US 9,896,334 B2Granted

Process for purification of hydrofluoric acid including obtaining arsenious acid by-product

AssigneeMexichem Fluor, Sociedad Anonima de Capical Variable

InventorsIris Samantha Duran Castillo, Juan Alberto juárez García, Nilo Martínez Robles

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Abstract

A process for purification of hydrofluoric acid reduces the content of heavy metals, including arsenic, to values lower than five parts per million, without using any chemicals and with an integrated design of hot and cold streams that provide low energy consumption. The process allows extraction of heavy metals, especially arsenic, with minimal waste generation and while maintaining an original oxidation state, which for the case of arsenic is +3, so that the residue can he converted into a product with commercial value, such as arsenious acid. The process includes operation of four systems, namely, a hydrofluoric acid purification system, an arsenic concentration system, a hot water system, and a cold water system. The extraction of heavy metals is performed by synchronized operations of these four systems.

Claims15

Dependent claims

A process for purifying hydrofluoric acid including obtaining an arsenious acid (H3AsO3) byproduct, comprising the steps of:

(A) PURIFICATION OF HF (REMOVAL OF AsF3):
(a1) Feeding high-arsenic HF to a purifying column;
(a2) Evaporating the high-arsenic HF at a bottom of the purifying column;
(a3) Condensing low-arsenic HF that leaves a dome of the purifying column into liquid HF;
(a4) Returning a portion of the liquid HF that has left the purifying column to the purifying column;
and
(a5) Purging the bottom of the purifying column,
(B) CONCENTRATION OF AsF3:
(b6) Feeding high-arsenic AsF3 HF, which has an arsenic concentration of 20,000 to 60,000 ppm by weight, to a concentrator column;
(b7) Evaporating the high-arsenic AsF3 HF at a bottom of the concentrator column;
(b8) Condensing HF gas leaving a dome of the concentrator column into liquid HF;
(b9) Returning at least a portion of the liquid HF that has left the concentrator column to the concentrator column;
and
(b10) Purging the bottom of the concentrator column,
(C) HYDROLYSIS OF ASF3:
(c11) Storing the AsF3;
and
(c12) Hydrolyzing AsF3 purged by the concentrator column by reacting the AsF3 with water,
wherein the purifying and concentrator columns are provided in a system containing a cold water circuit and a hot water circuit connected with the columns.

16 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/640,387Filed 6 Mar 2015
Priority: MX MX/A/2014/01588518 Dec 2014
Published: US 2016/0176711 A123 Jun 2016
Granted: 20 Feb 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

C01B 7/196
Separation; Purification: by distillation
B01D 3/007
Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping: energy recuperation; Heat pumps
B01D 3/143
Fractional distillation or use of a fractionation or rectification column: by two or more of a fractionation, separation or rectification step
C01G 28/005
Compounds of arsenic: oxides; Hydroxides; Oxyacids