GB2089512A

GB2089512A - Process and Apparatus for Testing Fluids for Fouling

Info

Publication number: GB2089512A
Application number: GB8129072A
Authority: GB
Original assignee: Drew Chemical Corp
Current assignee: Drew Chemical Corp
Priority date: 1980-10-30
Filing date: 1981-09-25
Publication date: 1982-06-23
Also published as: GB2089512B; FR2493523A1; DE3136225C2; CA1173159A; BR8106313A; NL8104682A; DE3136225A1

Abstract

Deposition of scale 24 (fouling) from a fluid 16 is detected at various fluid flow rates by measuring the fluid temperature 8, with thermocouple 26, the surface temperature of a member 14 in the fluid flow having a heater element assigned at known rate. The fouling data, flow rate, & other data such as corrosion, pH & conductivity, are recorded & a computer generates therefrom a fouling factor which is time related to the other data. By introducing a quantity of antifoulant & monitoring its efficacy a final anti- foulant procedure may be derived. Flow rate may be measured as differential pressure across a venturi. <IMAGE>

Description

SPECIFICATION Process and Apparatus for Testing Fluids for Fouling The present invention relates to a process and apparatus for testing fluids for fouling, and more particularly to a process and apparatus for the insitu testing and simultaneously monitoring and recording of aqueous and non-aqueous fluid systems for fouling tendencies, and parameters such as conductivity, pH, turbidity and corrosion, as well as to the development of an antifoulant protocol or procedure.

The chemical water treatment industry has historically been involved with reducing or inhibiting the inherent scale forming or fouling tendencies of natural waters associated with large industrial cooling water systems. Many of the foulant components found in water systems originate with the incoming supply, but some contaminants enter the system from the local environment or from process contamination.

Fouling is an extremely complex phenomenon.

From a fundamental point of view, it may be characterized as a combined momentum, heat and mass transfer problem. In many instances, chemical reaction kinetics is involved, as well as solubility characteristics of salts in water and corrosion technology. It has been stated that if the fouling tendency of a cooling water could be accurately predicted before a plant is designed and built, significant capital savings might be realized through more accurate heat exchanger specifications.

Usually, it is normal practice to increase heat exchanger surface area to overcome losses in performance caused by fouling deposits, with such additional surface area often accounting for more than half of the actual surface area of the heat exchanger. When such design practice is employed within titanium, stainless steel and like expensive materials of construction, it can be appreciated that capital expenditure might be significantly reduced if data could be developed to anticipate and provide for an anti-foulant procedure.

Fouling of a heat transfer surface is defined as the deposition on a surface of any material which increases the resistance to heat transfer. The fouling tendency of a fluid in contact with a heat transfer surface is a function of many variables including the components of the fluid, which in the case of water include, inter alia, crystals, silt, corrosion products, biological growths, and process contaminates. Generally, deposits are comprised of a combination of several of these materials in relationship to, inter alia, the geometry of the heat transfer surface, materials of construction, and temperature, and thus chemical inhibition to solve the problem of a particular deposit involves a variety of different chemicals introduced at varying concentrations and at varying times.

Industry has resorted to the use of laboratory simulators or time lapse evaluations of process heat exchangers and test heat exchangers with the requirement that such equipment is taken off line, shutdown, opened and inspected to evaluate fouling problems and antifoulant procedures. In the case of process heat exchangers, such inspection usually results in significant plant down time and lost production. Evaluation covers the entire period of process operation and shows accumulated results, which include system upsets, process leaks, the loss of chemical feed or human errors. While the sampling and laboratory testing of fluids permits evaluation of the fluids, the results of laboratory testing are tedious and do not provide results of simultaneous evaluation.

The present invention in one aspect provides apparatus for testing a fluid to generate fouling data, which comprises: a piping assembly including a fluid inlet and a fluid outlet and a heat transfer test assembly, the heat transfer test assembly including a heating member comprising a heating element disposed within a conduit having a passageway for the fluid; means for measuring the temperature of the fluid entering the heat transfer test assembly; means for supplying a pre-selected quantity of electrical energy to the said heating element; means for measuring a wall temperature of the heating member; flow means for measuring the velocity of the fluid through the piping assembly; and means for generating fouling data from the said pre-selected quantity of electrical energy supplied to the heating element, the said measured temperature of the fluid and the said measured wall temperature of the heating member.

The invention in another aspect provides a process for testing a fluid to be passed through a unit in an indirect heat transfer relationship to monitor and record fouling data, which comprises: (a) connecting the unit in fluidflow communication with a test zone of a mobile assembly, the test zone including a heating member having a source of heat; (b) measuring the temperature of the fluid; (c) energizing the said source of heat; (d) measuring the temperature of the heating member during passage of the fluid through the test zone; (e) measuring the flow rate of the fluid; (f) monitoring and measuring at least one parameter of the fluid selected from corrosion, pH and conductivity; and (g) simultaneously recording the data of steps (b), (d) and (f).

Thus the present invention provides a mobile apparatus and process therefor including a heat transfer test assembly and related conduit and valve assemblies for connection in fluid flow communication to a heat transfer apparatus for in-situ testing of the fluid passing therethrough and including monitoring and recording apparatus. The heat transfer test assembly suitably includes a heating member for controlled heat input and thermocouples to measure the wall temperature of the heating member to permit fouling determinations at varying flow rates with simultaneous monitoring and recording thereof together with data, such as corrosion, pH, and conductivity.

There may thus be generated foulant data permitting substantially simultaneous implementation of, and evaluation of, an antifoulant procedure on the fluid passing therethrough and including monitoring and recording apparatus together with a source of antifoulants for controlled introduction into the fluid to evaluate efficiency of the antifoulant procedure.The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a cross-sectional elevational view of a heat transfer test assembly; Figure 2 is a piping diagram of the process and apparatus of the present invention including the heat transfer test assembly; and Figure 3 is a schematic diagram of the process and apparatus for continuously testing, monitoring and recording data relative to the heat transfer test assembly as well as for monitoring and recording data as to corrosion, conductivity, pH, and the like.

Referring now to Figure 1, there is illustrated a heat transfer test assembly 10, comprised of a tube member 12 and an inner cylindrical heating member 14 formed of a tube member 16 in which a high resistant heating element 1 8 is embedded within an insulating matrix 20, such as magnesium oxide. The heating member 14 is coaxially-positioned within the tube member 12 to form an annular fluid flow passageway 22.

Symmetrically-disposed in the tube member 16 of the heating member 14 are a plurality of surface thermocouples 26 for sensing wall temperature, generally disposed at positions corresponding to the hour hand at 3, 6, 9 and 12 o'clock.

The tubular member 12 is formed of any suitable transparent material, such as glass, to permit visual observation of flow as well as scale formation 24 about the surface of the heating member 14. The tube member 16 of the heating member 14 is formed of a metallic material, such as stainless steel, copper, titanium, mild steel, or admiralty metal, dependent on the fluid to be initially tested by passage through the test assembly 10 or inter case of existing units of a like metallic material as that in the unit. Normally, stainless steel is used for normal cooling water application whereas admiralty metal is employed for sea water and brackish water applications.

As more fully described hereinafter, the fouling tendency of a fluid may be evaluated by the passage of a fluid through the heat transfer test assembly 10 under controlled rates of flow and heat output from the heating element 1 8 through measurement of temperature drops between the tube member 16 und the fluid to permit a determination of the resistance of the scale formation 24 therefor.

The heat transfer test assembly 10 is positioned within a piping assembly 30 as shown in Figure 2, including an inlet conduit 31 and an antifoulant conduit 32 in fluid communication with a container 33 including a antifoulant via the discharge side of a pump 34. The piping assembly 30 includes flow meters 35 and 36, a rotameter 37 and a flow rate control valve 38. The inlet conduit 31 is in parallel flow communication with the flow meters 35 and 36 by conduits 42 and 44 under the control of valves 46 and 48, respectively. Conduits 42 and 44 are in fluid flow communication by a conduit 50 under the control of an isolation valve 52 with one end of the rota meter 37, with the other end of the rotameter 37 being in fluid flow communication by conduits 54 and 56 with the inlet end of the heat transfer test assembly 10.Conduit 44 is in fluid flow communication by a conduit 58 under the control of a by-pass valve 60 with conduit 56.

The outlet of the heat transfer test assembly 10 is in fluid flow communication by a conduit 62 and a conduit 64 under the control of an isolation valve 66 via the flow rate control valve 38 to an outlet 68 by a conduit 70. Conduit 62 is in fluid flow communication with conduit 70 by a conduit 72 under the control of a by-pass valve 74. The conduit 70 is provided with a flow cell 76 including a plurality of probes (not shown) to measure other parameters of the fluid, as more fully discussed hereinafter.

The flow meters 35 and 36 are preferably of the venturi type with each flow meter having a different design rating of flow rates and are electrically connected via transducers 78 to a differential pressure cell 80 and by leads 82 and 84, respectively, to sense the pressure drop across the flow meters 35 and 36. The piping assembly 30 is further provided with a thermocouple 86 to monitor the bulk inlet water temperature and with a high temperature cutoff 88.

In order to provide a sufficient range of flow velocities, a plurality of heat transfer test assemblies 10 of differing diameters may be used for interchangeable insertion into the piping assembly 30. The flow rate control valve 38 is preferably of the constant flow type with an internal pressure equalizer (not shown) to ensure flow at the pre-selected value. The rota meter 37 permits visual monitoring and may be electronically monitored by a differential pressure cell (not shown).

The piping assembly 30 is integrated or coupled with a monitoring and recording assembly 90 including components of the piping assembly 30, as shown in Figure 3, disposed on a support structure (not shown) for positioning within a mobile container (not shown), such as a trailer or van, for easy movement from location to location to test fluid passing through a unit, such as a heat exchanger or reactor, as more fully discussed hereinafter. The container is provided with environmental capabilities to provide preselected conditions of temperature and humidity to ensure proper functioning of the various units of the monitoring and recording assembly.

The monitoring and recording assembly 90 includes a power inlet assembly 92, an analog to digital converter 94 and a computer print-out assembly 96. The power inlet assembly 92 is comprised of a 110 Vac. inlet connector 98 including a transformer 100, a 220 Vac. inlet connector 102 and a 440 Vac. inlet connector 106 including a transformer 104 connected by leads 108 to a variable rheostat 110. Generally, 110 Vac. is utilized for the environmental capabilities with one of the other power sources utilized in the monitoring and recording capability.

The variable rheostat 110 is connected by leads 11 2 to a wattmeter transducer 114 providing a source of power by leads 11 6 for the heating element 18 of the tube member 16.

The transducer 114 generates a signal transmitted via a lead 118 to the analog-digital converter 94 representative of the power level of the heating element 1 8 of the tube member 1 6.

The thermocouples 26 and 86 generate signals representative of temperature transmitted via leads 120 to a reference junction 122 for transmission via leads 124 to the analog-digital converter 94.

The transducers 78 receive signals generated by the flow meters 35 and 36 and in turn transmit a signal via lead 126 and/or lead 128 to the differential pressure cell 80 which generates an analog signal representative of flow rate trasmitted by a lead 130 to the analog-digital converter 94.

The flow cell 76 includes a plurality of probes connected by leads 132, 134 and 136 to a conductivity monitor 138, a pH monitor 140 and a corrosion monitor 142, respectively, connected to the analog-digital converter 94 by leads 144, 146 and 148 respectively. As known, the analogdigital converter transforms analog information into digital output data, which in turn is transmitted by a lead 1 50 to the computer printout assembly 96 for recording in a reference time frame.

In operation, the monitoring and recording assembly 90 disposed on a suitable support structure and enclosed in a self-contained environmental container is caused to be positioned adjacent a unit operation or unit process, such as a heat exchanger or delignification digester, employing a fluid to be tested, inter alia, for fouling tendencies to permit evaluation and/or ready treatment to remedy such fouling tendencies. A source of power is connected to the power inlet assembly 92 and a flexible conduit placed in fluid flow communication with the unit operation or process, generally on the up-stream side thereof.

The circulating fluid is caused to flow via the conduit 31 into the piping assembly 30 via either flow meter 35 or 36 by control of the valve 46 or 48, respectively, and thence sequentially through the rota meter 37 via the conduit 50 under the control of the valve 52, through the heat transfer test assembly 10 via the conduits 54 and 56, through the flow rate control valve 38 via the conduit 62 and the conduit 64 under the control of the valve 66, and finally through the flow cell 76 via the conduit 70 to be discharged through the outlet 68 to waste or to be returned to the unit operation or process.

During such operational time period, power is supplied by leads 116 to the heating element 18 of the tube member 1 6 with the temperature of the wall of the heating member 14 being monitored to obtain an average temperature thereof. Simultaneously, the bulk fluid temperature is monitored by the thermocouple 86 together with the monitoring of the fluid velocity to determine what, if any, velocity effects there are on fouling under given operating conditions.

Water velocity is controlled by the constant flow valve 38 and is visually monitored by the rotameter 37 simultaneously with electronic monitoring by the differential pressure cell 80 sensing the pressure drop across either flow meter 35 or 36.

The wall thermocouple 26, the bulk water temperature thermocouple 86, the wattmeter transducer 114 and the differential pressure cell 80 are connected to the analog-converter 94 via the reference junction 1 22 to convert analog electrical signals to digital output signals which are transmitted for recording to the computer printout assembly 96, it being understood that the computer printout assembly is capable of effecting some computation to generate calculated data, such as a fouling factor. Such a fouling factor is time related to data from the conductivity monitor 138, the pH monitor 140 and the corrosion monitor 142. In this manner, various data is simultaneously collected of factors relating to fouling, etc.

The apparatus may be alternatively caused to be positioned adjacent a unit operation or process, such as a heat exchanger or delignification digester, employing a fluid to be tested, inter alia, for fouling tendencies to permit evaluation and develop an antifoulant procedure.

During such initial time period, the apparatus is operated as hereinbefore described to generate calculated data, such as a fouling factor. Such fouling factor is time related to data from the conductivity monitor 138, the pH monitor 140 and the corrosion monitor 142.

Thereafter, the pump 34 is energized for a predetermined time period or continuously to quantitatively introduce antifoulant into the piping assembly 30 with simultaneous monitoring of the factors together with simultaneous generation of fouling data to evaluate the efficacy of the antifoulant procedure. Monitoring and evaluation of the antifoulant procedure as well as changes thereto permit the evaluation of a finalized antifoulant procedure for a given aqueous or nonaqueous fluid system. Accordingly, the antifoulant treated fluid may be returned via the discharge conduit 70 to the unit operation or process thereby permitting constant evaluation of the antifoulant procedure for the unit operation or process.

The invention will be further described with reference to the following illustrative Example.

Example Cooling water for a gas processing plant having a pH of from 7.2 to 7.6 treated with 24 ppms of antifoulant chemicals including a combination of phosphonates, aromatic glycols and chelating agents generated a fouling factor of from 240 to 260. In addition to the antifoulant chemicals, there was introduced 1 50 ppms of a corrosion inhibitor and 10 ppms of a microbiocide (on a shock basis to the cooling water).

An antifoulant procedure was developed whereby there was added 1 50 ppms of a corrosion inhibitor, 50 ppms of a nonionic antifoulant and 50 ppms of a microbiocide together with a base to alter the range of pH to 8.2 from 7.8. The effects of the new procedure were determined by continued operation of the heat transfer test assembly 10 under like conditions whereby the resulting fouling factor was from 20 to 25, a ten fold reduction from that originality observed.

After completion of the development of an antifoulant procedure, the monitoring and recording assembly 90 was disconnected from the unit operation or process by closing valve 46 or 48 and disconnecting inlet conduit 31 from the fluid source. Thereafter, the monitoring and recording assembly 90 may be easily moved to anotherocation within the plant or to another plant site.

The process and apparatus of the present invention as related to the generation of antifoulant procedures is particularly suited in the development of antifoulant procedures through cooling systems, chemical processing, such as a Kamyr digester, or process water for condensers.

Claims

1. Apparatus for testing a fluid to generate fouling data, which comprises: a piping assembly including a fluid inlet and a fluid outlet and a heat transfer test assembly, the heat transfer test assembly including a heating member comprising a heating element disposed within a conduit having a passageway for the fluid; means for measuring the temperature of the fluid entering the heat transfer test assembly; means for supplying a preselected quantity of electrical energy to the said heating element; means for measuring a wall temperature of the heating member; flow means for measuring the velocity of the fluid through the piping assembly; and means for generating fouling data from the said pre-selected quantity of electrical energy supplied to the heating element, the said measured temperature of the fluid and the said measured wall temperature of the heating member.

2. Apparatus as claimed in Claim 1, wherein there is developed antifoulant procedure and including a conduit for introducing an antifoulant into the fluid.

3. Apparatus as claimed in Claim 1 or 2, including means for measuring at least one parameter selected from corrosion, pH and conductivity.

4. Apparatus as claimed in Claim 3, including an assembly for simultaneously recording the said pre-selected quantity of electrical energy to the heating element, the said measured temperature of the fluid, the said measured wall temperature of the heating member, the said measured velocity of the fluid through the piping assembly and the said at least one measured parameter.

5. Apparatus as claimed in any of Claims 1 to 4, further comprising a flow control valve.

6. Apparatus as claimed in Claim 5, wherein the flow control valve is a constant flow type control valve inclusing a pressure equalizer.

7. Apparatus as claimed in any of Claims 1 to 6, wherein the flow means includes a venturi device.

8. Apparatus as claimed in Claim 7, wherein the venturi device is connected to a differential pressure cell to generate a signal responsive to a pressure drop across the venturi device.

9. Apparatus as claimed in any of Claims 1 to 8, further including converter means to convert analog electrical signals to digital output signals.

10. Apparatus as claimed in any of Claims 1 to 9, supported on a movable structure within a chamber having environmental regulating capability.

11. Apparatus according to Claim 1 for testing a fluid to generate fouling data, substantially as herein described with reference to, and as shown in, the accompanying drawings.

1 2. A process for testing a fluid to be passed through a unit in an indirect heat transfer relationship to monitor and record fouling data, which comprises: (a) connecting the unit in fluid flow communication with a test zone of a mobile assembly, the test zone including a heating member having a source of heat; (b) measuring the temperature of the fluid; (c) energizing the said source of heat; (d) measuring the temperature of the heating member during passage of the fluid through the test zone; (e) measuring the flow rate of the fluid; (f) monitoring and measuring at least one parameter of the fluid selected from corrosion, pH and conductivity; and (g) simultaneously recording the data of steps (b), (d) and (f).

1 3. A process as claimed in Claim 12, wherein an antifoulant is introduced into the fluid while continuing steps (b) to (e) to develop an antifoulant procedure.

14. A process as claimed in Claim 12 or 13, wherein the said data is also recorded in a manner for further electronic transmission to a data bank.

1 5. A process as claimed in any of Claims 12 to 14, wherein the said unit is on stream.

1 6. A process as claimed in any of Claims 12 to 15, wherein the said fluid is after passage through the said test zone recycled to the said unit.

1 7. A process as claimed in any of Claims 11 to 16, wherein steps (b) to (e) generate an analog signal convertable to a digital signal which is recorded together with fouling data.

18. A process according to Claim 12 for testing a fluid to monitor and record fouling data, substantially as herein described with reference to