Low energy production process for producing paper pulp from lignocellulosic biomass

Abstract

A low energy production process for producing paper pulp from lignocellulosic biomass, the process comprising the following successive steps: a) extracting lignins and hemicellulose from lignocellulosic biomass by putting at least one solid lignocellulosic raw material in the presence of a mixture, composed only of water and of formic acid, at atmospheric pressure and under controlled conditions of reaction temperature between ambient temperature and the reflux temperature of the mixture at atmospheric pressure, preferably between 80° C. and 100° C., with a weight ratio of the at least one solid lignocellulosic raw material/liquid mixture comprised between 1/1 and 1/15, and for a determined period of time of reaction; and b) separating, at atmospheric pressure and at the reaction temperature, a solid fraction, constituting raw paper pulp, from an organic phase containing in solution at least the starting formic acid and water mixture, solubilized monomeric and polymeric sugars, lignins.

Claims

1. A low energy production process for producing paper pulp from lignocellulosic biomass, said process comprising the following successive steps: a) extracting lignins and hemicellulose from lignocellulosic biomass by putting at least one solid lignocellulosic raw material in a presence of a mixture, composed only of water and of formic acid, at atmospheric pressure and under controlled conditions of reaction temperature between ambient temperature and a reflux temperature of the mixture at atmospheric pressure with a weight ratio of said at least one solid lignocellulosic raw material/liquid mixture comprised between 1/1 and 1/15, and for a determined period of time of reaction depending on a Kappa number of the raw paper pulp; b) separating, at atmospheric pressure and at said reaction temperature, a solid fraction, constituting raw paper pulp, from an organic phase containing in solution at least the starting formic acid and water mixture, solubilized monomeric and polymeric sugars, lignins; and, washing said raw paper pulp successively in two steps with: c1) a solution composed of water and of formic acid with a concentration of formic acid in said solution between 80% and 100%, at ambient temperature; and c2) with hot water between 40° C. and 60° C., and wherein a centrifugation step at ambient temperature is performed between said first washing step c1) with a solution composed of water and of formic acid, and said second washing step c2) with hot water.

2. The low energy paper pulp production process according to claim 1, wherein a concentration of formic acid in said mixture is between 50% and 100.

3. The low energy paper pulp production process according to claim 2, wherein the concentration of formic acid in said mixture is between 80% and 90%.

4. The low energy paper pulp production process according to claim 1, wherein the weight ratio of said at least one solid lignocellulosic raw material/liquid mixture is comprised between 1/4 and 1/6.

5. The low energy paper pulp production process according to claim 1, wherein said organic phase contains in solution at least the starting formic acid and water mixture, solubilized monomeric and polymeric sugars, lignins, and acetic acid derived from the lignocellulosic biomass.

6. The low energy paper pulp production process according to claim 1, wherein said b) separation step is a centrifugation step or a filtration step, at atmospheric pressure and at said reaction temperature.

7. The low energy paper pulp production process according to claim 1, wherein said determined period of time of reaction is stopped when the Kappa number of the raw paper pulp reaches a stabilized value depending on a nature of the at least one lignocellulosic raw material.

8. The low energy paper pulp production process according to claim 7, which comprises a step consisting in regularly determining the Kappa number of the raw paper pulp during said determined period of time of reaction for identifying the stabilization of the Kappa number of the raw paper pulp.

9. The low energy paper pulp production process according to claim 8, wherein the step for regularly determining the Kappa number of the raw paper pulp consists in determining the Kappa number every ten minutes.

10. The low energy paper pulp production process according to claim 7, wherein said determined period of time of reaction is stopped when the Kappa number of the raw paper pulp is stabilized after at least three consecutive determination of the Kappa number of the raw paper pulp.

11. The low energy paper pulp production process according to claim 1, wherein said reflux temperature is in a range of to 80° C. to 100° C.

12. The low energy paper pulp production process according to claim 11, wherein said reaction temperature is equal to 85° C.

13. A low energy production process for producing paper pulp from lignocellulosic biomass, said process comprising the following successive steps: a) extracting lignins and hemicellulose from lignocellulosic biomass by putting at least one solid lignocellulosic raw material in a presence of a mixture, composed only of water and of formic acid, at atmospheric pressure and under controlled conditions of reaction temperature between ambient temperature and a reflux temperature of the mixture at atmospheric pressure with a weight ratio of said at least one solid lignocellulosic raw material/liquid mixture comprised between 1/1 and 1/15, and for a determined period of time of reaction depending on a Kappa number of the raw paper pulp; b) separating, at atmospheric pressure and at said reaction temperature, a solid fraction, constituting raw paper pulp, from an organic phase containing in solution at least the starting formic acid and water mixture, solubilized monomeric and polymeric sugars, lignins; and, washing said raw paper pulp successively in two steps with: c1) a solution composed of water and of formic acid with a concentration of formic acid in said solution between 80% and 100%, at ambient temperature; and c2) with hot water between 40° C. and 60° C., and wherein a centrifugation step is performed after said second washing step c2) with hot water.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) All biomass contains cellulose, hemicellulose and lignin in varying percentages, along with inorganic components which are the source of ash. Cellulose is a straight-chain polymer comprising anhydroglucopyranose joined with ether bonds. Hemicellulose is an amorphous polysaccharide containing sugar units which are branched and have varied sugar types. Lignin is the most complex constituent and is a polymer structure of phenylpropane units.

(2) The most prominent constituent of biomass is lignocellulose, which consists of the non-starch, fibrous part of plant material. Cellulose or paper pulp, hemicellulose and lignin are the three main elements of lignocellulosic biomass.

First Example

(3) An example of extraction according to the invention of raw paper pulp from a biomass Lignocellulosic Raw Material (LRM) using a mixture of water and formic acid (HCOOH) at low temperature and at atmospheric pressure is as follows.

(4) The first step consisted in preparing a mixture or solution of formic acid in water using a ratio in weight of 85% of formic acid and 15% of water, i.e., a concentration of formic acid equal to 85%.

(5) In a second step, 30 grams of a dried sample of lignocellulosic feedstock (LRM) and 270 grams of the liquid mixture of formic acid in water have been introduced in a 500 milliliters glass reactor.

(6) The solid/liquid ratio (i.e., Lignocellulosic feedstock/Mixture of acid and water) mass ratio (ratio in weight) was, for example, equal to 1/9.

(7) In order to increase the contact surface between liquid and solid, the lignocellulosic raw material sample can be crushed.

(8) At the ambient atmospheric pressure and using an oil bath, the mixture of the acid/water solution and of the biomass lignocellulosic raw material sample is heated at a temperature between 80° C. and 90° C.

(9) This mixture is thus stirred using a mechanical stirrer with an Inox anchor to have a homogenous temperature.

(10) Using a thermometer, the temperature has been stabilized at 85° C.

(11) At this stabilized temperature, the reaction started and has been maintained for 4 hours.

(12) Because working at a low temperature under 100° C., this extraction step is a very low energy consuming step.

(13) At the end of this period of time of reaction, the content of the reactor has been cooled to the ambient temperature and it contains a solid fraction and a liquid fraction.

(14) The content of the reactor has then been filtered to separate the raw solid cellulose or raw paper pulp from the liquid phase or fraction (First organic liquor).

(15) The separated cellulose has been washed with formic acid and then pressed and filtered to remove—in a liquid form—another portion of the of the liquid phase or fraction (Second organic liquor).

(16) First and second organic liquors have then been mixed together to obtain a main organic liquor.

(17) This primary liquid fraction has further been concentrated under vacuum, preferably with a heating thereof between 40° C. and 50° C., at a pressure of 100 milliBar.

(18) This concentration phase has been maintained until the moment where the dry matter content was about 50% to 60% in weight.

(19) At this stage, all parts of the formic acid contained in the first organic liquor are recovered and separated to obtain an intermediate liquid fraction.

(20) It appears that some other organics acids, such as acetic acid (CH3CO2H), could be generated or produced in very small amounts during the extraction step starting with a mixture of formic acid and water.

(21) In order separate or “extract” the lignins from the hemicellulose fraction in the intermediate liquid fraction, warm water has been added to the intermediate liquid fraction for reaching a liquid/solid mass ratio, for example equal to 4/1.

(22) With a view to enhancing the separation of the lignins from the hemicellulose fraction, for example only, a high performance rotor/stator disperser has been used during a period of dispersion comprised between 2 and 3 minutes at a rotational speed greater than 15000 revolutions/minute.

(23) At the end of this dispersion step, it has been processed with a filtration step or a centrifugation step to separate the lignins from the hemicellulose fraction and to obtain a residual liquid fraction.

(24) The separated lignins have then been washed with warm water until a neutral pH of the filtrate has been reached.

(25) The lignins have then been crushed and dried until reaching 94% of dry matter in weight, the drying temperature being not greater than 40° C.

Second Example

(26) A second example of extraction according to the invention of raw paper pulp from a biomass Lignocellulosic Raw Material (LRM) using a mixture of water and formic acid (HCOOH) at low temperature and at atmospheric pressure is as follows.

(27) The first step consisted in preparing a mixture or solution of formic acid in water using a ratio in weight of 85% of formic acid and 15% of water, i.e., a concentration of formic acid equal to 85%.

(28) In a second step, an amount of a dried sample of lignocellulosic feedstock (LRM) and an amount of the liquid mixture of formic acid in water have been introduced in a glass reactor.

(29) The solid/liquid ratio (i.e., Lignocellulosic feedstock/Mixture of acid and water) mass ratio (ratio in weight) was, for example, from ¼ to ⅙, in order to have a minimum of contact between the acid mixture and the biomass sample.

(30) In order to increase the contact surface between liquid and solid, the lignocellulosic raw material sample can be crushed.

(31) At the ambient atmospheric pressure and using an oil bath, the mixture of the acid/water solution and of the biomass lignocellulosic raw material sample is heated at a temperature between 80° C. and 90° C.

(32) This mixture is thus stirred using a mechanical stirrer with an Inox anchor to have a homogenous temperature.

(33) Using a thermometer, the temperature has been stabilized at 85° C.

(34) At this stabilized temperature, the reaction started and has been maintained from 2 to 4 hours.

(35) A Kappa index analysis of a sample of raw cellulose (Raw paper pulp) is conducted on a regular basis, for example using the TAPPI standard method T236 om-99.

(36) For example, the Kappa index analysis is conducted at least every 30 minutes after the two first hours of reaction.

(37) The Kappa index analysis might be conducted every 10 minutes after the two first hours of reaction.

(38) When the Kappa index reaches a constant value, i.e., when its value is stabilized, the reaction (i.e., the so-called cooking period of time) is stopped.

(39) At this stage, the content is processed for separating the raw cellulose (Solid phase or solid fraction) from the so-called first organic liquor (Liquid phase or liquid fraction).

(40) This separation is obtained by filtration or centrifugation.

(41) Thereafter, the separated raw cellulose is washed with a solution composed of water and of formic acid at a concentration of formic acid between 85% and 99%.

(42) Thereafter, the washed cellulose is processed for removing the residual second organic liquor, by pressing and filtering, or preferably by centrifugation.

(43) Additionally, the obtained cellulose can be washed in an additional step using only water at a temperature from 40° C. to 60° C.

(44) After this “hot” water additional washing step, the cellulose or paper pulp can be again centrifuged.

(45) After washing, the pH of the paper pulp is close to neutral.

(46) The first and second organic liquors previously obtained are mixed together in a single main organic liquor.

(47) This main organic liquor is then concentrated under vacuum. The media has been heated at a temperature less than 50° C. at a 100 mBar pressure. The concentration step is maintained until obtaining organic syrup, the dry matter content of the syrup being about 50% to 60% in weight.

(48) In order to separate or “extract” the lignins from the hemicellulose fraction in the intermediate liquid fraction, warm water has been added to the intermediate liquid fraction for reaching a liquid/solid mass ratio, for example equal to at least about 2/1.

(49) With a view to enhancing the separation of the lignins from the hemicellulose fraction, for example only, a high performance rotor/stator disperser has been used during a period of dispersion comprised between 2 and 3 minutes at a rotational speed greater than 15000 rounds/minute.

(50) At the end of this dispersion step, it has been processed with a filtration step to separate the lignins from the hemicellulose fraction and to obtain a residual liquid fraction.

(51) The separated lignins have then been washed with warm water until a neutral pH of the filtrate has been reached.

(52) The lignins have then been crushed and dried until reaching at least 90% of dry matter in weight (Preferably 95%), the drying temperature being not greater than 40° C.

(53) The re-condensed formic acid/water previously obtained can be reused, after a rectification step to reach the preferred 85% concentration, for another extraction of biomass or for washing the raw cellulose or raw paper pulp.

(54) According to this second example, depending on the nature of the raw feedstock values, corresponding values have been obtained as follows.

(55) TABLE-US-00001 Weight of dried product (Dry matter content of the product) Rice straw Birch wood Feedstock (g) 44.7 (88%) 57.8 (95%) Lignin extracted (g) 7.5 (96%) 10.9 (97%) Hemicelluloses extracted (g) 12.7 (62%) 15.7 (62%) Mass yield of extracted product 45% 46% Kappa index of cellulose (Tappi 20-22 28-30 T236) Residual index of cellulose (Tappi 4%-5% 5%-6% T236)

(56) Because working at a low temperature under 100° C., this extraction step is a very low energy consuming step.

(57) For example, an industrial plant using the process according to the invention, for one Ton (1T) of dry pulp, has an average energy consumption around 2 MWh (+/−20%), to be compared with the average energy consumption equal to 5 to 6 MWh for a non-integrated plant using the Kraft process.

(58) The process according to the invention can be industrially implemented using a batch technique for the extraction step, also including stirring of the content of each batch.

(59) This is advantageous when compared with diffusion techniques that imply long and energy consuming extraction periods.

(60) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.