JPS6165148A - Calorimeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Chemical reactions involve the release or absorption of energy in the form of heat. The "heat of reaction" is a constant, reproducible characteristic value for a given chemical change. Furthermore, chemical reactions occur at widely different rates, and the time-varying nature of reaction rates is referred to as "reaction kinetics." Measurement of reaction heat and reaction rate is
A fundamental part of the experimental development of large-scale chemical manufacturing processes, concerned with process optimization and safety, and providing design parameters for manufacturing equipment. Any device used to measure heat is called a calorimeter, and numerous prior art calorimeters have been described for use in a variety of specific applications.

One of the prior art calorimeters applied in the study of chemical reactions
An example is described in US Pat. No. 3,994,164.

The invention described in Unknown Honor is a novel,
Concerning an improved calorimeter. This calorimeter can provide accurate measurements of the heat of reaction and instantaneous reaction rate.

This device offers excellent performance and one-use safety. By using a chemically inert metal reaction vessel rather than a glass vessel, a significantly reduced thermal time constant is obtained due to the thermal conductivity of metals which is 1000 times higher than glass. This can be confirmed by using a calorimeter to calculate the reactant (reαC-ti).
It is possible to respond more quickly to thermal fluctuations on mass, thus lowering the thermal detection threshold and reaching saturation heat flow type levels.
afhLx Level). External to the reaction vessel is a chemical feed stream (chetnic).
Providing a thermostatic mechanism for the feedstreams) provides accurate measurement of the characteristic heat of reaction.

In the absence of such a mechanism, the reactants would be heated or cooled by the different temperatures of the chemical feed streams. This causes significant measurement errors.

In the present invention, a heat insulating shield (αdiαba t 1c
The provision of the shield makes the present invention insensitive to ambient temperature variations, whereas prior art calorimeters are sensitive to changes in ambient temperature. From the standpoint of operator safety, the present invention uses a small amount of reactant, on the order of one-fifth to one-tenth the amount of reactant, completely avoids the use of fragile glass containers, and reduces It provides an excellent pressure relief mechanism with a gTm design that includes as large a vent as possible. These design patents create a scientific instrument that is the safest to operate in a conventional chemical laboratory, creating superior thermal overheating and greatly reducing the risk of potential explosion. do.

Accordingly, the present invention constitutes an advance in the art of reaction calorimetry and satisfies an existing need in the art.

According to the invention, an apparatus for use in calorimetric measurements of chemical reactions comprises a cylindrical reaction vessel made of chemically inert metal; has an airtight lid, a stirrer, a temperature sensor, and a stirrer.
(atibration) heater, several population monitors, and a two-stage pressure relief machine. The reaction vessel is surrounded by an insulating shield, excluding the heat flow following the vessel wall and lid 7 (l), thus minimizing thermal noise and errors due to undesired heat conduction paths. ing.

Heat can be added to or removed from the reactants to compensate for the heat of reaction and retain the system by the use of a heat exchanger placed below the flat bottom of the reaction vessel. . This heat exchanger consists of two thin insulated metal foil resistance heaters mounted on a rigid metal plate, the underside of which is still flowing at a high velocity.
It is cooled by a fluid and maintained at a constant temperature below the temperature of the reactants. The power dissipated in the control heater is regulated to ensure the removal of heat flow from the vessel to the circulating fluid heat sink and to maintain a constant concentration of 1 part of the reactant. Ru. Once the reaction begins, the control and power dissipation at the same time is controlled by the heat flow due to the reaction heat (
httatflux).

In this way, the power dissipation change in the controlled heater is linearly proportional to the rate at which heat is generated or absorbed by the reaction, and the slope of this proportionality then varies between the heater and the circulating fluid. and between the heater and the reactant, and the intercept (1nter
cept ) depends on the temperature difference between the container and the circulating fluid. Therefore, the characteristics of a calorimeter are determined during design by considering the sensitivity or, conversely, the saturation heat R,
flux) can be adjusted by selecting values for the above-mentioned parameters to maximize the flux. The thermal properties of the calorimeter are further influenced by the selection of high and low thermal impedance materials and by the selection of appropriate dimensions to direct the heat flow in the desired direction, and also by the use of thermal barriers such as the aforementioned thermal shields. controlled and regulated by

In a preferred embodiment of the invention, a digital computer is used to obtain heat measurements and to provide control of the power supplied to the heat exchanger equipment, as well as the feeding and agitation of the feedstocks (fegdstocks). Control speed, perform calculations, thermal and kinetic
) is used to graph the results. In other embodiments of the invention, analog controls are used for each area requiring electrical control; and measurements are displayed on an analog recording device.

The design of the preferred embodiment of the invention is optimized for isothermal operation, as described above. However, both adiabatic and temperature scanning modes of operation are also possible. In isothermal mode, heat is added to or removed from the reactants to offset the heat of reaction and maintain the temperature constant. In adiabatic mode,
Because the flow of heat to or from the reactants is blocked and the heat of reaction remains in the reactants, the temperature of the reactants is exponential, as governed by the thermodynamics and kinetics of the reaction. rises functionally. The reaction temperature is tracked by a thermal shield and circulating oil temperature. In the temperature scanning mode, the temperature of the reactants is increased stepwise, linearly, or in any other predetermined manner as desired by increasing the temperature of the circulating fluid and the thermal shield according to a temperature program.

This chemical reaction calorimeter was constructed on the design principle of cylindrical symmetry, as shown in FIG. Viewed from above, the device has a thermal n wall < t
It looks like a set of concentric metal cans that act as a mechanical barrier. The core of the calorimeter is the removable container (1) and its lid (2), which are made from chemically resistant metals. Zirconium is used in the prototype calorimeter to ensure corrosion resistance against strong mineral acids and bases. The reaction container has a lid (2
) is equipped with a large number of devices attached to it. The precision platinum resistance thermometer (RTD) (3) is 5XI.
It is conveniently used to detect the temperature of the reactants by the resolution of O-'”C.The reaction mixture is heated by a step motor (
A stirrer A (
4). Contains a resistance heater (7) used for calibrating the vessel Vi thermostat.

The temperature of the reactants is carefully controlled by a heat exchange device made up of heating and cooling elements. This design principle of simultaneous heating and cooling provides excellent temperature control and short thermal time constants.
A calorimeter thermostat is used in all heated areas to ensure constant temperature. Heating of the vessel is insulated with an 0,001 inch (approximately 0.025 nn) polymer film and a metal disk (8
) is achieved by a circular metal foil resistance heater glued to the top side of the , the lower side of the metal plate (8) enters from the inlet pipe (9) into two circular puntos (8).
It is cooled by a circulating fluid (low viscosity 7 recon oil in the prototype) that flows radially through the gap between The circulating fluids are simultaneously heated to provide excellent temperature control;
It is supplied from and returned to a reservoir which is then cooled.

A constant temperature differential between circulating oil and chemical reactants is an important design parameter, as discussed below.

All heat flow to and from the reaction vessel is by conduction through the flat base of the reaction vessel which is connected to the heat exchange mechanism. Heat flow through the walls and lid of the vessel is effectively eliminated by providing an insulating shield that maintains the temperature of the space surrounding the reaction vessel equal to the temperature inside the vessel. This insulating shield is an air oven contained within the metal can (12) and its lid (13). The insulating foil heater (14) is cooled by compressed air that flows out from the second can (16) and its lid (attached to the outer wall of the can (12)) and from a number of ducts (151).
17) and is exhausted through a vent pipe (not shown). The temperature of the air space inside the thermal shield is sensed by a second platinum resistance thermometer (RTD) (18) and maintained at the temperature of the chemical reactants by electronic control.

The heat exchange mechanism and insulating shield can are supported by nine pace blocks (19) made from polytetrafluoroethylene, selected for its high thermal impedance and suitability for high temperature operation. Heat exchanger(
The main body of 20) is also made of this material. The total calorimeter is
It is housed within an outer metal shell (21) comprising a lid (22) and a pace (23). The interior walls of this shell are filled with fiberglass insulation.

Assembling and disassembling the calorimeter is done inside! (13) and (17)
It is extremely simple since it is attached to the external lid (22) by means of tubular standoffs (25). Therefore, all three grandfathers are removed and inserted as a single assembly, as shown in Figure (2). Needle bearing and lip seα
l) stirrer shaft (6) supported by (26);
) is interrupted just above the reaction vessel a (2) and is reconnected by a gear coupling (27). The upper gear of the coupler has the outer and inner lids (13), (17), (2
2), the drive motor (5) and the shaft (8). The lower gear of the coupler is attached to the lower shaft,
and a reaction vessel (1) which can be removed separately;
remains together.

During operation of the calorimeter, the fluid chemical is passed through a number of inlet tubes (2
8) can be added to the reaction vessel sequentially or simultaneously. The temperature of this "titrant" is pre-balanced in a tubular heat exchanger (not shown) in close contact with the insulating shield can (12).

The heat exchanger is a coiled stainless steel tube glued to the inside of the can, and a separate pipe L7 is used for each reactant. Chemicals are mechanically pumped from an external reservoir through the balance tube and into the reaction vessel.

Pressure release gas venting of the reaction vessel (presurξre, 1
iej−υenting ) Id is accomplished at two levels. A small spring-loaded relief valve (not shown in Figure 1) is attached to the lid (2) and has a diameter of about 10 feet (3.17 m) to relieve slight excess pressure. Equipped with gas vent (υent). In case of large overpressures exceeding the capacity of the main degassing, the entire lid (2) of the reaction vessel is moved upwards to provide the largest possible degassing holes. Movement of the lid is enabled by a lid holder (29) loaded with a spill and a tongue connection (30) for the stirrer shaft. (not shown in Figure 1).

In preferred embodiments of the calorimeter, all control and measurement functions are performed using a digital computer to simplify operator interaction and provide design flexibility and application of control algorithms. In addition, a microprocessor-based controller provides timing, switching and control functions as well as host
st) included to facilitate communication to the computer.

Figure 3 illustrates the block diagram of an electronic control system. Two different digital interface paths are used = 16-bit parallel interface between the computer and the microprocessor. standard IEE
E-488 interface (8 bits 1,000 lines/byte)
Serial) is used for communication between the 7"L stone computer and several peripheral devices supplied with the TwinTaface protocol.

Microprocessor - controller is central processing unit (CPU)
, real-time clock/interconnected generator (CLOCK), digital interface controller (Ilo), relay multiplexer (f”1UX)
), four high-stability digital-to-analog converters (DACs)
, random access memory (RAM) and erasable FR
Contains OM (EFROM). The microprocessor provides convenient means for implementing the interconnection and switching of system components.

Data acquisition, decision making
ng) and control functions are performed independently by a digital computer.

High precision digital voltmeters are used to make voltage and resistance measurements of the entire system and are switched between the raft input lines by relay multiplexers (I, MUX) under computer control. Platinum RTD resistance measurement H5X10-”C resistance thermometer resolution,
Bonding effect! ,'unctioneffects), C, true with offset compensation.
) This is a 4-wire measurement. Platinum 1 (TD is traceable to the National Standards System (NBS))
1 with a response curve of 1. Quartz standard thermometer (
QUARTZ). The d' current in various resistive heaters is determined by measuring the voltage applied across the heater and multiplying by the current flowing in the circuit. Current is measured independently as a voltage across precision series current sensing resistors divided by known resistances. Therefore, Zewar measurements are absolute and have very high precision.

Power to the heater is provided by three programmable power supplies programmed from the computer via three of the four DACs. The fourth tvDAc is used to control and program the oil bath temperature. These 16 pit DA
C? -12” has a control resolution of 65.536 to 1.

In order to provide quantitative thermochemical information, the calorimeters described above use
Regardless of whether the mode of operation is isothermal or temperature scanning, it is necessary to maintain a constant temperature difference between the chemical reactants and the circulating oil heat tank. Operation under isothermal conditions is most easily understood.

If the temperature set point for the reaction is Tr and the temperature set point for the oil path is To, then Tr>
To and the difference ΔTo=Tr−Torri are positive and constant.

If the thermal resistance between the heater and the circulating oil is ROI degrees Watts, then the power dissipation qh in the control heater (section 8 in FIG. 1) is given by:

Under these steady state conditions, no heat flows into or out of the reaction vessel and Trli remains constant.

The value qh given by equation (1) represents the baseline for the experiment at a point where no reaction is occurring. When heat is generated in the reaction vessel at a rate of gr, either by a chemical reaction or by the application of power to section 7 of FIG. It must be removed quickly to avoid rising.The only available path for heat dissipation is through the bottom of the reaction vessel, through the control heater, and into the rapidly circulating oil. and the result is dissipation in the oil reservoir cooling system.

If the thermal resistance between the reactant and the heater is Rr, then Tr-To=qr (Rr+Ro)+qhRo
(2), and the formula (2) is Tr-To RrROR
Be transformed into O.

In equation (1), when q r = O, the baseline qh is (Tr-T
o)/Ro, the change in qh when qr〆0 is given by the left side of equation (3). Therefore, equation (4) is expressed as the change in power dissipation in the control heater Δ
qh is the ratio of thermal resistance Rr and Ro and the zero intercept (1nte
rcept ) with a slope determined by °C,
This suggests that the heat generated in the reaction is linearly proportional to qr °C. It is therefore clear that the heat of chemical reaction ΔDr can be measured by integrating the change in gas dissipation in the control heater during the course of the reaction.

△7'7 r=K f△q h, -d t
(5)O In this case the constant Kt, =: Ro/(Ro+Rr) is determined during the electrical calibration of the calorimeter.

These observations lead to a number of interesting considerations. The maximum power dissipation in the calorimeter is limited by Ro, which must be minimal for a reasonable ΔTo. The heat sensitivity of the calorimeter is maximized by increasing the Rr/Ro ratio so that a small reaction heat grating produces a large change in the heater temperature. On the other hand, 'Rr/
Decreasing Ro maximizes the heat flow that can be handled by the calorimeter. Since the ratio of thermal resistances Rr/Ro can be adjusted during the fabrication of the calorimeter, a meter can be constructed with any desired characteristics.

The dynamic characteristics of the calorimeter are the exponential terms c, -ezp(-t/T)]
(in this case the time constant of the Tf-j system)
cita-nce equivalent circuit
It can be inferred by constructing the formula for (-However, as discussed below, the response of a calorimeter is not limited by its natural time constant through the use of a control algorithm that provides a significantly reduced effective time constant.

The computer grogram used to control the calorimeter takes temperature readings from various sensors, relates the actual temperature to the desired temperature (set point), and corrects any differences by appropriate responses. I'll let you fix it too. Error (e
rror) signal ΔTI = set point - actual temperature) and the corresponding power level (power
1evel) is called a control algorithm. For insulation shields, conventional PID
A proportional/integral/derivative) algorithm was used and was found to be satisfactory. The functional form of this algorithm is qh = ・ΔT s + 2f ΔTs − dt + 3
・d(ΔTs), 1t (6) In the formula, ΔTs is the error signal for the heat shield. The coefficients of the three terms in equation (6) are , f, and 31″
minimum over-s
hoot) and ring gear 1” Iringing
) has been experimentally optimized to give fast response.

P to the calorimeter to respond faster than the original time constant.
The use of farces is suggested in the ID algorithm.The effective time constant can be reduced to a fraction of the original constant by adjusting the coefficient in equation (6).

The control algorithm for the vessel controlled heater is new and was discovered through experience to provide the best control. Regarding the container error signal △Tc, there is a quadratic dependency relationship (qlL
adratic dttpgnde? The PI form of the algorithm (without derivative term) with Lce ) was used.

qh, ・ΔTc・1ΔTcJ+ 4fΔTc・1Δ
Tc 1dt In this case, 1ΔTcl indicates the absolute value of the error signal.

The effect of this algorithm' is to make the heater power qh essentially constant when ΔTc is negligibly small, but for larger Tc it becomes linearly dependent (1 in.
The workmanship that ear dependency) allows is to change q quickly. The result of this approach is a noise-free baseline (constant qh) and a very rapid return to the set point temperature after thermal disturbance (eg, the beginning of the reaction). 3 and K to the coefficients of different values to make the thermal response the same during the heating and cooling cycles.

is used for the positive and negative error signals ΔTc. This 7"L effectively compensates for the different efficiencies of the heating and cooling elements of the control system.

The operation of chemical reaction calorimeter is based on the power compensation principle. In order to establish the validity of the heat release data provided by the calorimeter, it is necessary to determine the linearity of the controller response by calibration and to determine the accuracy of the heat flow measurements by testing known chemical systems. Rarely.

The linearity of the controller power-response was determined using a vessel containing water fl15 (1'). In this experiment the temperature difference between the reaction vessel and the circulating fluid was maintained at 30 °K. The power was A range of 0 to 40 watts was applied to the calibrated heater.The power response of the control heater was found to be a linear function of the calibrated heater power, as shown in Figure 4.Synthesis Thermal resistances RO and Rr can be inferred from the slope of this calibration plot and the baseline nowa qh.

The values for the calibration constant (see equation 5) are: The performance of the calorimeter was tested by acid-base neutralization reaction experiments. Tris-(hydroxymethyl)aminomethane (TRI
Four repeated measurements of the enthalpy of neutralization of S) and hydrochloric acid give an average experimental value of -Ll, 55Kca 11 mol, which is in contrast to the value given in the literature -LL, 55KCQ 11 mol(1)
It's wonderfully consistent. A typical plot of controller power versus time for this experiment is evident in FIG.

(HOc, i2)3CNH3+ c, -a-b, c-
The areas of the plot marked d, ef, and g indicate the baseline for the experiment.

Nosewer displacement in b-c and j'-g (ezcl
The response in region d is due to the acid-base neutralization reaction. The rate of this proton exchange reaction is extremely fast compared to the response time of the calorimeter, and a boxcar-shaped power-response curve is obtained with edges corresponding to the beginning and end of the titration. Therefore, kinetic analysis is not relevant to this reaction.

Proof of calorimeter performance is non-aqueous
Obtained by organic chemical reaction in uS) system. p-Toluenesulfonic acid (7) as a catalyst - T S A I
The heat of reaction for the ethanolysis of acetic anhydride is
Determined as -14,38K cal 1 mol in 4 tests.

The experimentally measured heat of reaction has not been published in the literature.

However, the heat of reaction is the average contribution of functional groups to the heat of combustion of organic compounds (confribwtio).
Hand, Ritsukuni (Eandrick) based on
) was estimated to be -14,26Kcal 11 moles. The curve of heat flow versus time is shown in FIG.

In the above embodiment, the electrical calibration pulse is in the region d-e
It is applied before and after the reaction that occurs in between. Power displacement (etc.
A plateau is reached which is initially rapid and determined by the rate of addition. However, as the reagents are consumed, the reaction rate decreases and the p-power response decreases. After the addition of reagents is complete, the reaction continues for a while at a second-order reaction rate I 5eco
order kinetics), and the power response decays in conjunction with this rate law. The second-order rate constant for this reaction was determined from the analysis of the nozzle curve.
) is obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the mechanical arrangement of an exemplary embodiment of the device of the invention, also in cross section. FIG. 2 is a diagram of an easy means of assembling and disassembling the device by connecting the various lids and gear couplings of the stirrer side drive shafts. FIG. 3 is a block diagram of the electrical control and measurement component interconnections of a preferred embodiment of the invention. FIG. 4 is a graphical representation of the linear response of the control heater/power as a function of the power dissipated by the calibration heater of the present device. FIG. 5 is a graphical representation of a typical use of the apparatus in the study of rapid acid-base reactions. FIG. 6 is a graphical representation of the slow organic reaction carried out within the apparatus.・l・・・・・・
・Container 2...Rose 3...Resistance thermometer 5...Stepping motor 7...Resistance heater 8...Metal desk, metal plate 9...
・Inlet pipe 11...Outlet pipe 12...Metal can]7...Lid 18...Resistance thermometer 20...Heat exchanger Patent Applicant: American Cyana Company FIG, 3.
4 0. 5 1 1.5
2sakima (ginu)

Claims (1)

[Claims] 1. A calorimeter used to test chemical processes, comprising: a. an airtight lid, a stirrer mechanism, a temperature sensor, a calibration heater, and several chemical inlet ports; and a two-stage pressure relief mechanism; b. closely attached to the bottom of the reaction vessel to control the flow of heat to the vessel and its reactants, at a specified temperature; a heat exchanger comprising an electric heater mounted on a circulating metal plate cooled by a circulating fluid; c. an insulating shield comprising a cylindrical barrier surrounded by and cooled by a flowing gas and provided with a temperature sensor; d. to equilibrate the temperature of the chemical feed stream; It's hot,
A constant temperature (in
e. an easy mechanism for assembling and disassembling the device and gaining access to the reaction vessel, in which the various lids to the cylindrical chamber are connected as a single assembly; f. a pump, a heater, a cooling system and a temperature sensor; a reservoir for the circulating fluid that is responsive to the temperature sensor and that is responsive to the temperature T of the reactant;
_r, the temperature T_s of the insulating shield, and the temperature T_o of the circulating fluid, which in a preferred embodiment of the invention includes a digital computer controller, and in other embodiments includes an analog controller. An electronic adjustment means comprising a controller, each of the above-mentioned controllers b
, c and f, electronic regulator means for regulating the balance between heating and cooling by regulating the power dissipated into the heating element while under constant cooling from the cooling element; A calorimeter characterized by comprising: and; 2. A flat circular insulated foil adhered to a support plate, in which the heat exchanger is cooled by a fluid flowing radially between the plate and the second plate from the center to the edge or vice versa. Claim 1, wherein the cooling efficiency of the fluid remains unchanged and the efficiency of the heater is adjusted to adjust the temperature of the reactant contained within the vessel. Apparatus described in section. 3. A covered cylindrical chamber in which the insulating shield is wrapped with a glued foil heater and uniformly cooled by pressurized gas flowing from a number of ducts surrounding the insulating shield. 3. The apparatus of claim 2, wherein the heating and cooling equilibrium maintains a temperature in the chamber equal to the temperature of the reactants. 4. The temperature of one or more chemical feed streams is controlled by a tubular heat exchanger bonded to the interior surface of the insulating shield in intimate thermal communication with the heating and cooling mechanisms of the insulating shield. 4. A device according to claim 3, which upon use is already equilibrated with the reactants in the vessel. 5. The cooling fluid is equipped with a circulation system and a temperature sensor, an electric heater, a cooling system, and a temperature regulation mechanism represented by suitable means for accurately regulating the temperature of the circulation fluid. 3. The device of claim 2, wherein the device is supplied with a reservoir. 6. A device capable of relieving the build-up of excess pressure by means of a two-stage mechanism, a. Approximately 5.46mm)
a small adjustable valve with a vent hole; b. a spring-loaded retainer for the lid and a bellows coupling for the agitator shaft;
The cap is combined to allow longitudinal displacement of the lid and the shaft in order to provide the largest possible vent holes to relieve large overpressures and guarantee maximum safety during operation of the calorimeter. 2. The apparatus of claim 1, further comprising: a collapsible retention mechanism for the lid of the reaction vessel. 7. By means of a heat exchanger according to claim 2, in which the temperature difference between the oil reservoir and the chemical reactant acts in cooperation with the fluid thermostat and circulation system of claim 5. The temperature of the reactants is kept constant or is made to follow a predetermined change, while the heat of reaction and the reaction rate are controlled in an electrically controlled heater located in the heat exchanger. A method of operating the device according to claim 1, measured by proportional adjustment of the dissipation of power. 8. The power dissipation gh in the control heater disposed in the heat exchanger according to claim 2 causes the temperature error signal Δ
is adjusted proportionally to the time integral of the signed square of T, plus the signed square of the temperature error signal, such that the temperature error signal is the difference between the instantaneous temperature of the chemical reactant and the particular temperature set point. The following formula ▲ includes mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, K_1 and K_2 are constants with different magnitudes for positive and negative temperature error signals, and |△T| A method of operating a device according to claim 1 according to the relationship: expressed in absolute value.