Method of manufacturing a combustibles sensor

• US 4,355,056 A
• Filed: 03/31/1981
• Issued: 10/19/1982
• Est. Priority Date: 03/31/1981
• Status: Expired due to Term

• Current Assignee: Elsag International NV
• Original Assignee: Babcock & Wilcox Company (Babcock International Group PLC)
• Inventors: Dalla Betta, Ralph A., Zimmerlin, Sharon L.
• Primary Examiner(s): Lusignan, Michael R.
• Application Number:
  US06/249,308
• Time in Patent Office: 567 Days
• Field of Search: 427/126.4, 338/34, 422/94, 23/232 E
• US Class Current: 427/126.4
• CPC Class Codes: G01N 25/32 using thermoelectric elements

Abstract

A method of manufacturing a differential thermocouple combustibles sensor is disclosed which makes the sensor relatively insensitive to sulfur poisoning. To accomplish this the catalytic thermocouple junction of a catalytic-non-catalytic junction pair is formed by coating it with a gel to increase the surface area and then with a chloroplatinic acid solution to make it catalytic. The catalytic junction is then treated with H₂ S to achieve a high catalyst surface area.

Claims

1. A method of manufacturing a combustibles sensor which is relatively insensitive to sulfur poisoning comprising the steps of:

providing a first temperature measurement device which has a temperature varying electrical property;

coating said temperature measurement device with a gel to form a high surface area substrate with increased surface area over said temperature measurement device;

coating said gel high surface area substrate with a catalytic material; and

treating said catalytic material coating with H₂ S to achieve a high surface area of the catalytic material.

2. The method of claim 1 including the further steps of:

providing a second temperature measurement device which has a temperature varying electrical property;

connecting said first temperature measurement device to said second temperature measurement device to form a differential temperature measurement device; and

coating said second temperature measurement device with a low surface area cement to form a non-catalytic surface.

3. The method of claim 1 wherein said gel is a mixture of γ

-alumina and a binding agent consisting of a colloidal suspension of the γ

-alumina.

4. The method of claim 1 wherein said coating of said high surface area substrate is done with a solution of chloroplatinic acid and water.

5. The method of claim 4 wherein said treating of said catalytic material with H₂ S is continued until the catalytic coating turns from yellow to black.

6. The method of claim 5 further including after said treating said catalytic material the steps of:

drying said treated catalytic material at approximately 100°

C. for approximately 20 min; and

heating said dryed catalytic material in approximately 500°

C. air for approximately 1 hr to oxidize any free sulfur or metal sulfides in the device.

7. The method of claim 2 further including after said step of coating said second temperature measurement device the further steps of:

drying said differential temperature measurement device at approximately 100°

C. for approximately 20 min; and

heating said differential temperature measurement device in approximately 500°

C. air for approximately 1 hr.

8. The method of claim 2 wherein said coating of said second temperature measurement device is done with Alundum cement having a particle size of 50 μ

m or smaller.

9. The method of claim 1 wherein said first temperature measurement device is a Chromel-Alumel thermocouple.

10. The method of claim 2 wherein said first and second temperature measurement devices are Chromel-Alumel thermocouples.