase diffusion reduce to minimum (5,6 parts among the figure) in the exit; (5) control system comprises temperature-controlling system, and mass-flow gas meter carries gas flow rate (4,8,9,10 parts among the figure) in order to control.

1. fire resisting material of furnace body; 2. gas feeding pipe; 3. porcelain boat and sample; 4. sample temperature thermocouple; 5 outlet pipes; 6. insulating plug; 7. quartz ampoule; 8. attemperating unit; 9. mass-flow gas meter; 10. attemperating unit thermopair; 11.Ar gas cylinder; 12. insulating plug.

Fig. 2: the CaO-FeO/Fe that utilizes this method to obtain ₂O ₃-SiO ₂-Al ₂O ₃-ZnO-CaCl ₂ZnCl in the system ₂The relation of saturated vapour pressure and temperature

Fig. 3: the CaO-FeO/Fe that utilizes this method to obtain ₂O ₃-SiO ₂-Al ₂O ₃-ZnO-CaCl ₂PbCl in the system ₂With the saturated vapour pressure of PbCl and the relation of temperature

Embodiment:

1. calculation of thermodynamics is determined the temperature range that heavy metal only volatilizees with chloride form in the system to be measured;

2. in the temperature range that 1 determines, choose probe temperature T, utilize the air-flow method of carrying make sample under this temperature conditions, (it is always weightless to obtain sample after the cooling for v, l/min) constant temperature a period of time t (min) under the condition for the specific gas flow rate that carries;

3. utilize the icp analysis method to obtain content of beary metal in the sample of test front and back, and then obtain heavy metal volatile quantity Δ W _M

4. obtain saturation vapor pressure of heavy metal chloride by formula (7).What obtain when having only a kind of chloride to form is this muriatic saturated vapour pressure, and what obtain when having two or more chlorides to form is several chloride saturated vapour pressure sums.

Claims (3)

1. A test method for heavy metal chloride saturated vapor pressure in a complex system is characterized in that it is the basic method to select a gas flow entrainment method, and select a kind of inert gas that is to carry the gas to flow through above the sample at the test temperature. When the vapor of the sample to be tested is saturated by the entrained gas, the partial pressure of the sample in the mixed gas is equal to the saturated vapor pressure of the substance at the same temperature; the relationship between the saturated vapor pressure of the sample to be tested and the weight loss of the sample is as follows: P=ΔWRT/MV _c (1) Among them: M—the molar mass of volatile gas, g·mol ^-1 ; R—constant, 8.314J K ^-1 mol ^-1 ; T - temperature, K; ΔW——weight loss, g; V _c - gas volume; m ³ . 2. the test method of heavy metal chloride saturated vapor pressure in a kind of complex system as claimed in claim 1, it is characterized in that for CaO-FeO/Fe ₂ O ₃ -SiO ₂ -Al ₂ O ₃ -ZnO-CaCl ₂ in the system , thermodynamic calculations show that Zn only volatilizes in the form of _ZnCl in the temperature range of 973K-1033K; the test temperature T is selected in the temperature range of 973K-1033K, and the sample is selected at the test temperature T (K), and the carrier gas is selected as required Under the condition of flow rate v(l/min), the temperature is kept constant for a period of time t(min). After the test, the sample is cooled under the condition of an inert atmosphere. The Zn content in the sample before and after the test is obtained by ICP analysis method, and then the Zn content in the sample during the constant temperature process is obtained. Volatility ΔW _Zn (g); Since Zn only volatilizes in the form of ZnCl ₂ , the volatile amount ΔW _ZnCl2 (g) of ZnCl ₂ can be calculated by ΔW _Zn (g): $\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; ZnC</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; Zn</span>}}}{\mathrm{<span\; class="notranslate">\; 65</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 136</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ And then ZnCl in this system _Saturated vapor pressure is obtained by following formula (3): ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; ZnC</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; Z</span>}{\mathrm{<span\; class="notranslate">\; nCl</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; RT</span>}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{{\mathrm{<span\; class="notranslate">\; ZnCl</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; vt</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 1000</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; Zn</span>}}\mathrm{<span\; class="notranslate">\; RT</span>}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; Zn</span>}}\mathrm{<span\; class="notranslate">\; vt</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 1000</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ In the formula, M _ZnCl2 and M _Zn - are the molar masses of ZnCl ₂ and elemental Zn, g/mol, respectively. 3. the test method of heavy metal chloride saturated vapor pressure in a kind of complex system as claimed in claim 1, it is characterized in that for CaO-FeO/Fe ₂ O ₃ -SiO ₂ -Al ₂ O ₃ -PbO-CaCl ₂ in the system , thermodynamic calculation shows that in the 973K-1033K temperature range, the volatile gas species of Pb are two kinds of _PbCl and PbCl; in the 973K-1033K temperature range, the selected test temperature T (K), the sample is at the test temperature T (K), According to the needs, select the constant temperature for a period of time t (min) under the condition of carrying gas flow rate v (l/min). After the test, the sample is cooled under the condition of an inert atmosphere. The Pb content in the sample before and after the test is obtained by ICP analysis method, and then the constant temperature is obtained. The volatilization amount ΔW _Pb (g) of Pb in the sample in the process; Since Pb volatilizes in two forms of PbCl and PbCl, the test _result is the sum of the saturated vapor pressures of PbCl and _PbCl , and the specific calculation process is as follows: It is assumed that P _PbCl , ΔW _PbCl , and M _PbCl represent the saturated vapor pressure, weight loss caused by volatilization, and molar mass of PbCl, respectively; P _PbCl2 , ΔW _PbCl2 , and M _PbCl2 represent the saturated vapor pressure, weight loss and molar mass of PbCl ₂ respectively; According to the test principle of the airflow entrainment method, the following formulas (4) and (5) are established: P _PbCl = ΔW _PbCl RT/(M _PbCl vt/1000) (4) P _PbCl2 = ΔW _PbCl2 RT/(M _PbCl2 vt/1000) (5) Then the sum of the two saturated vapor pressures P _PbCl2+PbCl is: P _PbCl2+PbCl ＝P _PbCl2 +P _PbCl ＝(ΔW _PbCl2 /M _PbCl2 +ΔW _PbCl /M _PbCl )RT/(vt/1000)＝( _NPbCl2 + _NPbCl )RT/(vt/1000)＝ _NPb RT /V＝ΔW _Pb RT/(M _Pb vt/1000) (6) In the formula, _NPbCl , _NPbCl2 , _NPb -respectively PbCl, _PbCl2 , and the molar number of the total Pb volatilized; ΔW _Pb -Pb element weight loss, g; M _Pb -Pb molar mass, g/mol; Formulas (3) and (6) can be expressed in the same form, namely formula (7): ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; MC</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; RT</span>}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; vt</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 1000</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$ In the formula,

-The saturated vapor pressure of the measured heavy metal chloride, Pa ΔW _M , M _M - are the weight loss (g) and molar mass (g/mol) of the heavy metal element M in the process of constant temperature, respectively.

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