# US 2014/0191898 A1 · Radar level measurement

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- Number: US 2014/0191898 A1
- Document ID: US20140191898A1
- Status: Published application
- Kind: A1
- Application number: 14/126,394
- Filed: 2012-09-03
- Published: 2014-07-10
- Earliest claimed: 2011-09-06
- Assignees: Stamicarbon B.V.
- Inventors: Klement Riegman
- Web page: https://patentgrep.com/patent/US20140191898A1

## CPC

- G01F 23/284: Electromagnetic waves
- G01S 13/88: Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00)
- H01Q 1/225: {used in level-measurement devices, e.g. for level gauge measurement}
- H01Q 13/20: Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q 13/24: constituted by a dielectric or ferromagnetic rod or pipe (H01Q13/28 takes precedence)
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)

## Abstract

Disclosed is a method of measuring the level of a liquid in a vessel, such as a chemical reactor, by radar. The method particularly pertains to situations wherein a supercritical fluid is present above the liquid. More particularly, the method serves to cope with the typical vigorous circumstances of a chemical reaction, such as urea synthesis. The invention foresees the use of a tube extending into the liquid, so as to guide the radar waves to the surface level of the liquid.

## Claims

### Claim 1

A radar method for detecting the level of a liquid in a vessel wherein a supercritical fluid is present above said liquid, the method comprising transmitting electromagnetic waves into the direction of the liquid through a tube, wherein the tube extends to a bottom end placed within the vessel above a desired minimum level of the liquid, and wherein said bottom end is defined by a reflective surface, the tube further comprising at least one hole for venting gas, and at least one hole for allowing liquid to enter.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the at least one hole for allowing liquid to enter the tube is positioned near or at the bottom end of said tube.

### Claim 3 (depends on 1)

A method according to claim 1, wherein the at least one hole for allowing liquid to enter the tube comprises 2-20 holes of diameter 2-20 mm.

### Claim 4 (depends on 1)

A method according to claim 1, wherein the tube extends substantially vertically into the liquid.

### Claim 5 (depends on 1)

A method according to claim 1, wherein the tube enters the vessel from the side and has a bend, and extends further downwards into the liquid, wherein the tube contains a vent hole below the bend in the tube.

### Claim 6 (depends on 1)

A method according to claim 1, wherein the tube is made from a duplex ferritic-austenitic stainless steel having a high content of Cr and N, and a low content of Ni.

### Claim 7 (depends on 6)

A method according to claim 6, wherein the tube is made from a duplex, stainless steel alloy, containing, in percent by weight:
C maximally 0.05%;
Si maximally 0.8%;
Mn 0.3-4%;
Cr 28-35%;
Ni 3-10%;
Mo 1.0-4.0%;
N 0.2-0.6;
Cu maximally 1.0%;
W maximally 2.0%;
S maximally 0.01%;
Ce 0-0.2%;
the remainder being Fe and normally occurring impurities and additives, the ferrite content being 30 70% is 30-70% by volume, preferably 33 35% by volume.

### Claim 8 (depends on 6)

A method according to claim 6, wherein the vessel is a urea synthesis reactor and the liquid is a carbamate solution formed in urea synthesis.

### Claim 9 (depends on 1)

A method according to claim 1, wherein the tube is cone-shaped on the inside adjacent to a radar cone.

### Claim 10 (depends on 6)

A radar system suitable for being placed into a vessel, comprising a transmitter, a receiver and a tube connected at a top end to the transmitter and the receiver, and a bottom end that is closed off, the tube further comprising at least two holes at different distances from the bottom end, wherein the tube is made of a steel as defined in claim 6.

### Claim 11 (depends on 10)

The radar system of claim 10, wherein the vessel is a urea synthesis reactor.

### Claim 12 (depends on 3)

The method of claim 3 wherein the at least one hole for allowing liquid to enter the tube comprises 5-15 holes of diameter 3-10 mm.

### Claim 13 (depends on 7)

The method of claim 7 wherein:
C is maximally 0.03%;
Si is maximally 0.5%;
Mn is 0.3-1%;
Cr is 29-33%;
Mo is 1.0-1.3%; and
N is 0.36-0.55%.

### Claim 14 (depends on 7)

The method of claim 7 wherein the ferrite content is 33-35% by volume.